Australian Severe Weather Forum

 GFS has some CAPE sitting in the central tablelands or the Weather co predict is the Hunter on thursday , but i wonder if the moisture will be wiped out like the last couple of times , at the surface it seemed to be a northerly and has some ok dewpoints but i dont see anything stopping those storm killing north westerlies.

I'm thinking that it's going to be a lot less spectacular than GFS is suggesting at this stage Nick, but would be happy to have been proven wrong come Friday morning. Clearly GFS has almost no handle on the boundary layer moisture in recent times eg cf. 18-20C dewpoints Friday versus LAPS progged 10C dewpoints which looks more realistic given the synoptic situation. Based on form, I know where my money is. High-based storms at best for Friday; maybe some ok lightning.

Not that i've been able to follow the model progression very much over the last few days but I think it seems to be slowing down the front.  Current forecast for Sydney for Friday is for a late shower/storm but I'm more interested in Saturday late morning/early afternoon as the southerly comes up the coast and the upper levels are starting to get more interesting.  Timing is a massive factor here but if it can hold off until then, I'd think Sydney could get a nice early afternoon surprise on Saturday.  Wouldn't be the first time I've seen something like this.

Macca

Hi guys,
It'd be nice to be able to position a chase base around Canberra for the next few days! It would give nice access up and down the Hume and across to the coast! It's great to have the convection forecast up and running on WZ once again. It makes it quick and easy to correlate a few factors.
Might be worth leaving this thread open for Sunday or even Monday given things still might hold out for the Eastern coast as the system moves across the state through the weekend.

I hope you guys get another possible supercell chance! Lets hope the jet stream that's currently sitting in QLD gets a chance to move a little further South! (I haven't had time to check the charts for the weekend as yet)

A real touch of summer here today with temps pushing 36ºc but the Northerly winds are fairly dry.
Take care if chasing tomorrow! :D
Shauno

The models are continuing to find it hard to agree with systems with GFS playing silly buggers. Today there is a general thunderstorm outlook but I doubt worth much of a drive. This is noth the scenario one would have hoped for. With double de-merit points in NSW, definitely best to remain home unless a supercell attracts you.

Regards,

Jimmy Deguara

Hi guys,

Jimmy: what seems to be going on with GFS do you know at all? I've noticed a few complaints and obvious issues in the recent storm threads here.

We had a rather nice storm sitting to our SW last night. We had a moist NE wind inflow that kept the storm sustained and highly active for just over 3hrs! I noticed a lot of bright flashing while out walking at 8pm and it continued until I walked home again at 10:30pm. Seemed to be very active with a good large strike (lighting the whole sky) every 3seconds or so with smaller flashes in between. Once I reached the top of the hill just up the street from home I could see towering structure being nicely illuminated orange-ish due to the distance of the storm, which I would estimate at 100k's or so. Temps were still 25ºc at 10:35pm! At a guess I would have positioned the storm somewhere out between Cumborah (to our West) and Walgett. I saw the last flashes at 11:15pm just before I hit the hay.

If this is any indication of the lightning activity to come with this system (given conditions are similar tonight) it shouldn't disappoint!

Currently sitting at 35ºc here and it does feel a little humid. Winds are only very light if any at all so I can't give an accurate direction.

Take care,
Shauno

Shauno,

My complaints are merely realting to the moisture overestimation. And it is a significant difference. Moisture according to the GFS was anticipated to be 16 to 18C whereas realistically it was maximum13 to 14C. The higher dew points explains the high CAPE and very significant Surface Lifted Index reading.

We'll see how GFS handles further into the season.

Regards,

Jimmy Deguara

You've got to love the Dorrigo Plateau for storms. When no forecast or model thinks it's a chance, it always throws up something. Storms have formed near Point Lookout and Ebor.

And in the past hour, storms have erupted out west with plentiful lightning. Hopefully the storms will survive for a lightning show nearer Sydney.

Regards,

Jimmy Deguara

Starting to fire up. Fingers crossed.

Nice looking cell on the radar to the NE of Armidale as well.


SEVERE THUNDERSTORM WARNING
for DAMAGING WIND
For people in parts of the CENTRAL TABLELANDS, SOUTHERN TABLELANDS, CENTRAL WEST SLOPES, CENTRAL WEST PLAINS, SOUTH WEST SLOPES, RIVERINA, UPPER WESTERN and LOWER WESTERN Forecast Districts.

Issued at 3:02 pm Friday, 3 October 2008.

Severe thunderstorms are likely to produce damaging winds in the warning area over the next several hours. Locations which may be affected include Parkes, Griffith, Tibooburra, Cobar, White Cliffs and Ivanhoe.

A wind gust of 91 kph has been recorded at Moomba in South Australia, from a thunderstorm in a similar environment to those in NSW.

Yep GFS is awful at modelling daytime boundary layer conditions.

It's intriguing given that the model initial conditions should be well constrained by surface and satellite observations. And more intriguing given that it seems to do a marvellous job at modelling the upper atmosphere and that nighttime conditions are predicted quite well.

Narrabri is presently about 32 degrees with DP of 11 degrees. Whereas GFS predicted a max temperature of 26 degrees for 2m AGL and DP of 18 degrees.

It would be interesting to know more about what is going on from one of the GFS developers.

From the BoM 4:15pm today:
Forecast for Saturday
A few showers and the chance of thunderstorms. Moderate west to northwest winds ahead of moderate to fresh south to southeast change by the afternoon.
Picked it 3 days ago. Did you bring you camera down?

Dann

Nice lightshow on the N Shore tonight!!! Lots of CG's!!! heres a few. all can be viewed at http://www.flickr.com/photos/28009095@N05/

 

Thanks Ben - some lovely lightning there !!

Has anyone heard any reports of severe weather? the BoM had warnings out for damaging winds for most of the arvo and evening and that's not surprising given the speed the storms were moving.

Ben and I went up to his local oval which has great views, took me 20mins to get there which is a very good run through Pennant Hills RD. Was a very enjoyable send off just before my overseas trip (Tomorrow 11.20am). Here are my pics:

Click here for pictures



P.S. I have heard no reports of damage in the Sydney area, if anywhere would have got damage it would have been the oval we were on, and no branches/trees down... not really any strong winds at all. Just some nice lightning.