Forecast Update
Valid: Sun 05 Aug 2012 12:00 to Mon 06 Aug 2012 06:00 UTC
Issued: Sun 05 Aug 2012 12:31
Forecaster: SCHLENCZEK

A level 2 was issued for NE Spain mainly for large hail, severe wind gusts and excessive precipitation.

A level 2 was issued for the W Alpine region mainly for large hail, severe wind gusts and tornadoes.

A level 2 was issued for S Poland and N Slovak Rep./ NE Czech Rep. mainly for large hail, excessive precipitation and severe wind gusts and to a lesser extent for tornadoes.

A level 1 was issued for the surrounding regions of the level 2 areas mainly for large hail, severe wind gusts and excessive precipitation.

A level 1 was issued for NE France, Benelux and W/ NW Germany mainly for severe wind gusts, marginally large hail and tornadoes.

SYNOPSIS

See previous forecast.

DISCUSSION

... LVL2 areas and large LVL1 area...

Only marginal changes are done to the level 2 areas due to slightly different model results and observations. The eastern LVL2 area was shifted slightly to the east as instability is somewhat higher and convection has already been initiated.

Also, the LVL1 has been extended to the northeast as the probability of storms merging into some MCSs has increased during the past runs of GFS. Those storms will likely produce marginally large hail, isolated severe wind gusts and excessive convective rainfall. A tornado is also not ruled out as locally enhances LL shear is simulated by AEMET HIRLAM.

...NE France, Benelux, W Germany...

Recent outputs of GFS and also recent soundings indicate that there will be a good overlap of 20 - 25 m/s deep layer shear and some hundred J/kg CAPE. As the shortwave trough approaches during the afternoon hours, QG forcing should be sufficient for convective initiation. Given some locally augmented SRH3, some storms may become supercellular and may pose a threat of marginally severe hail, severe wind gusts and tornadoes. The threat of severe weather will gradually diminish after sunset as most of the CAPE is confined to the boundary layer.