Global Precipitation & Temperature Outlook May 2018

2 May 2018

OVERVIEW
The May Outlook indicates wetter than normal conditions in East Africa, Uruguay, and Bangladesh. Much warmer than normal temperatures are expected in India, Egypt, Sudan, and Northeast China.

PRECIPITATION OUTLOOK
Wet anomalies are forecast for parts of East Africa including central Tanzania, eastern Kenya and along its western border with Uganda, southern Somalia, and eastern Ethiopia. Anomalies could be extreme -  beyond a 20-year return period - in pockets of central Tanzania. Wetter than normal conditions are also expected in Zambia, Malawi, southern and central Democratic Republic of the Congo, Equatorial Guinea, Gabon, southern Congo through DRC and into Angola, and farther north in southern Central Africa Republic, southern Sudan, South Sudan, and western Eritrea. Conditions may be especially intense in the Lower Congo region of DRC.

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.

In the Middle East moderately wetter than normal conditions are forecast throughout Iraq and into northeastern Syria and northwestern Iran. Wet anomalies ranging from moderate to extreme (a return period of 20-40 yrs) are expected in eastern Turkey. 

Conditions in Europe are expected to be relatively normal though Corsica, Sardinia, and central Italy will be wetter than the norm (a return period of 10-20 yrs), and mild wet anomalies are forecast for mainland Greece. Somewhat drier than normal conditions are expected in the Caucasus and in the Don River Basin of European Russia.

In Central Asia, western Kazakhstan will be somewhat drier than normal but northern and eastern regions will be moderately wetter, reaching across the northeastern border into Russia. 

Northeastern China stands out in East Asia with a forecast of moderate to severe dry anomalies. Some moderate dry anomalies are also forecast for pockets of Mongolia. Central Tibet is expected to be somewhat wetter than normal as is Shandong near the Bohai Sea.

In South Asia, some scattered, moderate dry anomalies are forecast for Pakistan and western India, with more severe conditions expected in northwestern Bhutan. Eastern Nepal and Bangladesh will be wetter than normal, including the area between them in India where anomalies may be severe.

Relatively normal precipitation is forecast for Southeast Asia, the Pacific, Australia, and New Zealand.

In South America, moderate to severe wet anomalies are forecast for Colombia; central Ecuador; Loreto, Peru in the north, and in a line following the Cordillera Central Mountains and drifting eastward towards Cusco; Acre. Brazil; and northern Argentina through Uruguay. A few pockets of moderate dry anomalies are expected in central and eastern Brazil but conditions surrounding the State of Paraíba in the easternmost tip may be extreme. Southern Altacama, Chile will be moderately drier than normal.

Moderately wetter than normal conditions are forecast for southern Mexico, becoming mild in Guatemala.

Arizona and Southern California are expected to be moderately drier than normal.

TEMPERATURE OUTLOOK
Central and western India jump out on the temperature map with a forecast of exceptionally warmer than normal temperatures (a return period of 40+yrs). These conditions are also expected to reach into Pakistan. Cooler than normal temperatures are forecast in eastern Nepal,across the border into India, and in Bangladesh. Severe warm anomalies are forecast for northern, southern, and Far East India, with moderate anomalies in northern Sri Lanka. 

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.

A large block of exceptionally warmer than normal temperatures is forecast in Africa covering much of Egypt as well as northern Sudan into Eritrea, southeastern Libya, and northern Chad. Anomalies of slightly lesser intensity cover much of Niger and the remainder of Libya. Moderate to severe warm anomalies are forecast for West Africa from Guinea through Gabon. South Africa is forecast to be moderately warmer than normal. Much cooler than normal temperatures are expected in southern DRC. Cool anomalies are also forecast for eastern Ethiopia into Somalia, southern South Sudan, eastern Uganda, and northern Kenya. 

In the Middle East, warm anomalies are forecast for many parts of the Levant and the Arabian Peninsula, along with Turkey, Georgia, and southern Iran. Anomalies are expected to be especially intense in Cyprus, Lebanon, Israel, Georgia, Qatar, easternmost Oman, and across the Gulf of Oman along Iran's southern shore.

Central Europe, Scandinavia, and the Baltics will be moderately warmer than normal, but conditions in Eastern Europe, the western Balkans, and southern Italy may be severe.

Warmer than normal temperatures are forecast for Russia's eastern half, and anomalies may be exceptional near Vladivostok. 

Likewise, severe to exceptional warm anomalies are expected in Mongolia's eastern half and into Northeast China, Inner Mongolia, and Qinghai, along with anomalies of generally lesser intensity in western, southern, and southeastern China. Severe to extreme warm anomalies are forecast for the Korean Peninsula and Japan. 

Severe warm anomalies are expected in Malaysia, Indonesia, Papua, eastern Australia, and South Island, New Zealand. 

Parts of northern South America will see moderately warmer than normal temperatures, though anomalies may be much more intense in a pocket of central Brazil.

Severe warm anomalies are forecast for northern Mexico; cool anomalies in the south; and moderate warm anomalies in southern Guatemala.

In the US, intense warm anomalies are expected in the Northeast and northern Louisiana. Moderately warmer than normal conditions are forecast east of the Mississippi, and in the South and Southwest. Intense warm anomalies are forecast for Alaska and well into western Canada; moderately warmer than normal temperatures are forecast for southern Ontario and southern Quebec. Conditions in Nova Scotia could be exceptionally warmer than normal.

NOTE ON ADMINISTRATIVE BOUNDARIES
There are numerous regions around the world where country borders are contested. ISciences depicts country boundaries on these maps solely to provide some geographic context. The boundaries are nominal, not legal, descriptions of each entity. The use of these boundaries does not imply any judgement on the legal status of any territory, or any endorsement or acceptance of disputed boundaries on the part of ISciences or our data providers.

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 2, 2018 which includes forecasts for May 2018 through January 2019 based on NOAA CFSv2 forecasts issued April 24 through April 30, 2018.

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.

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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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