Storm Forecast
Valid: Tue 02 Nov 2010 06:00 to Wed 03 Nov 2010 06:00 UTC
Issued: Tue 02 Nov 2010 01:04
Forecaster: KOROSEC
A level 2 was issued for south-central Italy and Adriatic sea as well as for eastern Adriatic coast mainly for excessive convective rainfall, strong winds, tornadoes and large hail.
A level 1 was issued for surrounding areas of level 2 mainly for excessive convective rainfall.
A level 1 was issued parts of British Isles, north Sea and Denmark mainly for strong to severe wind gusts.
SYNOPSIS
A strong zonal flow has established across northern Europe, where deep surface low is placed west of Scandinavia. The main cold front rapidly moves east while another one stretches across British Isles.
Over southern Europe, a slowly weakening large upper low makes only slow SE progress from across central Italy. Along/ahead of an attendant surface frontal zone, another round of excessive rainfalls and severe storms is expected.
A building upper ridge moves into SW Europe with high pressure system expanding towards central Europe by Wednesday morning.
DISCUSSION
British Isles, North Sea...
Strongly sheared environment with deep-layer shear exceeding 30m/s is embedded within the zonal flow, wraping around the deepening surface low north of UK. The main frontal zone moves east into Scandinavia in early morning hours and should locally support some strong winds where stronger convective cells will occur. Behind this front, cold maritime airmass will spread into North sea and UK, showers and a few thunderstorms could occur. While southern UK will be affected with belt of WAA coming from SW ahead of a new front, environment will become supportive for convection and/or convective lines once the frontal zone moves through. Though models are showing only weak instability signals, very high shear is well favorable for some strong cells/lines across the level 1 area. Expect strong to severe wind gusts locally along these line(s). However, very high speed shear and quite high SREH, but limited instability, could as well support stronger cells with embedded rotating updrafts.
... central Mediterranean and Adriatic sea ...
A large upper-level cut-off low with a history of intense and extensive rainfalls over north-central Italy, which caused major flooding in Po valley, will finally weaken and slowly move towards SE. An attendant cold front will be progressing east across the southern Italy and severe storms will continue along it towards southern Adriatic sea. Strong WAA with impressive mixing ratio values will be pushing moisture northwards which should result in intense and continues orographic plus convective rainfalls across the level 2 area. Overlaping the several hundreds of MLCAPE, around 20-25 m/s of deep-layer shear, as well as around 15 m/s of LL shear and 150-200 m^2/s^2 SREH3 will be available for organized severe storms, capable of producing large hail, strong winds and a couple of tornadoes besides the intense rainfalls as well. Supercells with LL mesocyclones are especially possible along the coasts of south Italy and coastal areas of southern Adriatic sea. A level 1 was extended further north due to excessive rainfall threat again as it seems that strong southerly mid-level flow with be pushing enough moisture into northern Adriatic area as well. Over warm waters of southern Mediterranean and with cold air aloft, scattered showers and thunderstorms will be occuring in the wake of the cold front.
