2023 Jersey tornado

Just before midnight on Wednesday, November 1st 2023, a violent and unexpected tornado impacted the Isle of Jersey in the Channel Islands, a crown dependency of the United Kingdom. Associated with powerful extratropical cyclone Storm Ciaran, the tornado was subsequently rated T6 on the TORRO scale or IF3 on the International Fujita Scale, which is broadly analogous to the Enhanced Fujita Scale commonly used in the United States, making it the strongest tornado to hit the British Isles for over 70 years.

Meteorological synopsis

The tornado was associated with a broader storm system, Storm Ciaran, an extremely powerful extratropical cyclone named by the UK's Met Office on the October 29th 2023. Red weather warnings for non-tornadic wind gusts in excess of 100mph were already in force for the Channel Islands with schools closed and people told to stay at home. By 18:00GMT on the evening of the 1st of November, the leading edge of the storms precipitation in the form of a warm front had reached Jersey, bringing mainly heavy rain produced by nimbostratus clouds.

At around 22:00GMT a cluster of showers formed over western Brittany in response to the storms rapidly advancing cold front, which then intensified into a cluster of thunderstorms. The cluster was quickly advected northeast back into the storms warm sector by the extremely strong south-westerly winds where it evolved into a persistent and severe single-cell thunderstorm known as a supercell. This cell left the northern coast of France near Saint-Brieuc, and reanalysis of detected lightning strikes produced by the cell shows that at least three cloud to ground strikes with a positive charge and a current exceeding 100kA affected mainland France and the English Channel as the storm tracked northeast towards Jersey.

Thunder and lightning was initially reported in St Helier by 23:40GMT, and by 23:50GMT, very large hail up to 85mm (8.5cm) in diameter was reported in the northern and Western suburbs of St Helier as well as scattered reports having been received in the more rural north-eastern parishes, which is comparable to some of the largest hail ever recorded in the British Isles since at least 1950. At around 23:55GMT, the tornado touched down just to the east of Havre des Pas bathing pool, on the islands south-south-eastern coastline, inflicting moderate to severe damage to coastal and seafront properties.

A classic hook-echo was present on the islands Doppler radar that indicated tornadic rotation to the east of the forward-flank downdraft.

Tornadic damage

The tornado then continued to travel north-northeast inflicting severe damage to Florence Boot Playing Fields (commonly referred to by locals as simply "FB Fields"), where metal fence posts were bent and deformed with other metal structures being torn and twisted. A metal recycling bank was rolled into a car before being tossed into the road 40m from where it originally stood. This damage was rated T4 and T5 respectively. A resident of nearby houses described lying in bed when the window shattered and tornadic debris started to fly in, causing an interior wall to blow down entirely.