[Index]
Monthly Global Tropical Cyclone Summary July 2004
[Summaries and Track Data] [Prepared by Gary Padgett]
| Tropical
Cyclones
[Index] |
Monthly Global Tropical Cyclone Summary July 2004 [Summaries and Track Data] [Prepared by Gary Padgett] |
MONTHLY GLOBAL TROPICAL CYCLONE SUMMARY
JULY, 2004
(For general comments about the nature of these summaries, as well as
information on how to download the tabular cyclone track files, see
the Author's Note at the end of this summary.)
*************************************************************************
JULY HIGHLIGHTS
--> Northwest Pacific rather quiet while Northeast Pacific heats up
*************************************************************************
***** Feature of the Month for July *****
MONSOON DEPRESSIONS AND STRONG TROPICAL WAVES
During the summer (boreal) of 2003, I sent another one of my famous
surveys to the members of an informal tropical cyclone discussion group
of which I am a member. I also recently sent it to a few other persons
in the tropical cyclone community. I intend to present the results of
the survey as monthly features spread over several months, beginning with
the May, 2004, summary. The survey consisted of ten multiple-choice
questions dealing with various tropical or subtropical cyclone-related
issues, and two or three questions will be considered each month.
The persons responding to the survey are listed below. A special
thanks to each for taking the time to respond to the questions.
Michael Bath - New South Wales, Australia
Bruno Benjamin - Guadeloupe, French West Indies
Eric Blake - TPC/NHC, Miami, Florida, USA
Pete Bowyer - Canadian Hurricane Centre, Halifax, Nova Scotia, Canada
Kevin Boyle - Newchapel Observatory, Stoke-on-Trent, UK
Jeff Callaghan - BoM, Brisbane, Queensland, Australia
Simon Clarke - Brisbane, Queensland, Australia
Tony Cristaldi - NWS Office, Melbourne, Florida, USA
Roger Edson - University of Guam, USA
Chris Fogarty - Canadian Hurricane Centre, Halifax, Nova Scotia, Canada
James Franklin - TPC/NHC, Miami, Florida, USA
Bruce Harper - Brisbane, Queensland, Australia
Julian Heming - UK Meteorological Office, UK
Karl Hoarau - Cergy-Pontoise University, Paris, France
Greg Holland - BoM, Australia
Mark Kersemakers - BoM, Darwin, Northern Territory, Australia
Mark Lander - University of Guam, USA
Chris Landsea - AOML/HRD, Miami, Florida, USA
Gary Padgett - Alabama, USA
Michael V. Padua - Naga City, Philippines
Michael Pitt - US Navy
David Roberts - TPC/NHC, Miami, Florida, USA
David Roth - NOAA/HPC, Maryland, USA
Matthew Saxby - Queanbeyan, New South Wales, Australia
Carl Smith - Queensland, Australia
Phil Smith - Hong Kong, China
John Wallace - San Antonio, Texas, USA
Ray Zehr - Colorado State University, Ft. Collins, Colorado, USA
For each of the survey questions, the format will be as follows:
(1) the question as it appeared in the original survey
(2) summary of the responses to each of the possible choices
(3) some of the comments from various respondents
Following this I will attempt to present an analysis of the issues
plus interject my opinions on the subject.
The monthly feature for July will focus on two types of deep tropical
systems, very different from each other, but yet the precursors of the
majority of the world's tropical cyclones: the monsoon depression and
the tropical wave (also known as easterly waves). Easterly waves are
the primary precursor of Atlantic tropical cyclones which form in the
deep tropics while monsoon depressions are the parent disturbances for
most of the tropical cyclones of the North Indian Ocean, the Northwestern
and South Pacific, and the Australian Region. The survey questions dealt
specifically with the operational warning problems caused by both monsoon
depressions and tropical waves when sustained gale-force winds develop
before the appearance of "classic" tropical cyclone characteristics.
There were 28 persons who responded to the survey questions. For
some questions, certain persons did not specify an answer, so the total
number of votes might not always add up to 28. Also, in some cases the
respondent was undecided between two of the choices. In those cases I
assigned 1/2 vote to each of the two choices. A word about the comments
included below: this article is extremely long as it is, and I could
not possibly include all the comments which the various respondents
made. I have selected certain ones which seem to cover the various
issues well, as well as a few which cast a different slant on the
question.
Question #6 - Monsoon Depressions
---------------------------------
(1) The question was: Monsoon depressions are large, sloppily-formed
cyclones which are prevalent in the western Pacific (both north and
south), Australian Region, and in the Indian Ocean. Sometimes these
systems produce winds exceeding gale force, or even storm force,
without having a tight circulation nor well-organized central
convection. In pre-Dvorak analysis days, no doubt many of these
were classified as tropical cyclones. Do you think the best
operational warning strategy for monsoon depressions acquiring
gale-force winds is:
(A) Name as tropical storms
(B) Introduce monsoon depression terminology in warnings and
emphasize presence of gales
(C) Issue gale warnings for certain areas without describing
the meteorological phenomenon
(D) Ignore and hope they'll go away or else transform into "classic"
tropical cyclones
(2) Summary of Responses
(A) Name as tropical storms: 9.0 votes - 33%
(B) Introduce new terminology: 14.5 votes - 54%
(C) Issue generic gale warnings: 3.5 votes - 13%
(D) Ignore: 0.0 votes - 0%
(3) Some Comments
Carl Smith (A & B): "They should be named if they are closed systems
and produce gale/storm-force winds, however, specific terminology
should be included in the warnings describing the situation and where
the gales/storm-force winds are expected."
Chris Fogarty (C): "Treat it like a large extratropical LOW--like in
the Atlantic without getting fancy."
Chris Landsea (A): "Handle similarly to what I suggested for sub-
tropicals. Name 'em as 'tropical cyclones' operationally, then in
the Best Track indicate the best 'true' identity."
Dave Roberts (B): "During my tenure at JTWC, I would name monsoon
depressions even though core winds were weak. Just was simpler to
do without confusing anyone. However, model assimilation was another
issue (TC size). Would like to see as separate terminology including
monsoon gyres."
David Roth (A): "Name as tropical storms since they have a very warm
core and usually transition into TCs. Frances of 1998 and Isidore of
2002 fit this definition fine, from what I understand, and completed
the transition."
Greg Holland (C): "Definitely NOT tropical cyclones...their winds
are well removed from what is generally a weakly-defined center (and
in the Australian Region often over land), and from memory, a lot,
if not most of them, are substantially cold-cored in the lower
troposphere...there is actually no need for any changes. My
impression is that the current system handles these perfectly
well by just putting out gale warnings."
James Franklin (B): "Issue gale warnings but discuss in context of
a monsoon cyclone."
Jeff Callaghan (A): "Justin in the Coral Sea in March, 1997, was for
much of its life more like a deep monsoon LOW but had a huge impact
at sea."
John Wallace (C): "There is no need to add more confusion to the TC
classification system by discerning between true TCs and MDs."
Julian Heming (B): "If we are going to have a separate terminology
for sub-tropical storms in the Atlantic, then there needs to be a
similar terminology for monsoon depressions, particularly if winds
exceed gale force."
Kevin Boyle (B): "Although winds of >35 kts could be classed as a
tropical storm, I suppose, to avoid confusion and to enhance aware-
ness of the system."
Mark Lander (B): I used to think that the most sensible thing to do
for monsoon depressions that had evolved to the point of possessing
gales was simply to name them as tropical storms. This is still my
preferred option, but since the warning agencies seem to have such
trouble with these things (center location, the warning format of
point-radius, broad light wind center, etc), I think an out is
needed. My 'out' would be to develop a point-band or point-ring
format for wind distribution. Then the systems can be numbered,
and the warning center does not have to over fret the non-standard
wind distribution. Also, by the time a MD has true gales in it,
it is usually well on its way to becoming a conventional TC anyway."
Matthew Saxby (A): "If it's a tropical system with a closed
circulation and gales in at least one quadrant, I think the thing
should be named and warned on in the normal TC way. Like I said
before, any victims aren't going to be impressed with fine legalistic
points."
Phil Smith (A): "My reason for choosing Option A is purely one of
making the general public aware that 'there are dangerous winds about
somewhere out there' and that they may need to make preparations
for bad weather conditions. As I understand it, this practice is
being taken up by BoM for monsoon LOWs threatening Australian areas
for this reason. A negative that could be raised against this prac-
tice is the likelihood that several circulation centres may develop
around the periphery and that these will sometimes 'take turns' at
being the dominant centre. This could lead to some exceedingly
erratic paths for some storms if the agency concerned tries to fix
the centre of the named storm at where the most action is occurring
from time to time."
