Storm Forecast

Storm Forecast
Valid: Thu 03 Mar 2016 06:00 to Fri 04 Mar 2016 06:00 UTC
Issued: Thu 03 Mar 2016 05:24
Forecaster: GATZEN

A level 1 was issued for the southern Tyrrhenian Sea region, the eastern Adriatic Sea region, the Ionian Sea and Greece and the south-eastern Aegean Sea region mainly for excessive rain, severe wind gusts, and to a lesser extent large hail.

A level 1 was issued for parts of the north-eastern Atlantic mainly for severe wind gusts.

SYNOPSIS

An intense polar trough / vort-max has entered the European long-wave trough from the north-west. It will split up over the Alps, with one vort-max lifting into Scandinavia, the other digging into the Adriatic, the latter yielding a negatively tilted short-wave trough that will affect the Aegean late in the period. Upstream, another intense vort-max follows and migrates into the Chanel region on Friday morning. At low levels, dry air masses spread into the west Mediterranean behind a cold front that crosses Italy and the Adriatic today, reaching Greece in the evening hours.

DISCUSSION

Italy and Adriatic to Greece and Aegean

Main convective activity is expected to occur with the mid-level vort-max crossing parts of the central Mediterranean today. It yields steep low- to mid-level lapse rates that expand from northern Italy to the south-east today. These can partly overlap with rather moist air mass ahead of a cold front, with surface dew points around 10C, especially from southern Italy towards the Aegean Sea. CAPE in the order of a few 100 J/kg is forecast by latest GFS.

Thunderstorms are currently going on across northern Italy along the cold front. While the cold front leaves the region with strong DCVA over the Adriatic, weakening convective activity is expected in the morning hours. Another increase can be expected later in the day when steep lapse rates overlap with rich moisture across the southern Tyrrhenian Sea and later on over the Ionian Sea and Aegean. Numerous storms are forecast that can organize into linear segments due to deep layer vertical wind shear around 15 m/s.

Main threat with these storms is strong to severe wind gusts given the already strong background flow. Additionally, large hail is not ruled out with the stronger updrafts. At the slow moving eastern flank of the cold front, excessive although partly non-convective precipitation will affect the Adriatic and later on eastern Aegean Sea region. In the wake of the cold front, some more storms are forecast close to the center of the trough, where steep lapse rates are present and some remaining moisture will allow for weak CAPE especially over the Sea.

Western British Isles to north-western France

An intense trough travels southward across western Europe. At its flank, a very strong mid-level jet streak spreads across the north-eastern Atlantic. It will provide strong DCVA and steep lapse rates are forecast by latest GFS at its cyclonically curved flank.

Ahead of the vort-max, a strong low-level cold front spreads southward, and cold air advection is expected. This will limit the chance of deep moist convection due to isentropic descent. Late in the period, the cold front becomes orientated parallel to the flow and cod air advection decreases. A few storms may be possible over southern France as indicated by latest GFS.

Main convective activity is forecast with the vort-max that travels southward west of Europe. Especially late in the period scattered storms are expected that will likely stay offshore. Main threat with these storms is severe wind given the strong background flow.

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