Storm Forecast
Valid: Fri 06 Jan 2017 06:00 to Sat 07 Jan 2017 06:00 UTC
Issued: Thu 05 Jan 2017 09:45
Forecaster: TUSCHY

A level 1 was issued for excessive rain mainly for SW-Turkey.

A level 1 was issued for waterspouts mainly for parts of the Tyrrhenian, Ionian, Adriatic and Aegean Sea.

SYNOPSIS and DISCUSSION

An highly amplified mid-/upper tropospheric streamline pattern continues with ridging affecting SW- and W-Europe and a pronounced trough covering most of CNTRL-/E-Europe. This configuration results in the advection of a very cold and dry air mass all the way to the CNTRL-/E-Mediterranean. Despite a long fetch over the warm sea, only isolated to scattered activity is expected due to the dryness of the air mass. Ongoing BL modification should support short-lived thunderstorms in the highlighted areas.

However two foci with a severe risk exist:

The first one is evident over SW Turkey along/just ahead of an eastward moving modified arctic cold front. Advection of more humid maritime air beneath an area with upper divergence next to the right entrace region of a powerful 50 m/s mid-tropospheric jet streak result in a forced band of embedded convection along the eastward shifting front. As background flow remains nearly parallel to the orientation of the front, a solid band of heavy precipitation is forecast to gradually shift east within the level 1 - temporal training is forecast. Up to 600 J/kg MLCAPE (during the start of the forecast) assists in embedded/elevated thunderstorm activity, but betimes CAPE and thunderstorm probabilities decrease. Excessive rain along the coast may cause flash flood problems. The risk ends from west to east and exits our area of responsibility until midnight.

The second area includes all offshore regions over the Adriatic, Ionian, Aegean and Tyrrhenian Sea. SSTs still run above climatology (1971-2000) and as 850 hPa temperatures drop to -8 to -15°C from north to south during the forecast, robust LLCAPE of locally more than 300 J/kg is anticipated. Thunderstorms offshore or along the coast experience rather weak shear, so the waterspout risk will be an enhanced. We added level 1 areas for those regions, where thunderstorm development is most likely (despite slow BL modification).

Isolated thunderstorm activity is possible offshore of NW-Norway during the night, but sporadic nature and lightning climatology for this time of year preclude the issuance of any lightning areas.