Ray Zehr (B or C): "Some 'TC size according to RMW' criteria is
needed as a guideline for naming. Since multiple TCs can be
associated with a single monsoon depression (or gyre), you can't
be naming monsoon depressions. Of course, a monsoon depression
can have a TC at its center, i.e., evolve into a TC."
Question #7 - Tropical Waves
----------------------------
(1) The question was: Primarily in the Atlantic tradewind belt--perhaps
rarely in other basins--well-organized tropical disturbances (i.e.,
tropical waves) moving rapidly along can produce gale and/or storm-
force winds without a closed circulation at the surface. They
usually have a mid-level circulation and would no doubt have westerly
winds at the surface on the equatorward side if they were not moving
so rapidly (sometimes 25-30 kts). These often present a much more
serious threat to marine interests and the Lesser Antilles than some
"normal" tropical depressions or even weak tropical storms. What is
the best operational warning strategy for these?
(A) Name as tropical storms
(B) Mention that gales are present in Tropical Weather Outlooks or
Special Tropical Disturbance Statements
(C) Introduce new terminology or issue special advisories for these
gale-bearing waves and emphasize warnings for strong winds
(2) Summary of Responses
(A) Name as tropical storms: 5.5 votes - 20%
(B) Mention in TWOs or STDSs: 13.5 votes - 48%
(C) New terminology: 9.0 votes - 32%
(3) Some Comments
Chris Landsea (A or B): "Definitely not Option C, but I'm on the
fence about this one. I could see either 'A' or 'B', as long as
the best track indicated that they were troughs rather than a
tropical cyclone (or even don't include them in the Best Track)."
Dave Roberts (C): "Wondering what the statistics are of these waves
eventually developing into TCs? Either way, a forecast track with
intensity and wind radii could easily be developed during its life
cycle."
David Roth (B): "Mention that gales are present in Tropical Weather
Outlooks or Special Tropical Disturbance Statements AND High Seas
Forecasts. There MUST be gale warnings in the High Seas Forecasts
for these systems, no ifs, ands, or buts. If not, then 'someone'
has dropped the ball."
Eric Blake (A or B): "Name usually if near land, otherwise
Option B."
Greg Holland (B): "Same comment for monsoon depressions, if they
are loosely defined at the center. However, if they have tropical
cyclone characteristics, then definition should be in Lagrangian
terms (note that the cloud imagery and our interpretation thereof
is Lagrangian). I do note that NHC requires a westerly wind at the
surface to call these systems, so why change a system that ain't
broke."
James Franklin (B): "Issue gale warnings, and mention such in TWOs
and STDSs. This is what we do now. I am very much opposed to
calling a trough a tropical cyclone. Look, not all hazardous weather
occurs in tropical cyclones. For the life of me, I cannot understand
this desire to call anything hazardous in the tropics a tropical
cyclone."
Julian Heming (B): "I think we need to adhere to classical
definitions of tropical cyclones (closed circulation), but also
develop ways of warning on the hazards of such systems."
Mark Lander (A): "Some of the TCs of 2003 (Claudette) showed that
these systems can possess gales, and an impressive cloud system, and
actually not have a distinct well-defined surface vortex. I think
that if a persistent, well-organized cloud system (with some of the
properties of a TC, such as an anticyclonic pattern to cirrus out-
flow) should be named. This especially if there is a light wind
region to the south of the gales (where only a small change in
intensity or forward speed would result in the immediate formation
of a surface vortex). I would bet that the statistics would show
that persistent well-defined tropical disturbances that acquire
gales become TCs most of the time, so there is an urgency to get out
a tropical advisory at the earliest possible time."
Phil Smith (C): "Could they be 'named tropical waves' drawing from
the same pool of names as are used for regular TCs? They certainly
present as much danger to shipping and island communities as named
storms do, and may often have very high winds on the one side.
Names are useful for alerting the general public and since these
waves can easily become true TCs when they slow down a bit, I believe
it would be a useful practice to help people know that the same
disturbance being referred to as 'Tropical Wave Adam' has become
'Tropical Storm Adam'. And if 'Tropical Wave Adam' simply fizzles
out without ever becoming 'Tropical Storm Adam', then no harm has
been done and people have been warned of winds which are dangerous
to their ships, homes, businesses or other interests."
Ray Zehr (A): "I've never liked the criteria of 'closed circulation'
for weak TCs. The criteria should be 'closed circulation in center
relative coordinates'. I see nothing wrong with explaining to the
public that a fast-moving vortex has strong winds on one side from
the direction of motion, and that's it. I think in the Atlantic
this occurs often with TDs and extratropical transitions, but
rarely with TSs, however, it's apparently somewhat common off the
west coast of Australia."
Roger Edson (B): "However!!! The scatterometer and microwave
imagery era has shown that it is wrong to assume that all do not
have westerly winds to the south and a closed circulation. Those
'old' assumptions were based on lack of data and a bad use of
terminology."
Simon Clarke (C): "Call them 'Gale Force Tropical Waves'."
Tony Cristaldi (C): "Mention that the only reason that the system
does not have the westerly ground-relative winds needed to be
designated as a TC is because of its fast forward speed."
Analysis and Gary's Opinion
---------------------------
First of all I'll say that Option D to Question #6 (ignore monsoon
depressions and hope they'll go away) perhaps sounds facetious, but it
was not meant as a joke. I've sometimes gotten the impression that
they've often been handled that way in the past, particularly by JTWC,
which has no provision in their operational plan (along with NHC) for
a tropical depression which might have gale-force winds. That's not
a problem for Australia and Fiji whose current definition of a tropical
depression (tropical LOW in Australia) allows for gale-force winds if
they are not occurring near the system's center.
In the survey I voted for Option A (name as tropical storms), but I'll
restrict that to include only systems for which the gales have begun to
curve cyclonically around the circulation, even if at some distance from
the center, and occupying from 1/3 to 1/2 or more of the circulation.
Most systems at this stage are likely to continue evolving into a
"classic" tropical cyclone anyway. I would not name systems with mainly
a linear band of gales well-removed from the center and which often could
exist without the presence of the LOW center. From my experience in
following such depressions in the Australian Region and South Pacific,
I have noted that sometimes the gales may be on the equatorward side due
to a monsoonal westerly-wind burst; at other times on the poleward side
due to a tight gradient with a subtropical HIGH.
Following is a quote from an e-mail I received from Cliff Revell,
who was (I think) formerly a member of New Zealand's Meteorological
Service. This comes from a letter Cliff had sent to Steve Ready
a few years earlier concerning the former WMO Region V requirement
that a tropical depression must have gales surrounding the center
in order to be classified as a tropical cyclone: "A suggestion. In
order to maintain consistency with other regions, with past statistics,
and to exclude those cases when gales occur at a distance from the
centre in a more or less linear band caused by a strong anticyclone to
the south, adopt the requirement that the envelope of gale-force or
stronger winds be curved in a cyclonic sense."
I must add, though, that Greg Holland and Ray Zehr have raised two
concerns which should be considered. As Greg points out, gale-producing
monsoon depressions can form over land in the northern portions of the
Australian continent. As every tropical meteorological text written
since the time of King Tut points out--tropical cyclones are absolutely
a type of marine cyclone and always weaken when they move over land.
Personally, I think it quite likely that most of these inland monsoon
depressions have the band of gales to the north due to strong monsoonal
westerlies and don't fit the cyclonic curvature criteria suggested by
Cliff Revell.
Ray Zehr (also Phil Smith) brought up the issue of multiple circu-
lation centers. Most of my knowledge of monsoon depressions and gyres
has come from Mark Lander, and from what Mark has related, monsoon gyres
typically spawn multiple tropical cyclones, but the entire gyre itself
only very rarely consolidates into a tropical cyclone (Typhoon Gladys of
1991 being an example). The smaller monsoon depression does often sport
several convective clusters, some of which may exhibit rotation, but
usually by the time an extensive area of gales has begun to curve around
the larger center, that center has become dominant and the depression
goes on to become a conventional tropical cyclone.
With regard to rapidly translating tropical waves, it is interesting
to note that while most persons in the tropical cyclone community tend
to regard a westerly surface wind on the equatorward side an absolute
requirement for the existence of a tropical cyclone, there are some
prominent voices (again Ray and Greg) who would define a tropical cyclone
in terms of center-relative coordinates. I voted for Option A (to
name) on the survey, but this was somewhat of a turnaround from the way
I'd previously thought on the issue. A couple of systems which helped to
alter my way of thinking were Chantal (2001) and Claudette (2003).
