Storm Forecast

Storm Forecast
Valid: Sat 15 Apr 2017 06:00 to Sun 16 Apr 2017 06:00 UTC
Issued: Fri 14 Apr 2017 23:05
Forecaster: TASZAREK

A level 1 was issued for NE Spain mainly for the large hail, severe wind gusts and excessive precipitation.

A level 1 was issued for N Italy, and parts of Slovenia and Croatia mainly for the risk of large hail and excessive precipitation.


Azores High overspreads over British Isles, France and Bay of Biscay. Blurred 1005-1010 hPa pressure field with low horizontal gradient overspreads S, SE and E Europe. Mid-level jet stream stretches from British Isles, through Benelux, Germany, Poland and Ukraine. An enhanced mid-level flow is also available over NE Spain. Scandinavia remains under cold arctic airmass. A wave passes through Benelux, N Germany and NW Poland during forecast period.

...CNTRL Europe...

Low-topped convection with a marginal potential for lightning is possible at the cold front and in the cold sector behind it over Denmark, E Germany, W Poland and Czech Republic. Although low-level flow is enhanced, these storms have a low severe weather potential (isolated wind gusts up to 20-25 m/s and graupel), mainly due to marginal instability. Given inconsistent NWP model scenarios regarding CI and parcel layer depth this area may have a lightning probability below 15%.

...N Italy, W Balkan Peninsula...

Convection with a higher lightning potential is possible over CNTRL Mediterranean area including Italy and W edge of Balkan Peninsula. Enhanced lapse rates up to 7 K/km overlap with 6-7 g/kg mixing ratios and result in a CAPE up to 400-600 J/kg. These storms initiate thanks to western PVA, orographic lift and local convergence zones, but due to weak vertical wind shear, have a low severe weather potential. Weak storm motion may however results in a few local excessive precipitation events, especially in the mountain areas. Low 0C isotherm elevation, enhanced lapse rates and 15 m/s of shear that may be locally available for the convective cells may result in an event with a hail up to 2-3cm. The overall severe weather threat in this area seems to be rather low and bordering level 0 and 1.

...NE Spain...

Similar situation takes place in NE Spain where within a passage of a shortwave trough, a pockets of enhanced low-level moisture and 7.5 K/km lapse rates produces CAPE up to 300-600 J/kg. Within the overlap of 20-25 m/s DLS and 10 m/s MLS, cells forming in this environment may evolve into low-topped supercells capable of producing large hail up to 2-3cm and marginally severe wind gusts. Some of the NWP model scenarios simulate also a possible excessive precipitation event in extreme SE Spain. However, similar as with CNTRL European storms, NWP model scenarios are inconsistent regarding CI and parcel layer depth.

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