Global Precipitation & Temperature Outlook December 2021

3 December 2021

OVERVIEW
The December 2021 Outlook indicates much wetter than normal conditions in Bangladesh and along the Gulf of Khambhat (Cambay) in western India. Temperatures will be much hotter than normal in African nations bordering the Gulf of Guinea as well as in Indonesia and New Zealand, among other places.

PRECIPITATION OUTLOOK
Several regions in South Asia are expected to be much wetter than normal. Widespread, exceptional precipitation surpluses are forecast in Bangladesh and Indian states to the east. Surpluses ranging from moderate to exceptional are forecast in Indian regions along the Bay of Bengal and into neighboring landlocked states. India’s west coast will be exceptionally wetter around the Gulf of Khambhat (Cambay) in Gujarat and coastal Maharashtra, with surpluses downgrading gradually as they reach into central Maharashtra and well into Karnataka. Moderate surpluses are expected in northern India centered in Himachal Pradesh. Nepal will be wetter than normal with moderate to severe surpluses, and moderate surpluses are forecast in western Bhutan. Pakistan, Afghanistan, and Sri Lanka can expect relatively normal precipitation.

Precipitation outlook. Reds indicate below normal monthly total precipitation. Blues indicate above normal monthly total precipitation. The darker the color, the more extreme the anomaly relative to a 1950-2009 climatic baseline. Colors are based on the expected return period of the anomalies.

In East Asia, precipitation surpluses of varying intensity are forecast in Tibet (Xizang), and moderate to severe surpluses in Northeast China in Heilongjiang and far northern Inner Mongolia. Scattered areas of deficit are forecast in pockets of northern China including northern Gansu, northern Shanxi, and near Inner Mongolia’s border with Jilin. Some pockets of deficit are also forecast for Mongolia including moderate deficits near Ulaanbaatar. Much of the Korean Peninsula will be drier than normal with moderate deficits overall and some severe pockets in South Korea. A few pockets of deficit are forecast in central and southern Japan but surpluses are expected on Hokkaido’s west coast including in Sapporo.

In Southeast Asia and the Pacific, widespread precipitation surpluses are expected in regions along Myanmar’s western border, while moderate deficits are expected along it’s eastern border. Deficits will reach into northern Thailand, northern Laos, and northern Vietnam. Malaysian Borneo and southern Sulawesi will be drier than normal. Moderate surpluses are expected in the central Philippines and a few pockets elsewhere in the Pacific.

The forecast for Australia and New Zealand indicates nearly normal precipitation. Some areas of moderate deficit are expected in the Kimberley Region and the Hamersley Mountain Range in Western Australia, and moderate pockets of surplus in southeastern Australia from Canberra and the Australian Alps to the coast.

Precipitation in Central Asia will be relatively normal though severe deficits are forecast on the Uzbek-Kazakh border near the Aral Sea. In Russia, widespread moderate precipitation surpluses are expected from the Western Siberian Plain into the Central Siberian Plateau. Surpluses will be more intense - severe to exceptional - north of Lake Baikal. Surpluses are also forecast in the far east, generally moderate along the coastal Arctic, severe in Chukchi, and reaching exceptional intensity in the Kamchatka Peninsula.

The Middle East can expect moderate to extreme precipitation deficits in north-central Saudi Arabia. Moderately drier than normal conditions are forecast in Iraq west of the Euphrates River and in the north between the Euphrates and Tigris. Kuwait will be moderately drier, as will Iran’s southern regions along the Persian Gulf with similar conditions reaching across the Gulf into pockets of United Arab Emirates and Qatar. Some moderate surpluses are expected in far eastern Turkey and pockets in Armenia and Azerbaijan.

Precipitation in Europe and European Russia will be relatively normal with moderate deficits in southwestern Spain.

