Risk of Strong Hurricane Winds to Florida Cities

Every year hurricanes threaten the United States with the potential for catastrophic losses of life and property. The risk of a catastrophe varies by location. The state of Florida is particularly vulnerable due to its position surrounded by warm seas. According to Blake et al. (2007), 40% of all U.S. hurricanes and major hurricanes hit Florida; and 83%of category 4 or higher hurricane strikes have hit either Florida or Texas. Due to increasing populations and economic development in the areas prone to devastation, average economic losses are increasing over time (Malmstadt et al. 2009). For society to better cope with and mitigate these disasters, amore precise estimate of the risk of high winds on the local level is needed. Indeed, companies can use this kind of information to sell catastrophe bonds that break down potential hurricane wind losses by municipality.

Here, we consider wind risk from a hurricane as the probability of a region experiencing winds of hurricane force or greater within a specified period. Within this context, risk is an attribute of a region that is determined by the size and location of the region and not by the potential for loss of life or property. Risk is an unobserved and changing quantity that is estimated using a statistical procedure. The procedure provides an estimate of the exceedence wind speed (return level) as a function of the return period (inverse of the annual probability). The primary goal here is to quantify the level of risk of hurricane winds of varying magnitudes blowing over a particular region over a given time period. This method can provide useful return-level estimates for homeowners on a 20–30-yr mortgage as well as provide information at similar time scales as offered for the 100-yr flood plain in the hydrology literature (Bin et al. 2008).

In particular, the present work estimates return levels of hurricane winds affecting Florida cities and examines the case for secular trends in the intensity and frequency of hurricanes in the vicinity of the state. This is an application of the Elsner et al. (2008a) model, where information from past cyclones affecting the city and its vicinity are combined through the parameters of an extreme-value distribution to estimate return levels. This paper goes beyond the initial work by automating the procedure and applying it to cities in Florida. This procedure, called the hurricane risk calculator (HRC), borrows information from a larger region to estimate the distribution parameters for a smaller region. The methodology implicitly assumes a stationary climate with regard to the occurrence and intensity of the wind events. Here, we shed some light on this assumption by examining the case for trends in hurricane activity in and around the state of Florida using the method of quantile regression as introduced in the study of hurricane climatology in Elsner et al. (2008b).

The paper begins with a description of the data used for this study in section 2. Section 3 discusses the statistical procedure for estimating local wind risk. Section 4 gives the results of the return-period calculations for selected Florida cities. Section 5 presents the methods and results of the trend analysis of hurricanes in the vicinity of Florida. Section 6 summarizes the results and emphasizes the important conclusions of this study. The work is important in providing reliable estimates of hurricane wind return periods for the population centers of Florida and for demonstrating a statistically significant trend in hurricane intensification rates in the vicinity of the state.

Malmstadt, Jill C., James B. Elsner, Thomas H. Jagger, 2010: Risk of Strong Hurricane Winds to Florida Cities. J. Appl. Meteor. Climatol., 49, 2121–2132. doi: http://dx.doi.org/10.1175/2010JAMC2420.1