Storm Forecast
Valid: Wed 14 Jan 2009 06:00 to Thu 15 Jan 2009 06:00 UTC
Issued: Tue 13 Jan 2009 23:47
Forecaster: PUCIK

SYNOPSIS

Both low pressure systems over the Europe, one over Norway and another over the Central Mediterranean are expected to lose significance and slowly fill during the forecast period. Moreover, a high will settle over the Scandinavia and a further advection of arctic airmass into Central Europe is predicted in the following few days. Meanwhile, a modified stable airmass takes up most of Europe. A mid level cut off low, placed over Italy, which has advected warmer and moister airmass in strong SW flow will also fill. This feature as well as the accompanying surface low have been a loci for thunderstorm activity during the last forecast period. The activity is therefore expected to quickly subside.

DISCUSSION

... Eastern Ionian sea, Greece...

An advection of warm and humid airmass is expected on the forward side of the weaking low. A tongue of instability will have formed by 06Z from the Ionian to the Adriatic Sea, although, as simulated by GFS, instability should be mostly marginal. MLCAPEs might exceed 800 J/kg only in the southern parts. Quite strong synoptic-scale lift combined with the strong low level flow convergence especially over the coastal areas will aid in the thunderstorm initiation. Thunderstorms should be also ongoing from the previous period and the latest satellite loop shows a linear convective system over Italy and Ionian Sea, moving eastwards. Strong flow induced by the low will result in 15 - 20 m/s of wind shear in the lowest 3 km ( for example, 850 hPa flow should reach 20 m/s especially over the coastal areas). At the same time, veering winds with height will increase the SREH values to more than 250 J/kg in 0-3 km layer. Such favourable conditions will rapidly diminish after 09Z.


The greatest threat is expected in the morning hours, between 06Z and 09Z, when the convective line is expected to reach the area. Favourable wind profiles and low LCLs suggest tornado/waterespout potential will exist, especially in the coastal areas with the best instability / low level shear overlap. Marginal severe wind gust risk should also develop, as suggested by 15 - 20 m/s wind shear component to low level boundary. Hail can also occur although its size is not expected to meet the severe weather criteria.