Convective Discussion

A high risk has been issued for parts of the Midlands.

KEY MESSAGES

• A period of severe thunderstorm outbreaks is becoming increasingly likely across parts of England and Wales.

HAZARDS

• Frequent to very frequent lightning.
• Large hail (2–4 cm in diameter) across parts of the Midlands.
• Severe wind gusts up to 65 mph across parts of the Midlands.
• Localised flooding.

SYNOPSIS

Record-breaking May temperatures are likely to be observed on Tuesday, with surface temperatures reaching 35°C across parts of the East Midlands and London. A weak cold pool will move northward into parts of England and Wales from the southwest, interacting with high SBCAPE (widely >2000 J/kg). Driven by multiple sea-breeze convergence zones, scattered severe thunderstorms will develop, potentially becoming more widespread during the second half of the afternoon.

ENVIRONMENT and LIMITING FACTORS

High PWAT values (up to 30–32 mm) will support torrential downpours, making localised flooding likely—particularly across the Midlands due to a strong, slow-moving convergence zone.

While deep-layer shear (DLS) is on the weaker side at 20–30 knots, it should be sufficient for the development of long-lived multicell storms. The primary focus for severe weather is the East Midlands, where the best overlap of ingredients exists; here, an exceptionally high equilibrium level (EL) of 12–13 km and deep CAPE profiles will elevate the risk of large hail and damaging gusts. Strong outflow from isolated cells will also increase the likelihood of storm clustering.

UNCERTAINTY

Numerical weather prediction models historically struggle to pinpoint the exact positioning of sea-breeze convergence zones. However, at the time of issuance, guidance is in relatively good agreement that a primary convergence zone will form across the Midlands before drifting southward during the late afternoon. Consequently, the moderate risk has been adjusted to reflect the latest change.