Topic: Thursday 16th February 2006 - Upper Trough

[Jimmy Deguara]

Hi,

There is the potential of severe weather again based on the current 00Z GFS model output. A cold pool is anticipated to drift across during the afternoon period to be over Sydney tomorrow night. There is rapid destabilisation and given the upper level wind profile and dry air aloft, there exists the possibilities of very large hail, very heavy rainfall and damaging winds. The negatives are the lower level wind profile which does not seem to back winds. Another negative is the relatively weak 700hPa level cap due to cooler temperatures. Regions that could be affected by severe weather extend in the eastern third of NSW and Victoria during the afternoon period.

I guess we shalt wait for the outcomes of the progressive models as to what eventuates.

Regards,

Jimmy Deguara

[Jimmy Deguara]

Hi,

The 06Z data has maintained the pattern with higher instability further north west.

Regards,

Jimmy Deguara

[David C]

Wow, that is some nice destabilisation between 3 and 12z - with moisture in place it is inconceivable that this cold pool wont produce some severe storms across the region tomorrow.......erm,,,,isn't it hehe. According to GFS, there seems to be potential for advection of drier air for  Sydney contributing to less instability, during the afternoon - it remains to be seen whether this persists with subsequent runs. In anycase there surely will be something through the evening locally.

[Jimmy Deguara]

Hi David,

12Z data released and the cold pool still exists but passing just slightly south of Sydney at 12Z.

I guess mismatch once more - the best destabilisation is on the south coast and there is some backing in the lower layers on the southern portion of the low. However, will there be sufficient moisture in this region!

There is great instability early in the Central West but it is a concern why such instability is not sustained. Perhaps drying? There is a pattern that promotes high CAPE further north and up to the Central Tablelands but it remains to be seen as to where the storms organise.

The dry slot seems to be passing through 34S north and northwestwards by 06Z.

Regards,

Jimmy Deguara

[Jimmy Deguara]

Hi,

Another thing I noticed is rapid destabilisation early near Parkes which explains the higher CAPE early in that region!

Regards,

Jimmy Deguara

[Jeff Brislane]

I couldn't help but notice the date today, and yes Jimmy you got it wrong. It's actually thursady February 16th. Who's for a reunion party?

Btw on an unrelated topic I met someone recently who corepunched a supercell un-intentionally on the M4 on a certain day in November 2000. More on that later.

Jeff.

[Geoff Thurtell]

Yes, another 16 February event.

Unfortunately my father is back in hospital so I cannot use my leave time to go out on a chase. Jimmy left just after 6am this morning.

I will keep my camera with me and hope for the best.

Jeff, you will have to fill in the details on the November 2000 encounter!

Geoff

[Jimmy Deguara]

Hi,

Yes I had to leave early in order to try getting there in time for the probably early action. It turned out to be elevated convection - some loud thunder but crap structure.

We then found ourselves leaving the early pre-trough environment and remained in sunny skies for a little while near Wellington. Of course there was a cumulus field. Shock horror there was a NE-N windstream persisting and feeding high dew points and ensuring low bases. Obsviously there also was a low pressure region. Storms from the Central West moved through towards Gulgong and although the initial structure was consolidated the storms were weakening by the time they got to us. Some brief lightning shots and timelapse video the only way the trip could salvage a bust situation.

Regards,

Jimmy Deguara

[David C]

Hi Guys,

The storm that came over Sydney put out a shelf cloud but was basically garden-variety tropical stuff. Some lightning but not intense, weak winds with passage of the gust front and moderate rain.