Summer Forecast 2019: A More Mixed Summer But Not Without It’s Hot Days!

Written by on May 3, 2019 in Rest of Europe, United Kingdom & Ireland with 0 Comments

Welcome to my 9th 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, El Nino, the mild winter just observed and rainfall distribution over the last 6 months.

2019 has a lot to live up to following the record warm summer 2018

The above factors as well as medium and long range computer models have been used to draw up my conclusion for the summer ahead. This forecast has a lot to live up to following the excellent forecast for Summer 2018.

In-depth

Winter temperature & Spring Rainfall

Rain and consequential moisture levels in the ground can have a significant influence on the atmosphere above. As a general rule of thumb, wet springs tend to produce wet and or cool summers but dry springs such as last year which produced a dry summer and record tying warmest on record.

The precipitation pattern of the previous 6 months just gone have been somewhat erratic and therefore making it hard to determine any influence down the road.

Thanks to above normal heights, winter 2018-19 was drier and warmer than normal across most of the continent except for central areas during the past winter.

Wet March, Dry April

Then came a wet March across the north, dry in the south.

One of the driest April’s followed the wet March.

According to the Met Office, 18 weather stations across the UK recorded their warmest April temperature.

France, Spain and Portugal turned wet during the spring months but despite a ‘regionally’ wet March, the overall picture has been a dry one this spring for the UK.

El Nino, Sea Surface Temperatures & Atlantic Multidecadal Oscillation

There are a few points to make regarding sea surface temperatures but firstly, the sea surface temperatures in the equatorial Pacific continue to support a gradual strengthening of El Nino conditions.

The North Atlantic is currently cold and has been to differing degrees over recent years. A suggestion that the warm phase of the AMO (Atlantic Multidecadal Oscillation) is over and is flipping around.

In 2012, following a warm winter and record warm/dry March, El Nino was developing in the Pacific. In April of that year the pattern flipped entirely from warm, dry March to the wettest April on record.

The likely reason? The combination of warm Atlantic and El Nino.

There is some comparisons between this past winter and spring to 2012, the warm winter, mild March but April was dry unlike in 2012, The bigger difference in 2019 to 2012 however which cannot be ignored, the cold north Atlantic!

The below charts show the comparison in global SST anomalies between the end of April 2012 and April 2019.

End of April 2012

Yesterday

Interesting to see the overall warming of earth’s oceans, especially within the tropics/subtropics but the North Atlantic has flipped colder. The North Pacific is warmer but not to the same extent of difference as Atlantic.

There’s a good deal of evidence which shows a warm Atlantic combined with a strengthening El Nino and increasingly wet spring leads to lower pressure and a wet summer.

A cold Atlantic tends to produce somewhat drier summers for Western Europe.

So, we have a conflict of interest this year. A developing El Nino following a warm winter but the ground is somewhat dry and the North Atlantic is cold. Dry ground, cold Atlantic tends to lean more towards above normal heights during the summer and therefore drier and warmer conditions could prevail.

When specifically looking at the El Nino, this has been known to boost summer heat LIKE IN 2014 and not so much rainfall like in 2012 when the Atlantic was warm. So take out of the equation the warm Atlantic and wet April (2012) and throw in a cold Atlantic and DRY APRIL (2019) and we could have another warmer, drier summer ahead.

SST’s & North Atlantic Oscillation

The cold North Atlantic, warm Norwegian/North Sea supports a trough of low pressure near or over Greenland but a blocking high over Iceland and or Scandinavia. A positive NAO is likely through at least the first half of this summer.

Conclusion

I will make a compromise. While I don’t see a repeat of last years relentless hot, dry weather, what I do believe we’ll see is a combination of both warm and dry and cool and wet. In other words the back and forth we’ve seen in recent weeks is likely to continue but a turn to wetter as the summer progresses.

In the means, warmer and drier weather looks likely from Northern Ireland to Finland beneath high pressure. However, when highest heights compared to normal position further north, there is typically a trough underneath. Therefore southwest and southern Europe could have a cooler, wetter front end to summer.

June 1-July 15th looks mixed with brief spells of rain and cooler weather. When warm and sunnier it could turn significantly warm but cool spells could also be notable.

From July 15-August 31 I believe warmer waters surrounding the UK will prevail and with the El Nino potentially maturing, a wetter 2nd half to summer is likely.

CFSv2 500mb height anomaly month by month.

June

Credit: Tropical Tidbits

Model suggests a changeable June for southwest Europe including the UK with wet or showery days mixed with warm, dry sunny days. Warmest conditions over east and southeast Europe.

July

Credit: Tropical Tidbits

Note the positive over Scotland. This suggests more unsettled weather more often than not from southern Spain perhaps extending up into southern England. Warmest, drier, sunniest North Ireland, Scotland etc.

August

Credit: Tropical Tidbits

Ridge core shifts south and east which suggests more Atlantic influence in August. As stated above, a wetter month looks likely here.

2 metre temperature anomaly for the June-August period.

Credit: Tropical Tidbits

Precipitation anomaly for the June-August period.

Credit: Tropical Tidbits

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