Astronomy, Photography and Weather

General Category => Weather & Atmospherics => Topic started by: martinastro on August 02, 2008, 09:07:57 pm

Title: Thunderstorm Outlook - Sun August 3rd
Post by: martinastro on August 02, 2008, 09:07:57 pm

From Tony Gilbert, issued 8.22pm Sat

Slight Risk Gen Tstorms N.Ireland & Northern UK regions 09Z-21Z Sun 3rd Aug 08

Remarkable similarities to today's outlook (Sat)!

Further surface troughing expected to initiate thundery showers for said regions throughout Sunday. Overlap of shear to instability at this time looks almost non existent so much less aggressive convection likely. Less PVA and dry air mid levels suggest sharp convection unlikely. GFS does advect better moisture into the region hense the projected moderate CAPE values suggested.

Overall risk seems rather low category, given the lack of shear and lack of convergence. Funnels look rather remote IMO. Slightly deeper upper trough and better moisture at surface however do give a fairly good chance for more thunder, atleast.

Title: Re: Thunderstorm Outlook - Sun August 3rd
Post by: martinastro on August 03, 2008, 10:40:47 am

Update from Tony Gilbert. 10.20am Sun UPDATE

As per earlier forecast.

Given the lack of shear, storm motion is expected to be rather slow. Such conditions typically produce a large area of cold outflow at surface which gradually spreads out from the core. The end result might see some thunderstorms initially, and then lapse rates will weaken rapidly. With this in mind the best activity looks to be wherever the first lot of convection develops.

From Paul Blight...

The 00Z Castor Bay Ascent indicated decent amount of CAPE and Pr Water below 700mbs, but with an inversion above 700mbs, therefore thunder is perhaps less likely than yesterday, but with still scope for Heavy Rain from some of these Showers across S Scotland and N Ireland and N England. If temps can rise a bit and with some additional uplift - Sperrin Mountains or the Southern Uplands- then Isolated Thunder is possible.

Even further south across the Midlands there is some CAPE below 700mbs - with some capability of some heavy downpours assoc with the Tm Airmass across England which is cooled by the approaching upper trough, (destabilise SMZ)