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Storm News
[Index][Aussie-Wx] |
Australian Weather Mailing List Archives: Friday, 17 December 1999 |
From Subject
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001 "James Chambers" [jamestorm at ozemail.com.au] Re: Ray Wilkie
002 Mark Dwyer [mjd at wantree.com.au] Further West Aus Upadtes on TC " John "
003 Anthony Cornelius [cyclone at flatrate.net.au] Nine network anals & progs
004 "Leslie R. Lemon" [lrlemon at compuserve.com] Nine network anals &
005 Harald Richter [spatz at atmos.albany.edu] SRH and CAPE
006 "Leslie R. Lemon" [lrlemon at compuserve.com] Nine network anals &
007 "Leslie R. Lemon" [lrlemon at compuserve.com] Nine network anals &
008 "Leslie R. Lemon" [lrlemon at compuserve.com] Nine network anals & progs
009 Carl Smith [carls at ace-net.com.au] ILSA 1600 UT map animation update
010 "Willis, Andrew" [adwillis at bechtel.com] Explain please... :)
011 Les Crossan [les.crossan at virgin.net] Explain please... :)
012 "Jane ONeill" [cadence at rubix.net.au] Explain please... :)
013 "Leslie R. Lemon" [lrlemon at compuserve.com] Explain please... :)
014 "Leslie R. Lemon" [lrlemon at compuserve.com] Explain please... :)
015 Harald Richter [spatz at atmos.albany.edu] SRH and CAPE
016 Anthony Cornelius [cyclone at flatrate.net.au] Explain please... :)
017 Les Crossan [les.crossan at virgin.net] Explain please... :)
018 Anthony Cornelius [cyclone at flatrate.net.au] Nine
019 Les Crossan [les.crossan at virgin.net] SRH and CAPE
020 Lindsay [writer at lisp.com.au] Powder snow
021 Lindsay [writer at lisp.com.au] TC John has made land...........
022 Blair Trewin [blair at met.Unimelb.EDU.AU] Heavy rain in various parts of the country...
023 Blair Trewin [blair at met.Unimelb.EDU.AU] Seriously weird forecasts on the web
024 "Michael Thompson" [michaelt at ozemail.com.au] Powder snow
025 Michael Scollay [michael.scollay at telstra.com. Powder snow
026 "weatherhead" [weatherhead at ozemail.com.au] Seriously weird forecasts on the web
027 Blair Trewin [blair at met.Unimelb.EDU.AU] Seriously weird forecasts on the web
028 Lindsay [writer at lisp.com.au] Great Britian Minima
029 Lindsay [writer at lisp.com.au] UK weather
030 Lindsay [writer at lisp.com.au] Guyra info
031 Lindsay [writer at lisp.com.au] Powder snow
032 Blair Trewin [blair at met.Unimelb.EDU.AU] Great Britian Minima
033 Paul.Mossman at DWNNICH.OCA.nt.gov.au Great Storm..........
034 "Mark Hardy" [mhardy at magna.com.au] Nine network anals & progs
035 Anthony Cornelius [cyclone at flatrate.net.au] SRH and CAPE
036 Les Crossan [les.crossan at virgin.net] Seriously weird forecasts on the web
037 Norman Lynagh [lynagh at dial.pipex.com] Great Britian Minima
038 Les Crossan [les.crossan at virgin.net] Great Britian Minima
039 Norman Lynagh [lynagh at dial.pipex.com] Seriously weird forecasts on the web
040 astroman [astroman at chariot.net.au] Snowtown report up and running
041 Anthony Cornelius [cyclone at flatrate.net.au] Nine network anals &progs
--------------------------------------------------------------------------------------
001
From: "James Chambers" [jamestorm at ozemail.com.au]
To: "aus-wx" [aussie-weather at world.std.com]
Subject: aus-wx: Re: Ray Wilkie
Date: Thu, 16 Dec 1999 22:58:54 +1000
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Hi all
I agree with everything Michael said. The standard of weather presentation
in Brisbane is sure to nose-dive after his retirement. Hopefully Ch 10 will
replace him with someone who at least knows something about weather! Ray,
if you reading this (not likely), have a happy retirement!!
Regards
James Chambers
Michael said:
>Amongst the discussion of television weather it should be noted that one of
Australia's most respected television weather journalists, Ray Wilkie,
retires tomorrow night after 20 years of quality weather presenting on
Channel 10 in Brisbane. The award winning metrologist
has always presented his segments in an informative and factual way. He
never used an autocue rather he shared his knowledge with the viewer through
his many years experience before television working in the BOM.
I urge all fellow Qlders on the list to tune in to his last bulletin at
5:55pm tomorrow night because the current thinking of economic rationalism
will mean that we will not see this type of presentation again.
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002
Date: Thu, 16 Dec 1999 21:55:24 +0800
From: Mark Dwyer [mjd at wantree.com.au]
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To: "aussie-weather at world.std.com" [aussie-weather at world.std.com]
Subject: aus-wx: Further West Aus Upadtes on TC " John "
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Here are some more newspaper articals from the West Australian from
Wednesday WST, 14/12/1999...enjoy the read......, more to come from
todays paper as i have time to scan it, and upload it.
Here are the url's ok...
http://users.wantree.com.au/~mjd/westaus141299_1b.jpg <--- front page...
http://users.wantree.com.au/~mjd/westaus141299_6&7b.jpg <---Pages 6 &
7...
MJ
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003
Date: Thu, 16 Dec 1999 23:58:56 +1000
From: Anthony Cornelius [cyclone at flatrate.net.au]
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To: aussie-weather at world.std.com
Subject: Re: US/AU Conditions (was) Re: aus-wx: Nine network anals & progs
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Hi Paul,
Paul Mossman wrote:
>
> And what CAPEs do Tropical areas get??............. I suspect higher
> then usual because of 33c / DP of 25 etc but you didnt seem to mention
> that.............
>
> Paul.
I actually left the tropics out, as Leslie asked for information outside
of tropical regions. Naturally, the tropics frequently get high CAPE's,
but I would suspect that they would not receive the extreme CAPE's quite
as often. Even though they certainly get the temps/DP's - their very
warm upper atmosphere compensates for this.
To be honest, I haven't paid quite as close attention to tropical
CAPE's, but would suspect that they wouldn't exceed 5000-6000 very often
(at least in Australia). The 'norm' max CAPE would sit between
2500-4000 daily in most tropical areas, but this is very variable.
AVN CAPE analysis does a very poor job in the the tropics CAPE
analysis. Although I suspect that it uses a slightly different
equation/method to calculate CAPE, as there are a few methods of parcel
plotting.
I think I mentioned in an earlier email, that even though there's such
high amounts of CAPE, shear is nearly non-existant. And even though the
higher your CAPE, the less shear needed (within reason), there are other
requirements. IE - speed sheer, dry layer in the upper atmosphere to
assist in evaporation, water loading, divergent upper levels are all
non-existant in much of the tropics.
This does not, however mean the storms that occur there aren't any less
spectacular! A storm doesn't have to be severe to give magnificent
structure, and/or brilliant lightning - and that's the true love/joy of
thunderstorms - the amazing structures that are created by them!
--
Anthony Cornelius
Queensland Coordinator of the Australian Severe Weather Association
(ASWA)
(07) 3390 4812
14 Kinsella St
Belmont, Brisbane
QLD, 4153
Please report severe thunderstorms on our Queensland severe thunderstorm
reporting line on (07) 3390 4218 or by going to our homepage at
http://www.severeweather.asn.au
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004
Date: Thu, 16 Dec 1999 11:20:10 -0500
From: "Leslie R. Lemon" [lrlemon at compuserve.com]
Subject: Re: US/AU Conditions (was) Re: aus-wx: Nine network anals &
progs
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Paul and Anthony and all:
Owing to the much warmer air (and moist air) aloft, tropical CAPEs are, I
believe, rather low (a few hundred or even less). Keep in mind that CAPE
is the integral of the buoyant energy, the temperature difference between
the environment and the rising parcel (moist adiabatic). As you know the
LI's in the tropics are usually quite modest (~+1 to -3). Once again that
is because the temperatures at 500 mb are warm, "substantially" warmer than
in mid-latitudes. This, in turn, accounts for the low updraft vertical
velocities and smaller dropsize distributions typically found in tropical
convection. Moreover, environmental shear is low in the topics, thus
updraft augmentation due to environmental shear is not available, either.
