Your Note is very interesting and I just wanted to add some personal comments if I might.

I have done a great deal of the research on north Florida and coastal Georgia historical landfalls, some of which was utilized by the North Atlantic HURDAT Reanalysis Project. While the landfall trend you point out is pronounced for the US Atlantic Seaboard in general it is even more conspicuous for some portions of the coast. For example, let’s look at the South Atlantic Bight, and in particular the apex of the Bight in coastal Georgia. Along this stretch of coast the second half of the 19th Century was active with five landfalls (1854, 1881, 1893, & [2] 1898) and three of those were major events (1854, 1893, 1898). If we look at the 19th century as a whole, one can even go further with several likely major hurricane landfalls during the first half of the 19th century (1804 [cat 4?], 1813 [cat 3?] & 1824 [cat 3?]), and I say likely as they are currently outside the HURDAT database. Chris Landsea and I have written an Electronic Tech Memo on Georgia Coastal Landfalls which can be reviewed at…

http://www.aoml.noaa.gov/hrd/Landsea/history/index.html

Now let’s contrast that “active period” with a second 100 year period from 1900 through 1999 which happens to be the period of the Jarrell et al. analysis and a large portion of the HURDAT Database. During this similar time frame we have only four direct or indirect landfalls (1911, 1940, 1947, & David “1979”) with no major landfalls! So for the 100 year period from 1800-1899 this small 111 mile stretch of coastline likely experienced six (6) direct major landfalls with none for a similar 100 year from 1900-1999.

If we were to try to make a determination of North Atlantic Hurricane activity based solely upon the Georgia coastal activity one would tend to believe that there were a significant number of 19th Century NA hurricanes but that trend had tailed off significantly during the 20th Century to the point were hurricanes do not poise a major threat. Of course no one would jump to that type of a conclusion based upon such a limited dataset (unless they live along the Georgia coast that is, as because I fight that battle daily). I’ve looked hard for just why the landfall incidence has changed so dramatically along the Georgia coast and have come up with some good ideas but nothing I can hang my hat on. Maybe the end of the Little Ice Age has altered landfall patterns in the Bight and local shelf water SST’s may also play a role, but who knows for sure. So while the trends you point out are evident for the CONUS its really interesting if you look at smaller portions of the coast.

Thanks much. You are absolutely right that this issue has been noticed (e.g., see the Solow articles cited above). And your analysis looks right on to me. What is interesting is that a number of very recent studies continue to use storm count data in uncritical fashion.

Happy new year!

Actually, I’m sure quite a few people noticed it. I was writing about it for my blog back in August and September of 2005.

http://iconicmidwest.blogspot.com/2005/08/global-warming-hurricane-myths.html

http://iconicmidwest.blogspot.com/2005/09/blaming-tiny-dwarf.html

In response to a criticism of my work I made the following observation:
http://iconicmidwest.blogspot.com/2005/09/blogging-with-data-youve-got.html

“In an attempt to refute my work the following was stated:

‘Misleading Because he limits his analysis to Hurricans that hit the United States,” and not the sum total of ALL Atlantic hurricanes, many of which never strike the US.’

I didn’t address this issue in my original post because I believed the answer to that question was self-evident, but maybe for many it isn’t. If one wants to compare data on hurricanes into the 19th century it makes sense to limit the discussion to only landfalling hurricanes. Why? For many reasons:

A) Without benefit of satellite imagery many non-land falling hurricanes in the 19th century would have been unknown. Failing to take this into account would seriously skew results in favor of saying there were many more post 1950 hurricanes. A similar thing happens when you hear of a “record number of tornadoes” striking the U.S. Well, with the tremendous increase in the number dopplar radar sites finding storms that might have never been seen by human eyes (e.g. remote rural areas, or in the dead of night), that should come as no surprise. It certainly doesn’t indicate that the number of tornadoes are increasing.

B) Logically, there is no reason to think that the incidence of U.S. landfall should change statistically speaking from the 19th century to today. In other words, if there are more hurricanes across the Atlantic basin as a whole, there should be a corresponding increase in the number of U.S. land-falling storms. Why one would wish to believe otherwise escapes me.”

It is nice to see work that backs up the gist of what I was claiming. (Although I’m sure my humble efforts wouldn’t pass muster in many other respects.)

Solow, A. R., Moore, L. J., 2002: Testing for Trend in North Atlantic Hurricane Activity, 1900-98. Journal of Climate. 15, 3111-3114.

