Hurricane, tornadoes, nor’easter made for a destructive combination

Although Hurricane Irma had significantly weakened by the time she made it to northeast Florida after slamming into the Keys as a Category 4 storm, her track, size and interaction with another storm here meant she still packed quite a punch for St. Johns County and points north.

 

The storm, which tracked north up the state after leaving the Keys and hitting Marco Island, passed St. Johns county to the west and exposed the region to its dangerous northeast quadrant, which, apart from the strong winds, also set down a number of tornadoes.

“It’s where you have the most low level shear,” Phil Peterson, a meteorologist with the National Weather Service in Jacksonville explained on Wednesday.

That shear, Peterson said, came from the strong easterly low level winds that interacted with the weather in the upper atmosphere that was not only moving in a different direction but also at a different speed.

“The strong changes in wind speed and direction makes it very conducive for tornadoes,” he said.

Here, it was a recipe for at least three confirmed tornadoes.

 

St. Johns County Fire Rescue said Wednesday morning that officials had confirmed with the National Weather Service that EF-1 tornadoes had touched down during the storm in Vilano Beach and in the Huguenot Cemetery in St. Augustine. Damage to the Summerhouse Beach & Racquet Club in Crescent Beach was determined to have been caused by a slightly more powerful EF-2 — the third most powerful tornado in the six-point Enhanced Fujita scale that rates tornadoes from EF-0 to EF-5. Tornadoes rated EF-2, according to the National Weather Service website, are capable of creating 111 to 135 mph winds, with EF-1 tornadoes putting down winds of 86 to 110 mph winds.

But, tornadoes aside, Irma also brought destructive winds to the region even when compared to North Florida cities to the west that were closer to the storm’s eye.

That, Peterson said, was because the region was already experiencing a nor’easter “totally independent” of Irma before she made her way into the northern counties and the two storms merged.

“That’s the reason why we had the strongest winds … across north Florida,” he said.

Those winds toppled trees and ripped roofs from homes across the county as the storm passed through.

St. Johns County saw sustained winds around 50 mph with a top wind speed recorded at 75 mph just north of the city.

The Jacksonville International Airport saw an 86 mph gust with the region’s highest recorded gust seen at Mayport at 87 mph. That’s compared to top wind speeds further inland at places like Ocala and Live Oak that saw top winds of 47 and 49 mph respectively, Peterson said.

The storm also brought 10.22 inches of rain to St. Augustine — a figure that Peterson said was pretty consistent across the county.

“It looks like 10 inches is pretty common for St. Johns County and St. Augustine,” he said.

The National Weather Service, which predicted the area would see a 6-foot storm surge, is still working on calculating the true surge, but, Peterson said, that number would be include in a “post tropical cyclone report” due out in the coming days.

 

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