After slamming Keys, Irma to batter Florida Peninsula, with ‘catastrophic’ storm surge feared

10 September 2017 9:51 AM

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The extremely dangerous Category 4 Irma crashed into the Florida Keys on Sunday morning, unleashing violent wind gusts and storm-surge flooding. Florida’s western coast next faces Irma’s wrath, and forecasters fear this storm will go down as one of the worst in the state’s history.

Winds in excess of 100 mph could batter numerous population centers along the western coast, including Naples and Fort Myers and up the coast to Tampa. And coastal waters could rise 10 to 15 feet above normally dry land, inundating homes, businesses and roads, an “imminent danger,” according to the National Hurricane Center.

“The Keys through Tampa will likely experience the worst storm surge event that area has seen in generations,” said Bill Read, a former Hurricane Center director.

When Irma crashed into the Keys early Sunday, following Hurricane Harvey’s assault in Texas, it marked the first time on record that two Category 4 storms had made landfall in the United States in the same year.

Because of the storm’s magnitude, the entire state of Florida is being severely affected by damaging winds and torrential rains. Tropical storm and hurricane conditions were also predicted to spread into the Florida Panhandle, eastern Alabama, much of Georgia, and southern South Carolina by Monday.

At 11 a.m. Sunday, the eye of Irma was heading toward southwest Florida, centered 80 miles south-southeast of Naples. The storm, packing peak winds of 130 mph, was crawling to the north at 8 mph. It was predicted to move up the west coast of Florida through the day Sunday and into Sunday night.

Spiral bands were also unleashing tropical-storm-force winds in Southeast Florida. Sustained winds in Miami and Fort Lauderdale were 40 to 50 mph Sunday morning, gusting to 60 to 70 mph.

The National Weather Service in Miami warned that gusts could reach 100 mph at the upper floors of high-rise buildings, and an isolated gust hit 100 mph at the University of Miami, according to the Weather Channel. Nearly 1.1 million customers were without power, mostly in Miami-Dade, Broward and Palm Beach counties.

As the storm’s spiral bands walloped South and Central Florida, the potential for tornadoes arose in the swirling air, and the Weather Service issued watches and warnings. Witnesses captured photographs of a twister moving off the ocean toward Fort Lauderdale on Saturday evening.

Hurricane warnings cover all of Florida except the western Panhandle, where a tropical storm warning was in effect.

A storm-surge warning was also issued for much of the Florida Peninsula (except for a small section from North Miami Beach to Jupiter Inlet), and even extended up the Georgia coast into southern South Carolina. The Hurricane Center said that this would bring the risk of “dangerous” and “life-threatening” inundation and that the threat was highest along Florida’s southwest coast and in the Florida Keys, where it said the surge is expected to be “catastrophic.”

“In SOUTHWEST FLORIDA — the NAPLES-FT. MYERS-CAPE CORAL area, the potential exists for the worst hurricane in history,” Bryan Norcross, the Weather Channel’s hurricane specialist, posted to Facebook.

Because of the shift in the most likely storm track to the west, Miami and Southeast Florida were most likely to miss the storm’s intensely destructive core, known as the eyewall, where winds are strongest. Even so, because of Irma’s enormous size, the entire Florida Peninsula and even the Panhandle were likely to witness damaging winds. The National Hurricane Center warned that the storm would bring “life-threatening wind impacts to much of the state.”

Conditions will continue to deteriorate Sunday over Florida from south to north as Irma chugs up the coast.

The storm will move up the west coast on Sunday afternoon and evening, walloping Marco Island, Naples, Cape Coral, Fort Myers, Port Charlotte, Sarasota and Tampa.

The storm track could still shift slightly west. If it shifts west, the center could stay over the Gulf of Mexico until hitting the northern portion of Florida’s Gulf Coast on Sunday night, perhaps in the Big Bend area south of Tallahassee.

Models run Saturday night suggested that a landfall between Naples and Tampa on Sunday afternoon or evening was plausible, but pinpointing the exact landfall location is difficult for a storm predicted to parallel a long coastline.

