Hurricane Hermine Poised to Make First Hurricane Strike on Florida in 11 Years

Widespread storm surge was barreling into Florida’s northeast Gulf Coast late Thursday night with the approach of Hurricane Hermine. The warm waters of the eastern Gulf fueled an well-advertised strengthening of Hermine on Thursday afternoon and evening. Hermine was an 80-mph Category 1 hurricane as of the midnight update from the National Hurricane Center. NHC placed the center of Hermine about 40 miles southeast of Tallahassee, FL, just an hour or two from making landfall. Thunderstorms were wrapped around a semi-distinct eye, and heavy bands of rain were clearly evident on radar. An especially intense belt of rain was moving across the northernmost FL peninsula late Thursday.

A Hurricane Warning remained in effect from Suwanee River to Mexico Beach, FL. A variety of other hurricane and tropical storm watches and warnings plastered the Gulf and Atlantic coasts from Florida all the way to northern New Jersey (see below for more on Hermine’s expected track). With Hurricane Gaston also active in the Central Atlantic, we now have multiple hurricanes in the Atlantic for the first time since the first week of September 2012, when Hurricane Leslie and Hurricane Michael were both active. Hermine will be the first hurricane to strike Florida since Wilma hit South Florida as a Category 3 storm in October 2005. Hermine will also be the first hurricane to strike the U.S. since Hurricane Arthur hit North Carolina on July 3, 2014 as a Category 2 storm with 100 mph winds.


Figure X. Hermine approaching landfall in Florida at 6:15 pm EDT September 1, 2016.

Observations this evening
A Personal Weather Station (PWS) at Alligator Point in the northern eyewall of Hermine measured sustained winds of 59 mph, gusting to 78 mph, at 10:25 pm EDT, and had picked up 2.15” of rain since 11 am.

Tyndall AFB Tower C, located about 20 miles south of Apalachicola, Florida, recorded sustained winds of 61 mph, gusting to 79 mph, at 8:50 pm EDT. The anemometer on the tower is at an elevation of 35 meters, which is higher than the standard 10 meters used to reference surface winds, so these winds need to be scaled down to what they would be at a height of 10 meters for a valid comparison to other surface wind measurements.

A PWS on Cedar Key, Florida recorded sustained winds of 44 mph, gusting to 52 mph, at 11:15 pm EDT.

A coastal C-MAN station at Keaton Beach, Florida, in the stronger eastern eyewall of Hermine, measured sustained winds of 45 mph, gusting to 58 mph, at 11 pm EDT.


Figure 2. Regional radar of Hurricane Hermine at 11 pm EDT September 1, 2016, with three time traces of the storm surge at water gages in Apalachicola, Cedar Key and Tampa, Florida. The storm surge (green line) had peaked in Tampa at this time, but was still rising at Apalachicola and Cedar Key. Surge images were taken from NOAA Tides and Currents page for Hermine.


Storm surge a major concern overnight
Even after Hermine’s expected landfall between 1 and 2 am Friday near the head of Apalachee Bay, the strong winds east and south of its center will continue to shove water into the bay and points east along Florida’s Big Bend. This is the bay’s first direct hit from a hurricane in half a century—since Alma, in 1966. NHC warned that surge levels could reach as high as 9 feet in parts of Apalachee Bay and the Big Bend. Fortunately, this is one of the most sparsely settled parts of the Florida coast, but widespread inundation in such places as the flood-prone community of Cedar Key will have a major impact. By 11 pm EDT Thursday, the surge had climbed to 7.2 feet at Cedar Key and 4.0 feet at Apalachicola. HIgh tide will be around 3 am EDT in Cedar Key, which means that the total water level (surge plus tide) could still be rising even after the surge itself peaks.

According to the U-Surge project, headed by storm surge expert Hal Needham, Hermine is likely to produce the highest water level for many locations between St. Marks and Clearwater since the March 1993 “Storm of the Century”. That extremely powerful winter-type storm produced a record surge of 6 to 12 feet across the region.

The forecast for Hermine
Hermine will be rolling along or near the Southeast coast on Friday, emerging off North Carolina’s Outer Banks by Saturday. At that point, Hermine will probably have undergone at least a partial conversion into an extratropical (post-tropical storm), deriving energy from atmospheric dynamics rather than from the heat energy of the ocean.

By later in the weekend, however, Hermine may regain some of its tropical characteristics. Computer models indicate it will slow down Sunday into Monday and perhaps even carry out a tightly looping path east of the Delmarva and south of Long Island, NY. Ocean temperatures are more than 2°C above average in this region. This may be warm enough to allow Hermine’s winds to restrengthen close to hurricane force near its center by Monday or Tuesday, regardless of whether it is classified as a tropical or post-tropical storm by that point. Even if it does become post-tropical, NHC will continue issuing advisories on Hermine as long as it remains a significant threat to land.


Figure 3. The official track forecast for Hurricane Hermine as of 11 pm EDT Thursday. Hermine’s dramatic slowdown is evident in the period from Sunday to Tuesday.

The biggest impact from Hermine after landfall will be a swath of torrential rain stretching from far north Florida to eastern North Carolina, extending from the coast up to 200 miles inland. Flash flood watches are in effect from Georgia to Virginia along a belt northwest of tropical storm warnings. Rains of 5” - 10”, with local totals on the order of 15”, will affect far northern Florida and southern Georgia, with 4” - 8” totals widespread up to the Carolinas. Rains of 1” - 5” and gusty winds will work their way up the Delaware, New Jersey, and New York coastlines from Saturday into Sunday and perhaps Monday--a very unwelcome prospect for Labor Day beach goers.

A zone of very heavy rain (perhaps 5” to 10”) and stronger wind could develop in parts of the eastern Delmarva and/or southern New Jersey on Sunday and Monday, depending on how close ex-Hermine gets to the Mid-Atlantic coast when it slows down.

Hurricane Watch continues for Hawaii ahead of Category 3 Lester
It’s quite rare to have two separate parts of the United States threatened by two hurricanes at the same time. So it was on Thursday night, with Hurricane Lester continuing to bear down on Hawaii. As of 11 pm EDT Thursday (5:00 pm HST), Lester was about 600 miles east of Hilo. Lester is again a major hurricane, with top sustained winds of 125 mph. Computer models agree on taking Lester along a west-northwest path that will parallel the Hawaiian island chain on Saturday. Uncertainty remains over how strong Lester will be at that point (most likely a Category 1 hurricane) and how close its path will be to the islands. The model guidance is now in fairly close agreement on a track just north of the islands, but perhaps within 100 miles—close enough to require continued vigilance.

We’ll be back on Friday with more than one update on the evolving Hermine situation.

Bob Henson and Jeff Masters