In the hyper data world of hurricane forecasting, where history is written in millibars and miles per hour, the National Hurricane Center’s 168-year record of Atlantic storms stands as an invaluable index to meteorologists, the insurance industry, government planning departments and, of course, weather geeks.
What’s less known: It gets tweaked a lot.
Since 2008, hurricane researchers have added new storms to the record almost every year, uncovering more information in old ship and weather records that more often than not depict mightier storms. As recently as 2011, they discovered two new hurricanes. Altogether, they’ve identified 82 overlooked tropical storms and three hurricanes swirling in the Atlantic since they began revising old records in the mid-1990s. Dozens more hurricanes have been reclassified to higher and lower categories.
Hurricane Michael, which hit the Florida Panhandle as a Category 4 storm, now enters that record, and in the coming months will get a hard second look. So it’s natural to wonder: Will Michael, too, get revised?
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If it gets upgraded to a Category 5, it would be a very rare event. Only three Cat 5 U.S. landfalls have ever been recorded. Two of those, the 1935 Labor Day storm that hit the Keys and Hurricane Andrew in 1992, were the result of revisions.
“You can’t say for sure, but the odds are high that it would have been a Cat 5 if it had had three more hours over ocean water,” said Colorado State University meteorologist Phil Klotzbach. “It was still on a strengthening trend.”
At landfall, the ferocious storm’s pressure reading was the third lowest on record for a U.S. hurricane, a hint that winds measured just two miles per hour shy of a Cat 5 threshold might turn out to have been stronger.
In the post analysis, forecasters will broaden their focus to look around the storm’s path for data about wind, rainfall, storm surge and damage estimates, said hurricane center spokesman Dennis Feltgen. No longer under the gun for a storm that appeared suddenly and rapidly intensified three times as it took aim at the Panhandle, they’ll be able to take a less stressful look at data collected by hurricane hunter planes and surface wind readings, measured with microwaves, that often require a more nuanced reading.
“It’s not like they necessarily find new sources of data,” said hurricane researcher Brian McNoldy at the University of Miami Rosenstiel School of Marine and Atmospheric Science. He suspects Michael will be reclassified as a Cat 5. “You have the benefit of hindsight and you have more time. You’re not under the constraint of an operational framework.”
The report should be ready early next year.
So what if Michael gets reclassified? It clearly won’t make a difference to places like Mexico Beach and rural Gadsden County, where the hurricane’s pounding winds flattened entire blocks. At least 25 deaths have so far been blamed on the storm.
But for meteorologists building models and making seasonal forecasts, and building officials looking at the toll caused by weaker building codes in the Panhandle, the information is vital. It’s also important for climate scientists tracking global warming.
“There are so many critical questions the hurricane database can answer,” said Chris Landsea, chief of the hurricane center’s Tropical Analysis and Forecast Branch overseeing the re-analysis project. “One is: What is the appropriate building code? Another is insurance and what are the rates that should be charged.”
And while much has been made of the role of climate change in recent storms — Harvey, Irma, Maria, Florence and Michael making landfall one after another seem to portend worsening storms — the record so far fails to support measurably higher winds, he said.
Just a 1 percent increase in strength has been documented since records begin in 1851, Landsea said, which translates to only a couple miles per hour higher wind speed in a storm like Michael. That’s too little to fall outside forecasters’ margin of error.
“Hurricanes today are likely stronger, but what’s most important is how much,” he said. “The uncertainty is much larger than the signal.”
Storm surge is another matter. In places like Florida Bay, where water levels have risen about five inches since 2000, flooding is increasing.
“It’s not huge, especially when you’re looking at an 8, 10 or 12-foot surge, but yeah, it’s there,” McNoldy said.
The lack of influence on one thing but not another should not undermine the larger conclusions about climate change, he added.
“Just because there isn’t much of a signal yet in hurricanes doesn’t mean there won’t be. It doesn’t discredit any of the other aspects of climate change impacts,” he said. “It’s just the record for hurricanes is not long enough to show a lot yet.”
The hurricane center began revisiting the records in the mid-1990s, when Cuban meteorologist Jose Fernandez Partagas, who fled the island in 1961, took on the tedious work as a volunteer.
Dressed in a tie and threadbare jacket, Fernandez Partagas spent long hours in a UM library, scouring old weather maps and newspapers for shipping reports to reconstruct the earliest and sparsest records from 1851 to 1910. After he was found dead in 1997, curled on a library couch where he often worked, and authorities failed to locate family, the hurricane center claimed Fernandez Partagas’ remains. In a gesture of respect, and to honor his work, they later released his ashes into Hurricane Danielle over the Atlantic.
“After hours and hours of work, he’d find a storm nobody’s ever heard of before, and to him that was like finding a relic in an archaeological dig,” NHC meteorologist Peter Black told the Miami Herald at the time.
The center also turned his work into an official project. Landsea, who was on the plane for the ceremony, took over from retired meteorologist Charlie Neumann in 2001.
Among the biggest boons to the project has been an ongoing effort by the National Oceanic and Atmospheric Administration, started in 1985, to build a massive database of ship information. The database includes a trove of wave, wind and pressure data dating back to 1661.
Ship data used to be one of the few ways to get information to land about an approaching storm. But it was also hugely unreliable. When the Labor Day hurricane struck the Keys in 1935, any nearby ships fled, and meteorologists lost the storm for three days. An American barnstormer in Cuba training pilots finally spotted it in time to send a warning.
If ships did collect data, often captains couldn’t report it in time. Even today, forecasters only receive about 5 percent of the available ship data, Landsea said.
Most of the revisions have occurred in storms that predate the 1960s satellite era or other technological advances, including dropsondes in the 1970s, when forecasters used a simple conversion to calculate winds from pressure readings.
“About 10 years ago, there was this realization that it’s not always a one-to-one correlation,” Landsea said. “It depends on how fast the storm is moving, the pressure the hurricane is embedded in, is it higher or lower? And it depends on latitude. And size is a big factor. So you put all these physical factors together, and you can get a very different wind for the same pressure.”
The revisions will only go through 1999, the year before forecasters developed a new technology for interpreting flight-level winds still used today.
“The key with meteorology is it’s not a perfect science,” Klotzbach said. “We’re better than we used to be, [but] every storm is different and little things can cause big changes. There’s going to be a whole lot of research off Michael. I know that’s little consolation to people in Florida, but at the end of the day it’s these kinds of storms that give us a reason to look through things and try to figure out what happens and why.”