15-07-2007 15:29 | Estofex | m.b.t. 15-07-2007 t/m 16-07-2007
Forecast Update
Valid: Sun 15 Jul 2007 15:00 to Mon 16 Jul 2007 06:00 UTC
Issued: Sun 15 Jul 2007 15:29
Forecaster: GROENEMEIJER
SYNOPSIS
Refer to convective forecast...
DISCUSSION
UK... France... Benelux... N Germany...
A warm front is moving slowly northward over the SE UK, the Benelux and Northern Germany. Its location at 14 UTC was approximately along a line from Southampton to London to Rotterdam to Hannover.
A very moist air-mass with dew points around 20 C has formed to the north of the front, where easterly surface winds are observed, creating a strongly helical environment. Instability of about 1500 J/kg MLCAPE should be available over Nrn Germany and the Benelux north of the front, and around 500 J/kg over the SE UK.
At least one cell that has formed over the SErn UK near London appeared rather organized for a while. Given rather LCL-heights and strong low-level shear more persistent storms that form there may produce tornadoes.
A risk exists that storms develop further east along the frontal zone. If they do, they may become supercells with a threat of tornadoes and large hail. This threat is conditional, but if storms form, they may produce large hail, severe downbursts and even tornadoes.
More storms, that possibly cluster into an MCS are expected to form tonight over NW France. These storms may initially be supercells, but will have a lower threat of tornadoes given more unidirectional low level shear. When an MCS forms, it will likely produce damaging winds in places as it moves NNE ward, possibily affecting the western Benelux and/or the SE UK overnight.
S Germany....
Convective initiation will be possible over SWrn Germany. Given high cloud bases, strong evaporative cooling is expected and a significant risk of a number of downbursts is forecast.
Hagel(-schade) | Onweer/blikseminslag | Tornado/hoosverschijnsel(en) | Verwachtingen/waarschuwingen | Wind/storm (-schade)
