Welcome to my 14th annual UK, Europe summer forecast. As always, when compiling this forecast for the upcoming June-August period there are multiple factors which are taken into consideration. They include the past winter pattern, type of spring just observed as well as the current ENSO state, global and regional sea surface temperature anomalies as well as current solar state!

Comparing Spring 2023 to 2024, Similar?

There is a degree of similarity in the spring pattern of 2023 to this year as seen in the below 500mb pattern but not without some key differences.

Spring 2023 had a notable positive over both Greenland and Iberia with deep negative over the central North Atlantic extending up through the UK/Ireland into central Europe. That positive may have been aided by the mid/late February SSW.

Spring 2024 has that northern blocking but more banana shaped extending from the Baffin Straits across to Scandinavia. Far less of a positive over Iberia. The reason for such persistent northern blocking? Perhaps frequent SSW’s and a late final warming of the stratosphere? Perhaps the easterly QBO? SST profile of the North Atlantic? Could be all of these or none…

Nevertheless that persistent block over Greenland has helped push the jet south and with some sort of ridge weak or strong, this has aided a negative or trough pointing at our part of the world.

So, similar upper pattern between both springs but… the trough core is almost directly over the UK (trapped underneath the block) this year compared to being centred out over the Atlantic last year. The stand out to this is a considerably wetter spring this year compared to last yet May is turning out slightly drier compared with March and April.

Spring 2023 was close to average for both temperature and rainfall compared to a warmer, wetter spring 2024 for UK/Ireland and much of Western Europe.

Interestingly both May 2023 and 2024 have seen significant severe weather and flooding across a large swathe of central and southern Europe thanks to an omega blocking pattern.

Italy’s Piedmont witnessed their wettest May in 2023 for 70 years and 2024 has been the wettest overall spring in 70 years.

500mb geopotential anomaly for June-August 2023

Summer 2023 started record warm, sunny and dry in June for the UK/Ireland, cool and often wet across Iberia. The high over low setup abruptly flipped in July and continued through the remainder of summer before turning warmer and drier in September where the warmest temperatures of the entire year occurred.

The UK observed it’s warmest of the three meteorological summer months in June, first time since 1966 and first time September hosted the warmest temperatures of the year since 2016.

As can be seen in the below CDAS 0.5 data, June was very warm but July and August were both average to slightly below average but the record warm June overwhelmed and made summer as a whole warmer-than-average.

June 2023 temp anomaly

July 2023

August 2023

In terms of high over low pressure, both 2023 and 2024 has seen quite a similar rainfall pattern, especially in May with drier north, wetter south and rather unsettled or stormy pattern in Europe.

This wet spring follows on from a wet winter with extension all the way back to July 2023 which means soil moisture content is reasonably healthy going into this summer for west and central Europe including most of the UK and Ireland. Drought persists through the Canaries, eastern Iberia and much of the Med Basin and Balkans.

 

Another perspective.

Transition from El Nino to La Nina

Eastern Pacific SST’s as of May 23.

Surface waters of the eastern equatorial Pacific continues to cool and this ongoing process should take the ENSO region into La Nina territory over the next few months, likely peaking late autumn or early winter.

Multi model projection

NMME SST’s for Jun-Aug 2024

The significance of these cooling waters with time causes a change in winds over the Pacific and eventually the entire global wind oscillation. This results in a shift in rainfall distribution around the world.

The key question becomes, assuming we continue to see the development of a La Nina, when will the atmosphere respond.

Here’s an interesting graphic courtesy of Severe Weather Europe showing past transition years and what the atmosphere and temperature has looked like within the mid latitudes.

Speed of the transition from Nino to Nina can be significant. Faster developing Nina’s have been known to bring cool, wet UK and even Europe summers as can be seen above, especially mid to late season. However we must take into consideration that some past Nino to Nina transitions occurred back when the overall ocean, land and atmosphere was cooler.

One major influence of a cooling east Pacific is a strengthening of high pressure and sinking air above. This leads us on to the Atlantic below.

