Here’s what hurricane categories mean — and how much damage to expect
South Florida’s hurricane forecasters and emergency managers keep getting better at their jobs. They are “shrinking the cone of uncertainty,’’ sharpening track forecasts and giving people more time to prepare.
They can better measure ocean water temperatures directly below a storm in real time, a key component in predicting wind speed and rainfall. They have new radars on hurricane hunter planes. And they are working on better predicting intensity after Michael quickly turned into a Category 5 hurricane in just three days last season.
But with the official start of the hurricane season on Saturday, forecasters and emergency managers still have one big worry: You.
Will the public heed warnings to take storms seriously and properly prepare, even for those systems that don’t develop into raging major hurricanes?
“A tropical storm can produce enormous damage,’’ said Ken Graham, director of the National Hurricane Center. “We need to do a better job communicating the risks. There is no such thing as ‘just’ a Category 1; we have to move away from these labels that may give the public a false sense of security.’’
Category 1 hurricanes alone killed 175 people and caused $103 billion worth of damage over the past 10 years. Lives could have been saved if the public didn’t focus so much on the storm’s classification, and considered instead the broader risks, including storm surge and inland flooding, he said.
Graham was named director last year just two months before the start of the season that produced two monster major hurricanes — Michael and Florence, which killed nearly 100 people and caused $50 billion worth of damage from Florida’s Panhandle up into Virginia. Graham said his mission is to to communicate storm forecasts and risks “in an actionable way,” so that people prepare and evacuate if needed.
A big part of that is raising awareness about storm surge and flood risks. Over the past three years, 83% of all deaths during tropical storms were associated with inland flooding, Graham said.
Many people who live away from coastal areas mistakenly assume they are in safer spots and downplay the risks of heavy rainfall that can quickly turn deadly.
This season is expected again to produce a healthy number of tropical systems and hurricanes. The National Oceanic and Atmospheric Administration (NOAA) is predicting a “near-normal’’ Atlantic hurricane season with between nine to 15 storms estimated from June 1 through Nov. 30. Of those storms, between four and eight could become hurricanes, and of those, up to four could turn into major hurricanes.
For the fifth straight year, the season actually started early, with short-lived Andrea developing last week and then fizzling near Bermuda. These pre-season predictions are based on the best science available. Still, NOAA only gives a 40% chance that the hurricane season will be normal. There is a 30% possibility of above-normal activity, and the same likelihood for a below-normal season.
Uncertainty is high because there are several competing factors that come into play in forecasting hurricanes. Because of the El Niño pattern this year, ocean temperatures will likely be higher than average, and the stronger wind shear that’s expected over the Caribbean would normally have a tendency to suppress hurricane activity. But that global weather pattern is being counterbalanced by higher-than-average sea surface temperatures over regions where hurricanes form, as well as by weaker trade winds associated with a stronger and wetter African monsoon season, which has a tendency to favor hurricanes.
Complicated? Yes, very.
Hurricane forecasting is based on myriad variables. In the end, no matter how precise forecasts may get, the overused cliché — ”it only takes one’’ — is still the best guidance hurricane emergency managers can give in the hopes of attracting people’s attention.
Scientists are constantly working on better connecting the dots on all the available data out there to sharpen forecasts. But predicting the intensity of a hurricane, and how quickly it can strengthen, remains perhaps the biggest challenge. The priority at the National Hurricane Center, NOAA and all other agencies that deal with hurricane preparedness is how to improve intensity predictions, with a special focus on storms that quickly grow into hurricanes.
This year, NOAA is expanding its glider program to provide more data on ocean water temperature as hurricanes develop. The gliders will provide real-time information on how colder or warmer water is weakening or boosting a hurricane, for example.
Up to 20 NOAA gliders will be deployed along the East Coast, in addition to 18 Navy gliders that will also send data to the forecasting models.
“The U.S. has been hit by only four Category 5 hurricanes and every single one of them was a tropical storm just three days out,’’ Graham said.
Investing in new systems to understand how and when storms intensify is crucial, he added. In order to “crack the nut’’ on hurricane intensity predictions, NOAA is upgrading its forecasting models and testing a system that would allow multiple storms to interact with one another in one single model. That will provide a more detailed picture and make forecasts more reliable, said Molly Baringer, deputy director of NOAA’s Atlantic Oceanographic and Meteorological Laboratory.
This new dynamical model, which is still in research phase, produced the most accurate forecast for Hurricane Isaac last year, she said. It was the only model that showed Isaac losing strength early on as it approached the Caribbean, because it was analyzed in conjunction with Hurricanes Florence and Helene.
But when forecasters looked at Isaac separately, as forecasting models are currently set up to do, the prediction was for the storm to remain a Category 1 hurricane longer, Baringer said.
The technology and science are getting more sophisticated every season yet the toughest challenge remains: communicating risks to the public.
NOAA and the National Hurricane Center have enlisted social scientists and behavioral specialists to improve hurricane preparedness communication and, hopefully, persuade people to heed their warnings even if this hurricane season starts out looking like a quiet one.