Global Precipitation & Temperature Outlook September 2018

5 September 2018

The September Outlook indicates that intense heat anomalies which have dominated Central Europe for the past month are expected to moderate overall. Exceptionally warmer than normal temperatures will prevail in Madagascar. Much drier than normal conditions are forecast in India along its southern Arabian Sea coast and also in Ethiopia's central Highlands.

In Africa, extreme to exceptional dry anomalies are forecast in central Ethiopia running north/south through the Highlands. Dry anomalies of generally lesser intensity are expected straddling Central African Republic, South Sudan, and Democratic Republic of the Congo, and also in southwestern Kenya. Wet anomalies are forecast across the southern Sahara and the Sahel, primarily moderate but with some pockets reaching extreme or even exceptional intensity. Conditions are also expected to be wetter than normal in: eastern Ethiopia, Somalia, southeastern Tanzania, southern Cameroon, northern Republic of the Congo, and eastern Gabon.

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.

Relatively normal precipitation is forecast for Europe, with some moderately drier than normal conditions in northeastern Germany and Ireland, and possibly wetter conditions in Hungary, western Slovakia, eastern Austria, and northern Croatia.

In the Middle East, Saudi Arabia can expect a pocket of fairly intense wet anomalies in the southwest near the Red Sea, while moderately drier conditions are expected further inland and in pockets of Yemen. Extreme to exceptional dry anomalies are forecast along the eastern coast of the Black Sea affecting Turkey and Georgia. Some wet anomalies are possible in Syria.

Moderately drier than normal conditions are expected in Kazakhstan east of the Caspian Sea, as well as in Russia between the Ural Mountains and the Central Siberian Plateau and in the Ural River watershed near Kazakhstan. Moderate wet anomalies are forecast for northeastern Kazakhstan and across the border into Russia.

In South Asia, exceptionally drier than normal conditions are expected in southwestern India along the Arabian Sea, with moderate conditions straddling Andhra Pradesh and Karnataka. Primarily mild wet anomalies are forecast in central India and north-central Bangladesh. Southeast Asia will see relatively normal precipitation, with moderate dry anomalies in eastern Cambodia and more intense anomalies in southernmost Myanmar and peninsular Thailand. Northern Sumatra and northeastern Borneo will be moderately wetter than normal.

Moderate wet anomalies are forecast for China's Yellow River watershed as well as parts of the Yangtze River watershed. A vast block of exceptional wet anomalies is forecast for northern Tibet, with dry anomalies skirting southern Tibet. South Korea is forecast to be moderately drier than normal. Some primarily mild wet anomalies are expected in eastern Honshu, Japan.

Western Australia will be moderately drier than normal, particularly the southwestern tip, but primarily mild dry anomalies are forecast elsewhere in the country.

In the West, central Quebec, Canada will be moderately drier than normal. In the US, moderate wet anomalies are forecast for the Upper Midwest and southern Rockies, trailing into Sonora, Mexico. Some areas of primarily moderate dry anomalies are expected in Mexico's southern Gulf states and pockets of northern Central America.

Further south, mild wet anomalies are forecast for Panama. Wet anomalies ranging from mild to severe are forecast in Colombia. Some mild wet anomalies are forecast for Venezuela and scattered pockets across northern Brazil. Central Chile is expected to be moderately drier than normal with conditions reaching across the border into Argentina.

Though Europe is forecast to get some relief from the exceptional heat anomalies of the past month, moderate anomalies are expected overall, with severe anomalies in Northern Europe, Eastern Europe, and European Russia. 

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.

Across northern Africa warm anomalies are forecast, ranging from moderate to exceptional. But it is Madagascar that jumps out on the map, flaring deep red, indicating exceptionally hotter than normal temperatures. Intense heat anomalies are also expected in northeastern South Africa into southern Mozambique, westernmost Democratic Republic of the Congo (DRC), and the Ethiopian Highlands. Moderate to severe warm anomalies are forecast in a mottled pattern across southern African nations and pockets of East Africa. Areas predicted to be cooler than normal include South Sudan and southern DRC.

In the Middle East, intense warm anomalies will dominate Saudi Arabia, Bahrain, Qatar, United Arab Emirates, Kuwait, Iraq west of the Euphrates, and Jordan. Warm anomalies of varying severity are forecast for Iran and southern Turkey including pockets of exceptional intensity. Primarily moderately warmer than normal conditions are expected near the Mediterranean, and moderate to severe conditions in Yemen.

Cool anomalies are forecast for much of eastern Kazakhstan including much cooler than normal conditions in the northeast and into Russia. Northeastern Kyrgyzstan will be moderately cooler than normal. Moderate warm anomalies are expected in Tajikistan.

In South Asia, southern India and Sri Lanka will see intense warm anomalies, and nearly as intense in India's Far Northeast. A path of moderate cool anomalies is forecast stretching across the center of the country. A pocket of exceptionally cooler than normal conditions is forecast along the northern border of Uttar Pradesh and Bihar just south of central Nepal.

Moderate to severe warm anomalies are forecast for much of Southeast Asia, central Philippines, and West Papua, Indonesia.

Southern China will be warmer than normal, with a vast stretch of exceptional anomalies from the eastern Tibetan Plateau reaching south into Yunnan.

Moderate warm anomalies will cover nearly all of Australia with some severe pockets, and extreme conditions north of Brisbane.

The US Northeast is forecast to be warmer than normal with anomalies reaching extreme intensity. Moderate to severe heat anomalies are expected in the Upper Midwest, fanning throughout a vast area in Canada through Ontario, southern Quebec, and into the Maritimes. British Columbia will be moderately warmer than normal. Back in the US, a pocket of exceptional warm anomalies is forecast in central Louisiana, surrounded by moderate conditions. Some moderate warm anomalies are also forecast in the West and in Florida.

Northwestern Mexico is forecast to be cooler than normal, though conditions in Baja will be warmer. Much warmer than normal conditions are forecast in Nayarit on the west coast, downgrading through Jalisco. Southern Mexico, the Yucatan, parts of Central America, and western Cuba will be warmer than normal with anomalies ranging from moderate to isolated pockets of extreme conditions.

In South America, warm anomalies are forecast for eastern Brazil, reaching severe to extreme or exceptional intensity in the easternmost states and in Tocantins. Fairly intense warm anomalies are expected in southwestern Peru, northern Chile, southwestern Bolivia, and northwestern Argentina. Primarily moderate warm anomalies are forecast for pockets of Colombia, central Ecuador, and French Guiana. Conditions in northern Bolivia are expected to be cooler than normal.

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 September 4, 2018 which includes forecasts for September 2018 through May 2019 based on NOAA CFSv2 forecasts issued August 25 through August 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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