(This post, originally published at 11:30 a.m., will be updated throughout Saturday. The latest update reflects the 2 p.m. National Hurricane Center advisory)
Large and extremely powerful, Hurricane Irma is sweeping toward Florida, its outer rainbands and strong winds already lashing the Keys and southern peninsula. If the storm reaches its full potential, it could be one of the worst hurricanes in the state’s history.
The latest computer model forecasts suggest the vicious storm is likely to ride up Florida’s west coast, with a combination of destructive winds and a devastating storm surge from the Florida Keys through Naples and Fort Myers and up the coast to Tampa. It’s not clear exactly where the storm will make landfall, but winds well in excess of 100 mph could batter numerous population centers along Florida’s west coast. And coastal waters could rise 10 to 15 feet above normally dry land, completely inundating homes, businesses, and roads.
“In the FLORIDA KEYS, it is a full-scale hurricane emergency,” Bryan Norcross, The Weather Channel’s hurricane specialist, posted to Facebook. “Key West is probably going to get its worst storm in modern history, and perhaps ever.”
He added: “In SOUTHWEST FLORIDA – the NAPLES-FT. MYERS-CAPE CORAL area, the potential exists for the worst hurricane in history. The core of Hurricane Irma, potentially with winds gusting over 150 mph or more, is going to come close. Buildings in Southwest Florida are not, in general, built to withstand these winds.”
Hurricane warnings cover much the Florida peninsula’s coastal areas. Hurricanes watches extended farther north into coastal Georgia and South Carolina.
A storm-surge warning was also issued for much of the South Florida and Central Florida coastlines, past Tampa on the west coast and Melbourne on the east coast. The Hurricane Center said 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.”
Storm Surge forecast Cape Sable to Captiva:10-15 ft!Captiva to Ana Maria Island:6-10 feet;Ana Maria to Clearwater including Tampa Bay:5-8 ft pic.twitter.com/lWfJssScrU
— Ginger Zee (@Ginger_Zee) September 9, 2017
At 2 p.m. Saturday, Irma was positioned about 145 miles southeast of Key West, chugging along to the west at 9 mph. Late Saturday, the storm is predicted to turn north, passing over the Keys and then up the west coast. But slight shifts in this projected track were still possible.
Even though the most severe conditions were expected on Florida’s west coast on Sunday, outer rain bands had already raked across Miami Saturday morning, with winds gusting over 60 mph and at least 25,000 homes losing power. In the Keys, winds were gusting over 50 mph early Saturday afternoon.
Because of the shift in the most likely storm track to the west, Southeast Florida is 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 the storm would bring “life-threatening wind impacts to much of the state.”
A computer model projection showed nearly 2 million power outages were possible in Florida and the Southeast U.S. from the storm’s winds.
Irma’s peak winds had lessened some on Saturday morning, with peak winds of 125 miles per hour, as it center scraped over Cuba’s north coast, interfering with its circulation.
But once Irma moves back over the water of the Florida straits, some of the warmest in the world (nearly 90 degrees), it is forecast to restrengthen some. Both computer models and the National Hurricane Center predict Irma to make landfall as a very dangerous Category 4 hurricane with 140 mph peak winds.
Tropical-storm-force winds are already hitting parts of southern Florida and the Keys, despite Irma’s storm center being approximately 200 miles south of Miami. Conditions will continue to deteriorate throughout the day Saturday as Irma starts to make its long awaited turn north.
The forecast track has once again shifted to the west slightly, with the storm expected to cross the Florida Keys (near Marathon) on Sunday morning, before moving up the west coast Sunday afternoon and evening, battering Marco Island, Naples, Cape Coral, Ft. Myers, Port Charlotte, Sarasota and Tampa.
The storm track could still shift slightly west or east. If it shifts west, the center could stay over the Gulf of Mexico until hitting northern portion of Florida’s Gulf Coast on Sunday , perhaps in the big bend area. If it shifts east, it would ride up the spine of the peninsula, weakening faster, but unleashing hurricane force winds on both sides of the state.
Effects on Florida
Here’s a guide to what is most likely and where…
Timeframe for worst conditions: Saturday evening through Sunday evening
Biggest impact threat: Storm surge and destructive winds
The Keys are poised to take a direct and devastating hit from Irma. Winds will be on the increase all day on Saturday, with sustained hurricane force winds up to 120 to 140 mph expected after midnight Sunday. Catastrophic storm surge levels of 10 feet or more more could inundate the entire area in a manner similar to the destruction caused by Hurricane Donna in 1960, which devastated the Keys. As a result of the extreme danger that Irma poses to the area, the National Weather Service office in Key West issued some of the strongest language you will ever see from a weather warning.
Southwest Florida to Tampa Bay
Timeframe for worst conditions: Sunday
Biggest impact threat: Storm surge and wind
Each shift in Irma’s track has spelled more bad news for the Southwest Florida. The Tampa Bay area hasn’t had a direct hit from a hurricane since 1921, but this part of the state is home to some of the most vulnerable real estate to flooding.
