Convective Outlook: Mon 01 May 2023

LOW SLGT MDT HIGH SVR

What do these risk levels mean?

Convective Outlook

VALID 06:00 UTC Mon 01 May 2023 - 05:59 UTC Tue 02 May 2023

ISSUED 07:06 UTC Mon 01 May 2023

ISSUED BY: Dan

A mid/upper trough embedded between two substantial upper ridges will be located over eastern Britain at 06z Monday, exiting to the North Sea by 12z. The associated cold pool aloft in conjunction with surface heating through the day may yield a few hundred J/kg MLCAPE, depending on the extent and clearance/overturning of low cloud/drizzle earlier in the morning. It seems likely towards midday and thereafter a number of showers will develop, some heavy, drifting southeastwards across central, southern and eastern England. Analysis of some forecast soundings from different NWP suites suggest there may be a slight a warm bulge in the 600-700hPa layer, which would serve to limit the depth of convection to below 13,000ft (and therefore lightning potential). The greatest risk of a few isolated lightning strikes, where cloud tops could reach -45C / >25,000ft, will likely be over East Anglia due to greater proximity to the departing upper trough, especially as any cells approach the east coast before moving offshore. As such, a low-end SLGT has been introduced. A strongly northerly jet will overspread central and eventually eastern England through the afternoon on the rear side of the departing trough, but at the same time profiles will likely gradually warm aloft, tending to progressively reduce the depth of convection from west to east. Therefore, despite increasing deep layer shear during the afternoon, much of the strong flow aloft will tend to be above the free convective layer.