Early measurements show the area was hit with record storm surge during Hurricane Helene. That’s when feet of ocean water is pushed ashore by storm winds to land that is normally dry.
Cody Fritz leads the storm surge team with the National Hurricane Center. He said that the information currently available is from tidal gauges.
Unlike buoys, which transmit data from the open water, tidal gauges record water level from the immediate coastline.
There are 11 tidal and river gauges controlled by the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Geological Survey (USGS) that cover parts of Pasco, Pinellas, Hillsborough, Sarasota and Manatee counties. Fritz said eight of the 11 are within "valid tidal areas," or convey relevant information when calculating storm surge.
DASHBOARD: View the tidal gauges here
Preliminary data from the tidal gauges across the Tampa Bay region show that Hurricane Helene likely broke multiple storm surge records, according to a WUSF analysis of NOAA and USGS records.
Mean Higher High Water (MHHW) is the preferred data measurement used by NOAA to measure water levels and predict flooding. In contrast, USGS-operated gauges measure water levels using "gauge height per feet." To accurately compare peak water levels across multiple gauges, Fritz converted USGS water levels recorded from Venice Inlet, Alafia River and Hillsborough River to MHHW values.
Before Helene, the record water level logged by tidal gauges located across the Tampa Bay region totaled just over four feet.
“From what I can tell … you’re getting about six to seven feet above that datum,” Fritz said. “So that’s pretty remarkable and exceptional. And obviously you can see the impacts in that area were pretty devastating.”
All of the tidal gauge stations transmitting water-level data from Clearwater to Venice logged record levels of storm surge during Helene. Six of those topped recorded levels from Hurricane Idalia last August, according to the WUSF analysis.
Still, Fritz said the tidal gauge data does not show the full picture.
The real-time water level readings will be paired with on-the-ground measurements of water lines across coastal regions of Florida’s Gulf Coast, Fritz said.
He said the process can take weeks.
“Where the storm makes landfall you have, generally, the highest storm surge,” Fritz said. "But that doesn't mean you can't have a storm surge spread out all along the Florida coast, as we saw, because the wind field in that storm was just so large.”
The process of verifying data is complicated by the distribution of tidal gauges along Florida’s coast, Fritz said.
Farther north from the Tampa Bay region, including in the Big Bend region where Helene made landfall, Fritz said tidal gauges are sparse.
“There’s not enough of them in the right location to measure the true peak of the storm surge event,” he said. “We’ve had this issue with many storm surge events throughout the years.”
