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Date: Sat, 19 Sep 1998 10:27:16 +1000
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From: Michael Bath 
Subject: Re: aussie-weather: Info. on Tornadoes...
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A true waterspout can certainly move over land but would very quickly
dissipate.

A note about the waterspout reported on the 18th August. There was a line
of very active thunderstorms from Sydneys mothern beaches stretching down
to the Wollongong area. Rainfall intensities reported from a couple of
stations along the coast were in the order of 150mm/hour for short
durations. Clifton Gardens is near Middle Head in Sydney harbour and would
have been exposed to outflow from these storms if not direct effects (I'm
not sure of how far the storm base extended into the harbour). Have a look
at these pictures I took from work at Parramatta (taken through a window
between 8.30 and 9am):
http://australiansevereweather.simplenet.com/photography/photos/1998/0818mb0
1.jpg
http://australiansevereweather.simplenet.com/photography/photos/1998/0818mb0
2.jpg
http://australiansevereweather.simplenet.com/photography/photos/1998/0818mb0
3.jpg
The left side of No 2 and 3 is looking east towards where the waterspout
would have occurred.

Opinions....?

Michael

At 21:24 18/09/98 +1000, you wrote:
>Thanks for that Paul!  I already knew the difference, but it was nice of
>you to take the time to write a response :-)  My question was probably a
>little ambiguous...what I meant was that can a true waterspout actually
>go over land?  (IE from large Cu, and not from a mesocyclone)  In my
>experience so far and from my knowledge, I didn't think that was
>possible, so I suggested that perhaps they were tornadoes...
>
>But thanks again Paul!
>Anthony
>
>Paul Graham wrote:
>
>> > Interesting!  But were they really water spouts or tornadoes?  Just
>> that
>> > I didn't think a water spout could survive the transition between
>> water
>> > and land.  I thought only tornadoes could...so therefore wouldn't it
>> be
>> > by definition a "tornadic waterspout?"  Or perhaps I'm wrong...
>>
>> There are no great distinctions.  A tornado over the water is a
>> waterspout
>> and a waterspout over land is a tornado.  Strong tornadoes/waterspouts
>>
>> tend to be the result of deep circulations (mesocyclones) associated
>> with
>> supercell thunderstorms and tend to be a spring or summertime
>> continental
>> feature.  Weak tornadoes/waterspouts tend to be the result of shallow
>> circulations (misocyclones) perhaps resulting from a convective cell
>> outflow boundary or a gust front and are common over land and ocean
>> alike.
>> Sometimes the term "tornadic waterspout" is used to refer to a tornado
>>
>> over the sea which resulted from a deep circulation (mesocyclone).
>> Again,
>> there are no strict distinctions since they are all just localised
>> whirling winds.
>> Hope you find what I wrote useful.
>> - Paul 

*=====================================================*
               Australian Severe Weather
     http://australiansevereweather.simplenet.com/
 thunderstorms, tropical cyclones, weather photography
   storm chasing, tornadoes, observations, lightning
*=====================================================*

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Date: Sat, 19 Sep 1998 17:42:56 +1000 (EST)
From: Paul Graham 
To: aussie-weather at world.std.com
Subject: aussie-weather: Weather Update...
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Severe Thunderstorm Advice issued this afternoon for the Central West of
NSW (large hail and destructive wind).  Not surprising for today. 
- Paul.

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From: "Jane ONeill" 
To: "Aussie Weather" 
Subject: aussie-weather: Melbourne Storms
Date: Sat, 19 Sep 1998 19:48:37 +1000
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Melbourne had a few storms in the area today - heavy rain in the Yarra
Valley at about 2pm & a good one across the southern and south eastern
suburbs around 5pm.  Fair amount of instability in the mid to late afternoon
but died down around dusk.

Jane ONeill

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Date: Sat, 19 Sep 1998 20:13:26 +1000 (EST)
From: Paul Graham 
To: Aussie Weather 
Subject: aussie-weather: Ground Jet Streaks...
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Thought this abstract about ground jet streaks was interesting and worth
posting to the mailing list in case people haven't already seen it: 
http://www.bom.gov.au/bmrc/meso/New/Gallery/People/Peter_May/grndJetStr.htm

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Date: Sat, 19 Sep 1998 20:37:39 +1000 (EST)
From: Paul Graham 
To: Aussie Weather 
Subject: aussie-weather: Latest Weather Update...
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Just had a look at the latest NSW radar loop (temporary available through
the Olympics test site) which shows a line of thunderstorms extending from
somewhere south of Parkes down to somewhere near Yass moving in an
easterly direction.  The precipitation intensities are shown to be
decreasing from around 10-20mm/hr to 2-10mm/hr or less.  Perhaps the
northwestern end may affect Sydney later (perhaps early tomorrow - in time
to spoil the Cycle Sydney I am hoping to go in)
- Paul.