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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