Chantal at one point was all but an open wave with 60-kt winds racing
across the Caribbean. And Claudette was a very well-developed system
with a very definite tropical storm appearance in satellite imagery with
established anticyclonic outflow and 45-kt winds north of the "center",
but (it was thought) without any westerly winds to the south. On 8 July
a reconnaissance aircraft searched in vain for several hours for westerly
winds and was about to depart the area when it very fortuitously
discovered a 20-kt southwesterly wind and a very tiny vortex. So we then
had an "instant" tropical storm. (I would add that I'm not in favor of
naming strong tropical waves which exhibit very little if any vorticity
and/or outflow, and which have substantial easterly winds on the equator-
ward side. Such systems are not likely to develop quickly into tropical
storms.)
Somehow it seems a little inconsistent to issue a full advisory
package (public advisory, forecast/advisory, discussion bulletin and
strike probabilities) for a 25-kt tropical depression which may not
be forecast to reach tropical storm intensity for 24-48 hours, but to
simply relegate information on a gale or storm-force tropical wave to
the TWOs and gale warnings buried down in the High Seas Forecasts. If
they're not going to be named, then STDSs should be issued at least every
six hours. Also, Roger Edson brings up a good point that even if a
reconnaissance crew fails to find westerly winds, how do we know for sure
they're not there?
I can't speak for the general public in the Lesser Antilles or other
Caribbean nations where these systems usually present a threat, but it
is an unarguable point that among the U. S. general public, when a system
is named, the interest jumps by an order of magnitude. And not just
among the general public. Following is an excerpt from the report on
Hurricane Claudette in the July, 2003, summary:
The following quote from an e-mail written by Kenneth J. Schaudt
of Marathon Oil Company illustrates how the attention of the public
and other concerned parties spikes up when a tropical storm is named:
"Much of the United States' natural gas is produced in the Gulf of
Mexico. Since the threat of tropical storms may shut down production
briefly, the market for natural gas responds to the perceived threats.
On the 8th (of July) at 1806 UTC, the Special Tropical Disturbance
Statement declaring Tropical Storm Claudette hit the wire. Within
three minutes, the price of natural gas had jumped 10 cents."
(Regarding the attention-grabbing power of a name, I know from several
of my Australian correspondents that the same is true Down Under.)
Regarding consistency with past practices, I think it is very likely
that prior to the satellite era and the development of the Dvorak method
of intensity analysis, and consequently a major emphasis being placed
on organized central convection, many stronger monsoon depressions were
classified as tropical storms in the areas of the world where they are
prevalent, just as in the Atlantic in earlier years no doubt many of the
"tropical" cyclones in the Best Track file were in reality subtropical
systems. And I also think it highly probable that many of the short-
lived Atlantic systems whose tracks are shown beginning just east of the
Lesser Antilles and then disappearing in the central Caribbean were
likely open tropical waves with gale-force or higher winds. Most of
these were included in the Best Track file based on island reports of
tropical storm winds, the assumption being that if sustained gale-force
winds were present, then more than likely there was a surface
circulation.
So, to recap, I personally am in favor of "bending the rules" a little
to name and treat as tropical storms systems which at a certain point in
time may not have attained quite all the characteristics of "classic"
tropical cyclones, but which can pose a significant threat to life and
property and which likely will eventually evolve into "classic" tropical
storms. There is nothing anomalous here--many systems have been named
which were in truth much closer in nature to a subtropical storm than to
a true tropical cyclone. It seems that this is the best way to help
reduce confusion and achieve the ultimate goal of minimizing loss of life
and mitigating damage. As Mark Lander has expounded many times, having
the initial tropical cyclone advisory refer to a system near or exceeding
hurricane intensity is not in the best interest of achieving this goal.
*************************************************************************
ACTIVITY BY BASINS
ATLANTIC (ATL) - North Atlantic Ocean, Caribbean Sea, Gulf of Mexico
Activity for July: 1 tropical depression
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida:
discussions, public advisories, forecast/advisories, tropical weather
outlooks, special tropical disturbance statements, etc. Some
additional information may have been gleaned from the monthly
summaries prepared by the hurricane specialists and available on
TPC/NHC's website. All references to sustained winds imply a
1-minute averaging period unless otherwise noted.
Atlantic Tropical Activity for July
-----------------------------------
No tropical storms or hurricanes formed in the Atlantic basin during
the month of July. This isn't anything out of the ordinary, as the
annual average of named storms is about 4 every 5 years, with a hurricane
developing about every third year. Over the past 25 years, July has been
stormless in 13 years, or about half the time. The only intense July
hurricane (Category 3 or higher on the Saffir/Simpson scale) since 1950
was Hurricane Bertha in 1996. Neither did any tropical depressions form
during July until the final day of the month, when Tropical Depression 01
developed during the afternoon off the Georgia coast, becoming Tropical
Storm Alex the next day. On 3 August Alex intensified into a Category 2
hurricane and passed very close to Cape Hatteras as it began to move
northeastward away from the U. S. mainland. After weakening slightly on
the 4th, Alex re-intensified on the 5th into a Category 3 hurricane as it
scooted northeastward over the warm Gulf Stream waters south of the
Canadian Maritimes. The report on Hurricane Alex will be included in the
August summary.
There were, however, a couple of weaker tropical disturbances worthy
of mention. A small area of disturbed weather developed on the morning
of 8 July about 240 nm southwest of Bermuda. During the afternoon a
small surface LOW center formed and moved east-northeastward, passing
very near Bermuda early on the 9th. According to Jack Beven, there was
just enough of a wind and pressure perturbation at Bermuda to show that
the circulation did exist at the surface. The lowest SLP recorded on
the island was only 1019 mb. Convection associated with the LOW remained
poorly-organized and the system soon encountered cooler SSTs after
passing Bermuda.
Disturbed weather developed off the east coast of Florida and extended
northeastward from the Bahamas for several hundred miles late in the
third week of July. This was associated with an upper-level LOW and a
broad surface trough. A weak LOW formed on the 24th about 285 nm south-
east of Cape Hatteras. By the morning of the 25th the LOW was centered
about 150 nm east-southeast of Cape Hatteras, moving north-northwestward
at about 12 kts with limited thunderstorm activity. During the early
morning hours of 26 July convection increased significantly, the LOW then
being located around 200 nm south of Long Island. Maximum winds were
estimated to be 20-25 kts northeast of the center, and there was a
possibility that if thunderstorm activity continued to increase near the
center, a tropical or subtropical depression might develop. However,
by midday the LOW was beginning to merge with a frontal zone, so tropical
cyclone formation was no longer considered likely.
*************************************************************************
NORTHEAST PACIFIC (NEP) - North Pacific Ocean East of Longitude 180
Activity for July: 3 tropical depressions
1 tropical storm
1 hurricane
1 intense hurricane
Sources of Information
----------------------
Most of the information presented below was obtained from the
various tropical cyclone products issued by the Tropical Prediction
Center/National Hurricane Center (TPC/NHC) in Miami, Florida (or the
Central Pacific Hurricane Center (CPHC) in Honolulu, Hawaii, for
locations west of longitude 140W): discussions, public advisories,
forecast/advisories, tropical weather outlooks, special tropical
disturbance statements, etc. Some additional information may have
been gleaned from the monthly summaries prepared by the hurricane
specialists and available on TPC/NHC's website. All references to
sustained winds imply a 1-minute averaging period unless otherwise
noted.
Northeast Pacific Tropical Activity for July
--------------------------------------------
Over the period 1971-2003, the Northeast Pacific basin's statistics
for July are: 3.7 named storms, 2.0 hurricanes, and 1.1 intense hurri-
cane. July of 2004 was pretty close to average with 3 named storms,
2 hurricanes, and 1 intense hurricane. Darby became the first Eastern
Pacific intense hurricane since Kenna in October, 2002. All three of
the storms formed well off the Mexican coast and moved generally west-
northwestward with minimal effects on the coastline. Reports follow
on these three storms--a special thanks to John Wallace for writing the
summaries for Blas and Celia.
In addition to the three named storms, there were also three tropical
depressions for which advisories were issued. The first of these formed
very early in the month well to the southwest of Cabo San Lucas on the
southern tip of the Baja California Peninsula. Tropical Depression 02E
formed around 1200 UTC on 2 July about 650 nm southwest of Cabo San
Lucas and moved west-northwestward, dissipating by 03/1800 UTC about
850 nm west-southwest of the Cabo. Maximum winds were estimated at
25 kts. Also during the first week of July, Tropical Depression 01C
formed in the Central North Pacific about 625 nm southeast of Johnston
Island. The first advisory was issued by CPHC at 0300 UTC on 5 July,
and the final one issued at 0300 UTC the next day when it became apparent
the system was dissipating. Maximum winds in this depression were also
estimated at only 25 kts.
