Topic: NSW/Qld Severe Hailstorms then Cold/Snow: 19 to 22 of October 2008

[Michael Thomas]

We should be seeing a few storms around NSW for the next several days. For today (or tomorrow depending on where you are), GFS has LI's down to -7 around the northern SW slopes and adjacent areas. I do not believe this is realistic since low level moisture is quite poor with dp's currently only around 10C. Temps are expected to get up around 30C in places which should be enough for storms, just they will be quite high based by the look of things. Monday isn't too great at this stage either but I wouldn't rule out a nice storm or two on the ranges on the mid-north coast. I know it's a bit of a wild card, but I am still hoping something interesting can come off on Tuesday and Wednesday. It appears that shear will improve on Tuesday and hopefully there will be some nice dp's in place around the mid-north coast and northern rivers. Wednesday looks to be quite a dynamic day with a strong upper trough pushing though. Currently the timing doesn't look too good so we will just have to wait and see.

Michael

[pingtang]

Yes,im not convinced we'll see anything of great quality today given the moisture at various levels. CAPE values are expected to reach 2000 near the town of Young assuming dewpoints stay in the teens.I agree that this seems unrealistic  given some single figure d'ps are likely today west of the ranges.  Another concern is high moisture at 600-800mb,this could lead to embedded storms and a rather messy sky later in the afternoon. Windshear isnt near as bad as last weekend,but its still far from ideal. The seabreeze will probrably penetrate into Goulburn in the late afternoon, but im not sure if this will helps things or not. So im expecting some high based storms today,with a risk of embedded storms and a mid level cloud feast later in the afternoon. Some good lightning is possible.

[Michael Thompson]

Sunday 19th October 20008
Target - Nowra
Prospects - Very Poor < -- please note this before being too critical of forecast
Expectations - Lightning after 8pm

Moisture has dried up quicker than a K Tel super mop. Although CAPE and LI figures look impressive for the SW slopes it will be hard to see much occurring. If anything does develop before sunset it has the potential for some nasty dry microbursts.

As the trough moves NE towards the coast so too does a wedge of moisture around 700-500mb, slightly better surface moisture may allow enough interaction to fire off some high based rubbish, initially on the ranges near Braidwood - Marulan and this should move east.

Despite rubbish storms (if any), good lightning photos and storm severity only have a weak correlation if any, so an opportunity may present it self for pictures. High bases and lack of rain will give nice bolt length and visibility, but I am going with best forecast scenario here.

Maverick factor on the coast is the SE wind change, at this stage so shallow I cannot see it being a great influence, but may lead to some cloud which may mar anything that does develop.

As often is the case the real show will be in Mudgee to the upper Hunter 18-24 hours later. ( Monday afternoon )

[Steven]

I can't see there being much for S QLD on Tue/Wed with very little instability around, unless I'm missing something here.

[Michael Thomas]

Hi Steven,

No you are not missing anything really. I slipped Qld in to the title as I would guess there is a chance of storms in SE Qld on Tuesday and/or Wednesday. Latest GFS run actually looks a bit more promising in my opinion with a nice mid level jet (50knot max) nosing into the mid north coast and northern rivers areas. I expect some activity could spill over the border ranges into S Qld. Here's a forecast sounding from the Brisbane valley area-

http://soundings.bsch.au.com/skew-t.html?source=ncep&lat=-27.65&lon=153.1&date=2008102106&gribdate=2008101900

Not much CAPE but I think the temp and dew point temp will be higher the 23/15 plotted.

Michael

[Dave Nelson]

hi gang

  what a crazy day....   targetted the sthrn highlands region .... total bust.  It was ac tually the minor looking
line of instability that we drove under around Mossvale that would become the real stormline  later on.
got a bit south of Marulan and realised nothing much was going to happen down that way so headed back to
Sydney.  Weatherzone was showing that that minor instability line had taken off and several cells had fired up
over the Razorback area SW of Campbelltown and were heading NE'wards.  By the time we got back to
Campbelltown area, the main cell was already over the "hills suburbs" of NW Syd. but a new cell was firing up
in its wake. We followed it up the Nthrn Rd via Penrith and nth to that fuel station by the roundabout
We sat there and awaited its arrival. some reasonable lightning (nothing wild) some heavy rain bursts, no hail.

  Coming back down Richmond Rd to Blacktown we could see 2 other good looking cells to the SE.  the radar
showing them to be on the coast ~ the Helensburg to Wollongong area.  Very photogenic  really nice updraughts

turned out an ok day after the wasted sthrn drive earlier on   c'est la vie

Gosford turned out to be the "place to be"   those 2 earlier cells went up through the Hawkesbury and hit Gosford
head on!!