This is as I understand it.
Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Phone: 816-373-3533
E-Mail: lrlemon at compuserve.com
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005
From: Harald Richter [spatz at atmos.albany.edu]
Subject: aus-wx: SRH and CAPE
To: aussie-weather at world.std.com (Australian Severe Weather Association)
Date: Thu, 16 Dec 1999 16:29:54 +0000 (GMT)
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Hi Anthony (and eavesdropers),
I enjoyed your discussion of SRH/CAPE. One
conclusion that I have arrived at is the *sensitivity*
of these two 'discriminators' to a number of things.
You can easily produce a 10,000+ CAPE sounding by
measuring T/Td in a steamy corn field after a weak
warm shower (this has been done in Western Iowa some months
back). Then you take that same thermometer/psychrometer, walk
away from that steamy corn field out into the
parking lot - your CAPE is down to 3000 J/kg.
"Representativeness" is another big concern when relating
CAPE (and SRH) to actual storms. Did the sounding go
up in the inflow sector of the storm, or was it launched
through a shallow cold pool on the cool side
of a boundary along which the storm happened to ride?
Climatologies that I have seen (I am thinking of Erik Rasmussen's
1992 clim.) have convinced me that "standard" CAPE and
"standard" SRH have no more than *some* value in discriminating
between supercells and non-supercells.
The storm motion/circulation itself has a significant
impact on CAPE/SRH. When a supercell turns right/left, its
SRH might double or drop to a half.
Mixing is a player in diluting originally high-CAPE parcels.
I guess my point is that there's a number of processes
out there (= where the storms are/should be) that can easily
double/halve CAPE/SRH values AND storms might "feel"
CAPE/SRH values vastly different from the ones that we are
able to compute. Still, until someone (on this list???)
comes up with something better, CAPE/SRH is it.
Harald
P.S.: My suggestion -- the "Cornelius Index (CI)"
CI < 0 --> no supercells
CI > 0 --> supercells
CI = 1 --> F1 tornado
CI = 5 --> F5 tornado
Now that I've done the hard stuff, could you
(A.) finish off the details, please :)
--
------------------------------------------------------
Harald Richter
Postdoctoral Research Associate
Department of Earth and Atmospheric Sciences
State University of New York at Albany
1400 Washington Avenue
Albany, NY 12222
phone: (518) 442-4273 fax: (518) 442-4494
spatz at atmos.albany.edu
http://www.atmos.albany.edu/facstaff/spatz/spatz.html
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006
Date: Thu, 16 Dec 1999 12:21:47 -0500
From: "Leslie R. Lemon" [lrlemon at compuserve.com]
Subject: Re: US/AU Conditions (was) Re: aus-wx: Nine network anals &
progs
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Jonty and Anthony:
> There is in deed a "trade off" between SRH and CAPE.
I apologize for forgetting to include in my discussion yesterday the
effects of environmental shear on updraft augmentation. SRH incorporates
that shear as do a few other proposed indices. SRH is proportional to the
area swept out by the storm relative (s-r) wind vectors between two levels
on the hodograph. That is generally considered to be important to the
storm when the layer from the surface to the top of the inflow layer is
considered. The top of the inflow layer is generally considered as the LFC
(Level of Free Convection). SRH integrates effects of s-r winds and
streamwise vorticity for the inflow layer approximated for many studies to
be the lowest 2 to 3 km of the sounding. This is provides an estimate for
an updrafts 'rotational potential'. It is sensitive to storm motion and
vertical wind shear. It is particularly strong when the hodograph is
curved. This is associated with strong s-r inflow.
EHI is similar to the Bulk Richardson number, in that it expresses the
relationship of buoyancy (thermodynamics) and wind shear (kinematics). We
know that there is a rough relationship among quantities such as SRH and
EHI and BR and supercell occurrence and perhaps more importantly tornado
production and strength. Interestingly enough, when regression analyses
have been done, the one parameter which seems to have the greatest
potential, the best direct correlation and association itself and tornado
occurrence is the LFC!!! The lower the LFC the greater the potential for
tornado development in environments that support severe thunderstorms.
This may be associated with how near the surface vortex stretching (and
thus amplification due to stretching) becomes important.
As some of you know, I personally belive that one of the reasons quantities
like SRH, BR, and EHI have, at least in part, failed as direct measures of
mesocyclone potential, and strength, and tornado potential is that the
mesocyclone and the environment for the tornado is NOT A ROTATING UPDRAFT.
In reality the abundance of data suggest very very strongly (I believe with
certainty) that the mesocyclone is analogous to the extratropical cyclone.
That is, the updraft is only 1/2 of the mesocyclone. The other half is the
RFD. So, the mesocyclone is made up of a (warm sector) rising and turning
updraft and a (cold sector) descending and turning downdraft. The tornado
is located just on the updraft side but within the gradient of these two
drafts near the circulation center. That concept has been published in
several forms both by myself and myself and Doswell from about 1970 up to
the present. However, many still stick with the mesocyclone/rotating
updraft concept. But then, this is an area of some controversy and
although I feel I have sufficient evidence to prove the
mesocyclone-extratropical-cyclone analogy, it is not accepted by many
others. Doppler radar, aircraft, surface observations, some numerical
models, and VORTEX results all tend to support the concept. Time and
observations will eventually tell. The bottom line is that we have much
more to learn and our understanding is greatly imperfect.
Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Phone: 816-373-3533
E-Mail: lrlemon at compuserve.com
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007
Date: Thu, 16 Dec 1999 12:42:20 -0500
From: "Leslie R. Lemon" [lrlemon at compuserve.com]
Subject: Re: US/AU Conditions (was) Re: aus-wx: Nine network anals &
progs
To: "INTERNET:aussie-weather at world.std.com" [aussie-weather at world.std.com]
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Jonty and all:
This discussion is great! Once again I am impressed with how much
knowledge there is in a group of supposed "armatures"!!! It is for that
reason I would urge some of you to consider submitting papers to
conferences. There have been some very significant contributions by
"non-professional" storm chasers to the science.
> highest of the 35 had a CAPE of about 4500 Jkg^-1). It does seem that
> there can be some form of "trade off" between SRH and CAPE in the
> conditions necessary for these storms, but it was difficult to relate the
> Plainfield storm to the others because it was pretty unique (have there
> been other similar situations since then?).
No, to my knowledge, there haven't been any just like Plainfield. However,
we have since learned that the concept of SRH (and other parameters) must
be viewed in very much a storm relative perspective. Don Burgess and
myself wrote a paper, using NEXRAD observations, where we clearly showed
that the storm itself modifies its environment and augments its own
near-storm SRH by accelerating updraft inflow. However, Browning (1978)
and many others including VORTEX observations have demonstrated how a
mesolow at the updraft base of perhaps only -0.5 mb will accelerate
low-level winds within ~ 20 km of the storm by as much as 10 m/s to 15 m/s.
Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Phone: 816-373-3533
E-Mail: lrlemon at compuserve.com
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008
Date: Thu, 16 Dec 1999 13:56:12 -0500
From: "Leslie R. Lemon" [lrlemon at compuserve.com]
Subject: US/AU Conditions (was) Re: aus-wx: Nine network anals & progs
To: "INTERNET:aussie-weather at world.std.com" [aussie-weather at world.std.com]
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Anthony and all:
> I agree with you Leslie, but I don't have any doubt that the US gets
> more than AU does - the conditions in the US can simply be phenomenal,
> on May 3, the frontal/low system that went through dropped OKC to
> 983hPa!!! I know this was a phenomenal system for you, but I don't
> think anything of this magnitude has ever occurred in AU. Certainly not
This whole post was great! (I did not recall that the surface low was that
deep on 3 May, but I may be easily mistaken.) I do think that one of the
key differences between the US and AU is the fact that the Rocky Mts. (3 to
5 km high) are immediately adjacent to the plains. They have much to do
with the lee side development of the low pressure trough and the resultant
nocturnal low-level jet (15 to 30 m/s) which transports abundant low-level
moist air from the gulf of mexico, northward. In addition they create
certain thermodynamic and kinematic environmental stratifications out on
the plains that encourage development of the cap at the upper surface of
the moist layer, abundant dry air aloft, the surface dry line, and very
favorable shear profiles. Thus, the mountainous terrain is critical to
developing or contributing to the development of the favorable environments
and the frequency of development of those environments. I do wonder,
however, what goes on in the interior of AU relative to severe storms,
hail, and tornadoes. I imagine there are some extremely impressive storms
there as well.
