Storm Forecast
Valid: Sun 08 Nov 2009 06:00 to Mon 09 Nov 2009 06:00 UTC
Issued: Sat 07 Nov 2009 20:42
Forecaster: TUSCHY
A level 1 was issued for parts of the western and central Mediterranean mainly for excessive rainll and isolated tornadoes.
A level 1 was issued for SW France mainly for large hail and isolated tornadoes.
A level 1 was issued for SW Turkey mainly for excessive rainfall, large hail and isolated tornadoes.
SYNOPSIS
A deep cyclonic vortex is centered over central Europe and steers numerous disturbances around its fringes. Widespread showers/thunderstorms over most parts of Europe are the result. Conditions over NE-Europe are more stable with cold conditions over far NE-Europe.
DISCUSSION
... Western / Central Mediterranean ...
A deep vortex has established over the central Mediterranean with attendant cyclonic flow affecting those areas. Widespread convection is anticipated with the most widespread activity along the luv-side of the islands. Those areas were highlighted with a high thunderstorm probability. In addition, a fetch over the northwestern Mediterranean was excluded to reflect the time period for the LL airmass to ingest enough moisture for enhanced updraft strength.
Thunderstorms will be in an overall weakly sheared environment, so weakly organized multicells are the main storm mode, probably clustering betimes. A low WBZ and locally moderate CAPE are adequate for isolated large hail next to excessive rainfall, especially in the level 1 areas. Another point will be the high LL CAPE release over the western Mediterranean. Particularly when convergence zones can set up, spouts will be a distinct possibility, also enhanced along the coastal areas. The activity will keep going throughout the forecast, assisted by the cold troposphere atop of the warm Mediterranean.
... SW- France ...
Steep lapse rates and some LL moisture support a favorable environment for deep convection, also onshore over SW-France. In addition, diurnal heating and -30°C at 5km will likely result in a diurnal maximum, probably during the noon/afternoon hours. Isolated large hail and strong wind gusts are the primary risk, although an isolated tornado report over SW-France can't be ruled out, given enhanced LL shear, onshore CAPE and low LCLs. The overall risk rapidly decays during the night hours.
... SW-Turkey ...
Thunderstorms are forecast until roughly 18 UTC beneath a rapidly eastward moving, sharp trough. A cluster of storms, probably ongoing over the Aegean Sea during the early morning hours, affects the SW-coast of Turkey with excessive rainfall, strong to severe wind gusts, large hail and isolated tornadoes. Despite weak DLS values, shear in the lowest 3km is adequate for organized convection and only modest EL temperatures indicate that this shear distribution already affects most parts of the updraft ( forecast cloud tops up to 7-8 km). Also, rapidly increasing LL shear along the coast results in an adequate CAPE/shear overlap with impressive LL CAPE values in excess of 200 J/kg. This magnitude of CAPE could even result in an isolated strong tornado event due to rapid vortex stretching. However, overall storm mode /cluster/ and decreasing activity during the afternoon/evening hours preclude a level 2 for now.
Further east (east of the forecast area), rapidly increasing shear and high CAPE point to a favorable environment for supercells with very large hail/damaging wind gusts and tornadoes.
... W-Romania ...
Thunderstorm probabilities gradually increase during the night/early morning hours, but current indications are that CAPE build-up will be too scarce for strong updrafts. Despite favorable shear and approaching forcing from the south, only low probability thunderstorm chances were included. If the risk increases, a subsequent upgrade may become necessary for severe wind gusts/hail.