Finally, advisories were initiated on Tropical Depression 06E at 0900
UTC on 29 July with the center located about 415 nm south-southwest of
Cabo San Lucas. However, the final advisory was issued only 18 hours
later, locating the dissipating center about 215 nm west-southwest of its
point of origin. In the case of TD-06E, the remnant LOW held together
as it drifted west-southwestward across the expanse of the Eastern North
Pacific. By late on 1 August convection had become re-established near
the center of the LOW so advisories were begun again on the system at
02/0300 UTC. The center was placed roughly 1200 nm west-southwest of
the southern tip of Baja California, and winds were estimated at 30 kts.
The depression was located over warm SSTs and in a region of low shear,
and intensification to near hurricane strength was initially forecast,
but the system failed to respond to its apparently favorable environ-
ment. Visible imagery on the 3rd and a 03/1440 UTC QuikScat overpass
indicated that the depression no longer had a well-defined closed surface
circulation and had degenerated into an elongated trough with embedded
swirls and only a narrow band of weak convection. The final advisory
at 03/2100 UTC placed the dissipating center about 1500 nm west-southwest
of Cabo San Lucas.
TROPICAL STORM BLAS
(TC-03E)
12 - 15 July
---------------------------------------
A. Storm Origins
----------------
Tropical Storm Blas formed from a tropical wave which had crossed
Central America into the Eastern Pacific on 8 July. On 12 July an
area of persistent disorganized convection that had been flaring up in
the Eastern Pacific for several days had finally consolidated by midday,
warranting its upgrade to Tropical Depression Three-E at 1500 UTC on
12 July when located approximately 300 nm south-southwest of Manzanillo,
Mexico. The depression tracked steadily northwestward, under the
influence of a ridge stationed over the United States Southwest.
B. Synoptic History
-------------------
The depression officially strengthened to Tropical Storm Blas at
0300 UTC on 13 July when centered about 265 nm southwest of Manzanillo.
The nascent Blas had the distinction of being a very large storm, with
storm-force wind radii that maxed out at 200 nm in the western quadrant
on the 13th and into the 14th as it accelerated northwestward at the
surprising speed of 17-18 kts. Blas reached its peak 1-min avg MSW of
50 kts, with a CP of 994 mb, at 0900 UTC on 13 July, an estimate which
the NHC considered conservative.
Blas began weakening on the 14th as it tracked into unfavorably cool
waters. Its broad circulation remained robust--ship ELYS4 reported a
35-kt wind 100 nm from the center at 0600 UTC on the 14th, though the
peak MSW overall was only 40 kts. Blas had dropped below storm strength
by 2100 UTC that day and, as is typical of weakening NEP cyclones,
decelerated and turned to the west-northwest along with the low-level
trade winds. Its convection having completely collapsed, the last
advisory was issued on Tropical Depression Blas at 0300 UTC on 15 July,
the weakening center being located about 500 nm due west of Cabo San
Lucas on the southern tip of the Baja California Peninsula. Not
surprisingly, the large remnant vortex took some time to spin down, and
was dimly evident in visible imagery as late as the 19th.
C. Damage and Casualties
------------------------
Though squalls affected Baja California, no known casualties or damage
were caused by Tropical Storm Blas.
(Report written by John Wallace)
HURRICANE CELIA
(TC-04E)
19 - 25 July
-----------------------------------
A. Storm Origins
----------------
As Tropical Storm Blas weakened and dissipated to the northwest,
another tropical cyclone quickly formed in its wake. A vigorous
tropical wave moved off the western coast of Africa on 5 July and
tracked uneventfully across the Atlantic and Caribbean. The wave
ultimately reached the Eastern Pacific, spawning a compact LOW which
was evident as early as the 17th. As the system tracked roughly
westward it became better organized and was upgraded to Tropical
Depression Four-E at 0300 UTC on 19 July when centered approximately
550 nm south-southwest of Cabo San Lucas.
B. Synoptic History
-------------------
A ridge to the north steered TD-04E slowly to the west with slight
oscillations. Its potential intensity was uncertain, due to the
conflicting factors of nearby stable air but also low shear and warm
SSTs. Even so, the depression strengthened to Tropical Storm Celia at
2100 UTC on 19 July when located about 600 nm south-southwest of Cabo
San Lucas. Celia was as remarkably small as its predecessor Blas had
been large: the gale-radius was only 60 nm, a value which varied little
throughout the cyclone's lifetime--even at its peak--challenging "midget"
status.
Celia tracked uneventfully westward and steadily intensified, after
a slight weakening late on the 20th and into the 21st due to interference
from an upper-level LOW. However, it managed to avoid entraining nearby
stable air into its circulation. Satellite detection of a mostly-closed
eyewall warranted its upgrade to a hurricane at 0300 UTC on 22 July. The
storm at this time had moved to a position about 750 nm southwest of Cabo
San Lucas. Celia reached its peak MSW of 70 kts, with an estimated CP of
985 mb, six hours later at 22/0900 UTC.
Celia weakened rapidly after its peak, probably due to both cooler
water and entrained stable air, courtesy of an interfering upper-level
LOW. By 2100 UTC on the 22nd the convection had largely collapsed,
though the weakening trend stabilized near minimum tropical storm
strength. Periodic deep convection and a good LLCC allowed it to hold
on to storm status as it tracked westward. It seems that the entrainment
of dry air decreased, shear remained low, and SSTs temporarily became a
little warmer.
On the 24th, however, Celia weakened to a depression, and turned
toward the west-northwest with a slight increase in speed as it moved
with the low-level flow. Convection remained remarkably tenacious for
such a small cyclone, and the last warning was not issued until late on
25 July--at 2100 UTC--placing the weakening LLCC about 1375 nm west-
southwest of the tip of Baja California. The remnant vortex remained
evident in satellite imagery until late on the 27th, when it dissipated
several hundred miles southeast of Hawaii.
C. Damage and Casualties
------------------------
There were no known casualties or damage resulting from Celia.
(Report written by John Wallace)
HURRICANE DARBY
(TC-05E)
26 July - 1 August
--------------------------------------
A. Storm Origins
----------------
A tropical wave moved westward across the coast of Africa on 12 July
and continued across the Atlantic and Caribbean, reaching the Eastern
Pacific on 20 July. The system showed the first signs of organization
on the 24th well to the south-southwest of Manzanillo, Mexico. The
disturbance gradually became better organized and had developed into
Tropical Depression 05E by 1800 UTC on 26 July when it was centered
approximately 700 nm south-southwest of Cabo San Lucas on the southern
tip of the Baja California Peninsula. Six hours later Dvorak
classifications from SAB and TAFB had reached T2.5, so TD-05E was
upgraded to Tropical Storm Darby. The circulation was still in its
formative stages and had not completely separated from the ITCZ.
B. Synoptic History
-------------------
Tropical Storm Darby's convective structure became increasingly better
organized during the 27th and by 1800 UTC the estimated MSW had reached
60 kts--just shy of hurricane status. There were some indications that
a banding-type eye was trying to develop, but its appearance in satellite
imagery was rather transient for the next 12 hours. However, SSM/I
microwave data at 28/0336 and 28/0507 UTC clearly indicated that Darby
had developed a 20-25 nm diameter eye embedded in a round CDO, and auto-
mated ODT values were around 69 kts. Satellite CI estimates ranged from
55 to 77 kts, but taking all the evidence into consideration, Darby was
upgraded to the season's second hurricane at 28/0900 UTC when located
approximately 835 nm southwest of Cabo San Lucas. Darby at this time
was moving west-northwestward at 11 kts around a subtropical ridge.
Initially, the hurricane was forecast to peak at 80 kts and then begin
to weaken as it encountered cooler SSTs. However, at 2100 UTC the cloud
pattern had improved significantly and T-numbers had increased to 5.0,
so the MSW was increased to 90 kts.
A further surprise was in store. At 0600 UTC on 29 July Dvorak
T-numbers from both TAFB and SAB had reached 6.0, or 115 kts. Darby
had undergone rapid intensification over sub-27 C water with the MSW
increasing from 35 kts to 105 kts in 54 hours. The MSW was set at
105 kts instead of 115 kts due to the fact that Darby was over 26 C
water, and the forecaster felt that downward mixing of the strong winds
was likely not occurring due to the cooler and more stable boundary
layer. Nonetheless, Darby had become the first Category 3 or higher
hurricane in the Eastern North Pacific since the very intense and
destructive Hurricane Kenna in October, 2002.
Darby's tenure as a major hurricane, however, was not to be for long.
By 29/1500 UTC the eye was becoming less distinct and winds were dropped
to 100 kts, and six hours later the eye was no longer visible and the
MSW was further reduced to 90 kts. The demise of Hurricane Darby was
rather quick as it moved over cooler SSTs and into increasing vertical
shear. Only 24 hours after reaching its peak of 105 kts, Darby was only
a minimal hurricane, and six hours later was a 55-kt tropical storm.
