I plotted up the tracks of all Atlantic hurricanes with peak winds of at lest 110 knots in time-tranches color-coding the track in 30-knot groups. One thing that intrigued me – it’s probably nothing particular remarkable to specialists – is that many of the big hurricanes had surprisingly similar tracks. Look at the plots below and see if you agree.
The order of the color code here is blue, cyan, green, yellow, orange, red. So red is 150 knot plus and very intense. The first figure below shows tracks from 1975 to 1999. Four of the five very intense hurricanes entered the Caribbean south of the big islands, with Allen and Gilbert having quite similar paths going south of Cuba and towards the Yucatan; David following a similar track but spinning north at Haiti; Mitch being a bit further south, with Andrew being the only very intense hurricane with a more northern track.
Figure 1. Hurricane tracks 1975-1999.
Now here’s a similar image for the 2000-2005 hurricanes. Isabel (2003) is the intense hurricane out in the Atlantic. (Ross McKitrick and I met for the first time while Isabel hit Toronto, meeting for lunch near the Toronto airport.) Ivan (2004), Dennis (2005), Emily (2005) and Wilma (2005) all had southern tracks rather similar to Allen and Gilbert. The most intense portion of Katrina and Rita was in virtually the same spot, seemingly on an arc to the north of the most intense part of IVan the year before. The most intense part of Camille (1969) – a bit more intense than either – was also in almost exactly the same spot.
Figure 2. Same as Figure 1 for 2000-2005 hurricanes.
Looking backwards on the same basis, here is the same figure for 1950-1975 hurricanes. You can see the most intense portion of Camille (1969) in the same location as the most intense portion of Rita and Katrina. Again, very intense winds seem to be concentrated in a few locations.
Figure 3. Same for 1950-1975.
Finally here are comparable figure for the periods 1900-1950 and 1851-1899. Based on the location of the most intense hurricanes in recent years, one would want to know how comprehensive was the coverage in the southern “lane” in which hurricanes like Allen and Gilbert developed. I’m inclined to think that coverage and intensity is likely to be under-estimated in these lanes and, if people are doing hurricane re-assessments, this would be a region to look most closely at.
Figure 4. Same for 1900-1950.
Figure 5. Same for 1851-1899.
In terms of thinking about a statistical model for very intense hurricanes – and I’m just musing here – it seems pretty clear that a hurricane which stays out in the Atlantic doesn’t have much of a chance of developing into a cat 4 or cat 5 hurricane. It reminds me a bit of a game of pinball – if the hurricane gets into the Caribbean or the Gulf of Mexico – its chances of racking up bonus points increase dramatically. Maybe this could account for some of the peculiarity in the distribution.