Storm Forecast
Valid: Fri 04 Aug 2023 06:00 to Sat 05 Aug 2023 06:00 UTC
Issued: Thu 03 Aug 2023 20:42
Forecaster: PUCIK
A level 2 was issued in a belt from Italy through the Adriatic Sea into Croatia, Bosnia and Hungary mainly for large to very large hail, severe wind gusts and heavy rainfall.
A level 1 was issued across N Italy, S Italy, Algeria and Tunisia mainly for large hail and severe wind gusts.
A level 1 was issued across Slovakia, Poland, W Ukraine and W Romania mainly for heavy rainfall and to the lesser degree for severe wind gusts and large hail.
A level 1 was issued across Russia mainly for severe wind gusts.
SYNOPSIS
Main synoptic-scale feature will be a deep trough located over France and N Spain at 06 UTC. The base of the trough will move across the Mediterranean towards Italy and the Adriatic Sea. Strong synoptic-scale lift is forecast ahead of the trough. Strong flow is wrapped around the trough with windspeeds up to 50 m/s at 300 hPa. Another trough will move across N Russia. Both troughs are connected via a pool of low geopotential heights over Scandinavia and N Atlantic. Closer to the surface, a wavy frontal boundary will run from the Mediterranean through Italy, N Croatia, Hungary into SE Poland and further through Belarus into Russia. The main thunderstorm activitity will be confined to the boundary.
... Italy , Adriatic Sea coastlines ...
Strong storms will likely be ongoing over the northern edge of the Lvl 2 already in the morning hours. Further storms are expected to develop during the day and the coverage will increase rapidly with the approach of a sharp-trough. CAPE-shear parameter space suggests high likelihood of severe storms. Forecast profiles and hodographs show around 25 m/s of 0-6 km bulk shear with mostly straight hodographs and abundance of CAPE over -10 deg C isotherm, meaning high risk of very large hail. It is likely that one or more linear systems develop as storms grow upscale and will move across the Adriatic Sea towards Croatian coastlines with risks of severe wind gusts (given > 15 m/s of 0-3 km shear) and also very heavy rainfall (given moist profiles). Storms will likely become elevated towards the night and the end of the forecast period, reducing the wind gust risk to some degree.
... Bosnia, NE Croatia, Hungary, Serbia, Slovakia, W Romania, SE Poland ...
Isolated storms, some of which will likely be supercells, may develop during the day, posing threat of large hail or severe wind gusts given > 20 m/s of 0-6 km bulk shear. The main wave of thunderstorms activity is forecast in the evening to overnight hours. The increase in activity will be associated with increasing lift through warm-air advection regime along the intensifying frontal wave. More isolated storms, likely in the form of supercells, are forecast especially along the S and E parts of the highlighted area, posing risks of (very) large hail and severe wind gusts. A convective system, at least partly elevated, is forecast to form over Croatia/Bosnia and move towards Hungary, Slovakia and Poland. The system will move rapidly NE-wards in the intensifying low-level wind field as the surface pressure falls along the wave in the night hours. The system will pose risks of very heavy rainfall and severe wind gusts. The severe wind gust risk will be pronounced further E, where surface-based CAPE will be still present. Strongly curved hodographs with 0-1 km shear > 10 m/s is simulated in the path of the system during the night, but tornado threat will be significantly reduced or completely diminished by the elevated nature of the storms.
... N Algeria, Tunisia to S Italy ...
Models disagree concerning the convective coverage over this area. Despite the disagreement, the front will move over the area, combined with the synoptic-scale lift provided by the approaching trough. At least isolated storms are very likely to form and will become supercells given strong deep-layer shear with threats of large hail and severe wind gusts.
... Russia ...
Strong lift in the left-exit region in the jet-streak will aid in priming the environment for widespread initiation along the progressing cold front. Expect several linear segments or a squall line with isolated threat of severe wind gusts.
