Hurricane Ernesto (2024)

Storm Active: August 12-20

During the second week of August, a tropical wave traversed the tropical Atlantic. Dry air near the wave limited its shower activity, so not much development occurred at first. Some spin became evident on satellite imagery around August 11, but convection remained very limited until the next day. During the afternoon of August 12, the system acquired a well-defined center and was designated Tropical Storm Ernesto a few hundred miles east of the Leeward Islands. Newly-formed Ernesto was moving at an extremely fast forward speed of 28 mph. On that heading, it quickly approached the Caribbean and the center passed near the island of Guadeloupe early on August 13.

Considering the struggles its precursor tropical wave had, Ernesto's transformation on the 12th and the 13th was extraordinary: the storm ballooned in size and developed large and pronounced banding features which brought heavy rains to locations hundreds of miles from the center. The organization of the core lagged a little behind but the cyclone nevertheless began to intensify steadily as it moved west-northwest through the northeast corner of the Caribbean. Ernesto was a strong tropical storm by the time it passed among the Virgin Islands that evening. Shortly after, the center of circulation emerged into the Atlantic, but a large blob of convection associated with the system persisted for the next day well to the south. This brought further heavy rain to Puerto Rico and neighboring areas.

During the morning of August 14, Ernesto strengthened into a hurricane. A trough of low pressure over the subtropical Atlantic turned the storm to the right throughout the day. Soon, the storm was headed north-northeast toward Bermuda. It underwent some structural changes too: periodic dry air intrusions prevented Ernesto from completing an eyewall, but lent the cyclone an spiral satellite apperance on the 15th. The radii of gale force winds also increased significantly in size and the pressure dropped. Hence even though conditions weren't ideal, the warm water and atmospheric instability helped Ernesto to reach category 2 hurricane strength by that evening. The storm peaked at 100 moh sustained winds and a central pressure of 969 mb as it approached Bermuda.

The trough that was steering Ernesto exited to the northeast by the 16th without fully capturing the cyclone. This slowed the storm's forward speed significantly. At the same time, wind shear increased markedly that day and pushed more dry air into the center of Ernesto. This weakened the storm, but it was still a category 1 hurricane when it made a direct landfall in Bermuda early on August 17. It moved quite slowly past the island, leading to a prolonged period of gale force winds. Early on the 18th, Ernesto was finally leaving the island behind and it weakened to a tropical storm. The cyclone found a pocket of more favorable conditions farther north and reintensified to a hurricane that day as a ragged eye appeared on satellite. A second trough arrived at the U.S. east coast to give Ernesto its final boost out to sea and the storm began accelerating toward the northeast. It stayed over the Gulf Stream waters long enough to reach a secondary peak intensity of 90 mph winds and a pressure of 968 mb during the morning of August 19. Late that day, though, it crossed the northern wall of the warm current and sea surface temperatures underneath Ernesto plummeted. The cyclone began to weaken and begin extratropical transition. However, it was still a hurricane when it passed just southeast of Newfoundland late the same evening, bringing gale force winds to the nearest corner of the island. Ernesto became post-tropical during the morning of August 20. The system moved quickly northeast across the Atlantic and impacted the UK a few days later.

The image above shows Ernesto as a category 2 hurricane on August 16 approaching Bermuda from the southeast.

Ernesto moved through the northeast Caribbean before making a direct landfall in Bermuda.

Hurricane Debby (2024)

Storm Active: August 2-9

During the last week of July, a tropical wave crossed the tropical Atlantic and moved along the northern Caribbean islands. For much of that journey, dry air stifled its development, but by August 1 it was starting to show some more signs of organization. The disturbance passed over Hispaniola and Cuba, bringing heavy rainfall. The land interaction slowed development a bit longer, but the system found a window to consolidate south of central Cuba later on August 2 and was classified Tropical Depression Four. The storm was initially steered west-northwest by a strong subtropical ridge, but a weakness over the eastern U.S. gave it the opportunity to turn northwest on August 3. The center passed over western Cuba that morning.

That evening, the cyclone emerged into the Gulf of Mexico. It found a much more humid atmosphere and low wind shear, which allowed the system to begin strengthening and become Tropical Storm Debby that evening. Thunderstorm activity began to build near the center of circulation early on August 4. Radar imagery also showed an eyewall building throughout the day as Debby paralleled the coastline of western Florida. The storm then turned north-northeast overnight and reached category 1 hurricane strength. It made landfall in the Big Bend of Florida during the morning of August 5 at its peak intensity of 80 mph winds and a central pressure of 979 mb.

Debby entered an area of weak steering currents and slowed down that day as it moved farther inland. Its winds diminished and the inner core decayed that evening as the cyclone was cut off from energy from the ocean. Nevertheless, a severe flooding event began to unfold for the southeast U.S. due to the slow movement of the storm. The center crossed Georgia and emerged over the Atlantic near the Georgia-South Carolina border during the afternoon of August 6. At the time, it was still hanging on to minimal tropical storm intensity. Though it moved over water, the storm did not travel eastward far enough to find the highest oceanic heat content of the region in the Gulf stream. As a result, the circulation remained mostly devoid of convection near the center and only gradually built back outer bands on August 7. It also underwent modest deepening, but did not much resemble a typical tropical storm. A rebuilding ridge to Debby's east began to push it back to the west of north that evening and made landfall in northern South Carolina overnight.

The storm's rains spread northward as it weakened inland on August 8. Late that afternoon, it weakened to a tropical depression. By early the next morning, the system became post-tropical over Virginia. The remnants of Debby sped off to the northeast and brought additional rain to the mid-Atlantic and regions farther north over the next couple of days.

The image above shows Debby at peak intensity as a category 1 hurricane in the early morning hours of August 5, just before Florida landfall.

Debby's slow movement across the U.S. southeast brought large rainfall totals, though flooding impacts were not as severe as initially feared.