WEATHER

Hurricane Irma: Category 5 tied for second strongest Atlantic hurricane ever

BY John Cifelli, Meteorologist |

— 185 mph winds, 929 mb
— Hurricane warnings posted for Puerto Rico, Leeward Islands
— High likelihood of an East Coast landfall

Hurricane Irma was upgraded to a Category 5 hurricane by the National Hurricane Center this morning, as she buzzsaws into the central Caribbean Sea with maximum sustained winds of 185 mph.That makes her tied for the second strongest Atlantic hurricane ever, and the strongest since Gilbert, 29 years ago.The Leeward Islands and Puerto Rico are under Hurricane Warnings, and the Southern Bahamas, Dominican Republic, Haiti and Cuba will likely fall under the same later today. With winds this powerful, Irma is tied for the second strongest Atlantic hurricane ever, and the strongest since Gilbert, 29 years ago. Any increase in wind speed will vault Irma into the top four strongest storms in the Atlantic of all time. She is currently headed just north of west, and a gradual WNW track is expected over the next couple of days, before she makes a more dramatic turn north on Saturday. Absent of an unexpected turn north earlier than expected, it is going to be very difficult to avoid a United States landfall sometime this weekend or early next week. Assuming Irma does strike the United States as a Category 4 or 5 storm, it will be the first time we experience back to back landfalls of that intensity in over 100 years.

Irma will travel over the ocean and sea equivalent of bathwater over the next several days, and she is enjoying a low-shear environment. Although hurricanes typically do not maintain such extreme intensity, Irma’s strength is not likely to diminish too much — unless her path takes the storm over substantial portions of the islands in or near her path. Interaction with land interrupts the mechanisms that tropical storms and hurricanes rely on for development. With this in mind, contact with islands in the Caribbean would be to the benefit of those on the United States mainland.

As we near the end of the medium term forecast period (day five), Irma begins to turn north as she escapes the influence of a broad upper level ridge across the central and western Atlantic. Currently, and through the rest of the week, this ridge is pressing Irma south and west, pinning her down from the natural trajectory of hurricanes to curve north and then east out to sea. As Irma slides west away from the ridge, she will turn north towards an upper level trough across the Great Lakes and Mississippi Valley. When and how dramatically this turn north occurs will decide Irma’s final track towards the United States. Currently, model guidance suggests the turn occurs between Cuba and Florida, and Irma will landfall somewhere on the Florida Peninsula. However, as Irma’s track is dependent on the strength and placement of upper level features still 5 days away, it is simple to see how dramatically things can change between now and then.

The worst impact to New Jersey would come with an earlier turn. In that case, Irma may make landfall on Florida, and reemerge into the Atlantic near Jacksonville, sliding northeast towards a second landfall in the Carolinas. She may skirt the eastern coast of Florida, or miss the state entirely, making her first US landfall in the Carolinas before climbing the coast. In any of these scenarios, New Jersey could potentially deal with a Hurricane Floyd-like scenario, with a weak hurricane or strong tropical storm conditions, and double digit rainfall totals.

The best case scenario for our state would be for the Great Lakes trough to move east quicker and have little interaction with Irma. In that case, a ridge could build back overhead aloft across the mid-Atlantic, and have the same south/west affect on the storm that the Atlantic Ridge is currently having on her. In that case, Irma, and her remnants would drift into the Tennessee or Ohio Valley, and the system would unwind and dissipate with little, if any impact.

There is a good reason that the National Hurricane Center does not forecast beyond five days. Anything more would be speculative, and the decisions related to emergency management and evacuations that are made based on hurricane forecasts are immense. For the time being, it is safe to say that all possibilities from a post-landfall impact to no impact at all, are on the table. If New Jersey sees the impacts of Irma, it will be after this weekend has passed. It would be prudent to review your own emergency plan, and do a household preparedness audit. Regardless of Irma’s effect on New Jersey, it is always a matter of time until you will find yourself glad to be ready for an emergency scenario.