Storm Forecast
Valid: Sun 09 Aug 2015 06:00 to Mon 10 Aug 2015 06:00 UTC
Issued: Sat 08 Aug 2015 22:53
Forecaster: TASZAREK
A level 2 was issued for S Spain mainly for the large and very large hail, severe wind gusts and excessive precipitation.
A level 2 was issued for SE France mainly for the large hail, severe wind gusts and excessive precipitation.
A level 1 was issued for S Spain mainly for the large hail and severe wind gusts.
A level 1 was issued for parts of Benelux, S Germany, E France, Switzerland, W Austria, W Czech Republic, N Italy mainly for the excessive precipitation and large hail.
A level 1 was issued for W Turkey mainly for the excessive precipitation.
A level 1 was issued for NE Poland, Latvia, NW Belarus, S Lithuania mainly for the large hail, severe wind gusts and excessive precipitation.
SYNOPSIS
Most of the central, southern and eastern Europe is covered by the warm and moist tropical airmass with 850 hPa temperature exceeding 20C. Jet stream encircling polar airmass extends from Greenland through British Isles, Scandinavia and N Russia. Cut-off over southern France moves during the forecast period SEwardly. Small cut-off occurs also in the S Baltic and moves NEwardly. Most of the instability over Mediterranean remains capped.
DISCUSSION
...S Spain...
Easterly influx of boundary layer's moisture content with mixing ratios up to 15-16 g/kg will take place over the SE coast of the Spain. Within the overlap of elevated mixed layers and lapse rates up to 8 C/km such a conditions will create CAPE values up to 3000 J/kg. Locally increased mid-level flow with DLS over 20 m/s and locally uncapped thermodynamic instability will provide good conditions for multicellular and supercellular thunderstorms. Given impressive boundary layer's moisture content, steep lapse rates and good wind shear large to very large hail can be expected within the level 2 area. Large directional shear (NWerly flow in mid-levels and SEerly flow over the surface) and MLS exceeding 20 m/s may result in a squall line capable of producing severe wind gusts. CI should take place in the afternoon hours, while the highest threat for the severe weather over level 2 area will fall on the late afternoon hours.
...Central Europe...
Ahead of the cut-off over S France, the overlap of DLS exceeding 25 m/s, CAPE up to 1500 J/kg and good QG-lift will take place. Thunderstorms over this area should be active during the whole forecast period and moving Serly (over the eastern side of the cut-off) may be capable of producing severe wind gusts and large hail. NWP models indicate that large multicell clusters with presumably embedded and isolated supercells over SE France, NW Italy and Switzerland are likely. Over S Germany, N Italy and Benelux the main threat resulting from the low storm motion of the convective cells and high PW values (40-45 mm) will be excessive precipitation and flash floods. Except thunderstorms within eastern side of the cut-off, CI over the level 1 area should take place in the afternoon hours and thunderstorms should be active until nighttime hours.
...Baltic Countries...
Small cut-off that moves NEwardly provides good QG-lift in the area where the CAPE 1000-1500 J/kg overlaps mostly with DLS ~ 15 m/s and locally 20 m/s. Within such setup, thunderstorms will form most likely on the eastern side of the cut-off and will be active during the whole forecast period and cut-off passage. Multicell clusters are the main forecast convective mode. However locally increased 0-3km SRH up to 150 m2/s2 may induce the occurrence of the embedded or isolated supercells capable of producing large hail and severe wind gusts. In the late evening hours, thanks to diurnal heating, thunderstorms should regenerate and form MCS over Latvia that will move NEsterly. Within such feature severe wind gusts and excessive precipitation (in the environment with PW over 40mm) are likely.
...W Turkey...
Internal airmass thunderstorms in the low sheared environment are forecasts to occur in the afternoon hours. Although vertical wind shear is likely to be weak, no good thunderstorm organization is forecast. However, low storm motion and impressive PW values (40-45mm) create threat for the excessive precipitation and local flash flood phenomena.
