The difference between June and July 2023 just ending has been like chalk and cheese, polar opposites. High pressure (centred just N of Scotland) in June was replaced by low pressure (draped across Ireland, UK and Scandinavia) in July.

From the warmest June on record (as per Met Office) to what looks likely to be slightly cooler and considerably wetter than average. In fact one of the UK’s wettest on record.

June 2023 500mb anomaly

July 2023 500mb anomaly

It looks likely to be the first summer since 1970 in which June was warmer than July according to Neil Kaye of the Met Office.

https://twitter.com/neilrkaye/status/1683402055463976960

The developing El Nino may have played a role (along with other forces such as the MJO, warm Atlantic) in the upper air switch from June to July.

This rather dramatic June to July switch was (rightly or wrongly) inspired by the developing El Nino and solar cycle being similar to 2012.

The transition from La Nina (prolonged period 2010- early 2012)  had similarity to the triple dip-La Nina we just came out of) along with solar cycle.

Summer 2015 also has an El Nino and July saw some big temperature extremes featuring record hot and record cool days with flash flood events. I believe those extremes were possible in July 2023.

Weather Highlights for July 2023

An unusually deep and potent low pressure system affected the southern UK and near continent on 5th July producing a months worth of rain in parts of East Anglia before hitting the Dutch Coast with hurricane-force wind gusts.

Said to have contained a potential ‘sting jet’, the system produced wind gusts of up to 92 mph, the strongest ever recorded during the summer months in the Netherlands. This wind event was similar though not as intense which hit the same area back at the end of July 2015.

While temperatures at or above 25C were rare anywhere across the UK and Ireland during July 2023, a short lived heat spike occurred between 6-8 July where temperatures topped 28.5C at both Kinloss and Lossiemouth on the Moray coast meanwhile the UK maximum was 30.2C reached in SE England.

Beyond the 10th, the UK and Ireland became increasingly cool and wet and so the focus of heat was south and east. Building initially over central Europe, a new surge started in the Canary Islands which spread east from Iberia to Turkey. This would prove historic!

https://twitter.com/extremetemps/status/1679762663214141440

https://twitter.com/extremetemps/status/1681282591184281600

https://twitter.com/extremetemps/status/1681738048495648768

https://twitter.com/WxNB_/status/1681324727812468736

https://twitter.com/extremetemps/status/1683182265784758272

https://twitter.com/extremetemps/status/1683543614083743759

https://twitter.com/cinicodippiu/status/1683833032254398465

https://twitter.com/WxNB_/status/1683819658657271808

Current SST’s surrounding Italy as of July 25th.

ALBANIA: 44.0 at Kucova NEW ALL TIME NATIONAL RECORD

While the Mediterranean baked, the UK was soaked and struggled temperature-wise with some (many) days stuck at between 12-15C for highs.

One weekend after the next saw low pressure spread a band of rain across Ireland and UK followed by heavy showers and thunderstorms.

One particular system saw a central pressure fall to 984mb over Northern Ireland, possibly the deepest July low to affect the UK and Ireland since 1988 according to Syran Bruan.

Unseasonably strong winds gusting 40-60 mph affected southern England and Wales which thunderstorms and downpours causing floods affected northern UK.

https://twitter.com/bbcweather/status/1683417761505001473

https://twitter.com/TheSnowDreamer/status/1683832316614041608

Huge Clash Between Air Masses!

Between the fresher Atlantic air over N Europe vs extreme heat over the Med, violent weather erupted along the boundary. The Alps and Balkans have been a focal point where severe winds, flash floods and monster hail has caused significant damage and even death.

https://twitter.com/MateuszTaszarek/status/1683767138996158465

https://twitter.com/capitalweather/status/1683882608923488279

Earlier in the month…

Stornoway town on the Western Isles observed not only it’s wettest first half to a July on record with over 100mm of rain but within that same 13 day period they also observed the 2nd warmest day thanks to strong ESE winds lifting the temperature to 26.6C on the 8th. The record is 27.0C set back in July 2014.

