Storm Forecast
Valid: Fri 08 Jul 2011 06:00 to Sat 09 Jul 2011 06:00 UTC
Issued: Thu 07 Jul 2011 20:44
Forecaster: TUSCHY
A level 1 was issued mainly for parts of UK for marginal hail and a few tornado events.
A level 1 was issued mainly for the Alpine region, E-Czech Republic, parts of Poland and Slovakia mainly for large hail and strong to isolated severe wind gusts.
A level 1 was issued for SE-Austria, Slovenia and W-Hungary mainly for large hail (an isolated significant hail event possible), strong to isolated severe wind gusts and an isolated tornado report.
SYNOPSIS
Neutral tilt of a cyclonic vortex over NW Europe indicates weak net-movement during the forecast. Brisk W/SW-erly flow continues over E/CNTRL Europe as a maritime air mass spreads eastwards. Another trough over E-Europe weakens betimes with weak geopotential heights increase over the Mediterranean.
DISCUSSION
... Alps, N-Italy, Slovenia ...
Numerous eastward moving vorticity maxima affect that area with a gradual weakening trend from west to east. As overall wind field backs somewhat during the forecast, increasing upslope flow component assists in scattered thunderstorm initiation next to either diurnal initiation or forced convection. Despite favorable shear profiles for organized convection (0-6 and 0-3 km bulk shear of 15 - 20 m/s), CAPE will be meager due to modest BL moisture and weak mid-level lapse rates. However we decided to issue a marginal level 1 for isolated large hail and strong wind gusts, if locally better moisture evolves.
Models agree in better MLCAPE over far NE-Italy, Slovenia, W-Hungary and far SE-Austria. An augmented risk of well organized multicells/isolated supercells exists with the primary risk being large hail (isolated very large hail possible) and strong to isolated severe wind gusts. Low LCLs, weak SRH and a somewhat deeper moisture depth may also assist in an isolated tornado event.
... E-Austria, Slovakia, E-Czech Republic and parts or Poland ...
A cold front over E-Germany/W-Czech Republic (08th July 06Z) moves towards the east as a weak upper impulse lifts northeastwards. Ahead of this front, EZ and GFS agree well in a moderately unstable warm sector (800 - 1000 J/kg MLCAPE), which will be weakly sheared at best. Scattered to widespread thunderstorm development ist anticipated but weak shear precludes better organized updrafts. Hence, a marginal level 1 was issued only for those areas, where rich buoyancy may assist in an isolated large hail report. Rapid thunderstorm clustering is forecast, which assists in locally excessive rainfall next to slow thunderstorm motion. This risk extends further north of our level 1 area, but current indications don't support rainfall amounts, matching our level criterion over N/NE Poland.
... UK, Ireland and Scotland ...
Placed beneath a vertically stacked depression, daytime driven thunderstorms are forecast. Weak shear precludes organized convection, but I'd at least expect a few marginal hail events with that activity. Also, GFS indicates a fairly well organized LL depression with enhanced LL shear, especially during the evening hours ( 12 m/s LL shear, up to 200 m^2/s^2 SRH1 and low LCLs). We don't want to rule out a few tornado reports with that activity. Thunderstorms gradually decay after sunset.
... W-Russia ...
Scattered to widespread thunderstorms occur beneath a weakening upper trough. Shear will be weak with modest CAPE, so a mixture of pulsating thunderstorms and multicells is forecast. Marginal hail (an isolated large hail event possible) and strong wind gusts are forecast.
