Storm Forecast
Valid: Wed 02 Aug 2017 06:00 to Thu 03 Aug 2017 06:00 UTC
Issued: Tue 01 Aug 2017 21:10
Forecaster: PUCIK
A level 2 was issued for NE Belarus and NW Russia mainly for severe wind gusts, tornadoes and large hail.
A level 1 was issued over E Poland and Belarus mainly for large hail and severe wind gusts.
A level 1 was issued over the Alpine range mainly for large hail, severe wind gusts and excessive precipitation.
A level 1 was issued for E Spain mainly for large hail and severe wind gusts.
SYNOPSIS
The main macro-synoptic feature will remain to be a large cyclonic vortex with two separate centers over the Atlantic and Scandinavia, with strong mid to upper tropospheric flow surrounding the vortex in a belt from UK across Germany, Poland into NW Russia. A short-wave trough will lift over E Iberia towards NE and subsequently turning towards the Balearic Islands. A separate vortex will reside over W Turkey. Main focus for the storm development during the day will be a wavy frontal boundary with moist airmass along and ahead of the boundary running from NW Russia towards SE Poland, Czech Republic, S Germany and France.
DISCUSSION
... Baltic States, NE Belarus, NW Russia ...
Ahead of the fast advancing cold front, moist airmass will be advected over the region with dewpoints reaching between 16 and 22 °C. In combination with mid-tropospheric lapse rates of 6 to 6.5 K/km, several hundreds to around 2000 J/kg of MLCAPE are simulated over the region by NWP. Extent of CAPE will depend likely on the cloudiness and precipitation advected in the morning hours from SW. With strengthening flow aloft, strong bulk vertical wind shear is forecast, with over 20 m/s in the 0-3 and 0-6 km layer, suggesting that much of the shear will be confined to the lower troposphere. Forecast hodographs show veered wind profiles with enhanced SRH values especially in the WAA regime at the eastern edge of the plume of the moister airmass. Conditions will befavourable for well organised convection, including supercells and bow-echoes. Fast moving cold front may support quick up-scale growth of convection with the highest threat being severe wind gusts as 850 hPa flow reaches 20 m/s. In case that isolated supercells manage to persist, strong tornadoes are not ruled out with LLS up to 15 m/s, enhanced SRH and quite low LCLs, particularly over the northern part of the area. Large hail will be likely with supercells as well. Lvl 2 is issued for the area with the best overlap of CAPE and strong lower tropospheric shear.
... Belarus to E Poland ...
Moderately unstable airmass is simulated ahead of the cold front with vertical wind shear increasing towards the north. Across NE Poland and Belarus, DLS will be sufficient for supercells while over S Poland, shear will be conducive for multicellular convection. Chances for initiation decrease as well from north to south and over S Poland, initiation will be tied mostly to the orography. Large hail and severe wind gusts will be the most likely threats from the well organised and stronger storms.
... Alpine range ...
South of the cold front, abundant lower tropospheric moisture is simulated with around 7 K/km lapse rates, contributing to 1000 to 2000 J/kg of MLCAPE. In conjunction with DLS ranging from 15 to 20 m/s over the whole range, well organised convection may be expected, including some supercells. Stronger cells will be capable of large hail and severe wind gusts. Excessive precipitation event is also likely given the rich topography of the area. Development will start in the early afternoon and storms will subside near the sunset. Models do not simulate storms moving too far towards the lowlands due to the CIN and lack of lift.
... E Spain ...
In conjunction with the passing trough, at least isolated storms may form in low to moderate CAPE inland. In the environment of steep lapse rates and at least 15 m/s of DLS, storms may be well organised, capable of large hail and severe wind gusts.
