PREDICTION FOR APRIL AND MAY 2017: WARMER THAN USUAL BUT OFTEN WET IN THE NORTH

[iapennell]

First of all, apologies for not getting the complete Spring 2017 forecast out in time. I was on holiday in Churchill (Canada) with my brother in late February, then when I got back I had exams to study for. I was also beset with sickness for much of March so little time to get onto the Netweather Forum let alone make seasonal forecasts! I will rectify my shortcomings by producing a forecast for the next two months, but I will not be tempting providence by producing a Summer 2017 prediction before the middle of May. In the summer half-year the Circumpolar Vortex is weak and regional variations in sea-surface temperatures provide the better hope of making a prediction for the season. Even that can get blown off course by a deep depression pushing into Scandinavia or a "Spanish Plume" that drastically alters local temperature and pressure patterns which can flip the upper-level Rossby waves into a completely different configuration that could prove to invalidate earlier predictions of the season. With these provisos in mind I will provide details of the weather that we can expect in April and May this year:

A number of important controls still look like they will shape the weather we get in the UK over the next couple of months. Firstly, sea-surface temperatures are some 2 to 3C warmer than usual around the United Kingdom but the North Atlantic south-west of Iceland is some 2C colder than usual and waters off Newfoundland are up to 3C colder than usual. Much of the north Pacific is also chillier than normal for the start of April but further north the Arctic waters are warmer than usual and the same is true of sea-surface temperatures in the Barents Sea (north of Norway) where sea-surface temperatures are 3 to 4C warmer than usual. Arctic sea-ice, as you may be aware, has started to recede from it's lowest maximum extent on record- particularly in the European Arctic sector and in the Bering Sea. Sea-ice extent, however, is close to normal early April extent off eastern Canada and in the Davis Strait between northern Canada and Greenland. This means that the Circumpolar Vortex would, other things being equal, travel a little closer to the Arctic than normal whilst an upper trough will form (more often than not) a little downwind (i.e. to the east) of the anomalously cold surface waters in the mid North Atlantic with the upper flow re-curving northwards as it reaches north-west Europe. This suggests high pressure over Europe but with deeper depressions than normal moving north-eastwards between Scotland and Iceland. This would suggest a warmer than normal April and May but with frequent spells of wet cooler conditions for Scotland, Northern Ireland and North West England.

However, there remain global macro-scale controls that could mean the emphasis is going to be more on wet and breezy rather than warm: The Quasi Biennial Oscillation (QBO) is a wind-pattern high up in the Equatorial Stratosphere over 15 miles above sea-level and it has been blowing at record-breaking speeds from the west (at 34 mph on average at the 30 mb level and over 20 mph at the 50 mb level) and this has ramifications for the weather-patterns in higher latitudes. The excess west-to-east momentum of this vast river of air eventually descends and it enters the global tropospheric circulation within a couple of months- within a further few weeks this excess westerly atmospheric angular momentum (AAM) finds its way into mid-latitudes (of both the Southern and Northern Hemispheres). It is the excess westerly AAM transferred into the Northern Hemisphere that we are interested in and unless of course it encounters the Himalayas and Rockies first this will eventually feed into stronger (and more extensive) westerly winds at higher latitudes. The Himalayas and the Rocky Mountains will intercept some of this excess westerly atmospheric angular momentum but by no means a substantial portion of it (let alone all of it) because during the spring lower latitude continents and oceans warm up along with the Eurasian and North American landmasses: Hence strong upper westerlies associated with the subtropical and polar-front jet-streams are pushed to slightly higher elevations in the subtropics and to higher latitudes over mid-latitudes- less of the westerly AAM is stopped by mountain ranges before reaching higher northern latitudes as a result. This can only mean one thing- stronger westerly winds associated with deeper depressions bringing more rain!! Upper-air forecasts hint at a weakening (even a reversal) of westerlies at 60N over the Stratosphere going through to mid April and there are hints that this could result in a cold snap with northerly winds mid-month as high-pressure builds over Greenland. However, it must be remembered that in summer the stratospheric winds over the Arctic and sub-arctic are usually easterly- but clearly Britain still gets wet and unsettled weather then!