Wettest July On Record For Northern Ireland, 6th Wettest for UK!

The NAO has been predominantly negative throughout summer so far with slight negative in June to deep negative in July.

That negative NAO in July led to the trapping of a trough across NW Europe which in turn led to the heatwave across the Med, one trapped upper feature then traps another! Throughout July lows have often cycled around one another or developing where NW and SW jet stream winds have met creating an area of incubation or cyclogenesis W or SW of Ireland.

Wettest July on record for Northern Ireland

Meanwhile in Ireland…

https://twitter.com/METclimate/status/1686683579156213760

The most anomalous trough within the hemispheric wave 5 pattern was across N Europe and this in turn trapped the heat dome over the Med.

I WILL PRESENT THE STATS HERE WHEN AVAILABLE

Will August Continue the Cool/Wet UK – Hot Mediterranean theme?

Despite a change within the Hemispheric pattern possibly attributed to the MJO, August looks likely to remain unsettled across NW/N Europe. At least through the first 10-15 days. Further waves of heat is possible from Iberia through the Med and into central and eastern Europe.

The month commences with a pretty flat, zonal flow connecting Canada with Europe, the UK and Ireland shall see the continuation of low pressure bombardment but through week 1, the ridge returns to a position W of Ireland which keeps the trough stuck and low pressure active. As heights rise over the Atlantic, NW or N winds will push sub-arctic air south over Ireland and UK keeping temps below average. The presence of LP and cool air aloft will also keep the showers active with longer spells of rain. In the sun, it will feel pleasant.

I believe the first half of August remains firmly below average temps, slightly above average rain.

The question is, can we possibly maintain this pattern throughout the month or will we see a shift to higher pressure. Hard to imagine LP with cool, wet conditions can maintain it’s grip ALL MONTH so I’m going to suggest we catch some variability beyond day 15-20 and a chance at some warm to hot air possibly lifting into at least the south and southeast UK during the final 10 or so days of August.

We’re likely to see some tropical cyclone development during the month. With warmest waters compared to normal further north and away from the main development region of the ATL, we have the chance of seeing some pretty far north tropical features whether it be storms or hurricanes. What’s important about these systems as they move north towards the mid-lats is they drive tropical heat north and can either strengthen or buckle the jet stream leading to an enhancement of the trough or it could kick it out of the way and present a new HP driven pattern.

August is a difficult month to call but I shall lean cool and wet and go against the grain of recent past.

500mb height anomaly week 1-3 off the CFSv2

Precipitation anomaly

Temperature anomaly

CFSv2 monthly shows a pretty rare wetter and cooler than average August!

AUGUST VERDICT:

AVERAGE to Slightly BELOW AVERAGE temperatures, Slightly ABOVE AVERAGE rainfall for both UK & Ireland

FREQUENT SPELLS OF COOL & WET DRIVEN IN BY A STRONGER THAN NORMAL ATLANTIC JET STREAM  & COOL FOLLOWING LP’s THROUGH ‘AT LEAST’ THE FIRST HALF OF THE MONTH FOLLOWED A SMALL POTENTIAL FOR WARMER, DRIER FINAL WEEK TO 10 DAYS!

As for Europe

Like we saw in July, more heat across the Mediterranean Basin but not quite as intense with 40-44CC Iberia, Italy, Greece, Turkey, 38C Balkans, 38C Southern France/32C Northern France, 28-30C Low Countries, 32C Germany, Poland, 35C Romania, Bulgaria, 32C Moldova, Ukraine, fresher 26C Lithuania, Estonia, Finland & Scandinavia only 23-25C…

Projected Max Temps for July for UK/Ireland:

England: 28-30C

Wales: 27C

Scotland: 26C

Northern Ireland: 25C

Rep of Ireland: 26C

FEATURED IMAGE CREDIT: Petr Kolegar

Tags: featured, monthly-outlook