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All eyes on Hurricane Irma: Using models for risk assessment and storm surge predictions

Allison Preston • DATE: September 13, 2017

As Hurricane Irma gathered strength in the Caribbean, researchers from around the globe scrambled to predict the damage she could leave in her wake. Department of Civil & Environmental Engineering & Earth Sciences (CEEES) graduate student Brian Joyce teamed up with Juan Gonzalez, Ph.D., to predict Irma’s impact on Puerto Rico, the U.S. Virgin Islands, and Southern Florida.

“We’re using Juan’s research to get a general idea of what the wave and surge conditions would look like for Puerto Rico,” said Joyce. “We’re able to do this using the newest available model.”

Specifically, they used the newly released Hurricanes in a Multi-scale Ocean-coupled Non-hydrostatic (HMON) model forecast to provide the hurricane track and intensity data as input for an ADCIRC Coastal Circulation model developed by Gonzalez. ADCIRC, along with a wave model, were used to predict storm surge, and wave conditions near the island.

Before the storm, buoys with wave and water measuring gauges were deployed to gather data as Hurricane Irma passed through the area. Gonzalez had been monitoring this information and comparing it to the model until the storm arrived and knocked out power across the island. That’s when Joyce stepped in.

“I ran the ADCIRC model and used that to predict the waves and water surface Irma Gif Photoelevation near Puerto Rico and the surrounding islands,” said Joyce. “The increased water surface elevation is the storm surge. It looks at how much water is lifted by the pressure and winds of the hurricane. On top of that, you have the waves being produced by the storm.”

Additionally, Gonzalez and Joyce were able to track Irma’s path using Coastal Emergency Risk Assessment (CERA) another ADCIRC Coastal Circulation and Storm Surge Model developed by Louisiana State University, the University of North Carolina, the University of Notre Dame, and a number of other institutions. Using the forecasted storm track and related uncertainty, these models allow researchers to make a risk assessment before the storm hits by predicting what the maximum storm surge and wave height could be.These models have become increasingly accurate, and are relied upon by the Department of Homeland Security, FEMA, and the Coast Guard to assess storm surge risk.

In Gonzalez’s model, he used detailed data for a more accurate prediction. He even factored surrounding coral reef systems into his model due to their capability to cause waves to break differently.

Validating the predictions

After Hurricane Irma passed through Puerto Rico and Southern Florida, Joyce and Gonzalez were able to test how accurate their predictions were.

“According to our model, waves near the coast would reach close to 10 meters in Puerto Rico during this storm, with swells in the deep ocean exceeding 20 meters. We simulated 30-foot waves, and that’s what they saw when the hurricane passed through.”

According to CEEES Department Chair Joannes Westerink, the department is using this information as part of a development called, “The Hazardous Weather Testbed” project with NOAA.

“It’s about understanding how different models work,” said Westerink. “We are going to be running the model from Irma and looking at how accurate it is.”

Another aspect of the project is looking at past storms in an effort to upgrade hurricane and storm-tracking systems. By using historical data, it could make models more detailed and accurate in predicting future storm surge.