Undercounting Hurricanes Revisited

Some four years ago I posted a study I had made on the likely undercounting of tropical storms in the historical best track data. Using very rudimentary tools and good ol' fashioned logic I reached the following conclusion:

It seems very probable the Mid-Atlantic storm counts are undercounted in some fashion. It is a trickier question to determine the degree of undercounting. However, if we take the rates of Mid-Atlantic storms found during the satellite era (see Figure 2 above) and apply them to the pre-satellite era the results are startling. Broken down by decade, the percentage of Mid-Atlantic storms to all storms in the satellite era looks like:

1967-1976: 17.20%
1977-1986: 14.44%
1987-1996: 24.53%
1997-2006: 21.23%

and for the entire period:

1967-2006: 19.77%

If we look at the minimum (14.44%) and maximum (24.53%) values as defining a range for the pre-satellite number (which today sits at 40 Mid-Atlantic storms out of 495 total storms, or 8.08%,) we are left with a range of an additional 1.28 to 2.46 storms per year. That would mean a difference for the sixty year period [ed. 1907-1967] of plus 77 to 148 storms.

Recently a new study has come out looking at the same issues, though using a much more sophisticated method of estimating the undercounts. Here is their chart for the adjusted data account for the probable missing storms:



As can be seen these results match up with my own to a remarkable degree. If mine were a little larger it must be remembered the range I gave was for all tropical storms while this chart is only looking at hurricanes. In fact, their adjustment is more than the one I suggested.

Still this kind of confirmation is nice to see.