El Nino to Neutral ENSO & U.S. Summer Climate

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El Nino may weaken by July according to yesterday's Bureau of Meteorology/Australia forecast. Modern-day analogs indicate much of the U.S. is warmer than normal during JUL/AUG/SEP when this ENSO condition occurs. Interestingly, the Corn Belt tends to be dry.

El Nino to neutral ENSO during JUL/AUG/SEP U.S. Climate Implications

Discussion: Yesterday the Bureau of Meteorology/Australia indicated a short-lived El Nino would weaken during JUL/AUG 2019. Since 1950 early ear weak El Nino episodes weakening to neutral phase during summer has occurred on 10 occasions but only 3 times during the past 25 years. Using all analog years the JUL/AUG/SEP U.S. climate is generally marginally warmer than normal in the Central and East U.S. (Fig. 1) while the East-central U.S. is wet (Fig. 2). However, using the more modern-day climate (analogs) the U.S. temperature correlation is much warmer (Fig. 3) although the precipitation regime is similar (Fig. 4). Note the Corn Belt is dry in both (analog) scenarios. The modern-day correlations are likely more realistic. The operational forecast is similarly warm on the West and East Coast but likely wetter/cooler over the Central U.S. wet soil moisture regime.

Fig. 1-2: All analog years of El Nino (early year) to neutral ENSO mid-year and attendant temperature/precipitation anomalies for JUL/AUG/SEP.

Fig. 3-4: Modern-day analog years of El Nino (early year) to neutral ENSO mid-year and attendant temperature/precipitation anomalies for JUL/AUG/SEP.