A strongly westerly QBO does not portend lots of dry fine spring weather in higher northern latitudes and though the hope must be that with sea-surface temperatures around Britain warmer than usual the excessive storms are guided north of the country: However, the large patch of icy water in the mid-north Atlantic will encourage the jet-stream to swing south over and east of there. That means there are likely to be depressions heading towards Britain- and given the effects of the record westerly QBO these depressions will be stronger than normal for the season. Furthermore the south-westerlies associated with these depressions will blow on their southern flank over warmer-than-usual waters just north-west of Britain and they will pick up moisture. I would be inclined, on the strength of these factors alone, to assert that north-west Scotland will have a rather changeable May at best and there will be plenty of rain.

Another important factor are developments in the equatorial Pacific Ocean: Sea-surface temperatures for the time of year are 1 to 2C above normal off the coast of Ecuador and these positive temperature anomalies push west towards the central Pacific: This suggests ENSO-neutral bordering on El-Nino conditions which, if anything, will tend to strengthen the upper westerlies associated with the sub-tropical jet-stream over the northern Pacific. This, through a dynamical impact on the structure of the upper westerlies over the North Pacific and North America can lead to increased amplitude between the waves and troughs associated with the Circumpolar Vortex. This could result in fine warm weather over Britain if depressions are carried well to the north of the country but, given the temperature-patterns as they are over the North Atlantic is as likely to mean the jet-stream pushes depressions in from the west on a more southerly track- before they turn north up the western side of Scotland. However temperature and pressure patterns across the Equatorial Pacific are only just bordering on El- Nino so it's overall impact on the United Kingdom weather through April and May will remain minimal.

The Sun is also an important influence: Currently the Sun is declining in the extent of it's electromagnetic activity, solar flares and sunspots as we get towards the quiet final stages of the current Sunspot Cycle: An active Sun produces solar flares that (through interaction with the Earth's magnetic field) increase the intensity of winter depressions and attendant westerlies in sub-arctic latitudes. A quiet Sun, by implication, should mean weaker depressions and weaker westerlies in higher latitudes. Also of note is that the Solar Constant has dropped from 1366 Wm^-2 a few years ago to nearer 1361 Wm^-2 today (a fall in solar output of close to 0.4%), it is of course known that the Solar output drops from Sunspot Maximum to Sunspot Minimum but there are indications that the Sun is going unusually quiet even by the standards of past Solar minima. However, this is not the thread to discuss whether changes in the Sun will mean an end to (and reversal of) global warming; though a quiet Sun ought to point towards a drier, cooler spring in Britain the strength of the Westerly QBO Phase and the sea-surface temperature patterns around and well west of Britain are liable (together) to well overcome the effect of a quiet Sun: The season as a whole does not look to be settled for the north and west of the country.

 

(continued below).   

[Mokidugway]

Lol wet in the north , as you where then , never could get my head around synoptic forecasting .

 

[lassie23]

no snow then

[iapennell]

April-May 2017 Prediction:continued....

Firstly April: For this there are the weather charts that give assistance, at least to mid-month. It looks like much of England will benefit from high-pressure systems moving up from the Azores and crossing into Europe early in the month. This will mean that there is a good deal of warm dry weather with temperatures reaching 20C in the most favoured parts of the South East and South Midlands at times, clear periods at night will mean localised frost with minima in most locations likely to fall to or below 5C in most places. Further north, passing fronts associated with North Atlantic depressions will bring rain at times and a fresh south-westerly wind. Any snowfalls are likely to be restricted to the Scottish mountains above about 800 metres, owing to the prevailing south-westerly winds. However, even here high-pressure will nose in from further south at times leading to some warm spring sunshine and maxima reaching 15C oven in places like Aberdeen and Dundee. A fine, but cooler spell is likely around 10th April as high-pressure affects the whole country with light north-easterly winds- night ground-frost is likely to become widespread with air frost probable in Scotland and northern England.

Mid-April looks like bringing a week of colder weather with high-pressure west and north-west of the country and depressions crossing Scandinavia; this will bring colder north or north-westerly winds and this means snow-showers in Scotland and upland parts of northern England. Daytime maxima will be below 10C except in the South and there will be widespread air-frost at night. In parts of Scotland and northern England valleys expect minima of -2C or below during this period.

