Drought

The IRI has worked in collaboration with the NOAA Earth System Research Laboratory (ESRL) and Climate Prediction Center (CPC) to develop a set of tools that provide probabilistic forecasts of future Standardized Precipitation Index (SPI) as an indicator of drought for various accumulation periods over the U.S. and Mexico based upon two forecast methodologies.

In addition to the SPI forecast tools, analyses of observed precipitation conditions using monthly SPI are provided, based upon monthly totals from the CPC's global Unified gridded precipitation dataset.

U.S. - Mexico
This map shows values of the monthly Standardized Precipitation Index (SPI) for a user-selected accumulation period (3, 6, 9, or 12-month) over the United States and Mexico, based upon observed monthly precipitation totals from the Climate Prediction Center's (CPC) Unified global precipitation dataset (combined retrospective and real-time). The SPI maps provide an indication of short-term to longer-term wet (green, positive SPI) or dry (yellow to red, negative SPI) conditions based upon precipitation alone. The negative half of the color scale uses the same colors and thresholds of SPI corresponding to the percentiles associated with the D0 (30%tile) to D4 (2%tile) drought intensity categories used in the U. S. Drought Monitor.
This tool displays maps of probabilistic forecasts of drought over the U.S. and Mexico using a forecast of the Standardized Precipitation Index (SPI; 3, 6, 9, or 12-month accumulation periods) in future months based upon forecast precipitation from the IRI Multi-Model Ensemble and the SPI Persistence methods. These maps provide quantifiable, probabilistic drought predictions for the United States and Mexico over the next few months.
This tool displays maps of probabilistic forecasts of drought over the U.S. and Mexico using a forecast of the Standardized Precipitation Index (SPI; 3, 6, 9, or 12-month accumulation periods) in future months based upon the SPI Persistence method. These maps provide quantifiable, probabilistic drought predictions for the United States and Mexico over the next few months.
U.S. Climate Divisions
This map shows values of the monthly Standardized Precipitation Index (SPI) for a user-selected accumulation period (3, 6, 9, or 12-month) over the continental United States, based upon observed monthly precipitation totals from the U. S. nClimDiv Version 1 dataset. The SPI maps provide an indication of short-term to longer-term wet (green, positive SPI) or dry (yellow to red, negative SPI) conditions based upon precipitation alone. The negative half of the color scale uses the same colors and thresholds of SPI corresponding to the percentiles associated with the D0 (30%tile) to D4 (2%tile) drought intensity categories used in the U. S. Drought Monitor.
This tool displays maps of probabilistic forecasts of drought in U.S. Climate Divisions using a forecast of the Standardized Precipitation Index (SPI; 3, 6, 9, or 12-month accumulation periods) in future months based upon forecast precipitation from the IRI Multi-Model Ensemble and the SPI Persistence methods. These maps provide quantifiable, probabilistic drought predictions for the United States over the next few months.
This tool displays maps of probabilistic forecasts of drought in U.S. Climate Divisions using a forecast of the Standardized Precipitation Index (SPI; 3, 6, 9, or 12-month accumulation periods) in future months based upon the SPI Persistence method. These maps provide quantifiable, probabilistic drought predictions for the United States over the next few months.