Summer 2016 - Outlook not so good

[iapennell]

2nd May 2016

Following my mixed successes (although in some regions of Scotland my spring forecasts have proved a little wide of the mark) I am making a provisional outlook for Summer 2016 for the United Kingdom. It is based on sound meteorological principles and the influence of sea-surface temperatures, sea-ice anomalies and the Northern Hemisphere snow-cover extent observed in March this year.

The El-Nino in the equatorial Pacific seems to have ended recently with sea-surface temperatures actually falling below normal off the coasts of Peru and Ecuador.  However temperaures in the tropical North Atlantic and tropical North Pacific are (on average) 1C warmer than normal for the stat of May whilst the Indian Ocean just north of the Equator is up to 2C warmer than normal. This is likely to support a strong Intertropical Convergence Zone (ITCZ) going into summer which will sustain NE Trade Winds stronger than normal. Also supportive of stronger-than-usual NE Trade Winds is the fact that most of the North Pacific between 30 and 45N is significantly colder than normal for the start of May with the cold anomaly reaching 2C in places. It is a similar story in the NE Atlantic north of 40N with cooler than normal waters.  Cooler than normal waters in the subtropical/low mid-latitude oceans means that the subtropical high-pressure belt will be stronger than normal and so NE Trade Winds on the southern flank will be correspondingly stronger. Other factors, however, such as the fact that snow-cover during March 2016 was some 3 million square kilometres less than normal over North America and Eurasia means that these vast continents will warm up faster with less snow-cover to reflect the sun's heat going into summer. This in turn means less cool air filtering into the subtropics of these continents, southern Asia and the southern USA/Mexico will heat up faster  with the result being that the subtropical high will weaken sooner in the season and weaken further. This will weaken the NE Trade Winds further south. On the whole, the overall impact is going to be of stronger NE Trade Winds covering a slightly larger geographical area than normal for the season leading to a bigger-than-normal demand for higher-latitude Westerlies to satisfy Conservation of Angular Momentum laws.

The hotter-than-usual tropical waters just north of the Equator will trigger more hurricanes and typhoons in the North Atlantic and Pacific respectively. These tend to move westwards along the ITCZ once the ITCZ is well north of the Equator with the very strong easterlies associated with them feeding into the Northern Hemisphere circulation whilst the very strong westerlies to the south of such storms feed into the Southern Hemisphere circulation. For angular momentum considerations vis-a-vis the Northern Hemisphere circulation this means stronger Westerlies in higher latitudes. However, the hurricanes are not likely to get going until the ITCZ is well north of the Equator over the oceans- that is not likely before July.

This paints a picture of stronger Westerlies reaching Britain bringing cool unsettled conditions off the North Atlantic during the summer.  However, other factors will influence the position of ridges and troughs associated with the Circumpolar Vortex of very strong Westerlies in the upper air. The position of the upper Westerlies will be influenced (overall) by the extent of sea-ice which (during April) has retreated north of 70N in the Eurasian sector of the Arctic whilst in the North American Arctic Hudson Bay is still frozen and there is still ice in the Davis Strait. The Baring Strait has just thawed out, however and waters off the southern coast of Alaska and western Canada are over 2C warmer than normal at the start of May. Sea-surface temperatures in the NE Atlantic to the west of Britain are 1 to 2C colder than normal and the North Sea is (at the time of writing) also colder than usual but the NW Atlantic south of Greenland is now warmer than usual.

The Circumpolar Vortex ridges over and just downwind of areas of warm water where sea-ice is retreated well to the north but upper troughs occur over and slightly downwind of cold seas where sea-ice extent comes south.  It is well-known that topographical locking of the jet-stream to the North American Rockies occurs (where an upper ridge often forms) and there is no reason why this will not happen over the coming months. On the whole, angular momentum considerations suggest that the upper (and lower) higher-latitude Westerlies will be a bit stronger than usual so I envisage that a four-wave pattern of upper ridges and troughs will occur through much of the summer, at least until around mid-July. A ridge is likely to occur over the Rockies (helped by warmer-than-usual water south of Alaska) but slow-to-warm Hudson Bay will encourage an upper trough over that region. Further east slightly warmer-than-usual waters south of Greenland will cause the upper Westerlies to re-curve a bit further north than usual so there may be more cyclonic activity over the NW Atlantic but with higher pressure further south and east. Colder waters over the NE Atlantic will cause the upper Westerlies to re-curve southwards and an upper trough would tend to occur over NW Europe. However, a caveat: sea-ice is retreated well to the north of its normal position in the European Arctic at the time of writing and sea-surface temperatures are above normal in the northern Norwegian and Barents seas.

