Tuesday, July 21, 2020

Global (all basins) 2020 Accumulated Cyclone Energy [ACE]: It's Quiet Out There, Too Quiet

Although an imperfect measure, ACE is a very handy shorthand. From Wikipedia:
Accumulated cyclone energy (ACE) is a measure used by various agencies including the National Oceanic and Atmospheric Administration (NOAA) and the India Meteorological Department to express the activity of individual tropical cyclones and entire tropical cyclone seasons. It uses an approximation of the wind energy used by a tropical system over its lifetime and is calculated every six hours. The ACE of a season is the sum of the ACEs for each storm and takes into account the number, strength, and duration of all the tropical storms in the season. The highest ACE calculated for a single storm is 82, for Hurricane/Typhoon Ioke in 2006....
And from the keeper of the ACE, Ryan Maue, Climatlas, July 21:

2020 Accumulated Cyclone Energy [ACE]

  Basin   Current YTD   Normal YTD % of Normal YTD Yearly Climo* 2018**
  Northern Hemisphere   41.5375   105 39% 568 821
  Western N Pacific   7.4425   61 12% 302 356
  Eastern + Cent N Pac   6.835   30 22% 138 320
  North Atlantic   8.04   6 134% 104 131
  North Indian   19.22   7 274% 18 37
  Southern Hemisphere   108.925   N/A N/A N/A 198
  Global   150.4625   277 54% 771 1011

*Climatology from historical 1981-2010 Tropical cyclone best track datasets
**Preliminary values from real-time ATCF advisories and will become final when best-tracks are available from JTWC and NHC after post-season analysis Small differences have been found in previous years between real-time and best-track ACE.