Global Precipitation & Temperature Outlook December 2018

3 December 2018

OVERVIEW
The December Outlook indicates exceptionally warmer than normal temperatures, 40+ years return period, in Southeast Asia. Much wetter than normal conditions are forecast for the Yangtze River Basin in China.

PRECIPITATION OUTLOOK
Widespread wet anomalies ranging from moderate to exceptional are expected in the Lower and Middle Reaches of the Yangtze River Basin in China. Southeast Asia is forecast to be moderately wetter than normal, as are Malaysia and Sumatra. Wet anomalies are also expected in Kyushu and Shikoku, Japan, northwestern Mongolia, and northern Heilongjiang, China into Russia. Primarily moderate dry anomalies are forecast in Papua New Guinea.

Precipitation conditions in Australia are expected to be relatively normal.

Relatively normal conditions are also forecast for Central and South Asia, with some mild wet anomalies in Afghanistan and mild dry anomalies in Russia’s Central Siberian Plateau.

In the Middle East, northern Iraq and eastern Turkey may see moderately wetter than normal conditions.

The British Isles will be somewhat wetter than normal, with similar conditions reaching throughout Northern Europe from Norway into Northern European Russia. Moderate dry anomalies are forecast for the southern Iberian Peninsula.

Dry anomalies will reach across the Strait of Gibraltar into Morocco and Algeria in northwestern Africa. Along the western Gulf of Guinea, Liberia and Ghana are forecast to be moderately drier than normal, while wetter than normal conditions are forecast in the southern Gulf countries - Cameroon, Gabon, western Congo, western Democratic Republic of the Congo (DRC), and into northwestern Angola. Wet anomalies will also form a ragged band across the center of the continent affecting southern Central African Republic, northwestern DRC, South Sudan, Uganda, and through the Horn of Africa. Anomalies are forecast to reach extreme intensity in Ethiopia and Somalia. Some wet anomalies are also expected in Tanzania. Moderately drier than normal conditions are forecast for southwestern Madagascar, central South Africa, and Lesotho.

In North America, some areas of moderate dry anomalies are forecast in Quebec, Canada and farther west in Alberta with milder anomalies in nearby provinces. Across the border in the US, some dry anomalies are forecast in pockets of the Upper Midwest, reaching severe intensity in North Dakota, and moderate to severe conditions in Michigan’s Upper Peninsula. Southern Alabama and Georgia, as well as Florida’s northern half, will be moderately wetter than normal.

Nearly normal conditions are forecast for Mexico, and some small but fairly intense pockets of dry anomalies are expected in Central America. In South America, dry anomalies are forecast for Colombia and some pockets in Venezuela, and will reach exceptional intensity in northern Colombia. Intense dry anomalies are also expected in south-central Peru in the Cordillera Oriental Mountains leading through western Bolivia. Wetter than normal conditions are forecast in the eastern Amazon Basin in Brazil and into French Guiana. Anomalies will be moderate to severe overall but may be extreme in Amapá.

TEMPERATURE OUTLOOK
Conditions in Southeast Asia are expected to be much warmer than normal, with severe to exceptional anomalies in Thailand, Laos, Cambodia, central and southern Vietnam, and southern Myanmar. Warm anomalies nearly as intense are forecast for Malaysia, Indonesia, Philippines, and Papua New Guinea, including exceptional pockets.

Australia will see warm anomalies of varying intensity in the center of the country, and exceptional anomalies in the north in Top End, Northern Territory and Cape York Peninsula, Queensland.

In East Asia, warmer than normal conditions are forecast for many parts of China, including exceptional anomalies in Yunnan, Hainan, and a pocket in northwestern Qinghai. Moderate to severe anomalies are forecast in the Yellow River Basin, the North China Plain, and along the southeast coast. Exceptional warm anomalies are forecast for Taiwan. In Japan, severe warm anomalies are expected in southern Honshu.