This distribution of sea-surface temperature anomalies and sea-ice extent could cause the upper Westerlies to split in the vicinity of western Europe with a northern section of the upper Westerlies carrying depressions north of Scandinavia to be re-invigorated by warmer-then-normal waters there and to follow the margins of the ice whilst a southern branch of Westerlies follows an intensified temperature gradient between the cold NE Atlantic and the rapidly-heating Med/continental Europe with depressions and bad weather affecting central Europe as a result. In between and away from these branches of the jet-stream the still cool waters around the United Kingdom could encourage high-pressure and a run of hot sunny days (not excessive heat owing to the tempering influence of relatively cool coastal waters).

 

CONTINUED BELOW 

Edited May 2, 2016 by Paul
Removed all caps title.

[iapennell]

CONTINUED

On the whole, however the Circumpolar Vortex is likely to be too strong to enable the jet-stream to split like this, but I do think that high-pressure will come in following the passage of fronts from the north-west and- at times- disrupt the upper westerlies to the extent that depressions are forced well to the north (and south-eastwards into Europe) so that some hot sunny weather is possible.

So for June and the first half of July the cool waters over and west of Britain will mean high-pressure will frequently be to the south-west whilst the upper trough guides depressions from southern Greenland/Iceland south-eastwards to southern Norway, Denmark and the North Sea. Thus the prevailing weather will be cool and showery with fresh west and NW winds on most days. The south and south-west of England will often escape showers and here there will be more in the way of warm sunny days with typical maxima of 20 to 22C but northern England and Scotland will be cooler with maxima of 16 to 18C being typical along with some sharp showers with hail and thunder possible. Clear skies will, nonetheless, be common at night in the cool sub-polar airstreams and minima in lowland locations will widely fall below 10C even in the South.

Colder Arctic air is likely to reach Scotland and northern England a couple of times during June as a deeper depression pushes towards Denmark with a stronger ridge of high-pressure west of Britain on occasion: On such occasions maxima around 12C across the lowlands of the North will occur and snow will fall on the Scottish mountains above 600 metres' elevation. With the clear night following as the ridge moves in from the west air temperatures will fall close to freezing point across Scotland and the North and ground-frost will be widespread. Yes, I am fairly confident of this happening at least twice during June, gardeners you have been warned! I am also confident that the south is likely to escape such cold although even in Devon minima as low as 6C could well occur.

As the waters well north of Britain continue to warm and high-pressure to the south-west means the strong summer Sun warms the cool NE Atlantic waters the focus of the troughing and depressions will shift eastwards, it is during late June into July that a measure of "splitting" of the jet-stream will occur with some cyclonic activity carried well north of Scandinavia into the Arctic. Meanwhile the seas around Britain will still be cooler than normal given the weather likely to have occurred up to that point and at this time these cooler waters will encourage some anticyclonic curvature over the UK as a trough forms further east; this is then when high-pressure is much more likely to become established over the country with the high being centered just to the south-west of Britain. This will bring relief from the cool conditions and showers and the clear skies and strong summer sunshine will lead to temperatures exceeding 27C in the Midlands and southern regions. Further north it will still be quite sunny but a stiff westerly breeze is likely to prevent temperatures exceeding 24C anywhere north of a line from Preston to Middlesbrough. Temperatures will still cool quite quickly at night under clear skies to around 10C, even across southern regions. The high-pressure will retreat south-westwards at times to allow blustery and cooler north-westerlies to bring some showers to Scotland and the far North of England at times. This fine spell is likely to last ten days to a fortnight which takes us up to developments from mid-July onwards.

From mid-July onwards hurricanes and typhoons in the tropical Atlantic and Pacific will substantially alter the balance vis-a-vis the Angular Momentum budget: At the same time the strong summer sunshine will warm the subtropical waters of the North Atlantic and North Pacific but barring a miracle these waters will still be cooler than normal by late July. Thus the NE trade Winds will still be stronger than normal along the southern flanks which, combined with the 2016 Hurricane/Typhoon season getting into full swing means there will still be a need for stronger Westerlies in higher latitudes to satisfy angular momentum laws. However the configuration of those higher-latitude Westerlies is liable to be different. The waters off the Canadian Arctic are likely to warm fairly rapidly as warm air off the North American continent assists with the melting of ice in then warming the waters of Hudson Bay: This will diminish the amplitude of the upper trough over and downwind of eastern Canada, further east and north the sea-ice extent will retreat to north of Spitzbergen with the entire area of sea east of Greenland and south of 70N becoming ice free.  The Norwegian Sea will continue to warm as the summer progresses and this development is likely to assist a northwards shift in the Circumpolar Vortex accordingly. It is entirely probable that, encouraged by the northwards shift of the jet-stream and the need for stronger low-level Westerlies in higher latitudes to satisfy Angular Momentum laws (this "need" is magnified as the Westerlies shift northwards and closer to the axis of the Earth's rotation) the Circumpolar Vortex will revert to a three-wave pattern from mid-July onwards; a weak ridge will be anchored to the Rockies, a trough over Newfoundland and a weak ridge to the north of Britain. The cool seas around Britain would encourage high-pressure to build- particularly to the south-west where cooler seas would encourage some anticyclonic curvature to the upper winds. However, let us not forget the upper Westerlies, whilst shifted well to the north of Britain, will also be significantly stronger than normal from late-July onwards. This has big implications for the likely weather during the second half of the summer.

