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Severe Thunderstorm Outlook - Sat August 9th

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Author Topic: Severe Thunderstorm Outlook - Sat August 9th  (Read 288 times)
martinastro
Martin Mc Kenna
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« on: August 09, 2008, 11:56:26 am »



From Tony Gilbert

11.30am Sat

Slight Risk of Severe Thunderstorms Ireland through to Northern UK & SW Scotland 12Z Sat 9th Aug-03Z Sun 10th Aug

Moderate Risk of Tornado Development same period. Transitional as per convective map below.

Recent and quite dramatic changes in the models highlight a period of risk for severe thunderstorms and tornado development within the post frontal trough. UK & Ireland will likely see prolonged periods of rain within the range of the cold front. UKMO forecast synopsis suggest the development of a strong surface trough in the wake of the cold front bringing further thundery showers to highlighted regions afternoon and overnight. Sharp upper troughing encourage lift and increases lapse rates through period. Polar maritime feed from the west sustains a good consistant flow of moisture at surface within a highly unstable environment. Strong upper and low level jet increase vertical shear numerically and steadily with height giving perfect balance of updraft to downdraft exchange. Weak surface winds allow for notable veer and strong speed shear in the lowest layer and is plotted within the red boxes. Current models push lift marginally into the warm sector so outlook requires constant monitoring for any changes. ATM I am very encouraged by vertical moisture distribution allowing for the best possible scenario for potential instability.

Prime risk today is based on the serious risk of tornado development and hense attributation the risk of categorized severe thunderstorms. Moderate CAPE and medium level freezing levels will suggest moderate hail possible. Dry air mid levels allow for strongest levels of gust possible. Based on mean average gust calculations between 800mb and 600mb this suggest up to around 40kts possible ATM.


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martinastro
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« Reply #1 on: August 09, 2008, 05:12:21 pm »

ESTOFEX are giving us a level 1 this evening.

http://www.estofex.org/
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martinastro
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« Reply #2 on: August 09, 2008, 09:39:34 pm »

Been out watching until around sunset from a great location. Convection is elevated here, nothing substantial but very unstable looking. Some heavy showers and mammatus but no 'beefy' convection to speak of. Quite photogenic skies. Pity nothing happened. I thought with a level 1 something might have happened. Maybe lack of ground heating didn't help things in the north.
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brianb
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« Reply #3 on: August 09, 2008, 10:30:06 pm »

On the way back from Carnfunnock I noticed a distinctly beefy lump of convection which was CuNim but with a smooth rounded top rather than the usual anvil. There was definitely heavy rain falling from it (from a few miles NE of Ballymena stretching over the plateau to the NE, at 1635 BST) but no signs of electrical activity noted.

To the north of this the ground was wet and the air seemed to be cooler. At Carnfunnock it was 24C by the not very accurate thermometer in my car (warmed up 6C driving down the coast road from Ballycastle) and it was approx. 30% sunny and humid but dry ground despite the morning rain.
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