Date: Tue, 23 May 2000 10:25:49 -0400
From: "Leslie R. Lemon" <lrlemon at compuserve.com>
Subject: Re: aus-wx: the documentary "storm force"
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Michael wrote:

> I have to go with Jimmy on this, I think the landspout term is very
> appropriate in that the mechanisms are similar to a waterspout. Landspout
> means to me - no wall cloud, flat based Cu (even congestus), no
mesocyclone.
> This is different to some non-supercell tornadoes in that they can look
very
> much like a supercell tornado and be formed on inflow - outflow boundary
> associated with often ragged chaotic cloud bases, unlike landspouts.

In the plains of the US and the storm chasing community the following
definitions are used.  "Gustnadoes" are vortices along the tstm gust front
which apparently do not have a connection with the shelf cloud (if there is
one) or with the cloud base updraft above.  (I have some doubt about the
absence of a vertical connection, but, at least, there are no funnels aloft
or cloud base connection visible.)  These vortices are usually F0.

The "gust front tornado" does have a funnel (usually aloft without
condensation cloud to the surface).  But because it does have an obvious
extension to the cloud base above, and with this connection vertical
stretching can amplify the vorticity (spin) of the vortex.  These tornadoes
can be F0 to most often F1.  Remember, many have the misguided idea that
for a 'tornado' to be a tornado, it must have a funnel cloud extending to
the ground.  This is simply wrong.  Normally, even with supercell
tornadoes, the damaging vortex develops at the surface and aloft as a
funnel cloud, and with time the funnel will descend into the surface based
dust and debris cloud.  Sometimes the funnel will never reach the ground,
despite the fact that damage is occurring at the ground for some distance. 
At other times there are funnel fragments intermediate from cloud base to
ground.  But, even though many tornadoes do develop a ground to cloud base
funnel, that is not necessary for a "tornado", defined as a "violently
rotating column of air in contact with the ground and pendent from a
cumulonimbus (or towering cumulus)..

The "landspout" is a tornadic vortex which develops out of pre-existing
"vertical vorticity" in the boundary layer.  In other words, often a
discontinuity exist at the surface such as a gust front that survived the
demise of the parent tstm, a "bubble boundary" or boundary produced by a
large area of tstms, or even a synoptic scale boundary.  Not uncommonly
there is a collision of a moving boundary and a stationery boundary.  At
the point of collision, winds are such that a weak vortex, or several weak
vortices will develop.  If the atmosphere is unstable, cu or towering cu
will develop along the boundary and when the updraft of one of these clouds
phases with one of these cumulus updrafts, vertical stretching occurs,
amplification of rotation, and a "landspout" is borne.  The only visible
connection with the surface is often a "tube" of dust extending vertically
upward to the funnel aloft.  Condensation to the surface does occur but is
relatively rare.  Often, as the towering cumulus grows and matures, the
resulting rainfall and downdraft will lead to the demise of the tornado. 
These tornadoes range in strength from F0 to F2.

Then, of course there are the supercell tornadoes.

Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Tel. 816-373-3533, 816-213-3237
E-Mail: lrlemon at compuserve.com
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 -----------------------jacob at iinet.net.au------------------------------

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Date: Wed, 24 May 2000 00:28:47 +0800
To: <aussie-weather at world.std.com>
From: Ira Fehlberg <jra at upnaway.com>
Subject: aus-wx: Tips on chasing.
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As you may or may not know John & I have been building a new site. So far
part of it is up and i thought if anyones bored (since the wx is pretty
boring around the country atm) and wants a read i have done a page on
chasing tips, its up at
http://www.inflowimages.com/chasetips.html

May the wx improve soon,

Ira Fehlberg

PS btw i have had some problems with my computer and email the last few
weeks so if i havent replied to any important emails please forgive ill get
to them tomorrow i hope, ta again.

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From: "MSC" <cadence at rubix.net.au>
To: "Aussie Weather" <aussie-weather at world.std.com>
Subject: aus-wx: Snow?
Date: Wed, 24 May 2000 08:06:34 +1000
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Can anyone confirm a report of snow on Mt Macedon yesterday?


Jane 

---------------------------------------
Jane ONeill
ASWA - Victoria
http://www.severeweather.asn.au
 
Melbourne Storm Chasers
http://www.rubix.net.au/~cadence
---------------------------------------

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From: "Les Crossan" <les.crossan at virgin.net>
To: <aussie-weather at world.std.com>
Subject: Re: aus-wx: Snow?
Date: Tue, 23 May 2000 22:32:43 +0100
Organization: Cosmic EuroCon - note all times are always GMT
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----- Original Message ----- 
From: MSC <cadence at rubix.net.au>
To: Aussie Weather <aussie-weather at world.std.com>
Sent: Tuesday, May 23, 2000 11:06 PM
Subject: aus-wx: Snow?


> Can anyone confirm a report of snow on Mt Macedon yesterday?

Unfortunatly not (:

Les

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Date: Wed, 24 May 2000 08:38:10 +1000
From: Anthony Cornelius <cyclone at flatrate.net.au>
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Subject: Re: aus-wx: TORNADOES and tornadoes...
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Hi Kevin and all,

Thanks for the interesting discussion so far - I've been enjoying it.

Onto your email (re, a tornado must require a Cb), I'd light to put
forth a few points to you.

Thunderstorms, and Congestus are nearly identical.  More so, if they're
both precipitating.

With our recent lack of weather this season, it granted me the
opportunity to take notice of a few less-exciting things that normally I
wouldn't notice.  And that was the remarkable similarity between our
coastal showers, and thunderstorms.  In one case, a line of showers
coming off the ocean came through during the maximum heat of the day,
and displayed (what I thought to be) multicellular charecteristics. 
There would be dominant showers, dissipating showers, and forming
showers - all developed and dissipated like multicells.  

Many showers that I've observed have displayed these characteristics of
thunderstorms:

- Defininte and organised updraft and downdraft regions
- Shelf clouds/archus clouds
- Scud lowerings/lowered bases
- A "core" so to speak
- A pronounced inflow and outflow region
- Rain feet
- RFB
- Flanking line
- WC (only once, arguably twice - no camera for the probable one)
- Rotation 
- Hail/hail shafts
- Have formed in simila ways to thunderstorms (eg, border range
thunderstorms get pollution nuclei, and convergence from the mountains,
coastal showers get salt nuclei and convergence from the friction
causing the wind to slow down as it approaches the coast).

I could still go on - but essentially, a thunderstorm could simply be
seen as a "very well organised, and usually larger and stronger version
of a shower."  Which would tend to suggest that tornadoes can occur from
showers/CJ's just as they do in Cb's, but of general weaker intensity. 
Perhaps something that might stir a few people up, is my thought that
perhaps to study tornado-producing thunderstorms, we would be better to
study tornado-producing showers as they are a little less complicated
then thunerstorm dynamics.

I also remember having an interesting conversation with Dr Pearce (<g> 
As to not embarrass Matthew too much, Dr Pearce is an IRC "nick") and we
discussed the prospects of a "supercellular" shower.  Which again, would
not be out of the question.  I guess the only debate would be by
definition - but no doubt, showers do rotate.  Perhaps Ira has a little
to say about this with winter frontal systems in WA.

The interesting 'wild card' I throw at you, are these photos from a
rotating lowering on the 21st of April, last year.

http://www.bsch.simplenet.com/anthony/Apr99/1999April21e.jpg
http://www.bsch.simplenet.com/anthony/Apr99/1999April21g.jpg 
'g' is the main rotation area in this lowering, it appears to extend
upwards and has at least some vertical depth.  As this went over - it
was sufficiently strong as to allow my ears to pop, but it was just
'breezy.'

All from a shower...

Kevin Phyland wrote:
<snip all>
-- 
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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From: "Willis, Andrew" <adwillis at bechtel.com>
To: "'aussie-weather at world.std.com'" <aussie-weather at world.std.com>
Subject: RE: aus-wx: Cold outbreak update
Date: Tue, 23 May 2000 15:38:09 -0700
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> Just in case previous model runs didn't get everyone excited enough,
> the 00Z GASP run (just out) has a thickness of 522 over Melbourne on
> Saturday morning...
> 
Hi All

I've been following the cold outbreak discussion with interest.

