The final report on Major Hurricane Irma was just issued by meteorologists John Cangialosi, Andrew Latto, and Robbie Berg at the National Hurricane Center in Miami. The report is rather long. I’ll try to break down some of the more important information for our area.

Irma was a long-lived Cape Verde hurricane that reached category 5 intensity on the Saffir-Simpson Hurricane Wind Scale. The catastrophic hurricane made seven landfalls, four of which occurred as a category 5 hurricane across the northern Caribbean Islands. Irma made landfall as a category 4 hurricane in the Florida Keys and struck southwestern Florida at category 3 intensity. Irma caused widespread devastation across the affected areas and was one of the strongest and costliest hurricanes on record in the Atlantic basin.

Irma originated from a tropical wave that departed the west coast of Africa on Aug. 27, 2017. Six hours later, it became a tropical storm and was named Irma. In about 24 hours, Irma was a hurricane about 400 miles west of the Cabo Verde Islands. Irma became a major hurricane only 48 hours after forming!

The hurricane reached its maximum intensity of 178 mph on Sept. 5, when it was located about 70 mi east-southeast of Barbuda. As a category 5 hurricane, Irma made landfall on Barbuda on Sept. 6 with a minimum pressure of 914 mb.

WINDS

St. Martin: The estimated landfall intensity of 178 mph Sept. 6.
Bahamas: The estimated landfall intensity of 155 mph on Little Inagua Island at on Sept. 8.
Cuba: The estimated landfall intensity of 165 mph near Cayo Romano on Sept. 9.
The Florida Keys: The estimated landfall of 132 mph on Sept. 10 near Cudjoe Key.
Southwest Florida: The estimated landfall intensity of 115 mph on Sept. 10 near Marco Island.

Hurricane Irma wind gusts

STORM SURGE FLOODING

Cuba reports that Irma produced significant coastal flooding along the north coast of Cuba due to storm surge and large waves. In Ciego de Ávila Province, the sea rose by 10 to 11.5 ft and penetrated inland more than 0.5 miles from the coast. Unprecedented storm surge flooding occurred in portions of La Habana Province, in some cases surpassing the coastal floods produced by the Storm of the Century (March 1993) and Hurricane Wilma (October 2005). Water levels reached 7.4 ft in some locations.

In the Florida Keys, the storm surge produced maximum inundation levels of 5 to 8 ft above ground level for portions of the Lower Florida Keys from Cudjoe Key eastward to Big Pine Key and Bahia Honda Key, near and to the east of where Irma's center made landfall.

On the Southwest Coast of Florida, surge levels of 6 to 10 ft above ground level hit the unpopulated coast of between Cape Sable and Cape Romano, within Everglades National Park.

The combined effect of storm surge and the tide produced maximum inundation levels of 1 to 2 ft above ground level along the west coast of Florida north of Charlotte Harbor to Apalachee Bay.

In Tampa Bay, generally recorded peak water levels of a little more than 1 ft with the highest observation being 1.7 ft at the McKay Bay Entrance near Downtown Tampa. Offshore winds on the northern side of Irma’s circulation initially caused water levels to recede below normal levels along much of the west coast of Florida, including Tampa Bay. In fact, some normally submerged areas went virtually dry, allowing people to (inadvisably) walk out onto the sea or bay floor, while also stranding marine vessels and even manatees.

RAINFALL

Irma produced heavy rain across much of the state of Florida, and rainfall totals of 10 to 15 inches were common across the peninsula and the Keys. The maximum reported storm-total rainfall was near Ft. Pierce, Florida, in St. Lucie County, where 21.66 inches of rain was measured between 9 and 12 September.

The heavy rainfall caused flooding of streets and low-lying areas across much of the Florida peninsula. In Indian River County, 12 people were rescued from flood waters, and in Orange County residents were rescued from flooded homes.

Hurricane Irma rainfall totals

TORNADOES

Irma produced 25 confirmed tornadoes: 21 in Florida and 4 in South Carolina. Of the tornadoes, 3 were EF-2, 15 were EF-1, and 7 EF-0. The majority of the tornadoes occurred along the east coast of central and northern Florida. A EF-2 tornadoes touched down in Mims, Florida and caused severe roof damage to numerous homes and uprooted many trees in the area. An EF-2 tornado struck near Crescent Beach, Florida. This tornado caused significant structural damage to vacation rentals in the area.

Another EF-2 tornado hit Polk City, Florida, knocking down seven high power transmission poles. Weaker but still notable tornadoes in Florida included an EF-1 that went through Miramar and caused tree and roof damage. An EF-1 tornado affected St. Augustine causing significant damage to a cemetery. Another EF-1 tornado occurred in Merritt Island and damaged numerous homes and a church.

DEATHS

Irma caused 44 deaths across the Caribbean Islands and the southeastern United States. The majority of the casualities were in the Caribbean Islands, where Irma's winds were the strongest. Eleven direct deaths were reported combined in Saint Martin and Saint Barthelemy, nine in Cuba, four in Sint Maarten, four in the British Virgin Islands, three in the U.S. Virgin Islands, three in Barbuda, one in Barbados, one in Haiti, and one in Anguilla.

In the United States, seven direct deaths were reported, and an additional 85 indirect deaths occurred, 80 of which were in Florida. Hundreds more were injured before, during, or after the hurricane. About 6 million residents in Florida were evacuated from coastal areas.

There were four direct deaths in Florida from Hurricane Irma. Two occurred in Duval County, where a 59-year-old male and a 54-year-old female drowned due to fresh water flooding when their tent was submerged in water in the woods. An 89-year-old male drowned in Manatee County when he went outside during the hurricane to secure his boat to the dock and fell into a canal.

In Broward County, an 86-year-old male opened the front door during the hurricane and a gust of wind caused him to fall and hit his head fatally. Of the 80 indirect deaths in Florida, a combination of falls during preparations for Irma’s approach, vehicle accidents, carbon monoxide poisoning from generators, chainsaw accidents, and electrocutions were mainly to blame. In Broward County, 14 indirect deaths occurred in one nursing home due to overheating when air conditioners failed as power faltered.

Near Orlando in Osceola County, about 4,000 structures were damaged, and the estimated cost in that county is near $100 million. Irma also caused significant damage to the southwest and central Florida orange groves, totaling about $760 million.

FORECAST

Official forecast track errors were roughly 30-40 percent lower than the mean official errors for the previous five-year period for all forecast times. At 96 and 120 hours, errors were larger than their five-year averages, which suggests that Irma was a more difficult hurricane than usual to forecast at those longer time periods.

Among the individual models, the European Centre for Medium-Range Weather Forecasts model was the best-performing model and the only one to consistently beat the NHC official forecasts. The NOAA HFIP Corrected Consensus Approach model and the Florida State Superensemble also performed very well and had lower average errors than the official forecasts at most time periods. All of the models had a right-of-track bias and predicted Irma to turn northward sooner and farther east over Florida, but the bias was the smallest in the Euro and UKMET models, which handled the large-scale steering features better than the US GFS and Hurricane-WRF models.

Hurricane Irma's path