Convective Outlook: Sat 15 Oct 2016
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sat 15 Oct 2016 - 05:59 UTC Sun 16 Oct 2016

ISSUED 07:16 UTC Sat 15 Oct 2016

ISSUED BY: Dan

Broad upper low will reside to the southwest of the British Isles, but with various forcing elements pivoting around its main centre of gravity to bring renewed pulses of (a messy mix of) dynamic/convective precipitation northeastwards at various stages through Saturday and Saturday night. All of these features have the potential to produce some sporadic/isolated lightning activity, most likely over open waters and on windward coasts where relatively warm SSTs beneath cold mid-levels will increase instability. 

One such feature will arrive across S/SW coastal areas this afternoon, and already has a history of producing some sporadic lightning near the Brest peninsula so far this morning, but is expected to weaken as it moves further inland through Saturday evening. Nonetheless, squally gusts of wind and some small hail will be possible from the most intense embedded cells.

Attention then turns more to the overnight hours as the upper trough advances from the southwest, a sharpening shortwave rounding the base and running north across Ireland/Irish Sea later. An increase in shower coverage/intensity is expected here through Saturday night, and given some marginal instability have issued a low-end SLGT where slightly better environmental conditions look likely to develop to produce lightning. Again, some small hail and gusty winds will be possible with the strongest cells.

Later in the night, another showery feature approaches the south coast from the English Channel. Given slightly better instability and stronger wind shear, this will need monitoring for the potential for a waterspout/tornado. This is considered very low risk in any one location, but similar setups in the past have yielded some tornadic activity, which is climatologically most likely along coastal areas between Gosport and Brighton

In reality, other local-scale SLGTs could be issued, but it is near-impossible to be any more precise as to where the best ingredients could (briefly) come together to increase lightning potential on a local scale.