Hurricane Lee placed on a rare feat of fast intensification within the 24 hours ending at 2 a.m. EDT Friday, growing its winds by 85 mph because it moved over the record-warm waters northeast of the Leeward Islands. Only two different Atlantic hurricanes up to now 40 years — Felix (2007) and Wilma (2005) — intensified extra quickly. Lee peaked as a particularly harmful Category 5 hurricane with 165 mph winds early Friday, then weakened barely to a high-end Category 4 hurricane late Friday morning.
Research by Kieran Bhatia (see beneath) and others has recognized fast intensification as one of many hurricane phenomena being boosted by oceanic warming from human-induced local weather change.
At 11 a.m. EDT Friday, Lee was situated about 565 miles east of the northern Leeward Islands, shifting west-northwest at 13 mph with prime sustained winds of 155 mph and a central stress of 942 mb. Satellite images early Friday afternoon confirmed that Lee’s eyewall thunderstorms weren’t as intense or as symmetric as earlier than, with a area of lowered depth alongside its west facet. This was being brought on by some average southwesterly wind shear of 15-20 knots — which was not predicted — that started affecting Lee early Friday morning.
Three hours of GOES-East 1-minute imagery centered over Hurricane Lee this morning. Shown is storm-relative animation of seen imagery.
Both GOES-East Meso-sectors again to protecting SPC Slight Risk areas for remainder of in the present day. pic.twitter.com/dswSFMxQ7m
— Bill Line (@bill_line) September 8, 2023
Track forecast for Lee
Lee is anticipated to maneuver west-northwest at a progressively slowing ahead pace by Tuesday, pushed by the clockwise circulation across the Azores-Bermuda High to the north. On this observe, the system will cross just a few hundred miles to the northeast of the northernmost Leeward Islands on Saturday and Sunday, sparing them any main impacts from wind and rain. The National Hurricane Center, or NHC, predicts a few 10-20% probability of tropical storm-force winds in these islands.
On Wednesday, Lee is anticipated to succeed in the western fringe of the high-pressure ridge steering it and begin to really feel the steering affect of a trough of low stress shifting over the U.S. East Coast. This trough is more likely to flip Lee sharply to the north, protecting the core of Lee away from the southeastern Bahamas and Turks and Caicos Islands, sparing them from any main impacts from wind and rain. NHC predicts a few 10-20% probability of tropical storm-force winds in these islands.
The actual location and timing of Lee’s sharp northward flip — which remains to be on the fringe of NHC’s five-day forecast window — will strongly decide Lee’s subsequent future. Lee is anticipated to make its closest method to Bermuda round Sept. 14-15. However, long-range forecast ability up to now sooner or later is poor, and the risk to Bermuda is unclear. After Lee passes Bermuda, the hurricane poses a landfall risk to the Canadian Maritime Provinces and the Northeast U.S.; the Friday morning runs of the GFS and European fashions and their ensembles have been exhibiting {that a} landfall as far west as Massachusetts or as far east as Newfoundland have been prospects; a landfall farther to the south alongside the U.S. East Coast was wanting much less and fewer seemingly. A recurvature out to sea with out making landfall can also be a very good chance.
The steering of Lee late subsequent week will likely be decided by the trough of low stress to the storm’s west, over japanese North America, mixed with a ridge of excessive stress to Lee’s east, centered alongside the east coast of Newfoundland. If this ridge is robust sufficient, it would block Lee’s path to the east, ensuing within the hurricane making landfall within the Canadian Maritime Provinces or New England. A weaker ridge would permit Lee to recurve out to sea with out making landfall.
The energy of this ridge might rely critically upon how shut Tropical Storm Margot will get and the way robust it’s. If Margot is robust sufficient and shut sufficient to Lee, Margot will weaken the ridge and have interaction in a Fujiwhara interplay with Lee — a scenario the place two cyclones rotate counterclockwise round a typical heart. This resolution was marketed by the 0Z Friday operational run of the European mannequin. A extra seemingly scenario is that Margot stays far sufficient away from Lee that no interplay between the storms happens, leading to Lee’s landfall in Canada, as predicted by the Friday morning runs of the GFS mannequin and by many of the ensemble members of each the GFS and European mannequin (Figure 2). In brief, this stays a high-uncertainty forecast!
One influence is assured, although: Lee will carry a chronic interval of excessive surf and harmful rip currents to the northern shores of the islands of the northeastern Caribbean starting this weekend and to a lot of the east coast of North America starting early subsequent week. High surf will begin to have an effect on the Canadian Maritime Provinces by Wednesday.
