Europe Summer Forecast 2020 & Current Global Warming Situation

Written by on May 21, 2020 in Rest of Europe, United Kingdom & Ireland with 0 Comments

Welcome to my 10th annual European summer forecast. As always, when compiling this forecast for the upcoming June-August period there are multiple factors which have been taken into consideration which could influence the summer pattern. These include global and regional sea surface temperature anomalies, the current and projected ENSO state, the mild, wet winter followed by a warm, dry April and cool, dry first half of May. Other longer term aspects to consider include the solar cycle and Atlantic Multidecadal Oscillation (AMO).

Cooling of east/central equatorial Pacific

It’s of no coincidence that following the previous solar maximum and the Super El Nino of 2015-16 (1st since 1997-98) that global warming has taken centre stage bringing record warm winters and summers.

However, in 2020, we may finally be seeing a flip with cooling rapidly developing over the equatorial Pacific. There is also cooling taking place elsewhere.

Credit: ggweather.com

Each moderate to strong El Nino sees a rise in global temperature.

Global temperature of the lower atmosphere since 1979.

Credit: Dr Roy Spencer

In the above graph, note the surge in global temperature with each El Nino and the drop off afterwards. Also note that there’s less cool off with each El Nino compared to the previous. Why is that? Blame CO2 or something else.

I believe the cause of warming is more likely or plausibly down to an increase in water vapour from the warmer ocean.

This warmth in the ocean and atmosphere has most certainly increase summer temperature and rainfall for the UK.

What brought the warm, wet winter followed by cooler, dry spring?

Warm globe, warm ocean, lasting effects of El Nino. Especially warm west-central Pacific waters enhanced the warm phase of the madden julian oscillation (MJO) which in turn strengthened the polar vortex. This held below normal heights in the high latitudes and stronger than normal heights in the mid latitudes with a strong zonal jet stream in between. Record warmth and rainfall was the result across the Northern Hemisphere.

The 360-degree flip from February to April?

The combination of an eastward shift in the MJO and the unraveling of the polar vortex led to a blocked, dry pattern switch from winter to spring. The later than usual release of cold from stratosphere to troposphere I believe aided an unusually blocky and cool May. This also reduced SST’s surrounding the UK which is likely to have early summer influence.

The ongoing cool (past few years) across the North Atlantic has been driven by a stronger than normal winter jet stream. These persistent westerlies has forced continuous upwelling, lifting cold water to the surface.

Let’s take a closer look at the current global sea surface temperature anomalies (SSTA’s). As you can see, the North Atlantic has warmed due to a negative North Atlantic Oscillation over recent weeks (Greenland high) but the waters around the UK and particularly the North Sea has cooled sharply thanks to persistent north, northeast winds lately.

Credit: Tropical Tidbits

Interesting to see the North Pacific nearer to North America has warmed significantly over the last 2 months, like with the North Atlantic, this is thanks to an Alaska high, particularly in April and May.

With both Pacific Decadal and Atlantic Multidecadal Oscillations are in their warm phase, most evident over the northern basins. As you can see, it t doesn’t take much ‘weather’ for them to go from cool to warm as their net area overall is warm which explains the global warmth overall.

All the above being said, are we ready to see a global shift?

The last 7-days shows more cooling than warming globally.

Credit: Tropical Tidbits

Here’s a closer look at the 7-day change over the North Atlantic.

Credit: Tropical Tidbits

What role could cooling oceans, developing La Nina and low solar cycle have on summer?

There is indeed land influences from regional cooling or warming of ocean areas but these are relatively brief perhaps only last a couple of months to perhaps a year.

Until we see entire ocean basins cool, earth’s temperature simply won’t fall and the atmosphere may take 2-3 years to respond to a cooling ocean beneath.

As you can see from the below graphic, we appear to be nearing the end of a solar period known as the ‘modern maximum’. There’s a great deal of science suggesting that the sun is the primary driver of our earth’s climate system. So, I guess if you increase the output from the sun, you warm the oceans and the oceans warm the atmosphere.

If we are indeed approaching another maunder minimum type period then it will be very interesting to see IF our earth will begin to cool in response to the sun’s lower energy output.

Between 2015 and 2020, we have seen a tight cluster of ‘hottest years on record’, including record warm and wet winters and record heatwaves in summer, enhanced by more frequent warming El Nino’s than cooling La Nina’s (hence the lack of cooling). So, essentially the warmth has been building both in the run up to the last solar maximum of cycle 24/25 and in the wake of it.

