Hurricane experts say forecasts can be off by 40 miles per day
If forecasters warn that Tampa Bay is in the crosshairs of a hurricane still days away, then much of the rest of Florida should remain on edge, experts said Wednesday.
At the National Hurricane Conference in Orlando this week, experts say forecasting storm tracks has improved each year but could still err by the width of the state’s peninsula.
“Our track forecast errors are still about 40 or 45 miles a day,” said Michael Brennan, senior specialist at the National Hurricane Center in Miami.
“So, two or three days out, we are still talking about 90 to 120 miles, or certainly a big enough difference to mean whether the eye moves over the west coast or the east coast of Florida.”
“The common theme in the lead-up to Hurricane Irma,” Brennan said, “was that the forecast shifted around, and I remember trying to emphasize to people that the threat is still there for everybody.”
Even as Irma barreled into the Keys, the storm was still expected to skirt the state’s Gulf coast and possibly make landfall near Tampa.
Instead, the hurricane swerved inland sooner than expected, paralleled the spine of the state and crossed Interstate 4 near Plant City just before sunrise Sept. 11.
The storm triggered flooding and sewage spills, toppled thousands of trees and left more than 1 million homes in Orange, Seminole, Lake, Osceola, Brevard and Volusia counties without power.
Though Irma’s core was west of Orlando, its wrath extended east to Jacksonville, with tropical-storm winds, heavy rain and coastal flooding.
“Irma was so powerful as it affected the Caribbean islands,” he said. “In Florida you had the realization of what Irma did to Barbuda and the Virgin Islands before it got here, and I think that really focused attention on the risk of the storm.”
The National Hurricane Center has upped its accuracy warning about storm surges, said Cody Fritz, a storm-surge specialist.
He said the center has sought to separate predictions about the ferocity of wind from warnings about the magnitude of coastal flooding.
“Just because you have a Category 1 or Category 2 storm doesn’t mean you will have greater storm surge,” Fritz said. “Storm surge is a product of many variables: angle of approach, track, speed and intensity.”
Although some trial warnings had been done previously, the center first made surge watches and warnings a formal part forecasting in time for Hurricane Harvey, which swamped the Houston area in August.
Surge warnings were issued later with Irma, Maria and Nate.
“With Hurricane Sandy impacting the Northeast, it brought 9 feet of storm surge and killed almost 41 people because of storm surge,” Fritz said.
“If you look at hurricanes Harvey, Nate, Irma and Maria, with all of those storms their maximum surge was between 9 and 10 feet. There were zero deaths related to storm surge.”