Storm Forecast
Valid: Wed 10 Jun 2009 06:00 to Thu 11 Jun 2009 06:00 UTC
Issued: Wed 10 Jun 2009 00:20
Forecaster: PUCIK
A level 1 was issued for Central France, Germany mainly for severe wind gusts and tornadoes.
A level 1 was issued for E part of Baltic states, NE Belarus and Western Russia mainly for large hail and severe wind gusts and tornadoes.
SYNOPSIS
At midlevels, a ridge will stretch from the Mediterranean into the Black sea region and Russia. To the west a mid level low, with center over the Norway Sea will slowly translate southwards and at the same time, a strong impulse is expected to travel across Western Europe, affecting weather mainly over France and Germany. Strong flow is simulated around the impulse, reaching more than 35 m/s at 500 hPa level. At the surface a shallow high will lie over Russia, slowly moving eastwards and a complex of lows is forecast over Western and Northern Europe, with a trough stretching from Scandinavia into Turkey. A surface low, which will develop within region of the mid-level impulse will rapidly progress from Atlantic to Benelux by the end of forecast period, slightly deepening. Frontal zone, will run from the region of the above mentioned low, across Baltic States into Northern Russia.
DISCUSSION
... France to Germany....
In association with the mid-level impulse, strong QG forcing will result in the broad zone of stratiform precipitation around the frontal zone. GFS 12Z is quite optimistic with at least marginal instability release, but still, MLCAPEs values should stay below 500 J/kg. ECMWF also pusts slightly unstable conditions ahead of the cold front. Under the mid-level jet, strong DLS values are anticipated, over 25 m/s, with shear in the lowest 3 km over 20 m/s. As low level wind flow will strenghten due to the deepening surface low, at 850 hPa level wind speeds may reach 25 m/s and low level shear will exceed locally 15 m/s. These conditions would be very favorable for development of strongly forced convective line, probably involving bowing segments with accompanying threat of severe wind gusts. Furthermore, strong SREH is simulated, with values over 250 J/kg in 0-1km layer and with strong LLS at the same time, tornadoes can not be ruled out with such system. One of the detrimental factors might be that instability will be more of elevated nature, as suggested by GFS 18Z run or the presence of broad stratiform rain, in which the convection will be embedded. Models also slightly differ in the track of the belt of instability and therefore this area will be closely monitored for a possible update.
...Baltic states, Belarus, Western Russia...
Behind the warm front, humid airmass is advected with steep lapse rates at mid-levels. Surface heating will lead to the moderate instability release with most of the region having around 1000 J/kg of MLCAPE, locally with even higher values. Moderate wind shear, around 15 m/s, both at 0-6 km layer and 0-3 km layer suggest an organisation to multicells. Wind shear is expected to strenghten towards the evening hours ( 18/21Z) but at this time, instability should be dimnishing. Well organised, strong multicells will have a potential to produce isolated large hail. Moreover, high Delta Theta-E and enhanced DCAPE values suggest a potential for downbursts. Towards the evening, MCS might form, traveling NE wards, probably in the form of squall line. Severe wind gusts might accompany such system. To the east of Belarus a belt of enhanced SREH and LLS will exist, along with low LCLs, suggesting a slight potential for a briefly rotating updraft and a weak tornado, especially in the afternoon hours.
...Eastern Poland, Western Ukraine...
A belt of enhanced LLS is simulated by models, depicting a possible threat of tornadoes, but due to the lack of DLS or shear in the 0-3 km layer, Level 1 is not warranted at the moment. Update might become necessary later on.
