Topic: NSW / SE QLD Storms: 13-14 April 2008

[Macca]

Interesting (slight) variations in the models today and tomorrow.

GFS indicates storms are possible this afternoon and tomorrow (with some NICE instability forecast for tomorrow afternoon with -5 to -6 LIs) over the SE corner.

Briefly on today...GFS is going for some precip over the SE corner of QLD (which, given the inputs would have to be convective). MesoLAPS doesn't want a piece of this at all but LAPS takes half a piece as does the BoM who have gone for "afternoon shower" - somewhat of a half-way forecast but probably the right one given the uncertainty both ways. If GFS was to be right, plotting 28/15 on the GFS forecast sounding for today gives LI's of about -3 and CAPE of 900j/kg. Shear is enough (pretty nice actually) to get storms moving and maybe enough to get something briefly organised (at least enough to make it last longer than 30 mins).

Tomorrow sees the upper level temps drop 3-4C compared to today with the approach of a decent upper level trough. GFS has -5 to -6 LI's plotted over Brisbane which is fairly nice. Again, MesoLAPS doesn't want as much to do with this as GFS.

OK...i've just worked out the difference (at least for today)...GFS kicks the upper trough further N today and far enough N to have an influence on our weather here. It pushes a 2C temp drop at 500mb across the SE corner between 6z and 12z tonight as the upper trough moves in. MesoLAPS on the other hand slides the upper trough more to the ESE. Interesting difference. Hopefully GFS is correct although hard to get evidence at this stage as to which one is looking more likely.

Anyway - something to watch at least.

Macca

[nmoir]

 It is the 9th anniversary of that nasty supercell , some instability around this afternoon in sydney too

I spent a week covering the damage from that event , even now you can see the damage path with carful eyes from the air if you look for newish tiled roofs

[Richary]

At the time I was working for Telstra in the city, and the next day had to go to the Paddington Exchange to change some backup tapes. I decided to walk the journey.

As I got closer to Paddo, it was obvious the damage became worse and worse. Down one side of the road every car windscreen was smashed, down the other side every rear window. And it looked like someone had taken to them all with a large ball hammer. Once at Paddington, I went up to the roof (about 6 floors high). Every tile and slate roof visible around the area was trashed.

A workmate at the time lived at Eastgardens and had just spent 18 months renovating the inside of his house, new cornices and all that. All ruined. At least he joked that now with the insurance he could pay someone to do it properly.

[Michael Bath]

It was Wednesday 14th April 1999 - some articles are linked from here (had to cull a few old ones as the reports are now gone unfortunately)

http://australiasevereweather.com/storm_news/990414.htm

[Michael Bath]

BoM now has warning out for a few NSW districts:



SEVERE THUNDERSTORM WARNING
for LARGE HAILSTONES, FLASH FLOODING and DAMAGING WIND
For people in the
METROPOLITAN,
ILLAWARRA and parts of the
HUNTER and
CENTRAL TABLELANDS Forecast Districts.


Issued at 12:23 pm Sunday, 13 April 2008.


Severe thunderstorms may produce large hailstones, very heavy rainfall, flash flooding and damaging winds in the warning area over the next several hours. Locations which may be affected include Gosford, Sydney, Parramatta, Wollongong, Lithgow and Katoomba.

[Macca]

All the while I was doing my post this morning i was trying to ignore the fact that Sydney was looking pretty nice for storms (AGAIN!).  Bit hard to ignore on a day like April 14th thou as Nick and others have pointed out.  Seriously...this is the third weekend running there have been storms in Sydney.  I have seen more storms in Sydney this year, being the 2008 calander year, than I have here in Brisbane and I have spent a total of 10 days in Sydney and 94 in Brisbane. 

On a side note, some moderate showers have popped up on the ranges east of Stanthorpe!!!  COMON QLD!

[Richary]

It certainly started building up as it got closer to me at Rydalmere, and we had quite a few close CGs and Intracloud bolts. Also some quite heavy rain from about 1pm. Only about 10mm all up though.

