Global Precipitation & Temperature Outlook April 2018

2 April 2018

The April Outlook indicates wetter than normal conditions in India, East Africa, and northwest Brazil. Significantly warmer than normal temperatures are forecast for Far East Russia and Alaska, much of eastern China, particularly the Yangtze River Basin from Shanghai to Chongqing, and eastern Australia from Brisbane to Canberra. 

In South Asia, wet anomalies of varying severity are forecast throughout India, with the center of the country expected to be moderately wetter than normal. Anomalies in the Ganges Basin in the north will be more intense, with a return period of 20 to 40 years, and some southern states could see exceptional anomalies with a return period of 40 years or more. Much wetter than normal conditions are also forecast for Bangladesh, Nepal, and Tibet. 

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.

Moderate dry anomalies are forecast for Central Asia in Afghanistan,Turkmenistan, eastern Uzbekistan, and southern Kazakhstan. Anomalies may be more severe in Tajikistan.

Much of Southeast Asia is expected to see relatively normal conditions of precipitation. However, dry anomalies are forecast for southern Vietnam, southern Laos, Cambodia, and the Malay Peninsula; and, some wet anomalies are forecast for the island of New Guinea.

Merely mild dry anomalies are forecast for Australia but may be slightly more intense in the southwest, especially the Blackwood River area of Western Australia.

In Africa, moderate to extreme wet anomalies are forecast for the Horn of Africa, South Sudan, eastern Uganda, northeast Kenya, and in Angola, western Namibia, western Zambia, Zimbabwe, and Mozambique.

The United Kingdom will be moderately wetter than normal, as will Brittany, France, and vast stretches across Russia. 

In South America, the Amazon Basin in Brazil is expected to be wetter than normal, with anomalies in a return period range of 5 to 40 years. Primarily moderate wet anomalies will reach into southern and eastern Venezuela and Guyana. Milder wet anomalies are forecast from central Brazil trailing to the state of Espíritu Santo on the Atlantic coast. A pocket in central Colombia will be much wetter than normal, as will eastern Bolivia. Much drier than normal conditions are expected in a path reaching from Colombia's southwestern coast through western Ecuador and into northwestern Peru.

Conditions in Central America will be somewhat wetter than normal.

In the US, moderate dry anomalies are expected in west Texas, and mild to moderate wet anomalies are forecast for the Ohio River Valley and the Pacific Northwest. Across the border from the US Northwest, southern British Columbia, Canada will be somewhat wetter than normal. And elsewhere in Canada, moderate dry anomalies are forecast for the central portion of Northwest Territories, leading southeast through the northern half of Saskatchewan, much of Manitoba, and into northern Ontario.

Most noticeable in the temperature forecast below is the vast stretch of exceptional warm anomalies - with a return period of over 40 years, shown in dark red - predicted for Russia's Far East, along with warm anomalies of varying severity in much of the eastern half of the country. Noteworthy also, are intense warm anomalies in many parts of China, which will be extreme to exceptional in the Yangtze River Basin from Shanghai to Chongking. Mongolia is forecast to be moderately warmer than normal. The Korean Peninsula and Japan will be warmer than normal as well, with anomalies reaching a return period of 10 to 20 years. 

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 Southeast Asia, primarily moderate warm anomalies are forecast for western Thailand, southern Laos, southern Vietnam, Malaysia, and Indonesia but may be severe in eastern Thailand and the Malay Peninsula.

Australia jumps out on the map with warm anomalies blanketing much of the country, with anomalies expected to be especially intense in the southeast, and in the western Pilbara region of Western Australia.

In South Asia, much cooler than normal temperatures are expected in Bangladesh, eastern Nepal, and western Bhutan, while Afghanistan, Pakistan, and western India will be warmer than normal.

Warmer temperatures will also reach into Turkmenistan, where severe anomalies are forecast. Elsewhere in Central Asia, Uzbekistan and southern and western Kazakhstan will be moderately warmer than normal, but severe to exceptional warm anomalies are forecast for Tajikistan.

Much of the Middle East will be warmer than normal, particularly northern Saudi Arabia where anomalies with a return period of over 40 years are expected. Intense warm anomalies are expected in western and southern Iraq, Qatar, western Oman, eastern Turkey, and in southern Iran along the Gulf of Oman.

Northern Africa is forecast to be moderately warmer than normal, but conditions may be more intense in the east along the Red Sea coast, and in the west in Mauritania and between Algeria and Niger. Much cooler than normal temperatures are forecast for South Sudan, southern and eastern Ethiopia, Somaliland, northern Kenya, eastern Uganda, southern Democratic Republic of the Congo, and northwestern Namibia. Pockets of cooler than normal conditions are expected in central Tanzania and other parts of south-central Africa. Madagascar, however, will see warmer than normal temperatures,

Moderate warm anomalies are forecast for Central and Eastern Europe; conditions may be severe in Switzerland and Romania.

In North America, the US Southwest will see moderately warmer than normal temperatures with severe anomalies forecast for New Mexico. Much of the Midwest will be somewhat cooler than normal, with a return period from 5 to 20 years. Temperatures in Alaska will be warmer than normal, with severe anomalies in the center of the state.

Relatively normal temperatures are forecast for South America, with some moderate warm anomalies in north-central Brazil and other pockets of the continent.

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.

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 April 2, 2018 which includes forecasts for April 2018 through December 2018 based on NOAA CFSv2 forecasts issued March 25 through March 31, 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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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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