Can someone describe briefly what a 522 thickness of the 00Z GASP is.

Thanks.
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From: David Jones <D.Jones at bom.gov.au>
To: "Aussie Weather (E-mail)" <aussie-weather at world.std.com>
Subject: aus-wx: progged cold outbreak..
Date: Wed, 24 May 2000 09:05:42 +1000
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Well people.. the latest batch of 12Z progs are in and they are even more
hyped than yesterday. To interpolate/extrapolate the minimum thickness
values for Melbourne/Hobart are,

UK ~528 / ~528 
US ~526 / ~520
GASP ~522 / ~519

As a guide flurries are likely to sea level with thickness values ~526
(provided you have the precipitation happening - which with TOT TOTS of +55
this shouldn't be a problem). Each GPDM very nearly equals 0.5C in average
(pressure) weighted temperature for the 1000 to 500 hPa part of the
atmosphere, so UK, US, GASP suggest snow around Melbourne to about 150m, 0m,
-300m. Of course the models may have it all wrong.... though they first
picked up on this cold outbreak late last week, and have only intensified it
since, so there is hope they are onto something.

Two noteworthy features about the progged outbreak are,
1 - the best is expected to come through at night,
2 - the flow is progged to be between SW and S when the coldest air passes
through. 

The flow is particularly important for Melbourne as flow north of SW tends
to be quite unfavourable for showers at night over Melbourne - from memory
the cold outbreak we had in early June 1994 and Aug 1996 (97?) both had
relatively unfavourable W flow, despite thickness values cold enough for
snow in the city.

As for snow depths, the progs suggest moderate snowfalls at quite high
levels ahead of the Friday front (mostly above ~1500m) - I'ld guess about
5-25cm (with Buller probably getting the least). Behind the front
significant snowfalls will probably be confined to the southern slopes -
meaning Baw Baw, Lake Mt etc. The real limiter with this system will
probably be lack of moisture, as is often the case with cold outbreaks. 

Cheers,

David.

                                                              
Dr David Jones                                               
                                                            
Climate Analysis Section                                   
National Climate Centre                                    
Bureau of Meteorology      Fax      : (+61 3) 9669 4678   
GPO Box 1289K, Melbourne   Ph (work): (+61 3) 9669 4861 
Victoria 3001, Australia   Ph (home): (+61 3) 9898 4425  
email : D.Jones at bom.gov.au                               

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Date: Tue, 23 May 2000 13:26:05 -0700
From: Lindsay <writer at lisp.com.au>
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Subject: Re: aus-wx: Bathurst weather
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G'day Blair and David, wish I could have seen that Bathurst frost,
sounds great.

Interestingly, at the 0800 obs this morning (tuesday) Mount Boyce (A few
k's north of Blackheath for those not familiar with it) was balmy at
around 10.0 with Richmond around 3 and Sydney airport around 10.0. It
was so warm up here.

Lindsay P.

Blair Trewin wrote:
> 
> >
> > HI .
> >
> > Nice extreme frost and fog this morning, looking out my front window and
> > cannot see Mt Panorama at all. Fog covering all of Mountain.. I would
> > say a -3 or -4 last night, still very cold.  Grass very white,, looks
> > like snow, but no that is for later in week by the sounds of it. Lets
> > hope we see some snow aound Orange - Oberon areas on Sat - Sun..
> >
> > Dave
> >
> 
> -6.2, the second-coldest May minimum in the records I have digitised
> (1921 to present; note that this doesn't match the Bureau web site
> which only covers the post-1966 period there).
> 
> This seems to have been the most relatively extreme observation, but
> I was also impressed by Armidale (-6), Forbes Airport (-4),
> Tumbarumba (-6), Cooma (-7) and Rutherglen (-4).
> 
> There is clearly a substantial inversion (and the upper-level winds
> make a big difference too); Charlotte Pass only got down to 1.
> 
> Blair Trewin
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Date: Tue, 23 May 2000 19:56:28 -0400
From: "Leslie R. Lemon" <lrlemon at compuserve.com>
Subject: aus-wx: progged cold outbreak..
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Dr. Jones wrote:

> As for snow depths, the progs suggest moderate snowfalls at quite high
> levels ahead of the Friday front (mostly above ~1500m) - I'ld guess about
> 5-25cm (with Buller probably getting the least). Behind the front
> significant snowfalls will probably be confined to the southern slopes -
> meaning Baw Baw, Lake Mt etc. The real limiter with this system will
> probably be lack of moisture, as is often the case with cold outbreaks. 

Just wanted to tell all you folks that I am cheering for you!  I really
would like to see heaps of snow on all of you!!  <S>  I do love snow
myself....and we never get enough here.

Good luck!!

Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Tel. 816-373-3533, 816-213-3237
E-Mail: lrlemon at compuserve.com
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Date: Tue, 23 May 2000 20:23:22 -0400
From: "Leslie R. Lemon" <lrlemon at compuserve.com>
Subject: Re: aus-wx: TORNADOES and tornadoes...
To: "INTERNET:aussie-weather at world.std.com" <aussie-weather at world.std.com>
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Anthony wrote:

> With our recent lack of weather this season, it granted me the
> opportunity to take notice of a few less-exciting things that normally I
> wouldn't notice.  And that was the remarkable similarity between our
> coastal showers, and thunderstorms.  In one case, a line of showers
> coming off the ocean came through during the maximum heat of the day,
> and displayed (what I thought to be) multicellular characteristics. 
> There would be dominant showers, dissipating showers, and forming
> showers - all developed and dissipated like multicells.  

Good stuff, Anthoney.  Well, virtually all convection tends to be
multicellular.  We once thought (and I guess some still do) that some
convective storms, e.g., supercells, are single cellular.  That concept was
developed from poor resolution radar.  Visually I believe we have always
known convection was, seemingly, by its very nature, multicellular.  

Obviously the discriminator between thunderstorms and showers is what??? 
LOL.  No mystery here; thunder is the discriminator.  But does thunder
change the convection.  No, appears to be the answer.  Lightning depends on
mixed phase precip (ice, graupel, water) and sufficiently strong drafts to
separate charges.  But, indications are that the dynamics of shear and
rotation can occur with only showers.  In fact, we do see the three
dimensional reflectivity distribution (echo overhang and WER, BWER, and
displaced echo top as well as the "wall" or hook echo) in very small storms
that can be argued as showers.  We even see these in tropical convection. 
So, it can be concluded that "showers" can and do produce mesocyclones (or
"misocyclones' < 2km across) and tornadoes.  They have been documented.

Still the mystery goes on.  Why tornadoes?  What does the atmosphere get
from the T that it can't get from somewhere else?

Les
************************
Leslie R. Lemon
Radar, Severe Storms, & Research Meteorologist
Tel. 816-373-3533, 816-213-3237
E-Mail: lrlemon at compuserve.com
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Date: Wed, 24 May 2000 12:56:29 +1000
To: aussie-weather at world.std.com
From: Carl Smith <carls at ace-net.com.au>
Subject: Re: aus-wx: TORNADOES and tornadoes...
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Hi Les.
<snip>
>
>Still the mystery goes on.  Why tornadoes?  What does the atmosphere get
>from the T that it can't get from somewhere else?
>
>Les
>************************
<snip>

An assortment of grasshoppers, spiders, and other bugs and small (or on
occasion large) animals, or various species of fish if over water :-)

Carl.


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Date: Wed, 24 May 2000 06:35:01 -0700
From: Lindsay <writer at lisp.com.au>
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Thanks Leslie,

We are keeping our fingers crossed.


