Convective Outlook: Wed 26 Jun 2019
What do these risk levels mean?
Convective Outlook

VALID 06:00 UTC Wed 26 Jun 2019 - 05:59 UTC Thu 27 Jun 2019

ISSUED 18:23 UTC Wed 26 Jun 2019


UPDATE 18:22 UTC Latest data suggests the risk of elevated thunderstorms affecting parts of SW Ireland later tonight has increased - as such a SLGT has been introduced. First wave of thunderstorms currently ongoing over the Celtic Sea is expected to pass to the south and/or weaken on approach, but the main interest is with a second round of elevated thunderstorms that will likely develop later this evening - perhaps also close to the Scilly Isles - and will then head northwest towards Munster later in the night. Though it must be stressed the majority of activity will likely stay just offshore to the south

Upper ridge will expand across western Europe on Wednesday, while an upper vortex pivots westwards to the west of Biscay. The net result is advection of a high Theta-W airmass from France, across the Channel Islands and out to the Celtic Sea. Weak impulses running northwards from the English Channel into southern England may produce some showery bursts of rain from high-based elevated convection during Wednesday daytime. Lightning risk is considered quite low.

By late afternoon into the evening, an environment with very steep lapse rates and significant CAPE (1,500 - 2,000 J/kg) will evolve across the Celtic Sea, engaging with the left exit of a strong southerly jet to the west of Biscay. Model guidance is in reasonable agreement for a cluster of potentially very active elevated thunderstorms to develop during this timeframe, expanding in coverage as they drift west-northwestwards on the leading edge of this instability plume over open waters to the south of Ireland. Depending on the exact track, these may pass close to SW Ireland on Wednesday night - and upgrades may be required if trends suggest a heightened chance of reaching SW Ireland, especially late in the night.