During late April there are indications that high-pressure over Greenland will hang on, but weaken with high-pressure often south-west of the UK. However, the emphasis will be on increasingly unsettled conditions coming in off the North Atlantic associated with depressions that will brush by north-west Scotland. The sea-surface temperature patterns and the QBO indications lend themselves to this being the more likely outcome. Spells of cold wet weather borne on westerly winds (with snow above 600 metres) will affect Scotland- farmers with lambs beware! These conditions will also affect northern England and Wales at times with snow on the highest ground on occasion and there will be the odd westerly gale affecting the North West and western Scotland. The South of England and South Midlands will escape most of the chill wet weather and here there will be a good deal of sunshine and warmth at times- some fronts from further north will bring rain at times. The only consolation is that night frost will become much more infrequent, even in Scotland, owing to frequent cloud-cover and the prevailing wind-direction being westerly rather than northerly.

April 2017: CET of 9.5C; England and Wales rainfall average total of 90 mm.

Scotland: Average lowland temperature: 7.0C, Average total rainfall of 120 mm.

For May 2017 the general prognosis is not good except in the Midlands and South where there will be a good deal of warm dry weather at times. Starting with the English Midlands, Yorkshire and southern England there will be a good deal of warm dry weather with high-pressure crossing southern and central Europe extending its influence northwards, Prevailing winds will be west or south-westerly so despite clear nights ground-frost will be unlikely except in the most sheltered frost-hollows and the strong May sunshine will regularly raise air-temperatures to 22C or above over a wide area. There is even the likelihood of a hot spell during the second half of the month with winds turning southerly and bringing air up from the Mediterranean for a few days- temperatures across the Midlands and South will widely reach or exceed 26C. However, with the assistance of upper troughs to the west, this hot spell is likely to degenerate to widespread thunderstorms with localised heavy rain and even hail- combined with a sharp drop in temperature to more seasonable levels as the wind veers towards the west.

That said, even in the south there will not be fine weather throughout May as frontal influences push in at times and early May is likely to be distinctly cool and breezy with regular showers. This will be an effect from high-pressure extending north into the mid-North Atlantic and the still-present Greenland High (Greenland itself will be slower to warm up this spring than it might otherwise, record winter snowfalls over the ice-sheet have increased the surface albedo to 85 to 90%). Depressions are more likely to pass closer to the north of Scotland and bring chillier air in its wake at times- with frontal influences pushing further south- as a result. Frost at night will still be unlikely in the South early in May due to breezy conditions, patchy cloud-cover and moist ground though ground-frost may affect frost hollows on the few clear nights following cooler westerlies.

For North West and North East England (excluding Yorkshire), Wales and Scotland conditions will not be so amenable: Early May is likely to be chilly and particularly wet (with snow in the Scottish mountains at times). A good number of days will struggle to reach 10C, even in the lowlands. However, even here there will be some bright and warmer days in between the passage of depressions to the north of Scotland, although clear nights following westerlies will be colder and local frost cannot be ruled out. Wales, however, is likely to be warmer and most places will escape frost worries, although it is still likely to be wet. Westerly gales are likely to affect the far northern coasts of Scotland along with the Hebrides at times early in May.

Later in May the weather will become considerably warmer over the north and west of the country as low-pressure remains more to the north-west of Britain whilst pressure rises in the south: This will result in winds coming in more from the west and south-west and there will be a little less rain as depressions to the north-west become a little weaker heading towards summer. There will, consequently be a good deal of warm, bright days with temperatures reaching 20C in places like Preston and Newcastle on occasion and these conditions will occur between frontal passages. The fronts crossing the more northerly parts of the country in late May will bring heavy showery rain at times, and locally accompanied by hail and thunder. The warmer airstream and shorter nights is likely to put paid to any risk of frost in the North and Scotland during the second half of May. A spell of very warm southerly winds that is likely to happen late in May will bring hot weather to the South of England and also bring a day or two of heat to South Wales (with maxima locally at 25C), but the warm southerlies and the daytime heat and sun associated with it is unlikely to get north of a line from Liverpool to Middlesbrough, this period will be associated with humid south-westerlies with plenty of cloud and patchy rain further north. It is unlikely that anywhere in Cumbria, Northumberland or Scotland will exceed 22C during May owing to the generally unsettled conditions.

For May 2017: CET of 13.0C, England and Wales Rainfall (average total) = 80 mm;

Scotland average temperature (lowlands): 10.5C; Rainfall (average total)= 110 mm 

   

 

[iapennell]

52 minutes ago, lassie23 said:

no snow then

There's quite likely to be snow on the Scottish mountains at times during April and early May. Snow-showers are also likely to occur more widely in Scotland and northern England around the middle of April due to an anticipated spell of Arctic winds!