Eastern North Pacific tropical cyclones have a higher "death rate" caused
by systems moving over cold SSTs without encountering a baroclinic zone
more so than in any other basin. Typically when systems moving north-
westward or west-northwestward lose most of their deep convection and
become shallow systems, they turn westward and move with the low-level
trade winds. Darby was no exception to this as it began to track west-
ward after crossing 130W.
By 2100 UTC on 30 July Darby had been reduced to a swirl of low and
mid-level clouds with isolated patches of deep convection to the north-
east of the center. Satellite intensity estimates ranged from 35 to
65 kts, and a high resolution QuikScat overpass at 1446 UTC showed a
50-kt vector north of the center, so the intensity was set at 50 kts.
However, the MSW was reduced to 40 kts six hours later, and at 1200 UTC
on the 31st Darby was downgraded to a tropical depression. Darby had
crossed 140W into the Central North Pacific by 0000 UTC on 1 August.
Although the depression was moving over warmer water, it was running into
strong southwesterly vertical shear. CPHC issued the final advisory on
Darby at 01/0600 UTC, placing the dissipating center about 750 nm east
of Hilo, Hawaii. The remnants of Darby continued westward, bringing
rainfall totals of up to 150 mm in some parts of Hawaii.
C. Damage and Casualties
------------------------
No reports of damage or casualties resulting from Hurricane Darby
have been received.
(Report written by Gary Padgett)
*************************************************************************
NORTHWEST PACIFIC (NWP) - North Pacific Ocean West of Longitude 180
Activity for July: 2 tropical storms **
1 typhoon
** - one of these classified as a tropical storm only by China (NMCC)
Sources of Information
----------------------
Most of the information presented below is based upon tropical
cyclone warnings and significant tropical weather outlooks issued
by the Joint Typhoon Warning Center of the U. S. Air Force and
Navy (JTWC), located at Pearl Harbor, Hawaii. In the companion
tropical cyclone tracks file, I normally annotate track coordinates
from some of the various Asian warning centers when their center
positions differ from JTWC's by usually 40-50 nm or more. All
references to sustained winds imply a 1-minute averaging period
unless otherwise noted.
Michael V. Padua of Naga City in the Philippines, owner of the
Typhoon 2000 website, normally sends me cyclone tracks based upon
warnings issued by the Japanese Meteorological Agency (JMA) and the
Philippines' Atmospheric, Geophysical & Astronomical Services
Administration (PAGASA). Also, Huang Chunliang of Fuzhou City, China,
sends data taken from synoptic observations around the Northwest
Pacific basin. A very special thanks to Michael and Chunliang for
the assistance they so reliably provide.
In the title line for each storm I have referenced all the cyclone
names/numbers I have available: JTWC's depression number, the
JMA-assigned name (if any), JMA's tropical storm numeric designator,
and PAGASA's name for systems forming in or passing through their
area of warning responsibility.
Northwest Pacific Tropical Activity for July
--------------------------------------------
After a very active June with five typhoons churning Northwest Pacific
waters, the month of July was rather quiet by comparison. Three tropical
storms formed, with only one reaching typhoon status. Tropical Storm
Kompasu/Julian formed just before mid-month and trekked westward, making
landfall near Hong Kong as a minimal tropical storm. Late in the month
Typhoon Namtheun formed roughly 500 nm northeast of Guam and a like
distance to the southeast of Iwo Jima. Namtheun moved northwestward,
then turned westward and moved south of Honshu toward a landfall on the
island of Shikoku. The third storm was unnamed, being classified as
a tropical storm by only NMCC and the Guangdong Regional Meteorological
Centre (GRMC). All the other warning agencies treated this system as
only a tropical depression or low-pressure area, but wind observations
recorded at several stations in southeastern China strongly suggest that
this system was a tropical storm. A report on this system, compiled and
sent by Huang Chunliang of Fuzhou City, follows. Reports on the other
two named cyclones also follow, the one on Kompasu authored by Kevin
Boyle. A special thanks to Kevin and Chunliang for their assistance.
ADDENDA TO JUNE TROPICAL CYCLONE TRACKS
For the past several months Huang Chunliang has been preparing and
sending tables summarizing the MSW estimations from the various TCWCs.
Chunliang was away at Shanghai for job-related training for most of the
months of July and August and was not able to complete the MSW tables
for the June typhoons. Following are the tables he recently sent for
Typhoon Mindulle and Typhoon Tingting.
=========================================================
== Typhoon 10W/MINDULLE/0407/IGME (Jun 21-Jul 4, 2004) ==
=========================================================
TCWC Storm ID PEAK MSW (kt)
--------------------------------------------------------------
JTWC Typhoon 10W (MINDULLE) 125
JMA Very Severe Typhoon 0407 (MINDULLE) 90
PAGASA Typhoon IGME 105
NMCC Typhoon 0407 (MINDULLE) 100
HKO Typhoon MINDULLE (0407) 90
CWB Moderate Typhoon 0407 (MINDULLE) 90
====================================================
== Typhoon 11W/TINGTING/0408 (Jun 24-Jul 4, 2004) ==
====================================================
TCWC Storm ID PEAK MSW (kt)
--------------------------------------------------------------
JTWC Typhoon 11W (TINGTING) 80
JMA Very Severe Typhoon 0408 (TINGTING) 85
NMCC Typhoon 0408 (TINGTING) 80
HKO Typhoon TINGTING (0408) --*
CWB Moderate Typhoon 0408 (TINGTING) --#
Note 1 (*): HKO never issued any real-time warnings on this typhoon,
which remained outside their AOR throughout its life.
Note 2 (#): CWB data was insufficient for me when I was away in
Shanghai.
TROPICAL STORM KOMPASU
(TC-12W / TS 0409 / JULIAN)
13 - 16 July
-----------------------------------------------
Kompasu: contributed by Japan, is the compass, a v-shaped device for
describing circles or arcs; also the name of the constellation
Circinus
A. Storm Origins
----------------
At 0600 UTC on 12 July a weak, cycling area of deep convection was
first mentioned in JTWC's STWO and located approximately 500 nm southeast
of Okinawa. Animated multi-spectral imagery revealed a possible weak
LLCC associated with this system. An upper-level analysis indicated
that the disturbance was within an area of weak shear and weak diffluence
aloft. The potential for development into a significant tropical cyclone
at this point was assessed as poor. This was upgraded to fair status in
a re-issued advisory at 12/1930 UTC.
A TCFA was issued at 13/0230 UTC after the system had become better
organized. The LLCC was well-developed at this time, but exposed as
seen in multi-spectral imagery. A QuikScat pass also showed a well-
developed tight vortex with the associated deep convection propagating
toward the southern end of an analyzed shear line. The first warning
on Tropical Depression 12W was issued at 13/0600 UTC with the centre
located 340 nm south-southeast of Okinawa and moving toward the
west at 8 kts. Even though this system was exiting an area of high
vertical shear, the dynamical aids did not indicate any further
development nor did they initialize the storm very well. Pint-sized
TD-12W spent the rest of the day tracking westward and accelerating,
its forward speed reaching 17 kts by 1800 UTC. The baby tropical
cyclone was christened Kompasu following JMA's upgrade to tropical
storm intensity at 0000 UTC on the 14th. (PAGASA named the
depression Julian at 13/1200 UTC when it entered that agency's AOR.)
B. Synoptic History
-------------------
JTWC upgraded Kompasu to a tropical storm at 14/0600 UTC when the
system was located 180 nm east-southeast of Kaoshiung, Taiwan. Kompasu
was still moving briskly toward the west or west-northwest under the
influence of a mid-level steering ridge to the northeast. The system
continued to exhibit an exposed LLCC due to continued shearing from the
east. However, a little strengthening had been occurring and the MSW
reached 40 kts at 14/1200 UTC. At this time Kompasu unexpectedly turned
west-southwestwards, and this heading ensured that the centre would pass
south of Taiwan.
Tropical Storm Kompasu/Julian did not change a great deal during the
15th. A peak intensity of 45 kts had been reached at 14/1800 UTC and
this intensity was maintained throughout the following day. The radius
of gale-force winds fluctuated in succeeding JTWC warnings, but to give
the reader some idea of Kompasu's minute size, 34-kt wind radius never
exceeded 50 nm during the maximum intensity. An interesting possibility
is that a tropical cyclone, similar to Kompasu, might have escaped
unnoticed in the pre-satellite era, especially one which did not make
landfall near a population centre like Hong Kong.
