Impressive Hurricane Larry continues to maintain major hurricane status as it trundles northwest at 10 mph over the open central Atlantic. At 11 a.m. EDT Monday, Larry had top sustained winds of 120 mph, and had been a major category 3 hurricane since 3Z Saturday (11 p.m. EDT Friday). 

Satellite images showed that Larry had a huge 70-mile diameter eye, a thick eyewall, and virtually no outer spiral bands. These qualities are characteristic of a special type of hurricane referred to as “annular.” Such hurricanes tend to form when the surrounding atmosphere is dry, making it difficult for the storm to maintain far-flung spiral bands.

Larry will be in a supportive environment for a major hurricane over the next three days, and the National Hurricane Center (NHC) is predicting Larry will be a major hurricane through Wednesday night as it makes its closest approach to Bermuda. Larry is expected to pass just east of the island on Thursday morning, close enough to bring it heavy rain showers and strong winds. In its 11 a.m. EDT Monday wind probability forecast, NHC gave Bermuda a 39% chance of experiencing tropical storm-force winds of 39 mph or more from Larry, and a 7% chance of hurricane-force winds.

Larry’s large size and long duration at category 3 strength are making the hurricane a formidable wave machine, and the Lesser Antilles Islands were experiencing its resulting large waves and dangerous rip currents on Monday. These conditions will spread westward and northward during the week, and affect much of the U.S. East Coast and Canadian Maritime Provinces by Wednesday.

Larry will be steered to the northwest by the Azores-Bermuda High through Tuesday, but it is predicted to turn to the north and northeast later in the week, when the hurricane will feel the pull of a trough of low pressure passing to the north. Larry is expected to pass near southeastern Newfoundland, Canada, on Friday night, September 10. In its 11 a.m. EDT Monday wind probability forecast, NHC gave Cape Race, Newfoundland, a 56% chance of experiencing tropical storm-force winds of 39 mph or more from Larry, and a 13% chance of hurricane-force winds.

Moisture pulled to the northwest by Larry is expected to affect New England late this week, potentially bringing 1-3” of rain to the coast (see Tweet by Michael Ventrice below).

Disturbance 91L likely to bring rains of 1-3” to the Southeast U.S.

In the south-central Gulf of Mexico, an area of disturbed weather designated 91L was moving northward at less than 5 mph, bringing a few heavy rain showers to the Yucatan Peninsula and adjacent waters, as seen on satellite imagery. Though waters are warm and the atmosphere moist, 91L is experiencing high wind shear of 20-30 knots from an upper-level trough of low pressure, and is unlikely to develop over the next two days.

Figure 1. Output from the European model ensemble (EPS) from 0Z Monday, September 5, shows about a 40% chance that 91L will become a tropical depression in the northeastern Gulf of Mexico or waters off the Southeast U.S. coast by Thursday night. (Image credit: weathermodels.com)

High wind shear is predicted to continue for the remainder of the week over the Gulf of Mexico, and steering currents will carry 91L to the north or northeast at less than 5 mph. Heavy rains of 1-3” from 91L may affect the U.S. Gulf Coast from Louisiana to the Florida Peninsula Wednesday through Friday. On Friday, 91L will likely cross over northern Florida, emerging into the Atlantic Ocean off the Southeast U.S. coast by Saturday. Wind shear may be lower at that time, and 91L’s best odds of development will come this weekend when it is off the coast of South Carolina, as it moves to the northeast, parallel to the coast. In its 8 a.m. EDT Monday Tropical Weather Outlook, the NHC gave the system 2-day and 5-day odds of development of 0% and 30%, respectively. The next name on the Atlantic list of storms is Mindy.

The southwestern Gulf of Mexico’s Bay of Campeche will be another area for possible tropical cyclone formation this weekend, when a tropical wave may enter the Gulf and begin to develop, according to the 12Z Monday run of the GFS model.

Bob Henson contributed to this post.

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Jeff Masters

Jeff Masters, Ph.D., worked as a hurricane scientist with the NOAA Hurricane Hunters from 1986-1990. After a near-fatal flight into category 5 Hurricane Hugo, he left the Hurricane Hunters to pursue a...