Storm Forecast
Valid: Tue 16 May 2017 06:00 to Wed 17 May 2017 06:00 UTC
Issued: Mon 15 May 2017 21:54
Forecaster: DAFIS
A level 1 was issued for parts of Ukraine, Hungary and Romania mainly for excessive preciitation and large amounts of small hail.
A level 1 was issued for S Italy mainly for excessive preciitation and large amounts of small hail.
SYNOPSIS
A longwave trough is crossing a large part of East Europe, resulting in widespread thunderstorm activity during Tuesday and a meso-low is about to form over the Ionian Sea. At the same time, a ridge is stretching from NW Africa towards S Scandinavia, bringing warm air masses mostly to Spain and France. The cyclone in W Russia is accompanied by a vorticity max in the mid/upper levels but apart from a convergence line in N Ukraine, cold LL air masses suggest mostly stable conditions. A cold front from the Atlantic Ocean is approaching the coasts of Spain and France where some storms may pop-up in the evening embedded in the stratiform rain bands which may produce note-worthy rainfall amounts. During the late afternoon night a vorticity lobe over the Ionian Sea will provide lift to the tropical LL air mass, producing pulsating storms. In the afternoon, high amounts of precipitation may also be accumulated in Greece, FYROM and S Romania but they cannot verify a level 1 area. Storms should appear in the early morning of Wednesday in S Aegean Sea.
DISCUSSION
.... Ukraine, Hungary and Romania ....
The vorticity lobe is now crossing Poland (15/05 21z), entering the level 1 area the following hours. Storms should appear in the borders with Ukraine and Slovakia even before 06z, under a weakly sheared environment with MLCAPE slightly exceeding 1000 J/kg. A level 1 was issued due to steep mid-level lapse rates, weak mid-level flow and high PW values which can result in slow moving storm cells, producing excessive precipitation and large amounts of small hail. Hail could reach the surface as freezing level is calculated near 2200m and NCAPE values suggest strong up/downdraughts.
.... South Italy ....
The same conditions are expected in S Italy, with slightly better kinematics since local convergence lines can form near the coasts due to sea breeze. The contribution of sea breeze will be higher if diabatic heating will take place in the morning. High PW over the area is expected to produce excessive precipitation and large amounts of small hail in more elevated areas. Weak mid-level wind flow will keep storms almost stationary, increasing the flash-flood threat.