BTW, relative to the 3 May outbreak, as late as the morning of that day SPC
had no idea of the magnitude of the impending outbreak. Even when the risk
finally was elevated to "high", hail was emphasized as the primary threat.
Clearly there is a lot we do not understand!
I can dial up any NEXRAD in the country via my PC. (I have a demo account
with one of the NIDS distributors. This is not normally free, even here.)
I watched those storms develop and could easily see the intense
mesocyclones and even the tornadoes themselves. This was beyond anything I
have ever seen in 30 + years in that almost every storm that developed on
that day "tornadoed". As I watched the OKC storm and tornado develop and
move toward OKC-Moore-Norman areas I became emotional. I actually was
moved to tears because I have so many friends there and knew virtually no
one has a basement (as I do wherein is my office). It was so obvious this
was a disaster in the making. Further, if you can imagine this, as I
watched the storm and associated hook echo move into Moore, OK,
reflectivities in the hook went from ~ 50 dBZ to > 65 dBZ!! I knew
instantly that the cause of that phenomena was the debris from the housing
subdivisions being lofted by the tornado. Moreover, I knew that some of
that "debris" could actually be human bodies! Even before the tornado had
reached Moore, I could estimate, using the velocity products from the KTLX
NEXRAD which was only about 25 km away, that the TVS and associated
tornado, was ~ 2 km wide!!
For more on the 3 May storms see:
http://doplight.nssl.noaa.gov/~speg/may3.html, and
http://www.nwsnorman.noaa.gov/storms/3may99
http://www.kfor.com/tornado.asp,
See this site and order a very impressive and dramatic video:
http://www.kfor.com/weather/may_fury.asp. I highly recommend that you
obtain this video and show it at one of the ASWA meetings! Believe me, it
is spellbinding!
Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Phone: 816-373-3533
E-Mail: lrlemon at compuserve.com
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009
X-Sender: carls at ford.ace-net.com.au
Date: Fri, 17 Dec 1999 06:31:28 +1000
To: aussie-weather mailing list [aussie-weather at world.std.com]
From: Carl Smith [carls at ace-net.com.au]
Subject: aus-wx: ILSA 1600 UT map animation update
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
Hi All.
I've sent Phil in HK the ILSA update for the 1600 UT info, had a few hours
sleep. Be getting a couple more before 2200 update.
He will upload it when he wakes up in morning at
http://www.drdisk.com.hk/johnilsa.htm
Looks like ILSA going cross the coast near Pardoo Station, Wallal Downs
Station, Sandfire Flats Roadhouse about dawn local time - maybe 20 people
will get to experience it if they don't sleep through it - these places
back on to the vast Great Sandy Desert which is one of the hottest and
least populated parts of Australia.
Carl.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Carl Smith.
Gold Coast, Queensland, Australia.
carls at ace-net.com.au
Cyclone Tracking Maps Website:
http://www.ace-net.com.au/~carls/index.htm
Current Cyclone Information Page:
http://www.ace-net.com.au/~carls/current.htm
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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010
From: "Willis, Andrew" [adwillis at bechtel.com]
To: "'Aussie Weather'" [aussie-weather at world.std.com]
Subject: aus-wx: Explain please... :)
Date: Thu, 16 Dec 1999 12:47:08 -0800
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After reading Anthony's post about watching the May 3rd storms in Oklahoma,
I watched them develop via the WX-Chase digest and the Storm Warnings via
The Tornado Project. I'll agree that it was a chilling feeling when chasers
started predicting that the Bridge Creek Tornado was now aiming directly at
Oklahoma City. I also 'watched' the 1998 Birmingham, Alabama F5 tornado via
the warnings produced from the Tornado Project and felt the same sinking
feeling as it aimed at a major city.
Now for an amatuer, could someone fill in the blanks for me please.
CAPE = ?
SRH = ?
Andrew Willis
Desktop Support - Port Waratah Stage 3 Expansion
Eagles may soar but weasels don't get sucked into jet engines.
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011
Date: Thu, 16 Dec 1999 21:22:12 +0000
From: Les Crossan [les.crossan at virgin.net]
Organization: Cosmic EuroCon - note all times in GMT
X-Mailer: Mozilla 4.5 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: Re: aus-wx: Explain please... :)
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"Willis, Andrew" wrote:
>
> Now for an amatuer, could someone fill in the blanks for me please.
>
> CAPE = ?
Convective Available Potential Energy
>
> SRH = ?
>
S----- relative helicity??
Some of us were starting to get VERY lost at the beginning of this thread ):
Now all we need is the mathematix.
Les(UK)
btw I've got a Skew-T dating from 1960, I know CAPE is high but can someone tell
me how high by showing me the math(s)???
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012
From: "Jane ONeill" [cadence at rubix.net.au]
To: [aussie-weather at world.std.com]
Subject: Re: aus-wx: Explain please... :)
Date: Fri, 17 Dec 1999 09:12:45 +1100
X-Mailer: Microsoft Outlook Express 5.00.2014.211
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> > SRH = ?
> >
>
> S----- relative helicity??
>
Storm Relative Helicity
Jane ONeill
ASWA - Victoria
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013
Date: Thu, 16 Dec 1999 17:10:05 -0500
From: "Leslie R. Lemon" [lrlemon at compuserve.com]
Subject: Re: aus-wx: Explain please... :)
To: "INTERNET:aussie-weather at world.std.com" [aussie-weather at world.std.com]
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Les (UK):
> btw I've got a Skew-T dating from 1960, I know CAPE is high but can
someone tell
> me how high by showing me the math(s)???
Let me take a shot at this via e-mail. It is the integral of the of the dot
product of the storm relative wind vector and the horizontal vorticity
vector with respect to height over the height range of 0 to Z.
Does that make sense?
Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Phone: 816-373-3533
E-Mail: lrlemon at compuserve.com
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014
Date: Thu, 16 Dec 1999 17:23:48 -0500
From: "Leslie R. Lemon" [lrlemon at compuserve.com]
Subject: aus-wx: Explain please... :)
To: "INTERNET:aussie-weather at world.std.com" [aussie-weather at world.std.com]
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Andrew:
> After reading Anthony's post about watching the May 3rd storms in
Oklahoma,
> I watched them develop via the WX-Chase digest and the Storm Warnings via
> The Tornado Project. I'll agree that it was a chilling feeling when
chasers
That was my (Les US) description, [S]. Yes, I also used the same NEXRAD
dial-up to watch the radar in real time as the Birmingham, Alabama F5
tornado approached the city. It was chilling. One of the biggest
differences was that the storm was farther away, outside of TVS (tornadic
vortex signature) detection range for any of the NEXRADs. However, I did
in that case the same thing I did in the OKC case and that was to dial-up
several radars in the area and get a variety of views. There were many
other tornadic storms in that case as well.
Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Phone: 816-373-3533
E-Mail: lrlemon at compuserve.com
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015
From: Harald Richter [spatz at atmos.albany.edu]
Subject: aus-wx: SRH and CAPE
To: aussie-weather at world.std.com (Australian Severe Weather Association)
Date: Thu, 16 Dec 1999 23:00:25 +0000 (GMT)
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For the hardliners,
The computations could of these two popular
'convective indicators' could be done like this:
Storm-Relative Helicity =
SRH =
integral (from 0 to h) [ k * ((V-c) x dV/dz)] dz
where
k = vertical unit vector
V = total velocity vector of the ambient flow
c = motion vector of the storm (whatever that means)
dV/dz = vertical shear vector
z = vertical coordinate
h = commonly the level of free convection (~ 3km)
Convective Available Potential Energy =
CAPE =
- integral (level of free convection
to level where parcel becomes neutrally buoyant)
[ (T_parcel - T_ambient) R d(ln p) ]
where
R = universal gas constant for dry air
p = pressure
ln = natural logarithm
T_parcel = temperature of the parcel for which you calculate CAPE
T_ambient = temperature of the ambient air at pressure p
There are many variations of computing CAPE such as virtual temp.
adjustments, and initial parcel properties (surface parcel,
layer-averaged parcel etc.)
