Storm Forecast
Valid: Tue 22 Dec 2009 06:00 to Wed 23 Dec 2009 06:00 UTC
Issued: Tue 22 Dec 2009 06:46
Forecaster: VAN DER VELDE
A level 1 was issued for Corsica, NW Italy and Slovenia/Croatia for a combined chance of convective gusts, excessive precipitation and tornadoes.
A level 1 was issued for southern Spain mainly for a chance of convective wind gusts and tornadoes.
SYNOPSIS
A large depression with its main center over the western North Sea <976 hPa is filled with a cold unstable airmass. Its warm sector moves over France, Benelux, Germany and Denmark with the potential of causing freezing rain.
Another low and upper shortwave trough moves over Spain into the northern Mediterranean.
DISCUSSION
...southern Spain...
After cold front passage, instability is predicted to increase. Wind profiles should be favorable for fast-moving convective cells and line segments with a chance of severe gusts. Since 0-1 km shear is augmented to values over 15 m/s and the lift associated to the shortwave is strong and concentrated in a small area, a tornado should not be ruled out.
...Corsica and Slovenia areas...
The shortwave arrives during the night and CAPE signals are present in GFS. Strong moisture flux onto shores/elevated terrain can enhance any convective (and non-convective) precipitation and cause local flash floods, but the fast motion of the system reduces the chance. Low level shear >15 m/s and SREH > 200 mē/sē (>300 mē/sē at Balkan coast) are in support of a chance of tornadoes, and overall the fast flow (>50 kts between 900-600 hPa) can create severe wind gusts in convective downdrafts.
