Storm Forecast
Valid: Mon 21 Jun 2010 06:00 to Tue 22 Jun 2010 06:00 UTC
Issued: Sun 20 Jun 2010 22:32
Forecaster: TUSCHY

A level 2 was issued for N-Adriatic Sea, parts of Croatia, Bosnia and Herzegovina, Serbia and W-Romania mainly for excessive rainfall.

A level 1 surrounds the level 2 mainly for large hail, severe wind gusts and tornadoes.

SYNOPSIS

Strong upper low crosses the central Mediterranean from west to east. Quasi-stationary upper trough remains over central Europe with broad WAA downstream, resulting in an extensive warm sector. CAA affects western Europe with more stable air, so no DMC is forecast .

DISCUSSION

... From Greece/Turkey to Estonia and the Adriatic Sea to Romania ...

Potent low dripped off over the central Mediterranean and is about to move due east during the forecast period. The rest of the upper trough remains quasi-stationary over north/central Europe with strengthening ridging in-between over east Europe, building westwards. This set-up creates a broad, moist warm sector over E-Europe with weak kinematics present, as weak gradient/diffluent upper streamline pattern prevails.

At the surface, pressure fall is underway over Bulgaria and Romania with model discrepancies still present regarding final placement of this depression. Placed beneath the exit of a strong phased polar/subtropical jet ought to assist in gradual strengthening of this cyclonic vortex. North of this depression, a quasi-stationary north-south aligned front remains the focus for widespread initiation.

Widespread thunderstorm development occurs already during the morning hours and keeps going well into the night. Moist BL, weak kinematics, good upper support, local orographic enhancement and frontogenesis all support rapid upscale growth into numerous more or less organized thunderstorm clusters with the most vigorous activity expected from the Adriatic Sea to Romania. Excessive rainfall is forecast especially over the N-Adriatic Sea (morning hours) and between the S-Carpathians and the southern Dinaric Alps (noon onwards). It has to be emphasized that various model outputs had spots with 100 l/12h and 150 - 250 l/24h somewhere east of the Adriatic Sea (still model discrepancies left), so flooding could become a problem, if this scenario verifies.

Further north, from W-Ukraine to Estonia, MCS development is also forecast, which move towards the north. Due to somewhat better DLS, MCSs tend to move more rapidly to the north with isolated severe wind gusts and large hail being the main risk.

Also, abundant LL CAPE is present along the quasi-stationary boundary, but also over the Adriatic Sea, so tornado probabilities are augmented, especially during the more discrete phase after initiation, along numerous outflow boundaries (locally increasing LL directional shear), but also beneath rapidly developing updrafts. The level 1 will cover this risk.

After sunset, decreasing CAPE will assist in overall weakening.