Storm Forecast
Valid: Sun 03 May 2020 06:00 to Mon 04 May 2020 06:00 UTC
Issued: Sat 02 May 2020 21:13
Forecaster: KAHRAMAN

A Level 1 is issued for E Bulgaria, NW Turkey, and parts of S Romania for excessive precipitation.

A Level 1 is issued for SW Turkey mainly for large hail.

A Level 1 is issued for parts of E Ukraine and further north for excessive precipitation.

SYNOPSIS

A mid-tropospheric ridge over the Iberian Peninsula with its associated warm air, and the cold air mass over the Norwegian Sea form moderate temperature gradients and zonal flow over the Western Europe. A polar jet turns southeast following the Adriatic Sea, ending up parallel to the Southern Turkish coasts, without an important transformation during the forecast period. Meanwhile, a trough over Central Europe moves further east, while the geopotential gradient weakens in the southern tip over Balkans, leading to a cut-off.

DISCUSSION

... Eastern Europe ...

The warm air advection in front of the meridional cold front over Eastern Europe carries 7-9 g/kg mixing ratio values from the Black Sea and Caspian Sea towards Ukraine, Belarus, and parts of Southern and Western Russia. Mid-level lapse rate values of 7 K/km overlap with the moist air over the area, likely developing clusters of thunderstorms. The relatively high moisture availability, and nearly-saturated air throughout the troposphere might boost the precipitation efficiency, resulting in locally high rainfall rates. Due to weak circulation, deep layer shear is quite low, and storms should be unorganized. However, any storm formed would also be almost stationary for the same reason, increasing the flash flood risk where rainfall rates are high. Local eddies promote moisture advection also around southeastern Balkans, which results in similar environmental conditions. A few storms over Northwestern Turkey, and parts of Bulgaria and Southern Romania would assess locally excessive precipitation potential. Southern Turkey possesses high 0-6 km shear, but risk for severe convection is limited due to lower CAPE values. A few locations might experience hail of ~2cm size or accumulation over Southwest Turkey, and an isolated tornado is not ruled out, although the chances are low due to the marginal low level shear.

... Parts of Norway, Sweden, UK, and Central Europe ...

Patches of modest moisture advection and weak instability aloft make up a few hundred J/kg of CAPE over parts of Northern Europe. Since the confidence is not high regarding the possible convective cloud tops, low probability thunder areas are issued over parts of Southern Scandinavia and NE England. Adritic Sea is capped, but partial lands around it has the potential. Southern Italy has an overlap of high shear and low CAPE, promising well organized convection, but any hazard is not warranted in particular. A night-time non-surface based convection is possible over Western Germany and Southern Netherlands as well.