The next 12-24 months is going to be very interestibg our next solar minimum. Let’s see what happens THIS summer regarding heat and let’s see if our oceans will start cooling as we meet supposedly the weakest solar cycle in 200 years.

Credit: abruptearthchanges.com

Following the recent years of enhanced global warmth, driven by the 2015-16 Super El Nino, as we decent into the next solar minimum, it will be interesting to not only see if we get a repeat of the solar minimum winters of 2000-01 and 2009-10 over the next couple of years but also if earth’s temperature comes down in any significant way.

I believe there is somewhat of a larger scale shift underway and let’s watch the next 12 months as we should start to turn down the thermostat of our earth’s atmosphere down. The Atlantic is due for a return to it’s cold AMO phase and I believe there’s evidence to suggest this change has begun.

So, what may the short & long term players and influences do to summer 2020?

Firstly, I recon the warmest part of summer comes early (June 1-early July). Sure we’ll get warm to even hot days throughout the summer.

A troughy summer?

There’s a strong correlation between warm, wet winters followed by dry springs to deliver an overall disappointing summer. These can be cool, wet or cool dry or even warm and wet but lower than normal pressure tends to be over or nearby to the UK.

The Balkans, Greece, Turkey, Cyprus and other southeast European countries is currently baking in all-time monthly record heat. I believe this region continues to see very hot conditions but further north and west into central Europe, negative heights will become more establishes as the summer months progress.

Potential implications of warmer/cooler SSTA’s, dry ground on the atmosphere?

Current dry ground surrounded by cooler than normal ‘regional’ waters suggests higher than normal pressure over the UK and Western Europe as we progress from spring into summer.

Credit: Simon Cardy

May has seen barely a drop of rain in places on the heels of one of the driest April’s.

Credit: BBC Weather

Here’s the CFSv2 forecasted global sea surface temperatures for June through August.

Credit: Tropical Tidbits

My Verdict

June 1-July 15

With a very dry spring, you could and I certainly have, assumed another hot, dry summer like 2018 was upon us once again. Especially when you’ve got very dry ground, surrounded by cool water which tends to support above normal high pressure aloft and enhanced surface heating with less of the sun’s energy taken up with evaporation.

However, looking back at similar past winters and springs to this year and the general trend is towards quite the opposite.

That being said, I do suspect high pressure should be the dominant force over France and at least the southern half of the UK and Ireland through the early summer with temperatures above normal and rainfall below average but I don’t see it holding. Nearby fronts associated with low pressure near Iceland could keep Scotland and Northern Ireland as well as northwest England more unsettled.

As we progress into the heart of summer (July), waters surrounding the UK will have likely warmed to normal or above while the La Nina in the Pacific strengthens. With other potential factors becoming involved I believe the high over or near to the UK either slips south and east opening the door to an Atlantic low or it shifts west into the Atlantic. Either way it should turn cooler and more unsettled.

Like in 2015, there is also the potential for big fluctuations in temperature between very warm and cool. A good and current example of this is the significant surge of heat over particularly England yesterday following the coldest air in 20-40 years just a week previous. This warmth is brief and shall quickly be replaced by low pressure packing wind and rain tomorrow.

Short, possibly intense surges of heat followed by cold and or rainy spells is likely.

The east and southeast of Europe looks warmest compared to normal.

July 15-August 31

As the summer progresses beyond mid-July, we must watch the MJO and it’s influences on the Atlantic. We expect an active hurricane season this year and this is likely to have direct influence on the mid latitude and UK/Europe pattern, especially late July/August.

All in all, heights lower as the summer progresses. Cooler SHOULD be the theme but in terms of rain, it really could go either way. The amount of warming seen over the North Atlantic and surrounding the UK could determine how wet the summer gets.

Another aspect worth pointing out. Dry springs tend to see a negative Arctic Oscillation and North Atlantic Oscillation dominated summer which means northern blocking and troughs near to the UK.

Here’s the latest CFSv2.

500mb height anomaly

June

Credit: Tropical Tidbits

July

Credit: Tropical Tidbits

August

Credit: Tropical Tidbits

Precipitation anomaly

June

Credit: Tropical Tidbits

July

Credit: Tropical Tidbits

August

Credit: Tropical Tidbits

2-metre temperature anomaly

June

Credit: Tropical Tidbits

July

Credit: Tropical Tidbits

August

Credit: Tropical Tidbits

ECMWF has a warm, dry summer with +AO/NAO.

Credit: ECMWF

Met Office model for June-August 2020 period.

Credit: Met Office

Credit: Met Office

Credit: Met Office

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