Astronomy, Photography and Weather

General Category => Weather & Atmospherics => Topic started by: martinastro on July 17, 2008, 06:30:52 pm



Title: Thunderstorm Outlook - Fri/Sat 18/19th
Post by: martinastro on July 17, 2008, 06:30:52 pm
From ESTOFEX

(http://i35.tinypic.com/33cw4ll.png)

Storm Forecast
Valid: Fri 18 Jul 2008 06:00 to Sat 19 Jul 2008 06:00 UTC
Issued: Thu 17 Jul 2008 13:08
Forecaster: TUSCHY

There is a chance for a few organized storms between a 00Z - 06Z time - frame over NE Ireland and northern / central parts of UK as a strong upper trough crosses the area from the WNW. Very limited instability release precludes any higher probabilities at the moment.


Title: Re: Thunderstorm Outlook - Fri 18th
Post by: brianb on July 17, 2008, 09:10:58 pm
Nah, won't happen. I get migraine when it's going to thunder.


Title: Re: Thunderstorm Outlook - Fri 18th
Post by: martinastro on July 17, 2008, 10:08:34 pm
LOL. An expert told me that the above forecast is meant for the early hours of Saturday night although you never know between now and then. There are some intense showers moving in from the Atlantic over Scotland due to hit N. Ireland much later tonight. I will see what the experts think of the true potential closer to the time. Instability is not great at all but there is good vertical wind shear so any cells that do manage to develop could be quite well organized although forecasting these things is as much art as science.

Will wait for the next update.


Title: Re: Thunderstorm Outlook - Fri/Sat 18/19th
Post by: martinastro on July 18, 2008, 11:16:57 am
Netweatherforecast...

(http://i33.tinypic.com/2vxnbjt.jpg)

Synopsis
BY 12Z FRIDAY, LOW PRESSURE OF 997MB IS EXPECTED CENTRED NEAR WESTERN ISLES TRACKING EAST THROUGH AFTERNOON, WARM FRONT AFFECTING NE SCOTLAND MOVES EAST INTO NORTH SEA, WHILE COLD FRONT STRETCHING FROM ELGIN SW THROUGH LONDONDERRY AT 12Z MOVES SE TO BE OVER NERN ENGLAND BY EVENING, MOST OF THE UK IN WARM SECTOR FRIDAY AFTERNOON, WITH TROUGH MOVING EAST IN WARM SECTOR ACROSS ENGLAND AND WALES. BY 00Z SATURDAY, LOW IS EXPECTED JUST EAST OF ORKNEY ISLANDS WITH COLD FRONT STRETCHING SW THROUGH EDINBURGH-ANGLESEY-ST. DAVID MOVING SE FOLLOWED BY TROUGH MOVING SOUTH ACROSS SCOTLAND.

...1200Z-2000Z FRI OVER SERN SCOTLAND, N. IRELAND, NERN, CENTRAL AND ERN ENGLAND...

STRENGTHENING CYCLONIC UPPER FLOW AND STEEPENING LAPSE RATES OVER NERN AND CENTRAL UK WILL SEE WARM SECTOR AIRMASS BECOME INCREASINGLY UNSTABLE HERE, IF SUFFICIENT INSOLATION OCCURS IN THE AFTERNOON - SCATTERED HEAVY SHOWERS AND ISOLATED THUNDERSTORMS ARE LIKELY TO DEVELOP ESPECIALLY INVOF OF SURFACE TROUGH MOVING EAST ACROSS ENGLAND DURING THE AFTERNOON ... ALTHOUGH 30-40 KTS OF DEEP LAYER SHEAR AND MODEST LOW-LEVEL SHEAR ARE FCST - INSTABILITY MAYBE LIMITED GIVEN RELATIVELY WARM MOIST PROFILES ALL THE WAY UP ON FCST SKEW-TS SO ANY CONVECTION IS UNLIKELY TO DEVELOP SEVERE POTENTIAL. NON SEVERE GUSTY WINDS AND HEAVY DOWNPOURS ARE MAIN THREAT.

...0000Z-0600Z SAT OVER N. IRELAND, SERN SCOTLAND AND NERN ENGLAND...

STRONG UPPER TROUGH MOVES IN ACROSS THE AREA FROM THE WNW OVERNIGHT INTO SATURDAY MORNING FOLLOWING BEHIND SFC COLD FRONT MOVING SE, UPLIFT OF FAIRLY MOIST MARITIME AIRMASS ALONG NERN END OF COLD FRONT WITH HELP OF FORCED ASCENT ON ARRIVAL OF UPPER TROUGH WILL LIKELY LEAD TO HEAVY CONVECTIVE RAINFALL OVER THIS AREA WITHIN THIS PERIOD, ISOLATED T-STORMS MAY POSSIBLY DEVELOP WITH THREAT OF HAIL AND GUSTY WINDS - AS DRY AIR INTRUSION ARRIVES ALOFT FROM THE WEST WITH ARRIVAL OF UPPER TROUGH AND MIXES DOWN IN ANY CONVECTIVE CELLS. DEEP LAYER SHEAR WILL TEND TO WEAKEN FROM THE NW DURING THE NIGHT BUT SOME ORGANISED CONVECTION MAY STILL DEVELOP, SOME MODERATE LOW LEVEL SHEAR IS ALSO INDICATED ... HOWEVER, LACK OF INSOLATION WILL TEND TO LIMIT INSTABILITY SO WILL NOT WARRANT A SLIGHT RISK OF SEVERE WEATHER FOR NOW. AN ISOLATED WEAK TORNADO CAN'T BE RULED OUT HOWEVER.

Issued by: Nick F - Senior Forecaster for Netweather


Title: Re: Thunderstorm Outlook - Fri/Sat 18/19th
Post by: martinastro on July 18, 2008, 11:50:50 pm
Heard the risk is now reduced but still possible. Large cumulonimbus cell on my northern horizon after sunset and into evening twilight when Capella appeared, with mammatus.