Around August 17, a disturbance began to consolidate in the tropical Atlantic several hundred miles east of the Lesser Antilles. It originated as part of a sprawling trough of low pressure which extended far to the east-northeast and spawned two other tropical cyclones, Emily and Gert. The system crossed into the Caribbean sea on August 19, bringing heavy rain to the Windward Islands as it passed over. The system was facing some wind shear but conditions were otherwise favorable. This led to the formation Tropical Storm Franklin on August 20.
Franklin struggled to maintain a well-defined center of circulation over the next few days, not an unusual battle for cyclones in the eastern Caribbean. It had plenty of warm water and atmospheric moisture to work with, but wind shear inhibited it from gaining much strength, and in fact the low-level center reformed in different locatinos a couple of times. The storm at first had moved west, but it turned sharply toward the north by the 22nd under the influence of a trough over the western Atlantic. This ultimately brought the center over the Dominican Republic during the morning of August 23. The main impacts to Hispaniola were heavy rain. Franklin emerged over the open Atlantic late that afternoon.
The atmospheric steering currents collapsed the next day and the system slowed down and began an unusual turn to the east. Persistent wind shear out of the northwest also kept deep convection primarily to the southeast of the center. This prevented Franklin from strengthening much through August 25. That morning, the storm turned southeastward under the influence of an upper-level anticyclone in the Caribbean. It is very rare for a storm to move on a southeast heading in the tropics, especially before the very end of hurricane season.
Franklin's environment soon changed rather significantly, though. An upper-level low cut off to its west and it turned rather sharply back toward the northwest over the next day under the influence of this low. At the same time, wind shear lessened considerably, allowing the cyclone to become more symmetric and strengthen. Moderately dry air near the storm kept the thunderstorm activity limited, but this wasn't enough to prevent significant deepening on August 26 as hints of an eye appeared on satellite imagery. Franklin intensified into a category 1 hurricane that morning.
Spiral banding in the storm improved throughout the day as it continued slowly northwestward. It reached category 2 on August 27 and turned toward the north. However, it was the next day that Franklin really broke through, clearing out a large and circular eye. In a significant burst of strengthening, it became the first major hurricane of the season early in the morning of the 28th and then a category 4 shortly after. Franklin reached its peak intensity that evening with 150 mph winds and a central pressure of 926 mb. This pressure reading was the lowest yet recorded in an Atlantic hurricane over the open Atlantic (not the Gulf of Mexico) so far north, at 29 ° N. It was the lowest pressure in any Atlantic hurricane overall in nearly 3 years, since Iota of 2020.
On August 29, the satellite presentation degraded somewhat as the storm experienced an eyewall replacement cycle. Franklin weakened to a category 3. For a time, the storm cleared out a large new eye, but wind shear began to increase out of the north the next day, due to a combination of a large trough moving off the U.S. northeast and trailing Idalia in its wake. The storm was still a category 2 when it passed north of Bermuda; its wind field was large enough to bring tropical storm force winds to the island.
Franklin weakened to a category 1 on the 31st and also began extratropical transition as it sped toward the northeast. This transition completed on September 1, at which time the storm became a hurricane-force extratropical low. This low absorbed the much smaller Tropical Storm Jose late that night. The system ultimately moved eastward across the northern Atlantic and combined with another low pressure system off the coast of Europe.
The image above shows Franklin shortly before reaching peak intensity on August 28.
Franklin's unusual track was difficult to forecast due to a complicated combination of steering influences.
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