Storm Forecast
Valid: Tue 09 May 2017 06:00 to Wed 10 May 2017 06:00 UTC
Issued: Mon 08 May 2017 21:04
Forecaster: DAFIS
A level 1 was issued for Bulgaria, NE Greece and NW Turkey mainly for excessive precipitation, large hail, severe wnd gusts and tornadoes.
A level 1 was issued for N Portugal and N Spain mainly for large hail and severe wind gusts.
SYNOPSIS
An upper-air trough extends from Scandinavia towards Central Mediterranean Sea with the jet stream being cyclonically curved at its leading edge. A cold outbreak at the Baltic States and W Russia brings unseasonal snow showers. A vorticity max is forecast over SE Balkans and will also cross N Turkey during Tuesday. Another place of convective interest if found in North Iberian Peninsula, where another trough is approaching from the Atlantic Ocean. Steep lapse rates and unstable low level air masses will create a favorable environment for many storms, but in addition, strong vertical wind shear over Turkey may increase the intensity of storms to a great extent. Finally, some storms over Italy may produce locally excessive precipitation.
DISCUSSION
.... Bulgaria, Greece and Turkey ....
As an embedded short-wave trough is approaching SE Balkans, a cold front near the surface is also travelling south. The preexisting warm and moist LL air masses will be pushed SE, towards Turkey. Moreover, a jet streak is crossing the country, increasing the DLS up to 35 m/s. Several storms are expected to pop-up after 12z in N Greece, Bulgaria and NW Turkey, some of them will become organized multicells. Supercells may also form over Turkey as large fat CAPE profiles and high SHRE0-3 will feed the storms during the afternoon. CI will be a problem in Central Turkey as a cap is expected to form and LL wind speeds will exceed 10-15 m/s. To sum-up, in Bulgaria the main threat will be excessive precipitation from isolated cells as well as multicells in the eastern parts, in NE Greece hail up to 2cm is expected and supercells in Turkey can produce hail up to 3cm, severe wind gusts and tornadoes.
.... N Portugal and NW Spain ....
Even though NWP models predicted thunderstorms today in this area, CI never happened, probably because of the strong cap. Tomorrow CAA in the mid-levels will result in steep lapse rates and CI is expected after 12z. Scattered signals of DLS in the range 10-15 m/s are not indicators of strongly organized convection, but 10 m/s 0-3km shear overlapping with 500 1000 J/kg CAPE and >7K 800-600 hPa LR can produce strong updraughts, resulting in large hail and severe wind gusts. Activity will gradually stop after the sunset.
