Topic: NSW & S Qld Severe Storms: 11-14 September 2008

[Michael Thomas]

Well, I think a new tread should be started about the possibility of storms in NSW for the Friday and extending into the weekend. GFS has consistently been forecasting instability to develop later this week but I will stick to the latest 12Z run for this discussion. Friday, looks somewhat interesting with quite good wind shear and LI's around the -3 mark. At this stage though it is really Saturday that is catching my interest. There should be some decent moisture with the deep N'ly winds and with cold air aloft LI's are forecast as low as -6. Hopefully this is not based unrealistically high surface dp's. Interestingly, a dryline is present on the 12z run in the NW of the state. Ahead of the dryline, the LCL's are pretty high so expect some high based storms with small hail to form. Here's a forecast sounding for that region-

http://soundings.bsch.au.com/skew-t.html?source=ncep&lat=-29.98&lon=145.08&date=2008091306&gribdate=2008091012

Another area of interest is the South West Slopes region. 850 hPa winds are around 20-30 knots from the north. It is quite rare in Australia to see such strong N'ly winds at this level. It appears to me that there is a warm front aligned E-W associated with this deep flow of warm moist air. If this is the case we may have the chance of a few storms forming along the warm front (if there is one). Here is a forecast sounding for that area-

http://soundings.bsch.au.com/skew-t.html?source=ncep&lat=-35.63&lon=146.72&date=2008091306&gribdate=2008091012

It's easy to read too much into this but there are E'ly winds in this area. This extra turning does wonders for low level shear. This is probably the region I would suggest that has a chance of severe storms forming.

Sunday, the upper level winds really start to increase but directional shear is gone as surface winds tend NW'ly. I suspect that widespread rain and embedded thunderstorms will be all that results, though, hopefully I am wrong.

Anyway, spring is here and let this be the start of a great storm season,

Michael

[Michael Bath]

There's quite a different in the precip forecasts for Saturday afternoon between GFS and LAPS.  GFS is favouring far western NSW (later on) and SE QLD away from the coast, while LAPS certainly favours most of eastern NSW and inland S QLD.

Certainly a few interesting days coming up, and even today may see something along the coast strip in NE NSW and SE QLD - most likely evening.

[Jimmy Deguara]

Michael and Michael,

I have been looking with interest at the system and the good thing is the moisture profile is quite decent for this time of the year given the weak cap at 700 (0 degrees at 700hPa level). Let's hope that storms do not become too numerous but then again why whinge, a storm is a storm this early in the season and the conditions as described by Michael is quite decent for early September.

Michael B, the concept of precipitation differences is merely for the rain bands that will follow as the system drifts across I guess. I would have thought Sunday was a go when I last checked but Saturday is definitely looking a half decent day.

Regards,

Jimmy Deguara

[Michael Bath]

Storm cell has been almost stationary over the Tweed Heads area and just offshore for the past 90 mins. Lightning is every 10-30 seconds. Barneys Point has received 42mm in a short time. There was a report of hail at nearby Banora Point.

[enak_12]

Putting up some pics from last night (11'th) just a little bit of lightning this far south hoping for more storms today.

[Michael Thomas]

Quite a surprise that storm off Tweed Heads. It actually looked rather impressive on radar for a while. Here is a the radar loop of the storm forming and staying stationary of the coast. Storms continued off the coast much longer after this as well.

---> Brisbane radar loop

Jimmy, earlier Sunday certainly looked the better day but now GFS is really favouring Saturday in terms of instability, still a few days out so we'll have to wait. I'm just hoping moisture can make it down to the border region in time for Saturday afternoon. We need about an 15 degree increase dew point temperature between now and then, hopefully that's not asking for too much.

Michael

[Michael Bath]

This first photo was at 5.30pm when cloud tops finally managed to push a bit higher. This continued on as part of the Tweed Coast storm.



Mid level cloud and the nearly full moon made the lightning pics a bit washed out looking.







The radar accumulation is interesting and pretty much matches the radar loop times above. I've seen storms stay in generally the one location for extended periods previously, but the situation last night was one of the most impressive cases.



MB

[David C]

GFS overcooked the dewpoints for today, which contributed to the somewhat inflated convective energy progged for late afternoon (ie LI -6, CAPE 1600) in / around southwest slopes.  From tonight on, the moisture influx looks reasonably solid for a round of severe storms Saturday over a wide area of NSW. Should be interesting if those dewpoint depressions are minimised and strong low level flow is realised -- never know what might happen.

[Jimmy Deguara]

David,

The progged conditions look good on paper - good turning of the winds, reasonable shear, and excellent low level shear. The only negatives - the target on the GFS 00Z has shifted farther west and there is a ridging in place further NW. This should not have too much of an impact given the upper level temperatures. However the moisture is the key as David suggests.

Will be taking out Imelda and Kimberly on their first chase:)

Regards,

Jimmy Deguara

[Rodney Wallbridge]

Gyday all, here are a few pics from tonights thunderstorm which went past Lismore.Managed to get out to the south side of town for a pretty nice show!Spring sure is here!It was interesting watching this coming up from the south around sunset as it was allready going soft.But then i took another look and a new updraft would peak up over the others.
 
 
 
 
 
 

[Mike]

Finally some pics!  Some nice structure to those thunderstorms and nice to see Enak got some star trails with the long exposures!  Looking forward to any more photos guys, hope you managed all to go chasing.

[Ben]

Great stuff Mr Wallbridge!!!! Looks like a tasty storm there, even at that stage of its life! :D Can definitely see it is outflow dominant, but that upper kinda curved base structure suggests it could have exhibited a nice meso on it earlier I would say! Great pics again!

[Jimmy Deguara]

Very nice structured storm - what a surprise event!

The situation for today defies belief - I mean do we believe that moisture can recover to that magnitude? Unless rain is going to occur and increase the dew points though the temperatures are going to decrease in this region. I am concerned about the cooling that exists further east of the Central West according to the models. The dew points should merely make it to say the early teens rather than the mid teens.

The models also somehow do not form an agreement. So I think it is the typical early risk chase one would anticipate in September - you head out and hope for the best!

Regards,

Jimmy Deguara

[James]

If a miracle happens and moisture does recover then some parts of NSW could be in for some great storms. Not often you see a forecast sounding with such nice wind shear.

[Rodney Wallbridge]

Gyday all, Dorrigo area might spawn a nice storm today...which hopefully might stay together for a visit into the Northern Rivers.  I'd like to be sitting at Tamworth today perhaps things might go really nice out that way in a band southwards towards Orange. Be interesting  to see some nice isolated storms!