Accumulated
Cyclone Energy, ACE measures the total wind energy realized over the
entire life cycle of all storms in a tropical season. ACE is an index that
combines the numbers of systems, how long they existed and how intense they
became. The ACE Index is intended to provide better insight into a
seasons overall intensity than simply counting the number of storms. On average
76% of a seasons total ACE happens after August, 28. Historically, only two named storms
form on average by early August. Based on this, our 2020 season is basically just
getting started.
ACE comes to
be especially important when trying to compare different hurricane seasons in
an effort to show the differences in power used during the seasons. A hurricane
season could have an above-average number of storms, but if they were all weak,
the season could still score lower than a season that had fewer storms overall
but also some major hurricanes.
A paper authored by Carl Drews asserts “The results show that the recent increase in Atlantic hurricane activity is primarily due to an increase in the number of storms per season, with increased hurricane intensity playing a secondary role.”
NOAA uses
the ACE index of a season to classify the season into one of four categories. The
categories break down as: below average,
near average, above average, and extremely active season and are based on the
ACE index, number of tropical storms, hurricanes and major hurricanes over the
30 years between 1981 and 2010.
Atlantic
basin
Category |
ACE Index |
Tropical storms |
Average |
105.6 |
12.1 |
Extremely
active |
Above
152.5 |
Not
defined |
Above-normal |
Above 111 |
13 or more |
Near-normal |
66-111 |
10-13 |
Chart source
Wikipedia
This year most
weather outlets are forecasting the (Atlantic) ACE value to be somewhere
between 150 and 200. Numbers that high would qualify 2020 as a hyperactive
season.
The 1995
Atlantic hurricane season was another hyperactive season with 19 named storms,
11 hurricanes and five major hurricanes: Felix, Luis, Marilyn, Opal and Roxanne.
One thing that really makes 1995 standout
is the fact there were 5 named storms in the Atlantic Basin at the same time,
Humberto, Iris, Jerry, Karen and Luis.
Based on ACE
the 1933 hurricane season was the most intense season in the historic record going back to 1851.
1933 had a total ACE in the North Atlantic of 258.6. The year in 2nd place based on ACE is 2005
with an ACE of 245.3.
When looking
at the number of named storms, 1933 was the 2nd most active on
record. It is estimated to have produced 20 named storms. As I said before, without Satellite observation,
if tropical cyclones stayed out to sea away from populated areas or shipping
lanes, especially if they were short duration and relatively weak, could’ve remained
undetected. Of the 20 storms during the season, 11 attained hurricane
status. 6 of those were major hurricanes. This broke the record for most known named
storms set back in 1887. Out of the 6 major hurricanes, 5 of them made landfall
on the United States. Two of those major hurricanes made landfall one day
apart. The 1933 Hurricane Season was notable in two respects. First, the 21
tropical disturbances recorded that year was a record in the Atlantic (eclipsed
in 2005), and second, the majority of storms moved farther west than is usual.
Seven of these made landfall between Corpus Christi and Tampico, Mexico
So, the total number of storms isn’t really telling the whole story about 2020. While we’re having a record setting pace for named storms; the ACE is lagging quite a bit. So far, the total amount of energy produced in the North Atlantic has been 45.1, the vast majority of which consist of Isaias (9.19) and Laura (12.75), the rest is comprised by the rest of the pack, showing how weak and short lived those tropical cyclones were. We still in the peak of the Atlantic season with still half of the season to go. So, there is still plenty of time for total ACE to climb. The potential of more tropical cyclones impacting the Mid-Atlantic and Northeast are still quite high, based on the climatological average. Just because most of the storms this season have been weak and short lived, doesn’t mean this will be the case for September and October. I don’t believe our region is done with tropical cyclones this season….so keep your guard up…
Source Colorado
State University
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