Storm Forecast
Valid: Sun 12 Dec 2010 06:00 to Mon 13 Dec 2010 06:00 UTC
Issued: Sat 11 Dec 2010 15:40
Forecaster: SCHLENCZEK

No threat levels have been issued.

SYNOPSIS / DISCUSSION

A large upper trough is present over the eastern and northern parts of Europe while high pressure prevails over western Europe. According to GFS ensemble forecasts and ECMWF EPS, the Atlantic blocking should persist at least until next Saturday (Dec 18), likely for one or two more weeks and therefore not much change in convective activity is expected in Europe. On Sunday, there are two regions of interest:

Low-end instability is forecast near the center and also ahead of an upper shortwave trough which should enter the Adriatic on Sunday morning. It is questionable whether storms will be electrified or not but in such a situation with some QG forcing, warm water and low CAPE, thunderstorms were observed quite often in this region. Some uncertainties still exist as strong LL winds from the Dinaric mountains may create bad conditions for convective storms. Due to strong upper level winds (50 m/s at 300hPa) and therefore some 25 - 40 m/s deep layer shear, isolated severe weather cannot be ruled out. Some uncapped 100 - 200 J/kg low level CAPE and low level lapse rates in excess of 10 K/km may allow one or two waterspouts but a threat level is not justified. Further east, outside of the forecast area, S Turkey and Cyprus may get strong convective rainfall during the next 48 hours which may lead to flooding.

Isolated briefly organized thunderstorms can be expected over the Atlantic region west of Iberia near the upper cold core of a trough which crosses the Azores with its southern tip. Severe weather seems to be unlikely as shear and low level lapse rates are not favorable for organized storms and tornadogenesis.