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).
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 74 mph 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:
where the subscript 0 denotes 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 paper in Eos developed a number of indices based on various characteristics of hurricanes. The ReAdvisory team at the reinsurance broker RK Carvill 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 for Hurricane Katrina at 1pm Central daylight time on Sunday, August 28, 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.
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.
|Name||Year||Landfall||NHC advisory number||V(mph)||R(miles)||Saffir–Simpson category||CHI|
Modeled data is available from a number of sources:
- Seasonal data, suitable for use in the insurance and reinsurance community, is provided by Applied Insurance Research
- Atmospheric and Environmental Research, Inc. provide CHI values for live storms through their hCast-SR product
- MDA Federal provide a real-time CHI forecasting product