Tropical Storm Rina (2023)

Storm Active: September 28-October 1

On September 23, a fairly late season tropical wave entered the Atlantic. It moved westward at a low latitude, passing well south of Cabo Verde and crossing the tropical Atlantic at a steady pace. By the 26th, an area of low pressure had developed along the wave, but the last push to tropical storm status was slow-going due to the size of the disturbance and the fact that Tropical Storm Philippe was close by to the northwest. Around the same time, the system turned rather sharply toward the north-northwest as it began a binary interaction with Philippe. A closed circulation became evident on September 28 and the disturbance was named Tropical Storm Rina.

The storm was over warm water but faced strong westerly wind shear and some disruption from the interaction with Philippe, which was only a little over 500 miles away to the west. Therefore, convection was confined primarily to the south and east of Rina's center. Due to the Fujiwhara effect, Philippe and Rina began to orbit each other cyclonically, which meant that Rina picked up speed and turned toward the west-northwest over the next couple of days. On September 30, the storm turned poleward and separated from the binary interaction, weakening as it did so. The strong shear over Rina did not lessen, and the center lost definition on October 1. By late that evening, it had degenerated into a remnant low. What was left of Rina dissipated soon after.

The image above shows Tropical Storm Rina early on September 29. The eastern part of Tropical Storm Philippe is visible at left.

Rina was a short-lived tropical storm that did not affect land.

Tropical Storm Philippe (2023)

Storm Active: September 23-October 6

Around September 19, another tropical wave entered the Atlantic. It moved west-northwest for the next few days and displayed some impressive thunderstorm activity, though it lacked a well-defined center. The system acquired enough organized to be classified Tropical Depression Seventeen on September 23, when it was roughly halfway between the African coastline and the Lesser Antilles. At the time of formation, the low-level center was rather west of the deepest convection, having outrun the rest of the system. Most of the mid-level spin was similarly displaced east of the center.

Despite battling wind shear, the system's satellite presentation improved steadily and it strengthened into Tropical Storm Philippe shortly after formation, with gradual intensification occurring thereafter. The center of the storm reformed northeast of its previous position on September 24, bringing the low-level circulation closer to the convective canopy. Over the next few days, wind shear increased some more, exposing the center again and slightly weakening Philippe. Sporadic bursts of thunderstorm activity continued to generate gale-force winds well east or southeast of the center, but the cyclone was very poorly organized as it continued generally westward. It turned northwest on September 27, but this motion was short-lived. In fact, Philippe was barely a tropical storm by the 28th: there appeared to be multiple centers of vorticity stretching east to west and the overall circulation was highly elongated.

Complicating the storm's situation further was newly formed Tropical Storm Rina to the east. The two storms influenced each other and began to orbit cyclonically around a common center due to the Fujiwhara effect. On Philippe's part, it slowed dramatically and took an unusual dip toward the southwest beginning late on the 28th and continuing through September 30. During that time, the center again became better defined and the storm deepened a little as a more solid central dense overcast became established.

The influence of Rina waned on October 1 as the distance between the cyclones increased. A mid-level ridge northeast of the storm became the dominant steering feature of Philippe's relatively shallow vortex, and it moved generally west-northwestward the next couple of days. The convection had become more vigorous, but was still displaced south and east of the center by shear for the most part. During the evening of October 2, the center of the storm made landfall in the island of Barbuda. Due to Philippe's structure, however, heavy rains spread into most of the Leeward Islands in the wake of the center's passing.

For the next day, the storm's center continued northwestward, passing north of the remaining Caribbean islands in its path, but the main area of convection moved almost due west into the northeastern Caribbean. This meant that heavy rainfall continued on the islands, but the cyclone itself lost organization as the separation between center and thunderstorm activity became greater and greater. By that night, the circulation was so ill-defined that Philippe was barely a tropical storm. New convection ultimately developed somewhat nearer the shallow vortex as the system turned north. Some of the activity was the result of the interaction of Philippe with a frontal boundary well north of the center, though. Regardless of its origin, this part of the storm swept over Bermuda by October 5 and brought tropical storm conditions there.

The next morning, Philippe's center was absorbed into the larger frontal system and it became post-tropical. The remnant low interacted with another non-tropical low to its west and the combined system ultimately deepened and swept into the upper northeast U.S. and Atlantic Canada by October 8.

The image above shows Philippe on September 27. The center is nearly exposed at the cloud cover's western edge. The storm struggled with wind shear nearly all of its existence.

Philippe was a meandering, long-lived, and hard-to-predict tropical storm. It has the strange distinction of being the first known Atlantic tropical cyclone to last as long as it did (13 days) without achieving maximum winds of more than 50 mph.

