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: 27/08/2020 06 UTC – 28/08/2020 06 UTC
Issued by: Severe Weather Europe
Forecaster: Marko Korošec
SUMMARY
Severe storms are possible along with both frontal systems over western Europe and also far eastern Europe into western Russia on Thursday. Severe winds and tornadoes are possible across the English Channel. Isolated severe storms are possible across northeast Spain and the western Alps.
Overview of the risk areas across Europe
SYNOPTIC OVERVIEW
An upper ridge is established across the southern half of Europe, with two upper short-waves traveling across eastern and western Europe. A new upper ridge begins strengthening over far North Atlantic and Greenland, resulting in a deepening trough over western Europe. A surface low with frontal system moves from Ireland and UK into Benelux.
FORECAST DISCUSSION
+++ England, English Channel and France +++
SLGT risk has been issued for far southern England and across the English Channel into far northern France with a threat for severe winds and tornadoes.
Some isolated severe storms will be possible within the strongly sheared and helical environment near the warm front. Storms that can form along the warm front and close to the triple point could become supercellular with tornado threats.
+++ Turkey, Finland and northwest Russia +++
SLGT risk has been issued for southeastern Belarus, northern Ukraine into western Russia with an isolated threat for severe storms, capable of producing severe winds, marginal hail, and torrential rainfall.
Storms will form along with the frontal system during the afternoon and gradually vanish in the evening hours.
+++ other areas +++
MRGL risk has been issued for southern Turkey with an isolated threat for severe storms with large hail and severe winds.
TSTM risks have been issued for east-northeast Spain, western Alps, eastern Turkey into Georgia, and part of Morocco 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.)