Tropical storm Isaias is expected to touch down in New York City on Tuesday in the late afternoon, with the strongest winds hitting the city since Hurricane Sandy. Forecasts predict wind gusts between 65 and 70 mph, making skyscrapers particularly vulnerable: At 100 stories, wind gusts could be elevated to 72 to 77 mph. This is due to the lack of friction and resistance at higher altitudes.
"The tallest buildings in NYC will see about 10% higher gusts above the 60th floor," says CNN Meteorologist Chad Myers. "This is due to the lack of friction compared to all of the buildings and trees at lower levels."
New York City, where I currently live, has been blessedly free from wind speeds of 69 degrees since Hurricane Sandy in 2012, when the winds knocked a crane off the top of a skyscraper.
"The wind and flooding impacts from Isaias will be similar to what the city has seen from some of the strongest coastal storms," says Ross Dickman, the Meteorologist-in-Charge of the NWS in New York City, "but we haven't seen one this strong in many years."
The change in altitude isn't the only threat that skyscrapers experience. There's a wind tunnel effect caused by the way that the skyscrapers change the direction of wind. The wind will pick up small objects, which can create damaging projectiles. City building codes generally take wind load into account. Building codes in Miami were revised after Hurricane Andrew in 1992 to require skyscrapers to withstand wind speeds of 175 mph.
New York City building code requires any building to be able to withstand wind pressure of 15 psf (pounds per square foot) at a minimum. Wind speeds from Isaias are only expected to yield 15.2 psf of pressure at a maximum.
"Some flat top buildings use tar and stones as the last layer of waterproofing," says Myers. "The smaller loose stones can also be blown off the building and into other highrises near them creating a glass-break risk or even a danger to pedestrians walking below."
Stay safe, fellow New Yorkers!