Storm Forecast
Valid: Tue 19 Apr 2016 06:00 to Wed 20 Apr 2016 06:00 UTC
Issued: Mon 18 Apr 2016 22:17
Forecaster: DAFIS

A level 1 was issued for parts of Croatia, Bosnia and Herzegovina, Serbia and Montenegro, N Bulgaria and Romania mainly for the large hail, excessive rainfall and severe wind gusts. An isolated event of waterspout in Croatia is not excluded.

A level 1 was issued for Portugal mainly for severe wind gusts and excessive rainfall.

SYNOPSIS

A wide ridge is formed, stretching from W Mediterranean basin towards Ireland, while a cyclonic vortex is approaching the coasts of Portugal which is forecast to remain quasi-stationary for the next 48 hours. Over N Europe a slightly positive tilted trough during the morning of Tuesday becomes negative tilted afterwards, pushing cold and dry air masses over Central Europe, where deep convection is precluded, although, steep lapse rates over the Baltic States suggest that some storms may form after 12z. This set-up results in a strengthening baroclinic zone in N Balkans, where better LL moisture becomes established. Another shortwave trough that travels from N Italy over Adriatic Sea provides a favorable environment for DMC near the coasts of Croatia.

DISCUSSION

.... Croatia, Bosnia and Herzegovina, Serbia and Montenegro, parts of Serbia, N Bulgaria and Romania ....

As the shortwave trough over N Italy moves over the Adriatic Sea, cyclogenesis takes place on the surface and a sharp shear gradient is present with enhanced DLS next to the mid/upper jet in W Balkans. Strong PVA should provide enough deep tropospheric lift apart from diurnal heating, especially at the coasts of Croatia. At the other parts of level 1 area, PBL is expected to be more warm and moist than on Monday, so CI should start early enough for storms to become organized, into this strongly sheared environment. MLCAPE of 800-1200 J/kg will be adequate for a few strong updrafts and large hail events, but there is also a threat of excessive rainfall in parts of S Serbia and SW Romania where PW is calculated near 30 mm. Strong to isolated severe wind gusts are possible, too, also fostered by supportive pattern for strong outflows. In Central Serbia cloudiness may suppress adiabatic heating of the surface in the afternoon but elevated convection during the early night hours support the thought of a level 1 for any messy organized storm clusters. LLS does not overlap with CAPE, so tornado threat remains low but one or two waterspouts may form near the coasts of Croatia due to steep lapse rates above the sea and locally strong convergence lines in this complex topography.

.... Portugal ....

A vigorous cyclonic vortex will approach the coasts of Portugal during Tuesday, with its cold front crossing the country in the early morning. The advection of warm and moist air masses from SW increase the threat of an excessive rainfall event, even though non-convective features are expected to prevail. Nevertheless, any storm that will be able to form within this strong wind field, will be able to produce strong to severe wind gusts and downpours, as PW exceeds the 30 mm according to high resolution models.