Thunderstorm Risk

Conditions for deep, moist convection (DMC):

• Air parcels must have a Level of Free Convection (LFC) 
• The synoptic-scale helps prime the local environment for deep, moist convection (removing CIN, etc...) 
• There must be sufficient lift so air parcels can reach their LFC (from air-mass boundaries or terrain) 
• Once air parcels reach their LFC, they must become positively buoyant through a relatively deep layer of the troposphere 

Europe Thunderstorm Probability
Thompson Index: Thunderstorm Potential & Severity

< 20: Weak Potential for TS

20 to 30: Moderate Potential for TS

30 to 40: Strong Potential for TS

40 to 50: Very Strong Potential for thunderstorms

> 50: Extreme Potential of thunderstorms

 

>35: Potential for severe TS

Severe TS: Different countries = different criteria

 

United Kingdom:

  • Any force tornado

  • 20 mm (0.79 in) min size hail

  • 89 km/h (55 mph) min wind speed

  • "Conducive to flash flooding" rainfall rate

 

Extremely severe convective weather phenomena:

  • A tornado of class F2 or stronger

  • At least 5.0 cm hail size

  • Wind gusts with a speed of at least 33 m/s (about 119 km/h or 65 knots)

What to look for:

 

- Identify regions where potential for strong updrafts exists (high CAPE)

- Eliminate regions in which there isn't any CAPE (SB, ML or MU).

CAPE (SB, ML, MU) & CIN
Europe Convective Weather Forecasts
France Thunderstorm Risk (including large hail & tornado)