Storm Forecast
Valid: Thu 13 Mar 2025 08:00 to Fri 14 Mar 2025 06:00 UTC
Issued: Thu 13 Mar 2025 08:48
Forecaster: TUSCHY

A level 2 was issued for the Balearic Islands all the way to far NW Italy mainly for an augmented tornado risk (including a significat event), hail and severe to damaging wind gusts. Heavy rain is also forecast.

A level 1 surrounds the level 2 mainly for similar hazards but lower probabilities. In general the tornado risk diminishes onshore.

A level 1 was issued for N Algeria/Morocco mainly for isolated large hail and severe gusts.

A level 1 was issued for parts of the Balkan States and surroundings mainly for large hail and severe gusts but also for an isolated tornado threat.

SYNOPSIS

A phase locked upper wave pattern features a positive tilted trough over W/SW Europe with an extensive warm conveyor belt along its eastern fringe. This WCB features positive EFI water vapour flux/CAPE shear values and assists in a broad overlap of meager to modest moisture with strong shear.

DISCUSSION

...Balearic Islands to far NW Italy...

A shallow and progressive wave lifts out of the long wave trough's base and moves from the W-Mediterranean towards Italy. BL response occurs as MSLP lowers, which results in the northward advection of a seasonable moist marine layer towards the Balearic Islands. Dewpoints increase into the lower to mid tens and result in 400-800 J/kg MUCAPE as this moisture surges beneath the upper thermal trough. First the warm sector remains confined but broadens NE of the Balearic Islands, as the wave deepens a bit. This also increases transition time for maturing cells, which cross the warm sector. This increases confidence in long tracking supercells to the NE of the Islands.

However the setup near/over the Balearic Islands also features a very effective background for well organized supercells in a modest CAPE but very strong shear environment. In fact, some models indicate 0-3 km shear in the 20-25 m/s range, which is rather strong.

A northward advecting marine airmass slides on a cooler/stable airmass just N of the Islands and causes a band of heavy rain. The main focus for organized DMC exists along the S fringe of this precipitation, where more discrete cells travel both along the vorticity-rich marine front and into the strongly sheared warm sector.
Elongated forecast hodographs show very effective LL inflow with lots of effective streamwise and streamwise vorticity-rich moist/unstable air to enter organized updrafts, which take profit of 20 m/s DLS. Hence the risk of a few tornadoes/mesocyclonic waterspouts is enhanced and even a significant event is possible. The main uncertainty remains, if the sweet-spot for tornadic supercells remains just to the south of the Islands or pushes enough to the north. Severe to damaging gusts are also forecast next to isolated hail.

In addition, organized thunderstorms pose a hail and severe gust threat over SE Spain around noon into the afternoon before thunderstorms exit towards the Mediterranean Sea. Also, heavy rain becomes an issue betimes (and also into the overnight hours) over S-CNTRL Spain with slow moving convection. Hence the rather broad level 1 for S to CNTRL Spain.

Betimes, long tracking supercells race NE over parts of the W Mediterranean Basin. This activity is accompanied by all kind of hazards including a tornado/severe gust and isolated hail threat.
During the evening and overnight hours, the passing wave takes the severe risk towards Corse/NW Sardegna and into far NW Italy. Rotating storms with neutral LL lapse rates offshore/along the coasts bring all kind of hazards including a tornado, severe wind gust and isolated hail threat. Offshore moving storms turn more elevated betimes due to a stable BL air mass, but we kept a level 2 mainly for the severe gust risk for more elevated areas.

The level 1 over N Italy was issued for a few better organized afternoon storms, before overall storm mode turns too messy for anything more discrete. Hail and a few severe gusts should be the main hazard with that activity.

... N Algeria ...

Onshore advecting marine air mass assists in 300-600 J/kg MUCAPE beneath steeper mid-level lase rates. Strong DLS favors organized convection, although limited vertical CAPE extent could offset some of the highest DLS values. Nevertheless a few severe thunderstorms with severe wind gusts (rather high LCLs) and isolated large hail are forecast to shift E.

... Parts of E/SE Europe (e.g. the Balkan States) ...

Behind a departing upper wave a more zonal flow regime becomes established atop a still moist BL air mass. Diabatic/diurnal driven CAPE build-up in the order of 300-600 J/kg (regionally higher values not ruled out) is forecast and scattered thunderstorms evolve beyond noon while shifting E/NE. This airmass features adequate shear vectors for organized thunderstorms with modest CAPE probably the mainly limiting parameter. However, strong shear probably offsets the CAPE issue to some extent and causes numerous well organized multicells or supercells in the broad level 1 area. In general rather high LCLs favor mainly a large hail and severe gust risk with this activity with an increasing large hail risk to the S part of the level 1 area, where a bit more CAPE exists.
Nevertheless, better BL moisture towards E Hungary and patches of better moisture elsewhere support a low-end tornado risk, mainly driven by regional (orographic) effects. Hence an isolated tornado even cannot be ruled out either.