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: 07/08/2020 06 UTC – 08/08/2020 06 UTC
Issued by: Severe Weather Europe
Forecaster: Marko Korošec
SUMMARY
A few isolated severe storms with a threat for severe winds, marginally large hail, and torrential rainfall are possible across the southern Balkan peninsula, northern Spain and central Poland.
Overview of the risk areas across Europe
SYNOPTIC OVERVIEW
The upper-level ridge continues strengthening across much of Europe with a weakening upper low over the southern Mediterranean and southern Balkans. The North Atlantic trough/low is also weakening while moving across Iceland on Friday. At the surface, high-pressure has established, centered over northeast Europe. A frontal system stalls over Ireland and Scotland.
FORECAST DISCUSSION
+++ Bosnia, Serbia, Romania, Bulgaria, Greece +++
SLGT risk has been issued for eastern Bosnia, central Serbia into southwestern Romania, west-central Bulgaria, and eastern Greece with an isolated threat for severe storms, capable of producing severe winds, marginally large hail, and locally heavy rainfall.
MRGL risk has been issued for areas surrounding the SLGT risk area across much of south-central Balkans, the Ionian Sea, and southern Italy with a limited threat for strong winds, marginal hail, and heavy rainfall.
An unstable air mass remains across the southern Balkan peninsula, beneath a weakening upper low. Still, some marginal deep-layer shear is present, especially across the SLGT risk area.
Some organized storms are again likely to develop and could mainly bring severe winds and heavy rainfall in places. Stronger instability should also support some marginal hail events. More storms are also expected across southern Italy, the far south Adriatic Sea, and the Ionian sea beneath the upper low core. Cold mid-levels should support the waterspout threat again.
+++ Poland and Ukraine +++
MRGL risk has been issued for central Poland into western Ukraine with a threat for isolated severe storms, capable of producing severe winds and marginally large hail.
A quite strong instability but limited shear could support some better organized isolated storms wind strong winds and some larger hail.
+++ north Spain +++
MRGL risk has been issued for northern Spain with a threat for isolated severe storms, capable of producing severe winds and marginally large hail.
Although with limited instability but within the marginal shear, some isolated storms could become severe with strong winds and some larger hail.
+++ other areas +++
TSTM risk areas have been placed across the UK and Ireland towards SW Norway, Morocco, Ukraine and the Alps. 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.)