As Hurricane Michael moves toward what will likely be a deadly interaction with the panhandle of Florida, one of the primary questions facing those who will be impacted is just how the storm will manifest itself.
Will the storm, upgraded to a category 4 Wednesday morning, hit hard and race on through Florida quickly en route to Georgia, South Carolina and points northeast? Or will it do what two of the most damaging hurricanes of recent memory have done?
Hurricane Harvey hit southern Texas in August 2017 and then all but stopped moving, prompting flooding and inflicting damage for about two weeks. The same held for Florence, which hit North and South Carolina just six weeks ago and lingered for three destructive weeks.
Science is looking for answers.
“There is a lot we still don’t understand about how hurricanes work,” William Boos, associate professor of earth and planetary sciences at UC Berkeley, said. “We don’t know what determines how fast they will move once they hit land.
“Are we going to have more Harveys and Florences where they just hang out for a while?”
Some things science is clear about. There has been a rise in sea level. Ocean temperatures have warmed. Atmospheric humidity, which feeds hurricanes to produce rain, has risen. Those are problems, because the longer a storm is over land, the greater the chance of damage.
“That’s what was remarkable about both Harvey and Florence,” Boos said. “So much damage was due to rainfall. Historically, most has been due to storm surge.”
Storm surge is primarily caused by winds pushing water ashore above its norms. For Hurricane Michael, which is expected to make landfall at midday Wednesday, the winds were at 120 mph as of midday Tuesday and the storm surge was predicted to be 13 feet.
Climate change, which has led to oceans warming and sea levels rising, is at the heart of the current spate of hurricane damage. But there is a lesser-appreciated aspect to the issue. From the Gulf Coast to the Eastern Seaboard, homes and business have for centuries been built close to the shore, and rising seas haven’t changed that.
“You can reduce the damage,” Boos said. “It’s been dominated by the fact that we are putting infrastructure and wealth in the path of the storms. There’s a huge flux of population moving into coastal region.”
It’s true on the West Coast, too, but the West Coast is spared hurricane problems for the most part because the water offshore is colder than on the other side of the continent. And it is warm water that fuels hurricanes.
“If you try to swim off the coast of California without a wetsuit, you know why we don’t get hurricanes here,” Boos said. “Where it is warmer, along the west coast of Mexico, they do have them.”
Boos warns against putting too much faith in the given category of any hurricane. If one moves slowly and sticks around long enough, a lesser category storm can do major damage.
“Much of the focus is on the wind speed,” he said. “The category given to a hurricane is all about its wind speed. It’s relative to the storm surge. But it may be misguided. The broader point is that the very intensity you think of with the wind is only part of it. The amount of water the storm produces is an important factor.”
Will Hurricane Michael sprint through Florida, Georgia and the Carolinas? Or will it linger and compound the damage? Some projections are leaning toward a quick- moving storm.
Boos said “this is a fairly large storm, and it’s been a while since Florida has been hit by a hurricane this strong.”
Fast or slow, neither eventuality is promising.