The detection of a trend in hurricane activity in the North Atlantic basin has been restricted by the incompleteness of the record prior to 1946. In an earlier paper, the complete record of U.S. landfalling hurricanes was used to extend the period of analysis back to 1930. In this paper, a further extension is made back to 1900. In doing so, the assumption in the earlier paper of an exponential linear trend is relaxed and the trend is estimated nonparametrically. The results show no significant trend in basinwide hurricane activity over the period 1900–98.

Solow A. R., and L. Moore, 2000: Testing for a trend in a partially incomplete hurricane record. J. Climate, 13, 3696–3699.

The record of annual counts of basinwide North Atlantic hurricanes is incomplete prior to 1946. This has restricted efforts to identify a long-term trend in hurricane activity to the postwar period. In contrast, the complete record of U.S. landfalling hurricanes extends back to 1930 or earlier. Under the assumption that the proportion of basinwide hurricanes that make landfall is constant over time, it is possible to use the record of landfalling hurricanes to extend a test for trend in basinwide hurricane activity beyond the postwar period. This note describes and illustrates a method for doing this. The results suggest that there has been a significant reduction in basinwide hurricane activity over the period 1930–98.

I am not sure how to test this concept, but one might begin by looking at the distribution of lengths of hurricanes (either time or distance will do), and noting if the average length decreases during busy hurricane years.

It is a breakout of wind speed readings from the unisys hurricane database for the Atlantic basin. The file I used is tracks.atl that ends with 2005.
It appears that as time goes on, more low readings are being included.

There appears to have been a shift in observational techniques around 1950 and again around 1980.

I don’t know how this affects the statistical reliability, but thought it might have a bearing on the lower percentage of US landfalling storms. Might it be appropriate to only use obsevations above a certain wind speed threshhold? Say 30-35kts. Those are certainly the ones most likely to be recorded over long
periods of time.

10kt, 15kt, 20kt, 25kt, 30kt, 35kt, 40kt, 45kt, 50kt, 55kt, more, total
1851-60, 0, 0, 0, 0, 0, 0, 69, 0, 147, 0, 685, 901
1861-70, 0, 0, 0, 0, 0, 0, 54, 0, 140, 0, 827, 1021
1871-80, 0, 0, 0, 0, 52, 0, 367, 0, 396, 0, 1252, 2067
1881-90, 0, 0, 0, 4, 56, 167, 291, 143, 349, 67, 1268, 2345
1891-00, 0, 0, 2, 47, 94, 326, 332, 223, 405, 116, 1463, 3008
1901-10, 0, 0, 4, 74, 288, 498, 269, 181, 190, 86, 873, 2463
1911-20, 0, 3, 29, 44, 114, 225, 153, 142, 98, 80, 667, 1555
1921-30, 0, 2, 13, 33, 55, 370, 191, 116, 97, 56, 861, 1794
1931-40, 0, 18, 51, 72, 78, 732, 418, 173, 149, 113, 971, 2775
1941-50, 0, 18, 26, 105, 80, 360, 295, 230, 188, 109, 1094, 2505
1951-60, 0, 27, 10, 301, 178, 327, 180, 229, 191, 103, 1241, 2787
1961-70, 0, 11, 27, 475, 502, 193, 171, 178, 170, 137, 1419, 3283
1971-80, 0, 20, 90, 342, 478, 210, 240, 218, 160, 136, 886, 2780
1981-90 21, 47, 81, 302, 418, 281, 247, 244, 188, 178, 816, 2823
1991-00, 6, 21, 164, 251, 475, 329, 308, 315, 264, 171, 1334, 3638
2001-05, 34, 29, 139, 273, 378, 293, 212, 250, 221, 166, 816, 2811
total, 61, 196, 636, 2323, 3246, 4311, 3797, 2642, 3353, 1518, 16473, 38556

Here’s mean wind speed for all readings and also for speeds of 30kt or more.
All, 30kt+
1851-60, 71.6, 71.6
1861-70, 71.7, 71.7
1871-80, 62.7, 62.7
1881-90, 61.2, 61.3
1891-00, 61.4, 62
1901-10, 52.1, 53
1911-20, 57.8, 59.6
1921-30, 61.2, 62.2
1931-40, 53.1, 54.8
1941-50, 58.6, 60.9
1951-60, 58.5, 63.2
1961-70, 55.1, 60.8
1971-80, 49.2, 54.1
1981-90, 48.4, 53.3
1991-00, 52.7, 56.9
2001-05, 50.6, 56.5
total, 56.3, 59.3
Hmmm. Doesn’t seem to format well.
The data could be saved as a .csv file and put in a spreadsheet for better viewing.

A large percentage of those losses could have happened in what they thought of as the “Bermuda Triangle”.