Summary: Storm Nelson will move northward and bring heavy and squally showers, perhaps some clusters of thunderstorms, moving from southwest England, expanding itself northeastward toward majority of Southwestern England over late morning and early afternoon.
Convective Available Potential Energy (CAPE) ranging from 500 to 800 J/kg could energize the showers behind the occluded front, leading to the formation of one or more squall lines propagating northeastward from Devon during the late morning and afternoon. Coastal areas may experience gusts of 60-70 mph, perhaps 70-80 mph locally, with inland areas of England possibly encountering gusts of 50-60 mph. Intense rainfall and small hail are also potential concerns. There is a risk of tornadoes in southwest England and central southern England during the early afternoon as an active squall line will create conditions for rotating updrafts and the development of weak tornadoes.
Research on Synoptic-Scale Environments and Precipitation Morphologies of Tornado Outbreaks from Quasi-Linear Convective Systems in the United Kingdom indicates that tornado outbreaks, defined as days with three or more tornadoes, often occur in convective storms with heavy precipitation over a line exceeding 100 km. This suggests that tornadoes in such a setup are not uncommon. Relatively high CAPE value will also allow some organised cluster of thunderstorms to develop, mainly along the squall line across Devon, Somerset and Dorset.
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