Storm Forecast
Valid: Tue 13 Aug 2024 06:00 to Wed 14 Aug 2024 06:00 UTC
Issued: Mon 12 Aug 2024 21:47
Forecaster: PUCIK/BAART DE LA FAILLE/ADAMOVSKY
A level 2 was issued across Iberia mainly for large to very large hail, severe wind gusts and heavy rainfall.
A level 2 was issued across France, E BENELUX, NW Germany for large hail, severe wind gusts and heavy rainfall.
A level 1 was issued over Denmark for heavy rainfall and large hail.
A level 1 was issued across Germany, N Italy, Switzerland, Austria, SW Czechia mainly for large hail, heavy rainfall and severe wind gusts.
A level 1 was issued across central Italy mainly for severe wind gusts.
... Iberia ...
Two short-wave troughs are expected to cross the region, the first already in the morning hours, the second one following in the evening, arriving over the Balearic Sea by the night. A dryline is forecast to set up over the E-coastline with a pronounced overlap of steep lapse rates and abundant low-level moisture, yielding MLCAPE values over 2000 J/kg. With 0-6 shear exceeding 15 m/s, a mix of multicells and supercells can be expected. Storms will be initiated by the dryline, orography and weakly defined cold front. Coverage of storms will decrease from N to S owing to the increasing CIN values. Models suggest only limited CI in central-east, but with the highest potential for isolated supercell development with large to very large hail and severe wind gusts. Higher storm coverage is expected to the the N/NE, where CAPE 1000-1500 J/kg with no CIN is anticipated. 0-6 shear will reach up to 15 m/s, with some disagreement in models. A mix of severe weather threats is expected, including large hail, severe wind gusts and heavy rainfall. Heavy rainfall threat will ramp up in the evening with storm clustering.
During the night, as the trough moves over the sea, storms are expected to initiate there. The coverage is currently uncertain with large differences among the models. Severe storms can be expected given 15-20 m/s of 0-6 km shear and 3000+ J/kg of MLCAPE. The storms may turn elevated over the sea during the night.
... France ...
Abundant convection may already exist over S France in the morning hours, aided by the appraoch of a trough from France. Isolated large hail and flash flooding may occur in environment of high MUCAPE (2000-2500 J/kg) with shear locally up to 10 m/s.
Further initiation is expected towards the early afternoon, especially over the Massif Central, with storms spreading towards N France and BENELUX. MLCAPE will reach 2500-3500 J/kg, supporting powerful updrafts. Shear will decrease from NW towards E. Mostly multicell clusters are forecast with flash floods, large hail and severe wind gusts (precipitation loading term). Towards the NE more dry profiles will increasine the threat for wind gusts due to evaporation. Towards the NW, increased 0-3 km shear also enhances the risk for severe wind gusts.
... Benelux/W-Germany ...
Very high CAPE is forecast, locally reaching 4000 J/kg. Shear will stay rather weak, allowing mostly for pulse storms or multicell clusters. Lack of clear forcing makes the forecast of initiation, coverage and the timing of the storms very difficult. There are also large differences among the models. Surface convergence seems quite random over this areas. It is possible that the outflow boundaries will play a determining role in the initiation. The first round of storms can be expected from late morning till afternoon hours. High res models suggest the highest coverage over W Germany. In the evening, further storms will spread here from France with outflow boundaries providing lift. Increase in the coverage in the evening and night may be due to the increase in the WAA. Overnight storms will likely be elevated. Afternoon storms will bring especially large hail and severe wind gusts with local flooding, whereas overnight storms may bring especially heavy rainfall.
Either in the later afternoon or early evening some SB convection will initiate with mainly a threat of large hail, possibly locally wind gusts or flash flooding, and/or convection from France will propagate over Belgium in the late evening and overnight (likely elevated) with main threat for large hail and local flash flooding.
... Central to S Germany/Austria/Switzerland/N Italy/W Czech Republic ...
Early afternoon initiation is expected over the Alps and Sumava mountains, in 1000-1500 J/kg MLCAPE and weak vertical shear, with barely any storm motion. High LCLs are simulated by the models. Pulse storms with main threat of flash flooding and severe wind gusts and isolated large hail are forecast. The risk of large hail will be the highest over Bavaria and northern Austria, where the highest CAPE is simulated.
... Italy ...
Models agree on scattered CI over the mountains. Environment will be characterized by 500-1500 J/kg SBCAPE, bulk shear below 10 m/s and very dry profiles with pronounced inverted V. Single cells/pulse storms with main threat of wind gusts/downbursts are forecast.
