Ed DunhamAdministrator
(Former Meteorologist & CFHC Forum Moderator (Ed Passed Away on May 14, 2017))
Thu Sep 16 2010 12:29 PM
Re: Frequency and Intensity

Climatology would suggest that this peak period of activity should soon be on the downswing. While periods of high activity have been defined as having a 25-year cycle, a check of the historical data also suggests that the period itself is difficult to identify, i.e., a 25-year cycle is not obvious.

One minor correction - this season at the moment is still average rather than above average, although when the season is over a 13 or 14 storm total seems likely and will eventually place this season in the above average category. The current cycle of high activity started in 1995 so we are in year 16 of the so-called 25 year cycle. Does that mean that we now can expect 16 years of a decline in activity and therefore the 25 year cycle for this period of activity will be defined as a 32 year cycle? Of course that is a question that can't be answered until we get there, but it is worth noting that prior to 1995 the seasonal average was 10 named storms and because of the high activity of the current period the annual average in the Atlantic is now 11 named storms. Unknown as to whether it will remain at 11 or eventually decline to 10 again (or increase to 12).

Regarding Cat IV, this season was unusual in that it produced 4 of these monsters in a record short period of time. Early on in the season we knew that the eastern Atlantic was uncommonly warm this year - however that warmth will be considered by many scientists to be an anomaly unless and until a multi-year pattern of high eastern Atlantic SSTs is observed.

Although we have a climatological hurricane record that dates back to 1853, it contains too many astericks. How many storms were missed prior to the start of the satellite era in 1964? How many storms were not properly classified because there was no recon aircraft prior to the 1940s or no Dvorak Technique prior to 1974? I guess my point is that it seems like we've got a long period of climatological record, but we really don't.

Two of my favorite seasons in the historical record are 1887 and 1969. The numbers for 1887 were 19/11/2 - imagine what the real numbers (and intensities) might have been if satellites were available back then. In 1969 the numbers were 18/12/5 in a season that started a little late - and it did all of that in just under 4 months. Good question though!
ED



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