July like June has been a month featuring a little of everything. Some notable heat, cool and wet in what’s been a summer leaning more warm than not. Rainfall distribution has been highly variable, especially with thunderstorms.
The first half of the month saw the heat focus from Iberia to Scotland before shifting north and east as Atlantic disturbances brought cooling, wet relief. While cooler Iberia, France, much of the UK, especially north has remained warm, albeit more unsettled.
I believe the pattern shift was initiated by an MJO initiated eastbound Kelvin wave crossing the Pacific which forced heat to split north and east across the continent Europe.
The hottest air of the year refocused on Scandinavia and east through Italy into Greece and Turkey.
Past 10 days vs previous 10 days.
18-28 July.
8-18 July
We’ve witnessed spells of thundery rains and longer system rains which will lean July overall average, perhaps above average for UK/Ireland and near continent (France, Low Countries) with local variability as is often the case. Also, like June, July will go down as a warm month widely. Warm nights will help boost the monthly average mean.
Temp anomaly 1-30th Jul
Precip anomaly for the past 30 days
COOLER/UNSETTLED END TO JULY – START TO AUGUST
While heat has been extreme over Italy, Greece, Turkey as well as Scandinavia with a record 14 straight 30C days in Finland and 13 in Norway, the heat edges off the ‘extreme’ for both regions as unusually cool air expands over Central Europe. Unfortunately storms and big rains shall be a negative consequence of the cool down.
Due to a combination of factors including MJO, sharpening thermal gradient and strengthening Atlantic jet stream, early August (around Mon 4th) could host the passage of an unusually deep low presenting a spell of heavy rain and gales for UK/Ireland. Depth, position and whether it even materialises is all an open question.
In the broader view, Two upper ridges dominate the close to July/open to August (one W of Ireland & another east of Finland) with systems running in between helping reinforce a cool trough over Italy.
PRESSURE BUILDS EAST FROM ATLANTIC ACROSS EUROPE MID/LATE MONTH?
The CFSv2 above shows the cool/dry central and warmer/wetter east as we progress from week 1 into week 2 of August. The cool expands over UK/Ireland courtesy of that ridge holding firm WEST of Ireland and trough to the east.
Week 3 and 4 builds the pressure eastwards…
Week 1 through 4 suggests a drier than average theme for Ireland and UK as the ridge provides shelter from the Atlantic then bodily builds in over UK/Ireland and potentially much of the continent’s central and southern regions.
CFSv2 500mb heights week 3 and 4
Precip anomaly week 2-3-4
Temp anomaly week 3-4
I do expect 1 or more periods to exceed heatwave conditions for England and Wales, possibly NI and Scotland during August. If so, this would complete my forecast expectation of ‘heatwaves’ in each of the 3 summer months in 2025. Further days above 30C, particularly South and Southeast UK.
GFS Ensemble next 30 days
ECM Weeklies
While I believe ridging will build quite firmly over the UK between 10-20th of August, it will be interesting to see 1) what develops within the tropical Atlantic and 2) how strong 3) where these features go IF they form as this could drive the N Atl/Euro pattern mid and particularly late month. I believe the tropics could play a crucial role later but it depends upon how conducive the tropical environment becomes as for now there’s lot’s of dusty air and shear despite the MJO somewhat removing the lid from the upper levels.
More troughing 20th on? Possibly.
The Verdict…
Average to above average for both temp & rainfall for Northern Ireland and Northern UK, Warmer/Drier England/Wales. Drier/Warmer West/Southwest Europe, Cooler, Wetter East/North!
FEATURED IMAGE CREDIT: Peter Chisholm @thetrekpete
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