Storm Forecast
Valid: Sat 27 Jun 2015 06:00 to Sun 28 Jun 2015 06:00 UTC
Issued: Sat 27 Jun 2015 00:22
Forecaster: DAFIS
A level 2 was issued for SE Germany and W Austria for large hail, excessive rain and severe wind gusts.
A level 1 surrounds level 2, mainly for marginal large hail and excessive rain.
A level 1 was issued for NE Ukraine and W Russia for excessive rain and large hail.
A level 1 was issued for S Greece for excessive rain and marginal large hail.
SYNOPSIS
A wide ridge prevails in SW Europe while two cyclonic vortices are placed in S Balkans and SE Scandinavia. The rotation center of a big cyclonic vortex remains just south of Iceland but the most interesting part of today's synoptic pattern is the cold front approaching Germany during the morning where some organized lines of storms are forecast. Ridging over the Iberian Peninsula keeps conditions stable except from E Pyrenees where some weak storms may emerge.
DISCUSSION
....Germany, Austria, Switzerland, N Italy, Czech Republic....
A pronounced front bisects Germany with cool and modified marine air to its west and warm/moist air to its east. This front moves leisurely to the east and becomes quasi-stationary during the overnight hours over W Poland. Most likely daytime initiation (around noon) is forecast over the N-Alps to SE-Bavaria. During the afternoon hours, storms also emerge along the convergence zone along the German/Austrian border to the Czech Republic. CAPE/shear overlap ( 1500-2000 J/kg MLCAPE and 15-20 m/s DLS) favors well organized multicells/supercells with large hail. An isolated very large hail event is possible. Strong to isolated severe wind gusts accompany strongest storms, especially from NE Bavaria to the Czech Republic, where 0-3 km shear exceeds 15 m/s. PWs in excess of 30 mm enhance the risk of excessive rainfall and LL convergence zones in W Austria overlapping with high CAPE values, suggest critical areas for large hail.
In North Italy some multicells producing large hail and excessive rain are forecast during the evening hours where high MLCAPE values (>1000J/kg) overlap with strong DLS (20 - 25m/s), enhanced by LL moisture coming from the Gulf of Genoa and steep lapse rates by the diurnal heating. Enhanced LL CAPE and some offshore convection might cause a few waterspout reports mainly over the N-Adriatic Sea. Morning convection in the northern part of the 50-% lightning area (between Venice and Trieste and south to Pula) may see the best environment for waterspout activity
....Ukraine and Russia....
Models agree well in abundant MLCAPE build-up along and east of the westward surging warm front. The MLCAPE exceeds 2500J/kg, even reaching 3000J/kg in Russia, less in NW parts.
It is likely that convection from the night before continues during the first hours of this forecast before clusters start a temporal decreasing trend in coverage and intensity. Between 12-15Z we expect new DMC with exceedance of the convective temperature. The level 1 area stretches to NW Russia, where the right entrance of a modest mid/upper-tropospheric jet induces a supportive background environment for CI. DLS in the range of 20-25 m/s (GFS shows even 35m/s) will be more than adequate for supercells with large hail. In NE Ukraine the main threat will be excessive rainfall due to very high effective PW of 40-45mm and MLCAPE exceeding 1200J/kg in contrast to modest DLS and low LCLs, so large hail risk is limited.
....Greece....
A jet streak is placed over South Greece where CAPE increases from NW to SE and 0-6 km shear of 15-20 m/s (Peloponnesus) and supports well organized multicells/isolated supercells with a large hail and excessive rain event at the areas which are juxtaposed with a LL vortex in south Ionian Sea, as forecast by high resolution models (BOLAM, WRF, MM5). Initiation of storms will be early, probably before noon, because of enhanced CI by orographic lifting. Daytime driven convection beneath the upper trough results in scattered thunderstorms in the rest parts of Greece, between noon and 18Z. 10 m/s DLS and modest CAPE produce pulsating thunderstorms that come offshore during the night hours. Some signals of SRH 0-1km around 50-100mē/sē during Sunday morning in the north part of Crete island suggest a threat of waterspout occurrence.
