Global Precipitation & Temperature Outlook September 2020

2 September 2020

OVERVIEW
The September Outlook indicates warmer than normal temperatures across much of the vast expanse of Russia. Exceptionally hotter conditions are forecast from Southeast Asia into China and from the Levant north into Ukraine and southern Russia. Uganda will be much wetter than normal and Chile will be much drier than normal south of Santiago.

PRECIPITATION OUTLOOK
In South America, drier than normal conditions are expected in Ecuador and through much of the Cordillera Central Mountains in Peru with precipitation deficits reaching exceptional intensity in Peru. Moderate to severe deficits are forecast for northern and eastern Bolivia into northern Paraguay, moderating as they reach across the borders into Brazil. Parts of western and northern Brazil will be somewhat drier than normal including southern Amazonas, southern Pará, and central Maranhão. Chile will be much drier south of Santiago with deficits reaching into Argentina.

Some precipitation surpluses are forecast in south-central Colombia, around Lake Maracaibo in Venezuela, in Guyana’s southern tip, and in a pocket of coastal Bahia in northeastern Brazil.

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… — 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.

Nearly normal precipitation is forecast for Central America and the Caribbean with some areas of moderate surplus in northern Honduras and Jamaica. In Mexico, deficits are expected in central and southern states including some small pockets of extreme deficit. Moderate deficits are forecast for Tamaulipas State in the northeast.

In the U.S., conditions in Northern California and the Pacific Northwest will be moderately drier than normal with deficits leading into British Colombia, Canada. Moderate surpluses are expected at the intersection of Oklahoma, Missouri, and Arkansas. Surpluses are also forecast from eastern Alaska into Canada.

In Africa, Uganda will be much wetter than normal with surpluses reaching across the border into western Kenya, northern Tanzania, and western Democratic Republic of the Congo. Surpluses will be exceptional in northwestern Kenya. Other regions with a forecast of precipitation surplus, generally moderate, include: northern Algeria, northwestern Nigeria, Cameroon into northern Republic of the Congo; and, pockets in Chad, southern Ethiopia, southern Zimbabwe, and west-central Madagascar. Surpluses are also forecast in South Africa from Northern Cape into Orange Free State.

Precipitation deficits will be severe east of the Blue Nile in Sudan and a few small pockets in Ethiopia and central Kenya. Moderate deficits are forecast scattered along the Pacific Coast in West Africa from Sierra Leone through Nigeria and a few pockets in the Horn. Some moderate deficits are also forecast in southern Madagascar, central Angola, and northern Zimbabwe; and, in South Africa between Lesotho and Swaziland, in the west, and a pocket on the south-central coast.

Most of Europe can expect nearly normal conditions with some surplus in the north. Deficits along Turkey’s Black Sea Coast could reach exceptional intensity. Moderate to severe deficits are forecast in the Caspian Basin well into central Kazakhstan and in the Ural River Basin and much of the Volga Basin in Russia. Surpluses are expected in Russia in the Upper Tom and Upper Yenisei River regions, and in Kyrgyzstan, western Tajikistan, and pockets of eastern Uzbekistan and eastern Turkmenistan. A patchwork of deficit and surplus conditions is forecast for the southern Arabian Peninsula.

In South Asia, surpluses of varying intensity are expected in northwestern India and along its southern coast, Sri Lanka, southeastern Pakistan, and pockets throughout Afghanistan. Deficits are forecast in India’s Far North, Far Northeast, Bhutan, and Chittagong Division in southeastern Bangladesh leading into Myanmar’s west coast. In Southeast Asia, moderate to exceptional deficits will reach from northern Thailand into central and northern Laos and northern Vietnam. Moderate surpluses are forecast for pockets of Borneo and eastern Indonesia.

China can expect generally moderate precipitation deficits in the east spreading from Shanghai but more intense deficits in pockets of Tibet (Xizang). Moderate surpluses are forecast in Henan and Shaanxi in the Yellow River Basin and somewhat more intense surpluses in Xinjiang in northwestern China. Surpluses are expected in northern South Korea and from northeastern North Korea into China. Japan can expect some moderate deficits in the south and far north.

Nearly normal precipitation is forecast for Australia and New Zealand with some moderate deficits in eastern Tasmania.

TEMPERATURE OUTLOOK
The temperature forecast map below draws attention to several regions with intense warm anomalies. Dark red, indicating exceptionally hotter than normal conditions, blankets a widespread area from the southern Gangetic Plain in India through Bangladesh, Far Northeast India, Myanmar, Thailand, Laos, central Vietnam, and much of Cambodia. Exceptional conditions will bleed across Myanmar’s northern border deep into China in Yunnan, western Sichuan, eastern Tibet, and southern Qinghai. Southern Tibet can also expect intensely warmer than normal temperatures as can southern China and Hong Kong. Warm anomalies ranging from moderate to extreme are forecast for much of the remainder of China, Taiwan, the Korean Peninsula, and Japan.

