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08/08/2018, 1:18 pm EDT

Monthly ENSO Outlook

The Case for El Nino Modoki Executive Summary: The Climate Impact Company ENSO forecast through DEC/JAN/FEB indicates a 3-in-4 chance of El Nino Modoki or 1-in-4 chance that El Nino does not develop. Trends do not support a conventional El Nino for later this year.  El Nino onset is likely delayed until autumn. An intense El Nino is not expected.  If an El Nino Modoki develops a considerably different look to winter (versus a conventional El Nino) is likely featuring cold risk in the U.S., Europe and Russia. Discussion:  The subsurface equatorial temperature anomaly regime in the Pacific Ocean during July (Fig. 1) from June (Fig. 2) identify several important trends regarding expectations of ENSO phase for later 2018. First, warming in the far eastern equatorial Pacific which is where El Nino usually develops weakened in July. Second, the still robust warm signature shifted westward (in the east-central equatorial Pacific) and weakened slightly. And third, the subsurface West Pacific remains very warm which weakens El Nino risk. Implications of these mid-2018 trends are slightly lower El Nino risk and the possibility that El Nino may not develop as indicated by the Bureau of Meteorology/Australia forecast (Fig. 3). In 2012 El Nino came on mid-year and suddenly dissipated during autumn. The 2012 analog has a 1-in-4 chance of verifying in 2018. The other more likely possibility is that the subsurface warming convenes most strongly toward the Dateline and an El Nino Modoki forms similar to 1994, 2002 and 2009 (Fig. 4). Arrival of El Nino Modoki given the well-established neutral ENSO in August is a delay until later this year but in-place for northern hemisphere winter. Using the 1994-95, 2002-03 and 2009-10 El Nino Modoki analog years a historical perspective on potential winter ahead scenarios in the northern hemisphere reveal cold risk in the U.S., Europe and Russia (Fig. 5). Fig. 1: The subsurface Pacific Ocean anomalous warmth has increased in the West Pacific and weakened while shifting west in the East Pacific since June. Fig. 2: The subsurface equatorial East Pacific reached peak warming in June. Fig. 3: The Bureau of Meteorology/Australia forecast neutral ENSO ahead. Fig. 4: The Climate Impact Company analog forecast of ENSO phase reveals a 3-in-4 chance of El Nino ahead for later 2018 and into 2019. Fig. 5: The last 3 El Nino Modoki episodes averaged together produce a northern hemisphere winter temperature anomaly pattern favoring cold in the U.S. and especially Europe and Russia.