August Updated Forecast for the 2021 Atlantic Hurricane Season

19 08 2021

Dale C. S. Destin |

The forecast for the 2021 hurricane Season continues to call for an active season with the possibility of it being super-hyperactive. The confidence of an above normal season has remained virtually unchanged at 78%. It is also possible that the season could be super hyperactive or well above normal, with numbers reaching the top 10 percentile 1991-2020 base period or current climate period.

The prediction is now for 22 named storms (subtropical storms, tropical storms and hurricanes), with a 70 percent confidence or high confidence of the number ranging between 17 to 28. It is also likely–69 percent chance, that the number of named storms will exceed 19 and be in the top 10 percentile of the current climate period.

My forecast also calls for an accumulated cyclone energy (ACE) index of 188 with a high confidence of the range being 115 to 284. Also predicted are 11 hurricanes with a 70 percent confidence of  the total being 7 to 15, and 5 major hurricanes with high confidence of 3 to 7.

The season could also be well above normal or super hyperactive. There is also a 45% chance of the ACE exceeding 223, the top 10 percentile of the current climate period. Further, there is a massive 69% chance of more than 19 named storms or the number of named storms reaching the top 10 percentile. There is also a 41% chance of more than 11 hurricanes and 45% chance of more than 6 major hurricanes.

If this forecast pans out, this season would be the most active since 2017, in terms of ACE, and the 10th most active on record dating back to 1851. It would also be ranked third for the highest number of named storms, tied for 5th for the most hurricanes and 11th for the most major hurricanes.

If the season turns out to be hyperactive, as is possible, it will rank even higher. Only seven seasons have had a higher ACE than 223; three seasons with more than 19 named storms; four with more than 11 hurricanes and two with more than 6 major hurricanes.

The season initially got off to a “flyer” but became sedate in July. Since the start of August, activity has picked back up, going at a rate of of about one-and-half times the normal season. To date, there have been eight named storms with three becoming hurricanes. A typical season, based on the standard climate period 1991-2020, has 14 named storms, 7 hurricanes and 3 major hurricanes.

The main reason for the above normal forecast is the likely weak La Niña conditions or cold El Niño Southern Oscillation (ENSO) during August to October–the peak of the hurricane season.

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