Storm Forecast
Valid: Mon 07 Jun 2010 06:00 to Tue 08 Jun 2010 06:00 UTC
Issued: Mon 07 Jun 2010 05:29
Forecaster: SCHLENCZEK
A level 1 was issued for NE Algeria / N Tunisia mainly for large hail and severe wind gusts.
A level 1 was issued for N Poland and SW Baltics mainly for severe wind gusts and large hail and to a lesser extent for tornadoes.
SYNOPSIS
A low pressure system over NE Germany is forecast to move eastward towards the Baltic States. Ahead of this low, a moderately warm and moist airmass overspreads most parts of Austria, Czech Rep. and W Poland. Another low pressure system will affect the British Isles in the afternoon / evening hours. Remnants of an upper low over the Black Sea will lead to unsettled conditions over the Black Sea region and Turkey.
DISCUSSION
...NE France, S Benelux, extreme W Germany...
In the late evening / night hours until Tuesday morning, some low-end instability will be available ahead of an upper trough. Mid level wind fields will strengthen to 20 - 25 m/s at 700 hPa and a narrow convective line with isolated severe wind gusts may develop. As convective initiation in this environment is questionable due to relatively weak forcing, no threat level was issued.
...N Tunisia, NE Algeria...
A westerly upper jet streak with 30 m/s at 500 hPa will cross this region from west to east during the afternoon. Diurnal heating will lead to some hundred J/kg CAPE and some QG forcing should lead to convective initiation during the afternoon. Only a small number of storms is expected as the airmass is strongly capped. 20 - 25 m/s deep layer shear and locally > 250 mē/sē SRH3 may allow some well-organised multicells and a few supercells with large hail and isolated severe wind gusts as main threat. Most CAPE will vanish after sunset and convective activity will decrease in the late evening / night hours.
...Italy, N Balkans, Hungary...
In a region with weak pressure gradients and weak vertical shear, diurnal heating will lead to some hundred J/kg CAPE. Most storms should be short-lived and briefly organised. An isolated large hail event cannot be ruled out but a level 1 seems not warranted.
...N Poland, Baltic States, Belarus, W Russia...
Ahead of an upper trough, warm and moist air with a few hundred J/kg CAPE is advected to the northeast. In the vicinity of a 40 m/s upper jet streak, deep layer shear will increase to values between 20 and 25 m/s. Most of the shear is present at lower levels (15 m/s at 850 hPa) and storms will tend to merge into a linear MCS with isolated severe wind gusts and marginally severe hail possible. Especially in the northern parts of Poland, rich BL moisture leads to low LCL heights and locally enhanced LLS may allow an isolated tornado. Peak activity is expected in the afternoon and early evening before stabilisation of the boundary layer will reduce instability.
...Bosporus region...
In an environment with weak vertical shear and some hundred J/kg CAPE, showers and thunderstorms will develop during the day. Especially over the W Black Sea and Bosporus, the QPF maps of GFS suggest locally up to 50mm / 6h. A level 1 for excessive rainfall is not issued as most of the precipitation is expected to occur over water.
...Other regions...
Some diurnally driven showers and thunderstorms in a weakly sheared environment with a very low potential of severe weather are expected to develop over N Iberia / S France and S Scandinavia during the afternoon hours.