I am exhausted, bye,
Harald
--
------------------------------------------------------
Harald Richter
Postdoctoral Research Associate
Department of Earth and Atmospheric Sciences
State University of New York at Albany
1400 Washington Avenue
Albany, NY 12222
phone: (518) 442-4273 fax: (518) 442-4494
spatz at atmos.albany.edu
http://www.atmos.albany.edu/facstaff/spatz/spatz.html
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016
Date: Fri, 17 Dec 1999 08:50:21 +1000
From: Anthony Cornelius [cyclone at flatrate.net.au]
X-Mailer: Mozilla 4.6 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: Re: aus-wx: Explain please... :)
Sender: aussie-weather-approval at world.std.com
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Hi Les and Leslie :)
"Leslie R. Lemon" wrote:
>
> Les (UK):
>
> > btw I've got a Skew-T dating from 1960, I know CAPE is high but can
> someone tell
> > me how high by showing me the math(s)???
Did you want to scan this? I can then plot it manually, and give you a
fairly 'accurate estimate' - well, within 10% normally. If the figures
are easily legible, I can chuck them into my CAPE proggy and calculate
the exact figure too.
> Let me take a shot at this via e-mail. It is the integral of the of the dot
> product of the storm relative wind vector and the horizontal vorticity
> vector with respect to height over the height range of 0 to Z.
Actually - I think this is the SRH equation (?)
The equation I've always learnt is the 'looks easy, but is bloody
complicated' version:
CAPE = g x of - Tv(z) all over Tv(z) with respect to height (z)
Where g = gravitational something
LFC = Level of Free Convection
EL = Equilibrium Level
Tv = Virtual Temperature
Where Tv = (T/1 - (e/p(1-0.622))
When T = Temperature
e = vapour pressure
p = atmospheric pressure
Where e = (es - Ap(T-Tw)
When es = saturated vapour pressure
A = some ventilation constant
Tw = Wetbulb Temperature
After you substitute everything in, you get a very messy equation that
will take me 10 mins to type out!
I've often tried to calculate this for myself, but failed because:
- I don't have any values for 'A'
- I'm not sure how to calculate e or es without at least one of them
If anyone can assist me with the above, it'd be VERY much appreciated.
This is something I got from reading about the CAPE equation in a book -
and then I went through other books to find the missing equations and
variables - so if I've made a mistake somewhere along the way...please
tell me!
As I said though - the easiest thing is to manually plot the skew-t, and
derive an estimate of CAPE :) So if you want to scan it (or even post
it!) to me Les, I can try and work it out for you.
--
Anthony Cornelius
Queensland Coordinator of the Australian Severe Weather Association
(ASWA)
(07) 3390 4812
14 Kinsella St
Belmont, Brisbane
QLD, 4153
Please report severe thunderstorms on our Queensland severe thunderstorm
reporting line on (07) 3390 4218 or by going to our homepage at
http://www.severeweather.asn.au
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017
Date: Thu, 16 Dec 1999 23:10:14 +0000
From: Les Crossan [les.crossan at virgin.net]
Organization: Cosmic EuroCon - note all times in GMT
X-Mailer: Mozilla 4.5 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: Re: aus-wx: Explain please... :)
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
"Leslie R. Lemon" wrote:
It is the integral of the of the dot product of the storm relative wind vector
and the horizontal vorticity vector with respect to height over the height
range of 0 to Z.
>
It does - now please send us the formula (:
Les(UK)
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018
Date: Fri, 17 Dec 1999 09:15:22 +1000
From: Anthony Cornelius [cyclone at flatrate.net.au]
X-Mailer: Mozilla 4.6 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: Tropical CAPE's (was) Re: US/AU Conditions (was) Re: aus-wx: Nine
network anals &progs
Sender: aussie-weather-approval at world.std.com
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Hi Les,
"Leslie R. Lemon" wrote:
>
> Paul and Anthony and all:
>
> Owing to the much warmer air (and moist air) aloft, tropical CAPEs are, I
> believe, rather low (a few hundred or even less). Keep in mind that CAPE
> is the integral of the buoyant energy, the temperature difference between
> the environment and the rising parcel (moist adiabatic). As you know the
> LI's in the tropics are usually quite modest (~+1 to -3). Once again that
> is because the temperatures at 500 mb are warm, "substantially" warmer than
> in mid-latitudes. This, in turn, accounts for the low updraft vertical
> velocities and smaller dropsize distributions typically found in tropical
> convection. Moreover, environmental shear is low in the topics, thus
> updraft augmentation due to environmental shear is not available, either.
> This is as I understand it.
AU tropical CAPE's might be higher than say the usual tropical CAPE's
then? Darwin frequently has CAPE's of 1000-2000 at 9am, with LI's
between -3 and -6. But this is just one area, although I suspect many
tropical regions around there will receive CAPE's of this magnitude.
Again, lack of information in this area means one can only speculate in
this field for Australia.
--
Anthony Cornelius
Queensland Coordinator of the Australian Severe Weather Association
(ASWA)
(07) 3390 4812
14 Kinsella St
Belmont, Brisbane
QLD, 4153
Please report severe thunderstorms on our Queensland severe thunderstorm
reporting line on (07) 3390 4218 or by going to our homepage at
http://www.severeweather.asn.au
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019
Date: Thu, 16 Dec 1999 23:34:05 +0000
From: Les Crossan [les.crossan at virgin.net]
Organization: Cosmic EuroCon - note all times in GMT
X-Mailer: Mozilla 4.5 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: Re: aus-wx: SRH and CAPE
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
Harald Richter wrote:
> For the hardliners,
not really seeing if my maths is up to it....
> SRH = integral (from 0 to h) [ k * ((V-c) x dV/dz)] dz
>
> where
>
> k = vertical unit vector
> V = total velocity vector of the ambient flow
> c = motion vector of the storm (whatever that means)
> dV/dz = vertical shear vector
> z = vertical coordinate
> h = commonly the level of free convection (~ 3km)
>
It Is, It Is!!!! Brain still functions!
>
>
> CAPE = - integral (level of free convection
> to level where parcel becomes neutrally buoyant)
>
> [ (T_parcel - T_ambient) R d(ln p) ]
> where
>
> R = universal gas constant for dry air
> p = pressure
> ln = natural logarithm
> T_parcel = temperature of the parcel for which you calculate CAPE
> T_ambient = temperature of the ambient air at pressure p
>
> There are many variations of computing CAPE such as virtual temp.
> adjustments, and initial parcel properties (surface parcel,
> layer-averaged parcel etc.)
Nice one..... thanx everyone, now to plot... substitute... calculate. Me, I'm
gonna use a spreadsheet on this, thanx again (:
Les
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020
Date: Fri, 17 Dec 1999 09:23:54 -0800
From: Lindsay [writer at lisp.com.au]
X-Mailer: Mozilla 3.0 (Win16; I)
To: aussie-weather at world.std.com
Subject: aus-wx: Powder snow
Sender: aussie-weather-approval at world.std.com
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For Michael Scollay and others in the "snow know"
I was reading about The Rocky Mountains snow fields (Colorado) and the
amount of powder snow they receive there. The article said that
Australia rarely gets more than a few centimetres of powder snow over a
hard base.
Is this true?
I thought that at times after a fresh dump it could be quite powdery for
a day or so...just wondering.
Lindsay Pearce
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021
Date: Thu, 16 Dec 1999 10:00:49 -0800
From: Lindsay [writer at lisp.com.au]
X-Mailer: Mozilla 3.0 (Win16; I)
To: aussie-weather at world.std.com
Subject: Re: aus-wx: TC John has made land...........
Sender: aussie-weather-approval at world.std.com
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Whereabouts are you again Leslie? Altitude there? What's your typical
maximum and minimum for winter?
Balmy here in the mountains, haven't checked the thermometer, but I'd
say around 18C
(65F). Moderate NW winds with high pre-frontal cloud.