Much of India will be warmer than normal but anomalies will be especially intense in the southern half of the nation and in Sri Lanka, ranging from severe to exceptional. Warm anomalies in central Pakistan will be severe, with less intense conditions in the rest of the country. Northern Afghanistan is expected to be moderately warmer than normal. Eastern Nepal may be somewhat cooler than normal.

Moderate warm anomalies are forecast in Turkmenistan, Uzbekistan, southern Kyrgyzstan, and Tajikistan.

In the Middle East, exceptionally warmer than normal conditions are forecast for Yemen; moderate to extreme anomalies in south-central Saudi Arabia; and primarily moderate anomalies in Iran and southeastern Turkey.

Western, Central, and Northern Europe are forecast to be warmer than normal with severe anomalies from France through Germany, along with some pockets of extreme intensity.

Areas forecast to be warmer than normal in Africa include: northwestern Africa; coastal areas around the Gulf of Guinea; many parts of southern Africa; Magadascar; and around the southern Red Sea and Gulf of Aden. Anomalies are expected to reach exceptional intensity in: Liberia, coastal Ghana, coastal Nigeria, northeastern Angola, eastern South Africa, a pocket in southern Madagascar, and pockets in the Horn of Africa. Areas forecast to be cooler than normal include: northern DRC, South Sudan, parts of southern Ethiopia, northern Kenya, and east-central Uganda.

In North America, moderately warmer than normal temperatures are forecast from the Upper Midwest, US well into the southern portions of Canada’s Prairie Provinces, and in Alaska. Anomalies may be severe in northern Minnesota. Severe anomalies are also expected in southern Mexico; conditions may be extreme in Nayarit on the west coast. Severe to extreme warm anomalies are forecast for Guatemala, Belize, Honduras, Costa Rica, Panama, and Cuba.

In South America, areas of warm anomalies include: Colombia, Ecuador, central Peru, western Bolivia, Chile, and eastern Brazil. Pockets of extreme or even exceptional intensity are possible in the aforementioned regions. Cool anomalies ranging from moderate to extreme are forecast for: northeastern Venezuela; southeastern Suriname, French Guiana, and across the border into Brazil; eastern Bolivia; Paraguay; and, north-central Argentina and parts of the Argentine Pampas.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

ABOUT THIS BLOG POST
Each week, ISciences processes an ensemble of 28 seasonal temperature and precipitation forecasts issued by the National Oceanic and Atmospheric Administration's Climate Forecast System Version 2 (CFSv2). We present our results in a proprietary weekly report titled Global Water Monitor and Forecast: Precipitation and Temperature Outlook. This blog post summarizes our Outlook released December 3, 2018 which includes forecasts for December 2018 through August 2019 based on NOAA CFSv2 forecasts issued November 24 through November 30, 2018.

Technical details:

  • Each CFSv2 forecast is bias corrected by:

    • Constructing probability density functions from CFSv2 hindcasts.

    • Fitting the hindcast probability distribution functions to a generalized extreme value distribution.

    • Using an inverse lookup to an extreme value distribution fitted to the observed temperature and precipitation record (Fan & van den Dool 2008, Chen et al. 2002).

  • The map colors depict the return period of the median forecast anomaly.

  • Regions where the interquartile range of the ensemble spans both above normal and below normal conditions are hashed as having uncertain direction.

  • Regions where the interquartile range of the ensemble divided by the median forecast is large (>0.4) are hashed as having uncertain magnitude.

  • Results are reported in terms of return period using a 1950-2009 baseline.

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Comment

Many analyses reported in ISciences-authored blog posts are based on data generated by the ISciences Water Security Indicator Model (WSIM). Other sources, if used, are referenced in footnotes accompanying individual posts. WSIM is a validated capability that produces monthly reports on current and forecast global freshwater surpluses and deficits with lead times of 1-9 months at 0.5°x0.5° resolution. This capability has been in continuous operation since April 2011 and has proven to provide reliable forecasts of emerging water security concerns in that time-frame. WSIM has the ability to assess the impacts of water anomalies on people, agriculture, and electricity generation. Detailed data, customized visualizations, and reports are available for purchase.

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