Warm Atlantic

Atlantic SST’s as of May 23.

A record warm tropical Atlantic and cooling east tropical Pacific tends to favour large-scale high pressure or sinking over the cold east Pacific while lower pressure or rising over the warm tropical Atlantic.

A reduction in upper level westerlies aids tropical cyclone development in the Atlantic but what happens within the tropics can have influence further north.

As we look at the North Atlantic we have a largely warmer than average profile with some cooling both off the US East Coast as well as a pocket SW of Ireland.

Waters surrounding the UK have arguably warmed in recent weeks. The effects of the overall warmth with smaller areas of cool on the atmosphere remains to be seen but I suspect this warmth later in the season could enhance low pressure and rainfall events.

Interestingly, there are some interesting findings from World Climate Service on past ‘similar Atlantic SST’s.

Excerpt from their tweet

“One of the more “interesting” analog signals in our recent summer forecast is the set of years with most similar N Atlantic SSTs. The pattern looks reminiscent of summer 2012 for Europe, although that year isn’t one of the analogs. Probably not what the UK crowd wants to hear.”

I suspect a warmer Atlantic with wet soils over much of Western Europe ‘may’ lead to less aggressive heat and potentially lower pressure over the NE Atlantic/NW Europe and higher pressure and frequent heat through southern and eastern Europe when considering the 90 days of meteorological summer.

Are We About to Loose The Greenland Block (-NAO)?

For the most part, a persistent block has been present over or near Greenland in the past 12 months. The question is, will that block remain for this summer? If so, we would likely continue seeing a further south jet or storm track with a good chance of seeing ridging over S and SE Europe, this may put the UK and Ireland once again in the firing line of Atlantic low pressure.

I wouldn’t be surprised if the block starts off fairly strong in the wake of the final stratospheric warming but as the La Nina base state matures we may loose Arctic and Greenland blocking.

The majority of the long range models show a weak negative for June then positive July and August as per this World Climate Service graphic.

Solar Maximum 25

We are in the peak of solar cycle 25. The sun is the most active it’s been in some 20+ years. Whether this helps with a warming of ocean, land and or atmosphere, I don’t know. I use to believe solar maximum can have a warming influence but I am not sure.

Potential Influence of a busy Tropical Atlantic?

Another important factor in this forecast is the high likelihood of a very active tropical Atlantic. The above outlook from NOAA is their most aggressive ever.

Interaction between tropics and mid latitudes becomes greater later in the summer and it’s going to depend on the strength, position and steering of the mid Atlantic ridge.

The Azores high can often start off strong early season then can hand off to it’s western counterpart, the Bermuda high later July and especially into August. That cool pool east of the US may help boost the Bermuda high during the second half of the season and therefore any tropics waves or systems which can forced into the Carib or Gulf of Mexico rather than turning north.

Forecasting number of named storms is one thing but in our case, where they go is another. While I suspect many systems whether it be storms or hurricanes will head west for the Caribbean and Gulf of Mexico, there are likely to be a bunch which make a turn north. As these ‘heat cores’ leave the tropics and head north, they can have several different influences on the jet and the ridge-trough pattern which then has influence more often than not on the Europe pattern directly or indirectly.

My hunch is an overall warmer and wetter than normal summer for much of western Europe, drier and warmer across the south and east of the continent.

With the potential of a strong Azores or Iberia high, spells of heat will lift north, periodically paying a visit to the UK, more likely later in the summer. The pattern can be heavily influenced by tropical activity and it’s interaction with the mid latitudes by boosting high pressure or deepening low pressure.

The amount of water in the ground could well temper the strength of UK heat this summer, perhaps lowering the ceiling to a maximum of 32-34C between June 1-August 31.

Relevance of the MJO (Madden Julian Oscillation)

The MJO is a two-part wave of enhanced and suppressed convection over the tropics (fueled by the warm tropical waters of the Indian and Pacific Oceans). While one region (hemisphere) experiences the active branch with enhanced thunderstorm activity (lower pressure), another experiences sinking (high pressure). The importance and influence of the MJO can have global impacts and this teleconnection is often used in my forecasts.