[lassie23]

48 minutes ago, iapennell said:

There's quite likely to be snow on the Scottish mountains at times during April and early May. Snow-showers are also likely to occur more widely in Scotland and northern England around the middle of April due to an anticipated spell of Arctic winds!

Didn't this happen last April?

[Fourty Point Three Degrees]

That end of May prediction has overtones of May 2012 written onto it. The end of May 2012 was dominated by warm air and Spanish plumes and bringing that awful June along with it. I do hope this June isn't going to be the same.

[Methuselah]

10 hours ago, lassie23 said:

Didn't this happen last April?

And in '75, '89 and '95, I think. So hardly anything unusual for Springtime.

[karyo]

Thank you for your prediction Ian. What are your thoughts on the QBO for the rest of the year? Do you see it weakening or even turning easterly?

Sorry for deviating from your thread but spring and summer fail to ignite my interest.

[iapennell]

4 hours ago, karyo said:

Thank you for your prediction Ian. What are your thoughts on the QBO for the rest of the year? Do you see it weakening or even turning easterly?

Sorry for deviating from your thread but spring and summer fail to ignite my interest.

@karyo, The QBO typically works it's way downwards through the Equatorial Mesosphere and Stratosphere with time- look above the 30 and 50 mb level (where there are these record-strong Westerlies) to the 10 mb level and above what do you see? There is a zone of quite strong Easterlies blowing at the equivalent of gale-force or stronger at this level and it extends from 30S to 20N. This should slowly work it's way downwards through the Equatorial Stratosphere over the next six months, by which time we would expect easterlies at both the 30 and 50 mb levels. That is, of course, assuming there is not some disturbance to knock the QBO off-course (as happened last year)!

[iapennell]

15 hours ago, lassie23 said:

Didn't this happen last April?

Yes, there was a spell of Arctic winds in mid-April last year that brought four inches of snow to the North Pennines followed by temperatures at night falling to -3C as skies cleared. Then winds often remained from a northerly quarter for the remainder of the month bringing further wintry showers and frost at night. Fortunately that was saved by a warm dry May that made up for lost time. Late April this year is likely to be chilly and wet across the North and Scotland- with snow in the mountains-and (in northern regions at least) it is not going to be compensated for by a warm dry May.

As to how the summer this year will turn out, I would not want to make predictions at this stage. However the current temperature-anomaly pattern across the North Atlantic and the zone of anomalous strong Westerlies high up over the Equator are two factors that I would not want to still be in place in six weeks' time for a warm dry summer across Britain.

However, as I have pointed out, the seasonal weakening of the upper Westerlies during late-spring and into summer (though I am confident it will be stronger than usual for the time of year on the whole) means that regional weather-patterns are at the mercy of alteration as a result of a single storm, a few days' unusual heat over Canada or a late snowfall over Sweden. Some volcano in the Philippines could blow it's top- putting dust in the atmosphere that helps warm the upper-air and cool the surface next month, that would greatly alter the pressure and wind-patterns and render invalid any prediction made currently. We could have some very hot weather during the summer- especially in view of the above-average sea-surface temperatures around our shores- but it really is too early (and too far from the summer season) to make any concrete predictions as yet.

[karyo]

4 hours ago, iapennell said:

@karyo, The QBO typically works it's way downwards through the Equatorial Mesosphere and Stratosphere with time- look above the 30 and 50 mb level (where there are these record-strong Westerlies) to the 10 mb level and above what do you see? There is a zone of quite strong Easterlies blowing at the equivalent of gale-force or stronger at this level and it extends from 30S to 20N. This should slowly work it's way downwards through the Equatorial Stratosphere over the next six months, by which time we would expect easterlies at both the 30 and 50 mb levels. That is, of course, assuming there is not some disturbance to knock the QBO off-course (as happened last year)!

Thank you Ian, hopefully no more disturbances this time.

[damianslaw]

Thanks for this, interesting reading, but for Scotland and Cumbria not particularly appetising, May is my favourite month, indeed April and May on average bring the most settled driest conditions of the year here.. mmm have we been dealt our best cards in Feb and March .. it has been exceptionally benign these past few months so only a matter of time I guess before we a flip back to generally unsettled.

