Our turbulent summer so far here in the British Isles continues with a strong low pressure system currently overhead bringing a lot of wet and breezy weather. While tonight sees the return to very wet conditions across Scotland as the main moisture plume feeding in out of the NW across NI, S Scotland and N England lifts north tonight as the low pushes into the North Sea, more wet weather piles in Sunday. However, Saturday sees heights rise over the S of England through Saturday allow sunnier skies and temps back towards 20C.
Following the mere 24-hour rest from the wet in the South Saturday, we see another swirl of cloud move in hot on the heels of the current system during Sunday renewing persistent rains for the South while it keeps the peristent unsettled weather further north with no real drying out period for days on end. That means from the north Midlands to Central Scotland, the flood threat remains.
It appears once the Sunday system clears with the same path as the current system we should then see gradual improvement Monday and Tuesday with the GFS surface pressure chart showing high pressure working in. Interestingly the ECMWF upper chart shows height rises stemming from Iberia Tuesday onwards and this along with surface high pressure suggests the possibility of warmer, drier and sunnier weather on the way by Tuesday through perhaps Thursday or Friday.
Following the passing of a low on Tuesday, surface high pressure builds into the UK on the backside (Map courtesy of MeteoGroup)
A strong upper ridge builds over Iberia this weekend and with a trough and low developing to the west of Ireland, this helps draw ridging north into the UK by Tuesday onwards (Map courtesy of the ECMWF)
As you can see from both charts above (GFS surface chart above, ECMWF upper chart below), a little fly in the ointment (surface low) which may bring some unsettled weather, mainly in the South should clear later Tuesday allowing high pressure to build in at the surface, the ECM shows Europe’s heat reservoir leaving eastern Europe, pushing south and focusing across the Mediteranean Basin. With troughiness working into the very areas which have seen the hottest weather compared to normal in the past 4-6 weeks, the strongest heights back west to Iberia where a heat wave will develop this weekend. Yes, it’s hot throughout the basin as per usual at this time of year but the trough digging into the SE is key with heights rising over the western basin. With a ridge building with height/thickness values rising (meaning the air in the mid and upper levels is warming) over Spain and Portugal this is something we should watch closely. The model has shown this for a week now and hasn’t budged.
The key for the UK is does this ridge build and expand or simply build over the Southwest of Europe. The current model has for a few days shown enough of a northward extention that we could see at least mid-20s C back into the South if not Midlands of England mid next week with low 20s C returning to Scotland. The current run would support mid to perhaps even upper 20s C by Wednesday through Friday in the South, mid-20s C for Scotland.
What’s key for a return to summer here in the UK and Ireland is 1) the focus of hottest weather taking aim at Spain, 2) the trough developing a low to the west of Ireland and holding off before migrating east and 3) the eastward departure of the Tuesday feature which could bring a 3rd spell of wet weather from now till Tues to the UK. Rather than the trough sliding east, it builds in place, developing a well organised low by Tuesday, this would help naturally raise heights over the UK and act like a wheel drawing the super hot air over Spain, northwards. Thursday sees the wheel to our west (the low), pushing across the UK bringing our next substantial blast of wind and rain. Both the GFS and ECMWF show this low crossing us next weekend but it’s between this weekend and next which could be interesting with a 2-3 day return to summer.
The two charts below show the low growing and intensifying west of Ireland, this will help pump the Spanish heat up over the UK, allowing for a 2-3 day warm spell before it finally crosses us by Friday and next weekend.
(Courtesy of the ECMWF)
(Courtesy of the ECMWF)
(Courtesy of the ECMWF)
Keep in mind what I’ve been talking to you about now since my summer review back about a week to 10 days ago, given the wet spring and the persistency in the negative NAO, the long term pattern now highly favours a wetter, cooler summer but there will be short lived warm spells. Next week looks to be a perfect example with 1-2 weeks of cool and unsettled verses 2-4 DAYS of warmth.
Only a strong and sustained surge into a positive NAO would we see a prolonged spell of warmth and unfortunately the now extremely wet soils across the UK will have a negative feedback to the atmosphere, favouring lower heights than if we had dry soils. The return of the el nino has likely played a bigger role than many think this spring. Could also play a big role in next winter.
Hope to have some initial thoughts on the upcoming winter in coming days!
Nice write up Mark. A few days respite from the rain will be nice.
Very interested to hear ur thoughts on this winter, it’s not that far away really !