Global Precipitation & Temperature Outlook May 2019

3 May 2019

OVERVIEW
The May Outlook includes a forecast of exceptional warm anomalies in a number of places including northern Alaska; the State of São Paulo, Brazil and through the Andes from Colombia through northern Chile; and, around the Gulf of Guinea in Africa. Central Tanzania is expected to be much wetter than normal. Widespread, moderate to severe wet anomalies are forecast in a broad path in the U.S. from Michigan through Louisiana.

PRECIPITATION OUTLOOK
In North America, some moderate dry anomalies are forecast in far eastern Quebec, Canada at the Gulf of St. Lawrence. In the U.S., as previously stated, widespread moderate to severe wet anomalies are expected to form a broad path from Michigan to the Gulf, encompassing states on both sides of the Lower and Middle Mississippi River, reaching through the Ohio River Basin and into the Northeast as far as southern Maine. Severe anomalies will be particularly widespread in Missouri. Affected states include Kansas, Iowa, Missouri, Illinois, eastern Oklahoma, Arkansas, northeastern Texas, northern Louisiana, Mississippi, northern Alabama, Tennessee, Kentucky, Indiana, Ohio, Michigan, West Virginia, New York, Vermont, New Hampshire, western Massachusetts, and southern Maine.

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.

Wet anomalies ranging from moderate to extreme are forecast for Utah and into neighboring Colorado and Nevada, with milder anomalies in Idaho and Montana.

Mexico’s southern Pacific region is expected to be moderately drier than normal in Michoacán and Guerrero. Conditions may be slightly drier in a few pockets of Veracruz along the Gulf of Mexico. Some primarily moderate wet anomalies are forecast for pockets of Central America, and extreme wet anomalies in northwestern Colombia. Across South America’s central girth, conditions are expected to be somewhat wetter than normal with moderate to severe anomalies from Bolivia though Paraguay, and in a broad band across nearby Brazilian states to the Atlantic, including the State of São Paulo. Wet anomalies will also trace a path through Peru’s Cordillera Central Mountains, reaching past La Paz. Some intense dry anomalies are expected in Brazil’s easternmost tip, particularly in Pernambuco.

In Africa, wetter than normal conditions are forecast for Tanzania, northern Mozambique, Malawi, and northern Zambia with extreme to exceptional anomalies in central Tanzania. Wet anomalies are also forecast scattered along the Gulf of Guinea, and will be particularly pervasive from Equatorial Guinea through northernmost Angola and could reach exceptional intensity. The Ethiopian Highlands will be drier than normal with severe to extreme anomalies. Moderately drier than normal conditions are expected in western Kenya, northern Uganda, and northeastern Democratic Republic of the Congo (DRC). Severe dry anomalies are forecast for Guinea and northern Sierra Leone.

Relatively normal conditions are expected in most of Europe. Some wet anomalies are forecast for Finland and northern European Russia. Russia’s Kamchatka Peninsula in the far east will be moderately drier than the norm.

Southern India and Sri Lanka are expected to be moderately drier than normal with some more intense pockets, while wetter than normal conditions are forecast in northern India from the western Gangetic Plain reaching northwest past Delhi and into northern Pakistan. Bhutan will be exceptionally drier than normal.

Wet anomalies are expected in the Tibetan Plateau, along China’s southern coast, and in Taiwan.

In Indonesia, dry anomalies are forecast for Borneo and into Sulawesi, and are expected to be extreme in some pockets. Southern Philippines will be much drier than normal, but some wet anomalies are expected in the north. Moderate dry anomalies are forecast across north-central New Guinea, and moderate dry anomalies scattered across southern regions of the island.

Australia’s Top End in Northern Territory will see wetter than normal conditions. Moderate to severe dry anomalies are forecast in the country’s southwestern tip including Perth.

TEMPERATURE OUTLOOK
Warm anomalies are forecast across many parts of northern South America. Anomalies are expected to be exceptional in southern Venezuela into eastern Colombia, western Colombia, central Ecuador, and following the Andes from Peru through western Bolivia and into the Atacama Desert in northern Chile.

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.