Dave and Cindy

[nmoir]

These are the nice updrafts which intesified off the coast near woollongong , i was wishing the crappy cloud would get out of the way so i could see the bases , then i realised they were  the bases , these storms grew from the hips up! they moved NE

[James]

An afternoon of thunder in Galston as cells moved over and then continued to develop overhead. Got a photo of the storms off the Illawarra which looked nice but very high based.

   

The stuff over the hills was also high based but some nice lightning on the front end of the rain shafts. Photo of some sun lit mammatus on the back end. My photo is pretty similar to Nick's, excuse the double up

 

Tomorrow looks mildly interesting. At this stage I like the Upper Hunter with the easterly surge inland providing a focus for storm development. See how it looks in the morning.

[Richary]

Lots of rumblings here at Rydalmere as things passed to the west then north of here. Nothing really photogenic and no bolts seen (until about an hour ago, way off to the north on the horizon). On the radar some of the cells seemed to develop brief heavy rainfall at times. We had some rumbles from almost overhead but nothing to be seen.

[Jimmy Deguara]

Hi guys,

I did put in a little observation session turned into a small chase. My main objective is to prove that what I was seeing was actually hailstones. After roaming around, it was not until I got to near Box Hill area / Oakville that pea sized hailstones fell. However, mostly heavy rain was observed. I was never really in the core at that time.







I didn't bother keeping up with the storm as it drifted beyond towards the Cental Coast hinterland.

All photos for 19th October 2008


Regards,

Jimmy Deguara

[David Brodrick]

Here's an article from the ABC News website. I haven't seen BOM so explicitly provide prior warning of supercells before. Chris put me onto this.

From http://www.abc.net.au/news/stories/2008/10/20/2395638.htm

Granite Belt urged to brace for 'supercell' storms

Weather forecasters have given people in the Granite Belt region of southern Queensland early warning of a potential 'supercell' developing tomorrow afternoon.

Supercells are severe thunderstorms that can produce strong winds, torrential rain and hail.

Senior forecaster Brian Rolston says there could be a couple of days of stormy weather heading up from northern New South Wales, and the southern border region is likely to cop the worst.

"If it's going to happen it will by the southern Darling Downs Tuesday afternoon, probably more Tuesday than Wednesday," he said.

"There'll be thunderstorms on Wednesday as well, but the potential will be greater on Tuesday it looks like."

[David C]

"Weather forecasters have given people in the Granite Belt region of southern Queensland early warning of a potential 'supercell' developing tomorrow afternoon."

Sounds exciting!
 
One thing's for sure, with a temperature of ~20C here at Ryde, there's no supercell potential here today. A few moments ago during lunch I could barely see some solid towers way off to the west and north west of North Ryde, somewhere over the Wollemi and beyond.

[David C]

Cell showing consistent and very solid reflectivity heading towards Bulahdelah at the moment, heading south east. Most probably a mesocyclone in there.

[Michael Bath]

Interesting cell passed through the Blue Mountains a short while ago which dropped some decent sized hail at Blackheath. Surprised it was not a warned cell.

Hail photo by Lindsay

Not a bad sounding above the coastal crap - storms certainly needed to form above 900 hPa:

Sydney 04z

[Harley Pearman]

David, a similar storey has appeared in the Brisbane Times too 20/10/2008 under the heading "Supercells spark tornado fears", Brisbane times by Andrew Wight - 6.48 am.

I don't recall seeing storey headlines warning the public of the potential for supercell thunderstorms. The article takes it one step further by stating that supercells are expected to sweep into Brisbane tomorrow from the Darling Downs and Northern New South Wales bringing torrential rain and strong winds.

The article similar to the one posted above states that conditions will be right for formation of supercells and even states that there is the possibility of tornadoes.

However I have viewed the Bureau of Meteorology forecast for this region and there is a forecast of thunderstorms for the Granite Belt and region but I did not see any mention of large hail, damaging storms and or tornadoes or any specific warnings to the public.

There is also a general forecast for an east coast low forming off the New South Wales north or far north coast. That should be watched too and weather models currently show an east coast low off the far north coast or off south east Queensland for Wednesday.

On another matter, in addition to yesterday storm over far western and NW Sydney further storm activity has occurred close to Sydney but there has been no thunderstorm around Blacktown. A brief shower recently occurred but the southerly wind change has really taken hold now.

Harley Pearman