Several climate indicators are used to monitor drought in the United States. These indicators include:

• the Palmer Z Index, Palmer Drought Severity Index, and Palmer Hydrological Drought Index

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• the one-month, two-month, three-month, six-month, nine-month, 12-month, and 24-month Standardized Precipitation Index

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• maps showing the percent of normal precipitation for airport stations for the current month and year-to-date

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• the statewide precipitation ranks for current month (short-term) and 3-months, 6-months, and 12 months (longer-term)

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• the percent of normal precipitation maps, based on Cooperative Network and other station reports, provided by the NOAA Regional Climate Centers (HPRCC)

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• the short-term surface wetness anomaly map computed by the National Climatic Data Center from the Special Sensor Microwave Imager (SSMI), a polar orbiting satellite with global coverage

  larger image The surface wetness anomaly map shows areas of above and below average liquid precipitation wetness. During the winter months, it should be used in conjunction with the snow cover anomaly map.

  larger image The snow cover anomaly map shows areas of above and below average frozen precipitation "wetness". An area with above-average snow cover may appear to have below-average liquid wetness.

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• NOAA satellite observations of vegetation health are most effective during the warm season months. However, even at this time of year, the VHI from early April revealed stress on vegetation from the southern Great Lakes into the central Plains

• modeled runoff, evaporation, and soil moisture conditions as calculated by the National Weather Service

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• the percent of average precipitation map for the water year to date for the SNOTEL stations in the western mountains provided by the Western Regional Climate Center

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• the percent of average snow water content map for the SNOTEL stations in the western mountains provided by the Western Regional Climate Center

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• the April 1 mountain snow course snowpack observations made by the USDA Natural Resources Conservation Service

• the USGS March daily streamflow and monthly mean streamflow maps