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Ex-Hurricane Kate

Early this week attention focused on the first storm named by the Met Office and Met Eirann. “Abigail” was a typical winter Atlantic storm, one of many which would be expected to impact on the British Isles each year. The reason for naming storms is explained:

[su_quote]As the UK and Ireland’s National Met Services, the Met Office and Met Éireann operate to maintain public safety through severe weather warnings and forecasts. Working together, it is hoped that naming storms will help raise awareness of severe weather and ensure greater safety of the public. The Met Office and Met Éireann will continue to issue weather warnings in the normal way using the Met Office National Severe Weather Warning Service and Met Éireann Weather Warnings. A storm will then be named when it is deemed to have the potential to cause substantial impacts in the UK and/or Ireland. To avoid any confusion over naming, if a storm is the remnants of a tropical storm or hurricane that has moved across the Atlantic, the already established method of referring to it as, e.g. ‘Ex-hurricane X’ will continue.[/su_quote]

Abigail brought strong winds and some disruption to Scotland and parts of Ireland, along with heavy rain. Here, in southern England, it was nothing unusual for November: breezy and wet.

ex-Hurricane KateRight now, Weather across the British Isles is coming from a large, complex system of low pressure, another Atlantic storm, but this one has the remains of a Hurricane mixed up in it. Kate formed at the beginning of the month off the Bahamas and reached Hurricane strength just before it became part of an Atlantic storm system that had already left the north American continent heading westwards. This happens several times a year and the main effect is to add a great deal of energy and moisture to the storm as the hurricane adds enormous amounts of tropical air to what is already a clash between air from the polar region and air from the tropics.

This system has brought huge amounts of rain to the north and West of the country, especially Wales. This rain has been heaviest where the air has been forced up by terrain (“orographic” rainfall) and has been heavy enough to cause significant flooding. Again, here in the south of England, things have not been too unusual. We had light but very persistent rain for many hours yesterday, giving a total of about 10mm. It is also rather mild for the time of year as we experience a warm, wet tropical airmass. Today it is breezy, but nothing extreme.

As the system rolls through into Europe, it looks as if cooler polar air will be pulled down across the British Isles behind it, with temperatures likely to fall to seasonal norms, for the first time this autumn. November so far has been about 5C above the long term average for this location.