Convective Outlook Issued: Moderate risk 07/06/2025 06:00 - 08/06/2025 05:59

A cold pool associated with an upper low pressure will gradually move east throughout Saturday. A few shortwaves associated with the low pressure will deliver bands of heavy showers across most of the country, some might be thundery and severe.

Deep westerly jet stream has intensified the upper low during early Saturday, allowing a tight temperature and pressure gradient across the southern quadrant of the system. Deep level shear of 40-50 knots widely across England and low level shear of 25-35 knots along the south coasts provided a suitable environment for long tracking thunderstorms to form, especially along the south coasts due to a surface convergence zone. Surfacing heating will also allow CAPE of 500-700 J/kg to develop in the south.

Skinny, weak CAPE and well-sheared environments are prone to produce frequent lightning and rather severe storms. A good example last year (28/03/2024) produced cells with supercellular characteristics, bringing widespread thunderstorms and hail.

^ Convective Outlook Verification for 28/03/2024

A similar picture is expected today, where thunderstorms are expected to be triggered by a shortwave, initiating across Cornwall around 11 am - 12 pm. Once the storms initiated across Cornwall, a low level convergence zone as well as strong background shearing will allow this cell to be long tracking, perhaps lasting through most of the afternoon, moving along the southern coasts into Kent. A few brief tornadoes are possible, especially if thunderstorms contain supercellular characteristic. Hail, up to 2 cm in diameter is also possible due to the support of steep lapse rate. Strong gusts of 55mph max is also possible, especially along the south coasts. A very low-end moderate risk has therefore been issued.

As the atmosphere turn increasingly less saturated during the afternoon, further more showers could develop along some local convergence zones, mainly across parts of central southern England and East Anglia. These thunderstorms are expected to be rather spoardic as first due to the lower EL height, but they could turn more organised as they move eastward into a more well sheared environment, perhaps turning severe as well during the late afternoon and into the evening.

Isolated/ Scattered thunderstorms are also possible across parts of Scotland as well.

You can download the kml file of the convective outlook here:

Download here