The current forecast track has Irma making her final landfall in between Naples and St. Petersburg. Given the current forecast, sustained tropical storm force winds are expected by Saturday night, with winds gradually increasing overnight. The Naples area may well be hit the by the strongest winds, with sustained hurricane force winds of 115 to 135 mph with higher gusts moving in by Sunday morning.
Storm surge will be an especially large concern, with upward of 10 to 15 feet of surge possible as the center of Irma passes by. “This is fast moving, destructive water,” the Weather Channel’s Norcross said. “You cannot drive through it and you cannot stand in it. It will sweep buildings away. Storm surge is the deadliest hazard in a hurricane.”
Exceptional storm surge flooding possible in Naples & south including Marco Island
— Greg Diamond (@gdimeweather) September 9, 2017
Miami/Ft. Lauderdale/Dade County
Timeframe for worst conditions: Late Saturday night through Sunday evening
Biggest impact threat: Heavy rain and strong winds
Despite the continued shift westward in Irma’s forecast track, the Miami area is by no means off the hook. Sustained tropical force winds will continue coming in waves throughout the day as spiral bands cycle in, with hurricane force wind gusts embedded in some of the stronger rainbands. The worst conditions will move in after midnight Sunday and persist through much of the day, with sustained winds of 60-plus mph with gusts in excess of 75 mph. Rainfall totals will range from 8 to 15 inches, with the bulk of the rain coming in bursts where rainfall rates could reach four inches per hour.
While still a concern, storm surge will not be as serious here as in other parts of the state due to a combination of a lesser rise in water (3 to 6 feet) and deeper offshore waters.
Timeframe for worst conditions: Early Sunday morning through Monday morning
Biggest impact threat: Heavy rain/strong winds
Inland areas will not be immune to impacts from Irma. As it has been noted, Irma is an extremely large storm, with hurricane force winds extending some 90 miles from the center. As the storm begins to interact with more land, it will lose some of its peak wind speeds but actually grow in physical size. Sustained tropical force winds will begin striking Orlando and central Florida by Saturday afternoon, with hurricane force wind gusts possible late Sunday night.
The somewhat forgotten danger with landfalling hurricanes in the extreme rainfall that can develop over inland areas. Flooding will certainly be a concern as rainfall totals are expected to be in the range of 8 to 18 inches by Monday.
Potential effects on Georgia and the Southeast U.S.
Beyond Florida, there is the likelihood for damaging winds, flooding rain and a coastal storm surge farther north. Georgia is likely to see some of the worst effects Sunday night into Monday.
Irrespective of Irma’s track its circulation is enormous, so it would still likely push a significant storm surge toward the Georgia and South Carolina coasts.
Tropical-storm and even hurricane-force winds are also likely to affect much of Georgia, with downed trees and power outages could be a big problem there. Strong winds could expand into southern South Carolina and eastern Alabama as Monday wears on.
Heavy rains are also likely to swell north and west into Alabama, Tennessee and western North Carolina Monday into Tuesday.
“All areas seeing heavy rainfall from Irma will experience a risk of flooding and flash flooding,” the Hurricane Center said.
Irma’s path so far
Just after 9 p.m. Friday, Irma made landfall on the north coast of Cuba as a Category 5 hurricane, 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 reported at Falla, Cuba in the eyewall of 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.
— Bill Karins (@BillKarins) September 8, 2017
A devastating storm surge and destructive winds had also likely battered the southeastern Bahamas, near Great Inagua Island.
— NOAA Satellites PA (@NOAASatellitePA) September 8, 2017
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.
Wednesday afternoon, the storm’s eye had moved over Virgin Gorda in the British Virgin Islands, and its southern eyewall raked St. Thomas in the U.S. Virgin Islands.
— NOAA Satellites PA (@NOAASatellitePA) September 6, 2017
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.
Tuesday night and Wednesday morning, the hurricane passed directly over Barbuda and St. Martin in the northern Leeward Islands, the strongest hurricane ever 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 place in history
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).
Late Tuesday, its pressure dropped to 914 millibars (the lower the pressure, the stronger the storm), ranking as the lowest of any storm on record outside the Caribbean and Gulf of Mexico in the Atlantic basin.
The storm has generated the most “accumulated cyclone energy,” a measure of a storm’s duration and intensity, of any hurricane on record.
Without a doubt, the World Meteorological Organization will retire the names Harvey and Irma after this season. While there have been several instances of consecutive storm names getting retired (Rita and Stan 2005, Ivan and Jeanne 2004, Isabel and Juan 2003, Luis and Marilyn 1995), the United States has been hit by more than one Category 4+ hurricane in a season only one time: 1915. Two Category 4 hurricanes hit in Texas and Louisiana six weeks apart that year.
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.
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