Storm Forecast
Valid: Tue 10 May 2016 06:00 to Wed 11 May 2016 06:00 UTC
Issued: Mon 09 May 2016 21:14
Forecaster: DAFIS
A level 1 was issued for Portugal, parts of Spain and Morocco mainly for large hail.
A level 1 was issued for France mainly for large hail and excessive rain.
SYNOPSIS
A wide ridge is found over the southern parts of Europe, while a cold pool over the eastern parts splits in two parts during this outlook with one of them staying at the borders of Czech Republic, Poland and Slovakia and the second part is forecast to move east, towards the Black Sea. Both of them result in steep lapse rates and some hundreds of CAPE where some pulsate thunderstorms are expected. Another short wave trough is formed in NE Scandinavia and a cold front on the surface is found in NW Russia. The main steering mechanism of weather conditions tomorrow in West Europe will be a large cold core cyclone off the shores of Portugal which pushes moist air masses over Spain and France.
DISCUSSION
.... Portugal, Spain, Morocco ....
The cold pool that has formed west from Portugal creates a favorable environment for DMC events in the Iberian Peninsula and NW part of Morocco. Latest model guidance suggest a combination of strong mid level winds and several impulses within the unstable low level air masses, with a vorticity lobe crossing the countries after 12z. DLS is calculated around 20 m/s or more, overlapping with 1000 J/kg of MLCAPE. DLS values over Morocco exceed the 30 m/s, but CAPE values are meager. Any cluster of storm that will appear in this environment, will be capable of producing large hail, even though GFS produces low LCL heights, ECMWF forecasts lower mixing ratios in the PBL and higher LCLs. Moreover, strong to severe wind gusts cannot be excluded at the storms' outflows.
.... France ....
Most of the France will be covered by stratiform clouds, at least the first half of Tuesday, so CI will be postponed in central and NE parts of the country. On the contrary, Normandy and southern parts will experience convective activity earlier, with the peak of the activity in the late afternoon hours, where one or two MCSs are expected and even a supercell in SW parts. GFS produces CAPE up to 2000 J/kg, overlapping with strong DLS of 20 -25 m/s in the level 1 area. At the northern parts of level 1 there is a threat of excessive rainfall since the storm cells are expected to move slowly in the absence of strong mid level winds and high PW values. Large hail is expected at the southern parts of level 1. High resolution models produce some LLS with values up to 10 m/s near the borders of France and Switzerland where LCL is calculated below 800m, so we cannot exclude a weak tornado event.
Thunderstorm activity in East Europe should be very active in the afternoon but severe weather should be rather unlikely, expect from one or two isolated events that do not support issuing a level 1 threat.
