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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).