Accumulated Cyclone Energy Index Vs. Atlantic Multidecadal Oscillation

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Highlight: Warm North Atlantic Cycle Continues, Promotes Stronger TC Seasons

Fig. 1: Annual accumulated cyclone energy (ACE) index 1950-2021 versus the long-term phase of the Atlantic multi-decadal oscillation (AMO) and Climate Impact Company 2022 ACE forecast (149).

Discussion: According to NOAA/NHC, the accumulated cyclone energy (ACE) index is a metric used to express the energy used by a tropical cyclone during its lifetime measured on a 6-hourly basis. ACE index is added for each storm to determine the “activeness” of a given season. The Atlantic multi-decadal oscillation (AMO) is a decadal cycle of alternating warm/cool North Atlantic basin average SST. Currently, we’re in the long-term warm cycle which began in the middle 1990’s. The last warm cycle occurred from 1925-1964. Tropical cyclone activity increases (unless El Nino is present) when the North Atlantic basin is warmer than normal (+AMO). Since the middle 1990’s, the “activeness” of the North Atlantic basin seasonal tropical cyclone activity has generally been above to much above normal due to the long-term warm cycle of AMO and the lack of El Nino presence (only 24% of the months from 1995-2022). Climate Impact Company is forecast an ACE index of 149 for the 2022 season.