CONTINUED BELOW 

   

Edited May 2, 2016 by iapennell

[MP-R]

Doesn't sound too rosy; can't think of an analogue for a summer like that either, not in my lifetime anyway. So it sounds like the first half of the summer we're going to want to see the Azores high move in as much as possible given its position to the SW of us, and the chances of plumes would be higher in the second half of the summer.

If that forecast comes off even close to that, 2016 will be challenging 2015 for the most boring year up to that point.

[iapennell]

CONTINUED:

So late July and August look very much like a North-South divide: For Wales, southern England, the Midlands, Yorkshire, Cheshire and East Anglia high-pressure will be in charge for much of the time though that does not necessarily mean heat because with high-pressure centred to the southwest the wind will often come in from the west and the waters just west of Britain will still (probably) be a little cooler than normal. However, the presence of high-pressure does mean plenty of very warm sunny days and it will get hot from time to time with maxima reaching 28C at times across the Midlands and eastern districts. Elsewhere maxima of 25C will be the best one can hope for. At night under clear skies it will still get quite chilly with minima of 10C occurring widely at times.

Further north across Scotland, Northern Ireland and both North West and North East England stronger cooler westerly winds will prevail and maxima above 20C will be the exception rather than the rule. Patchy cloud and fresh winds will at least keep temperatures falling too much at night so minima will actually be a little higher than in the South, typical values being 11 to 12C late July into August. However the odd colder night associated with a ridge of high-pressure and light winds cannot be ruled out. For Scotland and northern England the stiff cool Westerlies will bring frontal bands and rain at times with the rain being heaviest in western Scotland and Cumbria (i.e hilly areas facing the prevailing winds).

Even though high-pressure is expected much of the time for late July and August in the South that does not rule out periodic cooler spells caused by a cold front pushing south and eastwards in the westerly flow to bring sharp showers, possibly with hail and thunder, as the cold front pushes heated daytime air ahead of it upwards triggering serious atmospheric instability. There will still be several days during this drier and warmer second half of the summer during which gusty winds and sharp showers interrupt the sunshine and heat and daytime temperatures struggle to exceed 20C.

As August progresses the beginning of seasonal cooling in the Arctic will strengthen the baroclinic gradients driving sub-arctic depressions and the Hurricane Season reaching its apex will increase further the need for stronger Westerlies in higher latitudes. During the second half of August some deeper depressions with centres below 980 mb will pass near Iceland and the first gales will hit the far north-west of Scotland with heavy rain. Strong westerly winds with substantial rainfall will also extend further south across the rest of Scotland and much of northern England associated with daytime temperatures in the lowlands below 18C anywhere north of Manchester.

So my prognosis is of a cool start to the summer with better conditions in July and August: My CET predictions- 13.5C in June, 17.0C in July and 17.0C in August; in lowland Scotland 11.0C in June, 15.0C in July and 14.5C in August. Southern England and South Wales will, on balance have near-normal temperatures for the three summer months with drier than normal conditions (particularly for the far south and south-west of England where rainfall is likely to be less than 70% of normal total). The Midlands will also have near-normal temperatures with rainfall close to normal, rainfall will also be close to normal in Yorkshire but mean temperatures will be fractionally colder than normal for the season as a whole. All Scotland along with North West and North East England will have a summer colder and overall 0 to 25% wetter than normal with the coldest conditions (where mean temperatures will be over 1C colder than normal) reserved for northern Scotland. Western regions of Scotland and west Cumbria will also have upwards of 30% more rain than normal for the summer season. Timings of the wettest conditions in the North will vary depending on where you are, it will be wettest in northern and eastern Scotland along with North East England and coastal Yorkshire in June in association with depressions in the North Sea and chilly north or NW winds; for Cumbria, Lancashire and west/north-west Scotland the wettest conditions will be from late July onwards (more so August) in association with stiff westerlies bringing fronts off the North Atlantic.