At 0000 UTC on 16 July Tropical Storm Kompasu was 85 nm southeast of
Hong Kong and moving west-northwestward at 10 kts. The system shifted
to a more poleward track and came ashore near Hong Kong at approximately
16/0900 UTC. Kompasu was barely at tropical storm intensity by the time
it made landfall. The LLCC proceeded northward, leaving behind the
upper-level circulation which was being sheared toward the southwest.
The final warning was issued by JTWC at 16/1200 UTC when the centre was
continuing northward 40 nm east of Hong Kong. JMA continued to monitor
Kompasu as a tropical depression for another six hours before that agency
also dissipated the storm.
C. Meteorological Observations
------------------------------
Waglan Island reported a 10-min sustained MSW of up to 65 kts at
16/0900-1000 UTC. The lowest pressure of 996 mb was recorded between
0500-0600 UTC. (The AWS at Waglan Island sits more than 75 m above
MSL.)
The following report was sent by Huang Chunliang.
According to the HKO warnings, Tropical Storm Kompasu (0409) made
landfall over Sai Kung at around 16/0700 UTC, when it was about 25 km to
the east of Hong Kong Observatory Headquarters, its closest approach,
with a MSW of 40 kts and a CP of 990 hPa.
The HKO report on TS Kompasu can be found at the following link:
http://www.weather.gov.hk/informtc/kompasu/kompasu.htm>
In Guangdong Province, the coastal region near the mouth of Pearl
River reported sustainded winds of Beaufort Force 7 to 8, gusting to
Force 9 to 10 during the storm. Pingshan & Longqi, both located in
Shenzhen City, recorded peak gusts to 50.5 kts, while the Gulf of Daya
(Huizhou City) & Guishan (Zhuhai City) both reported gusts topping
46.7 kts.
D. Damage and Casualties
------------------------
News reports indicated that Tropical Storm Kompasu only caused minor
damage in Hong Kong. Three people were injured as a result of wind-
borne debris. However, many transportation services were either
cancelled or ran on reduced schedules, and the stock market, banks and
other institutions were closed. Emergency shelters were opened for the
homeless.
E. Addendum to July Tropical Cyclone Tracks File
------------------------------------------------
Following is the MSW comparison table prepared and sent by Huang
Chunliang. This was unavailable at the time the July tracks file was
sent.
==============================================================
== Tropical Storm 12W/KOMPASU/0409/JULIAN (Jul 11-16, 2004) ==
==============================================================
TCWC Storm ID PEAK MSW (kt)
--------------------------------------------------------------
JTWC Tropical Storm 12W (KOMPASU) 45
JMA Typhoon 0409 (KOMPASU) 45
PAGASA Tropical Storm JULIAN 40*
NMCC Tropical Storm 0409 (KOMPASU) 45
HKO Tropical Storm KOMPASU (0409) 45
CWB Weak Typhoon 0409 (KOMPASU) 40
Note (*): The MSW is merely the "peak" value based on the limited
warnings released only when the storm was travelling within the
restricted AOR, so it may have not been the real peak.
(Report written by Kevin Boyle with contributions by Huang Chunliang.)
TYPHOON NAMTHEUN
(TC-13W / TY 0410)
24 July - 1 August
--------------------------------------
Namtheun: contributed by Laos, is the name of a river--one of the
tributaries of the Mekong River
A. Storm Origins
----------------
The origins of July's only typhoon lay in an area of convection which
formed on 23 July about 470 nm northeast of Guam and was persistent.
Animated multi-spectral and water vapor imagery revealed upper-level
divergence into an upper-level LOW east of a possible LLCC. A QuikScat
pass depicted a very weak circulation embedded in an elongated area of
broad troughing, and an upper-level analysis suggested an environment
of low vertical shear and fair divergence. At 24/0600 UTC the system
was relocated two degrees poleward to a point approximately 540 nm
northeast of Guam. The potential for development was upped to fair at
24/1100 UTC as deep convection was increasing over the LLCC. A recent
QuikScat pass indicated stronger winds in the northeast quadrant, but
the core of the circulation remained weak. An upper-level analysis
indicated that anticyclonic flow was centered over the LLCC with good
outflow in the equatorward direction.
B. Synoptic History
-------------------
JMA classified the system as a 30-kt tropical depression at 24/1200
UTC, and JTWC issued a TCFA at 24/1400 UTC. The area of convection was
quasi-stationary approximately 530 nm northeast of Guam, and satellite
imagery indicated that deep convection was continuing to increase over
the LLCC, even though a recent QuikScat pass showed that the LLCC was
still very disorganized and not co-located with the mid-level rotation.
JTWC's first warning on Tropical Depression 13W was issued at 0000 UTC
on 25 July. The center was located about 550 nm east-southeast of Iwo
Jima and was drifting north-northwestward at 2 kts. A mid-level
steering ridge to the northeast was forecast to continue guiding the
tropical cyclone to the north-northwest. At 25/1200 UTC both JTWC
and JMA upgraded the depression to tropical storm status with the latter
agency assigning the name Namtheun. Satellite CI estimates were 35
and 55 kts, but a 25/0409 UTC CIMSS AMSU intensity estimation product
showed the system to be near 992 mb, and recent 85-GHz SSM/I passes
revealed a possible mid-level eye forming. The MSW was set at 50 kts
in JTWC's warning and at 40 kts (10-min avg) in JMA's warning. By
1800 UTC Tropical Storm Namtheun was passing approximately 400 nm east
of Iwo Jima, still tracking northwestward.
The 26th of July was a day of rapid intensification for Namtheun.
JTWC upgraded the system to a 65-kt typhoon at 26/0000 UTC when it was
centered about 370 nm east of Iwo Jima. The MSW was bumped up to 90 kts
at 0600 UTC based on CI estimates of 77 and 102 kts. A 26/0328 UTC
AMSR-E pass revealed a 15-nm eye surrounded by a well-defined banding
feature. At the same time JMA increased the intensity (10-min avg) from
55 kts to 80 kts. By 1800 UTC winds had increased to an estimated
115 kts with the typhoon located approximately 300 nm east-northeast of
Iwo Jima. This, however, proved to be Namtheun's peak intensity. (JMA's
peak 10-min avg MSW was 85 kts with an attendant CP of 945 mb.) At its
peak intensity Namtheun was a rather small typhoon with gales covering
an area about 200 nm in diameter. The radius of typhoon-force winds was
estimated at 30 nm.
Typhoon Namtheun continued tracking steadily northwestward on the 27th
as it slowly began to weaken. The eye was no longer evident in EIR
imagery by 1200 UTC and the MSW was brought down to 105 kts, and at 1800
UTC the intensity was reduced further to 90 kts. Namtheun was then
centered about 360 nm southeast of Tokyo and moving northwestward at
10 kts. On 28 July Namtheun's track changed to more of a west-
northwesterly heading. The storm held its 90-kt intensity until 1200 UTC
when it was lowered to 80 kts. By 0000 UTC on 29 July Namtheun was
moving due westward at around 4 kts as it passed a little over 200 nm
due south of Tokyo, and this westerly motion continued throughout the
day. The MSW remained pegged at 80 kts until 29/1800 UTC when it was
decreased slightly to 75 kts. A 29/1143 UTC SSM/I pass in the 37-GHz
band revealed a ragged, 50-nm diameter eye. Animated water vapor imagery
showed that deep convection in the northwest quadrant was decreasing as
the system encountered northerly flow aloft and drier low-level inflow
from Japan.
Typhoon Namtheun continued to move generally westward south of Japan
on the 30th. At 1200 UTC the cyclone was centered approximately 280 nm
southwest of Tokyo. JTWC reduced the MSW to 65 kts, based on CI esti-
mates ranging from 55 to 77 kts plus a UW-CIMSS CP estimate of 975 mb,
which would correspond to a MSW of around 66 kts. Drier air from Japan
had continued to erode the convection in the western semicircle of the
storm with deep convection now restricted to the eastern quadrants.
JTWC downgraded Namtheun to tropical storm status at 30/1800 UTC with
CI estimates still ranging from 55 to 77 kts. Interestingly, JMA main-
tained Namtheun as a typhoon for another 18 hours after JTWC's downgrade.
The storm's heading became increasingly northwesterly on 31 July as it
tracked around the southwestern periphery of the steering ridge east of
Japan. At 31/0600 UTC Namtheun was centered approximately 80 nm east-
southeast of Iwakuni, Japan, moving northwestward at 11 kts. JTWC's
peak MSW was 55 kts, but JMA was still treating Namtheun as a minimal
typhoon. By 1200 UTC the center had moved inland over the Japanese
island of Shikoku, and by 1800 UTC had crossed western Honshu and emerged
into the Sea of Japan.
At 0000 UTC on 1 August Namtheun's center was in the Sea of Japan
about 105 nm east of Busan, South Korea, tracking slowly northwestward.
