Historical records and multidecadal signal

[Calasanjy]

I was curious about the expected length of the current multi-decadal signal for the Atlantic and Eastern Pacific basins. As the current one has continued since 1995, and Bill Gray and other tropical weather experts have expected it to persist for at least another ten years, are there any trends exploring the records back through the early 20th century as to how long each cycle typically persists?

In addition, are there any such patterns in other basins? I've noticed that the Western Pacific, with a few exceptions, has seemed to have been declining in activity since the mid-'90s. While the Southern Hemisphere appears more flexible year-to-year as opposed to featuring long-term (i.e. multidecadal) trends, the records have indicated an increase in the number of particularly intense TCs within the past 20 or so years. However, I have encountered debates over whether TCs in prior decades were underestimated. To those who track historical activity in these basins, do you have any thoughts? Thanks for the info.

[Derek Ortt]

some work by Jeffery Donnelly from Woods Hole University showed that the multi-decadal signature is only a function of the 20th century. In the centuries prior, there are no signs of this

[Calasanjy]

Very curious. BTW, do you believe the records for prior centuries to be accurate?

I have difficulty fathoming how something like that would suddenly appear in the twentieth century, aside from potentially increased CO2 levels which I would think to be too minimal thus far to cause such a dramatic cycle.

[Derek Ortt]

the long-term records are derived using sediment cores. There is a distinct signal for each landfall.

The way that the activity is determiend is based upon the nuber of surge events at a given location

[Ptarmigan]

Very curious. BTW, do you believe the records for prior centuries to be accurate?

I have difficulty fathoming how something like that would suddenly appear in the twentieth century, aside from potentially increased CO2 levels which I would think to be too minimal thus far to cause such a dramatic cycle.

Satellites were not around. Most of them were recorded by ships. Also, they tend to avoid storms for safety reasons. Many of these storms were underestimated. It would not surprise me if there were more storms that went undetected in the Atlantic.

I think 2005 like seasons are not as rare as we like to think. Some seasons I think were very active and if not more so than 2005 in the 19th century. Likely candidate years before the 20th century are 1886, 1887, 1893, and 1899. As for the 20th century, I think 1933 had more than 21 storms, likely around 30 storms formed.

[KWT]

I think its likely 1933 was every bit as active as 2005 in terms of storm numbers, 1887 also may have been up there considering the amount of storms that likely went undected in the Atlantic and the fact it had 19 storms anyway.