Storm Forecast
Valid: Sun 03 Feb 2019 06:00 to Mon 04 Feb 2019 06:00 UTC
Issued: Sat 02 Feb 2019 19:22
Forecaster: TUSCHY

A level 1 was issued across the SE Adriatic and far NE Ionian Sea mainly for exessive rain, isolated large hail and an isolated tornado risk.


SYNOPSIS

An highly amplified streamline pattern continues with a Rossby-wave and embedded vortex analyzed over S-/ CNTRL-Europe, both framed by extensive ridges to the west and east. The vertically stacked vortex' core is placed over Corsica/Sardegna and is accompanied by a strong LL depression, which shifts to the SE during the forecast. A deep southerly flow regime covers the eastern fringe of that vortex with persistent moisture and differential temperature advection offering some onshore MUCAPE over SE/E-Europe.

Elsewhere dry and cold/stable conditions persist and preclude organized onshore thunderstorm activity. Spotty offshore convection beneath cold mid-levels may yield enough vertical extent for a confined and short-lived / non-severe thunderstorm event.

A few thunderstorms are possible over NW Europe in confined regions (e.g. dry slot/surface front intersection) as numerous dynamic systems pass by, but model discrepancies remain too high for adding a specific lightning area.

DISCUSSION

... CNTRL Mediterranean ...

Three foci for strong/severe thunderstorms exist.

The first area of interest features ongoing convection along the SE coast of the Adriatic Sea, spreading into the far N Ionian Sea during the forecast. The storm mode will be a back-building MCS. The system gets fed by intense LL winds from the S/SE in excess of 25 m/s. This will be a progressive event as the moisture tongue shifts SE betimes and weakens, so it was highlighted by a broad level 1. Excessive rain will be the main hazard with Montenegro and far W-Albania probably collecting up to 150 l/qm rain in 24h. A few coastal tornadoes due to intense LL shear and a few marginal large hail events due to embedded multicells/isolated supercells are also possible.

The second area of interest will be Sardegna and Corsica, which both reside beneath the base of the vortex in a low shear / CAPE environment. Slow moving thunderstorms bring locally excessive rain and marginal hail.

Finally the third area of interest encompasses the Tyrrhenian and the Adriatic Sea, where scattered thunderstorms bring heavy rain and graupel or even isolated hail. The SW coast of Italy will see a local excessive rainfall risk with repeatedly onshore moving thunderstorms. This setup also favors a few waterspout reports.

Also a few thunderstorms may develop over Slovenia and surrounding areas during peak heating. This activity remains mostly elevated with graupel/isolated hail the main hazard.

We thought about adding a level 1 over NE Algeria with repeatedly onshore moving showers/thunderstorms but an utterly dry air mass from France does not recover enough over the Mediterranean for a coastal excessive rainfall threat. QPF data also keeps 24h amounts below any level threshold.