Convective Outlook: Sun 30 Jul 2017
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Sun 30 Jul 2017 - 05:59 UTC Mon 31 Jul 2017

ISSUED 19:10 UTC Sat 29 Jul 2017

ISSUED BY: Dan

Once again, upper vortex will be centred to the west of Scotland on Sunday, with cool mid-levels covering the British Isles atop relatively warm SSTs and diurnal heating inland. Reasonably steep lapse rates exist with a build-up of 500-900 Jkg-1 CAPE, while several shortwaves will rotate around the parent upper low. Broadly cyclonic upper flow, although hints of some subtle ridging over SE-ern quarter of Britain and resultant subsidence will translate to late convective development (i.e. late afternoon into the evening) for the likes of Lincs / East Anglia / SE + CS England.


Elsewhere scattered showers and a few thunderstorms will become increasingly widespread as a shortwave trough phases with diurnal heating - for England and Wales, the risk is mainly confined to SW England and Wales during the morning, then slowly expanding NE-wards across the Midlands / Home Counties to eastern England by evening. Fewer showers likely in Kent/Surrey/Sussex given surface flow originating from the Channel - though a few (weakening) French exports may get close to the far SE at times.

Closer to the centre of the upper low, showers/thunderstorms across Eire / Northern Ireland / Scotland will likely be more pulse-type, particularly focused along zones of low-level wind convergence and hence slow storm motion could result in some locally high rainfall totals. A few funnel clouds / weak tornado may be possible with these cells.
For southern Britain, stronger DLS around the base of the upper low may aid some cell organisation, and while showers/thunderstorms will tend to be faster-moving compared to those farther north, elements of training over similar areas may occur, especially when combined with peninsula convergence from SW England - S Midlands - East Anglia, for example. Such convergence combined with some reasonable LLS could potentially result in an isolated tornado - though relatively high cloud bases (given temperature / dewpoint spread) reduce this risk somewhat. Locally strong wind gusts may occur near these showers.

Hail up to 1.5cm in diameter will be possible with any stronger cells.