Synopsis: La Niña is favored to develop during the Southern Hemisphere winter 2016, with about a 75% chance of La Nina during the fall and winter 2016-17.
During the past month, sea surface temperature (SST) anomalies decreased across the equatorial Pacific Ocean, with near-to-below average SSTs recently emerging in the eastern Pacific. The latest Niño region indices also reflect this decline, with the steepest decreases occurring in the Niño-3 and Niño-1+2 regions. The surface cooling was largely driven by the expansion of below-average subsurface temperatures, which extended to the surface in the eastern Pacific. While oceanic anomalies are clearly trending toward ENSO-neutral, many atmospheric anomalies were still consistent with El Niño, such as the negative equatorial and traditional Southern Oscillation indices. Upper-level easterly winds persisted over the central and eastern Pacific, while low-level winds were near average. Enhanced convection continued over the central tropical Pacific and was suppressed north of Indonesia. Collectively, these anomalies reflect a weakening El Niño and a trend toward ENSO-neutral conditions.
Most models predict the end of El Niño and a brief period of ENSO-neutral by early Southern Hemisphere winter. The model consensus then calls for increasingly negative SST anomalies in the Niño 3.4 region as the winter and spring progress. However, there is clear uncertainty over the timing and intensity of a potential La Niña (3-month Niño-3.4 SST less than or equal to -0.5°C). The forecaster consensus favors La Niña onset during the winter, mainly weighting the dynamical models (such as NCEP CFSv2) and observed trends toward cooler-than-average conditions. Overall, La Niña is favored to develop during the Southern Hemisphere winter 2016, with about a 75% chance of La Nina during the spring and summer 2016-17.
Most landmasses will experience average wind conditions for the month. Winds will be less than average in much of the central and western and southeastern Pacific Ocean into SE Asia and southern South America along with the Central Atlantic Ocean. Around New Zealand winds will be stronger than normal along the east coast as will the western South Pacific through to the far Southwest Pacific through the southern Philippines and the northwest Pacific and North Atlantic including and Eastern Europe and the UK.
Much of the northern hemisphere including Europe and the USA, Canada and Europe should be near normal along with parts of Brazil. New Zealand and southern South America and the southwest Pacific and eastern Australia should be slightly below normal.
Much of Central North America and South America are forecast as usually low while similar conditions prevail in much of Africa and SE Asia and China and Central Asia. Warm episodes are limited to western Europe and the western South Pacific and insular SE Asia and the Arctic region.
In the western hemisphere extreme precipitation events are forecast for Mexico, and the Southwest and across to Texas and parts of the northern and eastern Caribbean. The Amazon could have unusually to very unusually low rainfall.
In SE Asia and unusually low rainfall is forecast through the western island portion of the region. In Northeast Asia unusually to very unusually high rainfall events are possible in much of China and also the eastern South Pacific.
In the southern Sahel of Africa and West Africa and isolated parts of west Asia unusually high rainfall is possible.
Through much of Europe and continental north Asia usual normal to usual high conditions prevail. Usual high is forecast for parts of Southern Africa.
The slow evolution of ENSO to a more neutral situation can be viewed through sea surface temperature anomaly maps. The equatorial Eastern Pacific is lower than normal than normal. The Indian Ocean is warmer than normal and then previous months. The western and central Atlantic is also warmer than normal. The ocean surrounding New Zealand is warmer than normal to the east and north and warmer than normal around most of Australia with a warm pool expanding between Australia and Indonesia. The central South Pacific remains cooler than normal. The sea in Northeast Asia is also considerably cooler than normal as well as in the northeast Canada while the artic sea is warmer than normal.
Slightly wetter conditions prevail in much of the northern hemisphere with greater anomalies in the southern tier of the USA and the Caribbean and Southern Florida and through the Andes of South America and southern Brazil and Argentina and SE China while drier than normal conditions prevail through the Western and Southwest Pacific region. In the Southern hemisphere dryness is shown for Southern Africa, Madagascar and the Amazon basin and far southern Chile and the South Pacific islands. Wetter than normal conditions prevail in the northern quadrant of the South Pacific along the equator and into the Indonesian archipelago and the Northern Territory of Australia. Much of Europe and Eurasia is near normal to slightly wetter than normal. High rainfall anomalies are expected in Bangladesh and Myanmar.
Much of Canada down to the Gulf of Mexico are above normal for temperature while the western States of the USA and Mexico are cooler to considerably cooler than normal along with western Australia and Central Africa. Central America and the Caribbean and the northern half of South America are above normal as is the Eastern half of Asia and most of Australia and Southeast Asia and India and southern part of the Middle East. Part of southern China and northern SE Asia and far Northeast Asia are much colder than normal along with much of East Africa. Eastern Indonesia through Papua New Guinea and the South Pacific should be slightly cooler than normal. Most of Australia and New Zealand should be slightly to moderately above normal. Argentina and southern Brazil should be cooler than normal.