As Louisiana and the Northeast U.S. continue to pick up the pieces after Hurricane Ida’s destructive rampage (see below for tips on how you can help), two other tropical systems deserve attention this Labor Day weekend.

The strongest by far is Major Hurricane Larry, which vaulted to category 3 strength late Friday in the central tropical Atlantic. At 11 a.m. EDT Saturday, Larry was packing top sustained winds of 125 mph as it spun about half way between the Leeward Islands and the Cape Verde Islands, moving west-northwest at 15 mph.

The broad strokes of Larry’s forecast are unusually straightforward. As it’s steered around the Azores High, Larry is expected to carve out a classic path over the next few days, gradually curving to the west-northwest and northwest through the central Atlantic. This route will bring Larry closer to Bermuda by midweek, and the island is projected to be within the National Hurricane Center’s five-day cone by Thursday. The long-range GFS and European ensemble forecasts are in emphatic agreement on this overall track. A strong upper-level low is expected to be reinforced across New England and Maritime Canada next week, which should steer Larry safely out to sea. Update (2:30 p.m. EDT Sunday): The track forecast with Larry continues to be high-confidence, with only a small chance that Larry will pass far enough west to strike Bermuda.

The intensity forecast is also straightforward. Larry is predicted to remain a major hurricane over the five-day forecast period, a feat last accomplished by Hurricane Maria (2017). Larry could easily reach category 4 strength over the weekend, as predicted by NHC, with wind shear light (less than 10 knots) and sea surface temperatures (SSTs) above 27 degrees Celsius (81°F). Somewhat drier air will filter into Larry’s circulation early next week (mid-level relative humidity dropping from around 60% to around 50%), but SSTs will warm to around 29°C (84°F) and shear is expected to remain light to moderate. The main factor modulating Larry’s strength prior to approaching Bermuda will be hard-to-predict eyewall replacement cycles. Update (2:30 p.m. Sunday): Larry is now predicted by NHC to remain a category 3 hurricane through Wednesday, gradually weakening late in the week as it encounters cooler waters and stronger wind shear.

Larry’s large swells next week will bring high surf and the risk of rip currents to the U.S. East Coast, Canadian Maritime Provinces, and north-facing shores of the Caribbean islands. Dangerous surf from Larry’s large swells will begin to affect the Lesser Antilles on Sunday. For the East Coast, the NHC is already warning of “life-threatening surf and rip current conditions” after Labor Day.

Figure 1. Infrared satellite image of 91L near the east coast of Mexico’s Yucatan Peninsula at 1730Z (1:30 p.m. EDT) Saturday, September 4, 2021. (Image credit: RAMMB/CIRA/CSU)

Disturbance 91L headed for southwest Gulf this weekend

A diffuse disturbance dubbed 91L could approach the Gulf Coast later next week after taking a slow track across the western Gulf of Mexico. The disturbance will be moving across the southern Yucatan Peninsula of Mexico over the weekend. At midday Saturday, an elongated cluster of intense showers and thunderstorms was weakening off the Caribbean cost of Belize and Mexico.

Some redevelopment is possible Saturday night, but any consolidation most likely will wait until 91L moves into the Bay of Campeche on Sunday. It could then take several days for 91L to organize any further, as strong wind shear of 20-30 knots will prevail along its path in the western Gulf from Sunday through at least Tuesday. The disturbance will be passing over very warm water around 29 degrees C (84°F); together with a moist midlevel atmosphere (relative humidity 60-70%), 91L is likely to maintain at least some convection (showers and thunderstorms).

Longer-range models will struggle with projecting 91L’s future until there is a more well-defined center. For now, only a few members of the GFS and European model ensemble show development of 91L in the western Gulf. Whatever might emerge, if anything does, would most likely drift toward the Gulf Coast later next week. Persistent wind shear and dry air likely will inhibit any extensive development even then. However, as even a tropical depression can dump large amounts of rain if it is a slow mover, 91L needs to be monitored over the next few days. In its 2 p.m. EDT Saturday tropical weather outlook, NHC gave 91L a near-zero chance of development through Monday but a 30% chance for Monday through Thursday. Update (2:30 p.m. EDT Sunday): There has been little change in 91L’s status since Saturday. As of 2 p.m. Sunday, NHC now gives 91L a near-zero chance of development through Tuesday and a 30% chance for Tuesday through Friday. It looks increasingly likely that several inches of rain could fall in the upcoming week in association with 91L across northern Florida and the southern tier of Louisiana, Mississippi, Alabama, and Georgia. By late week, 91L may be emerging off the Southeast coast into the Atlantic.

Figure 2 (updated at 2:30 p.m. EDT Sunday, September 5). Output from the European model ensemble (EPS) from 0Z Sunday, September 5, shows a modest chance that 91L will become a tropical depression toward the middle of the week. (Image credit: weathermodels.com)

How to help hurricane recovery efforts

The Partnership for Inclusive Disaster Strategies (formerly portlight.org), co-founded by members of the Weather Underground community, is responding to the Hurricane Ida disaster. Also, the Weather Channel has put together a list of many excellent charities that will be active in Hurricane Ida recovery.

Dr. Jeff Masters contributed to this post.

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Bob Henson

Bob Henson is a meteorologist and journalist based in Boulder, Colorado. He has written on weather and climate for the National Center for Atmospheric Research, Weather Underground, and many freelance...