Winds were down to 35 kts as a result of terrain-induced weakening; also,
the LLCC was lagging behind the upper-level circulation due to increased
shear. At 01/0600 UTC the cyclone was moving slowly northward east of
South Korea. Satellite CI estimates ranged from 25 to 35 kts, but JTWC
deemed the system to be extratropical and issued their final warning.
JMA carried Namtheun through one more warning cycle, then downgraded the
system to a depression and issued their final warning at 1200 UTC.
C. Meteorological Observations
------------------------------
Karl Hoarau sent me some hourly observations from the station at
Murotomisaki (WMO 47899). The eye of Typhoon Namtheun passed 18 nm to
the south of the station around 0200 UTC on 31 July. The storm had
already been downgraded by JTWC but was still being carried as a typhoon
by JMA. The following pressures have been reduced to sea level, and the
winds represent 10-min mean winds.
30 July at 2100 UTC 991.2 mb 51 kts
2200 UTC 989.7 mb 70 kts
2300 UTC 988.4 mb 72 kts
31 July at 0000 UTC 986.8 mb 77 kts
0100 UTC 984.9 mb 87 kts
0200 UTC 984.2 mb 91 kts
0300 UTC 985.6 mb 76 kts
0400 UTC 989.6 mb 68 kts
0500 UTC 992.3 mb 53 kts
One fact which should be kept in mind is that the Murotomisaki station
is located on a cape at an elevation of 185 metres. (A special thanks to
Karl for sending these observations.)
D. Damage and Casualties
------------------------
I have received no reports of damage of casualties resulting from
Typhoon Namtheun.
E. Additional Observations
--------------------------
At the last minute I received a report from Huang Chunliang of
observations from Japanese stations. I have included the report
essentially just as he sent it. A special thanks to Chunliang for
sending the data.
NOTE: To convert metres/second (m/s) to knots approximately, just
double the m/s: e.g., 35 m/s ~= 70 kts. To convert precisely,
divide m/s by 0.51444: e.g., 35 m/s = 68 kts.
{Part I}. Landfalls (base on the JMA warnings)
==============================================
1. Severe Typhoon 0410 (NAMTHEUN) made landfall in western Kochi
Prefecture around 31/0700 UTC with a MSW of 35 m/s and a CP of 980 hPa.
2. Typhoon 0410 (NAMTHEUN) made landfall near Hiroshima City, Hiroshima
Prefecture around 31/1230Z with a MSW of 23 m/s and a CP of 992 hPa.
{Part II}. Top-5 storm totals [29/1500-02/1500Z]
================================================
Ranking Prefecture Station Rainfall (mm)
-------------------------------------------------------------
01 Tokushima Asahimaru 1243
02 Nara Mt.Hidegatake 1153
03 Tokushima Kitou 980
04 Tokushima Fukuharaasahi 936
05 Kochi Shigetou 772
{Part III}. Top-5 daily rainfall obs
====================================
Ranking Prefecture Station Rainfall (mm)
----------------------------------------------------------------------
01 Tokushima Asahimaru 588*[31/1500-01/1500Z]
02 Nara Mt.Hidegatake 588 [30/1500-31/1500Z]
03 Tokushima Fukuharaasahi 516 [30/1500-31/1500Z]
04 Kochi Yanase 514 [30/1500-31/1500Z]
05 Tokushima Kitou 512*[31/1500-01/1500Z]
{Part IV}. Top-5 hourly rainfall obs
====================================
Ranking Prefecture Station Rainfall (mm)
----------------------------------------------------------------------
01 Kochi Nakamura 117*[01/1540-01/1640Z]
02 Kochi Shigetou 110*[01/0000-01/0100Z]
03 Ehime Chikanaga 104*[01/1410-01/1510Z]
04 Kochi Motoyama 92 [01/0910-01/1010Z]
05 Kochi Kubokawa 91*[01/1140-01/1240Z]
{Part V}. Top-5 peak sustained wind (10-min avg) obs
====================================================
Ranking Station Peak wind (mps/dir)
-------------------------------------------------------------------------
01 Murotomisaki, Kochi (WMO47899, Alt 185m) 47.7/E [31/0210Z]
02 Hiwasa, Tokushima (JMA71266, Alt 3m) 22 /E [31/0310Z]
03 Shionomisaki, Wakayama (WMO47778, Alt 73m) 19.0/E [30/1810Z]
04 Tsu, Mie (WMO47651, Alt 3m) 18.1/ESE [31/0320Z]
05 Tamano, Okayama (JMA66501, Alt 2m) 18 /E [31/1250Z]
{Part VI}. Top-5 peak gust obs
==============================
Ranking Station Peak wind (mps/dir)
-------------------------------------------------------------------------
01 Murotomisaki, Kochi (WMO47899, Alt 185m) 60.9/ENE [31/0200Z]
02 Hachijojima, Tokyo (WMO47678, Alt 79m) 44.6/ENE [29/0703Z]
03 Shionomisaki, Wakayama (WMO47778, Alt 73m) 37.8/ENE [30/0812Z]
04 Owase, Mie (WMO47663, Alt 15m) 36.8/E [30/2344Z]
05 Kure, Hiroshima (WMO47766, Alt 4m) 31.1/NNE [31/0902Z]
{Part VII}. Top-5 SLP obs
=========================
Ranking Station Min SLP (hPa)
----------------------------------------------------------------
01 Murotomisaki, Kochi (WMO47899) 983.3 [31/0237Z]
02 Shimizu, Kochi (WMO47898) 989.2 [31/0555Z]
03 Sukumo, Kochi (WMO47897) 989.9 [31/0647Z]
04 Matsuyama, Ehime (WMO47887) 990.3 [31/0948Z]
05 Kochi, Kochi (WMO47893) 990.5 [31/0431Z]
{Part VIII} References (Japanese versions only)
===============================================
http://www.data.kishou.go.jp>
http://www.osaka-jma.go.jp>
http://www.tokyo-jma.go.jp>
NOTE: "*" = record-breaking values for relevant stations.
F. Addendum to July Tropical Cyclone Tracks File
------------------------------------------------
Following is the MSW comparison table prepared and sent by Huang
Chunliang. This was unavailable at the time the July tracks file was
sent.
====================================================
== Typhoon 13W/NAMTHEUN/0410 (JuL 24-Aug 3, 2004) ==
====================================================
TCWC Storm ID PEAK MSW (kt)
--------------------------------------------------------------
JTWC Typhoon 13W (NAMTHEUN) 115
JMA Very Severe Typhoon 0410 (NAMTHEUN) 85
NMCC Typhoon 0410 (NAMTHEUN) 100
HKO Typhoon NAMTHEUN (0410) ---*
CWB Moderate Typhoon 0410 (NAMTHEUN) ---#
Note 1 (*): HKO never issued any real-time warnings on this typhoon,
which remained outside their AOR throughout its life.
Note 2 (#): CWB data was insufficient for me when I was away in
Shanghai.
(Sections A-D written by Gary Padgett; Sections E & F compiled by Huang
Chunliang)
TROPICAL STORM
(NMCC 0411 / NRL Invest 94W)
26 - 27 July
------------------------------------------------
A. Introduction
---------------
Only NMC and GRMC, both sub-agencies of CMA (China Meteorological
Administration), classified the system as a tropical storm in real time,
while HKO, JMA, TMD and SMG (Macao) ranked it as a tropical depression
only. Another three TCWCs: JTWC, CWB and PAGASA, however, just treated
94W as a tropical disturbance/low-pressure area. It should be noted
that the last time there was a NMC tropical storm without a JMA number
(i.e., JMA never regarded it as a tropical storm) was in mid-December,
1999, when NMC issued several warnings on a SCS tropical storm (numbered
TS-9917 by NMC and TD-33W by JTWC).
B. Synoptic History
-------------------
Both NMC and GRMC initiated warnings on TD-03 at 26/0600 UTC. And
the MSW of 30 kts was kept for three warning cycles before two ships
reported winds of gale force in the wee hours on the 27th (locally).
So the depression was upgraded to Tropical Storm 0411 at 27/0000 UTC.
It took only three hours for the unnamed storm, which turned out to be
a short fuse, to make landfall. According to the NMC and GRMC warnings,
Tropical Storm 0411 made landfall in the coastal region between Huilai
County and Lufeng City, Guangdong Province around 27/0305 UTC with a
MSW of 40 kts and a CP of 995 hPa. Once inland, the storm began to
fade rapidly. The cyclone was downgraded to a 25-kt depression at
27/0600 UTC, at which time China issued their final warning.