A catastrophic storm surge of 5 to 10 feet or more is expected to inundate much of the island chain. Heavy rain will add to the water issues, as anywhere from 5 to 10 inches of additional rain will fall before the worst of the storm is over. Unfortunately, the damage potential on the Keys could be landscape-altering after taking a direct hit from this storm.

The Miami area was in the thick of it late Sunday morning. Irma has been battering Florida’s southeastern coast with strong thunderstorms embedded in the storm’s outer rainbands since Saturday evening. Sustained winds of 45 to 70 mph with gusts of 80-plus mph will last well into Sunday afternoon.

Swirling winds at all levels of the atmosphere have also increased the chances of tornadoes developing at any point on Sunday, especially in locations right along the water. Rainfall totals of four to eight inches or more are expected on Sunday alone, which may exacerbate localized flooding. With Irma’s last-minute track shift to the west, the storm surge won’t be as big of a concern here as it is elsewhere, with a two- to four-foot surge expected along much of Florida’s east coast.

Irma’s ultimate destination will be along the west coast of Florida. This means the conditions will deteriorate rapidly from Naples to Tampa Bay throughout Sunday afternoon. However, Irma’s path will take it parallel to the west coast of Florida, keeping the entire region engulfed in the dangerous northeast quadrant of the storm, where winds are strongest. Sustained winds of 35 to 60 mph are forecast through Sunday afternoon, with sustained hurricane force winds and gusts over 100 mph arriving to Naples by Sunday evening and in St. Petersburg/Tampa Bay several hours later.

The most dangerous hazard for this region will be the extreme storm surge. Nowhere in the entire state will the storm-surge levels be higher than along the gulf-facing coast, with storm surge totals of eight to 12 feet and locally up to 15 feet forecast. Any coastal city from Tampa Bay south to Naples is at risk, with historic flooding (the likes of which haven’t been seen in this area since Hurricane Donna in 1960) threatening thousands of people and structures.

Inland areas won’t escape the effects of Irma. The storm is extremely large in size, with tropical-storm-force winds extending outward over 200 miles from the center. The wind speeds in central Florida and the Orlando area will start to pick up by late Sunday afternoon, with sustained winds of 40 to 60 mph and gusts of 70-plus mph lasting from late Sunday night through Monday morning.

Heavy rain will also cause problems, with a general six to 12-plus inches of rain expected by the time the storm is over. The threat of tornadoes will increase by Sunday night, as well, as the storm’s center tracks north along the west coast of Florida.

Time frame for worst conditions: Sunday evening through Monday afternoon.

The northeast portion of Florida will be spared the worst of Irma but won’t escape unscathed. Sustained tropical-force winds of 40 to 55 mph will overspread the area from Daytona Beach to Jacksonville by Sunday evening, with the worst winds (gusts up to 70 mph) occurring overnight. Heavy rain will be a story line here as six to 10-plus inches of rain is expected to fall in a relatively short period.

As with other parts of the state, the tornado threat will peak overnight on Sunday as Irma’s storm center tracks northward.

Storm-surge values will be elevated (two to four feet) but should result in only minor to moderate coastal flooding.

Time frame for worst conditions: Monday morning through Tuesday morning.

Hurricane warnings extend well into Georgia, covering over half of the state. Parts of southern South Carolina also are under a hurricane warning, with Irma poised to maintain its hurricane-force strength for several hours after landfall.

Sustained tropical force winds of 25 to 45 mph will spread over Georgia from south to north starting late Sunday night. The strongest sustained winds (40 to 50 mph) with gusts of 60-plus mph will move in on early Monday morning, lasting through Monday evening. This includes Atlanta, which is under a tropical-storm warning, where sustained winds of 25 to 40 mph with gusts up to 60 mph will occur from about 10 p.m. Sunday night to about 5 p.m. Monday afternoon. This could lead to downed trees and outages.

