Hurricane Isaac (2006)

Infobox Hurricane
Name=Hurricane Isaac
Type=hurricane
Year=2006
Basin=Atl
Image location=Hurricane Isaac 01 oct 2006 1435Z.jpg


Formed=September 27, 2006
Dissipated=October 3, 2006
1-min winds=75
Pressure=985
Da

Fatalities=None reported
Areas=Newfoundland
Hurricane season=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 attained tropical storm intensity on September 28 and entered a region 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). [ [http://www.aoml.noaa.gov/hrd/tcfaq/F2.html FAQ: Hurricanes, Typhoons, and Tropical Cyclones] ]

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. [http://weather.unisys.com/hurricane/atlantic/2006/ISAAC/track.dat Unisys' Hurricane Isaac BT Data] ] [http://www.nhc.noaa.gov/archive/2006/al09/al092006.discus.017.shtml? Hurricane Isaac Discussion 17] ] [http://www.nhc.noaa.gov/archive/2006/al09/al092006.discus.020.shtml? Hurricane Isaac Discussion 20] ] [http://bbsnews.net/bbsn_photos/Hurricane-Tropical-Storm-Graphics-Photos-2006/H_Isaac_09_30_2006_11pm BBS News - Issac Advisory 14 (September 30)] ]

History

Isaac originated as a tropical wave that exited from Africa on September 18. An area of disturbed weather started 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. [http://tcweb.fnmoc.navy.mil/tc-bin/tc_home.cgi Naval Research Laboratory page on Isaac] ] 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. [http://www.nhc.noaa.gov/pdf/TCR-AL092006_Isaac.pdf Hurricane Isaac Tropical Cyclone Report by the National Hurricane Center] ]

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 slightly intensified during the next day near Bermuda, reaching its maximum 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. [http://weather.unisys.com/hurricane/atlantic/2006/ISAAC/track.dat Unisys' Hurricane Isaac BT Data] ]

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 minimal tropical storm on October 2 and maintained tropical cyclonic structure and deep convection. Soon after, Isaac transitioned into an extratropical storm and merged with a larger extratropical system on October 3 off the Avalon Peninsula. [http://www.nhc.noaa.gov/archive/2006/tws/MIATWSAT_oct.shtml? October 2006 Monthly Weather Review] ] [http://www.nhc.noaa.gov/archive/2006/al09/al092006.discus.013.shtml? Hurricane Isaac Discussion 13] ] [http://www.nhc.noaa.gov/archive/2006/al09/al092006.discus.018.shtml? Hurricane Isaac Discussion 18] ] [http://www.nhc.noaa.gov/archive/2006/al09/al092006.discus.019.shtml? Hurricane Isaac Discussion 19] ] [http://weather.unisys.com/hurricane/atlantic/2006/ISAAC/track.dat Unisys' Hurricane Isaac BT Data] ]

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.

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 portion of the Maritimes Marine District. A rainfall warning was issued for Southeastern Newfoundland, advising of the threat of 40-50 mm rainfall. [http://www.atl.ec.gc.ca/weather/hurricane/bulletins/20061001233924.Isaac.txt.en Canadian Hurricane Center bulletin on Isaac at 9:30 NDT on October 1] ] [http://www.ns.ec.gc.ca/weather/hurricane/bulletins/20061003022851.Isaac.txt.en CHC Advisory 24 on Hurricane Isaac (Afternoon of October 3)] ]

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. [http://www.atl.ec.gc.ca/weather/hurricane/bulletins/20061003022851.Isaac.txt.en CHC Archive on Hurricane Isaac] ] 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). [http://www.atl.ec.gc.ca/weather/hurricane/bulletins/20061003022851.Isaac.txt.en CHC Archive on Hurricane Isaac] ] Canadian buoy 44138 reported wind gusts up to 56 knots and sustained winds of 50 knots. [http://www.nhc.noaa.gov/archive/2006/al09/al092006.discus.021.shtml? Hurricane Isaac Discussion 21] ] 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. [http://www.ns.ec.gc.ca/weather/hurricane/bulletins/20061002180428.Isaac.txt.en Issac Advisory at 3:30 pm NDT October 2] ] 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. [http://www.atl.ec.gc.ca/weather/hurricane/bulletins/20061003022851.Isaac.txt.en CHC Archive on Hurricane Isaac] ] Otherwise, Isaac's impact on Newfoundland was minimal with no deaths or damage reported.

See also

* List of Atlantic hurricanes

References

External links

Wikinewshas|related news
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* The NHC's [http://www.nhc.noaa.gov/archive/2006/ISAAC.shtml? archive on Hurricane Isaac] .
* The CHC's [http://www.ns.ec.gc.ca/weather/hurricane/bulletins_e.html#2006:Isaac archive on Hurricane Isaac] .