This is my prediction for the summer, barring any really unusual interruptions like the Yellowstone super-volcano erupting or nuclear war. Please remember, than in summer when the jet-stream and upper westerlies are relatively weak, a major weather event such as a deep depression in the North Atlantic (or maybe a Spanish Plume) can itself totally alter the path of the jet-stream and bring about radically different weather to that predicted, at least for a time. With these caveats in mind, and based on my understanding of the fundamentals of meteorology, the above-forecast is the one I am most certain will happen.   

[iapennell]

http://www.theweatheroutlook.com/twoother/twocontent.aspx?type=hpnews&id=3203&title=Summer+2016+update+4

This fourth summer outlook from Matt Hugo is a strikingly close agreement to my predictions for the South and Midlands,  though I assert that the better weather will come July and August. For the North there is probably closer agreement to Matt Hugo's earlier forecast for Summer 2016.

[cheese]

June can be a write off for all I care - as long as July and August are decent. Hopefully, being a bit further south, it wouldn't end up too bad here, based on your forecast. Summer 2015 was slightly cooler than average but June and August were both quite nice with a rubbish July sandwiched between them.

Edited May 3, 2016 by cheese

[Methuselah]

Well, after 50+ years of 'it'll be a scorcher' or 'it'll be the start of the next glacial period' I think I'll just wait and see?

[iapennell]

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjMm9fD0sXMAhWFBcAKHajEAVgQqQIIJTAA&url=http%3A%2F%2Fwww.express.co.uk%2Fnews%2Fweather%2F667492%2FSummer-weather-forecast-UK-long-range-hottest-summer-sunshine&usg=AFQjCNGDXPoh79Lf_iUUWO_UkOWtQGvENQ

Take THIS sensationalism with a pinch of salt! Whilst I expect July and August to be warmer and drier than normal in the South and Midlands I do not think this will apply to Scotland and I do not think June will be warmer than usual anywhere. However, the South West will be closest to predicted high-pressure in June and will be drier than normal, I expect Scotland and the North East to have a wetter-than-normal June as well as a colder one.

[wishingforsnow]

Well based on that forecast I'd say another North South split could be on the card regarding frequency of settled v unsettled weather so encouragingly it may turn out good for my location  And Matt Hugo's latest updates becoming gradually more positive towards the upcoming summer as the season draws closer regarding high pressure being more influential and not to expect a season like 2012 is encouraging to see for Summer 2016 even if it may not provide spectacular UK wide 2003 style warmth. 

[Matthew.]

I was impressed by your late April cold snap Iapennell. It will be interesting to see if your 10.6c estimate for May comes near the mark also. The North/South weather patterns are giving some changes to the usual West to east patterns. I hope your wrong about June though.

[northwestsnow]

On 5/3/2016 at 22:13, iapennell said:

http://www.theweatheroutlook.com/twoother/twocontent.aspx?type=hpnews&id=3203&title=Summer+2016+update+4

This fourth summer outlook from Matt Hugo is a strikingly close agreement to my predictions for the South and Midlands,  though I assert that the better weather will come July and August. For the North there is probably closer agreement to Matt Hugo's earlier forecast for Summer 2016.

But matt is suggesting a decent June, which is in contrast to your thoughts ian? Anyway, lots of water under the bridge prior to June.Lets see how it pans out , thanks for your forecasts Ian, they are appreciated.

Edited May 10, 2016 by northwestsnow

[draztik]

Thank you Ian for another thoroughly detailed forecast based on your understanding - which, based on previous forecasts, seems pretty sound to say the least! Your knowledge and analysis is very much appreciated. Thanks for sharing.  

[iapennell]

In the light of recent changes in sea-surface temperatures and a patch of cooler than normal water in the tropical Atlantic off West Africa and also the fact that the North Sea is colder than normal at the present time (much of the North Atlantic remains colder than normal but parts of the NW Atlantic just off the US Coast are now very warm) I will update my prediction for June. 

With the European Models now also suggesting fine weather going into June and the changes in patterns of sea-surface temperatures I expect the overall strength of the Westerlies to be diminished despite cool conditions in the subtropical Pacific and lower mid-latitudes of the North Atlantic adding strength to the NE Trade Winds (and through the angular momentum budget to stronger Westerlies at higher latitudes).  The cool tropical Atlantic off West Africa is not conducive to hurricanes forming this side of July and without the strong easterlies on their northern flanks which also affect the Northern Hemisphere momentum budget that means weaker Westerlies. The pattern of sea-surface temperature around and West of Britain, compared with earlier, pulls the troughing of the upper Westerlies further east than anticipated earlier, particularly that cool conditions have been re-established over Scandinavia and the Baltic. 

