Sunday, October 20, 2024

Hurricane Oscar (2024)

Storm Active: October 19-22

A tropical wave moved off of Africa on October 10. A low pressure center soon formed in association with the wave and the system trekked steadily across the tropical Atlantic. Along its journey, the low had a pretty well-defined center and was on the verge of tropical cyclone status multiple times, but was unable to muster enough convection to get there in a dry atmospheric environment. On October 18, the low passed just north of the greater Antilles and found another opportunity north of Hispaniola. It was finally named Tropical Storm Oscar during the morning of October 19.

Making up for lost time, Oscar ramped up quickly. Aircraft reconaissance found that the small storm had launched to category 1 hurricane strength by the same afternoon. A ridge north of the cyclone pushed it west-southwestward and the hurricane passed among the Turks and Caicos that evening, including a direct landfall on Great Inagua island early on October 20. The storm slowed down as it approached eastern Cuba that afternoon and made landfall near the country's eastern tip with maximum sustained winds fo 80 mph and a central pressure of 986 mb.

After landfall, Oscar stalled as the steering ridge was replaced by a trough that slowly turned it back toward the north. Its interaction with mountainous terrain weakened it quickly to a tropical storm and disrupted the circulation. During the afternoon of October 21, the storm finally reentered the Atlantic as a minimal tropical storm. It moved northeast into the Bahamas and brought some rain there, but atmospheric conditions had become much more hostile and Oscar was unable to improve its poorly defined structure. The cyclone ultimately dissipated the next day.



The image above shows tiny Oscar just after being upgraded to a category 1 hurricane. The storm was small but made multiple direct landfalls.


The track above shows the full path Oscar and its progenitor system (points where it was not a tropical cyclone are triangles). The system finally developed only near the end of its journey of thousands of miles.

Tropical Storm Nadine (2024)

Storm Active: October 19-20

Around October 15, a broad low pressure system formed in the southwestern Caribbean just east of Nicaragua. The system drifted northwest only very slowly over the next few days, but brought heavy rains to a broad swath of central America. In the early hours of October 19, it became organized enough to be designated Tropical Storm Nadine east of Belize. Nadine organized rapidly but was quickly running out of water as it moved due west. Just before noon, the storm made landfall in Belize with peak winds of 60 mph. After landfall, the storm weakened steadily. It weakened to a tropical depression over Guatemala and turned west-southwest until dissipation on October 20.



The image above shows a strengthening Nadine just before landfall in Belize.


Nadine was a short-lived but large tropical storm which had significant flooding impacts.

Saturday, October 5, 2024

Hurricane Milton (2024)

Storm Active: October 5-11

Around the end of September, a tropical wave moving through the Caribbean interacted with a broad area of rotation over central America to produce a large area of disturbed weather. This disturbance moved northwest into the Bay of Campeche over the next couple of days. After that, it remained mostly stationary just off the western coast of the Gulf of Mexico. On October 4, the system suddenly coalesced quickly around a nascent center of circulation. The next morning, it was designated Tropical Depression Fourteen.

The depression had low shear and warm water to work with and quickly strengthened into Tropical Storm Milton during the afternoon of the 5th. The system was rather small at first, but this allowed it to ramp up quickly, especially once an inner core became established early on October 6. Milton rapidly intensified into a hurricane that day. The system embarked on an unusual motion just south of east across the Gulf of Mexico. Overnight, the storm began a historic burst of strengthening. At 0900 UTC on October 7, the storm was upgraded to a category 2. Just two hours later it became a major hurricane, and after another two hours, a strong category 4. A little before 1600 UTC, it reached category 5 intensity. At 0000 UTC October 8, peaked at a historic intensity of 180 mph sustained winds and a central pressure of 897 mb. This was the lowest pressure recorded in an Atlantic hurricane since 2005 and made Milton the fifth most intense Atlantic hurricane on record by minimum pressure. The cyclone's ascent from tropical depression to category 5 hurricane took 49 hours, the fastest such a feat had ever been observed.

