Set to Impact Entire West Coast of Florida, Irma Raises Significant Storm Surge Concerns

14:30 UTC  Sunday, September 10

Tom Sabbatelli, hurricane risk expert – RMS

As Hurricane Irma makes landfall in the Florida Keys as a Category 4 storm, the range of the storm’s possible future tracks in the latest RMS HWind forecast product is rapidly narrowing. It is now certain that Irma will track along Florida’s west coast and impact all major population centers from Naples to Tallahassee.

What is less certain is the length of time Irma’s center will remain over water, with some scenarios projecting a landfall near Fort Myers and others delaying the landfall until Irma reaches the state’s Big Bend region.

Figure 1. RMS HWind Forecast for Hurricane Irma, as of 00:00 UTC on September 10, 2017. Impact probabilities (upper right) represent the probability of the storm’s center passing within 50 nautical miles of each city.

Each scenario has significant implications for insured losses.

A landfall further south would bring ashore Irma’s most intense wind and storm surge in areas between Naples and Tampa, but would weaken the system more rapidly as it moves northward. Conversely, a track located further offshore may reduce hazards experienced on land but would impact a broader area as the storm weakens slowly. An offshore track also increases the likelihood of hurricane force winds impacting the Florida panhandle.

The latest RMS modeling indicates that there is a 10 percent chance of insured wind losses from Irma exceeding US$60 billion. This threshold continues to decrease from previous guidance, reflecting the increasing probability of a predominantly offshore storm track.

However, it is imperative to stress that today’s estimate, like all previous estimates, does not include contributions from storm surge nor post-event loss amplification (PLA). As mentioned in yesterday’s update, concerns for significant storm surge and PLA are increasing. Within the range of possible scenarios we are looking at today, some feature storm surge contributions to the insured loss of up to 30 percent**, inclusive of coverage leakage and partial flood coverage. Furthermore, PLA could further inflate insured loss by up to 15 percent**.

**Estimates of storm surge or PLA are preliminary, as their ultimate contributions are heavily conditional on the storm’s final behavior. RMS will advise on these aspects of the event as the situation evolves.

For more information on RMS HWind, RMS clients can consult their account representatives for details on the latest RMS HWind updates.

Senior Product Manager, Model Product Management
Tom is a Senior Product Manager in the Model Product Management team, focusing on the North Atlantic Hurricane Model suite of products. He joined RMS in 2009 and spent several years in the Client Support Services organization, primarily providing specialist peril model support. Tom joined RMS upon completion of his B.S. and M.S. degrees in meteorology from The Pennsylvania State University, where he studied the statistical influence of climate state variables on tropical cyclone frequency. He is a member of the American Meteorological Society (AMS).

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