CONVECTIVE FORECAST
VALID 06Z MON 22/03 - 06Z TUE 23/03 2004
ISSUED: 22/03 05:35Z
FORECASTER: GROENEMEIJER

There is a slight risk of severe thunderstorms forecast across southwestern France

There is a slight risk of severe thunderstorms forecast across northern Germany and northwestern Poland

SYNOPSIS

Monday at 06Z... A longwave trough is located near a line from Scandinavia to southwestern Europe. Most of western Europe is in a neutral polar air mass that will destabilise as a result of solar heating. A northwesterly mid/upper level jet streak is located from Ireland towards northern Spain and is moving southeastward. During the second half of the forecast period a shortwave trough will develop in the jet's exit region over the western Mediterranean.

DISCUSSION

...southwestern France...
Synoptic-scale ascent, solar heating and strong wind shear set the stage for strong convection over southwestern France. The convection will likely be organised in line segments and mini-supercells. Especially the latter type will be capable of producing strong and severe wind gusts and 2-3 cm hail. Anticipated rather low LCL's indicate one or two tornadoes are possible. The threat of severe storms will diminish around sunset.

...northern Germany, northwestern Poland...
northern Germany, northwestern Poland A mid-level vorticity maximum located over the northern Netherlands is expected to move eastward into northern Germany and northern Poland. On its southern and eastern flanks 15-20 m/s wind shear in the lowest 3 km was observed. This area of somewhat stronger shear is expected to move eastward with the system. As thunderstorms redevelop due to solar heating over western continental Europe, storms could become rather well-organised in this area of stronger shear. Likely modes of organisation over include linear segments possibly with embedded rotating updrafts. Wind gusts and 2-3 cm hail could occur with these storms. Cloud bases are expected to remain quite low so that a tornado is not ruled out. Given the fact that shear is expected to be rather marginal, while the instability will likely remain quite low as well, a slight risk is not issued for this area at this time. During the afternoon, threat will diminish from the west as shear decreases.

#