In spite of a decrease in convection shortly after forming, the large depression remained well organized, with a 575 mile wide wind field. On August 22, as it passed 140 miles (225 km) miles to south of the Cape Verde islands, deep convection developed over the center of circulation, and early on August 23 the depression strengthened into Tropical Storm Debby about 300 miles southwest of Cape Verde. Banding features continued to organize as the system slowly strengthened, and on August 23 Debby reached its peak intensity of 50 mph over the open waters of the Atlantic Ocean. Forecasters predicted Debby to continue to strengthen to reach hurricane status, while its projected path placed the storm in an area of warm water temperatures and moderate upper level shear.
Shortly after reaching its peak intensity, Debby encountered an area of dry air, and as a result weakened. The low level circulation detached itself from the dying convection while the system as a whole continued west-northwestward. Convection redeveloped over a portion of the center, while banding features redeveloped as well. Organization continued, and Debby again reached its peak intensity of 50 mph on August 24. Southerly wind shear displaced the convection to the north of the center, and Debby weakened to a weak tropical storm on August 25. The center of the storm became asymmetric and elongated, and on August 26 Debby weakened to a tropical depression. Convection remained minimal and it quickly degenerated into a remnant area of low pressure. The low turned to the north and north-northeast ahead of an approaching trough, and on August 28 the low dissipated.
The government of the Cape Verde islands gave out tropical storm warnings at the same time with the issuance of the first advisory on Tropical Depression Four, meaning tropical storm conditions were expected in the area within 24 hours. The National Hurricane Center stated that heavy rainfall, possibly as high as 10 inches in mountainous areas, would be possible in the territory, possibly causing life-threatening flash floods and mudslides.
However, because of a reformation further to the south, tropical storm warnings were discontinued as the depression passed away from the area. While passing around 115 miles to the southwest of the southwestern most islands, the depression produced a 35 mph wind gust at Fogo and some rainfall, though no damage was reported.
Long range forecasts brought the storm near Bermuda. However Debby remained over 900 miles from the island at its closest approach.
Though the storm was forecasted to remain far away from the Gulf of Mexico, investors tracking the storm caused the price of crude oil to rise 60 cents a barrel due to the possible impact to oil installations.
Fogo, Cape Verde
Fogo (Portuguese for "fire") is a volcanic island in the Sotavento group of Cape Verde. It is the most prominent of the group, rising to nearly 3,000 m (10,000 ft) above sea level at Pico do Fogo.
Hurricane Isaac (2006)
Hurricane Isaac was the final tropical cyclone of the 2006 Atlantic hurricane season. It reached peak strength of Category 1 just before striking Newfoundland, where it produced tropical storm-force winds. Isaac followed the path of the three previous storms in the Atlantic basin, Florence, Gordon, and Helene. Isaac formed in the central North Atlantic Ocean and moved eastward toward Europe.
Hurricane Isaac formed off the coast of Africa on September 18. Intensification was partly suppressed by high wind shear and by cool sea surface temperatures in the wake of Hurricanes Gordon and Helene. Isaac reached tropical storm strength on September 28 and entered an area of low wind shear, allowing it to strengthen into an 85 mph (137 km/h) hurricane. Its intensity nearly matched forecasts made with the Statistical Hurricane Intensity Prediction Scheme (SHIPS).
On October 1, Isaac turned northeast and struck Newfoundland as a tropical storm. Two days later, it merged with a newly formed baroclinic low off the east coast of the United States. The merged system was forecast to move toward the area between Greenland and Great Britain. Isaac produced rainfall over Newfoundland of up to 25 mm (1 in). No deaths or damage were reported. Isaac was the second storm to affect Newfoundland during the season, the other being Hurricane Florence.
Isaac started as a tropical wave that moved away from Africa on September 18. An area of disturbed weather began interacting with the tropical wave as deep convection increased on September 23. The convection began to organize, and weather agencies to release the first Dvorak numbers on the system.
The SHIPS models predicted that the system would become a hurricane with maximum sustained winds of 88 knots (150 km/h) after 120 hours. However, the system was slow to organize and a Tropical Cyclone Formation Advisory was not issued by the National Hurricane Center (NHC) until four days later. The NHC, however, decided the convection was too ephemeral to justify classification as a tropical depression and the TCFA was discontinued. Three days later, on September 27 another TCFA was issued, announcing the formation of the ninth tropical depression of the Atlantic season.
The depression strengthened into Tropical Storm Isaac on September 28, just twelve hours after the cyclone's formation. Deep convection was slow to form that day since the system remained over cold waters that had upwelled in the wake of Hurricanes Gordon and Helene. The next day, the cyclone moved west-northwestward and started gaining subtropical characteristics while its convection deepened. Vertical shear weakened as the system moved away from the cold, upwelling waters and the core of Isaac started re-developing. Atmospheric conditions remained favorable and Isaac reached hurricane status on September 30. Isaac continued strengthening a little bit during the next day near Bermuda, reaching its peak intensity with sustained winds of 85 mph (135 km/h) and minimum central pressure of 985 mbar. Isaac's winds quickly weakened to 80 mph (130 km/h), but its central pressure did not change.
Isaac encountered cooler waters as it approached Newfoundland on October 1, and weakened into a tropical storm on October 2. Isaac made landfall on the Avalon Peninsula as a weak tropical storm on October 2 and maintained tropical cyclonic structure and deep convection. Soon after, Isaac turned into an extratropical storm and merged with a larger extratropical system on October 3 off the Avalon Peninsula.
A tropical storm "watch" was sent up on October 1 for the Avalon Peninsula. The watch was upgraded to a tropical storm "warning" the next day. Another watch was issued for the Burin and Bonavista peninsulas, although it was quickly removed. On October 2, all tropical cyclone watches and warnings were taken away. Heavy rain and gusty winds were expected. Because of this, rainfall warnings were declared for parts of southern Newfoundland. Wind and gale advisories were also given out over the Atlantic Ocean.
On October 2, a ship called the "Elektra" (call sign SIWB) reported winds of while it was located about to the east of the center of the storm. Two other ships, many buoys, and a few oil platforms also recorded strong winds. Waves off the coast reached about heigh.
Isaac did not have much impact on land. No people were killed, and there was no bad damage. However, some parts of the Avalon Peninsula had tropical storm conditions. At Cape Race, constant winds were as high as , with wind gusts of up to . The strongest winds remained offshore. Since the storm was moving so quickly, it did not drop much rainfall; precipitation usually amounted to below .
Baroclinic