Storm Forecast
Valid: Tue 14 Oct 2025 06:00 to Wed 15 Oct 2025 06:00 UTC
Issued: Mon 13 Oct 2025 20:17
Forecaster: TUSCHY

A level 2 was issued for the Balearic Islands and offshore areas E mainly for excessive rain.

A level 2 was issued for NE Sardegna and E Corsica mainly for excessive rain.

A level 1 surrounds both level 2 areas with a similar hazard, but lowered probabilities. In addition we expect numerous waterspout reports.


SYNOPSIS

Weak dynamics prevail over the W Mediterranean, so the messy pattern with hard to forecast QPF maxima continues. As seen yesterday, a tad stronger capping than anticipated and a weaker upper wave both resulted in less thunderstorms over most of the Balearic Islands in an otherwise favorable environment for organized DMC activity.

Yesterday's filling low-amplitude wave shifts E atop the W Mediterranean and crosses Sardegna and then Sicily E/SE while dissolving. At the same time another mid/upper trough takes shape over S France and starts to move SE over the W Mediterranean Sea during the overnight hours. This structuring trough is already present in latest remote-sensing data.
IFS-ENS has only weak signals for a surface response with the first wave although WRF-NMM keeps a meandering weak depression S of the Balearic Islands for most of the forecast period with other models indicating more of a zonal MSLP channel offshore of N Africa with embedded smaller-scale vortices.
The story turns more coherent with the approaching second wave from the NW, where more focused MSLP signals in the ENS emerge over the Tyrrhenian Sea. This results in a dominant cyclonic flow regime atop the W Mediterranean for the night. At the same time we see a weak/modest Scirocco event over the Strait of Sicily. All that results in various mesoscale convergence zones with one pointing from the Balearic Islands E towards Sardegna and another one organizing E/SE of Sardegna.

Elsewhere, the hostile conditions for DMC activity persist over most of Europe as a cooler/drier northerly flow regime between the blocking anticyclone over NW Europe and an extensive upper low over E Europe/W Russia persists.

DISCUSSION

... W to CNTRL Mediterranean ...

Atop the Balearic Islands, initial high-energetic airmass with MUCAPE in excess of 2000 J/kg (e.g. Mallorca-Son Bonet with 2195 J/kg, yesterday at 12Z) advects E betimes in response to the structuring cyclonic flow regime and attendant more N-erly BL flow.
Ongoing from the previous night expect numerous erratic (but overall eastward creeping) thunderstorms within weak shear and adequate CAPE. The risk for locally back-building convection is still present and if we get such a training cluster next to/over one of these Islands, we could once again see hourly rainfall amounts in the 50-80 l/qm range. We kept the level 2 confined to the eastern Islands, where the more humid airmass sticks around longer and where some models have more focused BL convergence along the periphery of the mentioned LL vortex/low pressure channel.

The other area of interest evolves during the evening into the overnight hours E of Sardegna and atop the Tyrrhenian Sea. Strengthening southerly BL flow with moisture advection and more focused positive thickness advection ahead of the approaching upper wave from the NW create a broad area with slow moving to temporarily back-building convection with heavy to excessive rain. Shear especially in the lowest 3 km is a tad stronger than further W, so even transient storm rotation along a convergence zone with deviating storm motion is possible.
This should be mainly an offshore risk as clustering convection shifts S with laid out outflow boundaries serving as foci for temporal training. The overall coast-parallel BL flow E of Sardegna should keep the training risk more offshore and confined to the S part of Sardegna.

Beyond midnight, as the BL flow turns more easterly over Corsica and NE Sardegna in respoonse to the cyclonic flow regime, a training coastal convection risk increases and we could see a few localized 80-100 l/qm sub-6 hourly rainfall amounts with potential flash flooding. This time frame caused a local level 2 upgrade. Otherwise we kept the offshore convection in a broad level 1 with less obvious foci for more concentrated activity (e.g. Balearic Islands E has a focused moisture/wind confluence, which increased confidence for a level 2).

During the end of the forecast we expect a few slow moving thunderstorms S of the Gulf of Squillace but this risk does not yet need any level area.

We added parts of Sicily to a level 1 mainly to cover the EZ model suite, which is enthusiatic in sparking daytime thunderstorms during the passage of the dissolving first wave and nocturnal clusters from the NW, which approach during the end of the forecast. The rain risk will be of most concern.

S Greece could see a few slow moving coastal thunderstorms with heavy rain but the general risk is too spotty for a level 1 upgrade.

Parts of N Algeria/Tunisia will see a few high-based thunderstorms with a few strong to severe downburst gusts and isolated hail.

All those areas could see a few waterspout events mainly along focused LL convergence zones.