Storm Forecast

Storm Forecast
Valid: Wed 23 Oct 2024 06:00 to Thu 24 Oct 2024 06:00 UTC
Issued: Tue 22 Oct 2024 20:11
Forecaster: TUSCHY

A level 1 was issued over parts of the CNTRL Mediterranean mainly for heavy (locally excessive) rain and an isolated tornado event.

A level 1 was issued for parts of E-Spain mainly for heavy rain and an isolated tornado event.

SYNOPSIS

A weakness in the blocking pattern over S Europe features a decaying trough over the W Mediterranean with a new trough further W (Portugal to Morocco). Embedded in this broad trough structure is a cut-off over S Germany (not much net motion forecast), whereas another and potent trough approaches from the W.
While a stagnant wave train persists over S Europe, a bit more progressivity occurs to the N (NW Europe to Scandinavia into NW Russia).

Along the BL an extensive 1035 hPa high pressure area is placed over CNTRL Europe with a quasi-stationary and meridionally aligned low pressure channel to the south (covering most of the CNTRL Mediterranean). This area will be the main focus for DMC activity.

An eastward moving wave sparks a few thunderstorms over the Gulf of Finland and E but limited CAPE should preclude severe with those thunderstorms (maybe a few gusts).

DISCUSSION

... Italy and surrounding areas ...

Driven by the quasi-stationary wave pattern, an extensive warm conveyor belt (WCB) has established along the E fringe of the weakening upper trough with TPWs soaring into the lower 40 mm in the latest blended products (anomaly values in excess of 150 % to the background climatology).

This WCB features a long fetch of S-erly winds atop the W Tyrrhenian Sea with MUCAPE in general in the 800-1200 J/kg range. DLS is in the 5-10 m/s range with storm motion vectors in the 10-15 m/s range from the S. Some signals for enhanced 0-2 km convergence exist with the WCB, but this signal weakens during the day, whereas parcel layer depth increases over NW Italy during the night.

We probably see an ongoing N-S aligned MCS with slow moving convective elements including temporal training just E of Sardinia and Corsica. This activity moves N towards W-CNTRL Italy before weakening during the evening onwards. Still expect pulsating convection during the night as the airmass remains unstable with diffuse background forcing. Hence the main activity should evolve along the coastal front/convergence zone.

Isolated level 2 rainfall amounts are possible along the W coast of CNTRL Italy, but hard to forecast (that far out) mesoscale dynamics dictate that risk. Hence only a broad level 1 was issued.

Next to the rain threat an isolated tornado is possible mainly along LL convergence zones/along the coast.

Further N (over N Italy), vanishing CAPE but better upper divergence ahead of the S German cut-off support a broad area with convectively enhanced precipitation. This acitcity brings heavy rain, but missing thunderstorms (or only very spotty events) preclude any level for that event. However some final rainfall amounts (mainly along the orography) could be the highest of the day for Italy.

... E Spain ...

Repeatedly onshore moving thunderstorms bring heavy rain to this level 1 area with an isolated tornado event along the coast not ruled out.

Creative Commons License