Prediction for Autumn 2016

[iapennell]

They say that a Week Is A Long Time In Politics; the same seems to be true in the prospects for the Autumn 2016 with regards to the general circulation and (thus) the sort of weather we can expect in this country: The "Cold Blob" in the North Atlantic has gone entirely and sea-surface temperatures are now well above normal for early September from the North American coast to Europe and cooler-than-normal water off the coast of Norway has also gone. Worthy of note however is that sea-surface temperature anomalies of 6C or warmer are present in the Greenland Sea and there are unusually large openings in the Arctic pack-ice just a couple of hundred miles into the far side of the North Pole (from Britain).

There has also been a sharp up-tick in hurricane activity in the tropical North Atlantic and ex-hurricane Gaston is making its presence felt. The Quasi Biennial Oscillation of wind-anomalies at the 30 mb level in the Equatorial Stratosphere is currently of winds from the West exceeding 10 metres per second.

All of this points to a wetter but milder picture for the autumn- particularly from early October onwards and particularly for Cumbria, Northern Ireland and Scotland where there will be an increased propensity for gales. However, it looks like storm tracks will remain well north of Britain this month, following the northwards position of the main baroclinic zones compared to normal. I therefore remain confident that there will be much dry and warm weather across England and Wales during September, though western Scotland is increasingly likely to be characterised by spells of rain and strong south-westerly winds and somewhat cooler temperatures as we get closer to October.

As a consequence of the change in the pattern of (and the nature of) the sea-surface temperature anomalies around and (particularly) to the west of Britain I downplay the probability of a chilly dry spell with easterly winds bringing air frosts at night in October. The south and east of England is certainly likely to be drier than normal until mid-October owing to the probable wind and surface-pressure patterns (i.e. high-pressure over Europe and deep depressions in the vicinity of Iceland) but it will be warm due to the (likely) southerly component of prevailing winds and I am not (therefore) expecting an air frost for most locations until November.

[iapennell]

On 8/21/2016 at 17:31, Gael_Force said:

Thanks for replies, Ian. Your links are new for me but interesting to see the divergence being talked about in the 30 and 50mb graph. Whether this unusual departure has any bearing for the weather on the ground, we'll see in due course.

Can I refer folk to the interesting article that has appeared in The Times today about the Quasi Biennial Oscillation (for those of you with a Times subscription typing into the search bar "Winds of Change", "Mild Wet and Stormy" should bring it up). If indeed the QBO has been disrupted and we have the QBO remaining in a westerly phase this coming season it means that this Autumn will be unsettled and wet (but mild) from about mid-October onwards, particularly for the northern half of Britain. Looking further ahead it now means we have a high chance of Winter 2016-17 turning out wet windy and mild (with little in the way of frost or lowland snow), much as has been the case over the last few winters.

Rest assured, for those of us living in England and Wales (with the probable exception of Cumbria), I continue to expect September and early October to be markedly drier and sunnier than usual with temperatures above normal by day. There may well be some chilly clear nights but with winds likely to be south-westerly for the duration don't expect frosts!  The longer-term weather charts seem to be backing up this assertion. See this link:

http://www.weathercharts.org/wetterzentrale-t120-t384.htm

Edited September 9, 2016 by iapennell

[iapennell]

My apologies, the article in The Times today (9th Sept) that I referred to above is actually titled "Weird winds of change mean mild, wet and stormy" and it is on page 11. Apologies those of you with a subscription to The Times if you were looking for said-article on the search terms that I indicated above and you did not find it! 

[lorenzo]

There are a couple of QBO charts that should without much examination explain the predicament...

[iapennell]

Longer term outlook through to October has high-pressure (often) close to the South and Midlands with some more unsettled conditions at times for Scotland judging by the surface-pressure charts for the next 16 days: http://www.weathercharts.org/wetterzentrale-t120-t384.htm

We can thus expect there to be more warm sunny weather for much of England and Wales, but temperatures will not be as high as they have been. Scotland will be more unsettled but even here there will be some fine spells.

September 2016 shaping up broadly as predicted, but much of the month (to date) has been rather warmer than I anticipated across the southern half of the country. Looking ahead, Greenland Sea is up to 6C warmer than the seasonal norm and much of the NE Atlantic is warm. This, along with Arctic Ice near record lows will ensure storm tracks remain well to the north of the county for the next month and thus we can expect more dry and warm weather for much of England and Wales (plus some chilly nights, as over the last 48 hours). That is not to say there wont be some rain at times as fronts (associated with depressions far to the north) push south- this we have seen with the thunderstorms locally over the past week.