The temperature forecast for October 2015 dominates this month's Outlook. (For data sources see "About this blog post" below.)

Exceptionally hotter than normal conditions are forecast in October for many areas of the world, as is evident in the dark red regions on the map below, with abnormally to moderately warmer temperatures forecast for most of the remaining land area.

Overall, the precipitation outlook for October 2015 (see map below) indicates that parts of northern South America, Malaysia, and Indonesia may see exceptionally drier than normal conditions, while exceptionally wetter than normal conditions are forecast for northern Mexico and parts of East Africa. More detailed analysis is provided in the following paragraphs.

Moderate to exceptional precipitation deficits are forecast for Guatemala, Belize, El Salvador, Honduras, Nicaragua, Jamaica, and Haiti. In South America notable deficits are expected from Venezuela through much of Brazil, and in southern Chile. Elsewhere severe to exceptional deficits are forecast for: Bhutan, Malaysia, southern Sumatra, Java, Borneo, Sulawesi, New Guinea, and in Victoria, Australia; Tasmania; and North Island, New Zealand. Moderate dry conditions are expected in: central Ethiopia and nearby South Sudan, central India and eastern Nepal, and western Sri Lanka.

Surpluses are expected in the Central US from the Northern Plains down through much of northern Mexico, and in South Carolina. In South America, coastal regions of Colombia and Ecuador may experience moderate surpluses as well as central Paraguay, the southern tip of Brazil, and southern Argentina. Portugal and western Spain may see wetter than normal conditions. A wide band of surpluses is forecast from Turkey eastward through Syria, Georgia, Armenia, Azerbaijan, Iraq, Iran, Turkmenistan, Tajikistan, then northwards through eastern Kazakhstan into Russia. Moderate to exceptional surpluses are expected in parts of East Africa, particularly eastern Kenya and southern Somalia. Thailand, Laos, Cambodia, Vietnam, and Hainan, China may also experience moderate to severe surpluses.

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 October 5, 2015 which includes forecasts for October 2015 through June 2016 based on NOAA CFSv2 forecasts issued September 24 through September 30, 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 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.