Storm Forecast
Valid: Fri 20 Nov 2009 06:00 to Sat 21 Nov 2009 06:00 UTC
Issued: Thu 19 Nov 2009 17:33
Forecaster: TUSCHY
A level 1 was issued for the far eastern Atlantic mainly for severe wind gusts.
SYNOPSIS
Deep trough over the NE-Atlantic shifts eastward with strong WAA downstream, resulting in unseasonably warm conditions over south/central Europe. A cold and stable airmass prevails over far NE Euorpe with unsettled conditions over Norway and Sweden.
DISCUSSION
... General thunderstorm areas ...
A weak wave, embedded in the SW-erly flow causes regionally enhanced convective precipitation probabilities over parts of Scotland during the noon/afternoon and along the SW coast of Norway during the morning hours. Nothing severe is forecast. Both GFS and ECMWF are in-line with highlighting thunderstorm areas.
... Level 1 area ...
And again, another set-up for a strong warm conveyor belt (WCB) over the far eastern Atlantic. Winds at all levels ramp up during the night hours with peaks of 65m/s at 500hPa, 40m/s at 850hPa and the advection of weakly modified tropical airmass. Compared to the last events, the cold airmass is displaced well to the west, so the overall precipitation event remains more stratiform in nature. However, environmental conditions are again favorable for some conditional symmetric instability release and therefore embedded convection. Confidence in more than sporadic thunderstorms is too low for a thunderstorm area. A non-thunder level 1 was included due to enhanced chances for embedded convective segments and intense winds just above the surface along the eastnortheastward moving cold front. Despite limited mixing and very weak lapse rates in the BL, wind gusts in excess of our severe criterion are forecast. This WCB spreads NE-wards and is about to affect Ireland and UK during the morning hours with another round of rain on already soaked ground.
West of the level-1, winds at 850hPa remain at 20m/s with good downward momentum, but postfrontal subsidence limits convective activity until 06 UTC.
