El Nino, Subtropics Fuel UK Rains, Active SW Storm Track Continues, Further Flooding Likely This Week

Written by Mark Vogan on August 25, 2015 in Rest of Europe, Summer 2015, United Kingdom & Ireland with 0 Comments

It’s been an interesting past several days of weather across the UK with storms, heat, humidity as well as flooding rains. Canterbury received 61mm (2.4 inches) of rain within a 12 hour period yesterday. That’s over a months worth! According to Nick Miller of the BBC, most of that fell within 1 hour.

Check out the skies hanging over London yesterday. View from BBC Broadcasting House!

Credit: BBC Weather

Back on Saturday night, we saw flooding rain and dramatic thunderstorms followed by one of Scotland’s warmest as well as windiest days of summer. How often do you get 25C with a gale blowing? Wind speeds over Cairngorm Summit were clocked at an unusual 105 mph.

So why are we seeing the heavier pulses of rain into the UK these days? Firstly, we continue to see a strengthening El Nino event in the Pacific which is the primary reason why I had this as a wet summer. Secondly, the track of these lows are coming in from a warmer source region where waters as you well know have been running 1-3C above normal off Portugal.

Credit: NOAA

Thirdly, the further south than normal jet now and throughout this summer has everything to do with the large SSTA contrast between north-central Atlantic extending into Ireland and the very warm water off Iberia, this has helped enhance the summer jet.

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Lows coming up from the warmer-than-normal subtropics continue more moisture and within a warm, humid environment, you get bigger rains. That along with the El Nino which is enhancing our rainfall not just now but throughout this summer.

This is NOT a normal jet stream position or strength for late August.

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Yesterday saw quite the upside down UK temperature profile with the warmest high in Northern Scotland (23C) and the coolest high (13C) over Southern England beneath the cloud, rain and cool wind.

Credit: BBC

This is a very active pattern to end August with further ‘El Nino/warm Atlantic’ fuelled rains to come through this evening into tomorrow. Atlantic lows continue to circle a large trough out over the Atlantic, their eastward progressed halted by a strong blocking high over Europe.

The low pressure parade will continue through the remainder of this week and with a more southerly track, we see more rain thanks to sub-tropical and warm water influence and a cooler air mass over the UK with the jet being displaced further south than normal.

The QPF 7 day rainfall totals shows clearly where these lows are tracking.

Credit: AccuWeather Pro

The GFS surface shows the domination of low pressure but an easing down into early and mid next week as heights build over the Atlantic, recasting this turbulent atmosphere.