[MP-R]

I'd be more worried if we'd had a settled March like 2011 or 2012 but given the changeable nature of March this year, I'm a little more confident that the weather will be more fluid over the coming months. An unsettled showery may wouldn't be unusual at all, especially given recent years. Other than last year, we've been really struggling with nice Mays. Could do with another one!

[damianslaw]

14 hours ago, MP-R said:

I'd be more worried if we'd had a settled March like 2011 or 2012 but given the changeable nature of March this year, I'm a little more confident that the weather will be more fluid over the coming months. An unsettled showery may wouldn't be unusual at all, especially given recent years. Other than last year, we've been really struggling with nice Mays. Could do with another one!

Yes recent May's bar last year have been rather disappointing, some like 2008 started very well but went downhill mid month, whilst others like 2009 and 2012 were inconsistent with a shortlived very warm summerlike spell - indeed last week of May 2012 was the best weather of the whole season temp wise. A settled fine May beats a settled fine April hands down I say..

[Matthew.]

If Iapennell CET predictions are spot on we will be declaring the warmest spring on record

[Weather-history]

On 01/04/2017 at 23:45, iapennell said:

April 2017: CET of 9.5C; England and Wales rainfall average total of 90 mm.

 

   

 

90mm is really wet for April for England and Wales, that would put it in top 40 wettest Aprils on record. Its been very dry thus far, I think your rainfall prediction is in trouble already. Its going to have to be a really cyclonic spell to catch up now and there is nothing at the moment to suggest this.

Edited April 11, 2017 by Weather-history

[Nick L]

52 minutes ago, Weather-history said:

90mm is really wet for April for England and Wales, that would put it in top 40 wettest Aprils on record. Its been very dry thus far, I think your rainfall prediction is in trouble already. Its going to have to be a really cyclonic spell to catch up now and there is nothing at the moment to suggest this.

Yes, very little sign of any significant rainfall for at least the next 7-10 days across southern Britain. It's already been a very dry month for many.

[iapennell]

http://www.weathercharts.org/wetterzentrale-t120-t384.htm#228

And this too, also for 20th April:

These charts are for nine days' hence (20th April)- it does not look particularly settled anywhere. This sort of weather-pattern could bring quite cold weather as well.

I see no reason to alter my predictions based, not only on the long-term of these weather-charts- but on other such large-scale fundamentals as a record Westerly QBO and the pattern of sea-surface temperatures across the North Atlantic. For sure, when the upper Westerlies that encircle the Arctic weaken in spring they become subject to short-term weather conditions at the surface and that makes them a little unpredictable but my money remains on late April through much of May being unsettled and wet, particularly in the North and Scotland.  

 

[lassie23]

Has that blob in the Atlantic disappeared?

[Methuselah]

3 minutes ago, lassie23 said:

Has that blob in the Atlantic disappeared?

Is that the same blob that did for last summer?

[lassie23]

3 minutes ago, Ed Stone said:

Is that the same blob that did for last summer?

yes the one that ruined our summer so much, that i grew corn and cucumbers for the first time

[Nick L]

16 minutes ago, iapennell said:

http://www.weathercharts.org/wetterzentrale-t120-t384.htm#228

And this too, also for 20th April:

These charts are for nine days' hence (20th April)- it does not look particularly settled anywhere. This sort of weather-pattern could bring quite cold weather as well.

I see no reason to alter my predictions based, not only on the long-term of these weather-charts- but on other such large-scale fundamentals as a record Westerly QBO and the pattern of sea-surface temperatures across the North Atlantic. For sure, when the upper Westerlies that encircle the Arctic weaken in spring they become subject to short-term weather conditions at the surface and that makes them a little unpredictable but my money remains on late April through much of May being unsettled and wet, particularly in the North and Scotland.  

 

But 90mm of rainfall though? While it's not looking like wall-to-wall sunshine for the rest of the month, there is certainly little sign of meaningful rainfall over the southern half of the UK. In fact, this morning's EC had parts of southern England barely seeing a mm or two for the next 10 days.

[Weather-history]

36 minutes ago, iapennell said:

http://www.weathercharts.org/wetterzentrale-t120-t384.htm#228

And this too, also for 20th April:

These charts are for nine days' hence (20th April)- it does not look particularly settled anywhere. This sort of weather-pattern could bring quite cold weather as well.

