A reinsurance brokerage unveiled a new classification system today that it claims gives a more accurate assessment of a hurricane's potential to cause damage than existing measures.

The Hurricane Damage Potential Index will allow insurers predict hurricane damage more realistically and effectively in the future as hurricanes approach landfall, said Dr. Steve Smith of the ReAdvisory unit of London-based Carvill reinsurance intermediaries.

The current Saffir-Simpson Hurricane Scale classifies hurricanes in categories from 1 to 5, while the HDPI provides a sharper picture of potential damage for the insurance and related industries, according to Carvill.

“For example, meteorologists have had to quantify Saffir-Simpson categories as either 'strong' or 'weak'. As a case in point, Hurricane Katrina was a strong Category 3 storm at landfall, but this did not provide a real guide to the actual physical impact,” Dr. Smith said.

Under Saffir-Simpson a Category 3 involves barometric pressure of 27.91 to 28.49 and winds from 111 to 130 mph storm surge of 9-12 feet and “damage extensive.”

The HDPI incorporates additional factors, such as sustained wind speed, and the radius to hurricane force winds. It is also a continuous measurement, rather than a discrete scale, starting from one and it has no maximum value, although it would probably top off at around 35.

Dr. Smith noted that Hurricane Wilma in 2005 was at one point in its life the strongest storm on record.

“However, the HDPI highlights that, at its strongest, Hurricane Katrina had more potential for damage than Wilma, despite its lower wind speed, in view of the fact that Katrina was a far wider storm,” Dr. Smith said. “The Saffir-Simpson scale would be unable to make this distinction clear.”

Using HDPI, at landfall, Katrina would have been ranked a 13 while at its maximum rating would have come in at 27. Hurricane Andrew was an 18.5 at landfall.

Dr. Smith said he has long been concerned that the Saffir-Simpson scale does not entirely address the needs of the insurance community.

“Analysis of hurricanes from the last 20 years using the two scales has shown that the HDPI correlates much more closely to the actual industry insured loss for each storm than Saffir-Simpson.

“But importantly, the HDPI provides a more complete assessment of the 'strength' of a hurricane while still being based on publicly available data,” Dr. Smith said.

For the time being, the HPDI will be used primarily in Carvill's daily summary of storms as they are occurring. Any effort for it to gain widespread currency would involve getting the National Weather Service to switch to the system for which there could be some effort in the future, Dr. Smith said.

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