Convective Outlook: Mon 14 Oct 2019
LOW
SLGT
MDT
HIGH
SVR
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Mon 14 Oct 2019 - 05:59 UTC Tue 15 Oct 2019

ISSUED 19:11 UTC Sun 13 Oct 2019

ISSUED BY: Dan

Trough disruption will occur on Sunday night to the west of Ireland, with the largescale upper trough splitting such that one portion will relax northeastwards towards NW Scotland (generating some instability over this area on Monday, hence the risk of a few isolated lightning strikes), the other digging southwards towards Biscay while becoming increasingly negatively-tilted. The net result is a backing of the flow over western Europe, encouraging a surge of warm air advection to occur from France into SE England / Low Countries, this environment also becoming engaged by the forward side of the approaching aforementioned upper trough.

The frontal boundary, which has plagued much of England and Wales throughout the weekend, will begin Monday once again straddling the English Channel. Through the day the front, and associated leading precipitation, will lift gradually northwards, with advection of high dewpoint air (15-16C) eventually reaching SE England during the afternoon and evening hours, within the warm sector. Forced ascent of this warm, moist airmass, particularly as a ~950mb warm nose develops by late afternoon / early evening, will encourage deep convection to occur, with heavy showers / a few thunderstorms expected to develop over northern France / English Channel and drift NNE / NE-wards towards CS / SE England, and perhaps later East Anglia.

The true extent of lightning is questionable given rather saturated profiles, but 400-600 J/kg CAPE coupled with steep mid-level lapse rates, strong shear through the cloud-bearing layer and forced ascent should allow at least some sporadic lightning to occur, and hence the introduction of a SLGT. The area may need tweaking (east and / or west) depending on trends.
Despite the somewhat restricted instability, forecast wind profiles would suggest the potential for a supercell or two. Much of this activity will be from elevated convection, however should any thunderstorms become rooted within the boundary layer then there is potential for the marked backed surface winds to aid low-level rotation and bring the risk of a tornado, particularly early in the evening. Local flooding will be an additional concern.