Intensity forecast for Lee
The wind shear affecting Lee on Friday is anticipated to abate by Saturday or Sunday, permitting Lee to benefit from in any other case favorable circumstances for intensification: heat waters of 30 levels Celsius (86°F) and a fairly moist ambiance (a midlevel relative humidity of 55-60%). The whole warmth content material of the ocean waters is anticipated to peak on Sunday. These circumstances ought to permit Lee to stay at Category 4 or 5 energy by the weekend. The 12Z Friday run of the SHIPS model predicted that over the following 4 days, Lee’s most potential depth — the strongest it might probably get beneath excellent circumstances — could be a Category 5 hurricane with 190-195 mph winds. The 11 a.m. EDT Friday NHC depth forecast referred to as for Lee to take care of Category 4 energy for the following 5 days and never attain Category 5 energy once more, however NHC additionally acknowledged in its forecast dialogue that restrengthening was potential; one other interval at Category 5 energy can’t but be dominated out.
Lee may additionally bear an eyewall alternative cycle this weekend. This course of, widespread in intense hurricanes, happens when the eyewall shrinks, grows unstable, and collapses, and a brand new outer eyewall with a bigger diameter replaces it. An eyewall alternative cycle usually weakens the utmost winds of a hurricane by 10-20 mph however spreads out hurricane-force winds over a bigger space, growing the storm surge. The timing of eyewall alternative cycles is tough to foretell.
Most of the depth fashions agree that Lee will likely be a robust Category 4 or 5 hurricane by Tuesday, then weaken to Category 3 energy by Wednesday due to lowered ocean heat and a rise in wind shear. Lee’s depth on the time of any potential landfall within the U.S. or Canada that happens late subsequent week is unattainable to foretell up to now upfront, however Lee is predicted to broaden considerably in dimension and could be able to inflicting vital impacts from its storm surge, winds, and heavy rains, even when it have been a tropical storm.
Seven Cat 5s globally in 2023
Lee is Earth’s seventh Cat 5 storm of 2023, utilizing rankings from the Joint Typhoon Warning Center and National Hurricane Center. The 1990-2022 common globally for a complete calendar 12 months is 5.3 Cat 5s, so we’re already above common. With the Northern Hemisphere season solely about half full, it’s seemingly there will likely be extra Cat 5s, significantly within the northwest Pacific. The file is 12 Cat 5s in a 12 months, set in 1997. Last 12 months had solely three.
This 12 months is now the primary time on file that there was at the very least one Cat 5 noticed in each main ocean basin vulnerable to tropical cyclones. In addition to Lee within the Atlantic, we had Cat 5s within the northeast Pacific (Jova), northwest Pacific (Super Typhoon Mawar), North Indian (Cyclone Mocha), the South Indian (Cyclone Freddy and Cyclone Ilsa), and Southwest Pacific (Cyclone Kevin). Thanks go to Jasper Deng for this stat.
Tropical Storm Margot on observe to accentuate this weekend
Though nonetheless a minimal tropical storm on Friday, Margot could also be prowling the Atlantic for an extended whereas — even perhaps longer than Lee. At 11 a.m. EDT Friday, Margot was centered within the japanese tropical Atlantic about 600 miles west-northwest of Cabo Verde, with prime sustained winds of 40 mph and a central stress of 1005 mb, headed west-northwest at 17 mph.
The expansive area of showers and thunderstorms, or convection, round Margot was not particularly nicely organized at noon Friday. Margot will likely be shifting west-northwest this weekend over heat waters (round 28 levels Celsius, or 82 levels Fahrenheit), inside a modestly moist ambiance (midlevel relative humidity round 55-60%). Margot’s important nemesis will likely be persistent westerly wind shear of 15-25 knots, which was pushing most of Margot’s convection away from its low-level heart on Friday — by no means a very good signal for the well being of a tropical cyclone. Despite the robust shear, forecast fashions are in robust settlement that Margot will progressively intensify over the following a number of days. The National Hurricane Center predicted on Friday that Margot will attain hurricane energy by Sunday and stay a Category 1 storm by at the very least Wednesday.
Margot itself is not going to threaten any land areas for the following few days, if ever, and it’ll most certainly stay far sufficient east of Lee (at the very least 1,000 miles or 1,600 kilometers) to attenuate any affect on their mutual movement that might come up from the Fujiwhara effect, as mentioned above. Even so, Margot might nonetheless affect the destiny of Lee. As Margot angles towards the north early subsequent week, it would assist break down the sprawling Bermuda High now steering Lee towards the west-northwest. The evolution of that prime will play an important position in Lee’s future, as famous above.
Next tropical wave
Quite a lot of members of the GFS and European mannequin ensembles are exhibiting growth might happen by the center of subsequent week within the central tropical Atlantic of a tropical wave predicted to maneuver off the coast of Africa early subsequent week. This wave is just not but being highlighted by NHC in its Tropical Weather Outlook.
Website guests can touch upon “Eye on the Storm” posts (see feedback coverage beneath). Sign as much as obtain notices of latest postings here.
