Storm Forecast
Valid: Mon 01 May 2017 06:00 to Tue 02 May 2017 06:00 UTC
Issued: Mon 01 May 2017 00:41
Forecaster: VAN DER VELDE

A level 1 was issued for NE Belarus and W Russia mainly for chance of an isolated tornado.
A level 1 was issued for S England mainly for chance of an isolated tornado.

SYNOPSIS

The map is dominated by an upper low affecting the region between Ireland and Austria, with convection possible under the center of this system, where lapse rates are steep, and near the surface low over SW England. At night, the UK low starts moving into W France. The frontal system lies almost stationary over Germany and the Netherlands. A jet stream circles the upper low center with high lapse rates over central France such that convection would not profit from strong deep layer wind shear. A shortwave trough and jet streak belonging to this system passes over N Italy (very slight instability) and the Alps. Weakly capped convection will develop over Turkey in absence of dynamics and shear. And finally, a small but dynamic low over Belarus produces a very sharply defined frontal system with some unstable air in the warm sector near the occlusion point.

DISCUSSION

...NE Belarus/W Russia...

The thermal gradients around the occlusion are generating warm air advection which results in curved hodographs, yielding over 350 m2/s2 of SREH in the lowest 3 kilometers (GFS model). With just very slight MUCAPE (and MLCAPE) the question is whether deep convection will develop, and if it does, it has a potential of producing an isolated tornado given the favorable helicity.

...S England...

Very high near-surface vorticity and slow convective cell motion and low shear support spin-up type tornadoes (spouts).