Lindsay Pearce
Leslie R. Lemon wrote:
>
> What a difference a hemisphere will make! We had 7.5 cm of snow last night
> and it is only about 3 C here now after a day of abundant sunshine but with
> strong winds.
>
> > > Exmouth climbed up to 40 degrees today. A pretty impressive figure
> being
> > so
> > > close to the cyclone. Most likely due to the downslope winds around the
> > SE
> > > side of TC John. MH
>
> Les
> ************************
> Leslie R. Lemon
> Radar, Severe Storms, & Research Meteorologist
> Phone: 816-373-3533
> E-Mail: lrlemon at compuserve.com
>
> essage text written by INTERNET:aussie-weather at world.std.com
> >> Exmouth climbed up to 40 degrees today. A pretty impressive figure being
> so
> > close to the cyclone. Most likely due to the downslope winds around the
> SE
> > side of TC John. MH<
>
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022
From: Blair Trewin [blair at met.Unimelb.EDU.AU]
Subject: aus-wx: Heavy rain in various parts of the country...
To: aussie-weather at world.std.com (Aussie Weather)
Date: Fri, 17 Dec 1999 11:07:41 +1100 (EST)
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A few interesting reports from various bits of the country:
- numerous falls over 50mm in the NE Vic/SE NSW highlands (e.g.
91 at Crackenback, 87 at Mitta Mitta, and a few other sites in the
60s). Also widespread 10-40mm in Gippsland (and presumably in the
Melbourne catchments, although those need follow-up rains and there's
no sign that they'll get them).
- 103mm at Wilcannia. I'm not 100% certain that this is legit (White
Cliffs, the nearest other site, got 8), but it's entirely possible
if there were storms about. This would be their third-highest daily
fall in a 116-year record if confirmed.
- 46mm at Alice Springs, which must go close to doubling their total
for the year. Also 41mm at Giles (making a two-day total of 81).
Also 18mm at Birdsville. Moomba (NE SA) had 48mm to 4 p.m. yesterday,
but didn't report this morning. (This area of rain covers a region
which has been very dry this year, with pockets having had only about
30-40mm for the year to date).
No reports yet from WA or NT (apart from Alice) because of the time
difference. Ilsa might produce something interesting if any of its
rainbands managed to end up on top of a gauge (the system itself
looks like it will hit absolutely nothing, other than providing some
extra water to anyone who feels like emulating the wanderings of
Mr. Bogucki).
Queensland looks like it might get some substantial rain over the
next two days (which is normally the only way that Victoria avoids
losing at the Gabba, so I can't be too upset :-). Also pretty cool
over the SE (Melbourne is not forecast to get into 548-plus thicknesses
until Monday night).
Blair Trewin
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023
From: Blair Trewin [blair at met.Unimelb.EDU.AU]
Subject: aus-wx: Seriously weird forecasts on the web
To: aussie-weather at world.std.com (Aussie Weather)
Date: Fri, 17 Dec 1999 11:44:48 +1100 (EST)
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If you want a bit of light entertainment, go to:
http://www.bbc.co.uk/weather/
and select the 5-day forecast for Canberra. I'll believe a max of
4 when I see it!
(The UK itself is worth keeping an eye on over the weekend - looks
set to turn very cold, with possible snow and very low minima in the
frost pockets, especially in Scotland).
Blair Trewin
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024
From: "Michael Thompson" [michaelt at ozemail.com.au]
To: [aussie-weather at world.std.com]
Subject: Re: aus-wx: Powder snow
Date: Fri, 17 Dec 1999 11:48:14 +1100
X-Mailer: Microsoft Outlook Express 5.00.2014.211
Sender: aussie-weather-approval at world.std.com
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I have never skied in my life, but I think powder is a product of low
humidity - low temperatures, whilst Aussie snow tends to be in very humid
environments with temps often just under 0C , which equals large flakes.
Michael
> For Michael Scollay and others in the "snow know"
>
>
> I was reading about The Rocky Mountains snow fields (Colorado) and the
> amount of powder snow they receive there. The article said that
> Australia rarely gets more than a few centimetres of powder snow over a
> hard base.
>
> Is this true?
>
> I thought that at times after a fresh dump it could be quite powdery for
> a day or so...just wondering.
>
>
> Lindsay Pearce
>
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025
Date: Fri, 17 Dec 1999 12:31:32 +1100
From: Michael Scollay [michael.scollay at telstra.com.au]
Organization: Telstra Strategy & Research
X-Mailer: Mozilla 4.5 [en] (X11; I; SunOS 5.5.1 sun4m)
X-Accept-Language: en
To: aussie-weather at world.std.com
Subject: Re: aus-wx: Powder snow
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
Lindsay wrote:
>
> For Michael Scollay and others in the "snow know"
>
> I was reading about The Rocky Mountains snow fields (Colorado)
> and the amount of powder snow they receive there. The article
> said that Australia rarely gets more than a few centimetres
> of powder snow over a hard base.
>
> Is this true?
>
> I thought that at times after a fresh dump it could be quite
> powdery for a day or so...just wondering.
First of all, the author of that arctical is talking off
the top of his hat with a load of crap. I'll take him out
on the main range almost any day in July/August and laugh
at him/her buried in Aussie powder over his head but with
one qualification - the conditions have got to be spot on.
Secondly, I've skiied "powder" in Colorado, Utah and France.
There's nothing like the lightness of Utah dry snow which
is the other name for "powder" with its huge lightly-packed
classic snow-crystaline structure. Now that is a rare sight
in Australia as our dry snow tends to be more tightly
packed with crystals not quite as large.
I could describe more (favourite subject) later...
Michael Scollay mailto:michael.scollay at telstra.com.au
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026
From: "weatherhead" [weatherhead at ozemail.com.au]
To: [aussie-weather at world.std.com]
Subject: Re: aus-wx: Seriously weird forecasts on the web
Date: Fri, 17 Dec 1999 12:38:45 +1100
X-Mailer: Microsoft Outlook Express 5.00.2615.200
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Hey
Actually I am unsure what year it was ( I think it was Christmas-New Year
97/98 but i am probably wrong) that their was a severe cold snap in the UK
particularly Scotland. Upward of 40 people died and power was cut for around
three weeks. I had a friend who was staying there for 6 weeks and didn't go
outside for four. He is back there again this year and the cold seems to be
following him.
Daniel Weatherhead
----- Original Message -----
From: Blair Trewin [blair at met.Unimelb.EDU.AU]
To: Aussie Weather [aussie-weather at world.std.com]
Sent: Friday, December 17, 1999 11:44 AM
Subject: aus-wx: Seriously weird forecasts on the web
>
> (The UK itself is worth keeping an eye on over the weekend - looks
> set to turn very cold, with possible snow and very low minima in the
> frost pockets, especially in Scotland).
>
> Blair Trewin
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027
From: Blair Trewin [blair at met.Unimelb.EDU.AU]
Subject: Re: aus-wx: Seriously weird forecasts on the web
To: aussie-weather at world.std.com
Date: Fri, 17 Dec 1999 13:26:45 +1100 (EST)
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>
> Hey
> Actually I am unsure what year it was ( I think it was Christmas-New Year
> 97/98 but i am probably wrong) that their was a severe cold snap in the UK
> particularly Scotland. Upward of 40 people died and power was cut for around
> three weeks. I had a friend who was staying there for 6 weeks and didn't go
> outside for four. He is back there again this year and the cold seems to be
> following him.
95/6 actually - and this situation seems to be developing similarly
at this stage.
Blair Trewin
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028
Date: Fri, 17 Dec 1999 12:47:32 -0800
From: Lindsay [writer at lisp.com.au]
X-Mailer: Mozilla 3.0 (Win16; I)
To: aussie-weather at world.std.com
Subject: aus-wx: Great Britian Minima
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
What sort of low temps do they get in these cold outbreaks? What sort of
wind chills as well?
Lindsay P.
Blair Trewin wrote:
>
> >
> > Hey
> > Actually I am unsure what year it was ( I think it was Christmas-New Year
> > 97/98 but i am probably wrong) that their was a severe cold snap in the UK
> > particularly Scotland. Upward of 40 people died and power was cut for around
> > three weeks. I had a friend who was staying there for 6 weeks and didn't go
> > outside for four. He is back there again this year and the cold seems to be
> > following him.
