Storm Forecast
Valid: Sun 01 Feb 2015 06:00 to Mon 02 Feb 2015 06:00 UTC
Issued: Sun 01 Feb 2015 02:54
Forecaster: TASZAREK

A level 2 was issued for Albania, Macedonia, Bulgaria and parts of Greece mainly for severe wind gusts, tornadoes and in lesser extent for isolated large hail

A level 1 was issued for parts of Balkan Peninsula, Aegean Sea, Black Sea and parts of Turkey mainly for widespread severe wind gusts.


SYNOPSIS

A large vortex is centered over Baltic Sea and with numerous smaller-scale vortices rotating around it provide dynamic weather pattern for most of Europe. Together with Azores High this feature drives cool and dry polar air masses to W Europe and even up to Africa. In the cold sector at the rear of the mentioned trough, steep lapse rates over Bay of Biscay and North Sea may locally provide instability and risk for lightning occurrence. More intense lightning activity is expected over most of the Mediterranean where boundary-layer dew points will be higher and will result in higher thermodynamic instability. Jet stream that encircles cool polar air mass will be stretching highest wind speed values zone from Tunisia to Black Sea. The peak of the long-wave centered over Balkan Peninsula that move eastward is expected to bring severe convective weather phenomena in slightly unstable air mass in front of the active cold front.

DISCUSSION

...parts of Balkan Peninsula, Black Sea, Turkey and Aeagan Sea...

Eastwardly moving trough centered over Albania and associated undulating atmospheric fronts with low and mid-level jet streak above (30 m/s at 850 hPa) create risk for damaging convective phenomena. Although CAPE in the warm unstable sector is likely to be marginal (200-400 J/kg) the existence of impressive 50 m/s DLS and moderate vertical directional shear (0-3km SRH 200 m2/s2) can organize convection linearly. Isolated and embedded mesocyclones capable of producing damaging wind gusts, tornadoes and large hail are not ruled out. Tornado potential will result from overlap of 0-1km SRH over 100 m2/s2 and LLS exceeding 15 m/s in the zone of CAPE up to 200 J/kg located mostly in the lower part of the troposphere. Due to low boundary-layer moisture content, the potential for large hail will be small, but given influx of higher mixing ratios from Aegean Sea to E Bulgaria and the presence of mesocyclone feature, locally hail up to 3-4cm is not ruled out. Non-convective wind gusts in the forward flank of the trough are forecast to be capable of 33 m/s. If convection will be involved, gusts can reach even higher values. The highest threat for damaging wind gusts in the forecast period will extend from Aegean Sea to Black Sea.

Limiting factors for whole level 1 are associated with not very good overlap of moderate QG-forcing and marginal instability that may be not enough strong to provide DMC. Lightning activity presumably will be not very intense, but due to the risk for the occurrence of significant severe weather phenomena (most likely over W Greece. Albania and Bulgaria) level 2 was issued.

The highest threat for severe weather in level 2 is expected in the morning and noon hours when the most favorable forcing (left side of jet streak's exit, advection of vorticity) is forecast. Especially dangerous convective cells capable of producing tornadoes and large hail may move north-eastwardly through parts of NW Greece and Bulgaria around 09-12Z. SW flow perpendicular to the mountain ranges will provide orographic lifting that locally may also help to initiate convection. In the afternoon and evening hours thunderstorm activity should increase over Aegean Sea and W Turkey. Thunderstorms over W coast of Greece and Albania should continue for the whole day, thus some local excessive convective precipitation phenomena is not rulled out.