Storm Forecast Issued: 2009-08-18 21:28:00
Valid: 2009-08-19 00:00:00 - 2009-08-19 23:59:00
Regions Affected
extreme Southeast England ( all of the UK, excluding Outer Hebrides and SW England are including in the WATCH )
Synopsis
A complex area of LOW pressure between Scotland and Iceland, and a large area of HIGH pressure over the continent will dominate the weather across the United Kingdom on Wednesday. Ahead of a cold front, aligned through central Scotland and the Irish Sea at midday Wednesday, a very warm and humid airmass is advected northwards from France. A strong cap appears to be present over France for much of the daylight hours, preventing convection from occurring - however, during the evening hours the pressure gradient over northeast France is expected to slacken, creating a surface LOW to develop. This may cause initially scattered or isolated thunderstorms to develop. There is a risk of one or two of these clipping the extreme southeast corner during the mid-late evening hours - this is uncertain due to disagreement between the models. Later in the night the storms are expected to expand and merge into an MCS-type feature across Benelux and the southern North Sea. These storms pose a risk of supercellular characteristics. Elsewhere, although some heavy and locally torrential pulses of rain are expected to move northeastwards along the cold front, the risk of embedded thunderstorms seems unlikely given rather limited cloud height.
