On the recent increase in Atlantic Ocean hurricane activity and influencing factors

Abstract

The recent 2020 Atlantic Hurricane Season was the most active, with 31 storms. September was the most active month of the season, with a simultaneous occurrence of five storms. This study probed into the meteorological and oceanographic conditions prevailing in the Atlantic Main Development Region (MDR) during the high activity months of August, September, and October of 2020. The mean sea surface temperature (SST) for the month of September 2020 was around 0.2��C higher than the 30 years climatological average. Vertical wind shear (WSH) was well below the threshold for cyclogenesis, with a mean of ~ 5�m/s. Such conditions favoured the consecutive storm formations in the basin. Statistical sensitivity analysis was extended for the above three months of 1991�2020, using SST, WSH, and low-level relative vorticity (VOR) as predictors. The analysis showed mean difference between MDR and tropical region SST (SSTDIFF) to be a better influencer of hurricane count (HC) variability, with r 2 values of 0.43 and 0.35 for the months of August and October of 1991�2020 period, respectively. VOR was found to be the dominant influencer of hurricane activity in the month of September, with r 2 value of 0.47. Wavelet local multiple correlation technique showed correlation values to be higher (~ 0.75) for a SSTDIFF�HC pair for the months of August and October. However, VOR�HC pair had the highest correlation (~ 0.8) for the month of September. The WSH condition of the region, although favourable, was not found to be influencing hurricane activity significantly for this period. � 2023, The Author(s), under exclusive licence to Springer Nature B.V.