What Irma’s wind and water did to Florida

After days of terrifying predictions, Irma arrived slammed into the Florida Keys on Sunday morning and the Florida mainland Sunday afternoon. It entered the state as a Category 4 hurricane and left as a still-powerful tropical storm.

Irma had weakened Monday but continued to have remarkable reach, with high winds reaching more than 400 miles from the center.

While the northern part of the state is still experiencing the wind, rain and storm surge, the southern part has begun to assess the storm’s damage.

Irma brought substantial winds across Florida and into Georgia and parts of Alabama and South Carolina, with some areas reporting gusts at nearly 90 miles per hour.

The National Weather Service uses an array of instruments, also known as the Automated Surface Observing System, to measure climate conditions, especially during a hurricane.

But with enough force, those instruments can fail.

In Key West, the city’s monitoring system at the Key West International Airport reported an outage shortly before Irma made landfall at about 9 a.m. Sunday, said Susan Buchanan, director of public affairs for the National Weather Service, in an email.

The airport’s last wind reading before failing: 75 mph gusts.

Buchanan said the weather service also received word about a system outage at Ft. Lauderdale International Airport, which recorded 45 mph gusts before it failed.

As Irma moved north, so did power outages. By Monday morning, more than 6 million households in Florida had lost power. As restoration began in some place, others, such as areas of Georgia, went dark.

Storm surge and its impact

As Irma approached, the low pressure of the storm system and force of the winds pulled water away from shorelines.

Next came a large storm surge that pushed even more water back in, causing tides to rise several feet above normal as the storm made landfall.

The disappearing waters were a surprising sight to many. In some locations residents ventured out on shoreline that is normally covered by 4 to 5 feet of water. In Manatee County the receding waters stranded two manatees.

The National Hurricane Center posted a storm surge warning from Florida up to South Carolina, estimating that water levels rise more than 15 feet in some areas.

Tornado watches and warnings also blanketed Florida as Irma’s wind bands spawned other storms.

The surge was particularly threatening to vulnerable, low-lying cities such as Tampa, and the area seemed ill-prepared for it. A World Bank study called Tampa Bay one of the 10 areas in the world most at risk of damaging and costly flooding.

Evacuations ordered

As the storm approached, more than 6 million people in Florida were ordered to evacuate.

In Miami-Dade County, authorities issued the county’s first major, mandatory evacuation in more than a decade. Georgia Gov. Nathan Deal also issued mandatory evacuations in the state’s coastal counties, including the areas east of Interstate 95.

Additional low-lying areas and those in mobile homes may also be or have been under mandatory evacuation orders. As of Sunday, more than 114,000 people filled more than 500 shelters in Florida.