Lindsay Pearce

Leslie R. Lemon wrote:
> 
> Dr. Jones wrote:
> 
> > As for snow depths, the progs suggest moderate snowfalls at quite high
> > levels ahead of the Friday front (mostly above ~1500m) - I'ld guess about
> > 5-25cm (with Buller probably getting the least). Behind the front
> > significant snowfalls will probably be confined to the southern slopes -
> > meaning Baw Baw, Lake Mt etc. The real limiter with this system will
> > probably be lack of moisture, as is often the case with cold outbreaks.
> 
> Just wanted to tell all you folks that I am cheering for you!  I really
> would like to see heaps of snow on all of you!!  <S>  I do love snow
> myself....and we never get enough here.
> 
> Good luck!!
> 
> Les
> ************************
> Leslie R. Lemon
> Radar, Severe Storms, & Research Meteorologist
> Tel. 816-373-3533, 816-213-3237
> E-Mail: lrlemon at compuserve.com
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From: Blair Trewin <blair at met.Unimelb.EDU.AU>
Subject: Re: aus-wx: progged cold outbreak..
To: aussie-weather at world.std.com
Date: Wed, 24 May 2000 14:05:08 +1000 (EST)
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Today's model update (elaborating on what David's already said). Note
that we start to pick up the US model (which goes out to 3 days) now.

GASP

Has sped up considerably from yesterday. Now has the coldest air over 
Melbourne on Friday night and rapid warming during Saturday. 
Thicknesses are still down around 522-523 over Melbourne at 1200 GMT
Friday, and sub-520 over most of Tasmania. They have a low developing
in the Tasman on Saturday, but much weaker and further east than the
other models.

ECMWF

Holds the cold air back a fair bit; on Friday night the sub-528 tongue
is lying along the SA coast from Port Lincoln to Mount Gambier. 
Reading between the lines it seems to be trying to spin up a small low
over SE SA on Friday night, which it then has tracking across Victoria
on Saturday and 'bombing' as it hits the Tasman on Saturday night.
On Saturday night there are sub-528 pools over central Victoria and over 
Tasmania, and the sub-532 zone reaches central NSW. The low deepens
further over the Tasman on Sunday, pushing the flow more southerly
(as opposed to SW), and there is a further cold pool over SA by Monday
(sub-536) moving to north-western NSW by Tuesday. 

UKMO

Low SE of Tasmania on Friday night with the sub-528 tongue covering
most of SW Victoria and SE SA. Develops a low east of Gabo Island on
Saturday night, but not as intense as ECMWF. Not quite as cold on
Saturday as some others, bottoming at 529 in Gippsland.

US

Only goes out to Friday night. Similar to UKMO at that stage but a 
little colder, with thicknesses down below 524 near Mount Gambier.

David's done a pretty good job of summing up the likely implications.
The real wildcard, although I think it is a bit of a longshot, is
the possibility of a small-scale low moving across Victoria on
Saturday accompanied by very cold air. This could bring quite heavy
precipitation with it if it happens. The likelihood of a Tasman low
and the consequent more southerly flow also makes me more optimistic 
for snow in Canberra than I was 24 hours ago. (Canberra often misses
out in SW outbreaks because of the rainshadow from the Brindabellas;
a southerly, or even south-easterly if it's cold enough, is more
favourable).

As for Melbourne, I'd now assess the probabilities as being:

Snow falling in Dandenongs	80-90%
Snow settling in Dandenongs	70%
Snow falling in suburbs		40%
Snow falling in central Melbourne  25%
Snow settling in central Melbourne 10-15%
Major snowfall in Melbourne (10cm+)  5%

(for the last of these to happen, the most favourable scenario would
be a combination of the ECMWF's potential mesoscale low and the 
slightly colder air of GASP)

The higher-resolution local models (LAPS, MESOLAPS) will start to become
available tomorrow, which will add a further element of interest.

Blair Trewin

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From: Blair Trewin <blair at met.Unimelb.EDU.AU>
Subject: aus-wx: Mild in Tasmania - definitely not a prelude...
To: aussie-weather at world.std.com (Aussie Weather)
Date: Wed, 24 May 2000 14:49:11 +1000 (EST)
X-Mailer: ELM [version 2.5 PL2]
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In amongst all the excitement predicted, Hobart has had its second-
warmest May night on record (14.6), and its warmest for so late in
autumn.

Blair Trewin
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X-Sender: carls at ford.ace-net.com.au
Date: Wed, 24 May 2000 15:34:38 +1000
To: aussie-weather at world.std.com
From: Carl Smith <carls at ace-net.com.au>
Subject: Re: aus-wx: Mild in Tasmania - definitely not a prelude...
Sender: aussie-weather-approval at world.std.com
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Hi Blair.

>In amongst all the excitement predicted, Hobart has had its second-
>warmest May night on record (14.6), and its warmest for so late in
>autumn.
>
>Blair Trewin

Having lived in Hobart in the past, let me say that in my experience warm
nights often precede snowfalls.

The older locals down there also say that unusually warm weather is a sign
of approaching snow.

Carl.



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X-Sender: mm_de at postoffice.utas.edu.au
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Date: Wed, 24 May 2000 16:17:24 +1000
To: aussie-weather at world.std.com
From: Miguel de Salas <mm_de at postoffice.utas.edu.au>
Subject: Re: aus-wx: Mild in Tasmania - definitely not a prelude...
Sender: aussie-weather-approval at world.std.com
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At 03:34 PM 24-05-2000 +1000, you wrote:
>Hi Blair.
>
>>In amongst all the excitement predicted, Hobart has had its second-
>>warmest May night on record (14.6), and its warmest for so late in
>>autumn.
>>
>>Blair Trewin
>
>Having lived in Hobart in the past, let me say that in my experience warm
>nights often precede snowfalls.
>
>The older locals down there also say that unusually warm weather is a sign
>of approaching snow.
>
>Carl.

>From a Hobartian's point of view, higher latitude highs, which bring in
warm wind from the NW, usually always precede colder, SW or S air.

Miguel de Salas

 School of Plant Science,
 University of Tasmania,
 PO Box 252-55, Sandy Bay, Hobart
 Tasmania, Australia, 7001.

mailto://mm_de at postoffice.utas.edu.au

My Moths Page:
http://members.xoom.com/migueldes/moths/moths.html
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Date: Wed, 24 May 2000 10:00:27 -0700
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: progged cold outbreak..
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com

Hi all,

Which could possibly mean some decent snow for us in the Upper Blue
Mountains as this is one of the best directions for us. 

Here's hoping.

Lindsay

Blair wrote:

> The likelihood of a Tasman low
> and the consequent more southerly flow also makes me more optimistic
> for snow in Canberra than I was 24 hours ago. (Canberra often misses
> out in SW outbreaks because of the rainshadow from the Brindabellas;
> a southerly, or even south-easterly if it's cold enough, is more
> favourable).
> 
> As for Melbourne, I'd now assess the probabilities as being:
> 
> Snow falling in Dandenongs      80-90%
> Snow settling in Dandenongs     70%
> Snow falling in suburbs         40%
> Snow falling in central Melbourne  25%
> Snow settling in central Melbourne 10-15%
> Major snowfall in Melbourne (10cm+)  5%
> 
> (for the last of these to happen, the most favourable scenario would
> be a combination of the ECMWF's potential mesoscale low and the
> slightly colder air of GASP)
> 
> The higher-resolution local models (LAPS, MESOLAPS) will start to become
> available tomorrow, which will add a further element of interest.
> 
> Blair Trewin
> 
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X-Sender: jdeguara at pop.ihug.com.au
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Date: Wed, 24 May 2000 17:11:41 +1000
To: aussie-weather at world.std.com
From: Jimmy Deguara <jdeguara at ihug.com.au>
Subject: Re: aus-wx: TORNADOES and tornadoes...
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com

I agree with your observations Anthony on the multicellular concept. It is 
amazing how much you learn through observations over the years.

