Storm Forecast
Valid: Mon 01 Aug 2011 06:00 to Tue 02 Aug 2011 06:00 UTC
Issued: Sun 31 Jul 2011 22:06
Forecaster: SCHLENCZEK
A level 2 was issued for parts of E Spain and N Morocco / NW Algeria mainly for large to very large hail and severe wind gusts and to a lesser extent for tornadoes.
A level 1 surrounds the level 2 for large hail and severe wind gusts.
A level 1 was issued for E Poland, Belarus and NW Ukraine for large hail.
A level 1 was issued for E Greece and FYR Macedonia for large hail.
A level 1 was issued for N / NE Turkey for large hail.
SYNOPSIS
The most remarkable upper level feature on Monday is a small upper shortwave trough west of Iberia which will move across Iberia towards France. Unstable air ahead of this trough will lead to severe thunderstorms over Spain and the N Maghreb States.
Warm and moist air remains over eastern Europe and leads to showers and thunderstorms over a broad area. Locally, up to 2 kJ/kg MLCAPE are forecast and some isolated large hail is possible.
Ahead of an approaching low pressure system, some instability is expected over the British Isles and also over S Scandinavia.
Remnants of an upper low which moved across E Ukraine will lead to an overlap of low instability and strong shear over Turkey which is likely to result in some large hail reports.
DISCUSSION
...Iberia and N Morocco / NW Algeria...
Strong WAA affects the eastern portions of Spain as well as the N Maghreb States during Monday morning. This will lead to an increase of CAPE to approx. 1 - 2 kJ/kg in some places. Strong 20 - 25 m/s deep layer shear overlap with the highest instability and only a small CIN barrier should counteract convective initiation as strong QG forcing is to expect from the approaching shortwave trough. Some low and mid level cloudiness could locally reduce instability but some storms will probably develop during the afternoon. Given high instability and strong shear as well as 200 - 400 mē/sē of SRH3, well-organised multicells and supercells should be the dominant convective mode. The main threat will be large to very large hail, severe wind gusts and isolated tornadoes due to locally enhanced LL shear.
...British Isles...
Showers and thunderstorms may develop during the afternoon in an environment with low-end instability and weak shear. Severe weather is not expected to occur.
...Scandinavia...
Similar to the situation over the British Isles, low instability and weak shear are forecast for most portions of S Scandinavia. One exception is a region with 15 - 20 m/s deep layer shear over central Sweden. Next to this small jet streak, instability seems to be too low to support severe weather. Most of the storms will rapidly diminish after sunset.
...Italy, Adriatic, Balkans...
Some 500 - 1000 MJ/mē of ICAPE are forecast over most portions of Italy, the Adriatic and the Balkans. Deep layer shear has decreased to about 5 - 10 m/s which is probably too low to support organised severe thunderstorms. One can't rule out an isolated funnel / brief tornado and an isolated large hail event, but overall threat is very marginal.
Towards Greece, deep layer shear is somewhat higher and GFS predicts a small local maximum of instability. This may allow some more organised storms which are capable of producing isolated large hail. The region with the highest probability of organised convection is covered by a small level 1 area.
...E Poland, Belarus, S Baltics, NW Ukraine, W Russia...
The warm airmass with moderate instability and weak vertical shear also remains over parts of eastern Europe on Monday. Most storms tend to become multicells or pulsating singlecells with isolated large hail and isolated severe wind gusts as main threat. Locally, some flooding due to slow storm motion and backbuilding of storms may occur. Peak activity is expected around noon / early afternoon.
...Turkey...
Some hundred J/kg CAPE and 20 - 25 m/s of deep layer shear over the northern parts of Turkey should allow some multicells and supercells with isolated large hail as main threat. A level 1 is issued for the region which is most likely to be affected. The hail threat continues to the eastern / northeastern parts of Turkey which lay outside of the forecast area.