C. Meteorological Observations
------------------------------
(1) Wind Observations
---------------------
The majority of the counties/cities of coastal southeastern Guangdong:
Jieyang, Shantou and Shanwei Cities, as well as some counties/cities of
Chaozhou City, reported sustained winds of Beaufort Force 6 to 8,
gusting to Force 9 to 10 during the storm. Significant gust reports
included:
Station Jiadong, Lufeng City (a sub-city of Shanwei City) - 52.7 kts
Huilai Chuanqiao Reservoir (Huilai County, Jieyang City) - 49.2 kts
(2) Rainfall Observations
-------------------------
(a) Guangdong Province
----------------------
[27/0000-28/0000 UTC]: Rains >50 mm were recorded in 33 counties/cities,
among which, Heping County, Fengshun County, Wengyuan County, Chaozhou
City, Lianping County, Chao'an County, Shantou City and Chaoyang City
reported rains >100 mm with Qingzhou, Heping County reporting the highest
amount of 170.2 mm.
[28/0000-29/0000 UTC]: Rains >50 mm were recorded in 29 counties/cities,
among which, Shanwei City, Sihui City, Zhongshan City, Fengkai County,
Raoping County and Zhuhai City reported rains >100 mm with Nanlang,
Zhongshan City reporting the highest amount of 182.6 mm.
[29/0000-30/0000 UTC]: Rains >50 mm were recorded in 28 counties/cities,
among which, Huilai County, Maoming City, Puning City, Suixi County
reported rains >100 mm with Maoming City reporting the highest amount of
112.5 mm.
(b) Fujian Province
-------------------
[27/0000-29/0000 UTC]: 3 stations (Yunxiao, Zhaoan & Dongshan) located in
southern Fujian recorded rains >100 mm with Yunxiao County, Zhangzhou
City reporting the highest amount of 116.6 mm.
(c) Artificial Rain
-------------------
Artificial rainfall missions were selectively carried out in a few
regions of both Guangdong and Fujian Provinces, where drought was relaxed
to some extent thanks to the rains, whether artificial or not.
D. Damage and Casualties
------------------------
In Nan'ao County, Shantou City, 11 fishermen were confirmed dead and
another 11 were reported missing and feared dead after a fishing vessel
capsized near Guangdong's Nanpeng Dao around the noon of July 27
(locally).
In Huilai County, Jieyang City, another fishing boat was bowled over
by the stormy waves, leaving two fishermen missing in the evening of
July 27 (locally).
In Chao'an County, Chaozhou City, one person was killed when a tornado
hit the county's Fengtang and Fuyang Towns around 27/1100 (BJT). Another
seven residents were injured when more than 100 houses in four villages
were damaged or destroyed. Preliminary statistics indicated that a total
of 409 people from 93 families sustained damaged with 24 families home-
less. Direct economic losses were estimated at 11.2 million yuan.
Damage to coastal dikes, water conservation facilities and farmlands
was also reported in the Province.
E. Addendum to July Tropical Cyclone Tracks File
------------------------------------------------
Following is the MSW comparison table prepared and sent by Huang
Chunliang. This was unavailable at the time the July tracks file was
sent.
====================================================
== Tropical Storm 94W/0411/TD03 (Jul 26-27, 2004) ==
====================================================
TCWC Storm ID PEAK MSW (kt)
--------------------------------------------------------------
JMA Tropical Depression 30
NMCC Tropical Storm 0411/TD03* 45
HKO Tropical Depression 30
TMD Tropical Depression 30
Note 1: In the title line the storm grade was adopted based on the
classification of the most "radical" TCWC. Also, all the storm names/
numbers available to me have been referenced. In addition, the starting
date points to the one when the system was initially upgraded to TD
status by whatever TCWC, while the ending date represents the one when
the storm was finally ranked as a TD by whatever TCWC. (In this regard,
NMCC was the TCWC that took the lead in upgrading the system to TD
status on the 26th, while all the four agencies above issued their final
TC bulletins at 27/0600 UTC.)
Note 2 (*): The system was numbered "TD03" at 26/0600 UTC, when NMCC
initiated their TC warnings.
Note 3: Only NMC and GRMC, both sub-agencies of CMA (China Meteorological
Administration), classified the system as a tropical storm in real time,
while HKO, JMA, TMD and SMG (Macao) ranked it as a tropical depression
only. Another three TCWCs, JTWC, CWB & PAGASA, however, just treated
94W as a tropical disturbance/low-pressure Area.
(Report written by Huang Chunliang with slight editing by Gary Padgett)
*************************************************************************
NORTH INDIAN OCEAN (NIO) - Bay of Bengal and Arabian Sea
Activity for July: No tropical cyclones
*************************************************************************
SOUTHWEST INDIAN OCEAN (SWI) - South Indian Ocean West of Longitude 90E
Activity for July: No tropical cyclones
*************************************************************************
NORTHWEST AUSTRALIA/SOUTHEAST INDIAN OCEAN (AUW) - From 90E to 135E
Activity for July: No tropical cyclones
*************************************************************************
NORTHEAST AUSTRALIA/CORAL SEA (AUE) - From 135E to 160E
Activity for July: No tropical cyclones
*************************************************************************
SOUTH PACIFIC (SPA) - South Pacific Ocean East of Longitude 160E
Activity for July: No tropical cyclones
*************************************************************************
EXTRA FEATURE
In order to shorten the amount of typing in preparing the narrative
material, I have been in the habit of freely using abbreviations and
acronyms. I have tried to define most of these with the first usage
in a given summary, but I may have missed one now and then. Most of
these are probably understood by a majority of readers but perhaps a
few aren't clear to some. To remedy this I developed a Glossary of
Abbreviations and Acronyms which I first included in the July, 1998
summary. I don't normally include the Glossary in most months in
order to help keep them from being too long. If anyone would like to
receive a copy of the Glossary, please e-mail me and I'll be happy
to send them a copy.
*************************************************************************
AUTHOR'S NOTE: This summary should be considered a very preliminary
overview of the tropical cyclones that occur in each month. The cyclone
tracks (provided separately) will generally be based upon operational
warnings issued by the various tropical cyclone warning centers. The
information contained therein may differ somewhat from the tracking and
intensity information obtained from a "best-track" file which is based
on a detailed post-seasonal analysis of all available data. Information
on where to find official "best-track" files from the various warning
centers will be passed along from time to time.
The track files are not being sent via e-mail. They can be retrieved
from the archive sites listed below. (Note: I do have a limited e-mail
distribution list for the track files. If anyone wishes to receive
these via e-mail, please send me a message.)
Both the summaries and the track files are standard text files
created in DOS editor. Download to disk and use a viewer such as
Notepad or DOS editor to view the files.
The first summary in this series covered the month of October,
1997. Back issues can be obtained from the following websites
(courtesy of Michael Bath, Michael V. Padua, Michael Pitt, and
Chris Landsea):
http://australiasevereweather.com/cyclones/>
http://www.typhoon2000.ph>
http://mpittweather.com>
ftp://ftp.aoml.noaa.gov/hrd/pub/landsea/padgett/>
Another website where much information about tropical cyclones may
be found is the website for the UK Meteorological Office. Their site
contains a lot of statistical information about tropical cyclones
globally on a monthly basis. The URL is:
http://www.met-office.gov.uk/sec2/sec2cyclone/sec2cyclone.html>
TROPICAL CYCLONE REPORTS AVAILABLE
JTWC now has available on its website the complete Annual Tropical
Cyclone Report (ATCR) for 2003 (2002-2003 season for the Southern
Hemisphere). ATCRs for earlier years are available also.
The URL is: http://199.10.200.33/jtwc.html>
Also, TPC/NHC has available on its webpage nice "technicolor"
tracking charts for the 2003 Atlantic and Eastern North Pacific
tropical cyclones; also, storm reports for all the 2003 Atlantic
and Eastern North Pacific cyclones are now available, as well as
track charts and reports on storms from earlier years.
The URL is: http://www.nhc.noaa.gov>
A special thanks to Michael Bath of McLeans Ridges, New South Wales,
Australia, for assisting me with proofreading the summaries.
PREPARED BY
Gary Padgett
E-mail: [email protected]
Phone: 334-222-5327
Kevin Boyle (Eastern Atlantic, Western Northwest Pacific, South
China Sea)
E-mail: [email protected]
John Wallace (Assistance with Eastern North Pacific)
E-mail: [email protected]
Huang Chunliang (Assistance with Western Northwest Pacific, South
China Sea)
E-mail: [email protected]
Simon Clarke (Northeast Australia/Coral Sea, South Pacific)
E-mail: [email protected]
*************************************************************************
*************************************************************************
|
Document: summ0407.htm
Updated: 17th May, 2005 |
[Australian Severe Weather index] [Copyright Notice] [Email Contacts] [Search This Site] |