Monday, August 24, 2009

Extratropical Storm Bill Heads Towards the British Isles




From 1800 UTC Tue 25 Aug to 1800 UTC Fri 28 Aug

By midnight Wednesday the Atlantic will be dominated by ex-tropical hurricane Bill which will be at 52N 15W turning northeastwards into Western Scotland by midday Wednesday. As this low fills and moves away towards Iceland on Thursday, another low pressure forms and moves to 55N 17W by midday Thursday. This low moves to 59N 11W by midday Friday with central pressure remaining constant. Elsewhere a shallow low and frontal system will remain slow-moving across Scandinavia and the Baltic region. Although winds start below limits they increase to become strong south to southeasterly by midday Wednesday across all areas, perhaps reaching gale-force for a time in Forties, Viking and Fair Isle. Winds veer westerly by Thursday morning and slowly decrease for a time. By Friday morning strong southerly winds have again developed across Forth, Forties, Fisher and areas northwards. As winds decrease across these parts during Friday they increase to become strong west to southwesterly across Tyne, Dogger, German Bight and areas southwards

Niton

From 1800 UTC Tue 25 Aug to 1800 UTC Fri 28 Aug

By midnight Wednesday the Atlantic will be dominated by ex-tropical hurricane Bill which will be at 52N 15W turning northeastwards into Western Scotland by midday Wednesday. As this low fills and moves away towards Iceland on Thursday, another low pressure forms and moves to 55N 17W by midday Thursday. This low moves to 59N 11W by midday Friday with central pressure remaining constant. Visibility will be mostly moderate or good but poor at times in rain and drizzle. Strong south to southwesterly winds affect most areas Tuesday night west of Portland and Lundy. Winds generally veer westerly during Wednesday and decrease by the end of the day. Southwesterly winds then pick up again from midday Thursday in Shannon, Fastnet and Sole and later north-western parts of Fitzroy. Winds remain strong and veer west to northwesterly during Friday and extend into the Irish Sea and Wight. Visibility will be mostly moderate or good but poor at times in any rain or drizzle

Portpatrick

From 1800 UTC Tue 25 Aug to 1800 UTC Fri 28 Aug

By midnight Wednesday the Atlantic will be dominated by ex-tropical hurricane Bill which will be at 52N 15W turning northeastwards into Western Scotland by midday Wednesday. As this low fills and moves away towards Iceland on Thursday, another low pressure forms and moves to 55N 17W by midday Thursday. This low moves to 59N 11W by midday Friday with central pressure remaining constant. Strong southerly winds back southeasterly Tuesday night before veering westerly by midday Wednesday. West to southwesterly winds increase to gale-force in Hebrides, Fair Isle and Faeroes later on Wednesday and stay gale-force overnight. The gales move away later Thursday but a strong south to southwesterly wind remains across most areas except for Southeast Iceland where winds veer northwesterly. Westerly winds remain strong from Bailey and Hebrides southwards through Friday but become cyclonic over Southeast Iceland and Faeroes. Visibility will be generally moderate or good but poor at times in any rain or drizzle

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Warning UK regions:

Northern Ireland

North West England

SW Scotland, Lothian & Borders


Warning

Heavy Rain Wed 26 Aug
There is a moderate risk of severe weather affecting parts of Northern Ireland, southwestern Scotland and Cumbria on Wednesday.

A band of locally very heavy rain will move northeastwards across Northern Ireland during the early hours of Wednesday and will spread across Cumbria and southwestern Scotland in the morning before clearing away during the afternoon. Accumulations of between 20 and 40 mm of rain are expected in a short period of time, with a few spots receiving around 60 mm.

Issued at: 1130 Mon 24 Aug

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