Anomalies will also be exceptional in the Brazilian states of Pará, Bahia, and the smaller, easternmost states; and in Goiás, Minas Gerais, and Rio de Janeiro. Severe to extreme anomalies are expected in the Amazon Basin, and severe anomalies in Guyana, Suriname, and French Guyana. Moderate wet anomalies are forecast for western Paraguay.

In Central America, intense warm anomalies are expected in Panama and Costa Rica, and anomalies of lesser intensity in Honduras, El Salvador, and Guatemala. Jamaica and western Cuba will be exceptionally warmer than normal, while moderate to severe warm anomalies are forecast for Haiti and Dominican Republic. Much of Mexico will be warmer than normal as well, with severe anomalies in the northeast; severe to extreme anomalies coast-to-coast across the country’s middle with exceptional anomalies in Michoacán; and, severe to extreme anomalies in the south around the Gulf of Tehuantepec on the Pacific.

In the U.S., conditions will be warmer than the norm from southern Texas through southern Mississippi, Florida, and north along the Eastern Seaboard as far as Delaware. Anomalies will be moderate overall but exceptional in southern Texas and along the state’s Gulf Coast, and in Mississippi and southern Florida. Along the nation’s northern border, moderate cool anomalies are forecast for South Dakota and most of Montana, leading into southern regions of Canada’s Prairie Provinces. Alaska will be much warmer than normal, with exceptional anomalies in the north and severe anomalies around Anchorage.

In Europe, some primarily moderate warm anomalies are forecast in the U.K., Ireland, France, Spain, Portugal, Sicily, Switzerland, Romania, and southern Norway.

Across the Mediterranean in Africa, exceptionally warmer than normal temperatures are expected along the central west coast from Gambia leading around the Gulf of Guinea through southern Nigeria and nearly all of Cameroon, and trailing into northern Angola. Intense warm anomalies are expected across the Sahel with exceptional conditions in northern Sudan and anomalies nearly as intense in Egypt. The Ethiopian Highlands, too, will be exceptionally warmer than the norm, as will pockets of western Kenya, northeastern Madagascar, and northern DRC. A band of cooler than normal conditions is expected across southern DRC leading from Lake Tanganyika along the Lukuga River. Warm anomalies of varying intensity are forecast for southern Africa and will be extreme in southern Botswana and much of central South Africa.

The forecast for the Middle East indicates moderate to severe warm anomalies for Turkey and the Levant. More widespread and intense warm anomalies are expected on the Arabian Peninsula, with exceptional anomalies in Saudi Arabia, United Arab Emirates, and northern Oman. Extreme anomalies are expected in southern Iraq, and moderate anomalies in central Iran and along the Persian Gulf. Anomalies will be also be extreme along the Gulf of Oman in Iran, leading into moderate anomalies in southwestern Pakistan. Turkmenistan and Uzbekistan will be moderately warmer than normal, and far eastern Kyrgyzstan around Issyk-Kul Lake in will be moderately cooler, as will a pocket of northwestern Afghanistan.

The vast expanse of Russia east of the Urals is expected to be warmer than normal especially the Far East, where extreme to exceptional anomalies are forecast around the Sea of Okhotsk and on Kamchatka Peninsula. Severe warm anomalies are forecast for Mongolia and moderate to extreme anomalies in Northeast China. Elsewhere in China, primarily moderate warm anomalies are forecast between the Lower and Middle Reaches of the Yellow and Yangtze Rivers, and moderate to severe anomalies in Tibet.

In South Asia, warmer than normal conditions are expected in southern India with extreme anomalies in Tamil Nadu and Kerala, and extreme to exceptional anomalies in Sri Lanka. Moderate warm anomalies are forecast for India’s Far Northeast and Bangladesh.

Moderately warmer than normal temperatures are also forecast for Southeast Asia. Warm anomalies will be intense in Indonesia and southern Philippines, with exceptionally warmer conditions in southern Sumatra.

Temperatures will also be exceptionally warmer than normal west of Brisbane, Australia, and warm anomalies of lesser intensity will trace a northern arc along much of the continent’s perimeter from Perth through Kimberley Region in Western Australia, across the north, and down a broad path in the east through Tasmania. Exceptional warm anomalies are forecast for South Island, New Zealand.

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, 2019 which includes forecasts for May 2019 through January 2020 based on NOAA CFSv2 forecasts issued April 24 through April 30, 2019.

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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