Overall for April 2016, as in recent months, it is the temperature forecast which dominates the Outlook with exceptionally hotter temperatures expected across vast stretches of the world. (For data sources see "Special note" and "About this blog post" below.)
It is not just that warm anomalies are forecast, but that in many regions these anomalies are expected to be exceptional and widespread. Exceptionally hotter temperatures - with an expected frequency of occurrence greater than 40 years - are indicated in dark red.
Note the expanse of exceptional anomalies stretching from southern Alaska down through Canada's Yukon Territory and British Columbia, then continuing into Washington and Oregon. Likewise, bright red lights up parts of Central America, traces a wide path down much of the Pacific coast of South America, and encompasses the Amazon Basin. Other countries where exceptionally hotter temperatures are forecast to be particularly widespread include: Niger, Somalia, India, Sri Lanka, Thailand, Laos, Cambodia, Vietnam, Malaysia, Indonesia, China, Taiwan, and Australia. Moderate to exceptional anomalies are forecast for many other parts of the world.
Exceptionally wetter conditions - shown in dark blue - are forecast for northern Argentina, southern Yunnan province in China, Shanghai in the east, northern Heilongjiang and across the border into Russia. Moderate to exceptional precipitation surpluses are expected in: Colombia, Uruguay, the southern Arabian Peninsula, central Tanzania, eastern Tajikistan, and a wide east-west band across southern Russia.
Central and eastern Brazil are forecast to be drier than normal, exceptionally drier in some areas, as noted in the dark red patches. Other regions with deficit precipitation anomalies forecast include: Finland and northwestern Russia; eastern Kenya, southern Somalia, southern Ethiopia; southern India; Sri Lanka; Southeast Asia; Hainan (China); and the Philippines.
Special note regarding April 4, 2016 edition of Outlook:
Effective March 28, 2016 NOAA changed the initialization procedure for CFSv2 to address issues with unrealistically cold sea surface temperatures in the tropical Atlantic ocean. As a result, this month's Outlook is based on an ensemble of 14 CFSv2 forecasts issued after this fix was implemented instead of the normal 28. For more information see http://www.nws.noaa.gov/os/notification/tin16-09cfs.htm and http://www.nco.ncep.noaa.gov/pmb/changes/downloads/CFSv2_Atlantic_cold_bias_problem.pdf.
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 April 4, 2016 which includes forecasts for April 2016 through December 2016 based on NOAA CFSv2 forecasts issued March 25 through March 31, 2016.
- 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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