Jimmy Deguara



At 08:38 24/05/00 +1000, you wrote:
>Hi Kevin and all,
>
>Thanks for the interesting discussion so far - I've been enjoying it.
>
>Onto your email (re, a tornado must require a Cb), I'd light to put
>forth a few points to you.
>
>Thunderstorms, and Congestus are nearly identical.  More so, if they're
>both precipitating.
>
>With our recent lack of weather this season, it granted me the
>opportunity to take notice of a few less-exciting things that normally I
>wouldn't notice.  And that was the remarkable similarity between our
>coastal showers, and thunderstorms.  In one case, a line of showers
>coming off the ocean came through during the maximum heat of the day,
>and displayed (what I thought to be) multicellular charecteristics.
>There would be dominant showers, dissipating showers, and forming
>showers - all developed and dissipated like multicells.
>
>Many showers that I've observed have displayed these characteristics of
>thunderstorms:
>
>- Defininte and organised updraft and downdraft regions
>- Shelf clouds/archus clouds
>- Scud lowerings/lowered bases
>- A "core" so to speak
>- A pronounced inflow and outflow region
>- Rain feet
>- RFB
>- Flanking line
>- WC (only once, arguably twice - no camera for the probable one)
>- Rotation
>- Hail/hail shafts
>- Have formed in simila ways to thunderstorms (eg, border range
>thunderstorms get pollution nuclei, and convergence from the mountains,
>coastal showers get salt nuclei and convergence from the friction
>causing the wind to slow down as it approaches the coast).
>
>I could still go on - but essentially, a thunderstorm could simply be
>seen as a "very well organised, and usually larger and stronger version
>of a shower."  Which would tend to suggest that tornadoes can occur from
>showers/CJ's just as they do in Cb's, but of general weaker intensity.
>Perhaps something that might stir a few people up, is my thought that
>perhaps to study tornado-producing thunderstorms, we would be better to
>study tornado-producing showers as they are a little less complicated
>then thunerstorm dynamics.
>
>I also remember having an interesting conversation with Dr Pearce (<g>
>As to not embarrass Matthew too much, Dr Pearce is an IRC "nick") and we
>discussed the prospects of a "supercellular" shower.  Which again, would
>not be out of the question.  I guess the only debate would be by
>definition - but no doubt, showers do rotate.  Perhaps Ira has a little
>to say about this with winter frontal systems in WA.
>
>The interesting 'wild card' I throw at you, are these photos from a
>rotating lowering on the 21st of April, last year.
>
>http://www.bsch.simplenet.com/anthony/Apr99/1999April21e.jpg
>http://www.bsch.simplenet.com/anthony/Apr99/1999April21g.jpg
>'g' is the main rotation area in this lowering, it appears to extend
>upwards and has at least some vertical depth.  As this went over - it
>was sufficiently strong as to allow my ears to pop, but it was just
>'breezy.'
>
>All from a shower...
>
>Kevin Phyland wrote:
><snip all>
>--
>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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>  -----------------------jacob at iinet.net.au------------------------------

---------------------------------------------------------------------------- 
---------------
Jimmy Deguara
from Schofields, Sydney
President of  Australian Severe Weather Association Inc. (ASWA)
http://severeweather.asn.au
e-mail:  jdeguara at ihug.com.au
homepage with Michael Bath
note new URL
http://australiasevereweather.com/

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Date: Wed, 24 May 2000 17:44:13 +1000
From: Matthew Smith <tornado at bigpond.net.au>
X-Mailer: Mozilla 4.61 [en] (Win98; I)
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To: aussie-weather at world.std.com
Subject: aus-wx: Snow Chase & new email addy
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com

Hi everyone!
A snow chase will probably be on the cards this weekend around the Blue
Mountains. A number of people have expressed interest so far in chasing,
and anyone else who wants to come can ! An overnight stay may also be a
possibility on saturday, to get the most out of this system as we can :)

I am not sure if i will be able to go, I will know in the next day or 2.
But if it still looks good on friday/saturday morning, I recommend
people get together for a bit of  chase.

Also please dont forget about the forecasts on the Sydney Storm Chasers
page, done nightly by Matt Pearce (AKA Proffessor :) , for detailed
forecasts for NSW.
http://www.sydneystormchasers.com/forecasts/index.htm

BTW I now have cable internet access with Telstra, and im loving it
hehehe
New emial is tornado at bigpond.net.au

Matt Smith
http://www.sydneystormchasers.com

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From: "Ben Quinn" <bodie at flatrate.net.au>
To: <aussie-weather at world.std.com>
Subject: aus-wx: SE QLD Rain
Date: Wed, 24 May 2000 18:03:51 +1000
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Hi Everyone,

Some decent rain in SE QLD over the last few days - it rained here (although
mostly drizzle-light/occasionally moderate) all day today, and for most of
the day yesterday.. 40mm in the gauge now - approx. 20mm from overnight last
night, and 20mm during the day today..

Some better falls N and NW of me to 9am this morning, with Beerburrum
scoring 47mm, Eumundi 42mm, Maroochydore 40mm and a hanfull of other statons
recording between 15 and 40mm... a couple of 20-25mm's in the 6 hours from
9am this morning to 3pm today as well..  as usual with this kind of system,
the rain didn't make it very far inland..

AVN is also tipping moderate/heavy rain for us Friday afternoon - with a
band of rain forming over the southern interior of QLD and then quickly
moving offshore overnight Friday..





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From: Blair Trewin <blair at met.Unimelb.EDU.AU>
Subject: Re: aus-wx: Cold outbreak update
To: aussie-weather at world.std.com
Date: Wed, 24 May 2000 18:31:11 +1000 (EST)
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> 
> Hi Blair,
> 
> as a BoM staff memeber, you may be interested in this.
> 
> Radio stations (not TV stations that I know of) have been giving forecasts
> for the weekend, such as;
> 
> "Snow In Ringwood!"
> 
> "Over A Meter This Weekend!" etc etc
> 
> Now, I'm worried about this because of the misleading information - there
> not mentioning that the winds are going to become quite severe and you
> wouldn't like to be caught up in the blizzard that will kick in this
> weekend. Does this make them liable for false reports/neglegent
> reports/unofficial forecasts/etc - ie like the discussion a while back about
> aus-wx people making their own predicitons???
> 
> 
Commercial radio's presentation of weather info is one of my pet
hates (not that I'm exactly alone in that - Rob Gell got stuck into 
them in no uncertain fashion in his talk at the AMOS conference).
I haven't heard the reports you mentioned, but then I haven't listened
to commercial radio in the last 24 hours.

I think you'd have fun trying to sue over a failed forecast, though. 
Even in the world centre of litigation, the US of A, I'm not aware of
any successful cases (the closest was a case which was upheld by a 
lower court but overturned on appeal).

I'd sympathise with the forecasters trying to handle this situation.
Because it's such an extreme event, for most it would be something
they might come across once or twice in a career, and I don't think
anyone is quite believing that what the models tell us is going to
happen is really going to happen. On the one hand you can imagine 
the media frenzy that would ensue if an official Bureau forecast came
out stating a 5% chance of 10cm of snow in Melbourne (one suspects
that, in the media's hands, 5% would become 100% very quickly!); on
the other hand, if there really is a major snowfall in Melbourne,
remote a possibility as it may be, there will certainly be major 
disruption at the very least (although not as much as would be the 
case on a weekday), and the forecasters would be pilloried if they
hadn't picked it. Trying to predict the snow/rain boundary is a very
challenging forecasting problem in many parts of the world, but it's
not one any of our people usually have to deal with in the urban areas.
(To illustrate what can happen, IIRC the forecast for Christchurch 
when they got their huge dump in August 1992 was for snow down to
100 metres - a trivial error, probably equating to 0.5 degrees or so,
but one that made the difference between heavy rain and 20-50cm (can
you remember exact amounts, Ben?) of snow in the city).

Blair Trewin

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From: "Lyle Pakula" <remote at leski.com.au>
To: <aussie-weather at world.std.com>
Subject: Re: aus-wx: Cold outbreak update
Date: Wed, 24 May 2000 19:46:51 +1000
X-Mailer: Microsoft Outlook Express 5.00.2615.200
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Hi Blair,

Wow - I had no idea there was a remote chance of snow in Melbourne (when did
this last happen)? I thought the freezing level was only going to drop to,
at lowest, about 800m????

It's funny you metnion the ChCh example, when I was in NZ last year during
the "Big Dump" some locals were talking about the time when "the sheep were
hoping through the snow all the way along the Cantebury plains, right into
Chch". Hard to imagine snow so close to the ocean.

Cheers, Lyle.




