The "H-Bomb" Hurricane

Hurricane Irma is one of the most powerful Atlantic hurricanes ever: what we know

Irma is on track to hit the Eastern Caribbean and Puerto Rico Wednesday. Its path later in the week is still uncertain.

Updated by Sep 6, 2017, 6:32pm EDT

Hurricane Irma is already one for the record books.

As a Category 5 with sustained winds of 185 miles per hour, Irma now ranks among the most powerful hurricanes (as measured by wind speed) ever recorded. Irma has sustained these 185 mph winds for more than 24 hours, a record length of time. And it’s one of the most powerful cyclones to ever make landfall.

On Wednesday, the fierce storm hit the leeward (i.e. northeastern) Caribbean islands, moving through Barbuda and St. Martin. The New York Times reports widespread damage to property, homes, and infrastructure on these and other islands. Gaston Browne, the prime minister of Antigua and Barbuda told reporters Barbuda “is totally destroyed — 90 percent at least.” And there’s reports of at least one death on the island.

Later today, the eye of Irma will pass just north of Puerto Rico, where evacuations are underway and where there are fears the storm could disrupt the power supply for months. On Thursday, Irma is expected to graze by the Dominican Republic and Haiti. By late Thursday, it will be near Turks and Caicos and the southeastern Bahamas. All of these islands can expect tropical-storm force winds (at least), heavy rainfall, and coastal storm surge.

Even if these island do not receive a direct hit, it’s still a dangerous situation. “Hurricane-force winds extend outward up to 50 miles from the center and tropical-storm-force winds extend outward up to 185 miles,” the National Hurricane Center reports.

It’s still unclear if the storm will make landfall in Florida or elsewhere in the continental United States (it wouldn’t reach Florida until Saturday or Sunday). But it’s possible a huge “potentially catastrophic” category 4 or 5 storm will impact Florida. The forecast will grow more certain in the next few days. And local officials are already preparing for the worst. There are also chances of impacts in the Carolinas, depending on which direction the storm shifts in the coming days. Even the best forecasts are uncertain where Irma might land this weekend, meteorologist Eric Berger explains on Space City Weather.

According to the NWS, Irma is the strongest storm ever in the Atlantic (not counting those that reached the Caribbean and Gulf of Mexico). And it’s not far off from the all-time record hurricane wind speed of 190 mph.

While the exact forecast, size, and path of Irma will change, know this: Irma poses a threat to life and property from the Eastern Caribbean to the Gulf Coast. Here’s the situation.

It’s still unclear if Irma will hit the mainland United States. But the forecast is ominous.

The forecast track leaves a landfall in mainland Florida or the Florida Keys a possibility. Though much is still uncertain. “The threat of direct hurricane impacts in Florida over the weekend and early next week has increased,” the National Hurricane Center says. “Hurricane watches could be issued for portions of the Florida Keys and the Florida peninsula on Thursday.” It all depends whether the storm shifts further to the east or west.

In any case, the center stresses vigilance for those in the potential path of the storm, and to make sure safety, preparedness, and evacuation plans are known and in place.

Florida and Puerto Rico have already declared states of emergencies in preparation, freeing up resources for shelters, evacuations, and deploying National Guard members to help respond to the powerful storm. Mandatory evacuation orders are underway in the Florida Keys. Officials in Miami-Dade and Broward counties in Florida are preparing for or ordering evacuations.

“We can rebuild your home, but we cannot rebuild your life,” Florida Gov. Rick Scott said on CNN Wednesday. “Take what you need, but only what you need.”

Don’t just focus on wind speed. Even if Irma downgrades, it’s still a dangerous storm.

Irma is currently churning with sustained 185 mph winds, and is gusting even higher. But wind speed alone does not completely describe the risk of a hurricane. These storms are made dangerous by a mix of three factors: floods from storm surge, heavy rainfall, and damaging winds. A Category 5 storm hits intensely on all three. (The greatest threat to loss of life in most hurricanes is storm surge and coastal flooding — not wind.)

The incredibly intense winds of Category 5 storms can completely destroy homes, uproot trees, and knock out power utilities for months. The National Hurricane Center reports that “some fluctuations in intensity are likely during the next day or two, but Irma is forecast to remain a powerful Category 4 or 5 hurricane during the next couple of days.”

But don’t focus solely on the category number. The Saffir-Simpson scale is ranked purely on wind speed. As we saw with Hurricane Harvey, even a downgraded hurricane or tropical storm can cause massive destruction and chaos. Even if Irma downgrades, it’s still dangerous.

The National Center for Atmospheric Research has a hurricane severity scale that factors in wind speed, hurricane size, and forward speed (whether it stalls or not) to rate the potential destructiveness of a storm 1-to-10 scale. Irma now rates at a 5.3. On this scale, Hurricane Katrina would have scored a 6.6.

Zachary Crockett/Vox

Harvey dumped 50-plus inches of rain over parts of Houston and Louisiana, creating devastating floods (mostly because the storm stalled over the Gulf Coast after it made landfall). Irma, so far, is not expected to be such a devastating rain event. Currently isolated forecast totals top out at 15 inches.

The US is still reeling from the impacts of Hurricane Harvey. Parts of Houston are still under water, thousands are still living in shelters, and cleanup efforts have barely begun. Needless to say, another catastrophic storm in a two-week period would add salt to a wound and further strain the disaster relief resources of the federal government and groups like the Red Cross already stretched thin with the response to Harvey.

Even if this storm does not have major impacts to the mainland US, it is poised to unleash havoc on the countries in the Caribbean in its path. Recall in 2016, Hurricane Matthew killed more than 500 in Haiti while largely sparing the United States.

The beginning of September is peak hurricane season. Already, two other storms — Jose and Katia — have formed. Follow those storms here.

How to follow Hurricane Irma:

  • The National Hurricane Center has a page updating every few hours with the latest watches and warnings for Harvey. Check it out.
  • Follow the San Juan branch of the National Weather Service on Twitter. And the Miami and Florida Keys branches too.
  • Follow the Capital Weather Gang’s Twitter account. These folks tend to live-tweet storm updates.
  • Here’s a Twitter list of weather experts via meteorologist Eric Holthaus. These experts will give you up-to-the second forecasts and warnings.


thanks to: Vox

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