02/03/2023, 8:38 am EST

February 2023 Atlantic Multidecadal Oscillation Outlook for 2023

Highlight: Spiking warmth of AMO and TNA during 2023 tropical cyclone season. Discussion: The AMO index in 2022 produced a very specific regime: Neutral phase to begin the year suddenly warming (dramatically) during the peak of tropical cyclone season and cooling again by late year. During the long-term cool cycle of ENSO/warm cycle of AMO (since the late 1990’s) a total of 5 similar analog years to 2022 are observed. The following year, the analog suggests a similar pattern: Spiking warm AMO during the tropical cyclone season (Fig. 1) which should add upper ocean heat at that time of the year to support stronger hurricanes. Fig. 1: The 2023 AMO index forecast based on an analog. The TNA index evaluates SSTA across the main development region (MDR) for hurricanes in the North Atlantic basin. Given the El Nino forecast for the 2023 tropical cyclone season, a historical review of TNA patterns during onset El Nino years is relevant to the 2023 forecast. During the current long-term cycle of ENSO and AMO, El Nino onset analog years DURING the tropical cyclone season include 2002, 2004, 2006, 2009, and 2018. The 2006 analog is omitted due to the record warm TNA index observed in 2005 not matching the 2022 regime. The analog projection yields likelihood of decelerating warmth in the outer North Atlantic tropics during the first half of 2023 followed by rewarming to the warm phase during the core of the 2023 tropical cyclone season and prevailing through the end of the year (Fig. 2). The TNA index forecast supports development of robust tropical systems in the deep tropics if the upper shear pattern is supportive. Fig. 2: The 2023 TNA index forecast based on an analog.