Storm Forecast
Valid: Sat 05 Aug 2023 06:00 to Sun 06 Aug 2023 06:00 UTC
Issued: Fri 04 Aug 2023 22:38
Forecaster: PUCIK/KUZMENKO
A level 2 was issued across Serbia and Hungary for damaging wind gusts, heavy rainfall and large hail.
A level 2 was issued across Slovakia and S/SE Poland mainly for heavy rainfall, severe wind gusts and to the lesser degree for tornadoes and large hail.
A level 2 was issued across NE Poland, SE Lithuania and NW Belarus mainly for severe wind gusts, tornadoes and heavy rainfall.
A level 2 was issued across NW Greece mainly for heavy rainfall and severe wind gusts.
A level 1 was issued across W Slovakia, central Poland, Lithuania, Latvia and SE Estonia mainly for heavy rainfall and to the lesser degree for severe wind gusts.
A level 1 was issued across S Bosnia, North Macedonia, Albania, W Romania and W Bulgaria mainly for large hail, severe wind gusts and heavy rainfall.
SYNOPSIS
A trough over Italy will detach from lower geopotentials over NW Europe by Saturday 06 UTC. The resultant low will move E/SE towards the Ionian Sea. Further W, a short-wave will move across BENELUX and N France in the late afternoon to evening hours. Abundant low-level moisture will be confined to the wavy frontal boundary that will run from NW Greece, W Serbia into Hungary, Slovakia, Poland, N Belarus and E/SE Baltic countries. Severe thunderstorms are forecast in this belt.
DISCUSSION
... Serbia, W Romania, Hungary, Slovakia, SE Poland ...
Numerous storms are forecast to be ongoing across Slovakia/S Poland in the morning hours. These storms will move N and clouds will break especially over the E part of the area. Surface heating will increase MLCAPE values, which may locally reach 2000 J/kg. Strong deep layer shear will support well-organised storms. Hodographs will be mostly straight with increasing 0-3 km shear towards the evening hours. Stronger low-level shear, along with curved hodographs, is forecast over central-E Poland, where tornado risk will also be present in the afternoon hours. First, isolated storms will form and organize rapidly into supercells with threats of large hail and/or severe wind gusts. Towards the late afternoon and evening, one or more systems will form over Serbia and S Hungary in response to frontogenesis and move towards N/NW. There will be high risk of severe wind gusts at first, especially over the S and E half of the Lvl 2, giving way to higher risk of heavier rainfall in the late night hours as storms become elevated.
... NE Poland, Belarus, Baltic countries ...
Already in the early morning, first storms are expected to travel across Poland along the warm wave of the frontal boundary. The storms will be elevated with a risk of heavy rainfall. In the afternoon, redevelopment of storms is forecast along and to the N/NW of the warm wave, initiated by isentropic lift in strong warm air advection regime. As the low-level flow strengthens towards the late afternoon, large and curved hodographs are simulated with majority of shear in the bottom 1 km. A risk of tornadoes will be present if surface based storms manage to develop across central-E Poland, Belarus and SE Lithuania. Severe wind gust threat will also be high for any system that remains on the warm side of the boundary. However, majority of storms are expected to initiate on the cool side of the boundary, growing upscale and travelling N/NW in an elevated form. The primary hazard will be heavy rainfall, followed by severe wind risk, which will increase from W to E. Models disagree on the position of the elevated system at the end of the forecast period. ECMWF is currently most aggresive concerning the NW extent of the tongue of MUCAPE.
... NW Greece ...
Heavy rainfall and severe wind gust risk is forecast with an MCS approaching from the Ionian Sea in high CAPE and strong shear parameter space, including 0-3 km bulk shear over 15 m/s. Storms are forecast to weaken in the late afternoon to evening hours.
... N France ...
A band of low-topped showers may develop along a boundary that moves over the area in the evening hours. Models are in disagreement concerning the degree of CAPE and if storms can develop at all, but 0-1 km bulk shear around 15 m/s is forecast along with curved hodographs and around 100 m2/s2 of SRH in 0-500 m layer. Tornado risk will be present if more robust updrafts develop, but the model disagreement is currently too high to warrant a lvl 1.