Moderate deficits will reach into Africa in Morocco and pockets of Algeria. The Horn of Africa can also expect to be moderately drier than normal in several regions of Ethiopia and in Somaliland. Widespread deficits are forecast from northern Zambia into southern Democratic Republic of the Congo (DRC), much of Tanzania, Malawi, and northern Mozambique. Deficits will be moderate to severe overall but more intense in pockets of Zambia and DRC. Madagascar’s southern half will also be drier than normal.

Nations along the southern Gulf of Guinea can expect wetter than normal conditions from south-central Cameroon into northern Angola where surpluses will reach exceptional intensity. Widespread surpluses are forecast in South Africa in the west, south, and northeast including Pretoria. Surpluses will be severe in Northern Cape. Southern Namibia and southern Botswana will be somewhat wetter than normal. Elsewhere in Africa, pockets of surplus are forecast in Central African Republic and the southern tips of Somalia and Kenya.

In South America, much of the Brazilian Amazon region will be wetter than normal with moderate to extreme surpluses. Surpluses will reach into Venezuela’s southern tip, becoming exceptional, and pockets of moderate surplus are forecast in the Guianas. Several states in Brazil’s Southeast Region will be moderately wetter than normal, but moderate precipitation deficits are forecast in Rio Grande do Sul and well into Uruguay. Surpluses, primarily moderate, will dominate much of Bolivia though moderate deficits are expected in the nation’s southwest leading into Argentina. Chile’s southern half will be drier than normal. Central Argentina will be wetter than normal in San Luis, Mendoza, and La Pampa Provinces. In the continent’s northwest, mixed conditions are expected from western Venezuela into Peru, including deficits tracing the Andes into northern Peru, and surpluses in eastern Ecuador.

Most regions in Central America and the Caribbean will see near-normal precipitation. However, moderate to severe deficits are forecast in central Guatemala, moderate deficits near Havana, and surpluses in the southern Bahamas.

Mexico will be moderately drier than normal in a wide path along the Pacific Coast from Sinaloa through Michoacán with conditions reaching into landlocked states. Southern Baja will also be moderately drier. Precipitation deficits, generally moderate, are expected in Mexico’s south between the Gulf of Mexico and Gulf of Tehuantepec, and some pockets in the Yucatan Peninsula.

Precipitation in the southeastern United States will be less than normal, with mild to moderate deficits overall but severe deficits from central South Carolina into Georgia, and along Florida’s Gulf Coast from Tampa Bay to the south. Moderate deficits are forecast at the intersection of South Dakota, Nebraska, and Iowa. Moderate surpluses are expected in north-central Wyoming.

In the Canadian provinces, precipitation surpluses are forecast in western Newfoundland; regions of Quebec along Hudson Bay; the Ivanhoe River Watershed in Ontario; a narrow belt across southern Manitoba reaching Winnipeg; and following the southern border of Alberta and British Columbia. In the territories, widespread moderate to severe deficits are forecast from western Nunavut through the eastern half of Northwest Territories. Moderate deficits will reach from the northern extreme of Northwest Territories through much of the Yukon and into northeastern Alaska.

TEMPERATURE OUTLOOK
While relatively normal temperatures are expected in much of North Africa, West Africa can expect warm anomalies and exceptionally hotter temperatures will be widespread in nations along the Gulf of Guinea from Côte d'Ivoire through Gabon and Republic of the Congo. Sudan will be moderately warmer than normal but anomalies will be more intense in the Horn of Africa: severe from Eritrea into northern Ethiopia, severe to exceptional in Somaliland and southern and eastern Ethiopia, and of varying intensity in Somalia.

Temperature outlook. Reds indicate above normal monthly average temperature. Blues indicate below normal monthly average temperature. The darker the color, the more extreme the anomaly relative to a 1950-2009 climatic baseline. Colors are based on the expected return period of the anomalies.

