The six-month 2019 North American hurricane season is officially in the books, and it was an active one in terms of named storm counts, with the majority of activity coming in the typical mid-August and mid-October periods. The season ended with 18 named storms, six of which became hurricanes, and three of those achieving major hurricane status (Category 3+ on the Saffir-Simpson scale). Having 18 named storms in a season is well above the 12.1 average (1981 – 2010), but the number of hurricanes and major hurricanes is right around what would be expected in an average year. In terms of ACE (Accumulated Cyclone Energy), the season ended up at 123% of the average, with two storms, Dorian and Lorenzo, contributing an impressive 61% to the tally.
Preliminary Atlantic Tropical System Track Map Source: NHC.
*After spiking this summer, the Atlantic Multidecadal Oscillation (AMO) index dipped back to near average in November, according to the Klotzbach and Gray AMO index, as far north Atlantic sea surface temperatures are currently near their long-term average values. This could have explained the higher activity this season and could lead to lower counts next season if sea surface temperatures continue to drop.
After spiking this summer, the Atlantic Multi-decadal Oscillation (AMO) index dipped back to near average in November.
Andrew Siffert is vice president and senior meteorologist within BMS Re U.S. catastrophe analytics team. He works closely with clients to help them manage their weather-related risks through catastrophe response, catastrophe modeling, product development and scientific research and education.