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: 08/08/2020 06 UTC – 09/08/2020 06 UTC
Issued by: Severe Weather Europe
Forecaster: Marko Korošec
SUMMARY
Mainly isolated severe storms with a threat for severe winds, large hail, and torrential rainfall are possible across the southern Balkan peninsula, northern Spain, and western Scandinavia on Saturday.
Overview of the risk areas across Europe
SYNOPTIC OVERVIEW
An upper-level ridge dominates much of Europe, while a weakening upper low is drifting east over Greece. A short wave trough moves across Norway. At the surface, high-pressure extends across most of continental Europe. A cold front is placed from Norway towards England.
FORECAST DISCUSSION
+++ Bosnia, Serbia, Romania, Bulgaria and Greece +++
SLGT risk has been issued for eastern Bosnia, central Serbia into southwestern Romania and Bulgaria with an isolated threat for severe storms, capable of producing severe winds, large hail, and torrential rainfall.
MRGL risk has been issued for areas surrounding the SLGT risk area across much of south-central Balkans, including the Ionian Sea, and southern Italy with a limited threat for some strong winds, marginal hail, and heavy rainfall.
A moderately unstable air mass remains across the southern Balkan peninsula, beneath a weakening upper-level low. With marginal deep-layer shear in place, some better-organized storms are again possible in some areas.
Severe winds and locally torrential rainfall with flash floods are possible. Higher instability should also support some large hail events. Additional storms are also likely across southern Italy, the Ionian sea and around Greece, beneath the still cold upper low core. Cold mid-levels should support the waterspout threat again.
+++ Spain +++
SLGT/MRGL risks have been issued for north-central Spain with a threat for a few isolated severe storms, capable of producing severe winds and large hail.
A moderate instability under weak winds and shear could support some organized daytime driven storms wind strong winds and some large hail events.
+++ Norway, Sweden +++
SLGT risk has been issued for south-central Norway into western Sweden with a threat for isolated severe storms, capable of producing severe winds and marginally large hail.
Marginal instability builds up along the moving cold front within a moderately sheared environment. A few isolated organized storms could bring severe winds and some large hail events.
+++ other areas +++
TSTM risk areas have been placed across England and western France, the Alps, Slovakia, Poland, western Turkey, and southwestern Russia. Some daytime driven storms are likely to occur but 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.)