The December 2015 Outlook indicates the presence of exceptional anomalies in the forecasts for both precipitation and temperature. The temperature forecast, however, continues to dominate the narrative. (For data sources see "About this blog post" below.)
As 2015 winds down, the December temperature forecast indicates exceptional and persistent heat, consistent with preceding months and culminating in what will most likely be a record-setting year. Oranges and reds light up the forecast (first map below) indicating moderate to exceptional heat anomalies. Note the vast expanse of anomalies across the northern latitudes. In the north exceptional anomalies (greater than 40 years return period) are expected in: Ontario and Quebec, Canada; the Great Lakes Region and the Northeast United States; and a large chunk in Russia's boreal forest including Siberia.
Likewise, deep reds pull our attention to widespread exceptional heat anomalies in: Central America and the Caribbean; along the Pacific coast of South America and in Brazil's Amazon; coastal West Africa, South Africa, Madagascar, parts of Ethiopia and Yemen; India, Sri Lanka, Southeast Asia, Indonesia, Malaysia, and the Philippines.
Exceptionally cooler temperatures are expected in Central African Republic and South Sudan.
Northern Brazil pops out in December's precipitation forecast map (below), with oranges and reds indicating widespread dry anomalies that reach into Bolivia and Suriname. Dry anomalies are also forecast for: northern Wisconsin, US; southern Europe; West Africa and southwestern Madagascar; and, New Guinea.
Exceptionally wetter conditions, shown in deep blue, are expected in: south/central Florida, US; Central African Republic, South Sudan, Tanzania, Uganda, southwestern Ethiopia; Yunnan, Guizhou, and Hunan in southern China; far eastern Mongolia and across the border into China through Heilongjiang; and, north of Lake Baikal, Russia. Wet anomalies are also forecast for: Mexico's Yucatan Peninsula; Pacific coast Colombia and Ecuador; southern Brazil and central Argentina; Scotland; Norway; Bhutan, Bangladesh, western Myanmar; northern Vietnam, northern Laos, western Thailand; and, Western Australia.
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 December 2, 2015 which includes forecasts for December 2015 through August 2016 based on NOAA CFSv2 forecasts issued November 24 through November 30, 2015.
- 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.