In the heart of Africa, temperatures are expected to be warmer than normal in Democratic Republic of the Congo (DRC), Rwanda, and Burundi. Warmer temperatures are also forecast from Angola on the Atlantic Coast through Mozambique in the east. Anomalies will be severe overall but exceptional in several regions including northern Zambia. Intensely hotter than normal temperatures will blanket Madagascar. South Africa’s northeast will be much hotter than normal from Durban reaching north through Eswatini, downgrading somewhat past Johannesburg and Pretoria. A few places in Africa are forecast to be moderately cooler than normal including small pockets in central Namibia, spanning DRC’s north-central border, and east of Algiers on the Mediterranean Coast.

Relatively normal temperatures are forecast for much of Europe and European Russia. However, Norway’s Svalbard archipelago will be warmer than normal and moderately warmer temperatures are expected in the nation’s fjord region north of Bergen. Temperatures will also be moderately warmer than normal in other pockets of Europe including coastal Netherlands, Normandy and Brittany in France, western Ireland, Italy’s “boot,” central Romania and southeastern Bulgaria, and the Donbass region of eastern Ukraine.

Iran can expect warmer than normal temperatures throughout much of its extent with extremely to exceptionally hotter temperatures from Isfahan Province in the center of the country through southern provinces to the Strait of Hormuz. In other regions of the Middle East, moderate to severe warm anomalies are forecast in Iraq west of the Euphrates River and between the Lower Tigris River and Euphrates. Turkey will be moderately warmer in the east around Lake Van, as will eastern Syria and Azerbaijan. On the Arabian Peninsula, southwestern Yemen will be much warmer than normal; severe warm anomalies are expected in Qatar and Bahrain; and moderate to severe anomalies in Saudi Arabia’s Riyadh and Madinah Provinces.

Most regions in Central Asia will be warmer than normal with moderate to severe anomalies expected but temperatures could be extremely warmer south of the Naryn River in Kyrgyzstan and a pocket in eastern Tajikistan. In Russia, severe warm anomalies are forecast in the Lower Volga River region and the Ural River Watershed into Kazakhstan, and moderate anomalies in Trans-Volga. From the southern Ural Mountains through the Western Siberian Plain, temperatures will be warmer than normal with severe anomalies from Yekaterinburg to Tomsk. The Central Siberian Plateau will be moderately warmer than normal overall as will regions in the Arctic east and the Kamchatka Peninsula. Warm anomalies will be severe in Russian regions bordering Mongolia including the area around Lake Baikal, and also north of China where anomalies will reach extreme intensity south of the Zeya River Reservoir.

In South Asia, Sri Lanka will be exceptionally hotter than normal. Nearby in India’s southern tip, anomalies will be extreme in Tamil Nadu and severe reaching north to the Penner River in Andhra Pradesh. From the center of India to the Bay of Bengal moderate to severe warm anomalies are forecast, and also from northwestern India into the far north. India’s Far Northeast will be extremely to exceptionally hotter than normal and intense anomalies are also forecast for much of Bangladesh. Somewhat cooler than normal conditions are forecast in a pocket of northwestern Maharashtra. Near-normal temperatures are forecast in the Helmand River Basin in Afghanistan while moderately warmer than normal temperatures are expected elsewhere and severe warm anomalies in the Hindu Kush. Moderate to severe warm anomalies are also forecast in Pakistan, severe in the region of the Indus River’s many tributaries in northern Pakistan. Central Nepal will be moderately warmer than normal.

In East Asia, China can expect exceptionally hotter temperatures in western Sichuan, downgrading somewhat as they reach into eastern Tibet (Xizang), while western Tibet will be cooler than normal. Temperatures will be exceptionally hotter than normal north of the Bohai Sea and moderate to extreme warm anomalies are forecast throughout much of China’s northeast. Beijing and the surrounding regions can expect warm anomalies reaching extreme intensity. In the Lower and Middle Yellow River (Huang) Watershed moderately warmer than normal temperatures are forecast but anomalies will be intense in the Upper Basin. In the Han River Basin, a northern tributary of the Yangtze, moderate to severe warm anomalies are forecast, while anomalies in the Huai River Basin between the Yellow and Yangtze Rivers will reach extreme intensity. Elsewhere in East Asia, Honshu, Japan will be moderately warmer than normal and Hokkaido can expect severe to exceptional warm anomalies. Much of Mongolia will be warmer than normal with anomalies of varying intensity.

