Forecast Update
Valid: Fri 23 Feb 2007 16:00 to Sat 24 Feb 2007 06:00 UTC
Issued: Fri 23 Feb 2007 16:11
Forecaster: TUSCHY

SYNOPSIS

Please refer to the outlook issued at Thu 22 Feb 2007 18:30 UTC!

DISCUSSION

Some modifications regarding the TSTM area became necessary.
Latest sounding datas indicate an extensive area of marginal instability release, covering parts of Ireland, UK, France, Spain, Portugal, N-Algeria and N-Tunisia.
Various small disturbances / Areas of better thermodynamic conditions / Support by external effects like the topography will support isolated thunderstorm development over a pretty broad area.

The main reason for the update was the downgrade of the level-1 area, because of a constant influx of very dry air south of Crete. Storms will manage to develop around Crete later-on, but shear will stay weak during this time-frame.

Latest IR images indicate increasing convective activity W / SW of Irland and this trend should continue, as strong forcing will overspread parts of UK and France from the WNW during the evening and night hours.
Quality of airmass, shear and expected minimal instability release will favor an isolated tornado risk mainly over W / SW UK and NW / N France, where dewpoints stay high.
Gauzy instability release, starting radiation and constantly decreasing dewpoints further inland will limit the thunderstorm coverage and hence no higher probabilities will become necessary.