It’s been a summer of pattern persistence with the late spring shaping June and July. The North Atlantic’s warming off Newfoundland and cooling off Ireland with no outside forcing to disrupt has provided a cool and often unsettled west Europe vs hot, dry east Europe with stormy in between.

500mb geopotential height anomaly 1 May through 6 July

300mb mean zonal wind anomaly 1 June through 16 July.

June 2024

With the exception of a brief warm spell which saw 2 consecutive days above 30C in SE England, June was a cool month and July is no better.

July has been incredibly similar with persistent central North Atlantic ridging with cool WNW flow into the UK and Ireland

1-10th July

According to the Met Office, the UK summer through mid July has been remarkably cold by recent standards. Since the year 2000, only one year was this cold from 1st June to 8th July (2012).

In the 1970s, five summers were as cold or colder up to this point (71, 72, 74, 77, 78) In the 1960s, also five (62, 64, 65, 67, 69).

No of days of +25C for 1-11th July. Graphic via Willie Mossop (Ex Met Office)

Almost exactly like we saw during the final 10 days of June, winds took a turn…

Almost exactly like June, the final week to 10 days have seen winds turn from WNW to SW allowing for one day over 30C in the Southeast of England and warmest for UK of 2024 so far (31.9C at St James Park, London). However, the heat didn’t quite make it north like in June (albeit for a day).

Despite the warm-up, July ended up (like June), cooler than average while much of the continent was warm.

Late July hosts peak summer temperatures across Europe. Here’s a nice graphic from Brian Brettschneider.

July 2024 saw Scotland’s latest 25+C since 2010.

According to Sean Batty of STV, Floors Castle did manage 25.2C back on the 19th so July 2024 wasn’t completely absent of the 25C threshold like 2010, 2007, 2002, 1998 and 1993.

All in all it’s been a remarkably persistent Atlantic-Europe coupled pattern and the North Atlantic SST profile has a lot to do with it I think.

If you watch the below 90-day SST loop and watch the build-up of anomalous warmth east of Newfoundland, that’s where our mean ridge has lived all summer long.

and the proof is below in the 1 June through 19 July 500mb geopotential anomaly… Our mean flow has been WNW really extending back to May.

As the jet has dipped south over western Europe, it’s been north thanks to a downstream ridge over eastern Europe, aided by building drought through spring.

First 10 days of May.

Here’s the end of May.

Based on both SST and eastern Europe drought discussed above, here’s temperature anomaly for the past 60-days.

This was my ridge/jet stream forecast for July, a repeat of June.

Summer idea overall (released at the end of May)

I think you’ll agree, a decent call thus far.

While I believed lower pressure dominates the NW and ridging S & SE, I underestimated the lack of high pressure episodes and consequential warmth associated with those. This summer’s warmth likely constitutes about 1 to 1.5 weeks out of a possible 6 so far.

So, from my perspective the Atlantic has run the show so far in terms of upper pattern and aided by the eastern Europe drought but where do we go heading into summer’s final month?

MET OFFICE: Contrasting conditions in a cool and dull July

July 2024 Monthly Weather Report

UK July Highlights

Highest Maximum 32.0°C on 30th at Heathrow (Greater London, 25mAMSL) and Kew Gardens
(Greater London, 6mAMSL)
Lowest Maximum 10.8°C on 13th at Brizlee Wood (Northumberland, 250mAMSL)
Highest Minimum 19.6°C on 31st at Isle Of Portland (Dorset, 52mAMSL) and Swanage (Dorset,
10mAMSL)
Lowest Minimum 1.7°C on 31st at Tulloch Bridge (Inverness-shire, 249mAMSL) and Tyndrum No 3
(Perthshire (in Central Region), 168mAMSL)
Lowest Grass
Minimum -2.2°C on 31st at Dalwhinnie No 2 (Inverness-shire, 351mAMSL)
Most Rainfall 75.7mm on 8th at White Barrow (Devon, 445mAMSL)
Most Sunshine 15.3hr on 7th at Dale Fort (Dyfed, 33mAMSL)
Highest Gust 50Kt 58mph on 4th at Brizlee Wood (Northumberland, 250mAMSL)
also on 5th at Wight: Needles Old Battery (Isle Of Wight, 80mAMSL)
Highest Gust
(mountain*) 72Kt 83mph on 4th at Cairngorm Summit (Inverness-shire, 1237mAMSL)
Greatest Snow
Depth at 0900
UTC
No non-zero values.

July Score: 8.5 out of 10

August: A Repeat of June & July?

Did you notice at the very end of the SST animation above the slight filling of the cool pool west of Ireland and also have you noticed the westward shift in the ridge over Europe? It’s heating up over Iberia while slightly cooling down over the Balkans in the past week.

I ask myself the question, is this a temporary shift and the pattern returns to it’s default setting or is there a more fundamental shift taking place. Natural shift or increasing strength of the west African monsoon trough, helping pull the mean ridge to it’s north west.

As we head into August, the ITCZ (inter-tropical convergence zone) and subtropical ridge will naturally be at their most northerly position, we know the tropics will come alive again, helped by an eastward propagating MJO wave.

Therefore I expect TWO outcomes, both of which may occur, 1) a possible eastward extension of the ridge over the Atlantic into the UK (warm and dry). Strengthening of the Iberia high exerting greater influence to the north over UK and Ireland compared to June-July, 2) tropical cyclones development and interaction with the mid-latitude flow. Where do they go? Towards Caribbean/Gulf of Mexico? or do they find the weakness within the Bermuda-Azores ridge or around the western flank up the East Coast of the US? These are important factors to consider. There is two types of recurve, 1) a western Atlantic recurve which can lead to deepening UK/NW Europe trough while 2) a central Atlantic recurve can help pump high pressure and warmth from Iberia to UK even leading to heat wave conditions, plenty of August’s and possibly more so September’s have been this.

We end July warm to hot over SE UK (less Scotland/N Ireland) but GFS ensemble has a trough swinging back over the NW of Europe through week 1 and 2 of August. A return to the original pattern.

The warm to hot end of July for NW Europe nicely correlates with the current phase 5-6 MJO.

 

The GFS ensemble has a cool trough swinging in mid week on…

An amazing stretch of ‘sameness’ which enters it’s 3rd if not 4th straight month!

Any better with CFSv2 weeklies?

Cool first half, warmer 2nd? Well that’s been the story of both June and July so why not August?

I expect a warmer 2nd half to the month with potentially a spell of HOT for most if not all UK and Ireland with tropical forcing involved.

When looking at the month as a whole, the GFS extended shows much of the same, a flat zonal Atlantic flow with low north, ridge south. England possibly Wales always favouring warmer, drier than Scotland and Northern Ireland.

Dry outlook.

A rare 3rd straight cooler-than average month?

The latest run of the ECMWF 30-day shows similar flat zonal flow with slightly higher heights covering more of UK. with cooler north, warmer south with drier than average for all UK and Ireland except NW corner.

I expect average to slightly above average August for temperature and slightly drier across the UK and Ireland. Slightly cooler, possibly wetter Scotland, Northern Ireland, NW Rep of Ireland while drier across England and Wales. A hot, dry month for much of Europe

Tags: featured, monthly-outlook