Tropical Storm Ophelia (2023)

Storm Active: September 22-23

Around September 18, a frontal boundary moved off the U.S. east coast over the Atlantic ocean. The southern end of the front stalled not too far from shore. A non-tropical low formed along that southern edge, just north of the Bahamas, on September 21. The low moved generally north or north-northwest and deepened rather quickly over the next day. During the afternoon of September 22, an area of deep convection developed on the western side of the storm, spiraling north and east away from the center. Though the system was asymmetric, satellite and aircraft reconaissance measurements indicated it had transitioned to a tropical storm. Therefore, it was named Tropical Storm Ophelia.

Ophelia was in an environment of rather strong shear and suffered from the aforementioned asymmetry. Despite this, it managed to strengthen some more as it approached land. The cyclone made landfall in North Carolina early on September 23 at its peak intensity of 70 mph winds and a pressure of 981 mb. The large system slowly pushed inland that day and gradually weakened, but brought a large area of storm surge, heavy rain, and tropical storm force winds to the mid-Atlantic. It weakened to a tropical depression that evening and became post-tropical shortly thereafter while located over southeastern Virginia. What was left of Ophelia turned north and then east, bringing more steady rain to the northeast as it weakened.

The above image shows Ophelia a few hours after becoming a tropical storm on September 22.

At the time Ophelia made landfall in North Carolina, the large storm's impacts were already being felt over an area that extended much further north.

Hurricane Nigel (2023)

Storm Active: September 15-21

Around a week into September, another tropical wave entered the Atlantic. Several days later, it merged with another tropical disturbance to its east. This consolidation took some time, but gradual organization continued and ultimately culminated in the formation of Tropical Depression Fifteen on September 15. The circulation remained rather broad, but conditions were favorable for intensification. The depression strengthened into Tropical Storm Nigel late on the 16th. The storm moved steadily on a northwest path across the central Atlantic under the influence of a subtropical ridge.

Early on September 18, Nigel became a hurricane. The structure underwent an interesting evolution over the next day, with a very large eye opening up by the 19th. Initially, though, the convection around the eye was quite thin, especially on the north side. The eyewall became more solid throughout the day and Nigel intensified further to a category 2 hurricane. That night, the cyclone reached its peak intensity of 100 mph maximum sustained winds and a minimum pressure of 971 mb. Around the same time, it turned north, rounding the edge of the subtropical ridge.

On September 20, Nigel began to accelerate northeast as it was swept up by the mid-latitude westerlies. This soon brought the hurricane to cooler waters and a higher shear environment, causing it to gradually weaken. The remaining deep convection was displaced from the center the following day and the system transitioned to post-tropical in the evening.

The image above shows Nigel near peak intensity on September 19. Its eye was unusually large relative to the storm's total size, a feature more common in hurricanes in the subtropics.

Nigel did not directly affect any land areas as a tropical cyclone.

Hurricane Margot (2023)

Storm Active: September 7-17

On September 5, another tropical wave entered the eastern Atlantic. It moved west-northwest and developed fairly quickly as it passed over Cabo Verde. In fact, it was still bringing rain to the westernmost islands of Cabo Verde when it was classified Tropical Depression Fourteen during the morning of September 7. Not long after that, it was upgraded to Tropical Storm Margot.

Margot faced a mixed-bag of conditions. It was moving over fairly warm ocean waters and faced only moderate wind shear. However, it was surrounded by a fairly dry environment, so it took time for the storm to develop deep convection. On September 8, the center became exposed to the southwest of the strongest thunderstorms. Nevertheless, Margot eventually managed to organize and began gradually strengthening on September 9. A more substantial inner core appeared the next day as the storm turned toward the north, following a weakness in the subtropical ridge.

By September 11, Margot was a well-organized storm with a partial eye and impressive outflow to the north. This brought it to hurricane strength. Margot had its ups and downs over the next couple of days as it chugged northward, with some dry air in the circulation but an inner core and eye occasionally visible on satellite imagery. The net effect of all this was a little more gradual intensification. Margot reached a peak intensity as a high-end category 1 hurricane with 90 mph winds and a central pressure of 970 mb on September 13.

After that point, the storm's core became a little more diffuse, but its windfield expanded as it gained latitude. On September 14, Margot turned right in the face of a ridge blocking its path, and started a slow clockwise loop west of the Azores. During the loop, the storm underwent a gradual decay as dry air eroded its thunderstorm activity. It weakened to a tropical storm on the 15th and lost nearly all convection by early on September 17. At that time, it became post-tropical.

