Valid: Wed 25 Nov 2015 06:00 to Thu 26 Nov 2015 06:00 UTC
Issued: Tue 24 Nov 2015 21:07
A level 1 was issued for the Ionian Sea, W Greece, S Albania mainly for excessive precipitation, large hail and to the lesser degree for severe wind gusts.
A level 1 was issues for W Turkey mainly for excessive precipitation and to the lesser degree for large hail.
Blocking high over the Atlantic continues to spill arctic airmass over much of W and Central Europe, reaching even as far as N Africa behind the advancing cold fronts. This also means that much of continental Europe will be under too dry airmass to sustain any electrified DMC. Abundant convective activity is forecast over the Mediterranean where higher dewpoints are still present and passage of short-wave troughs induces cyclogenesis. The first trough of the forecast period will eject from N Africa and rapidly progress towards Greece and W Turkey. The second one will move from W Europe towards the Tyrrhenian Sea and will affect the Mediterranean region especially during the Wednesday night. Both of these troughs will be accompanied by DMC and will be discussed in more detail below.
... Ionian Sea, W Greece, S Albania, W Turkey ...
The aforementioned short-wave will pass this region with a strong SW-ly flow at mid to upper troposphere at its forward flank. A plume of steep lapse rates will be advected towards W Greece in the Wednesday morning hours. With dewpoints around 15 deg C, MLCAPE values on the order of few hundreds to around 1000 J/kg are forecast over the Ionian Sea. A favourable overlap with strong DLS (above 20 m/s) is forecast around 9 - 12 UTC, ceasing later as strong flow moves quickly eastward. Scattered to widespread DMC will form especially ahead of the trough, possibly including a few supercells. These will be capable of large hail and severe wind gusts (as 850hPa flow approaches 20 m/s). Excessive precipitation will be the primary threat as numerous rounds of thunderstorms are possible. Due to the weakening lapse rates, W Turkey will be under lower CAPE values, reducing the overall threat of severe weather (especially of large hail) compared to the Ionian Sea / Greece.
... Central Mediterranean, Sardegna, Corsica, N Africa coastline ...
As the second short-wave arrives during the Wednesday night, cyclogenesis is forecast over in the exit region of the cyclonically curved jet-streak over the Tyrrhenian Sea. However, prevailing N-NW-ly flow over much of the region will not help in replenishing the low-level moisture from south. This reduces the chances of higher CAPE values despite the presence of steep lapse rates thanks to the cold mid-tropospheric airmass. Nevertheless, scattered to widespread DMC will form. Most of the thunderstorms will form in rather weak to moderate shear regime, perhaps apart the western part of the area, where DLS will well exceed 20 m/s. However, convection will be low topped and will probably tap more from 0-3 km shear which will be mostly around 10 m/s. A few organised cells, possibly with brief mesocyclones, are forecast, but the only threat seems to be marginally large hail as CAPE values remain low and low-level moisture rather modest. Overal threat seems to be too low to warrant a Lvl 1 at the moment.