>
> 95/6 actually - and this situation seems to be developing similarly
> at this stage.
>
> Blair Trewin
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029
Date: Fri, 17 Dec 1999 12:42:01 -0800
From: Lindsay [writer at lisp.com.au]
X-Mailer: Mozilla 3.0 (Win16; I)
To: aussie-weather at world.std.com
Subject: aus-wx: UK weather
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Interesting Blair, yes i will keep an eye on the British weather. I've
got a friend near the Wales border.
Lindsay Pearce
Blair Trewin wrote:
>
> If you want a bit of light entertainment, go to:
>
> http://www.bbc.co.uk/weather/
>
> and select the 5-day forecast for Canberra. I'll believe a max of
> 4 when I see it!
>
> (The UK itself is worth keeping an eye on over the weekend - looks
> set to turn very cold, with possible snow and very low minima in the
> frost pockets, especially in Scotland).
>
> Blair Trewin
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030
Date: Fri, 17 Dec 1999 10:30:13 -0800
From: Lindsay [writer at lisp.com.au]
X-Mailer: Mozilla 3.0 (Win16; I)
To: aussie-weather at world.std.com
Subject: Re: aus-wx: Guyra info
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
Thanks Blair,
Still good stuff though, even without your paper. I plan to do some good
snow chases in my area ( Blackheath - Lithgow - Oberon -
Jenolan/Shooters Hill.) next season as I now have a new car and new
camera. So here's hoping for some decent snow, last year was quite
alright.
Linsay Pearce
Blair Trewin wrote:
>
> I can't find my piece of paper with the mean number of snow-days per
> year for various Australian stations, but seem to recall that Guyra
> was somewhere in the 2-3 range (by way of comparison, Canberra,
> Bathurst and Armidale are all in the 1-2 range, Orange is around 6,
> Oberon is around 15).
>
> The mean minimum in July (-1.0) is actually pretty unexceptional
> by New England standards. The site looks pretty good (over grass, no
> buildings or carparks nearby - which are the bane of most sites in
> the region) so I can only presume that local topography is responsible.
> Given that Woolbrook, 400 metres lower, has a July mean minimum of
> -1.4 (and has recorded -14.5), one would expect that a suitably
> sheltered rural valley site at Guyra's altitude (if any exist) might
> get down around -3 or -4.
>
> Blair Trewin
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031
Date: Fri, 17 Dec 1999 12:44:59 -0800
From: Lindsay [writer at lisp.com.au]
X-Mailer: Mozilla 3.0 (Win16; I)
To: aussie-weather at world.std.com
Subject: Re: aus-wx: Powder snow
Sender: aussie-weather-approval at world.std.com
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That's what prompted me to send my email. I recall you saying there was
some great days skiing last season, powder etc. Its annoying when such
articles go to print (City Weekly was the magazine) as I wonder where
the author got such information...Hmmm
Lindsay P.
Michael Scollay wrote:
>
> Lindsay wrote:
> >
> > For Michael Scollay and others in the "snow know"
> >
> > I was reading about The Rocky Mountains snow fields (Colorado)
> > and the amount of powder snow they receive there. The article
> > said that Australia rarely gets more than a few centimetres
> > of powder snow over a hard base.
> >
> > Is this true?
> >
> > I thought that at times after a fresh dump it could be quite
> > powdery for a day or so...just wondering.
>
> First of all, the author of that arctical is talking off
> the top of his hat with a load of crap. I'll take him out
> on the main range almost any day in July/August and laugh
> at him/her buried in Aussie powder over his head but with
> one qualification - the conditions have got to be spot on.
>
> Secondly, I've skiied "powder" in Colorado, Utah and France.
> There's nothing like the lightness of Utah dry snow which
> is the other name for "powder" with its huge lightly-packed
> classic snow-crystaline structure. Now that is a rare sight
> in Australia as our dry snow tends to be more tightly
> packed with crystals not quite as large.
>
> I could describe more (favourite subject) later...
>
> Michael Scollay mailto:michael.scollay at telstra.com.au
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032
From: Blair Trewin [blair at met.Unimelb.EDU.AU]
Subject: Re: aus-wx: Great Britian Minima
To: aussie-weather at world.std.com
Date: Fri, 17 Dec 1999 14:09:46 +1100 (EST)
X-Mailer: ELM [version 2.4 PL23]
Sender: aussie-weather-approval at world.std.com
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>
> What sort of low temps do they get in these cold outbreaks? What sort of
> wind chills as well?
>
>
> Lindsay P.
Don't know about windchills. The UK record low is -27.2, set on three
separate occasions, twice at Braemar (once in the late 19th century
and once in 1982) and once at Altnaharra (1995). All of these are in
Scotland. The 1981/82 cold spell also saw readings around -25/-26 in
pockets of England near the Welsh border (Shawbury, I think).
All of these readings are highly topography-dependent and were
recorded in sheltered valleys. It would be highly unusual to get
below -10 near the coast. -10 also appears to be about the lower
bound if there is no snow cover.
(I lived in Winchester, which is a real frost hollow, in 1989. This
was a very mild year - it didn't snow once - but we got to see the
influence of topography and urbanisation on minimum temperatures, in
all its glory, in a remarkable anticyclonic spell in November and
early December during which no precipitation fell for a month.
Running on some of the early mornings and climbing through the
inversion out of the valley - or entering the built-up area, whose
boundary was very sharp - sometimes felt like stepping in front of
the heater - I'd estimate some of the temperature changes at 5-7 C
over 100 metres horizontal distance. On the coldest mornings it would
range from near 0 C on the ridges to -10 C on the valley floor).
Blair Trewin
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033
From: Paul.Mossman at DWNNICH.OCA.nt.gov.au
To: " - *aussie-weather at world.std.com" [aussie-weather at world.std.com]
Subject: aus-wx: Great Storm..........
Date: Fri, 17 Dec 1999 13:10:49 +0930
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Howdy all.
Great storm is hitting here at the moment - bucketing down & nice lightning
etc.
Great big warm rain drops ........feel like dancin in the street.
Paul at darwin
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034
X-Mailer: Microsoft Outlook Express Macintosh Edition - 4.5 (0410)
Date: Fri, 17 Dec 1999 14:58:52 +1100
Subject: Re: aus-wx: Nine network anals & progs
From: "Mark Hardy" [mhardy at magna.com.au]
To: aussie-weather at world.std.com
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
Les
I was fortunate enough to take a trip in the US earlier this year and
visited several TV stations including The Weather Channel and The Weather
Network. I was struck by the capability of the presenters and the level of
support they receive with assistant mets and equipment.
I was also able to see how seriously weather cripples the country.
Consequently weather in the US is a serious business and it is easy to see
how The Weather Channel has become a Top 3 channel on Pay TV.
In contrast weather rarely has a comparable impact on people and industry
here in Australia. This in part explains why media coverage of weather here
is pretty basic. In fact places such as Phoenix Arizona and San Diego offer
pretty comparable TV weather coverage to Australian TV. It is also these
areas where the presenter is more likely to be a local personality rather
than a meteorologist (which is the norm in the east). In the SW the weather
is more moderate and so it ranks less importance in peoples lives.
But the quality of presentation produced by The Weather Channel is
fantastic. They achieve the right balance between technical detail and
news/entertainment value. Sydney and Brisbane TV stations in particular
could certainly take a lot of pointers from these guys.
_____________________________________________________
Mark Hardy.
The Weather Company Pty. Ltd.
Level 2, 7 West Street, North Sydney 2060
Ph (02) 9955 7704. Fax (02) 9955 1536.
Mobile 0414 642 739
email: mhardy at theweather.com.au
_____________________________________________________
----------
>From: "Leslie R. Lemon"
>To: "INTERNET:aussie-weather at world.std.com"
>Subject: Re: aus-wx: Nine network anals & progs
>Date: Thu, 16 Dec 1999 2:11 AM
>
> Mark:
>
>> The reason some media are inaccurate is not the fault of BoM. It's
> basically
>> because weather is not a high priority in their programming.
