Storm Forecast
Valid: Sun 02 Jun 2019 06:00 to Mon 03 Jun 2019 06:00 UTC
Issued: Sat 01 Jun 2019 20:25
Forecaster: TUSCHY
A level 1 was issued across parts of Bulgaria and Romania into Moldova mainly for isolated large hail and locally excessive rain.
A level 1 was issued across far E-Ukraine into Russia mainly for large hail and severe wind gusts.
A level 1 was issued for parts of N-Turkey mainly for large hail and severe wind gusts.
A level 1 was issued across parts of W-Russia mainly for severe wind gusts and a low-end tornado threat.
SYNOPSIS
Blocking pattern persists over S-Europe. One subtle change is the gradual filling process of the cyclonic vortex atop the S-Adriatic/N-Ionian Sea. Another change is the approach of a mobile upper trough over NW Europe with rising heights over the North Sea and S-Norway/Sweden.
A vigorous depression enters the European forecast sector from the NW with a strong vortex being placed over N-Irleand and W-Scotland. This vortex stretches an extensive warm sector over W-CNTRL Europe, which features only modest BL moisture with no real connection to any substantial moisture source.
DISCUSSION
... SE Europe ...
Along the periphery of the upper low, an extensive area with 400-800 J/kg MLCAPE (regionally up to 1000 J/kg) is forecast. DLS in the 10-15 m/s range will support only transitional stronger updrafts with isolated hail, probably approaching the severe criterion on a sporadic/temporal scale. Slow-moving thunderstorms grow upscale and produce locally heavy rain.
A level 1 was added for parts of Bulgaria and Romania, where robust BL moisture resides along the NE fringe of the vortex with some curvature in forecast hodogaphs (also seen in enhanced SRH-3 forecasts). A few multicells with large hail and locally excessive rain are possible. Intense synoptic-scale lift should result in a large convective complex to lift N through the level 1 during the night with a transition to mainly a rainfall threat.
Further west, rapid clustering brings heavy rain on a broader scale but QPF amounts remain below any level threshold.
Over far E-Ukraine into Russia, another level 1 was added to account for the overlap 1500-2500 J/kg MLCAPE and 10-15 m/s DLS. Large to isolated very large hail and a few severe downburst events are forecast.
... N-France and Benelux ...
Confluent low/mid-level flow regime in the broad warm sector beneath slighlty lowering geopotential heights result in capped elevated CAPE (several hundreds J/kg). CI of GFS seems not plausible with unrealistic BL moisture anomaly forecast (up to 6K sfc dewpoint anomaly compared to realtime data over N-France into N-Germany). Hence prefrontal convergence zone ahead of the cold front in the warm sector/embedded in a surface trough should stay inactive throughout the day. We monitor this area in case of better LL moisture input than currently forecast and hence for spotty CI.
Isolated to scattered elevated thunderstorms erupt along/ahead of the eastward propagating cold front during the night but nothing severe is forecast with this activity. An extensive low probability lightning area was issued due to ongoing timing discrepancies of the cold front within the model suite but also due to uncertainties with CI of elevated convection in such a weakly forced setup.
... N-Turkey ...
Mountainous convection erupts during the day in an environment with 15 m/s DLS and 1000-2000 J/kg MLCAPE. A few thunderstorms develop in a diffluent upper flow regime and bring isolated large hail. Deeply mixed sub-cloud layer and inverted-V profiles with lots of DCAPE indicate a chance for a few severe downburst events.
... Level 1 over W-Russia ...
Environment features moderate shear with 15-20 m/s DLS and slightly lower values in the lowest 3 km. Straight hodographs with 100-150 m^2/s^2 SRH 1/3 in a 300-600 J/kg SBCAPE environment show a chance for better organized updrafts to split with some additional helicity input by deviating storm motions. LCL heights of 500-800 m AGL and the aforementioned kinematic environment indicate a low-end tornado risk with gusts approaching severe criterion on an isolated scale. We decided to upgrade this area with a small and conditional level 1.