The storm remained incredibly compact throughout this explosion of intensification. A small but very symmetric eye had first appeared the morning of the 7th, and it contracted further after Milton reached category 5 strength until it was under 5 miles in diameter by that evening. The center was surrounded by an area of exceptionally cold cloud tops, the likes of which are seldom seen in the Atlantic basin. The storm's heading took it eastward across the Gulf just north of the Yucatan peninsula, and close enough to bring tropical storm conditions to the northern coastline. Overnight, Milton underwent an eyewall replacement cycle as the tiny eye filled in and the original eyewall was slowly replaced by a secondary larger one. This caused the storm's maximum winds to weaken back to category 4 and minimum pressure to rise temporarily, but it did expand the area of hurricane force winds.

The system recovered well on October 8 though and regained category 5 strength during the afternoon. By that time, Milton was on a faster east-northeastward path toward the central coast of western Florida. It reached an impressive secondary peak intensity of 165 mph winds and a minimum pressure of 902 mb that evening. Fortunately, shear began to increase quickly after that time and the cyclone weakened fairly rapidly from that point. It was down to a category 4 by early on the 9th, and became increasingly disheveled on satellite imagery. Nevertheless, Milton was still at category 3 strength when it made landfall in Florida that evening. The storm's days as a powerful hurricane led to significant storm surge impact, and its quick movement brought wind damage across a swath of the state. Milton was still a category 1 hurricane when it emerged on the Atlantic side of Florida early on October 10. By that time, the storm was interacting with a frontal zone and losing tropical characteristics. It became post-tropical early that evening and continued to gradually spin down as it pushed generally eastward out to sea.



The image above shows Milton near peak intensity on October 7. The cyclone exhibited a "pinhole eye" of only 5 miles across, a feature common for the Atlantic's top few strongest hurricanes. Milton's lowest pressure reading of 897 mb was the lowest observed in the Atlantic for 19 years.


Milton achieved category 5 status twice en route to a category 3 landfall in Florida.

Friday, October 4, 2024

Hurricane Leslie (2024)

Storm Active: October 2-12

Near the end of September, a late season tropical wave entered the Atlantic, cruising slowly westward at a low latitude. The disturbance was dwarfed by the strengthening Tropical Storm (and soon Hurricane) Kirk to its northwest, but it still managed to steadily organize and become Tropical Depression Thirteen on October 2. The cyclone had plenty of moisture to work with, but was buffeted by the outflow of Kirk for another few days, so its intensification was gradual. Nevertheless, it strengthened into Tropical Storm Leslie that night and continued to improve its satellite presentation over the coming days.

The storm found a pocket of conditions favorable enough to reach hurricane strength late on October 4. Leslie surpassed nearby Kirk and again set the mark for easternmost formation of a hurricane in the tropical Atlantic post-September, at a longitude of 34.2° W, further evidence of the anomalous warmth of the Atlantic basin. Leslie turned west-northwest and then northwest over the next couple of days and encountered some mid-level try air. It had some success battling off this dry air intrusion for a time, and managed to intensify a bit more on October 6, reaching its first peak intensity of 90 mph winds and a pressure of 982 mb.

The next day, Leslie's structure began to slowly degrade. Although the storm was still producing very deep convection, the core became more lopsided and the maximum winds decreased. The system was downgraded to a tropical storm early on October 8. It rebuilt its eyewall and made a comeback later in the day however, regaining hurricane status. Leslie remained surprisingly resilient and deepened more on October 9. Its eye partially cleared out and it beat its previous strength mark that evening, reaching a new peak intensity as a category 2 hurricane with 105 mph winds and a central pressure of 972 mb.

Upper-level winds from a disturbance to the storm's west increased markedly over Leslie on the 10th, however. This initiated rapid weakening, an the storm also began curving north and then northeast out to sea. By October 11, the cyclone was down to moderate tropical storm strength and was producing convection only sporadically. The next day, Leslie dissipated altogether.



The image above shows Leslie near its second peak intensity as a category 2 hurricane on October 9.



Leslie did not affect land as a tropical cyclone.