12 September, 2017
City officials last week said that the cranes could not be tied down or moved.
In its 10 p.m. update, the National Hurricane Center said Irma is taking its time moving away from Cuba, moving slowly northwestward away from its north coast at almost 6 miles per hour.
Tower cranes can rise hundreds of feet into the air on steel frameworks, and are used to lift steel, concrete, heavy construction equipment and other building materials.
Those counterweights could pose a grave threat if any of the cranes are unable to withstand wind and flying debris.
Residents at the Treasure Village Mobile Home Park in St. Petersburg, about four hours northwest of Miami Beach, said they weren't leaving either - even though the county called for an evacuation of all mobile homes, regardless of whether they were inland or near the water.
A crane tower is seen after part of it collapsed from the winds of Hurricane Irma on September 10, 2017 in Miami, Florida.
A collapsed construction crane seen in downtown Miami
When considering the risks of high-speed winds, it's important to remember that their power and potential for damage grow exponentially.
No injuries were reported after either crash, said Miami City Manager Daniel Alfonso.
Reporting on the dangers posed by Irma's powerful winds when they reach Florida, NPR's David Schaper spoke to Northwestern University civil engineering professor Joseph Schofer. The bayfront area is filled with hotels and high-rise condo and office buildings, near AmericanAirlines Arena.
The first collapse occurred Saturday morning at the under-construction building at 300 Biscayne Blvd.
"Streets have to be closed, another crane has to be brought in", he said.
"Our cranes are still weather vane-ing", Whiteman said.
A tornado could have ripped the crane loose, Whiteman said.More news: Price of gas jumps again as long weekend approaches