Global Precipitation & Temperature Outlook for May 2017

3 May 2017

As in many other recent months, extreme temperature anomalies are predicted in May for many parts of the world, this month with particular extent and severity in southern Myanmar and western India. Exceptional wet anomalies are predicted for East Africa, a region that has been in the grip of dry conditions.

Precipitation Outlook
With a few notable exceptions, the precipitation anomalies forecast for May - both dry and wet - are expected to be primarily moderate in severity. However, the dark blue area in East Africa calls attention to a band of exceptional wet anomalies reaching from southeastern Ethiopia through much of eastern Kenya, winding into central Tanzania and radiating outward in Tanzania with lesser intensity. Exceptional wet anomalies are also forecast for Lake Victoria in southeastern Uganda, surrounded by severe to extreme wet anomalies. Severe to isolated exceptional dry anomalies are forecast for eastern Myanmar, western Bhutan, and Australia's southwestern tip south of Perth.

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 wet anomalies are expected in Africa stretching across the Sahel in eastern Mali, Niger, Central African Republic, and becoming severe across central Sudan and into Eritrea. Elsewhere in Africa, primarily moderate wet anomalies are forecast along Nigeria's coast and into southern Cameroon, trailing southward. Eastern Zambia is also expected to experience moderate to severe wet anomalies.

Moderate to severe wet anomalies are forecast in western Saudi Arabia; moderate wet anomalies are forecast in much of Iraq, an east/west band across the middle of Afghanistan into northern Pakistan, northern India, and scattered across western China. Moderate dry anomalies are forecast for parts of southern India; moderate to extreme dry anomalies are forecast across Myanmar into China; and primarily moderate dry anomalies are expected across much of the southern half of the island of New Guinea. In Australia, moderate dry anomalies are forecast for much of the western half of the country and into Victoria in the southeast.

In the West, moderate to extreme wet anomalies are forecast for the US Northeast, particularly Maine. Primarily moderate wet anomalies are expected to extend across the border into Canada and reach west through Michigan, as well as in western Montana. Some moderate dry anomalies are forecast for southeastern Georgia.

In South America some scattered moderate dry anomalies are expected in central Brazil, and anomalies of slightly greater severity are forecast in an arc from southern Peru through southwestern Bolivia. Moderate wet anomalies are forecast for Paraguay, central Ecuador, north-central Colombia, and parts of Venezuela.

Temperature Outlook
Southern Myanmar is forecast to be exceptionally hotter than normal, with similar conditions reaching into northwestern Thailand, northern Cambodia, and southernmost Yunnan, China. Much of southern and western India, too, is expected to be warmer than normal, especially eastern Gujarat and western Maharashtra, where anomalies may be exceptional. Extreme to exceptional warm anomalies are also forecast for a vast stretch of northern Far East Russia, western Sahara in Africa, and eastern and southern Greenland.

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.

Moderate to severe warm anomalies are forecast for Indonesia which may reach exceptional severity in western Papua. Much of the eastern half of China, central and eastern Mongolia, the Korean Peninsula, and Japan are forecast to be warmer than normal with moderate to extreme anomalies.

Northern Africa is forecast to be warmer than normal, especially the western region as mentioned previously, and warm anomalies will extend into the northern half of Sudan. Moderate to extreme warm anomalies are also forecast for South Africa, northeastern Madagascar, and scattered along coastal regions of West Africa. A band of severe to exceptional cool anomalies is forecast across southern Democratic Republic of the Congo, and cool anomalies of generally lesser severity are expected in northern Kenya and southeastern Ethiopia. Extreme warm anomalies are forecast in eastern Saudi Arabia. Qatar and parts of the United Arab Emirates are expected to be much hotter than normal. Primarily moderate warm anomalies are forecast for Turkey.

Much of Europe is expected to be warmer than normal, with severe anomalies in France and Ukraine, and extreme anomalies in southern Italy.

Moderate to severe warm anomalies are forecast for South America's northern half, with some pockets of extreme warm anomalies in central and far eastern Brazil, and through the Andes in Colombia, Peru, and northern Chile. 

Temperatures throughout most of Alaska are expected to be warmer than normal ranging from moderate to extreme.

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 May 3, 2017 which includes forecasts for May 2017 through January 2018 based on NOAA CFSv2 forecasts issued April 24 through April 30, 2017.

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.



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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