The precipitation outlook for August indicates large areas of exceptionally wetter and large areas of exceptionally drier conditions. Much of the western half of the United States may be moderate to exceptionally wetter than normal in August, shown in the widespread blue hues in the Precipitation map below. (For data sources see "About this blog post" below.) Precipitation surpluses may also stretch in an eastward band of the central US and south into Mexico's northwestern states. Other areas likely to see wetter than normal conditions include: central and southern Brazil, Bolivia, Paraguay, parts of Argentina, Spain, northwestern Africa, Tajikistan and neighboring states, and Western Australia.

Exceptionally drier conditions may dominate a large region from eastern and central Mexico through the Pacific Coast of Central America and into Colombia, Venezuela, Guyana, Suriname, French Guiana, and northern Brazil. Moderate to exceptionally drier conditions are also expected in: central Ethiopia, central India, Nepal, Thailand, Laos, Cambodia, Malaysia, Indonesia, Papua New Guinea, Philippines, Taiwan, and southeastern China.

Precipitation outlook for August 2015. 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.

Predominately warmer than average temperatures are forecast globally in August, as shown in the Temperature map below. In the Western Hemisphere moderate to exceptionally warmer temperatures are expected in Alaska, Western Canada, the US Pacific Coast, the US Southeast, the Baja Peninsula and southward along Mexico's Pacific coastline, and in the Yucatan Peninsula. The Caribbean, Central America, and much of South America may also be affected.

In Africa severe to exceptionally warmer than average temperatures are expected in the Saharan region, Somaliland, southern Somalia, southern Kenya, and eastern Madagascar. Other hotspots in the forecast include: Saudi Arabia, the southern half of Iraq, Jordan, Syria, eastern Turkey, Georgia, the southern half of India, Sri Lanka, southern Myanmar, Thailand, Laos, Cambodia, Vietnam, Malaysia, Indonesia, Papua New Guinea, and Australia.

Temperature outlook for August 2015. 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.

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 July 23, 2015 which includes forecasts for August 2015 through April 2016 based on NOAA CFSv2 forecasts issued July 15 through July 21, 2015.

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 2008Chen 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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