Heavy rain is also expected, with storm totals of six to 10 inches forecast, the bulk of which should fall Monday.

Storm surge along the Georgia/South Carolina coast will be a hazard, as well, with the Hurricane Center predicting a surge of four to six feet. Of particular concern is the duration of the storm surge. Persistent onshore winds will extend the surge component here, with elevated water levels potentially lasting up to 36 hours.

On Sunday, the storm officially made landfall at Cudjoe Key at 9:10 a.m. as a Category 4 hurricane. Winds over the Keys raged, gusting to at least 94 mph in Key West (before the wind instrument failed) and up to 120 mph in Big Pine Key. Witness video showed the rising storm surge flooding Key West streets.

Before its encounter with the Keys, Irma made landfall on the north coast of Cuba as a Category 5 hurricane just after 9 p.m. Friday, with maximum sustained winds of 160 mph. It became that country’s first Category 5 hurricane since 1924. Fueled by the extremely warm ocean temperatures, Irma reintensified to the maximum hurricane classification level after weakening slightly on Friday afternoon.

As it scraped Cuba’s north coast early Saturday, it produced a sustained wind gust of 118 mph, and a gust to 159 mph was reported at Falla, Cuba, in the eyewall of the hurricane.

On Friday, before making landfall along Cuba’s north-central coast, Irma passed north of Haiti and then between Cuba’s northeast coast and the Central Bahamas.

Thursday evening, the center of the storm passed very close to the Turks and Caicos, producing potentially catastrophic Category 5 winds. The storm surge was of particular concern, as the water had the potential to rise 16 to 20 feet above normally dry land in coastal sections north of the storm center, causing extreme inundation.

A devastating storm surge and destructive winds had also probably battered the southeastern Bahamas, near Great Inagua Island.

Through early Thursday, the storm had battered islands from Puerto Rico to the northern Lesser Antilles.

While the center of Irma passed just north of Puerto Rico late Wednesday, a wind gust of 63 mph was clocked in San Juan early Wednesday evening, and more than 900,000 people were reported to be without power. In Culebra, Puerto Rico, a small island 17 miles east of the main island, a wind gust registered 111 mph in the afternoon.

Early Wednesday afternoon, a wind gust to 131 mph was clocked on Buck Island and 87 mph on St. Thomas in the U.S. Virgin Islands.

On Tuesday night and Wednesday morning, the hurricane passed directly over Barbuda and St. Martin in the northern Leeward Islands, the strongest hurricane recorded in that region and tied with the 1935 Florida Keys hurricane as the strongest Atlantic storm to strike land.

As Barbuda took a direct hit, the weather station there clocked a wind gust to 155 mph before it went offline.

The storm also passed directly over Anguilla and St. Martin early Wednesday, causing severe damage.

Irma’s peak intensity (185 mph) ranks among the strongest in recorded history, exceeding the likes of Katrina, Andrew and Camille — whose winds peaked at 175 mph.

Among the most intense storms on record, it trails only Hurricane Allen in 1980, which had winds of 190 mph. It is tied for second-most intense with Hurricane Wilma in 2005, Hurricane Gilbert in 1988 and the 1935 Florida Keys hurricane.

The storm maintained maximum wind speeds of at least 180 mph for 37 hours, longer than any storm on Earth on record, passing Super Typhoon Haiyan, the previous record-holder (24 hours).

The storm has generated the most “accumulated cyclone energy,” a measure of a storm’s duration and intensity, of any hurricane on record.

Irma’s landfall pressure of 929 millibars in the Florida Keys was the lowest for any U.S. landfalling hurricane since Katrina (920 millibars) and for a Florida landfall since Andrew (922 millibars). It ranks as the seventh-lowest pressure of any U.S. landfalling storm.

Capital Weather Gang hurricane expert Brian McNoldy contributed to this report. Credit to tropical-weather expert and occasional Capital Weather Gang contributor Phil Klotzbach for some of the statistics in this section.

Source: washingtonpost.com

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