-  - ---==( lyle_pakula at hotmail.com )==--- -  -
     .
    / \  .
   /~~~\/ \ " No Friends On A Powder Day "
  /     \  \
 /       \  \





----- Original Message -----
From: Blair Trewin <blair at met.Unimelb.EDU.AU>
To: <aussie-weather at world.std.com>
Sent: Wednesday, May 24, 2000 6:31 PM
Subject: Re: aus-wx: Cold outbreak update


> >
> > Hi Blair,
> >
> > as a BoM staff memeber, you may be interested in this.
> >
> > Radio stations (not TV stations that I know of) have been giving
forecasts
> > for the weekend, such as;
> >
> > "Snow In Ringwood!"
> >
> > "Over A Meter This Weekend!" etc etc
> >
> > Now, I'm worried about this because of the misleading information -
there
> > not mentioning that the winds are going to become quite severe and you
> > wouldn't like to be caught up in the blizzard that will kick in this
> > weekend. Does this make them liable for false reports/neglegent
> > reports/unofficial forecasts/etc - ie like the discussion a while back
about
> > aus-wx people making their own predicitons???
> >
> >
> Commercial radio's presentation of weather info is one of my pet
> hates (not that I'm exactly alone in that - Rob Gell got stuck into
> them in no uncertain fashion in his talk at the AMOS conference).
> I haven't heard the reports you mentioned, but then I haven't listened
> to commercial radio in the last 24 hours.
>
> I think you'd have fun trying to sue over a failed forecast, though.
> Even in the world centre of litigation, the US of A, I'm not aware of
> any successful cases (the closest was a case which was upheld by a
> lower court but overturned on appeal).
>
> I'd sympathise with the forecasters trying to handle this situation.
> Because it's such an extreme event, for most it would be something
> they might come across once or twice in a career, and I don't think
> anyone is quite believing that what the models tell us is going to
> happen is really going to happen. On the one hand you can imagine
> the media frenzy that would ensue if an official Bureau forecast came
> out stating a 5% chance of 10cm of snow in Melbourne (one suspects
> that, in the media's hands, 5% would become 100% very quickly!); on
> the other hand, if there really is a major snowfall in Melbourne,
> remote a possibility as it may be, there will certainly be major
> disruption at the very least (although not as much as would be the
> case on a weekday), and the forecasters would be pilloried if they
> hadn't picked it. Trying to predict the snow/rain boundary is a very
> challenging forecasting problem in many parts of the world, but it's
> not one any of our people usually have to deal with in the urban areas.
> (To illustrate what can happen, IIRC the forecast for Christchurch
> when they got their huge dump in August 1992 was for snow down to
> 100 metres - a trivial error, probably equating to 0.5 degrees or so,
> but one that made the difference between heavy rain and 20-50cm (can
> you remember exact amounts, Ben?) of snow in the city).
>
> Blair Trewin
>
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>  message.
>  -----------------------jacob at iinet.net.au------------------------------

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From: "Michael Thompson" <michaelt at ozemail.com.au>
To: <aussie-weather at world.std.com>
Subject: Re: aus-wx: progged cold outbreak..
Date: Wed, 24 May 2000 20:27:38 +1000
X-Mailer: Microsoft Outlook Express 5.00.2014.211
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com

I am 99.9% certain that we wont see snow here in Wollongong. I even go as
far to say that historically snow is more likely in Sydney than Wollongong.
( Although in Sydney I would still be 99.5% certain of no snow.)

Michael


----- Original Message -----
From: Leslie R. Lemon <lrlemon at compuserve.com>
To: <aussie-weather at world.std.com>
Sent: Wednesday, 24 May 2000 9:56
Subject: aus-wx: progged cold outbreak..


> Dr. Jones wrote:
>
> > As for snow depths, the progs suggest moderate snowfalls at quite high
> > levels ahead of the Friday front (mostly above ~1500m) - I'ld guess
about
> > 5-25cm (with Buller probably getting the least). Behind the front
> > significant snowfalls will probably be confined to the southern slopes -
> > meaning Baw Baw, Lake Mt etc. The real limiter with this system will
> > probably be lack of moisture, as is often the case with cold outbreaks.
>
> Just wanted to tell all you folks that I am cheering for you!  I really
> would like to see heaps of snow on all of you!!  <S>  I do love snow
> myself....and we never get enough here.
>
> Good luck!!
>
> Les
> ************************
> Leslie R. Lemon
> Radar, Severe Storms, & Research Meteorologist
> Tel. 816-373-3533, 816-213-3237
> E-Mail: lrlemon at compuserve.com
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>


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From: "Michael Thompson" <michaelt at ozemail.com.au>
To: <aussie-weather at world.std.com>
Subject: Re: aus-wx: Snow Chase & new email addy
Date: Wed, 24 May 2000 20:33:30 +1000
X-Mailer: Microsoft Outlook Express 5.00.2014.211
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com

Just be careful on the roads guys, although from experience I know most of
you are careful drivers. I hope the police do not put up road blocks, they
did that with the last Southern Highlands fall in 1998. You may have to get
up there before the snow starts.


Michael

----- Original Message -----
From: Matthew Smith <tornado at bigpond.net.au>
To: <aussie-weather at world.std.com>
Sent: Wednesday, 24 May 2000 17:44
Subject: aus-wx: Snow Chase & new email addy


> Hi everyone!
> A snow chase will probably be on the cards this weekend around the Blue
> Mountains. A number of people have expressed interest so far in chasing,
> and anyone else who wants to come can ! An overnight stay may also be a
> possibility on saturday, to get the most out of this system as we can :)
>
> I am not sure if i will be able to go, I will know in the next day or 2.
> But if it still looks good on friday/saturday morning, I recommend
> people get together for a bit of  chase.
>
> Also please dont forget about the forecasts on the Sydney Storm Chasers
> page, done nightly by Matt Pearce (AKA Proffessor :) , for detailed
> forecasts for NSW.
> http://www.sydneystormchasers.com/forecasts/index.htm
>
> BTW I now have cable internet access with Telstra, and im loving it
> hehehe
> New emial is tornado at bigpond.net.au
>
> Matt Smith
> http://www.sydneystormchasers.com
>
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>  -----------------------jacob at iinet.net.au------------------------------
>


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From: "Michael Thompson" <michaelt at ozemail.com.au>
To: <aussie-weather at world.std.com>
Subject: Re: aus-wx: Cold outbreak update
Date: Wed, 24 May 2000 20:19:04 +1000
X-Mailer: Microsoft Outlook Express 5.00.2014.211
Sender: aussie-weather-approval at world.std.com
Reply-To: aussie-weather at world.std.com

 I can relate to your first paragraph well, we have a certain DJ here in
Wollongong that will interpret a forecast of  Fri - Isloated shower
possible, Sat - Early shower, Sun - Early shower as " the forecast for the
weekend.. wet, wet, wet " I have heard him do this on several occasions and
have vowed to ring and complain to the station next time.

Michael




> Hi Lyle and all
>
> Unfortunately, this practise is not confined to simply this event with
radio
> stations. Quite often in Sydney, and probably other places, radio news
> bulletins read out the official forecast as only either "rain" or "fine"
> depending on whether the forecast mentions any precip at all or not. So,
you
> sometimes have the situation of a forecast reading "chance late shower"
and
> it happens to be blue sky at the moment at 7am. The newsreader decides for
> themself that its not going to happen and says something along the lines
of
> "The BoM is forecasting rain but it looks like they've got it wrong again"
> and dismiss the forecast.
>
> It is not all stations that do this, but there are a number of main
> culprits. The ABC is the best in my view, simply becuase they read the BoM
> forecasts out word for word. Another good initiative they have is talking
to
> someone from the Bureau twice daily each weekday afternoon so you always
> have an accurate forecast presented. I suppose the safest bet is to check
> the web site yourself if you are planning on heading to the mountains or
> going boating or something like that, but lots of people don't, and I
think
> this is something that radio stations should seriously reconsider ie only
> reading out the BoM's official forecast.
>
> I don't think it is the same as the aus-wx people making their own
> forecasts, simply because the media are only doing it to create a story
and
> do not profess to be basing their headlines on any meteorological
knowledge.
> The vast majority of amateurs on this list who forecast, of which I am
one,
> try to present the information factually to the best of their ability
based
> on the available data and do not face pressures of making their forecasts
as
> sensational as possible. I think it would be a very sad day if and when it
> was ever proposed that amateurs were not allowed to put their own
forecasts
> on public internet space anymore as this would cut off a great tool for
> improving weather knowledge.
>
> Enough of my ramblings
>
> Matthew Pearce
>
>
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From: wbc at ozemail.com.au (Laurier Williams)
To: aussie-weather at world.std.com
Subject: Re: aus-wx: Snow Chase & new email addy
Date: Wed, 24 May 2000 10:45:03 GMT
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On Wed, 24 May 2000 17:44:13 +1000, Matthew Smith
<tornado at bigpond.net.au> wrote:

>Hi everyone!
>A snow chase will probably be on the cards this weekend around the Blue
>Mountains. A number of people have expressed interest so far in chasing,
>and anyone else who wants to come can ! An overnight stay may also be a
>possibility on saturday, to get the most out of this system as we can :)
>
Just one point to keep in mind -- and I guess this applies to anyone
going snow chasing anywhere this weekend. 

