Storm Forecast
Valid: Sun 27 Jun 2010 06:00 to Mon 28 Jun 2010 06:00 UTC
Issued: Sun 27 Jun 2010 05:24
Forecaster: SCHLENCZEK
A level 1 was issued for N Algeria mainly for severe wind gusts (dust storms) and large hail.
A level 1 was issued for S / SE Ukraine mainly for large hail and excessive precipitation.
A level 1 was issued for W Russia mainly for severe wind gusts and tornadoes.
SYNOPSIS
An upper ridge is centered over France and will stretch northward towards the S Baltics. Very warm air from S Spain is advected to the northeast into S France and SW Germany. Between the ridge and an upper trough over the British Isles, a strong southwesterly upper flow will establish. Some instability is forecast in the transition zone between the ridge and the trough over Iberia and France in an environment with marginal shear.
Another plume of unstable air overspreads the Ionian / Aegean Sea and parts of Greece and Turkey near the centre of an upper cut-off low. This low will move eastward during the period, affecting Turkey and parts of the eastern Mediterranean.
A strong frontal boundary is present over W Russia, separating hot and moist air in the eastern parts from cool air in the western parts. This region should be the focus for severe convective storms on Sunday.
DISCUSSION
...Iberia and France...
Recent GFS runs show up to 1000 J/kg MLCAPE in this region with only weak vertical shear and rising geopotential heights. Some diurnally driven showers and thunderstorms will develop and may locally pose a risk of large hail and isolated flash floods. Given the isolated nature of such an event, no threat level was issued.
Similar conditions are expected in N Italy during the afternoon hours. 0-6 km shear has decreased to values below 10 m/s which indicates that organised severe thunderstorms are unlikely.
...N Algeria / Tunisia...
Some hundred J/kg CAPE are forecast in a very warm and dry airmass in the vicinity of a westerly 30 m/s jet streak over central Algeria. Locally 15 - 20 m/s deep layer shear should be sufficient for some organised thunderstorms which may produce large hail and severe wind gusts as Delta Theta-E should be in order of 12 - 16 K.
...parts of SE Europe...
Only some hundred J/kg CAPE are expected in the vicinity of the upper cut-off low in a moderately warm airmass. Overall vertical shear is quite weak and most storms tend to be short -lived and sub-severe. A small part of E Ukraine is highlighted as predicted precipitation sums indicate a possible flash flood event there and locally enhanced shear (10 - 15 m/s) and SRH may lead to an isolated large hail event.
...W Russia...
Along the frontal boundary, some hundred J/kg CAPE are in place with 20 - 25 m/s 0-3 km shear and 150 mē/sē SRH3 ahead of an upper vort-max. Forcing should be sufficient for convective initiation and the development of a linear MCS should be likely. The primary threat of this system should be severe wind gusts. Over the northern parts of this level 1 area, LL shear in order of 10 - 15 m/s is forecast which may allow an isolated tornado.
