Storm Forecast
Valid: Tue 14 Jun 2016 06:00 to Wed 15 Jun 2016 06:00 UTC
Issued: Mon 13 Jun 2016 21:46
Forecaster: DAFIS
A level 1 was issued for SW Russia, Ukraine, Moldova and Romania mainly for excessive rain, severe wind gusts and tornadoes.
A level 1 was issued for parts of Turkey mainly for excessive rain and large hail.
A level 1 was issued for parts of Poland, Czech Republic and Slovakia mainly for excessive rain and to a lesser extent for tornadoes.
A level 1 was issued for Italy mainly for large hail and excessive rain.
A level 1 was issued for Croatia, Slovenia, SE Austria and NW Hungary mainly for excessive rain and large hail.
A level 1 was issued for Spain mainly for large hail and severe wind gusts.
SYNOPSIS
A long-wave trough with a negative tilt stretches from NW Europe towards Turkey, while a mid-level low is forecast to form over the UK Isles. Embedded disturbances of the trough will be responsible for most of the severe weather events that we expect during Tuesday and first hours of Wednesday. The sub-tropical jet stream in West Mediterranean is found much more north than over Greece-Turkey, but areas with good overlap of wind shear and CAPE are limited, mostly over parts of Spain and Italy. On the surface, frontal activity is weak, with a rather staled warm front over Ukraine, where we can notice a strong low level convergence zone. A few thunderstorms are also expected in the UK, Central Europe, with a better chance for DMC over Poland and NW Balkans. NW Italy will be under the left exit of the jet stream, as well as parts of W France and some organized activity is expected.
DISCUSSION
.... SW Russia, Ukraine, Moldova and Romania - Turkey....
Strong low level south flow will advect warm and moist air masses, while the mid level flow is weak and DLS below 10 m/s. Also weak advection of PV will assist CI late in the morning apart from diurnal heating. Slowly moving storms that will form in the level 1 area will be capable of producing excessive rainfall and severe wind gusts where cold pools will form. Tornadogenesis will also be a threat, but we do not expect any mesocyclone to be formed. Low LCL heights and 10-15 m/s of LLS will pose a threat for landspouts mostly in Ukraine. Storm activity will continue during the night.
Also for West and North Turkey the advection of a moist air mass as well as PV advection over the continental parts, low level convergence and steep mid-level lapse rates will lead in the development of many storm cells. The area will be at the left exit of the jet stream, so CIN in the morning will be of less concern for CI near the coasts and later on storms will be able to produce excessive rainfall and large hail, mostly at the areas with a better overlap of 15 m/s DLS and decent CAPE. Complex and steep orography of Turkey will also enhance the storm activity.
.... Poland, Czech Republic and Slovakia ....
Latest model guidance suggest high PW values over large parts of Poland where also low level convergence may lead to stationary storms producing excessive rain and/or marginal small hail. Better ingredients for excessive rainfall are found in the most northern (much better PVA-moist BL) and most southern parts of level 1 area (much better PW), but a weak tornado cannot be ruled out, especially late in the evening, when high resolution models forecast a good overlap of LLS and CAPE. Again, a non-mesocyclonic tornado may occur and storms could continue pulsating well into the night.
.... Italy, Croatia, Slovenia, SE Austria, NW Hungary ....
A short-wave trough crosses the area in the evening - night hours, and storms will be capable to become supercells into this strongly sheared and unstable environment. Storm activity is expected to be quite messy in Central and South Italy, but in the northern parts and later during the night in NE Adriatic Sea, well organized storms will be capable of excessive rainfall, large hail and severe wind gusts. One or two waterspouts or weak tornadoes cannot be ruled out during the morning hours in N Adriatic Sea. On the other hand, best time frame for excessive rainfall for SE Austria and NW Hungary will be between 15z and 21z on Tuesday, as PW is over 30 mm and generally the flow will be weak.
.... Spain ....
Last but not least, Spain is expected to experience some thunderstorm activity. Although there are several concerns about CI, every storm that will form in NW Spain, taking into account that a dry layer between 700 and 850 hPa exists and DLS is about to exceed 20 m/s, large hail and severe wind gusts are expected. During the night and first hours of Wednesday, models show CI in East Spain, mostly offshore, south to Balearic Islands. As the jet stream is above the unstable air mass, a MCS may form able to produce larga hail.