The above image shows Margot at a hurricane on September 12.

Margot's only land impacts as a tropical cyclone were to Cabo Verde right after its formation as a tropical depression on September 7.

Hurricane Lee (2023)

Storm Active: September 5-16

On September 1, a strong tropical wave moved over the Atlantic from the west coast of Africa, producing a large area of vigorous thunderstorms near the coast as it did so. The system steadily gained organization as it moved westward at a fairly fast pace. A low pressure center formed on September 4 and the circulation became well-defined enough to designate the system Tropical Depression Thirteen on September 5. Very high sea surface temperatures in the tropical Atlantic allowed the storm to intensify quickly from that point as it moved west-northwestward. It became Tropical Storm Lee six hours after formation and developed prominant spiral banding almost immediately. Some slight northeasterly shear was not enough to prevent it from becoming a category 1 hurricane by the evening of September 6.

Conditions became even more favorable on September 7 and Lee's structure improved rapidly. The nascent eyewall, which was open to the west in the morning, closed off quite quickly after that and the stage was set for the hurricane to deepen at an incredible pace. The eye cleared out and became symmetric by the evening and Lee strengthened to a category 4 hurricane. That evening, Lee reached its peak intensity as a powerful category 5 hurricane, with maximum winds of 165 mph and a central pressure of 926 mb. These winds were the highest recorded in any Atlantic hurricane since Dorian of 2019. Shortly after that, wind shear disrupted the center of Lee and it began a weakening trend on September 8. The eye clouded over and the central dense overcast eroded, particularly on the west side. This brought the storm back down to a category 3 as it made its closest approach to the northeasternmost Caribbean islands.

Lee maintained its steady west-northwest heading, though its forward speed gradually slowed. The weakening halted on September 10, by which time the storm was a category 2. Its structure subsequently improved, though not to the level of its original burst of intensification. Lee regained major hurricane status that day. Further increases in winds were precluded by the storm's inner core organization, which consisted of a very large outer eyewall and a decaying partial inner eyewall. However, even though the winds did not increase further, the hurricane-force wind field had expanded significantly and continued to grow over the next few days.

By September 11, the storm had turned northwest and slowed further. Its path brought it well northeast of the Bahamas, though the large circulation caused large swells and rip currents to the Caribbean islands and U.S. east coast. Lee also traveled over the cool wake in ocean temperatures left behind by Franklin and exacerbated that issue by upwelling cool waters with its slow forward motion. As a result, a slow weakening began on September 13. The storm turned toward the north that day under the influence of an approaching trough. On September 14, Lee dropped to category 1 intensity and made its closest approach to Bermuda, passing well to the west. Regardless, the storm's large windfield brought a sustained period of tropical storm conditions to the island.

On the 15th, the cyclone became significantly less tropical in appearance, with dry air invading the southern semicircle and displacing convection northward. That evening, tropical storm conditions began across a wide area of coastal New England and Atlantic Canada. Early on September 16, Lee completed extratropical transition. Nevertheless, post-tropical Lee still brought winds to near hurricane force to Nova Scotia when it made landfall in the easternmost part of the province later that day. The center of the storm crossed the Bay of Fundy and made another landfall in New Brunswick very early on September 17. Weakening more quickly, ex-Lee moved over the Gulf of St. Lawrence and finally over Newfoundland on the way out to sea.

The image above shows Lee as a category 5 hurricane. Just after this satellite imagery, mid-level shear from the southwest disrupted the center and weakened the storm. The beginnings of this disruption are already apparent in the image.

Lee did not made landfall as a tropical cyclone but did have direct impacts on Atlantic Canada after becoming post-tropical.

Tropical Storm Katia (2023)

Storm Active: September 1-4

On August 28, a vigorous tropical wave entered the Atlantic. It moved west-northwestward over Cabo Verde, bringing strong storms to the islands on August 30. Two days later, it acquired enough organization to be designated Tropical Depression Twelve. The system began to move north-northwestward toward a low in the eastern Atlantic and strengthened into Tropical Storm Katia. Katia managed to develop a decent area of strong thunderstorms and intensified further, reaching peak winds of 60 mph on September 2.

However, as it gained latitude and moved away from the tropics, wind shear increased out of the south and the storm encountered much drier air. Rapid weakening followed. Katia slowed down and turned back northwest as it ran into a low-level subtropical ridge. It weakened to a tropical depression early on September 4 and then a remnant low later the same day.

The image above shows Katia at its peak intensity on September 2.

Katia did not threaten any land areas as a tropical cyclone during its journey through the eastern Atlantic.