When you look back at past UK and West Europe summer’s with a warmer, drier than normal June-July, you often get a break in August with turn to cooler and wetter but September’s tend to revert back to the pattern that was before. That’s the case this year, strikingly similar to last year with a warm, dry June-July with cooler, wetter August then back to warmer, drier in September. This may or not be the driest on record because last year, some areas experienced their driest Sept on record.

You also tend to find that you get another surge of true summer heat before the pattern does breakdown proper. The next 24 hours will see that heat surge which could send highs towards 27C around London or the suburbs tomorrow.

Blame or thank that Azores low that’s been a permanent feature of the last 2 weeks as it draws heat out of North Africa.

Note this jet stream or 2-300mb mean winds which dive underneath the low, crosses N Africa and then turns and speeds due NE into SE England. This should enhance sinking as well as draw hot air from a hot source. Temperatures in recent days have topped 45C in Algeria.

The surface chart also shows how the warm air is getting pulled in from the SE thanks the Azores low acting as a wheel.

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The WRF-NMM model shows 27C west of London and a broad area of 26C. Quite believable.

Tomorrow (Wed)

Thursday, which should be warmest!

GFS is warm but slightly more conservative than WRF, perhaps too much up in western Scotland and Northern Ireland where 22 or even 23C is plausible.

Plenty of heat across much of Europe.

According to both GFS and ECMWF, before heights build with the presence of Edouard coming up from the south, it becomes ‘unsettled’ but let’s just wait and see because both models thought today and tomorrow would be rather unsettled and that’s not happened. The models are underestimating the strength of the ridge, weakening and kicking it out too quick.

The height rise into the weekend and early next week is seen best in the 500mb anomaly.

 

It’s interesting when looking at the NAO index that’s it’s flipped from lowest negative since 2010 to the strongest positive probably of the entire year, hence the flip from cold August to warm September.

The 500mb height animation shows that crucial flip over Greenland! It only takes a former tropical cyclone and it’s surge of heat into the temperate regions for a large-scale readjustment of the upper height field.

Once the arctic begins cooling, we start to see changes further south and so a flip should come within the next 6 weeks. I suspect a wetter theme into October given the warm surrounding waters and El Nino coming on. How wet? Well right now I can only say that I suspect a wetter than normal pattern mid-Oct till possibly mid Dec. My theory is, that IF we get a winter resembling 09-10/10-11 then where the summer ridge is, that’s where the wettest weather (compared to normal) is during late autumn and then that’s where the cold trough goes for winter.

One could fear that the similar pattern to last year could lead to a similar winter. That’s possible but there are differences which should shift things late autumn into winter as the QBO is easterly, the solar cycle is heading down, not up and we’ve got an El Nino. These drivers should all point to a different kind of winter in 2014-15 but I would be foolish right now to suggest that a severe winter is coming.

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