UK/Ireland 10 Day Outlook, Cool May On The Horizon With -NAO/AO

Written by on April 15, 2013 in United Kingdom & Ireland with 2 Comments

Two deep Atlantic lows will bring two bands of heavy rain accompanied by gale or severe gale-force winds to Northern and Western parts of Britain and across Ireland in quick sucession, tonight and tomorrow night with blustery showers following in between.

Winds will widely top 50+ mph over Scotland, Northern England, Wales and right across Ireland and Northern Ireland tonight and perhaps tomorrow night too with the second system, so worth taking extra care if travelling over the next few days.

Conditions should ease by late week as high pressure builds north from the Azores. There is still uncertainty about how warm it may get this weekend with that high. Going by recent runs of the ECMWF and even the GFS, this weekend doesn’t look quite as warm as previously thought, however, as I study the current setup and link it to the increasingly positive NAO, I believe I am still on the right track with my ideas for the next week to 10 days. Bare in mind, my theory of a warm weekend just gone stemmed back well over a week ago and I got my 22C, despite the BBC only shooting for 19C even as late as yesterday morning. As for the upcoming weekend, which looks to bring high pressure (though perhaps not as warm as first thought), coincides beautifully with my ideas stemming back the best part of two weeks with modelling back and forth but the NAO going positive has kept me stubborn.

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Here’s the upcoming weekend according to the GFS 500 mb chart.

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

Sorry this chart is not particularly clear but it shows a modest ridge but heights aren’t particularly strong and so 850 temps are cool, if not chilly, therefore surface temps too should be dissapointing.

Here’s the 120 hour ECMWF.

Geopotential3250032hPa32and32Temperature32at3285032hPa_Europe_120Both models match up well.. high pressure yes, but not nearly as warm as initially thought.

Does this mean, no warmth on the horizon before the anticipated end of the month cooldown which takes us into May? Not nesessarily!

Here’s the latest NAO ensemble

nao_sprd2
We’re at Apr 15th and notice the peak doesn’t come till nearer the 20th, perhaps even a little later. Though this weekend is cooler but with high pressure at least, I am wondering whether my ‘warm spell’ idea is not dead and buried but perhaps a little premature. I believe the NAO ‘peak’ of positive not only provides us with high pressure over the UK but a surge of warmth to accompany and so, we should keep an eye on next week with even the ECMWF suggesting strong heights and warmer 850s trying to push into the UK and Ireland mid to late next week, coinciding with the spike in the NAO.

The NAO is set to go back negative along with the AO but I strongly believe another warm spell comes beforehand and as of tonight, when analysing the pattern, models with NAO/AO indexes, the short window of the 23-25th next wek is worth watching. Beyond that and towards the closing days of the month, the NAO should drop again, presenting us with a cooler regime which takes us through the first half of May.

Check out the GFS and ECMWF between 23-25th.

GFS 500mb at 216 hrs

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

GFS 850mb at 216 hrs

Courtesy/Owned by AccuWeather Pro

Courtesy/Owned by AccuWeather Pro

ECMWF 500mb/850s

192 hrs

Geopotential3250032hPa32and32Temperature32at3285032hPa_Europe_192

216 hrs

Geopotential3250032hPa32and32Temperature32at3285032hPa_Europe_216

Here’s another look at the CFSv2 for May.

Still below normal but not quite as much as the previous run.

Here’s the old May run…

euT2mMonInd1

New May run…

euT2mMonInd1

Precipitation continues to look below normal through the month.

While this long range model shows near average to slightly below average temps and even with a negative NAO/AO to start, this doesn’t mean we won’t get spells of warmth. The NAO/AO likely won’t stay negative throughout and so when you see a below normal month, this doesn’t mean there isn’t spells of warmer than normal, it’s just the month overall averages out below normal.

Out of interest, how’s June and even July looking??

June.

euT2mMonInd2

June! Still normal or below, hum..

July?

euT2mMonInd3

Interesting!!
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  1. Simon says:

    Hi Mark, out of curiosity what are the drivers for the NAO and AO? Do you have any links to good reference sources? The Met O and Beeb rarely if ever mention the NAO and AO and keep banging on about the jet stream – does the jet stream affect them?

    Thanks, and keep up the sterling work!

    • Mark Vogan says:

      Will try to get back to you with a more solid answer to a good question. In my opinion, the NAO/AO can be influenced by such things as the solar activity and as you’ll notice from my forecasts, sea surface temps. An exact trigger? A little hard to pinpoint. Stratospheric warming/cooling events which I can only put down to solar, is the likely trigger. So, strat warm/cooling events which therefore shift the NAO/AO.

      As for the jet stream, well it’s more influenced by them, rather than them influenced by the jet. Will try to look further and get back to you, Simon.

      Cheers.

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