Forecast Update
Valid: Wed 03 Sep 2008 15:00 to Thu 04 Sep 2008 06:00 UTC
Issued: Wed 03 Sep 2008 16:17
Forecaster: SCHLENCZEK
SYNOPSIS
Please refer to the convective forecast.
DISCUSSION
...SE France...
An organized convective line has formed over central / southwestern France in an environment with about 1000 J/kg MUCAPE and 25 - 30 m/s deep layer shear and it is moving northeastward. In parts of central and southeastern France ahead of the line, SRH in order of 150 J/kg and strong LLS with more than 12 m/s is present and T/Td in order of 25/20 degrees will create an environment supporting a few tornadoes that may be strong as there is a large angle between the low level wind vector and the 0-1 km shear vector. Very strong winds at 850hPa and 700hPa (20 - 25 m/s) will likely pose a threat of widespread severe gusts with a few damaging gusts not ruled out. If some storms develop more discrete, they will likely produce isolated large hail as well. The convective line should move into southwestern Germany and Switzerland in the next few hours.
...E Germany, Poland...
Remnants of the convective line over central Germany will continue into eastern / northeastern Germany and Poland during the late evening / night hours. Deep layer shear in order of 20 m/s and strong low level winds should support some severe gusts. The tornado threat is somewhat limited as the convective system is probably more elevated but an isolated tornado cannot be discounted, though.
...SE Finland / W Russia...
Ahead of an approaching shortwave trough, some low-end instability should be in place over southeastern Finland. In the vicinity of a cold front, deep layer shear in order of 25 m/s and 700hPa wind speeds near 20 m/s should support isolated severe gusts with a narrow convective line. High SRH1 / SRH3 (600 / 400 J/kg) may allow an isolated tornado as well. As most of the CAPE is surface-based and storm development is expected around sunset, a low-end LVL1 threat should be the best choice.
...Other areas...
The thunderstorm area over northern Scandinavia and the North sea has been extended as recent models show a higher probability of electrified storms as it was yesterday evening.
