NOAA sorts out hits, misses in forecasting Hurricane Ian
As Hurricane Ian bore down on Florida, normally reliable computer forecast models couldn’t agree on where the killer storm would land. But government meteorologists are now figuring out what went wrong — and right.
Much of the forecasting variation seems to be rooted in cool Canadian air that had weakened a batch of sunny weather over the East Coast. That weakening would allow Ian to turn eastward to southwestern Florida instead of north and west to the Panhandle hundreds of miles away.
The major American computer forecast model — one of several used by forecasters — missed that and the error was “critical,” a National Oceanic and Atmospheric Administration postmortem of computer forecast models determined Thursday.
“It’s pretty clear that error is very consequential,” said former NOAA chief scientist Ryan Maue, now a private meteorologist who wasn’t part of NOAA’s postmortem.
Still, meteorologists didn’t miss overall with their official Hurricane Ian forecast. Ian’s eventual southwestern Florida landfall was always within the “cone of uncertainty” of the National Hurricane Center’s forecast track, although at times it was on the farthest edge.
But it wasn’t that simple. Computer forecast models, which weeks earlier had agreed on where Hurricane Fiona was going, were hundreds of miles apart as Ian chugged through the Caribbean.
The normally reliable American computer model, which had performed better than any other model in 2021 and was doing well earlier in the year, kept forecasting a Florida Panhandle
landfall while the European model — long a favorite of many meteorologists — and the British simulation were pointing to Tampa or farther south.
Trying to avoid what meteorologists call the dreaded “windshield wiper effect” of dramatic hurricane path shifts, the official NOAA forecast stayed somewhere in between. Tampa seemed to be the center of possible landfalls.
However, the storm made landfall 89 miles to the south in Cayo Costa. For a large storm, that’s not a big difference and is within the 100-mile error bar NOAA sets. But Tampa was north of the nasty right-hand side of the hurricane eye, so it was spared the biggest storm surge and rainfall.
People wondered why the worst didn’t happen. There are meteorological, computer and communications reasons.
Overall, the European computer model performed best, the British one had the closest eventual Florida landfall but was too slow in timing, and the American model had the highest errors regarding track, NOAA’s Alicia Bentley said during the agency’s postmortem. But the American model was best at predicting Ian’s strength, she said.
The models use a similar physics formula to simulate what happens in the atmosphere. They usually rely on the same observations, more or less. But where they differ is how all those observations are put into the computer models, what kind of uncertainties are added and the timing of when the simulation starts, said University of Miami’s Brian McNoldy.
Another problem, meteorologists say, is that the cone is only where the storm is supposed to be with a 100-mile error radius, but the impacts of rain, surge and high wind will easily hit outside the cone with big storms like Ian.
“The cone was never intended to convey the actual impacts. It was only intended to convey the tracks,” said Gina Eosco, who heads a NOAA social science program that tries to improve storm communications.
So for the first time, NOAA surveyed Florida, Georgia and South Carolina residents before Ian hit and will follow up after to see what risks the public perceived from the media and government information. That will help the agency decide if it has to change its warning messaging, Eosco said.