Forecast Update
Valid: Fri 04 Jan 2008 17:00 to Sat 05 Jan 2008 06:00 UTC
Issued: Fri 04 Jan 2008 17:01
Forecaster: TUSCHY

SYNOPSIS

Please refer to the outlook issued at Thu 03 Jan 2008 22:24 .

DISCUSSION

...English Channel and surrounding areas...

Current radar observations show a more or less broken line of showers / thunderstorms, reaching extreme SW-UK.
The main reason for updating / upgrading southern UK is the latest VWP data. Camborne, just ahead of the line has a significant increase in both, speed and directional shear. Veering mainly at lower levels is quite impressive and so are the 60kt just above the surface. Those facts and the current radar presentation support higher confidence that wind gusts could reach our criterion, although more localized.
The tornado risk should be maximized along the coastal area where LL lapse rates are somewhat steeper, BL moisture is richer ( dewpoints along the coast reach 7-10°C ) and the LCL remains low. In addition, internal processes along the line could be the focus for a locally enhanced tornado threat.
As a result of the potential instability release to occur far inland, the level-1 was extended quite far northward, too.

Activity over NW France should be confined to the postfrontal airmass, where helicity values drop off rapidly and hence no level area was included.

We made some changes to the rest of the outlook to reflect main thunderstorm activity over the central Mediterranean.