European September/Autumn 2018 Outlook

Written by on August 22, 2018 in Rest of Europe, United Kingdom & Ireland with 0 Comments

From May 1 through July 31, the majority of Europe and in fact the Hemisphere has been unseasonably warm, record breaking warm. This can be directly attributed to the pre-Super El Nino ocean warming and post El Nino heat release into the atmosphere. Another key factor I believe was in fact the cooling of the Atlantic which aided in the dry spring and enhancement of blocking high pressure.

Take a look at how warm the oceans were back around this time in 2015 as the Super El Nino was brewing.

Summer 2018 compared to the hottest/driest on record…

Article from the Met Office

It’s been a long hot summer for many in the UK this year, but where does 2018 stand in comparison to previous record summers?

It already looks certain this summer – June, July and August – is going to be one of the warmest on record for the UK, after prolonged periods of hot weather. The latest mid-month statistics for August suggest the race for the very top spot in terms of temperature is still wide open.

After the third-warmest June and second-warmest July in our official national records dating back to 1910, this year is currently vying with the current record holder, 2006, as the warmest summer for mean temperature (which includes both day and night temperatures). The mean temperature for 2018 is currently at 16.1 °C – that’s exactly the same at this point in August of the record-holding summer of 2006. The final figure for 2006 was 15.8 °C.

Even if temperatures are around or below average for the rest of meteorological summer (through to the end of August), this year is likely to finish in the top five. As of 15 August 2018, the mean UK temperature for this month is currently 16.3 °C – this compares with a long term average for August of 14.9 °C.

The record mean temperature for August was 17.3 degrees in 1995. Although the mid-month figure is some way short of this – currently August 2018 stands as the eighth-warmest on record – the consistently warm weather throughout June, July and August raises the prospect of more notable ranking of average temperature for the summer as a whole.

Usually we will only quote statistics to the nearest 0.1 °C, but it is worth noting that the top three warmest summers for mean temperature are separated by just 0.01 °C – with 2006 at 15.78 °C, while 2003 and 1976 are tied in joint second at 15.77 °C .

The picture is a bit clearer when looking at average maximum temperature, where 1976 is the record holder with 21.0 °C, which is more comfortably ahead of 1995 in second place with 20.6 °C.

By this measure this year is vying with 1976 for the top spot  – at present the average maximum figure for 2018 stands at 21.1 °C. How the rest of this August pans out will have an effect on the final standings, but 2018 is almost certain to be one of the hottest on this measure as well.

Dr Mark McCarthy, Head of the Met Office National Climate Information Centre, explains: “Looking at maximum temperatures might seem to chime more with our perceptions, as our memories tend to focus on those hot days when the temperatures really peaked, rather than the mild nights.

“However, by including night and daytime temperatures, the mean temperature measure gives a fuller picture of what the UK climate is doing. On this measure it’s clear that the meteorological summer of 2018 is exceptional, simply for the consistent levels of warmth seen throughout the period so far.”

As you can see in the ‘Summer Maximum’ graph, this year is currently warmer than 1976 – but that summer saw a warm spell in August which is likely to bring it back in contention. It remains to be seen whether this August will be cool or warm, so it’s impossible to say which year will end up as the record. But it is reasonably safe to say that this year will be amongst the warmest.

Looking at the first half of August 2018 itself, it’s clear that although temperatures throughout the UK have been warmer than average, it is England that has seen the most pronounced effects – particularly the South East and East Anglia. If East Anglia’s daily maximum temperature remains at its current level of 25.2 °C it would easily be the hottest on record, beating 1997’s 25.1 °C. However, on the mean temperature measure it is currently – at 19.4 °C – some way off the 19.9 °C set in 1997.

What lies ahead?

With the return of the westerlies, waters have cooled dramatically around the UK as winds stir the ocean forcing cool water from below up to the surface.

Credit: Tropical Tidbits

We now have a nice North Atlantic tripole of warm-cool-warm. This could have significance towards winter if it were to maintain this profile.

In fact we’ve had significant cooling throughout our northern oceans in the last 7 days.

Credit: Tropical Tidbits

As well as the last 12 months.

This happens in the wake of strong to super El Ninos. Once the net ocean cools, the atmosphere shall follow.

The final week of not just August but meteorological summer will in fact end on a cooler than normal note for the UK into France while high pressure is displaced well into eastern Europe.

Credit: Tropical Tidbits

Credit: Tropical Tidbits

With a cooler northerly feed of air with some arctic origin, rainfall won’t be particularly significant although a series of fronts will sweep through bringing wettest conditions to W Scotland and Northern Ireland.

Credit: Tropical Tidbits

Shades of 2009 showing up?

While by no means identical and the summer certainly wasn’t like what we had to this year but there are shades of 2009 showing up with the overall players currently in place and long term model solutions.

Note the similarity in global SST’s.

Now

This day in 2009

There’s no doubt the waters were a good deal warmer in the arctic and far north atlantic in 2009 compared to this year but we have a similar overall look in both hemisphere’s. We also appear to have a developing ‘central’ Pacific based El Nino. Finally, although it’s not reached the minimum like 2009, we have a very quiet sun and we’re closing in on solar minimum 24, a minimum that’s arguably deeper than that of 2009.

It’s just just the SST’s, a potential ‘modoki’ El Nino or approaching solar minimum but the models are hinting at a similar type of autumn to 2009 with a warm, relatively dry September to increasingly wet but still warm October and particularly November.

For September I expect an active low pressure pattern for Scotland and Scandinavia with average to slightly above average rainfall. However with a stronger than normal Azores high extending into SW Europe, Portugal, Spain, France, Low Countries as well as much of England should stay warmer and drier than normal.

October looks wetter and November should see the Icelandic low dominate but SW winds could keep it very mild. The combination of warm air lifting north from subtropics but low pressure dominant, rainfall could be significant with potential flooding issues.

Aug, Sep, Oct, Nov rainfall compared to norm in 2009.

Met Office

Met Office

Met Office

Met Office

All three autumn months of 2009 were warmer than normal across pretty much the entire UK.

CFSv2 for Sep, Oct, Nov

October 500mb

Credit: Tropical Tidbits

Precip

Credit: Tropical Tidbits

Temp anomaly

Credit: Tropical Tidbits

October

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

November

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Credit: Tropical Tidbits

Featured image source: Wikipedia commons

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