Europe September 2020 Outlook (Brief summer 2020 recap)

Written by on August 31, 2020 in Rest of Europe, United Kingdom & Ireland with 0 Comments

The summer of 2020 will likely be remembered for the period between July 30 and August 10. It was between these dates an this brief period in which historic heat occurred. Otherwise it was a rather changeable and often cool, damp summer.

Here’s how the 500mb geopotential height anomaly has looked for summer 2020.

In terms of rainfall, it was wetter-than-normal each of the three meteorological months overall for the UK with the exceptions of northern Scotland and southeast England. As for temperature, overall it was slightly warmer-than-average summer thanks to June and August both being warmer-than-average. July was slightly below average (coolest since 2012) but 2 out of 3 summer months makes it a warmer than average summer.

Credit: Met Office

Credit: Met Office

July was significant because it was the first ‘cooler-than-average’ July for the UK since 2012. It also almost took the prize for being the first July since 2011 to not reach 30C but that was not to be the case as the thermometer rocketed to an astonishing 37.8C at Heathrow on the final day of the month making it the UK’s 3rd hottest day in recorded history and throw the Cheltenham record of August 1990 to 4th place. Before 2003, it was 1st.

38.7C – Jul 25, 2019 in Cambridge
38.5C – Aug 10, 2003 in Faversham
37.8C – Jul 31, 2020 in Heathrow
37.1C – Aug 3 1990 in Cheltenham

As we opened August, modelling had heatwave and even an August 2003 repeat written all over them. So much so I almost threw in the towel with my August forecast.

While restricted mostly to south and east England, the temperature for a solid week climbed well above 30C. Heathrow and Kew Gardens both observed a reading of 36.4C which turned out to be the UK’s highest August reading since 2003. Further north and even west, it was more unsettled and less warm.

Interestingly, by around the 10th of the month, the unsettled pattern spread throughout the UK and the remainder of the month turned out frequently wet and windy with average to below average temperatures.

Had it not been for the record warm opening 7-10 days of the month then August almost certainly would have followed July in being a cooler-than-average month and may well have made for a more average to below average summer for the UK.

Credit: Michael Ventrice

The final 10 days of August was practically the polar opposite to the opening 10 with an unusually strong jet stream throwing a series of lows across the UK.

Two named storms followed one after the other bringing unusually strong winds and heavy rain which caused disruption and damage, even record August wind gusts to some places. Storms Ellen and Francis were among two of the most notable August storms of the last 50 years with maximum winds of 81 mph on the Isle of Wight.

The closing days of the month and summer also produced unusually low temperatures for the time of year.

As a forecast, Summer 2020 will be regarded as a success

You will never get a forecast 100% correct but when all aspects are considered, it’s been a good forecast this year with the OVERALL low pressure dominated setup. The frequent ups and downs in temperature and the dominance of wetter than normal. I under estimated the hot spells (albeit brief, as expected) and I didn’t see an early August heat wave.

Unsettled theme likely to continue

So, as we wave goodbye to the weird, wonderful and challenging summer of 2020, we commence September and meteorological autumn tomorrow relatively calm. However come Wednesday, wind and rain moves in from the Atlantic. This is associated with the remnants of once Category 4 hurricane Laura which slammed the US Gulf Coast a few days ago.

Ex Hurricane Laura, embedded within a larger low pressure system looks to keep the Azores high suppressed to the south, keeping a cool westerly Atlantic flow going through at least the first 7 to 10 days of the month.

I believe September shall remain largely dominated by low pressure often passing between Scotland and Iceland UK with the Azores high remaining mainly to the south. So, cool, wet and at times windy weather continues. Like we’ve seen through much of the summer, spells of higher pressure is likely to be brief.

Here’s the CFSv2 for Sep 2020.

500mb height anomaly

Credit: Tropical Tidbits

2m temp anomaly

Credit: Tropical Tidbits

Precip anomaly

Credit: Tropical Tidbits


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