Currently we have an active phase 4 MJO pulse which is enhancing convection (thunderstorm activity) rainfall over the maritime continent (SE Asia, Indonesia and Australia).

Note in the latest GFS operational run for May 28th below shows deepest greens extend from Australia to Japan representative of phase 4 and enhanced rainfall and thunderstorm activity with greater chance of tropical cyclone development in this region. This forces enhanced sinking over the America’s, Atlantic and Africa.

Note the majority of heaviest rainfall between May 28 and June 7 is over SE Asia courtesy of the phase 4 MJO.

So take this a step further and have a look at the CFSv2’s projection in a month by month breakdown.

According to the CFSv2, June looks to see a favourable MJO with convection extending from Americas to Africa with chance for above normal activity. Then a return of enhanced convection over Africa and Atlantic for the heart of the season in August.

July suggests less favourable conditions for W Atlantic and Americas with active MJO returning to Indian Ocean and Africa but could lead to a robust West Africa monsoon and African wave activity which could lead to plenty of activity over the Atlantic with less favourability towards the Americas.

Then comes August and the greens (rising air) return to the Atlantic with widespread sinking over Pacific as we head towards the heart of the season. A classic La Nina atmospheric signature.

An active tropical Atlantic or not, the above phase 1-8 of the MJO can have influence on Europe and I shall be discussing it’s relevance to our weather in-depth in the coming weeks (stay tuned on my Youtube channel for discussion)

EXAMPLE

Below graphic is possibly a little more relevant to winter but…

However

Phase 7-8-1: Can enhance tropical activity between Africa and Americas but also blocking over/near Greenland leading to cooler, wetter UK/near continent

Phase 4-5: Can help bring warmer, drier weather to UK/W Europe

What Happening with the IOD (Indian Ocean Dipole)

Current status

NMME suggests a a fairly uniform warm IO SST profile for June-August.

However, a positive IOD looks likely for the summer ahead as can be seen by the majority of long range models.

World climate service states that during a positive phase of the IOD, there can be a tendency for warmer, drier summers over central and eastern Europe HOWEVER that is typically during a warm ENSO phase, not cool.

Long Range Models (June-August)

Met office model

Mean sea level pressure

Precipitation

ECMWF

mean sea level pressure

Precipitation

Meteo France

mean sea level pressure

Precipitation

Multi-model Europe view for June-August 2024

My Prediction

Rainstorms or flooding downpours and unusually cool summer days are possible with a lot of fluctuations between low vs high pressure but I think low pressure may win the battle.

There will be relatively short lived hot spells. Slightly longer and stronger the further south and east over the UK/Ireland you are.

With the direct or indirect influence of the tropics, one cannot rule out an August of two halves. By which I mean tropics entities lifting north over the Western North Atlantic can boost high pressure over the UK and Western Europe leading to a lengthy spell of fine summer weather but the very same systems can run right around the mid Atlantic ridge and pay a visit to our shores bringing unseasonably wet and windy conditions.

June

After a cool start to the month, it may turn more unsettled and overall a mixture of spells warm and dry, cool and wet.

Cool, dry first half to likely to be followed by warmer possibly wetter 2nd half.

Near average to slightly below average temperature/average to below average rainfall: UK max: 30C

July

July has probably the best shot at the longest and warmest period of summer and so I shall go for warmer but slightly drier than average overall. UK max 32C

July could see a moderate to severe heat event from Iberia to Turkey.

August

With the tropics becoming more involved, I suspect we have, like June, quite a mixed month with spells of high and low pressure bringing highly variable weather. Days of warm and sunny interspersed with low pressure bringing wet and windy as well as cool days. UK max 33C

Overall a Slightly WARMER & WETTER Than Average Summer is expected for UK, Ireland, France, Low Countries & parts of S Scandinavia too… Drier, Well ABOVE Average across S and E Europe!

NOTE: THIS ARTICLE WILL CONTINUE TO BE UPDATED UNTIL JUNE 1st.

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