Synopsis: A transition to ENSO-neutral is expected to occur by February 2017, with ENSO-neutral then continuing through the first half of 2017.
La Niña continued during December, with negative sea surface temperature (SST) anomalies continuing across the central and eastern equatorial Pacific. The weekly Niño index values fluctuated during the last month, with the Niño-3 and Niño-3.4 regions hovering near and slightly warmer than -0.5°C. The upper-ocean heat content anomaly was near zero when averaged across the eastern Pacific, though near-to-below average subsurface temperatures were evident closer to the surface. Atmospheric convection remained suppressed over the central tropical Pacific and enhanced over Indonesia. The low-level easterly winds were slightly enhanced over the western Pacific, and upper-level westerly anomalies were observed across the eastern Pacific. Overall, the ocean and atmosphere system remained consistent with a weak La Niña.
The multi-model averages favor an imminent transition to ENSO-neutral (3-month average Niño-3.4 index between -0.5°C and 0.5°C), with ENSO-neutral lasting through August-October (ASO) 2017. Along with the model forecasts, the decay of the subsurface temperature anomalies and marginally cool conditions at and near the ocean surface portends the return of ENSO-neutral over the next month. In summary, a transition to ENSO-neutral is expected to occur by February 2017, with ENSO-neutral then continuing through the first half of 2017.
Even as the tropical Pacific Ocean returns to ENSO-neutral conditions, the atmospheric impacts from La Niña could persist during the upcoming months.
Most landmasses will experience average wind conditions except for eastern South America and New Zealand and Tasmania and the eastern Caribbean that should all have lower than normal winds over the month. Also Northeast African parts of East Africa should have lower than normal winds for the month as well as the southern parts of West African countries and East Asia. Higher than average winds are expected in the North Pacific and North Atlantic through to the UK.
Much of the northern half of the northern hemisphere should be near normal while the mid-latitudes and tropics should be slightly below normal and the southern latitudes near normal except much of Australia and eastern Brazil that should be below normal along with most of north and west Africa and also parts of southern Africa. New Zealand and southern South America and Southern Africa should be near normal.
Much of Central North America and South America are forecast as usually low while similar conditions prevail in much of Africa and China and Central Asia and Northwest. Unusually cold events are forecast for the Arctic and Argentina. The eastern South Pacific and insular SE Asia plus the eastern seaboard of China are all forecast to experience unusually warm outbreaks. Much of Africa is either usually low or usually high with no extremes foreast.
In the western hemisphere low precipitation events are forecast for the Canadian arctic. Higher than normal rainfall events area also expected in northeast Brazil and Argentina and Bolivia. Usual high is forecast for Hawaii.
In SE Asia and Australia unusually low rainfall is forecast through the western island portion of the region and southern China and in northern Australia. Unusually high rainfall is expected in the interior of China and along the eastern seaboard. In insular SE Asia Luzon could experience unusually high rainfall as well as areas of the South China Sea and also the western Pacific ocean. The rest of the region has usually low or usually high conditions forecast.
Extreme rainfall events are possible in Ethiopia and also in the north central Africa as well as far southern Africa. Through much of Europe and continental north Asia usual normal conditions prevail.
Warmer than normal conditions prevail in the western North Atlantic and near normal conditions elsewhere. In the South Atlantic warmer than normal conditions prevail except along the coast of southern Brazil and Argentina that are cooler than normal.
The Northern Pacific is near normal with ENSO neutral conditions prevailing with cooler to near normal waters in the eastern tropical Pacific. The far northern Pacific should be considerably warmer than normal as well as the Arctic sea. The South Pacific is warmer than normal off the South American coast and also in the western South Pacific near Australia and New Zealand while the central South Pacific is near normal.
The Indian Ocean is warmer than normal from north to south in the eastern region near Indonesia, and normal to cooler than normal South of India and Sri Lanka with cooler than normal water off the coast of Africa and also off the coast of southwestern Australia.
North and South America near normal with slightly wetter conditions also northern and northeast South America and the very far southern tip of the continent.
Southeast Asia looks near normal north of the Equator and wetter than normal south of Equator while India is near normal. Just near the equator in the Central to western Pacific it should be much drier than normal. Much of Bangladesh and western Myanmar is likely to be wetter than normal and most of southern China wetter than normal and north Asia near normal to slightly wetter than normal.
Much of Africa should be near normal except from Cameroon and to the west that should be wetter than normal. The Middle East and western central Asia should be near normal. Europe should be near normal.
Much of North America, the Caribbean, and Central and northern South America should be warmer than normal except for western Mexico that should be cooler than normal. Argentina and Southern Brazil should be cooler than normal.
New Zealand should be near normal. Southwestern and central Australia cooler than normal and all of east and Southeast Asia should be warmer than normal with India and eastern Pakistan near normal. Southwest India should be warmer than normal as well as western China and Tibet. East Asia and Northeast Asia should be slightly to moderately cooler than normal.
Central Africa should be cooler than normal and Southern Africa warmer than normal. The Middle East and Iran and Afghanistan should be cooler than normal. The Arctic should be considerably warmer than normal. Most of Europe should be near normal except the Central Europe that could be moderately cooler than normal.