Severe weather outlook – forecast across Europe. This forecast features areas of organized severe weather with risk levels and severe weather threats across the European continent.
SEVERE WEATHER OUTLOOK – DAY 1
Valid: 10/08/2020 06 UTC – 11/08/2020 06 UTC
Issued by: Severe Weather Europe
Forecaster: Marko Korošec
SUMMARY
Severe storms with a threat for large hail, severe winds, and torrential rainfall are possible across England, France, Germany, Spain, and Georgia on Monday.
Overview of the risk areas across Europe
SYNOPTIC OVERVIEW
An extensive upper-level ridge is centered over northern and western Europe. To its southwest, an upper low is moving towards the Iberian peninsula. A weak upper low with a surface frontal system moves across northwestern Russia.
FORECAST DISCUSSION
+++ England and Benelux +++
SLGT risk has been issued for central England across the English Channel into Benelux with a threat for severe storms, capable of producing severe winds and marginally large hail.
Moderate instability builds up again and overlaps with weak to moderate deep-layer shear. A few isolated storms, including supercells, seem possible to form from the afternoon into the evening hours. Those could result in a few large hail and severe wind events.
+++ Spain and southeast France +++
SLGT risk has been issued for east-northeast Spain and southeast France with threat for severe storms, capable of producing severe winds, large hail, and torrential rainfall.
With an approaching upper low, air mass destabilizes in the afternoon hours, with moderate to strongly unstable air mass present over the forecast areas. The wind shear also increases and should support organized storms, including supercells. Storms could continue into the evening hours.
+++ Germany, Czechia and Poland +++
SLGT risk has been issued for northeast Germany across northern Czechia into southwestern Poland with a threat for scattered severe storms, capable of producing severe winds, torrential rainfall with flash floods and large hail.
A moderately strong instability under weak shear should support some organized slow-moving severe storms with strong winds, flash floods and some large hail events.
+++ Turkey and Georgia +++
SLGT risk has been issued for eastern Turkey into Georgia with a threat for a few isolated severe storms, capable of producing severe winds and large hail.
Although the main instability and shear seem decoupled, conditions should still support organized storms in the afternoon. A few isolated storms, including supercells, are possible with large hail and severe wind threats.
+++ other areas +++
TSTM risk areas have been placed across Morocco, Italy, eastern Europe, south Sweden, the Balkans, and western Turkey with a threat for daytime driven storms. Limited shear is present, so the storms should remain sub-severe.
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Understanding Severe Weather Outlook
Severe Weather Outlook features areas of organized severe weather with risk levels and severe weather threats. Risk levels are divided into seven categories:
TSTM – Thunderstorms
MRGL – Marginal risk
SLGT – Slight risk
ENH – Enhanced risk
MDT – Moderate risk
HIGH – High risk
SIG – Significant risk
WNTR – Winter risk
Risk categories stand for the coverage and intensity of organized severe weather. Those could include supercells, squall lines, mesoscale convective systems, wind storms, flooding, snowstorms, or ice storms.
Severe weather threats include:
- large hail (of at least 2 cm in diameter)
- Tornadoes (including waterspouts)
- Wind gusts (convective or non-convective) above 25 m/s (or above 90 km/h)
- Torrential convective precipitation / Flash floods
- Excessive rainfall (100 mm within 12 hours) / snowfall (50 cm within 12 hours)
Extremely severe weather threats include:
- Large hail (of at least 5 cm in diameter)
- Tornadoes of F2 intensity or stronger
- Wind gusts (convective or non-convective) above 33 m/s (or above 119 km/h) or 12 Bft
- Torrential convective precipitation / Flash floods
- Excessive rainfall (150 mm within 12 hours or above ) / snowfall (above 100 cm within 24 hours)
Categories in the forecast represent the chance of severe weather occurring within a 40 km radius from a location. The used level is based on the conversion table of probabilistic risk into the outlook categories. A threat level is upgraded into a higher category if probabilities meet the threshold criteria for the specific threat (e.g. tornado, wind, hail, or rainfall threat).
Each individual threat area includes a detailed forecast map and discussion on the potential of severe weather threats.
Read more: Explanations for abbreviations (TSTM, SLGT, ENH, etc.)