The upshot is that cyclonic activity will affect Scandinavia and Northern mainland Europe more during June whilst the upper winds will have anticyclonic curvature in the NE Atlantic and closer to Britain than anticipated earlier. I expect June to be dominated by high-pressure ridgeing from a well-established Azores High but with high-pressure mainly ridgeing to the west of the country.

There will be much more in the way of dry warm weather across the South, the Midlands, Wales and Northern England during June. There will even be hot weather at times as the high-pressure is likely to push right in at least once to bring strong sunshine from cloudless skies for four or more consecutive days. With more heat from the Sun than radiated away at this time of year that will quickly result in high temperatures ; particularly inland. However the main position of the high-pressure most of the time means prevailing winds from west or north-west so it will still be quite cool at times and there will be some chilly nights. 

For Scotland I still expect June to be a little on the cool side because of the prevailing winds from the west off a chilly North Atlantic. The north and east of Scotland is also likely to be wet and cold at times because of low-pressure over Scandinavia bringing showery northerlies. However there will be more in the way of dry warm weather than thought earlier.

There will be some showers and cooler conditions for England and Wales when the Azores High retreats to allow North Atlantic frontal systems to cross the region.

Updated outlook for June :

CET of 14.5C with total rainfall 5 cm but more rain in North Wales and Northern England. 

Scotland mean temperature of 12C for lowlands overall with rainfall slightly below average for Borders, Dumfries and Galloway but wetter than normal for far northern Scotland. 

 

For the remainder of the summer I remain confident that July and August will play out as per my original forecast. 

[Matthew.]

Thankyou for this forecast Ian, I am pleased for a better June. Still 14.6 is nothing special in terms of temperature but if High Pressure is in control and gives many sunny days like April 2015 it could be a very special month and remind us of them lovely hot summers of 76, 95,  03 in terms of sunshine

[northwestsnow]

Thanks for the update Ian

I'm desperate for a nice June as i'm off work for 3 weeks so will be nervously keeping an eye on developments over the next week or two.

Again the 00z GFS this morning seems intent on bringing the azores high into play for the start of the new month - much as your post above implies.

Footy, days in the garden and warmth sound great, i really hope it comes off, the fact that you are now 'on board' with something settled gives me a bit more confidence...

[iapennell]

Matt Hugo's latest update of the summer is encouraging in view of my (revised in mid May) summer forecast, namely high-pressure over SW of Britain with depressions passing to the north of the country with increased vigour later in the Summer. 

I did predict a good deal of warm dry weather for the South and Midlands in June and July but for the far north to average out cooler and a bit wetter than normal overall. I also expected and continue to expect increasingly unsettled conditions going into August. 

This is the update :

http://www.theweatheroutlook.com/twoother/twocontent.aspx?type=hpnews&id=3283&title=Summer+update

[weatherguru14]

Matt Hugo tweeted not looking good for most of July Now..he seems to be all over the shop.. making countlss claims and counter claims.

[knocker]

15 minutes ago, weatherguru14 said:

Matt Hugo tweeted not looking good for most of July Now..he seems to be all over the shop.. making countlss claims and counter claims.

Did he actually that?

 

[weatherguru14]

He may not directly have said it.. But  6   summer updates and most of them different from the last..Just a small bit of advice.. Once your in a hole, stop digging. no one can claim to be an      expert at long range forecasting in the UK..

[cheese]

Matt Hugo's thoughts change whenever the EC32 model changes. There's really no point in bothering. 

[northwestsnow]

Utterly depressed with how things are shaping up, is our climate just one long extended autumn now with the odd week of summer thrown in sep/oct?Thats they way it feels imby..

[markyo]

I do feel sorry for those longing  the heat of summer to appear,clock is ticking and nothing even on the horizon to suggest anything like it, I'd punt that we'll be stuck with this pattern till at least 3rd week in july.Suits me but I'm in the minority I know. Got gut feeling August could produce something more to the majorities liking.

[weatherguru14]

I think alot people want a good summer. Makes the year weatherwise  worth while..The weather in the winter in the UK often is pretty dire.Not pleasing when its blowing a gale and the rain is coming down horizontal . Spring can produce anything..Autumn seems the only realibe season of the year...The thing about our climate though.. the next models when ithey roll again out may not be back as bad as it was this morning..

[weatherguru14]

Anyway dunno why am complaining its a lovely summers day today here ..

[Methuselah]

I really don't see why so many folks are so downbeat...This summer, so far, has been the best one for thunderstorms in years?