Forecast Update
Valid: Thu 04 May 2006 14:00 to Fri 05 May 2006 06:00 UTC
Issued: Thu 04 May 2006 14:51
Forecaster: GROENEMEIJER

SYNOPSIS

See convective forecast...

DISCUSSION

The 12 UTC soundings from Britain showed very steep lapse rates in the 900-700 hPa range, but a rather strong capping inversion, too. Present thinking is that the cap will probably remain too strong across southeastern England to allow for convective initiation there, although this cannot be completely ruled out.

It is more likely that convection will initiate across northern and northwestern parts of England, southern Scotland and Wales, where CIN is a little lower and some forcing for upward motion is expected to overspread the area during the remainder of the afternoon and evening.

Across western Wales and Scotland, any storms will likelybe elevated.

Wherever surface-based storms develop, large hail appears to be a large threat given the very steep lapse rates observed right above the freezing level. Additionally, rotating updrafts/supercells may well form given 0-6 km bulk shear of around 20 m/s.

Especially across the northern part of the level 1 area, a threat of tornadoes will exist as well, given that low-level winds back strongly with height and large storm-relative helicity can be expected.