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 t… — 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.

Malaysia, Indonesia, the Philippines, and Papua New Guinea will also see warm anomalies with exceptionally hotter than normal temperatures in many regions. Nearly all of Australia will be warmer than normal with severe to exceptional anomalies in the nation’s northern half. Temperature abnormalities will be less intense in the Murray-Darling Basin but will be severe in eastern New South Wales. South Island, New Zealand will be moderately warmer than normal, while warm anomalies in New Caledonia will be extreme.

In South Asia, much of central and southern India will be warmer than normal with exceptional conditions in the east, as previously mentioned, and on the west coast. India’s Far North will be warmer than usual and much of Nepal will be exceptionally warmer. An exceptionally cooler pocket is predicted in northeastern Uttar Pradesh. Intense warmer anomalies are expected in southern Pakistan leading through Iran’s southern coast to the Strait of Hormuz; a moderately cooler pocket is forecast in north-central Pakistan.

In the Middle East, temperatures will be exceptionally hotter than normal from northern Saudi Arabia through Iraq west of the Euphrates, the Levant, and Turkey. Warm anomalies of varying intensity are forecast for the remainder of the Arabian Peninsula. Some cooler than normal pockets are forecast in southeastern Iran, and warm anomalies along the Red Sea and in Iran’s far northwest.

Warmer than normal temperatures are forecast for much of Russia’s vast area, particularly west of the Urals, the Arctic region, southern Russia, and the Lena River Watershed. Anomalies will be exceptional in the Arctic and in southern Russia (between the Black and Caspian Seas). Moderately warmer temperatures are forecast for western Kazakhstan - becoming more intense as they approach the Caspian Sea - and in Uzbekistan, northwestern Turkmenistan, eastern Tajikistan, and northeastern Afghanistan.

Temperatures in Western and Central Europe are expected to be relatively normal, though Eastern Europe will be much warmer with exceptional conditions in Ukraine, Moldova, and Romania; moderate to severe anomalies in Finland, the Baltics, Belarus, and pockets in the Balkans; and moderate anomalies in Norway, Switzerland, and southern Italy.

Warmer than normal conditions of varying intensity are forecast across northern Africa and will include areas of exceptionally hotter temperatures. Warm anomalies generally ranging from moderate to severe are expected in coastal West Africa in nations along the Gulf of Guinea and leading south through coastal Angola and across interior Angola. The southern nations of Namibia, Zambia, South Africa, and Madagascar can also expect to be warmer than normal. Anomalies will be severe to extreme in Northern Cape and from Johannesburg past Pretoria, South Africa. Warm anomalies will reach exceptional intensity in parts of the Horn of Africa including Somaliland and parts of Ethiopia. Southern Kenya will also be warmer than normal as will the region around Lake Turkana, though the border with Uganda will be cooler. Eastern Sudan will be exceptionally cooler than normal as will the region in Democratic Republic of the Congo west of Lake Tanganyika.

In South America, warmer temperatures are expected in much of the northern half of the continent, moderate overall but extreme to exceptional in French Guiana, the eastern Amazon Basin, Brazil’s northeastern coast, and the Cordillera Central Mountains in Peru. Much of Bolivia, Paraguay, Uruguay, and Argentina can expect normal temperatures with warmer than normal conditions in southwestern Bolivia. Chile’s northern half will be somewhat warmer than normal with conditions reaching into Argentina.

Central America and the Caribbean are forecast to be warmer than normal with exceptionally warmer temperatures in several regions including Honduras, Nicaragua, Costa Rica, Cuba, and Jamaica.

Mexico will be exceptionally warmer along its central Pacific Coast spreading north and south from Nayarit State. The southernmost states will be warmer than normal as will the Yucatan and Baja Peninsulas, and moderately warmer conditions are forecast in the north-central region of the country. Mainland temperatures near the northern Gulf of California are expected to be exceptionally warmer.

The U.S. West, Southwest, and Pacific Northwest will be warmer than normal with exceptional anomalies spanning the California-Nevada border, extreme to exceptional conditions in Arizona, and severe to extreme anomalies in the Northwest. Most of Florida will be much warmer than normal, and the U.S. Northeast will be moderately warmer. A moderately cooler than normal pocket is forecast in eastern Oklahoma.

Like its neighbors in the U.S. Northwest, British Columbia, Canada will be warmer than normal with anomalies ranging from moderate to extreme. On the other side of the country in eastern Canada, Newfoundland can expect severe warm anomalies, and moderate anomalies are forecast in eastern Labrador, Prince Edward Island, and Nova Scotia.

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 September 2, 2020 which includes forecasts for September 2020 through May 2021 based on NOAA CFSv2 forecasts issued August 25 through August 31, 2020.

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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