A strong Madden Julian oscillation shifts east into the equatorial Atlantic/Africa sector and weakens. The heat release pole ward warms the northern latitude mid-atmosphere and the declining latitudinal thermal gradient should slow the jet stream making trough/ridge patterns more likely to occur.

The Evaporative Demand Drought Index (EDDI) examines how anomalous the atmospheric evaporation demand is for a given location and across a time period of interest according to NOAA. Atmospheric evaporation demand is often referred to as “the thirst of the atmosphere”. The timescale of this index can vary to capture drying dynamics that themselves operate at different timescales.

Dr. Nate Mantua, PDO Expert at the NOAA/NMFS Southwest Fisheries Science Center reports that the March 2021 Pacific decadal oscillation index was -1.17 which represents moderate-to-strong cool phase. During March the -PDO regime present since early last year intensified to the strongest level during this 14-15 month-long cool regime.

The outlook is very similar to previous outlooks projecting a hotter than normal summer season for the Southwest to Central and Northeast U.S. The Great Plains gain a dry climate pattern and widening drought is increasingly likely. The wet zone is across the East and Southeast U.S. Land-falling hurricanes contribute to the wet forecast in September.