Message #625

[martinastro]

From UKWeatherworld...

There is nothing in the 12Z Suite of model guidance that goes against earlier ideas.  WV imagery shows the major longwave trough currently to the west of Iberia. Ahead of this an area of advancing high WBPT air is moving north (showing marked Mid level instability already to the west of Biscay.  This plume moving NE and merging with the plume already in the N Sea and effectively expanding the area to cover England by tomorrow evening. Greater than 18C WBPT air in the SE by then so quite juicy to say the least.

Aforementioned trough swings NE and extends then partially disrupts leaving an active part of the trough and slow moving upper level low over the Celtic Sea by 00Z Tues. THis is quite a complex development.  Large scale ascent takes place ahead of this trough with large amounts of PVA at 500 and 300mbs and large scale 700mb Vertical Velocity, this effectively meaning that above this plume, the airmass will be destabilising and become very unstable. 

During the afternoon Surface Convection may develop from London up through the Midlands to NW England and Wales (temps again nr 30C) spawning scattered T-Storms and downpours.  More general cloud dervied from an ELevated Moist Layer will move NE towards the SW.  Models are consistent in at least one MCS developing over N France and swinging NW. It is unclear whether this will be derived from the B/L however given the type of event and time of day it seems likely that most of the activity coming NE tomorrow evening and night will be from Mass synoptic ascent and therefore derived from above the B/L. However feeding from possible homegrown events means there may be a mixture.

Even Global Models and their limited resolution are indicating 20-30mm falling in some places within a few hrs and up to 50mm is possible in isolated spots in a 6hr period.  Locally Gusty winds and Strong Thunderstorms are possible if MCS's develop and move N.  Isolated Hail is possible =if= any severe storms develop.

Rain will move NE into Tuesday with increasing trends towards a curling occlusion developing bringing more rain into the SW and Wales on Tuesday.

From Tony Gilbert...

Whilst further general thunderstorms are on the cards for Monday. Once again initial convection is likely to be delayed well past the suggestion of the GFS model. Upper saturation inhibits potential instability and surface temps are less that what we saw for Sunday. So low level lapse rates may be less than what we saw today (Sun). An environment of weak shear and less convergence will all but preclude any severe weather potential. GFS are once again overdoing the CAPE.

Storms likely to be more wide spread across UK and NW Ireland but I see limitations here!

PS. Watch out for Tues is my advice!