The week ahead will most certainly be the best of the year so far with barely a drop of rain over the UK and Ireland, except for some isolated pop-up showers and storms and a small rain chance over NNE Scotland late Wednesday/Thursday. The warmth and sunshine was all over the charts throughout last week and it looks as though the warmth builds throughout this week with a possibility of London reaching 27C by Friday or Saturday.

Aside from the building of warmth, what’s interesting is the delay in the models with the return of wet, windy and cooler weather.

Both the GFS and ECMWF have now delayed any ‘breakdown’ in the settled weather until well into NEXT week and whether that holds true or not, this would fit nicely with my early June idea from way back in mid-May of a more ‘sustained’ or longer duration warm, settled pattern in early June, indicative of the positive NAO. The timing of any Atlantic weather returning is always tough to call but it’s a given that this entire week will be warm and mostly sunny with little in the way of rain. Great for sales of BBQ food, outdoor restaurants and for those hoping to get out into the garden. Not forgetting those holidaying in the UK or Ireland.

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In my previous post I did show you both GFS and ECM with a breakdown scenario for late week but did state that nothing was written in stone and that it would chop and change. In all honesty, while not ruling it out, I would have been more surprised at the quicker breakdown than a delayed one given the NAO index firmly into positive by Friday and this weekend, however the transient nature of the pattern so far, meant that this possibility couldn’t be ignored.

Yes I did state that the breakdown may come sooner than first thought but forecasting the correct timing of any breakdown is practically impossible more than a week out. The models are adjusting to the more ‘sustained’ settled pattern which had always been called for through most of May even when we had unusual cold and snow. I stated that once the positive NAO returns, a more sustained spell of warmer, drier weather was likely.

Since my last write-up, the models are strengthening the upper level ridge and increasing the 850 temperatures by Friday through the weekend with highs potentially reaching 26 or 27C in the South of England, perhaps 24 or 25C in Wales, Scotland, Northern Ireland and the Republic.

Here’s the GFS surface chart

Tuesday

Thursday

Saturday

Notice the low off NE Scotland showing it’s hand Thursday, that feature remains a ‘fly in the ointment’ and may bring a brief blip to parts of Scotland but I believe it will have little effect on England and Wales and the only effect we may find further south is a slight temperature drop although heights should intensify right across the UK and Ireland towards late week.

Here’s the ECMWF upper chart/850mb temps

Tuesday

Thursday

Saturday

ECMWF Takes Warm, Settled Conditions Well Into Next Week!!

Sunday

Wednesday

It’s tough to say whether this warm, settled period lasts way out to mid next week but it’s certainly a huge improvement to last year as most of the warm, sunny weather was more confined to the South.

Always remember that we live in the UK and our warm, sunny weather only lasts so long. While I stand by my original forecast of a warmer, drier summer. There will be breakdowns with a return to cool, wet weather but unlike the persistent rain and cool of last summer, bar several days here and there.. this year should hopefully see some decent spells of warmth and sunshine and I am hopeful of relatively shortlived breakdowns.

Soil To Atmosphere Feedback

Soil moisture is very important when it comes to summer temperatures. The wetter the soils, the more moisture is added to the atmosphere as sunshine, angle and energy increases. For example, at this time last spring, there was a heck of a lot of flooding. It rained heavy so often that the ground never got a chance to dry out and so anytime we got decent sunshine, moisture would be released into the atmosphere and so a lot of energy from the sun went into evaporation rather than going into directly heating the ground and then air.

This next week to 10 days with decent sunshine should help dry out any soaked ground from recent heavy rains and that means that despite an eventual break down, the stage may be set for another warmer, drier and more importantly, SUSTAINED period of warm, settled weather.

Here is the latest NAO ensemble.

As you can see, the ensemble is in excellent agreement that we see a plunge back into negative sooner rather than later and so a breakdown WILL come. Note the possibility of a return to positive during the second half of the month. The soil moisture could determine the level and duration of heat within the next warm surge and return to positive in the NAO.

Not only does copious amounts of spring rains affect air temperature but it affects atmospheric pressure. Wet soils encourage more rain, an increase in cloud cover and ultimately lower pressure. Drier than normal soils encourage sunnier skies, warmer air temperatures and higher pressure. There is a strong feedback between soil and atmosphere (less moisture in soils makes the air drier and drier air means it heats faster).

Another important aspect to consider is that the warmer the air, the faster the evaporation rate and soils loose moisture. A week of warmth and sunshine in June will have greater impact than a warm, dry week in April or even May and this CAN have influence on our weather pattern into the heart of summer.

Does a warm, dry spell in early June deffinately mean a hotter July? No, but it may help pave the way to a better month with an increased possibility of higher pressure, more in the way of sunshine and if soils aren’t overly wet, warmer temperatures too.

The warm AMO supports wetter summers here in the UK and Ireland and while the trend since 2006 has been for wetter and therefore cooler, it doesn’t mean we cannot get breaks within a multiyear cycle.

Within a period of colder, snowier winters, like we saw back in the mid to late 70s, not every winter was cold. There may have been 1 out of 3 or 4 winters which was mild. We are in a cycle of much wetter summers and a lot of that has to do with the warm AMO and cold PDO but within that cycle, there are breaks and this summer may be one of those breaks. Last spring we saw the onset of a weak El Nino on the back of two straight LA Nina years. I believe the flood gates opened last April because of the onset of the El Nino after a prolonged dry spell induced by the La Nina. This spring, while we’ve seen heavy rain at times, the soils aren’t saturated and so they have the ability to dry out. The ENSO index this year is neutral, neither an El Nino or La Nina.

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