Once snow or icy weather starts in the Blue Mountains, the road
network closes down *very* quickly. Even a few cm of white stuff,
combined with ice from frozen recent rain, can close the Great Western
Highway within an hour or so of the snow starting. I live in
Blackheath, the highest town in the mountains, and it's fairly routine
to have the highway closed once or twice each winter, mainly because
the steeper grades become dangerous and the police today seem less
inclined to let people chance their luck than they used to (could they
be sued if they didn't close the highway and a car skidded on black
ice?) As little as 5cm of snow will close the highway (typically at
the hill on the Sydney side of Wentworth Falls, the grade just east of
Medlow Bath, and Victoria Pass), and 15cm or so will shut down the
railways as points clog up and power circuits malfunction. That
effectively isolates the Mountains. If there's a really good dump,
don't plan on getting back to Sydney for work on Monday!

I'll be watching the weather like a hawk on Friday -- I'm working in
Sydney and have to get home that night, and if the snow starts during
the evening I run the risk of being snowed out -- and missing being
snowed in!

Laurier

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From: "Matthew Piper" <mjpiper at ozemail.com.au>
To: <aussie-weather at world.std.com>
Subject: Re: aus-wx: Snow Chase & new email addy
Date: Wed, 24 May 2000 20:57:39 +1000
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Hi Matt and Everyone,

I will most certainly be willing to come along on a snow chase. I cant wait
to try out my new video camera properly and to take tonnes of snow pics. Ive
been watching the models like a hawk since Saturday and hope we all arent
let down. Fingers crossed that this is only the beginning of a really snowy
winter.

Matthew Piper

----- Original Message -----
From: Matthew Smith <tornado at bigpond.net.au>
To: <aussie-weather at world.std.com>
Sent: Wednesday, May 24, 2000 5:44 PM
Subject: aus-wx: Snow Chase & new email addy


> Hi everyone!
> A snow chase will probably be on the cards this weekend around the Blue
> Mountains. A number of people have expressed interest so far in chasing,
> and anyone else who wants to come can ! An overnight stay may also be a
> possibility on saturday, to get the most out of this system as we can :)
>
> I am not sure if i will be able to go, I will know in the next day or 2.
> But if it still looks good on friday/saturday morning, I recommend
> people get together for a bit of  chase.
>
> Also please dont forget about the forecasts on the Sydney Storm Chasers
> page, done nightly by Matt Pearce (AKA Proffessor :) , for detailed
> forecasts for NSW.
> http://www.sydneystormchasers.com/forecasts/index.htm
>
> BTW I now have cable internet access with Telstra, and im loving it
> hehehe
> New emial is tornado at bigpond.net.au
>
> Matt Smith
> http://www.sydneystormchasers.com
>
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From: "Matthew Piper" <mjpiper at ozemail.com.au>
To: "Aussie Weather" <aussie-weather at world.std.com>
Subject: aus-wx: 1960's Snowfalls in the Blue Mtns
Date: Wed, 24 May 2000 21:07:34 +1000
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<x-html>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=iso-8859-1" http-equiv=Content-Type>
<META content="MSHTML 5.00.2614.3500" name=GENERATOR>
<STYLE></STYLE>
</HEAD>
<BODY bgColor=#ffffff>
<DIV><FONT face=Arial size=2>Hi Everyone,</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>I am wondering if anyone has any idea when there 
was some massive falls of snow in the Blue Mtns during the 1960's. The reason I 
am asking is that my&nbsp;parents remember a couple of times that the railway 
line was totally cut and the whole region isolated. They think it was sometime 
during 1968. What are the chances of something like this happening again with 
this forecast cold outbreak.</FONT></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=Arial size=2>Matthew Piper</FONT></DIV></BODY></HTML>
</x-html>
Date: Wed, 24 May 2000 10:49:43 +0100
To: aussie-weather at world.std.com
From: Norman Lynagh <lynagh at dial.pipex.com>
Subject: Re: aus-wx: Cold outbreak update
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In message <200005240831.SAA06954 at munya.earthsci.unimelb.edu.au>, Blair
Trewin <blair at met.Unimelb.EDU.AU> writes
>> 
>> Hi Blair,
>> 
>> as a BoM staff memeber, you may be interested in this.
>> 
>> Radio stations (not TV stations that I know of) have been giving forecasts
>> for the weekend, such as;
>> 
>> "Snow In Ringwood!"
>> 
>> "Over A Meter This Weekend!" etc etc
>> 
>> Now, I'm worried about this because of the misleading information - there
>> not mentioning that the winds are going to become quite severe and you
>> wouldn't like to be caught up in the blizzard that will kick in this
>> weekend. Does this make them liable for false reports/neglegent
>> reports/unofficial forecasts/etc - ie like the discussion a while back about
>> aus-wx people making their own predicitons???
>> 
>> 
>Commercial radio's presentation of weather info is one of my pet
>hates (not that I'm exactly alone in that - Rob Gell got stuck into 
>them in no uncertain fashion in his talk at the AMOS conference).
>I haven't heard the reports you mentioned, but then I haven't listened
>to commercial radio in the last 24 hours.
>
>I think you'd have fun trying to sue over a failed forecast, though. 
>Even in the world centre of litigation, the US of A, I'm not aware of
>any successful cases (the closest was a case which was upheld by a 
>lower court but overturned on appeal).
>
>I'd sympathise with the forecasters trying to handle this situation.
>Because it's such an extreme event, for most it would be something
>they might come across once or twice in a career, and I don't think
>anyone is quite believing that what the models tell us is going to
>happen is really going to happen. On the one hand you can imagine 
>the media frenzy that would ensue if an official Bureau forecast came
>out stating a 5% chance of 10cm of snow in Melbourne (one suspects
>that, in the media's hands, 5% would become 100% very quickly!); on
>the other hand, if there really is a major snowfall in Melbourne,
>remote a possibility as it may be, there will certainly be major 
>disruption at the very least (although not as much as would be the 
>case on a weekday), and the forecasters would be pilloried if they
>hadn't picked it. Trying to predict the snow/rain boundary is a very
>challenging forecasting problem in many parts of the world, but it's
>not one any of our people usually have to deal with in the urban areas.
>(To illustrate what can happen, IIRC the forecast for Christchurch 
>when they got their huge dump in August 1992 was for snow down to
>100 metres - a trivial error, probably equating to 0.5 degrees or so,
>but one that made the difference between heavy rain and 20-50cm (can
>you remember exact amounts, Ben?) of snow in the city).
>
>Blair Trewin

This is a problem faced by forecasters in the UK on a good number of
occasions in an average winter. It's almost impossible to get it just
right. The majority of the heavy snowfall events in the main populated
areas come in very marginal snow/rain situations, often when relatively
mild Atlantic air is trying to displace cold continental air. The
1000-500 mb thickness is a very poor guide as to whether it will rain or
snow. A much more useful tool here is the 1000-850 mb thickness.

I remember walking in snow on Mt. Donna Buang in 1967. I was living in
Melbourne at the time, attending Weather Officer Course No. 3 at the BoM
Training School. It seems a long time ago!

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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From: "Ben Tichborne" <tich at netaccess.co.nz>
To: <aussie-weather-digest at world.std.com>
Subject: aus-wx: Re: aussie-weather-digest V1 #587
Date: Wed, 24 May 2000 23:58:42 +1200
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The likelihood of a Tasman low
> and the consequent more southerly flow also makes me more optimistic
> for snow in Canberra than I was 24 hours ago. (Canberra often misses
> out in SW outbreaks because of the rainshadow from the Brindabellas;
> a southerly, or even south-easterly if it's cold enough, is more
> favourable).

