Storm Forecast
Valid: Mon 11 May 2015 06:00 to Tue 12 May 2015 06:00 UTC
Issued: Mon 11 May 2015 05:06
Forecaster: GATZEN
A level 1 was issued for southern Greece mainly for large hail and excessive precipitation.
SYNOPSIS
High across south-west Europe ridges into Central Europe. Downstream, a deep trough affects eastern Europe. Embedded digging vort-max crosses the southern Balkan Peninsula and enters the east Mediterranean south of Greece. In the wake of the trough, a swath of cool air below 800 hPa affects a broad region from the Baltic Sea across Poland and western Ukraine into the Balkans. With increasing ridging from the west, the cool air is capped and deep lapse rates will be quite poor across eastern Europe. Additionally, low-level moisture is limited. Better chances for deep moist convection exist across the Balkans.
DISCUSSION
Southern Balkans to western Turkey
Cold air advection goes on across the Balkans. Ahead of the approaching mid-level vort-max, a convergence zone has build from central Romania to the Aegean, with easterly winds over the Black Sea and western Turkey. Due to steepening deep lapse rates and remaining low-level moisture, CAPE evolved along the convergence zone as indicated by latest Thessaloniki sounding.
Thunderstorms have formed over Bulgaria in the area of this convergence as well as further west near the centre of the mid-level vort-max. Latest models indicate that convective activity will increase along the convergence zone from western Romania to the Aegean as well as near the approaching trough centre across Greece today. Additionally, convective activity will evolve over Turkey ahead of the approaching trough.
Well-organized thunderstorms are not likely given the weak vertical wind shear near the base of the trough. Increasing north-easterly flow in the wake of the trough will increase the low-level vertical wind shear, but this will be associated with cold air advection and stabilization in the evening hours. However, given the quite intense upper trough that moves across Greece, thunderstorms near the centre may be quite intense, though. Locally large hail and excessive precipitation is therefore not ruled out, especially across southern Greece.
