Misplaced Pages

This is an old revision of this page, as edited by Juliancolton (talk | contribs) at 22:03, 16 September 2009 (→Meteorological history: tweak). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Unnamed Hurricane

Category 1 hurricane (SSHWS/NWS)
Unnamed Hurricane on November 1 at peak intensity
Formed	November 1, 1991 (1991-11)
Dissipated	November 2, 1991 (1991-11-03)
Highest winds	1-minute sustained: 75 mph (120 km/h)
Lowest pressure	980 mbar (hPa); 28.94 inHg
Fatalities	None reported
Damage	None
Areas affected	Canada
Part of the 1991 Atlantic hurricane season

Hurricane 8 of the 1991 Atlantic hurricane season was an unnamed tropical cyclone which had rare and complex origins, forming in the center of a nor'easter commonly referred to as the "Perfect Storm". Hurricane Grace formed on October 26, and was eventually absorbed by the much larger extratropical cyclone to the north. This cyclone became a powerful nor'easter that caused severe damage along parts of the east coast of North America and generated extremely high offshore waves. As this storm weakened, it moved over the warmer waters of the Gulf Stream, where its core began to organize.

On November 1, a tropical storm was identified at the center of the non-tropical storm system. It briefly attained Category 1 intensity on the Saffir-Simpson Hurricane Scale before moving ashore in Nova Scotia and fully dissipating just 10 hours thereafter. The hurricane is considered largely a separate entity from the initial nor'easter which caused severe damage, and therefore, the tropical system itself had minor effects on land. It was left unnamed to avoid confusion among the public.

Meteorological history

On October 25, Hurricane Grace formed as a subtropical system, and eventually became a tropical cyclone on October 27. Grace reached its peak intensity with winds of 100 mph (155 km/h) and a minimum central barometric pressure of 980 mbar (hPa; 28.94 inHg), making it a Category 2 on the Saffir-Simpson Hurricane Scale. Meanwhile, an extratropical cyclone formed along an approaching cold front off the New England coast. This storm rapidly intensified and influenced Grace's steering currents, turning the hurricane sharply towards the east.

Hurricane Grace turned northeastward later that day, as the rapidly approaching frontal boundary destroyed the storm's lower-level center. The system became overtaken by the front and subsequently lost its tropical characteristics. It moved north along the front and merged with the large extratropical cyclone to the north. The cyclone significantly strengthened as a result of the temperature contrast between the cold air to the northwest and the warmth and humidity from the remnants of Hurricane Grace. The low pressure system continued deepening as it drifted southeastward and then southwestward towards the United States. While situated 390 mi (630 km) south of Halifax, Nova Scotia, the nor'easter attained its peak intensity with winds of up to 70 mph (110 km/h).

Upon peaking in intensity, the nor'easter turned southward and gradually weakened; by November 1, its pressure had risen to 998 mb. The low moved over warm waters of the Gulf Stream, where bands of convection around the center began to organize. At around this time, the system attained subtropical characteristics. On November 1, while the storm was executing a counter-clockwise loop, a tropical cyclone had been identified at the center of the larger low. Although these conditions are rare, Hurricane Karl during 1980 also formed within a larger non-tropical weather system.

By around 1400 UTC on November 1, an eye feature was forming, and the tropical cyclone reached its peak intensity with maximum sustained winds of 75 mph (120 km/h); these estimates, combined with reports from an Air Force Reserve Unit flight into the storm and confirmation that a warm-core center was present, indicated that the system had become a Category 1 hurricane on the Saffir-Simpson Hurricane Scale. The hurricane accelerated towards the northeast and quickly weakened back into a tropical storm. It made landfall near Halifax, Nova Scotia, at 1400 UTC on November 2 with sustained winds of 45 mph (72 km/h). While the storm was approaching the coast, weather radars depicted curved rainbands on the western side of the system. It fully dissipated about 10 hours after landfall.

Impact and naming

The unnamed hurricane is considered largely a separate system to the larger non-tropical low from which it formed. Therefore, most of the effects from the nor'easter were not perceived to be related to the tropical cyclone. On November 2, a ship reported 50 mph (80 km/h) winds in association with the cyclone. The storm's effects in Canada were minimal, and confined to gusty winds and light precipitation. About 0.27 in (6.9 mm) of rain was reported in Bedford, Nova Scotia. The hurricane caused no significant damage in the region.

Beginning in 1950, the National Hurricane Center named officially recognized tropical storms and hurricanes. The 1991 unnamed hurricane was reported to have met all the criteria for a tropical cyclone; however, it was purposefully left unnamed to avoid confusion amongst the media and the public, who were focusing on the damage from the initial nor'easter, as the hurricane itself was not expected to pose a major threat to land. It was the eighth nameable storm of the 1991 Atlantic hurricane season. Had it been designated a name, it would have been called Henri.

See also

• List of Canada hurricanes
• List of United States hurricanes
• North Atlantic tropical cyclone

References

1. Edward Rappaport (November 13, 1991). "Hurricane Grace Preliminary Report Page 1". National Hurricane Center. Retrieved 2009-09-14.
2. Edward Rappaport (November 13, 1991). "Hurricane Grace Preliminary Report Page 4". National Hurricane Center. Retrieved 2009-09-14.
3. ^ "Ingredients for a real 'perfect storm'". USA Today. Retrieved 2009-09-14. {{cite web}}: Italic or bold markup not allowed in: |publisher= (help)
4. National Climatic Data Center (November 13, 1991). "The Perfect Storm". National Oceanic and Atmospheric Administration. Retrieved 2009-09-14.
5. Richard Pasch. "Unnamed Hurricane Preliminary Report Page 1". National Hurricane Center. Retrieved 2009-09-14.
6. ^ National Climatic Data Center. "Unnamed Hurricane". National Oceanic and Atmospheric Administration. Retrieved 2009-09-14.
7. Richard Pasch and Lixion Avila (March 26, 1992). "Atlantic Hurricane Season of 1980" (PDF). National Oceanic and Atmospheric Administration. Retrieved 2009-09-13.
8. Richard Pasch. "Unnamed Hurricane Preliminary Report Page 2". National Hurricane Center. Retrieved 2009-09-14.
9. Richard Pasch. "Unnamed Hurricane Preliminary Report Page 3". National Hurricane Center. Retrieved 2009-09-14.
10. "Canadian Tropical Cyclone Season Summary for 1991". Canadian Hurricane Centre. Retrieved 2009-09-14.

External links

• The Perfect Storm from the National Climatic Data Center
• National Hurricane Center Preliminary Report

v t e Tropical cyclones of the 1991 Atlantic hurricane season
Timeline
	TSAna TDTwo 3Bob TDFour TDFive 4Claudette TSDanny TSErika TSFabian TDTen 2Grace 1"The Perfect Storm"
Category

• Hurricanes in Canada
• Category 1 Atlantic hurricanes
• 1991 Atlantic hurricane season