Snow in Canberra on Saturday night?. I'm sure should Crusaders will handle
such conditions better than the Brumbies. (but we're gonna thrash 'em
anyway)

> As for Melbourne, I'd now assess the probabilities as being:
>
> Snow falling in Dandenongs 80-90%
> Snow settling in Dandenongs 70%
> Snow falling in suburbs 40%
> Snow falling in central Melbourne  25%
> Snow settling in central Melbourne 10-15%
> Major snowfall in Melbourne (10cm+)  5%

 Don't forget we're still in May. Has such an icy blast (ie with widespread
snow to low levels) hit so early in the season before?. In NZ, the last such
similar event happened back on 29/30 May 1989, and saw record low maximum
temperatures in many places, not to mention widespread snow.

:
Trying to predict the snow/rain boundary is a very
> challenging forecasting problem in many parts of the world, but it's
> not one any of our people usually have to deal with in the urban areas.
> (To illustrate what can happen, IIRC the forecast for Christchurch
> when they got their huge dump in August 1992 was for snow down to
> 100 metres - a trivial error, probably equating to 0.5 degrees or so,
> but one that made the difference between heavy rain and 20-50cm (can
> you remember exact amounts, Ben?) of snow in the city).

 In 1992 (I wasn't living there then, but I happened to be in Christchurch
at the time) snow was predicted to fall to near sea-level in the forecasts
for a day or so before the event, but only to settle above about 100 metres.
Indeed on the 27th, this forecast was correct for the whole day. But in the
evening, the temperature dropped just a degree or two, and this was all it
took for heavy snow to blanket the city (depths varied between 10 and 30 cm
in the city - drifts up to 2 metres were reported on the higher Port Hills).
Once the temperature rose a few degrees about midday on the 28th, it was
back to rain again.

 BTW, once this upcoming cold airmass departs Australia, the longer range
models show it moving onto NZ. However one of the models (MRF 9 day
forecasts) forsees (or foresaw) a low forming over the lower South Island,
so the situation may become more complex than just a simple cold southerly/
southwesterly outbreak. Should be very interesting.




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X-Sender: paisley at mail.cobweb.com.au
Date: Wed, 24 May 2000 21:34:17 +0930
To: aussie-weather at world.std.com
From: Phil Bagust <paisley at cobweb.com.au>
Subject: Re: aus-wx: Snow Chase & new email addy
Sender: aussie-weather-approval at world.std.com
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I can speak for myself [and also Andrew and Kathryn I think] when I say
that we will be out and about in the Mt Lofty Ranges on Friday/Saturday,
and any white stuff at our lower altitudes will only be good news for you
out east.  An [unlikely] really big dump might see most of the mid north
covered - that would be worth a few snaps!

Good luck all, and keep your tootsies warm :)

Phil 'Paisley' Bagust
paisley at cobweb.com.au
http://www.chariot.net.au/~paisley2


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From: wbc at ozemail.com.au (Laurier Williams)
To: aussie-weather at world.std.com
Subject: Re: aus-wx: progged cold outbreak..
Date: Wed, 24 May 2000 12:08:10 GMT
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On Wed, 24 May 2000 14:05:08 +1000 (EST), Blair Trewin
<blair at met.Unimelb.EDU.AU> wrote:

>Today's model update (elaborating on what David's already said). Note
>that we start to pick up the US model (which goes out to 3 days) now.
>
Thanks, Blair, for an excellent job summing up the models. Here's my
5c worth and a couple of updates.

I don't believe it's any more a case of whether there'll be a major
polar outbreak, but rather a matter of detail in where the largest
snow dumps occur, and their timing. 

The 200hPa MRF analysis for 10am EST this morning currently at
ftp://sprite.llnl.gov/pub/fiorino/ncep/mrf/grf/current/mrf10.w20.000.ausnz.gif
shows the polar jet oriented South/North well under WA, with core
speeds over 100kts. It loops from 60S up to 40S, then straight back
south again, with undiminished core speeds. The MRF maintains this
jet, moving it slowly ENE until Friday morning, after which the trough
rapidly breaks, leaving a deep closed upper low west of Tasmania. In
response to the upper trough, the high SW of Perth, which has been
slowly shifting south over the past couple of days, is now centred at
around 50S with a strong ridge to the Antarctic High. If you download
and animate the IR satpix from
http://www.yoko.npmoc.navy.mil/nsds-e20shots/austir/, which
conveniently go down to 60S, you can actually see the main front
developing, and cold air streaming northeastwards behind it. It will
be the development of the secondary low somewhere W of Tasmania in
response to the upper cut-off low that will slingshot this cold air
field due north over the mainland. 

The latest (00z) GASP has a tongue of sub-528 thickness covering most
of Victoria and southern NSW by 00z Saturday, moving into the east of
both states and weakening to sub-536 by 00z Sunday, and broadening to
be sub-540 south of a line Port Augusta to Port Macquarie by 00z
Monday. GASP develops a low on Tasmania at 00z Friday, moving it
slowly away SE through to Monday with little real development, but
significantly places it in a NW/SE trough extending SE from eastern
Bass Strait. The GASP 700 humidity pattern is interesting, and differs
from the other models in having a pronounced dry slot after the
initial frontal rainband, but then brings >90% humidity from the S
across Vic and southern NSW by 00z Sunday. 850 temps are sub -4 across
most of Vic and S NSW at 00z Saturday, contracting to eastern NSW by
Sunday, but GASP keeps the 850 temp below 0 over almost all Vic and
NSW through to the end of the model run on Wednesday.

The EC is broadly similar, but about 12 hours later in its timing, and
moves a low from just under SE SA east to around Gabo Island on the
Saturday evening, whereupon it bombs from 996 to 982hPa in 24 hours
while moving only very slowly east. This splits the southerly flow,
trending the surface flow southeasterly by Tuesday, and maintaining a
NW/SE upper trough back through Victoria and western NSW, all with a
thickness of around 536. Unfortunately, I don't have humidity or temp
details for the EC.

The latest (00z) MRF develops a low west of Bass Strait at 00z Friday,
moving it rapidly to just SE of Tassie by 12z Friday, then bombing it
to ~977hPa by 00z Sunday with little further movement. This produces
SSW then SWlies over Vic and NSW, but MRF keeps most of NSW and Vic
enclosed by the 540 line through to Tuesday, with most of the country
from central NSW southwards showing >90% 850hPa humidity, -3 to -6
850hPa temps and decent precipitation, also through to Tuesday! The
MRF also has an extraordinarily agile cold pool at 500hPa, which
appears to perform a somersault around Tasmania with a central
temperature around -36. Starting west of Tas/South of Adelaide at 00z
Friday, it crosses Melbourne at 00z Saturday, and covers much of
eastern Vic, SE NSW at 12z Saturday before drifting away to the east.
Meantime, a second pool of <-38 forms on NE Tas at 12z Sunday before
diminishing and shifting off to the ENE on Monday. 

The 00z NOGAPS is rather a dry argument. Its timing is similar to GASP
and MRF, with the main tongue of sub-528 air covering most of Victoria
at 00z Saturday (sub 522 over Tassie!). The thermal trough moves
slowly east, cutting off over the NSW central/Illawarra coast by 00z
Sunday. NOGAPS keeps moving everything away to the east or SE, though
it still leaves a substantial 500hPa temperature trough (sub -24)
lying back E/W through central NSW. NOGAPs, however, has no rain
anywhere over land after the initial rainband with the front.

All this detail is nicely tantalising, but my guess is that, on the
day(s) in question it will be local-scale developments that will
decide where the most interesting weather occurs. Certainly, Victoria
from the ranges south would appear to be the place to be, but the
tendency of all of the models, in one way or another, to produce a
stagnant pool of very cold air over the SE of the continent could
result in quite a protracted period of widespread, though probably
light, snow. 

