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07/22/2019, 2:10 pm EDT

Weekly ENSO Diagnostics Report

Looking Like an El Nino Modoki Discussion: The ever-changing ENSO regime has yet again has a new look. Recent weeks of cooling in the eastern equatorial Pacific have defeated the 2018-19 weak (conventional) El Nino. However, leftover warmth at the surface (Fig. 1) and subsurface (Fig. 2) near the Dateline indicate an El Nino Modoki may be developing (Fig. 3). The Nino SSTA regions are each below the El Nino threshold except Nino4 (central Pacific) which remains robustly in El Nino territory (Fig. 4). When was the last late (northern hemisphere) summer El Nino Modoki? Since the ENSO/PDO and AMO cycle change in the mid-to-late 1990’s an El Nino Modoki has been present during August in 2002 and 2004. In both cases the El Nino Modoki strengthened the remainder of the year. Interestingly, the 2002/2004 analog upper air pattern for August features a Central U.S. trough and ridge pattern on each coast similar to analogs produced for August when atmospheric angular momentum (AAM) becomes negative (mentioned in yesterday’s notes). The largescale climate pattern for August appears to be heading for a wet solution reaching from the Gulf States to the Corn Belt. Summary: Conventional El Nino has ended. However, the warmth associated with the weak El Nino of 2018-19 remains in-place both at the surface and subsurface near the Dateline in the equatorial Pacific. The trend of warming near the Dateline while the eastern equatorial Pacific cools remains in-place. A weak El Nino Modoki may be forming. Fig. 1: Global SSTA observations for July 20, 2019 reveal an El Nino Modoki look in the equatorial Pacific Ocean. Fig. 2: The El Nino Modoki is supported by warmth in the subsurface near the Dateline. Fig. 3: An El Nino Modoki has generated in recent weeks. Fig. 4: The Nino SSTA regions have trended cooler to beneath El Nino thresholds except the Nino4 region which is near the Dateline.
07/15/2019, 3:08 pm EDT

Weekly ENSO Diagnostics: Neutral ENSO

Neutral ENSO Discussion: ENSO is essentially neutral with only the Nino4 (central Pacific) warmer than normal (Fig. 1). The still warm central pacific tropics compared with the cooling eastern equatorial Pacific is indicative of a potential El Nino Modoki. Subsurface temperatures are also somewhat cooler especially in the far eastern equatorial East Pacific (Fig. 2). Fig. 1: The 12-week Nino SSTA regions indicate a persistent lingering El Nino warming is confined to near the Dateline. Fig. 2: Upper ocean heat to sustain El Nino continues to decline.