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Female
UKASF
Areas Affected:
SLGT: C + CS Scotland, Pennines, W + S Midlands, Cumbria
Synopsis:
Strong capping beneath upper ridge will inhibit deep convection, but isolated convection may occur in response to daytime heating and orographic forcing.
Discussion:
As LSTs rise sharply, >1400J/kg CAPE is likely to build up. However, with a distinct lack of forcing and strong capping at 950mb due to a warm nose, primary focus then turns to either convergence from seabreezes, or orographic forcing, or ideally a combination of both. This seems most prevalent around the Solway Firth (Dumfries & Galloway and/or Cumbria), and over the Pennines where seabreezes and topography will play a key part in providing forced ascent and the potential for a few isolated showers/thunderstorms to form, but this risk is considered quite low (10-20%). Initiation time is likely to be quite late in the day once again.
Forecast soundings indicate a qute dry profile, so it is questionable as to how much precipitation such showers could produce. Nevertheless, PWAT >30mm locally combined with very light steering winds means locally a quasi-stationary cell could produce a significant amount of rain over a relatively small area - one to watch, perhaps.
Very week shear not only limits severe potential, but also suggests such showers (or storms) will become poorly organised, but given dry air aloft there could be some hail if any stronger cores can develop.
Several models also indicate high ground W + N of London (Chilterns primarily, and perhaps the Cotswolds) may also have the potential for an isolated sharp shower, but given lack of significant topographic forcing and/or convergence, for now we ignore this idea.
http://ukasf.co.uk/storm-forecasts/172
The Netweather stormrisk:
http://cdn.nwstatic....ukstormrisk.png
then there's this:
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http://131.54.120.15...STORM-STANDARD#
maybe a forecast to come from Nick F and Brickfielder later!
Good luck everyone!