I see no reason to alter my predictions based, not only on the long-term of these weather-charts- but on other such large-scale fundamentals as a record Westerly QBO and the pattern of sea-surface temperatures across the North Atlantic. For sure, when the upper Westerlies that encircle the Arctic weaken in spring they become subject to short-term weather conditions at the surface and that makes them a little unpredictable but my money remains on late April through much of May being unsettled and wet, particularly in the North and Scotland.  

 

The irony is that you use those charts as support for rainfall prediction but they don't aid your CET prediction.  Will have to see what happens but northerly flows are not the wettest flows. Slow moving cyclonicity or frequent passage of lows over the UK are. Nothing at the moment supports this.

Edited April 11, 2017 by Weather-history

[iapennell]

@Weather-history, You are correct that northerly flows don't (as a rule) result in the highest rainfall because cold airstreams from the Arctic or sub-arctic hold less moisture. However, these airstreams are also convectively unstable in April as the cold air warms over land warmed strongly by a Sun that gets to 50 degrees above the horizon at lunchtime over the Midlands and South and the upper-level temperatures with this type of synopsis will be unusually cold because of an upper trough over and to the east of Britain. You will also notice that, over SE England, surface pressure is around 1010 mb or lower with a depression not much further to the east.

This means that the wind circulation at low levels will be in-blowing- with the northerlies picking up moisture over the North Sea before moving over land and with a steep temperature lapse-rate through the atmosphere (a feature of Polar Maritime or Arctic Maritime airstreams in April) strong convection currents over land- as the surface and low atmosphere gets heated by the strong spring sunshine- will result in deep cumulus and even cumulonimbus-type clouds that are certainly capable of bringing sharp showers, including hail and thunder.

Regards temperatures, the first eleven days of April have already been much warmer than average (it reached 25C in the SE on Sunday, 9th) and even now- despite cooler conditions from the west temperatures remain a little above the seasonal norm for mid-April in the South. As such, even with a week or more of northerly winds bringing down very cold Arctic air (and I am not predicting more than a week of northerlies) this will not bring mean temperatures to below normal for the month as a whole. Late in April, I am confident that there will be more westerly types that will not bring average temperatures below the long-term seasonal norm. All this considered, I am still confident that I will end up close to final April CET. Scotland will, on the whole be just a little warmer than the long-term normal there (I predicted a mean temperature for lowland Scotland of 7.0C), given the mild start to April this allows plenty of scope for chilly wet weather later in April (as predicted) and for the month to still end up a little warmer than average.

Some of the modelling is showing plenty of indications of cold, wet weather late in April- such as this for the 25th:

The pattern there is cold, showery and (over Scotland) cyclonic. And this for just six days' time:

Quite a vicious little depression there off north-west Scotland driving what looks to be a chilly unsettled Polar-Maritime westerly airstream over Britain.

 

Yes, I could yet be wrong, as I mention in my prediction (above) as the Circumpolar Vortex weakens in springtime it becomes susceptible to alteration by quite localised mesoscale weather conditions (i.e. heavy snowfall over Sweden or a depression moving over Germany) and can therefore change at short notice into a pattern of ridges and troughs quite unlike the one predicted a week earlier. However, on the basis of the record Westerly QBO circulation high above the Equator, the extent of Arctic sea-ice and pattern of sea-surface temperature anomalies around Britain across the North Atlantic (the so-called "Cold Blob"- that area of the North Atlantic that is unusually cold for the location and time of year is south of Greenland- and it will tend to induce an upper trough somewhat downwind of it- i.e. nearer the UK), combined with a look at what the main weather-charts predicted for a few weeks' hence led me to conclude that the most likely outcome this April and May was for a good deal of unsettled weather- in the North and Scotland in particular but with seasonal temperatures on the whole a little above average.

Sea-surface temperatures around Britain are running at around 2C above the seasonal norm and I anticipated that this would moderate the predicted northerlies over the next week and cool westerlies later and that, despite their frequency, temperatures would still be above normal for April on the whole. With a warmer sea and with deep cold Arctic air travelling over it you also make for a more convectively unstable air-mass (translating to heavier showers and thus higher rainfall where such an air-mass moves over land).

 

P.S. Not to worry for those living in the Midlands, southern England, South Wales and Yorkshire I do expect the second half of May to be very warm and settled in these locations as the subtropical high asserts itself over Europe and the storm-tracks over the NE Atlantic migrate to the Iceland area! Even Manchester and Liverpool will probably get a good deal of warm dry weather then.

Edited April 12, 2017 by iapennell
add point