[Macca]

Fairly LARGE storm heading through the Hunter at the moment.  I'd suggest this would have some severe characteristics given its size, the environment is it in and the ENE'ly movement (deviating to the left) over the last hour or so.  Looks like a nice HP monster and would probably make for some nice photos if you were close to it.

Macca

[James]

View of the northern part of the line that developed over Hornsby. Shot taken around 2pm'ish (would have been up near Gosford). Soccer game was delayed by 30 minutes as the base forming above unleashed some hefty CG's.

Some very nice lean in the towers indicating good vertical wind shear.

     

Am off to Brisbane tomorrow so fingers crossed for some more up there.

[Steven]

While heading out this afternoon, there was some interesting towers going up around the place and to the west was quite a bit of high cloud, although I assumed these were just showers from cumulus's, nonetheless I was a little surprised to see the forecast for a possible thunderstorm, GFS predicts moderate to strong instability close to the coast, bring it on I say.

Steven

[Richary]

The Hunter storm is looking very nasty - especially the 0730 UT image.

[Steven]

Seems to have sustained itself in the last few scans, definitely a violent core, I hope those people near Forster brace themselves.

Looks to contain large hail, heavy winds and rain and maybe even microbursts!

[James]

That crappy looking line teased with a sporadic CG every few minutes as it made its way from the Richmond towards Glenorie around 730pm. I persisted for 45 minutes until the rain started to fall and the CG's dried up. So what does every good storm chaser do when this happens... pack up and head home. I got as far as packing everything into the boot when all of a sudden a blinding flash filled the car. Sure enough 6 seconds later that all too familiar crack ripped through the atmosphere. In the next 2 minutes more than 10 CG's hit all around Middle Dural/Glenorie, not enough time for me to get the camera and tripod out. One hit some sort of substation and made that lovely eeirie green glow for a few seconds afterwards.

Without a tripod, sticking the camera out the window I managed to capture this. Not a bad effort if I do say so myself 

   

[Richary]

Nice photo! That 2nd line of storms hit here a bit before 7pm though all the lightning action was up in the clouds rather than CGs. Another quick 15mm of rain. Certainly wasn't severe though the rain would have made driving a bit tricky.

[Harley Pearman]

Hello

Sydney Thunderstorm 13/4/2008

Heavy early morning fog over western Sydney clearing by 8 am. At 10.30 am, I was observing thunderstorm cells sitting over the Blue Mountains.

I have never seen unusual weather like this before in Autumn where fog clears and 3 hours later, thunderstorms start developing on the ranges to the west. This does not give allot of available time for daytime heating for powering thunderstorm cells. Yet, this happened.

I could not take any photos because I had to be in the city to attend the PIA Conference on climate change and urban planning and topics such as thunderstorms will be discussed.

What I noticed about the storm event of 13/4/2008 is that prior to the thunderstorm, large clusters of alt cumulus castellatus clouds pre ceeded the thunderstorm cell.

It appears the storm traversed through Sydney's west early afternoon but did not drop allot of rain. Falls of 5 mm at Blacktown, 6 mm at Penrith occurred.

However, east of Blacktown, it appears the storm intensified. Some rainfall totals were 28 mm at Granville, 23 mm at Turramurra, 28 mm at Sydney Olympic Park, 10 mm at Sydney and 16 mm at Chatswood.

I was in the city and I observed up to 12 cloud to ground lightning strikes including one on a city skyscraper. The storm was very active including significant intra cloud lightning and almost continuous thunder for a period. The storm was pre ceeded by a large lowered shelf cloud travelling NNE and stiff but cold southerly winds and then heavy rain. No hail fell. The storm cell had cleared out to sea by 1.40 pm.

A weaker thunderstorm moved through Sydney's eastern side at 7 pm bringing a further heavy shower but less lightning.

Today I looked at the rainfall figures from it and the heaviest rain occurred within the Cumberland Basin west of the CBD. I am thinking about the behaviour of this storm and my conference that I am attending and I wonder if the urban heat island effect created by the city may have played a role in intensifying the storm or rainfall over the built up area of Sydney.

This is a topic that will be covered in the conference and I will provide a discussion thread on this at a later date.

Harley Pearman