Huge hurricane; small Florida peninsula

She was born on the afternoon of Aug. 28, 2017, in a thunderstorm moving off the eastern coast of Africa about 3,300 miles east of the southern tip of Florida.

She headed west near the Cape Verde Islands, like many storms do in this part of the world. She climbed aboard what is known as the hurricane conveyor belt and rode the warm Atlantic waters west to Florida. This belt is where typical African thunderstorms spawn major hurricanes that invade the United States.

Among those destructive Cape Verde storms were Hurricane Hugo in 1989, Hurricane Ivan in 2004 and Hurricane Katrina in 2005 — all among the most powerful and destructive hurricanes to strike the United States. Irma was born in the same area as those three monsters and, 14 days later made, her own mark in history.

Irma grew into a tropical storm on Aug. 30 about 430 miles west of the Cape Verde Islands. Forecasters warned that Irma was poised to become a major Cape Verde hurricane. They were correct in predicting Irma’s place in history. Irma broke many records: maintaining a sustained wind of more than 185 mph for 37 hours, including a direct hit on the tiny Caribbean island of Barbuda; and spending nearly three days as a Category 5 major hurricane.

Many Floridians may believe that Irma will go down as one of the most, if not the most, unpredictable hurricanes on record. Despite aircraft, satellites and super computer tracking models monitoring every aspect of the powerful storm, Irma’s final destructive journey to Florida shifted from along the east coast of Florida, to up the spine of the state, to up the west coast.

In the end, sophisticated upper-level wind patterns kept tugging on Irma until she plowed through Naples as a Category 4 hurricane, curved into the peninsula, and headed north over Marion and Alachua counties. Irma was one of the largest (in diameter) storms ever.

Nate McGinnis, a National Weather Service meteorologist in Jacksonville, said the National Hurricane Center’s five-day forecast turned out to be accurate. Irma’s path actually wavered by only 120 miles. If computer models had predicted five days out that a storm was to hit Mobile, Alabama, for example, and it actually hit Pensacola, most people would consider that an excellent forecast.

But because Florida’s peninsula is only about 120 miles or so across, and Irma covered some 70,000 square miles (5,000 square miles more than all of Florida), then the difference in paths seemed grossly inaccurate. In reality, the National Hurricane Center and forecasters like McGinnis warned for the past week of the three likely scenarios: east coast, up the spine, west coast.

McGinnis said forecasters warned that the scenario of Irma skirting the west coast of Florida would be catastrophic. That is because the storm’s northeast quadrant, a hurricane’s strongest winds, would wreak havoc on the entire state. And it did.

During the last five days of Irma’s march to Florida, the U.S. forecast landfall first focused on Miami, with the storm skirting the east coast on its way to the Carolinas. It then shifted back to the spine-of-Florida track, and then running up the west coast of Florida as a Category 3 hurricane. That led forecasters to warn that Dunnellon and Rainbow Lakes Estates, in southwest Marion, could experience 110 mph winds.

Since Irma followed the western Florida track, Marion County dodged a bullet when the storm went inland in far south Florida, McGinnis noted. It may be hard to believe that Marion dodged a bullet when 140,000-plus electrical customers are without power.

"We knew the east coast scenario would be best for much of Florida,” McGinnis said. Under that scenario, the worst of the winds would be offshore. “When it tracked slightly to the west, we knew Florida would have widespread problems.”

History of NOAA's cones for Irma



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Joe Callahan can be reached at 867-4113 or at joe.callahan@starbanner.com. Follow him on Twitter @JoeOcalaNews.