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Thursday, July 1, 2021

Hurricane Elsa (2021)

Storm Active: June 30-July 9

On June 27, a vigorous tropical wave left the African coastline. It stuck to the low-latitudes away from any Saharan dry air and quickly moved westward. By the 29th, it had developed a broad low pressure center and was showing signs of organization. Things really ramped up the next day when spiral banding features became evident, though satellite data indicated that there was still only a sharp trough at surface level (winds flowed around a line oriented north to south, rather than around a center of circulation). Moist equatorial inflow from the southwest generated some more spin and helped the system reach tropical depression status that night.

By the morning of July 1, the cyclone was producing gale force winds and was upgraded to Tropical Storm Elsa. Remarkably, Elsa broke the record for earliest fifth named storm (or "E" storm) that had been set just one year previously by 2020's Tropical Storm Edouard on July 6 of that year. It was still early in the summer and the tropical trade winds that blow east to west were very strong: Elsa reached a remarkable forward speed of 29 mph toward the west-northwest that afternoon. Such forward speeds are rare in the tropics, as opposed to the mid-latitudes where they are more common. Typically, this speed would make it hard for thunderstorm activity to "keep up" with the system's center, but otherwise favorable conditions allowed Elsa to intensify (albeit gradually) throughout the day.

Overnight, a circular central dense overcast blossomed and the storm's core became much better defined. This allowed a faster burst of strengthening that continued into July 2 and brought Elsa to hurricane strength that morning. The center passed just south of the island of Barbados and crossed the Windwards into the Caribbean sea later that morning. Elsa became a hurricane farther east in the tropics than any other recorded storm so early in the calendar year since 1933. It also was the fastest moving hurricane ever recorded in the tropics, at one point reaching 31 mph. However, after reaching a peak intensity of 85 mph winds and a pressure of 991 mb that afternoon, the storm's rapid forward speed finally caught up with it: the center of circulation outrun the associated thunderstorm activity and convection collapsed.

As a result, some weakening occurred overnight and into the morning of July 3, putting Elsa at high-end tropical storm strength. It passed well south of Puerto Rico and the Dominican Republic, and paralleled the southern coast of Haiti that afternoon. Though it stayed offshore, torrential rainfall impacted the southeastern peninsula. The cyclone approached the western edge of the steering ridge that evening and finally slowed down, allowing new deep convection to develop over the center of circulation. And yet, Elsa continued to baffle: even as the satellite presentation improved, aircraft reconnaissance indicated that central pressure continued to increase, rising to 1009 mb on July 4. Such a pressure is more typical of a tropical depression than a strong tropical storm!

Regardless, more rain was in store as the storm passed just north of Jamaica that day. Elsa then slowed even more and turned northwest toward central Cuba. The system remained fairly disorganized but held nearly steady in intensity up to landfall in Cuba on July 5. Fortunately, impacts in the country were not that severe. That evening, the center emerged into the Gulf of Mexico. Being back over water allowed the cyclone to again build a core, but it was slow going; wind shear out of the southwest kept the low-level circulation exposed and the thunderstorm activity primarily to the northeast. Nevertheless, slow strengthening occurred as Elsa moved north toward Florida on the 6th.

Satellite imagery during that afternoon indicated that the shear vector was now from the south - a bit more favorable for intensification as the center was moving northward. Hints of an eye appeared on radar and Elsa regained hurricane strength that evening. By that time, the outer bands were affecting western Florida, but the compact core meant that most impacts stayed offshore. Overnight, dry air invaded the core and the system weakened again to a tropical storm. It still had maximum sustained winds of 65 mph, however, when it made landfall in northwestern Florida late in the morning of July 7.

Elsa brought moderate flooding to the southeast as it began to curve northeastward, passing inland into Georgia. At first, it weakened over land, but it maintained an impressive circulation. It remained a tropical storm and even restrengthened some as it passed over the Carolinas on July 8. By the evening, flooding rains had spread northward into the mid-Atlantic states. The cyclone's center exited the coast briefly overnight before making further landfalls in New England during the morning of July 9. By that time, it was losing tropical characteristics as it continued to accelerate northeastward. At last, Elsa completed its long journey and became post-tropical that afternoon. Its remnants passed through Atlantic Canada and ultimately dissipated over the north Atlantic.



The above image shows Elsa near peak intensity passing over the Windward Islands.



Elsa had impacts all the way across the Caribbean and all the way up the eastern coastline of North America.

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