Some storms take us by surprise
Emily ‘just happened,’ climate researcher says
Tampa Bay residents woke up Monday morning to learn that a patch of bad weather in the Gulf of Mexico had turned into a tropical storm that would strike them within a few hours.
Tropical Storm Emily grew from an area of clouds, wind and rain to a tropical depression by 6 a.m. and a tropical storm by 8 a.m., bringing high winds, lightning and heavy rain to that region and leading Gov. Rick Scott to declare a state of emergency for 31 counties as it swept across the state.
“For the most part, it was a surprise,” said Brian McNoldy, senior research associate at the University of Miami’s Rosenstiel School of Marine and Atmospheric Sciences. “It just happened, and happened rather abruptly. It did catch people off guard.”
By 5 p.m. Monday, Emily had weakened to a tropical depression with winds of 35 mph, heading east-northeast at 11 mph. But in an age of weather satellites, hurricane hunter airplanes and computerized forecast models, we’re not supposed to be surprised by a powerful storm suddenly looming over the coast. But hurricane experts say storms do occasionally form near shore, giving residents little time to prepare and making forecasters look less than infallible. “There are numerous examples of tropical storms developing close to the coastline,” said Dennis Feltgen, spokesman for the National Hurricane Center. “Emily is another example of why it is so important to have a hurricane plan in place, as we don’t always get a three- or even five-day notice on the storm’s approach.”
In 2007 a tropical depression formed 60 miles off the Texas coast and rapidly strengthened into Hurricane Humberto before reaching land. And on July 1, 2014, Tropical Storm Arthur formed just 70 miles off Fort Pierce but spared that city, heading north and strengthening into a Category 2 hurricane, with top winds of 100 miles per hour, before striking North Carolina.
For the most part, however, since such
storms don’t have time to draw energy from warm water before reaching land, they tend to be less destructive than the more common ones approaching from far off. Over the past 20 years in the Atlantic, McNoldy said, six storms formed that made landfall less than a day later.
Most were fairly weak, he said, reflecting the lack of time they had to strengthen before reaching land. Tropical Storm Bill, for example, formed early in the morning of June 16 and made landfall that night on Matagorda Island, Texas, with winds of about 60 mph before rapidly weakening to a tropical depression. Accurate hurricane forecasting, like air-conditioning and mosquito-control programs, has helped take the rough edges off life in South Florida, making the region livable for more than just hardy pioneers. The sudden appearance of Tropical Storm Emily may seem like a visit from the bad old days, when with little warning a 1935 storm destroyed the Florida Keys railroad or, in Texas, a 1900 hurricane leveled Galveston.
But unlike Emily, those catastrophic storms had not suddenly taken shape. They had been growing and strengthening for days, just without much notice from weather forecasters. Storms such as Emily, which form close to land, are likely to cause much less harm.
“They’re going to come ashore pretty quickly so they don’t have much time to intensify,” said Jeff Masters, co-founder and director of meteorology for the web site Weather Underground. “I really can’t remember a case where a storm formed as close to land as Emily did and ended up causing significant damage. They don’t have time to intensify. The biggest-danger storms are the longtrack Cape Verde systems that form off tropical waves off the coast of Africa. Emily was not one of those. It formed from an old cold front.”
Of greater concern than a storm suddenly appearing off the coast is the danger of an existing storm rapidly intensifying just before making landfall. Hurricane Charley, for example, approached the southwest Florida coast with 110-mph winds and then, over the course of three hours, roared to murderous Category 4 strength, with winds of 150 mph when it slammed into the coast.
“The nightmare situation that hurricane forecasters worry about is the rapid intensification close to shore from a storm that is just kind of out there, been out there for a while and suddenly encounters favorable conditions for intensification that were not anticipated,” Masters said.
“Our ability to forecast rapid intensification is poor,” he said. “We saw that last year with Hurricane Matthew. That’s the bigger danger – a Cape Verde type system coming toward shore that suddenly – boom! – explodes from a tropical storm to a Cat 4 or 5 hurricane in a day.”