Global Precipitation & Temperature Outlook October 2018

2 October 2018

OVERVIEW
Warmer than normal temperatures are forecast for a vast stretch of Russia east of the Ural Mountains, through the Central Siberian Plateau and leading south to the Sea of Japan, where anomalies will be intense. Similar conditions are expected across the border in China’s Northeastern Plain. The US Southwest can expect much wetter than normal conditions.

PRECIPITATION OUTLOOK
Noteworthy in the precipitation outlook is the forecast of significant wet anomalies in the US Southwest ranging from moderate to extreme. Extreme conditions are expected in Arizona with anomalies less intense radiating into neighboring states. Wet anomalies are also forecast for the Upper Midwest, which will be primarily moderate but may be severe in North Dakota and northeastern Wisconsin.

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.

Moderate wet anomalies will reach across the US northern borders into Canada, while moderate to extreme dry anomalies are forecast in far northwestern Canada stretching across the Brooks Range in northern Alaska.

Much of northwestern Mexico will be somewhat wetter than normal, from Chihuahua westward through the northern half of the Baja Peninsula where anomalies are expected to be extreme. A pocket of fairly intense dry anomalies is forecast for east-central Nicaragua.

In South America, moderate dry anomalies are forecast for southeast Brazil, with moderate wet anomalies in the south (Santa Catarina and Rio Grande so Sul) leading into northern Uruguay. Wet anomalies of varying intensity are expected in a broad arc around the continent from eastern Venezuela through Colombia, eastern Ecuador, and northern Peru. Northeastern Argentina will be moderately wetter than normal. Some pockets of intense dry anomalies are forecast for Venezuela’s north-central coast, northwestern Ecuador, central Bolivia near Cochabamba, and central Salta Province in northwestern Argentina.

In Africa, central and eastern Ethiopia are expected to be drier than normal, as will a band across Central African Republic into Cameroon. Areas where wetter than normal conditions are forecast include: western Libya into southeastern Algeria, Morocco, Mauritania, western Senegal, Ghana, northwestern Nigeria, southeastern Gabon, southeastern Democratic Republic of the Congo (DRC), and northwestern Tanzania.

Wet anomalies are forecast for northern India and parts of western India, central Pakistan, and central Afghanistan. Anomalies could be extreme in northern India. Severe to extreme dry anomalies are expected in central Bangladesh and parts of India’s Far Northeast.

Conditions in Russia will be moderately wetter than normal in the Central Siberian Plateau. Moderate to exceptional wet anomalies are forecast for the Yangtze River Basin in China and in a band across the Tibetan Plateau. Some dry anomalies are expected in northern Qinghai and the Lower Reaches of the Yellow River Basin. Wet anomalies are forecast for southern Japan.

Dry anomalies are forecast for central Vietnam, Philippines, pockets of the Malay Peninsula, and southern Sumatra. Wetter than normal regions include Malaysian Borneo, northern Sulawesi, and New Guinea’s “Bird’s Head” Peninsula in the west.

In Australia, dry anomalies will reach extreme intensity in Tasmania, and severe intensity in Victoria. Western Australia will be much wetter than normal.

TEMPERATURE OUTLOOK
Much of Russia east of European Russia will be warmer than normal with anomalies reaching severe or extreme intensity in eastern regions near China where anomalies of similar intensity are forecast for the Northeast Plain. Severe warm anomalies are forecast for much of Japan. Primarily moderate warm anomalies will extend from Central Asia across Mongolia, along with pockets across China’s northern half.

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.

Southeast Asia and Indonesia are expected to be much warmer than normal with anomalies reaching extreme and exceptional intensity, particularly in Thailand and Sumatra.

Warm anomalies are forecast for Australia and may be intense in Tasmania and in the northwest quadrant of mainland Australia.

Much of India’s southern half will be moderately warmer than normal, as will Sri Lanka, but anomalies may be extreme in eastern Karnataka down through Kerala. Cooler than normal conditions are forecast for Bhutan, Nepal, and in India south of Nepal where anomalies may be exceptional. Central Rajasthan and western Jammu and Kashmir will also be cooler than normal. A pocket of fairly intense warm anomalies is forecast in Afghanistan near Kabul.

In the Middle East, southwestern Iran will be exceptionally warmer than normal, as will southern Iraq. Anomalies ranging from severe to exceptional are forecast for much of the Arabian Peninsula and for Iraq west of the Euphrates River.

Relatively normal conditions are expected in Europe but moderate to severe warm anomalies are forecast for the western Iberian Peninsula.

In Africa, warm anomalies reaching exceptional intensity will stretch across much of the Sahel. Other areas of intense warm anomalies include: Eritrea, the Ethiopian Highlands and eastern Ethiopia, northwestern Kenya, the border of Nigeria and Cameroon, and from coastal Guinea through Sierra Leone and Liberia. Areas of generally less intense warm anomalies include: western and northern Madagascar, southern Kenya into northern Tanzania, South Africa, western Angola, and around the Gulf of Guinea. Eastern Sudan is expected to be much cooler than normal, as is a pocket in south-central DRC in northern Katanga.

In South America, Brazil’s eastern half will be warmer than normal with anomalies reaching extreme intensity in some pockets, including São Paulo. Exceptional warm anomalies are also forecast for southwestern Bolivia into northwestern Argentina, and a pocket in the southern Atacama Desert. Moderate warm anomalies are forecast for parts of Colombia, south-central Peru, northern Chile, and Paraguay. Many regions of Argentina are expected to be cooler than normal, as is north-central Venezuela.

Warm anomalies of varying intensity are forecast for southern Mexico and much of central America, with exceptional anomalies in eastern Nicaragua and in Nayarit on Mexico’s Pacific Coast. Cooler than normal temperatures are expected in coastal and central Sonora, Mexico.

Moderately warmer than normal conditions are expected in the US in a block east of the Mississippi through Virginia and south through Florida, where conditions may be severe. Moderate to severe warm anomalies are forecast in the Southern Rockies. Alaska will be much warmer than normal, with exceptional anomalies in the Seward Peninsula and to the north.

In Canada, moderately cooler than normal temperatures are forecast for the Prairie Provinces and regions around Hudson Bay.

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 October 2, 2018 which includes forecasts for October 2018 through June 2019 based on NOAA CFSv2 forecasts issued September 24 through September 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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