Slight Risk of Isolated Thunderstorms 09Z-21Z Ireland & Central UK Regions
Confidence Level; Medium
Low remains just NE of UK in quasi stationary state. Long wave upper trough moves east generating lift and increasing lapse rates. Strong jet stream with a west to east axis increases upper support to convection building closer to the southern sector of the convective box. UKMO currently forecast a surface wave follow by post frontal troughing later in the day.
WRF much less confident than GFS ATM. GFS builds strong instability as lapse rates increase through the day with up to 900 J/KG predicted. Front left exit region of the jet stream look divergent and should increase lift for a time primarily central UK. A number of mid level PVA max's look to run along this diffluent zone increasing upper dynamic lift further. GFS also predict a layer of dry air above the boundary layer where cooling of cloud tops may be enhanced for a time. Low level speed shear somewhat limited but certainly some veer along a line from N.Wales through to the Wash. There may be some scope for a tornado risk in association with the surface wave though this will need to be assessed on Weds.
This post has been edited by Tony Gilbert: 17 July 2012 - 18:34