Storm Forecast
Valid: Sat 22 Aug 2015 06:00 to Sun 23 Aug 2015 06:00 UTC
Issued: Fri 21 Aug 2015 20:30
Forecaster: DAFIS
A level 2 was issued for NE Spain and SW France mainly for excessive rain, large hail and severe wind gusts.
A level 1 stretches from the UK and E Ireland to Spain, mainly for excessive rain, large hail, severe wind gusts and tornadoes.
A level 1 was issued for Greece, Albania, FYROM, S Bulgaria and NW Turkey mainly for excessive rain, large hail and tornadoes.
SYNOPSIS
A cold pool in Eastern parts of Europe with slow movement to the West and another shortwave trough South from it, are the main causes of convective phenomena in the Balkans that will continue until Sunday. Another amplifying trough arrives from the Atlantic Sea to the most Western parts of the continent with a wide jet streak extending from North Spain to NE of the UK.
At the surface, a low pressure system is situated just South from Iceland. A cold front stretches from the UK to the western parts of the Iberian Peninsula and a warm front crosses the UK during the night of Saturday, where severe weather is forecast.
DISCUSSION
.... NE Spain and SW France ....
A jet streak with speeds of about 35 m/s and weak low level flow result in strong DLS of about 20 - 25 m/s which overlaps with MLCAPE of 1500 - 2000 J/kg. Some storms that formed during Friday night, will continue to affect parts of Spain but the main risk emerges during the second half of Saturday, when the cold front crosses the area. The boundary layer, rich with moisture from the sea and diurnal steepening lapse rates will result into explosive CI during the afternoon and large hail is expected. Moreover, excessive rain is forecast due to large amounts of PW according to WRF runs, with almost 50 mm over the level 2 area.
.... Spain to the UK ....
Several storms are forecast to form at the level 1 area, where synoptic-scale lift and weak CIN will lead in widespread showers. In SW France and the UK, organized storms at early night hours are forecast with large hail and severe wind gusts being the main threats. DLS of more than 15 m/s overlapping with some hundreds of CAPE and SREH 0-3km exceeding 300mē/sē are indicators that any storm that is formed into this area will become severe. LLS and SREH 0-1 km show favorable conditions for tornadoes or waterspouts near the coasts of Spain and France. There is also tornado threat for the UK during night hours.
.... Greece, Albania, FYROM, S Bulgaria and NW Turkey ....
A shortwave trough affects this part of Europe during Saturday. One or two multicells or supercells are forecast to form early in the morning in the NW Aegean Sea and in the N Ionian Sea, producing excessive rainfall and tornadoes (waterspouts). A convergence zone in eastern parts of Greek mainland, due to strong NE low level flow and W middle and upper air flow and advection of LL marine moisture, result in high MLCAPE values (~ 1000 J/kg) and DLS of about 20 m/s with signals of up to 25 m/s, without CIN, at least during night and early morning hours.
Same conditions will be present in northern parts of Turkey with storms being advected from the S Black Sea (waterspouts are also not ruled out). Later during Saturday, diurnal heating will result in widespread showers in mainland of Turkey and Greece, but also in Albania, FYROM and S Bulgaria where MLCAPE overlaps with DLS of about 15 - 20 m/s, so large hail is forecast and some severe wind gust reports are not ruled out.
