Carvill Hurricane Index

The Carvill Hurricane Index (CHI) is an index which describes the potential for damage from an Atlantic hurricane. The CHI is used as the basis for trading hurricane futures and options on the Chicago Mercantile Exchange (CME).

Index Calculation

The CHI takes as input two variables: the maximum sustained wind speed of a hurricane in miles per hour and the radius to hurricane force winds of a hurricane in miles (i.e. how far from the center of the hurricane winds of 74mph or greater are experienced). If the maximum sustained wind speed is denoted by "V" and the radius to hurricane force winds is denoted by "R" then the CHI is calculated as follows:

$CHI\; =\; left\; (\; frac\{V\}\{V\_0\}\; ight\; )^3\; +\; frac\{3\}\{2\}left\; (\; frac\{R\}\{R\_0\}\; ight\; )\; left\; (\; frac\{V\}\{V\_0\}\; ight\; )^2$

where the subscript "0" devotes reference values. For use on the CME, the reference values of 74 mph and 60 miles are used for the maximum sustained wind speed and radius of hurricane force winds respectively.

Index History and Data

The development of the CHI was based on work published by Lakshmi Kantha at the Department of Aerospace Studies at the University of Colorado in Boulder, Colorado. Kantha's paperL. Kantha, "Time to Replace the Saffir-Simpson Hurricane Scale?", "Eos", Vol. 87, No. 1, 3 January 2006] in Eos developed a number of indices based on various characteristics of hurricanes. The ReAdvisory team at the reinsurance broker RK Carvill [http://www.carvill.com RK Carvill website] ] used the basics of the Kantha paper to develop an index which became the CHI.

The data for the CHI comes from the Public Advisories issued for named storms by the National Hurricane Center. Specifically, to determine the maximum sustained wind speed, the following verbiage is looked for:

MAXIMUM SUSTAINED WINDS ARE NEAR "XX" MPH

To determine the radius to hurricane force winds, the following phrase is looked for:

HURRICANE FORCE WINDS EXTEND OUTWARD UP TO "XX" MILES

For example, Advisory 23A [ [http://www.nhc.noaa.gov/archive/2005/pub/al122005.public_a.023.shtml? Katrina Advisory 23A] ] for Hurricane Katrina at 1pm Central Daylight Time on Sunday, August 28th, 2005, gave the maximum sustained wind speed of 175 mph and the radius of hurricane force winds of 105 miles resulting in a CHI value of 27.9.

Data

Public Advisories from the National Hurricane Center are archived back to 1998. The table below lists the CHI values for all the landfalling hurricanes since 1998 based on the NHC Public Advisories.

Prior to 1998, the data becomes sparse. However, using data from the HURSAT [ [http://www.ncdc.noaa.gov/oa/rsad/hursat/ Hurricane Satellite] ] database at NOAA it is possible to construct a set of CHI values for storms back to 1983.

Modeled data is available from a number of sources:
* Seasonal data, suitable for use in the insurance and reinsurance community, is provided by [http://www.air-worldwide.com Applied Insurance Research]
* [http://www.aer.com Atmospheric and Environmental Research, Inc.] provide CHI values for live storms through their "hCast-SR" product
* [http://www.mdafederal.com/mda-earthsat-weather MDA Federal] provide a real-time CHI forecasting product

Notes