Hurricane Imelda (2025)

Storm Active: September 27-October 2

Around September 16, the first of a pair of tropical waves entered the Atlantic basin from the east. Unlike its successor, which would become Hurricane Humberto, the leading wave did not generate much thunderstorm activity for much of its journey across the tropical Atlantic. It first attracted notice on September 21, when this activity increased markedly as it approached the Leeward Islands. The system remained too disorganized to consolidate into a tropical cyclone, but it brought significant rainfall across the Caribbean. It first impacted the Leewards on the 23rd, Puerto Rico the next day, and the Dominican Republic on the 25th. After that time, the disturbance slowed down and turned toward the north. Less land interaction and favorable atmospheric conditions allowed it to establish a circulation over the next couple of days. Eventually, the system was designated Tropical Depression Nine a little off the northern coast of east Cuba.

Despite achieving tropical cyclone status, the depression was very still broad and disorganized at first, with mid-level spin displaced from the low-level center. It began to build a dense area of convection near the developing center on the 28th. That afternoon, it was upgraded to Tropical Storm Imelda. Around the same time, the center began to move northward through the Bahamas, bringing tropical storm conditions to some of the islands. Imelda deepened steadily over the next few days and winds increased. By the time it exited the Bahamas on September 29, it was a strong tropical storm. It was upgraded to a hurricane during the morning of September 30.

Imelda did not have the traditional appearance of a hurricane on satellite imagery; some dry air was present near the center and convection did not completely surround it. Nevertheless, it continued strengthening. That day it also took a sharp turn toward the east-northeast. This was due to an approaching trough near the U.S. east coastline and a binary interaction with Hurricane Humberto to Imelda's northeast. As the two cyclones approached each other, the Fujiwhara effect caused them to rotate in a counterclockwise direction around the "center of gravity" between the two. This center of gravity was recurving northeast, so Humberto's eastward progress slowed some, while Imelda was yanked quickly eastward out to sea away from land.

Imelda closed off a circular eyewall and continued to intensify. During the morning of October 1, the cyclone reached its peak intensity as a category 2 hurricane with 100 mph winds and a minimum central pressure of 966 mb. After that time, wind shear increased due to the encroaching trough, but Imelda managed to temporarily maintain its strength due to a favorable trough interaction. This meant it was still near peak intensity when the center of circulation passed within a handful of miles of a direct landfall of Bermuda late on October 1. The center's passage just south of the island brought hurricane-force winds to Bermuda for a few hours, before Imelda sped off to the east.

After that, the storm began to weaken and lose its remaining tropical characteristics. During the morning of October 2, Imelda transitioned to a post-tropical cyclone. Its remnants arced northeastward over the open north Atlantic until they dissipated several days later.

The image above shows Imelda on October 1 at peak intensity. The island of Bermuda is visible at right, directly in the hurricane's path.

Imelda took a sharp turn eastward around September 30, preventing it from affected mainland North America. Nevertheless, the storm brought significant impacts to the Bahamas and Bermuda.

Hurricane Humberto (2025)

Storm Active: September 24-October 1

On September 18, a vigorous tropical wave entered the tropical Atlantic ocean from the west African coastline. It tracked west-northwestward and steadily organized until it was designated Tropical Storm Humberto northeast of the Lesser Antilles on September 24. Despite some wind shear out of the west early on, Humberto steadily strengthened from formation. On the 25th, spiral bands and a central core appeared on satellite imagery. The storm became a hurricane the next morning. Meanwhile, the storm's forward speed slowed significantly due to weak steering currents.

Atmospheric conditions soon improved further over the storm. On September 26, Humberto rapidly intensified. An eye appeared and cleared out extremely quickly; within an 18 hour period, the storm went from a minimal hurricane to a strong category 4 hurricane. Overnight, an eyewall replacement cycle briefly halted strengthening, but the system rebounded surprisingly quickly. September 27 brought an even more symmetric eye surrounded by a larger ring of extremely cold cloud tops. This coincided with Humberto reaching its peak strength as a category 5 hurricane, with maximum sustained winds of 160 mph and a minimum central pressure of 924 mb. Humberto was the second category 5 hurricane of the season, after Hurricane Erin. This made 2025 the second consecutive year with multiple category 5 Atlantic hurricanes, due to the formation of Beryl and Milton in 2024. Such an event only occurred once before on record, during the 1932-1933 seasons.

