Convective Outlook: Tue 08 Aug 2017
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Tue 08 Aug 2017 - 05:59 UTC Wed 09 Aug 2017

ISSUED 17:11 UTC Tue 08 Aug 2017


UPDATE 17:11 UTC Frontal boundary moving farther north than earlier expectations has allowed deeper instability to also move farther north, hence SLGT extended into Lincs

UPDATE 08:56 UTC No major changes, SLGT marginally extended to the north Norfolk coast

A very complicated pattern on Tuesday, with an upper vortex sliding SE-wards across Ireland, and in a broad sense pockets of marginal instability across the British Isles. The picture is complicated further by the N-S aligned frontal boundary providing thick cloud and dynamic precipitation to parts of the Midlands and Yorkshire/Lincolnshire, while either side potential exists for deep convection, either beneath the upper vortex in the west, or within the somewhat higher WBPT airmass to the east of the front.

Difficult to pin down any specific area for lightning activity, as there is a fairly broad but low risk in many areas, though some hints in NWP guidance of low-level convergence forcing a line/area of slow-moving torrential downpours in East Anglia during the afternoon and early evening hours. Marginal instability and rather unimpressive lapse rates suggest lightning might be quite isolated or sporadic (probably not worthy of a SLGT), but a very low-end SLGT has been issued to highlight this area a little better - the net result probably some heavy showers with little lightning. This also dependent on sufficient cloud breaks for insolation. Here the main concern is localised flooding. A few funnel clouds or a weak tornado will be possible with this activity.

The deepest convection will likely be found over SW Ireland with closest proximity to upper vortex, though this possibly moving through slightly out of sync with the diurnal cycle perhaps.