Hurricane Isaac (2006)

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Hurricane Isaac

Category 1 hurricane (SSHS)

Hurricane Isaac near peak intensity.

Formed

September 27, 2006

Dissipated

October 3, 2006

Highest
winds

85 mph (140 km/h) (1-minute sustained)

Lowest pressure

985 mbar (hPa; 29.1 inHg)

Deaths

None reported

Damage

Minimal

Areas
affected

Newfoundland

Part of the
2006 Atlantic hurricane season

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 a 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).^[1]

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.^[2]^[3]^[4]^[5]

1 Storm history
2 Preparations
3 Impact
4 See also
5 References
6 Other websites

[change] Storm history

Storm path

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.^[6] 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.^[7]

Isaac on October 1.

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.^[2]^[7]

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.^[8]^[9]^[10]^[11]^[2]

[change] Preparations

Several tropical cyclone watches and warnings were issued in association with Hurricane Isaac. A tropical storm watch was issued on October 1 for the Avalon Peninsula. This was upgraded the next day to a tropical storm warning, and a tropical storm watch was issued for the Burin and Bonavista Peninsulas. These warnings and watches were discontinued the same day. The final warning issued was a tropical storm warning for the Avalon Peninsula on October 2.^[7]

The Atlantic Storm Prediction Center released a warning for Prince Edward Island and northern Nova Scotia to expect 30-50 mm (1-2 in) rainfall totals on October 1 from the newly-formed extratropical system. A hurricane-force wind warning was issued for Laurentian Fan, Newfoundland with gale and storm-force wind warnings for the eastern part of the Maritimes Marine District. A rainfall warning was issued for Southeastern Newfoundland, advising of the threat of 40-50 mm rainfall.^[12]^[13]

[change] Impact

The strongest winds on land in Newfoundland were reported at Cape Race, where a maximum gust to 96 km/h (60 mph) with a sustained wind of 74 km/h (46 mph) was recorded. At Cape Pine, a peak wind of 76 km/h (47 mph) was reported.^[14] However, due to Isaac's small size and swift forward speed, winds were lighter over most of the Avalon Peninsula. Winds in St. John's, Newfoundland reached only 33 mph (54 km/h).^[14] Canadian buoy 44138 reported wind gusts up to 56 knots and sustained winds of 50 knots.^[15] During the extratropical transition on October 3, three oil platforms reported 48-56 knot winds east-southeast of the circulation center. The buoy also reported five meter high waves.^[16]^[7] Rainfall totals were 26 mm (1 in) at Cape Race, 10 mm (0.4 in) at St. John's and 19 mm (0.75 in) at Cape Pine.^[14] Otherwise, Isaac's impact on Newfoundland was minimal with no deaths or damage reported.