During this episode of strengthening, Humberto's heading meandered a little, but the subtropical ridge generally pushed it west-northwestward at a slow but steady pace. Although conditions remained favorable a bit longer, another outer eyewall soon formed and disrupted the storm's internal structure, causing it to weaken back to a category 4 by the 28th. The core continued to evolve, but the storm remained a category 4 until the following evening, when shear increased markedly. This shear was associated with an approaching trough and in part due to the increasing proximity between Humberto and Imelda, which was approaching from the southwest. This shear destroyed the hurricane's core and exposed the center, leading to rapid weakening. By the afternoon of September 30, Humberto was down to category 1 strength, though it maintained an area of strong storms northeast of the center.

Meanwhile, the hurricane recurved toward the north and then sharply turned toward the east in the mid-latitue westerly flow. Humberto met a quick demise soon after: its circulation was absorbed into the approaching front during the morning of October 1.

The image above shows the impressive satellite signature of Humberto at its peak intensity as a category 5 hurricane on September 27.

Humberto did not affect any land areas as a tropical cyclone.

Hurricane Gabrielle (2025)

Storm Active: September 17-25

A tropical wave entered the Atlantic ocean around September 12 and moved slowly westward over the next several days. It produced a significant amount of thunderstorm activity but remained quite disorganized. The system was eventually designated Tropical Depression Seven on September 17. At the time, it was a little past halfway from Africa to the Windward Islands. Despite achieving tropical depression status, the cyclone was still a mess, with almost all convection displaced east of the center. Furthermore, the center itself was a warring group of vorticies rotating around one another. Later that day, the center reformed further north, coaxed poleward by an upper-level low over the subtropics. The storm's winds also increased enough that it was upgraded to Tropical Storm Gabrielle.

Gabrielle evened out to a more steady west-northwest heading on the 18th and consolidated its circulation, but struggled to produce thunderstorm activity. For most of the day, it was little more than a naked swirl. That evening, it began to put up a better fight against westerly wind shear and storm activity blossomed in the eastern semicircle. Nevertheless, atmospheric conditions remained hostile through the next day. It was only on the 20th that shear lessened and Gabrielle was able to start intensifying again. The storm spent the next few days curving around the western edge of the subtropical ridge, first turning toward the north and toward the east. This path kept it east of Bermuda, too far to cause any direct impacts to the island. This was fortunate, because Gabrielle strengthened significantly.

On the 21st, it was upgraded to a hurricane. Shortly after that, the cyclone's satellite presentation improved markedly. An eye quickly cleared out and became more symmetric. Gabrielle vaulted to major hurricane strength by the morning of September 22. That afternoon it reached its peak intensity as a category 4 hurricane, with maximum winds of 140 mph and a central pressure of 948 mb. The storm accelerated toward the east-northeast and encountered gradually increasing wind shear as well as decreasing ocean heat content. This began a decaying trend, though it remained a significant hurricane.

Gabrielle began to lose tropical characteristics late on September 24 as the central core collapsed and it weakened to a category 1 hurricane. By this time, the storm was speeding eastward toward the central Azores. During the afternoon of September 25, a few hours before arriving at the islands, Gabrielle transitioned to a post-tropical cyclone. This did not prevent the cyclone from bringing strong winds, storm surge, and brief heavy rains to the Azores; during the storm's passage, hurricane-force gusts were recorded at sea level as well as hurricane-force sustained winds at higher elevations. A fully extratropical ex-Gabrielle exited the island chain toward the east by the next morning. Its remnants passed near the coast of Portugal before dissipating days later.

The image above shows Gabrielle as a category 4 hurricane on September 22.

Gabrielle did not directly impact any land areas as a tropical cyclone, but did make a direct hit on the Azores shortly after losing tropical characteristics.