>
> This is fascinating, the differences in culture and climate. Here in the
> US weather is THE MOST important factor when it comes to news and the
> viewing audience, at least in most parts of this country. That is why TV
> stations will spend $600K US or more for a weather radar (even when they
> also have a drop on NEXRAD) as well as another $500K or more for graphics
> computers, the on-air set, other instrumentation, several fully equipped
> chase vehicles, helicopters, and their own organized spotter networks, and
> satellite down-links. This does not even include the salaries (which can
> exceed $1M US) for the on-air meteorologists and other weather staff.
> Here, even in the private sector, weather is very big business. And they
> must get that weather right!
>
> But be encouraged, it has not always been that way. Thirty or forty years
> ago it was far different here. There were no (or at least very very few)
> on-air meteorologists. The 'equipment' they had was a teletype and a glass
> map that the weathercaster stood behind and wrote temperatures *backwards*
> using white markers [S]! LOL
>
> Les
>
> ************************
> Leslie R. Lemon
> Radar, Severe Storms, & Research Meteorologist
> Phone: 816-373-3533
> E-Mail: lrlemon at compuserve.com
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035
Date: Fri, 17 Dec 1999 18:25:19 +1000
From: Anthony Cornelius [cyclone at flatrate.net.au]
X-Mailer: Mozilla 4.6 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: Re: aus-wx: SRH and CAPE
Sender: aussie-weather-approval at world.std.com
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Hi Harald and all,
Just when people thought it was safe to come back again, I'm
recommencing the CAPE/SRH thread! :)
Harald Richter wrote:
>
> Hi Anthony (and eavesdropers),
>
> I enjoyed your discussion of SRH/CAPE. One
> conclusion that I have arrived at is the *sensitivity*
> of these two 'discriminators' to a number of things.
> You can easily produce a 10,000+ CAPE sounding by
> measuring T/Td in a steamy corn field after a weak
> warm shower (this has been done in Western Iowa some months
> back). Then you take that same thermometer/psychrometer, walk
> away from that steamy corn field out into the
> parking lot - your CAPE is down to 3000 J/kg.
> "Representativeness" is another big concern when relating
> CAPE (and SRH) to actual storms. Did the sounding go
> up in the inflow sector of the storm, or was it launched
> through a shallow cold pool on the cool side
> of a boundary along which the storm happened to ride?
> Climatologies that I have seen (I am thinking of Erik Rasmussen's
> 1992 clim.) have convinced me that "standard" CAPE and
> "standard" SRH have no more than *some* value in discriminating
> between supercells and non-supercells.
This is the hardest part about trying to comprehend CAPE, and how it
changes. Many people aren't aware as to how sensative CAPE is to
moisture, especially when DP's start exceeding the low 20's, CAPE will
begin to increase exponentially quite fast after this (providing there
is already CAPE present!) Call me boring - but I find this strand very
intriguing and thought provoking. On the other hand, you also have to
ensure that the parcel of air that you're trying to ascend, is going to
be representative of the lower/surface levels - I think it's refered to
as a TWML? (Thermally Well Mixed Layer) - but I might be thinking of
something else here.
It's one reason why I enjoy going over a selection of skew-ts when I'm
looking at LI/CAPE forecasts for us - I want to see if
a) the DP/temps at the surface are actually attainable
b) is there any dry air aloft that will dilute the CAPE
Here in Brisbane, a W'ly just above the surface will cause DP's to crash
into the single figures, while we swelter at the surface with low-mid 20
DP's.
> The storm motion/circulation itself has a significant
> impact on CAPE/SRH. When a supercell turns right/left, its
> SRH might double or drop to a half.
> Mixing is a player in diluting originally high-CAPE parcels.
You've just grabbed my attention - I don't suppose you could explain to
me how this actually occurs? IE - whena supercell turns right/left -
how its SRH may double, or drop in half. If you want to send this to me
personally so we don't bore too many people, then that's ok :)
> I guess my point is that there's a number of processes
> out there (= where the storms are/should be) that can easily
> double/halve CAPE/SRH values AND storms might "feel"
> CAPE/SRH values vastly different from the ones that we are
> able to compute. Still, until someone (on this list???)
> comes up with something better, CAPE/SRH is it.
You raise a very valid point here, I agree with you.
> Harald
>
> P.S.: My suggestion -- the "Cornelius Index (CI)"
> CI < 0 --> no supercells
> CI > 0 --> supercells
> CI = 1 --> F1 tornado
> CI = 5 --> F5 tornado
> Now that I've done the hard stuff, could you
> (A.) finish off the details, please :)
*LOL* at the index!
I have actually attempted to form my own thunderstorm forecasting index,
but it's extremely difficult really. There's no such thing as a
"perfect index" - but a good index should
a) When the index indicates thunderstorms, there should be thunderstorms
b) When the index doesn't indicate thunderstorms, there should NOT be
thunderstorms
All indicies have failed both of these tasks miserably. I guess a
scaling factor is the most difficult - perhaps one should look at
1) A thunderstorm probability index
2) A thunderstorm improbability index
On the other hand - I should shut up, because I can't develop a better
one!
--
Anthony Cornelius
Queensland Coordinator of the Australian Severe Weather Association
(ASWA)
(07) 3390 4812
14 Kinsella St
Belmont, Brisbane
QLD, 4153
Please report severe thunderstorms on our Queensland severe thunderstorm
reporting line on (07) 3390 4218 or by going to our homepage at
http://www.severeweather.asn.au
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036
Date: Fri, 17 Dec 1999 09:57:07 +0000
From: Les Crossan [les.crossan at virgin.net]
Organization: Cosmic EuroCon - note all times in GMT
X-Mailer: Mozilla 4.5 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: Re: aus-wx: Seriously weird forecasts on the web
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
Blair Trewin wrote:
>
>
> 95/6 actually - and this situation seems to be developing similarly
> at this stage.
>
I wouldn't agree, nobody knows quite how things are developing presently, for
really *cold* weather you need a cold North Sea, a blocking high over Scandinavia
with a SHORT sea track to the UK.
MRF, NOGAPS,AVN and the UKMO models are all diverging, suffice it to say that the
warm / cold battle isn't resolved yet!
Les(UK)
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037
Date: Fri, 17 Dec 1999 10:07:16 +0000
To: aussie-weather at world.std.com
From: Norman Lynagh [lynagh at dial.pipex.com]
Subject: Re: aus-wx: Great Britian Minima
X-Mailer: Turnpike (32) Version 4.00
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In message <385AA164.73FB at lisp.com.au>, Lindsay
writes
>What sort of low temps do they get in these cold outbreaks? What sort of
>wind chills as well?
>
>
>Lindsay P.
>
The really severe cold outbreak mentioned by Blair was in December 1995
(aren't these things always longer ago than you think!). During the
severe spell Glasgow Airport in Scotland recorded the following
temperatures:
Min Max
--- ---
25 Dec -6c +1c
26 Dec -16c -6c
27 Dec -19c -9c
28 Dec -19c -10c
29 Dec -20c -12c
30 Dec -18c +3c
Such severe conditions are very unusual in Glasgow. They occurred with a
snow cover in a calm, anticyclonic situation following an outbreak of
arctic air. Such low temperatures would not occur in windy conditions.
As Blair mentioned, a similar weather situation is developing for this
weekend with a high expected to be centred near the British Isles
following an outbreak of Arctic air. Very low overnight mins are a
certainty but probably not approaching the 1995 values because there is
very little snow cover, at least not in the populated areas.
Severe wind chills do occur every winter from time to time. At 0600 GMT
today, at the leading edge of the arctic outbreak the automatic weather
station on the summit of Cairngorm (1245 metres) reported a wind of 310
deg 58 knots gusting 71 knots and a temperature of -2.5c. Lerwick, in
the Shetland Islands reported 010 deg 36 knots gusting 50 knots and a
temperature of +1.0c. These conditions can be expected on quite a number
of occasions in an average winter. In particularly severe arctic
outbreaks Lerwick can expect 40-50 knot sustained winds with the
temperature getting down towards -5c. On Cairngorm summit sustained
winds of 70-80 knots are not uncommon with the temperature down to -10c.
