Do Gulf of Mexico Hurricanes Tend to be Larger Than Those Elsewhere in the Atlantic Basin?

Recent U.S. Gulf Coast hurricane landfalls of large but relatively weak hurricanes (Category 1 and 2) have caught the general public off-guard because these hurricanes produced damage that was judged extreme given their maximum sustained winds. Hurricanes like Isaac (2012) and Ike (2008) produced very large storm surges that inundated large swaths of the coastline, something not typically characteristic of lower-end hurricanes. Katrina (2005), though it was a Category 3 hurricane at landfall, produced a much larger storm surge along the Mississippi coast than did Category 5 Camille (1969), even though Katrina had much lower winds than Camille.

Hurricanes Ike, Isaac and Katrina are three examples of tropical cyclones that had relatively low central pressures and lower maximum sustained winds when compared to the standard pressure-wind relationship. Tropical cyclones that have lower central pressure but also rather low maximum sustained winds are usually larger in size. This is because the pressure gradient (and wind field) is spread out over a larger area. These types of tropical cyclones have produced larger swaths of moderate damage (larger number of power outages, larger area of minor to moderate structural damage, higher storm surge over a larger length of coastline).

In this study, the pressure-wind relationships of northern Gulf of Mexico hurricanes (north of 25N) from 1988 to present will be examined and compared to pressure-wind relationships elsewhere in the Atlantic Basin to determine if there is a greater frequency of larger hurricanes with lower pressure in the Gulf of Mexico when compared to the rest of the Atlantic Basin. Hurricane size will be evaluated using ImpactWeather's Hurricane Severity Index (HSI), which provides a size component. The size component of HSI is obtained for the tropical cyclones studied here (1988-present). It is hypothesized that tropical cyclones in the Gulf of Mexico (25-30N, 81-98W) tend to be larger and have a lower pressure for the same winds (on average) as compared with tropical cyclones in the same latitude band east of the Gulf of Mexico.