Issued 2018-11-23 08:23:19 Valid: 23/11/2018 0600 to 24/11/2018 0600
THUNDERSTORM OUTLOOK - FRIDAY 23 NOVEMBER 2018
Upper low over the NE Atlantic will drift ESE to SW of the UK and Ireland today, shallow surface low will drift slowly towards SW UK, with a slow-moving occluded front lying NW-SE across southern Ireland-SW England-northern France during the forecast period. Pulses of heavy showers and a few thunderstorms will drift NW along/near frontal boundary today.
... S IRELAND, SW ENGLAND, SW WALES ...
Tongue of mild/moist air advecting NW along/near occluded frontal boundary across SW UK. Filaments of stronger vorticity aloft wrapping around upper low to the SW will create lift of this warm/moist conveyor into increasingly cold air aloft - which create a NW-SE zone of instability/CAPE sufficiently strong to support scattered thunderstorms moving N/NW across the above areas through the day. Already sferics detected at breakfast time off south Devon coast. Heavy showers and thunderstorms will be capable of producing locally intense downpours, producing localised flash-flooding and hazardous driving conditions, especially as the showers/storms will form bands and train over some places. Small hail is possiible with these showers/storms.
Issued by the Netweather forecast team whenever there is a risk of storms or severe convective weather, these discussion based and in depth forecasts will highlight the areas at risk and give an in depth description of the risk and the factors surrounding it.
Thunderstorms - Severe thunderstorms unlikely to occur, slight risk of hail, gusting winds and localised flooding.
Slight Risk - A slight risk of severe convective weather exists. Hail >2.0cm diameter, wind gusts exceeding 50mph or 5-10% risk of a tornado within 50 miles of a point, or > 30% risk of localised flooding.
Moderate Risk - A moderate risk of severe convective weather exists. Hail 4-5cm in diameter, or wind gusts of 60-70mph, or a 10-15% chance of a tornado within 50 miles of a point, or >50% risk of localised flooding.
High Risk - A high risk of severe convective weather exists. Rarely, if ever used on the UK. Hail >5cm, or wind gusts in excess of 80mph, or >20% risk of a tornado within 50 miles of a point, or >70% risk of localised flooding.