Powerful Hurricane Irma haunts the open Atlantic as forecasters try to discern its path
Hurricane Irma is only about 24 hours old, but it's already proving to be an unusual and worrying storm.
Having rapidly intensified from a tropical storm early Thursday into a Category 3 "major" hurricane about 12 hours later, Irma continues to move westward over the open ocean between the Leeward Islands and Africa. It is now just one of a few hurricanes in modern history to intensify so quickly that far east in the Atlantic.
Computer models are insistent that the storm will remain a force to be reckoned with during its long journey westward, as it follows steering currents around a sprawling area of high pressure parked over the northwest Atlantic.
Forecasters are trying to figure out where the storm is headed. Will it impact the U.S., which is still reeling from Hurricane Harvey's devastation in Texas and Louisiana? Or will it recurve harmlessly out to sea?
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That question won't be answered today, but computer model simulations show two main factors that will determine Irma's eventual path: the high pressure area and a dip, or trough, in the jet stream that will dig into the eastern U.S. in about a week.
If the mid-level high pressure area wins out, the storm may be propelled into the Bahamas and the Southeast U.S., due to the clockwise flow of air around that high. If the trough is strong enough, southwesterly winds out ahead of it could pick up Irma and shove it away from the East Coast.
Interestingly, the placement of the trough in particular will be partially determined by another tropical cyclone -- Typhoon Sanvu -- located thousands of miles away in the North Pacific, off the coast of Japan.
Studies have shown that when powerful typhoons recurve away from Japan, as Typhoon Sanvu is forecast to do, they can energize the highway of swiftly flowing winds at high altitudes, popularly known as the jet stream, and lead to a more active weather pattern across North America.
For the jet stream, the storms can function as an injection of steroids, causing it to amplify and contort itself into large north-south undulations. These waves, known to meteorologists as ridges and troughs, get carried downstream like ripples in a pond, affecting weather in Alaska and the continental U.S.
Regardless of its path, it's clear that the storm will be intense, potentially peaking as a Category 4 or 5. One of the more reliable hurricane intensity models shows Irma remaining a major hurricane during the next 5 to 7 days.
Computer model runs on Thursday appeared to be more ominous, favoring direct impacts in the U.S. In particular, the more reliable European model showed this scenario.
On Friday, however, more model runs are showing an offshore track. That said, there is still more than enough uncertainty to keep a U.S. strike within the realm of possibility. It will be at least a few more days before this storm's ultimate path is known with much confidence.
Anyone with interests along the East Coast of the U.S., as well as Puerto Rico and the Bahamas, should review their hurricane plans and make sure to pay close attention to forecasts during Labor Day weekend.
We're getting near the peak of hurricane season, so such steps are prudent regardless of Irma's ultimate path.
Andrew Freedman is Mashable's Senior Editor for Science and Special Projects. Prior to working at Mashable, Freedman was a Senior Science writer for Climate Central. He has also worked as a reporter for Congressional Quarterly and Greenwire/E&E Daily. His writing has also appeared in the Washington Post, online at The Weather Channel, and washingtonpost.com, where he wrote a weekly climate science column for the "Capital Weather Gang" blog. He has provided commentary on climate science and policy for Sky News, CBC Radio, NPR, Al Jazeera, Sirius XM Radio, PBS NewsHour, and other national and international outlets. He holds a Masters in Climate and Society from Columbia University, and a Masters in Law and Diplomacy from The Fletcher School at Tufts University.
