Oncoming El Nino (Persistent Negative Southern Oscillation) Lead to Wet FEB/MAR Pattern in U.S.

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The atmosphere finally coupled with the equatorial East Pacific warming the past 7 weeks as demonstrated by a persistent negative phase of the southern oscillation index. The evolving El Nino climate helped to inspire heavy precipitation events.

Evolving El Nino Helped Spawn Wet FEB/MAR Pattern

Discussion: Moderate to heavy precipitation became widespread the past 7 weeks including prohibitive amount in California, contributing to historic flooding in the Midwest U.S. and heavy amount in the Mid-South (Fig. 1). The catalyst to this recent stormy pattern is emergence of an El Nino climate as the atmosphere coupled with the warming equatorial East Pacific during late winter. The reaction of the atmosphere is measured by the sudden persistent El Nino-like southern oscillation index (Fig. 2).

Fig. 1: Precipitation rate anomalies across the U.S. since February 1st.

Fig. 2: Daily southern oscillation index since February 1st.