Though many regions in Southeast Asia can expect relatively normal temperatures, much of Myanmar will be extremely to exceptionally hotter than normal. Intense warm anomalies are also expected throughout Malaysia, Indonesia, the central and southern Philippines, Lesser Sunda and Maluku Islands, and Papua New Guinea.

Exceptionally hotter than normal temperatures will reach into northern Australia blanketing Northern Territory’s Top End, the Kimberley Region in Western Australia, and parts of the Cape York Peninsula in Far North Queensland. The intensity of anomalies across northern Australia will downgrade as they reach south spanning the central Outback. Brisbane will be moderately warmer than normal while near-normal temperatures are forecast in other major cities. A cool pocket is expected in the Gascoyne Region near the coast of Western Australia. Tasmania will be much warmer than normal with widespread extreme anomalies, including in Hobart. South Island, New Zealand will be much warmer as well with extreme to exceptional anomalies. In North Island, moderate to extreme anomalies are expected.

The forecast for South America includes cooler than normal temperatures in Paraguay and throughout the vast Gran Chaco region well into eastern Bolivia and northern Argentina. Argentina’s Rioja and San Luis Provinces can also expect to be cooler than normal, while northern Patagonia is forecast to be moderately warmer than usual. Santa Catarina State in southern Brazil will be cooler than normal, but the nation’s easternmost states will be moderately to extremely hotter than normal with exceptional anomalies in Ceará. Moderate to extreme warm anomalies are also forecast in the states of Goiás and Minas Gerais, and moderately warmer than normal temperatures in many remaining parts of the nation’s eastern half, and in Amapá in the north and the western Amazon.

Across the northern arc of the continent, northern Guyana will be exceptionally hotter than normal and eastern French Guiana will be moderately warmer. Warm anomalies of varying intensity are expected in southern and northwestern Venezuela, Colombia, Ecuador, and Peru. Anomalies will be moderate overall but more intense following the Andes, especially through western Bolivia into Argentina. Pockets of central Chile will be moderately warmer than normal but more intense anomalies are expected near Copiapó in the north.

In Central America and the Caribbean, warm anomalies are forecast throughout the Caribbean, exceptional in the Bahamas and Jamaica, and extreme in Cuba. Warm anomalies in Central America will be severe to extreme from Honduras through Guatemala but less intense elsewhere.

Much of Mexico will be warmer than normal, with intensely warmer temperatures in many regions. Anomalies will be exceptional in the central Pacific States; severe to exceptional in a vast area from the central north to the Gulf of Mexico; extreme in the south between the Gulfs of Mexico and Tehuantepec, and severe in the Yucatan Peninsula. Warm anomalies of varying intensity are forecast for the Baja Peninsula.

The United States can expect widespread warmer than normal temperatures of varying intensity in many regions. In the West, anomalies will be extreme to exceptional from Colorado through New Mexico and the Rio Grande Watershed, moderate to extreme in Utah and Arizona, and moderate in Nevada and south of the San Joaquin River in California. Extreme warm anomalies are forecast for Louisiana and along the Gulf Coast past Houston. Widespread severe warm anomalies are expected from the Middle and Lower Mississippi River Watersheds reaching to the East Coast through the Ohio River Watershed and the Deep South. The U.S. Upper Midwest, Northeast, and central Texas will be moderately warmer than normal. Alaska can expect somewhat warmer than normal temperatures near Barrow.

Temperatures in Canada will be relatively normal with moderately warmer conditions in Southern Ontario, Newfoundland, and in Quebec in the Great Whale River Watershed near the east coast of Hudson Bay.

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 2, 2021 which includes forecasts for December 2021 through August 2022 based on NOAA CFSv2 forecasts issued November 24 through November 30, 2021.

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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