Down here in the much more sheltered south of England we occasionally
get down to -10c in calm anticyclonic conditions and to -15c very
rarely. The most severe conditions here are with an easterly wind coming
off the continent with a large high centred over Scandinavia. The most
severe event in recent years was in January 1987 (not so recent
really!). My records show the following:
Min Max Wind Snow depth
--- --- ---- ----------
10 Jan -0.4c +0.6c ENE Force 3-4 Nil
11 Jan -6.9c -3.3c NE Force 2-3 Nil
12 Jan -10.2c -7.1c NE Force 3 1 cm
13 Jan -9.9c -4.0c NE Force 3-4 2 cm
14 Jan -7.0c -3.6c NE Force 4-6 8 cm
15 Jan -4.3c -0.1c NE Force 4-5 7 cm
16 Jan -1.5c +0.4c NE Force 3-4 5 cm
17 Jan -2.3c -1.4c SE Force 1-2 5 cm
18 Jan -3.1c -1.2c SE Force 2 5 cm
19 Jan -3.1c -1.4c SE Force 2 5 cm
20 Jan -1.5c +1.7c Light & var 4 cm
I remember 12th Jan very clearly. After an early snow shower it was a
brilliantly clear sunny day yet the max temp was only -7.1c. The reason
was that a pool of very cold air had moved westwards from Russia. The
1000-500 mb thickness over southern England was below 500 dm. This cold
pool moving across the relatively warm North Sea produced very heavy
snow showers on the eastern coastal fringe of England but these did not
penetrate very far inland.
These conditions are a bit different to what I experienced when I was
working for the BoM in Queensland in the 1960s. I remember that Brisbane
sometimes felt cold in July!
Norman.
===================================================================
Norman Lynagh Weather Consultancy Tel: +44 (0)1494 870220
Chalfont St. Giles E-Mail: lynagh at dial.pipex.com
Buckinghamshire
England
===================================================================
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038
Date: Fri, 17 Dec 1999 10:20:49 +0000
From: Les Crossan [les.crossan at virgin.net]
Organization: Cosmic EuroCon - note all times in GMT
X-Mailer: Mozilla 4.5 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: Re: aus-wx: Great Britian Minima
Sender: aussie-weather-approval at world.std.com
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Blair Trewin wrote:
> >
> > What sort of low temps do they get in these cold outbreaks? What sort of
> > wind chills as well?
> >
Presently there is no *real* cold outbreak, the weather is still Atlantic with
low pressure centres crossing the central UK giving NE long sea track winds in
the north, the Azores high is still in place. For a serious cold spell you
need
(i) a persistant area of high pressure over Scandanavia (blocking high)
(ii) short sea track (Easterly) airmass to the UK - long sea track will give
snow and masses of it but temperatures are higher
(iii) light winds
Wallsend, at 55N 1'30W will then have temperatures down to -10, inland the
temperatures go seriously low. The lowest I've had here in the last 10 years
is -10.2c, on frozen snow.
Braemar (Central Scottish Highlands) has recorded -27.2c in these kind of
conditions - Braemar is surrounded by mountains and is a cold pool. It's also
where the Queen goes for her summer holidays, btw (:
There's masses on this kind of thing at the TORRO website:
http://www.torro.org.uk - look for british temperature extremes!
When you get a 30 knot short sea track easterly your talking brass monkey
time, with a longer sea track you might as well give it up on the east coast
as whiteout conditions can ensue and once the thaw ( reversion to atlantic
weather) comes in days or weeks serious flooding can happen.
The best snow conditions can happen when a polar low tracks down the
relatively warm North Sea - good for snow, soft hail, single cells and
waterspouts / tornadoes (:
And no CAPE in sight!
Les(UK)
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-----------------------jacob at iinet.net.au------------------------------
039
Date: Fri, 17 Dec 1999 10:42:12 +0000
To: aussie-weather at world.std.com
From: Norman Lynagh [lynagh at dial.pipex.com]
Subject: Re: aus-wx: Seriously weird forecasts on the web
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In message <385A08F3.6B5E8A69 at virgin.net>, Les Crossan
writes
>
>
>Blair Trewin wrote:
>
>>
>>
>> 95/6 actually - and this situation seems to be developing similarly
>> at this stage.
>>
>
>I wouldn't agree, nobody knows quite how things are developing presently, for
>really *cold* weather you need a cold North Sea, a blocking high over
>Scandinavia
>with a SHORT sea track to the UK.
>
>MRF, NOGAPS,AVN and the UKMO models are all diverging, suffice it to say that
>the
>warm / cold battle isn't resolved yet!
>
>Les(UK)
>
No Les, Blair is correct. The Dec 1995 severe cold spell, which is the
one Blair is talking about, had considerable similarities to the one
which is developing for this weekend. It occurred under a high which
developed over the British Isles following an arctic outbreak. There was
a low in the north Norwegian Sea and W-SW winds over most of
Scandinavia. One significant difference is that there was much more snow
cover in the 1995 event.
Norman.
===================================================================
Norman Lynagh Weather Consultancy Tel: +44 (0)1494 870220
Chalfont St. Giles E-Mail: lynagh at dial.pipex.com
Buckinghamshire
England
===================================================================
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-----------------------jacob at iinet.net.au------------------------------
040
X-Sender: astroman at mail.chariot.net.au
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Date: Fri, 17 Dec 1999 22:32:00 +1030
To: aussie-weather at world.std.com
From: astroman [astroman at chariot.net.au]
Subject: aus-wx: Snowtown report up and running
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com
Hi all,
letting you all know that the snowtown report is now up on the web at
http://sastorms.virtualave.net/snowtown.html
don't forget to checkout the rest of the pages at
http://sastorms.virtualave.net
thanks for your patience
Andrew Wall
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-----------------------jacob at iinet.net.au------------------------------
041
Date: Fri, 17 Dec 1999 22:16:17 +1000
From: Anthony Cornelius [cyclone at flatrate.net.au]
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To: aussie-weather at world.std.com
Subject: Re: US/AU Conditions (was) Re: aus-wx: Nine network anals &progs
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Hi Leslie and all,
"Leslie R. Lemon" wrote:
>
> Jonty and Anthony:
Interestingly enough, when regression analyses
> have been done, the one parameter which seems to have the greatest
> potential, the best direct correlation and association itself and tornado
> occurrence is the LFC!!! The lower the LFC the greater the potential for
> tornado development in environments that support severe thunderstorms.
> This may be associated with how near the surface vortex stretching (and
> thus amplification due to stretching) becomes important.
This is certainly interesting, would this have something to do with the
fact that it's best if your SRH potential is in the 0-3km area of the
thunderstorm (height)? Meaning that the lower your updraft can really
get going without interference, and tap into that high SRH (if I can use
SRH as a simple way of saying that good shear that is very supercell
inducing), thus allowing to rotate?
I know what I want to say here, but my thoughts on 'paper' are cluttered
and ambigious, I apologise for that. But exactly how does the rotating
updraft work and operating? Once an updraft begins to rotate, how will
it slow down and stop rotating? How long does it take to stop rotating?
I always thought that as an updraft began around the surface, and then
began to rotate, that it'd have a certain degreee of momentum that would
allow the updraft, and ultimately the storm to continue to rotate (to an
extent), through a sizable area of the atmosphere. Obviously, the shear
in the layers above the area of good SRH would need to be somewhat
conductive, or at least supportive of sustained rotation.
Since updrafts of the storm only go up, and good SRH higher in the
atmosphere might cause a section of the storm to rotate, but this
rotation won't travel *down* the updraft, only upwards. Therefore, if
good SRH and LFC co-incided, as the updraft rises (assuming it rises
quickly), it would continue to rotate for a set period of timne.
Of course, the area of SRH is actually along the z plane, versus the LFC
which lies as a horizontal slice.
Hopefully you'll be able to give a better explanation...
--
Anthony Cornelius
Queensland Coordinator of the Australian Severe Weather Association
(ASWA)
(07) 3390 4812
14 Kinsella St
Belmont, Brisbane
QLD, 4153
Please report severe thunderstorms on our Queensland severe thunderstorm
reporting line on (07) 3390 4218 or by going to our homepage at
http://www.severeweather.asn.au
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| Document: 991217.htm
Updated: 22 December 1999 |
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