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Climate forecasts and outlooks provide valuable information to decision makers. Water managers, for example, consult streamflow forecasts to allocate water to irrigation districts and ranchers review precipitation and drought forecasts to help decide if fields will produce healthy grasses.
Most forecasts and outlooks are based on expectations of future temperature and precipitation deroved from long-term climate trends, the current and anticipated state of tropical sea surface temperatures, sophisticated computer models, expert judgments, and other diagnostic tools. No forecast or outlook, however, is imperfect. As a result, they are often presented in probabilistic terms.
There are many forecasts and outlooks produced and available on the Web. Below is a list of several common products.
Temperature and precipitation seasonal outlooks
NOAA’s Climate Prediction Center (CPC) publishes on the third Thursday in each month one-month and seasonal outlooks for temperature and precipitation. Seasonal outlooks correspond to three month periods and are generated two weeks to 13 months in advance of the season. In both the one-month and seasonal forecasts, Information is presented in probabilities, or chances, that conditions in the period will be above-average, near average, and below-average compared to the 1971–2000 period.
Seasonal Drought Outlook
The CPC produces a seasonal drought outlook that depicts drought conditions in a three-month period that follows the month of the issue date (Figure 1). For example, the seasonal drought outlook issued in January covers the period February–April. Affected areas are defined subjectively and are based on expert assessment of numerous indicators, including outputs of short- and long-term forecasting models. The CPC produces maps and a detailed discussion that highlights drought conditions in different regions.
El Niño–Southern Oscillation (ENSO) forecast
The International Research Institute for Climate and Society (IRI) generates a probabilistic ENSO forecast for overlapping three month seasons (Figure 2). The forecast expresses the probabilities of the occurrence of sea surface temperatures that resemble El Niño, La Niña, and Neutral conditions in the ENSO-sensitive Niño 3.4 region. The ENSO forecast is a subjective assessment of current model forecasts of Niño 3.4 sea surface temperatures that are made monthly.
The National Water and Climate Center (NWCC) part of the USDA National Resources Conservation Service produces forecasts for streamflow volumes that would occur naturally without any upstream influences, such as reservoirs and diversions. The NWCC provides forecasts for numerous exceedence levels. For example, a forecast may state that there is a 30, 50, and 70 percent chance that streamflows with be 150, 100, and 75 percent of average, respectively. The percentages change depending on the season and current and expected conditions. The NWCC only produces streamflow forecasts for Arizona between January and April and between January and May for New Mexico.
Wildland Fire Outlook
The National Interagency Coordination Center at the National Interagency Fire Center publishes a seasonal wildland fire outlook each month. The Outlook covers the three month period following the month of publication and includes a map and discussion of the forecast. The forecasts consider observed climate conditions, climate and weather forecasts, vegetation health, and surface-fuels conditions in order to assess fire potential for fires greater than 100 acres. They are subjective assessments that synthesize information provided by fire and climate experts throughout the U.S.