I think the things to watch for on the weekend will be the movement of
the upper cold pool(s), possible surface developments as far north as
central NSW, the movement of the major low and the orientation of
surface airflow, and the dewpoints -- the feature the models
*dis*agree on most is where the humidity will be.

I said 5c worth, and this is probably more than $1, but it is
certainly the most impressive development I have seen since I've had
internet-quality forecast materials available.

Laurier


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From: wbc at ozemail.com.au (Laurier Williams)
To: aussie-weather at world.std.com
Subject: Re: aus-wx: 1960's Snowfalls in the Blue Mtns
Date: Wed, 24 May 2000 12:15:34 GMT
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On Wed, 24 May 2000 21:07:34 +1000, "Matthew Piper"
<mjpiper at ozemail.com.au> wrote:

>Hi Everyone,
>
>I am wondering if anyone has any idea when there was some massive falls of snow in the Blue Mtns during the 1960's. The reason I am asking is that my parents remember a couple of times that the railway line was totally cut and the whole region isolated. They think it was sometime during 1968. What are the chances of something like this happening again with this forecast cold outbreak.
>
It was July 1965, Matthew -- around mid month from memory. It snowed
in Katoomba from about 9am on a Saturday until about 4pm the next day,
with about 30 to 45cm of snow across the mountains. They brought some
steam engines out of mothballs to try to clear the points and keep the
railway open, but power failures ultimately stopped everything. Roads
were closed for several days. There was also a substantial snowfall in
August 1962. 

Good snow in the Blue Mountains usually requires a S or SE airflow or
the nearby passage of a surface low (like the one that gave the
Mountains around a metre of snow in 1905). A SW flow tends only to
give snow showers as some of the larger Cu that haven't dumped their
load south of Oberon pass by.

Laurier

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From: wbc at ozemail.com.au (Laurier Williams)
To: aussie-weather at world.std.com
Subject: Re: aus-wx: Cold outbreak update
Date: Wed, 24 May 2000 12:32:12 GMT
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On Tue, 23 May 2000 15:38:09 -0700, "Willis, Andrew"
<adwillis at bechtel.com> wrote:

>> Just in case previous model runs didn't get everyone excited enough,
>> the 00Z GASP run (just out) has a thickness of 522 over Melbourne on
>> Saturday morning...
>> 
>Hi All
>
>I've been following the cold outbreak discussion with interest.
>
>Can someone describe briefly what a 522 thickness of the 00Z GASP is.
>
Hi Andrew. This refers to the distance in geopotential dekametres
(read "tens of metres") between the points vertically in the
atmosphere where the pressure is 1000hPa and 500hPa. As colder air is
denser, the smaller the distance the colder the airmass. When the
distance drops below 5400 metres (i.e. 540), there's an old
rule-of-thumb that says snow is likely, though this seems to have been
designed by US/European forecasters as it applies (sort of) in that
latitude. However, at Victorian and Tasmanian latitudes, a thickness
of 5220m (522) could well produce snow to sea level.

As has been pointed out in other posts, however, it's a pretty crude
measure as there's a lot of variation that can take place between
1000hPa (typically just above the surface) and 500hPa (typically about
18,000 feet up. The 850hPa temperature (about 1,400 metres up in cold
weather) is a good indicator, as it's the temperature of the lower
atmosphere that has most to do with whether precipitation falls as
rain or snow. If you assume the atmosphere will warm up by about 1
degree C each 100m of descent, and that it'll snow when the temp falls
below ~2 degrees, you can calculate the likelihood of snow falling at
your altitude. So if you're at an altitude of 800m, for example, an
850hPa (1400m)  temp of -3 would warm up about 6C to around +3, and
snow would be borderline. There's lots that can go wrong with this
rule-of-thumb, too, but it's a bit better than thickness, and 850
temperature forecast charts are available for all the main models.

Oh, the 00Z GASP is the 00.00 UTC (10am EST) run of the Bureau of
Meteorology's main global computer model.

Laurier


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 -----------------------jacob at iinet.net.au------------------------------

Date: Wed, 24 May 2000 22:28:26 +1000
From: David Carroll <davidkc at nia.net.au>
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To: aussie-weather at world.std.com
Subject: Re: aus-wx: Snow Chase & new email addy
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HI All.

Well everyone is very keen for some snow around the Blue Mountains this
weekend.. I'm really hoping for some white stuff myself up here in Bathurst and
surrounding areas.. As Michael wrote about roads.. I know that Yetholme and Mt
Lambie get closed very fast from previous years.. Just near airport of Bathurst
at Raglan the SES put up road barriers and there is basically no way of driving
anywhere.. Last year Mitchell Hwy to Orange was closed,  Oberon rd was also
closed, and the most obvious one Great Western Hwy.. So lets hope you all get
safely to whatever town you choose,, especially you Matt Smith..
I intend on having radio scanner tuned into emerg services for any signs of snow
falls in my area.. Dont worry anyone,, first sign of snow, you all will be first
to know..

Dave

Michael Thompson wrote:

> Just be careful on the roads guys, although from experience I know most of
> you are careful drivers. I hope the police do not put up road blocks, they
> did that with the last Southern Highlands fall in 1998. You may have to get
> up there before the snow starts.
>
> Michael
>
> ----- Original Message -----
> From: Matthew Smith <tornado at bigpond.net.au>
> To: <aussie-weather at world.std.com>
> Sent: Wednesday, 24 May 2000 17:44
> Subject: aus-wx: Snow Chase & new email addy
>
> > Hi everyone!
> > A snow chase will probably be on the cards this weekend around the Blue
> > Mountains. A number of people have expressed interest so far in chasing,
> > and anyone else who wants to come can ! An overnight stay may also be a
> > possibility on saturday, to get the most out of this system as we can :)
> >
> > I am not sure if i will be able to go, I will know in the next day or 2.
> > But if it still looks good on friday/saturday morning, I recommend
> > people get together for a bit of  chase.
> >
> > Also please dont forget about the forecasts on the Sydney Storm Chasers
> > page, done nightly by Matt Pearce (AKA Proffessor :) , for detailed
> > forecasts for NSW.
> > http://www.sydneystormchasers.com/forecasts/index.htm
> >
> > BTW I now have cable internet access with Telstra, and im loving it
> > hehehe
> > New emial is tornado at bigpond.net.au
> >
> > Matt Smith
> > http://www.sydneystormchasers.com
> >
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> >  -----------------------jacob at iinet.net.au------------------------------
> >
>
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>  -----------------------jacob at iinet.net.au------------------------------

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Date: Wed, 24 May 2000 22:53:57 +1000
From: Andrew Miskelly <amiskelly at ozemail.com.au>
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Subject: aus-wx: Amateur Forecasts
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Hi all,

Can I just quickly say that I think all of the amateur forecast sites
belonging to people on the list are sensational. I think it is very
important to have these sites which unlike official sites, aren't prone
to conservative forecasting and other politics. I certainly consider
them to be more acurate as they are often derrived from discussions like
the ones we have been having in the past week among many great minds.

Matthew Pearce, MSC, Nick Sykes and everyone else, well done to you all.
I for one appriciate your work.

Andrew (Hoping for SWlys in Taralga on Sat) Miskelly.

--
Andrew Miskelly
Illawarra/Southern Tablelands, NSW
amiskelly at ozemail.com.au
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 -----------------------jacob at iinet.net.au------------------------------

X-Originating-IP: [203.23.72.3]
From: "Lyle Pakula" <lyle_pakula at hotmail.com>
To: "Aussie-Weather Mailing List" <aussie-weather at world.std.com>
Subject: aus-wx: AWS Heaters
Date: Wed, 24 May 2000 20:12:01 +1000
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Reply-To: aussie-weather at world.std.com

Hi,

Does anyone know if they have activated the heaters (so to measure snow
fall) for the AWS's at higher altitudes, in particular, Mt Baw Baw?

Cheers, Lyle.

p.s. If anyone is planning on travelling to Baw Baw, me and some friends
will be staying in Icy Creek from Sat -> Tues and visiting the Mt every
day - drop us a line and we'll see you there!

-  - ---==( lyle_pakula at hotmail.com )==--- -  -
     .
    / \  .
   /~~~\/ \ " No Friends On A Powder Day "
  /     \  \
 /       \  \





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