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07/14/2019, 8:15 pm EDT

U.S. Month 1-3 Ahead Outlook Valid August to October 2019

Warmer than normal; watching increasing tropical cyclone risk Executive summary: After an on again/off again El Nino of 2018-19 could an evolving La Nina be ahead? All the dynamic models show a weak La Nina developing in the AUG/SEP/OCT timeframe which could cause more than previously indicated North Atlantic hurricanes and is likely to bias late summer and autumn warmer than normal for much of the nation. Fig. 1: Global models indicate an evolving La Nina for early autumn. August 2019: Most striking in the August forecast is the wetter adjustment for the Gulf region extending northward toward the Corn Belt. The outlook suggests additional tropical events in the Gulf are likely with attendant soaking rains as they move inland. A wet/cool pattern remains in the forecast for Montana into the Dakotas but somewhat smaller in coverage versus previous forecasts. Can a western U.S. ridge organize and bring persistent hot weather? For the most part, that forecast has failed this summer season (so far). However, a hot ending to meteorological summer is likely in the West. Hottest anomalies are projected across the Mid-Atlantic States upwind from the heat release of tropical events in the Gulf region. Fig. 2-3: The Climate Impact Company month ahead forecast for August 2019.  September 2019: The outlook is adjusted cooler due to the influence of Pacific troughs rolling into central continent. Otherwise September is warmer than normal across most of the U.S. Interestingly, the wet pattern over the Gulf region in August reverses dry in September. There is tropical cyclone risk to the Mid-Atlantic coast in September. The Northwest is dry and quite warm in September. Fig. 4-5: The Climate Impact Company month ahead forecast for September 2019.  October 2019: Middle autumn is warmer than normal across the entire U.S. especially if a weak La Nina develops. Wet weather suppresses Northwest U.S. drought and late season tropical/subtropical events are possible on the East Coast. Fig. 6-7: The Climate Impact Company month ahead forecast for October 2019.