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A Hyperactive End to the Atlantic Hurricane Season: October–November 2020

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  • 1 Department of Atmospheric Science, Colorado State University, Fort Collins CO 80523
  • | 2 Department of Geosciences, Mississippi State University, Mississippi State MS 39762
  • | 3 Department of Atmospheric Science, Colorado State University, Fort Collins CO 80523
  • | 4 National Hurricane Center, National Oceanic and Atmospheric Administration, Miami FL 33165
  • | 5 Aon, Chicago IL 60601
  • | 6 Ouranos, Montreal Canada H3A 1B9, Barcelona Supercomputing Center, Barcelona Spain 08034
  • | 7 School of Geosciences, University of South Florida, Tampa FL 33620
  • | 8 UCAR/Cooperative Programs for the Advancement of Earth System Science, San Diego, CA 92127
  • | 9 North Carolina Institute for Climate Studies, Cooperative Institute for Satellite Earth System Studies (CISESS), North Carolina State University, Asheville NC 28801
  • | 10 WeatherTiger, LLC, Tallahassee FL 32302
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Abstract

The active 2020 Atlantic hurricane season produced 30 named storms, 14 hurricanes, and 7 major hurricanes (Category 3+ on the Saffir-Simpson Hurricane Wind Scale). Though the season was active overall, the final two months (October–November) raised 2020 into the upper echelon of Atlantic hurricane activity for integrated metrics such as Accumulated Cyclone Energy (ACE). This study focuses on October–November 2020, when 7 named storms, 6 hurricanes, and 5 major hurricanes formed and produced ACE of 74 * 104 kt2. Since 1950, October–November 2020 ranks tied for 3rd for named storms, 1st for hurricanes and major hurricanes, and 2nd for ACE. Six named storms also underwent rapid intensification (≥30 kt intensification in ≤24 hr) in October–November 2020—the most on record.

This manuscript includes a climatological analysis of October–November tropical cyclones (TCs) and their primary formation regions. In 2020, anomalously low wind shear in the western Caribbean and Gulf of Mexico, likely driven by a moderate intensity La Niña event and anomalously high sea surface temperatures (SSTs) in the Caribbean provided dynamic and thermodynamic conditions that were much more conducive than normal for late-season TC formation and rapid intensification. This study also highlights October–November 2020 landfalls, including Hurricanes Delta and Zeta in Louisiana and in Mexico and Hurricanes Eta and Iota in Nicaragua. The active late season in the Caribbean would have been anticipated by a statistical model using the July–September-averaged ENSO Longitude Index and Atlantic warm pool SSTs as predictors.

Klotzbach and Wood contributed equally to this work.

Corresponding author address: Philip J. Klotzbach, Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523 email: philk@atmos.colostate.edu

Abstract

The active 2020 Atlantic hurricane season produced 30 named storms, 14 hurricanes, and 7 major hurricanes (Category 3+ on the Saffir-Simpson Hurricane Wind Scale). Though the season was active overall, the final two months (October–November) raised 2020 into the upper echelon of Atlantic hurricane activity for integrated metrics such as Accumulated Cyclone Energy (ACE). This study focuses on October–November 2020, when 7 named storms, 6 hurricanes, and 5 major hurricanes formed and produced ACE of 74 * 104 kt2. Since 1950, October–November 2020 ranks tied for 3rd for named storms, 1st for hurricanes and major hurricanes, and 2nd for ACE. Six named storms also underwent rapid intensification (≥30 kt intensification in ≤24 hr) in October–November 2020—the most on record.

This manuscript includes a climatological analysis of October–November tropical cyclones (TCs) and their primary formation regions. In 2020, anomalously low wind shear in the western Caribbean and Gulf of Mexico, likely driven by a moderate intensity La Niña event and anomalously high sea surface temperatures (SSTs) in the Caribbean provided dynamic and thermodynamic conditions that were much more conducive than normal for late-season TC formation and rapid intensification. This study also highlights October–November 2020 landfalls, including Hurricanes Delta and Zeta in Louisiana and in Mexico and Hurricanes Eta and Iota in Nicaragua. The active late season in the Caribbean would have been anticipated by a statistical model using the July–September-averaged ENSO Longitude Index and Atlantic warm pool SSTs as predictors.

Klotzbach and Wood contributed equally to this work.

Corresponding author address: Philip J. Klotzbach, Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523 email: philk@atmos.colostate.edu
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