UPPER LEVEL LOW - WEATHER EVENTS

• The frontal cloud band on the leading edge of an Upper Level Low is usually thick enough to produce precipitation. In some cases there is also frontal cloudiness on the rear edge.
• When the Upper Level Low is over land, there is a low cloud layer in the centre.
• Over cold surface there is no convection, and therefore no showers occur.

Over Sea

Parameter	Description
Precipitation	Moderate to heavy showery precipitation. In winter season snow and snow showers are possible Also hail and thunderstorms can be observed. In centre convective cells (showers) are seen
Temperature	No significant feature at surface. Quite often a thermal trough in upper levels
Wind (incl. gusts)	Around embedded Cbs strong gusts are possible
Other relevant information	Precipitation in cloud band showery (layered cloudiness with embedded Cbs) Risk of moderate to severe icing and turbulence.

An Upper Level Low over the British Isles:

	09 May 2001/00.00 UTC - Meteosat IR image, weather events (green: rain and showers, cyan: snow, yellow: fog and mist, black: no precipitation)

Over Land

Parameter	Description
Precipitation	Moderate to heavy showery precipitation. In winter season snow and snow showers are possible Also hail and thunderstorms can be observed. In centre overcast of low layered cloudiness with rain, drizzle or snow.
Temperature	No significant feature at surface. Quite often a thermal trough in upper levels
Wind (incl. gusts)	Around embedded Cbs strong gusts are possible
Other relevant information	Precipitation in cloud band showery (layered cloudiness with embedded Cbs) In centre sometimes embedded Cbs with showers Risk of moderate to severe icing and turbulence.

A large Upper Level Low with several secondary lows over Eastern Europe:

	18 May 2001/00.00 UTC - Meteosat IR image, weather events (green: rain and showers, cyan: snow, yellow: fog and mist, black: no precipitation)