martinastro
Martin Mc Kenna
Global Moderator
Hero Member
Posts: 5182
Maghera, N. Ireland
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« Reply #75 on: November 18, 2009, 11:01:54 pm » |
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UKww Weather Warning for Heavy rain and severe gales
Issued Wednesday 18/11/2009 0700BST
Areas affected: NW half of Wales, NW England, SW & W Scotland, N Ireland
Valid from: 0700GMT Weds 18th November - 1800GMT Fri 20th November
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General evolution:
The weather during this Warning period will be dominated by a major, deep (960mb Thurs 1200) Atlantic low pressure system that is drifting slowly NE towards the gap between the UK and Iceland. On its southern flank, a conveyor of warm, moist SW winds has become established and a series of frontal waves will run along this feature during the forecast period. High pressure over Europe means that a steep pressure-gradient will remain a feature throughout.
Forecast: Wet and windy sums up the forecast with gale to severe gale-force winds causing problems at times: however, the key feature is the prolonged rainfall that will occur, pretty much continuously through towards the end of the forecast period. Latest model guidance suggests totals of 50-80mm for North Wales and, more particularly, 90-130mm for the Lake District and hills of SW Scotland: adding in a factor for enhancement over the mountains and these figures could be exceeded by 50% or more giving 150mm+ in places. The ground is already saturated so that run-off will be very high, leading to widespread standing water on roads and rivers/streams in full spate. Prone flood-plain areas are very likely to see serious flooding leading to disruption especially into the second half of the forecast period. Road travel is likely to be adversely affected and driving conditions will be hazardous throughout the period.
This forecast period ends on the evening of Friday 20th November but readers should be aware that another round of severe weather looks likely to strike over the weekend with very windy conditions a cause for concern - more on that nearer the time.
Issued by JSM for UKww, 0700GMT 18/11/2009
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