1991 Perfect Storm
The 1991 Perfect Storm, also known as The No-Name Storm and the Halloween Gale/Storm, was a damaging and deadly nor'easter that lasted from October 28 to November 2, 1991. While initially an extratropical cyclone, it absorbed Hurricane Grace to its south, later evolving into a small, unnamed Category 1 hurricane. The storm lashed the East coast of the United States with high waves and coastal flooding during its extratropical cyclone phase. Damage from the storm totaled over $200 million and resulted in thirteen fatalities, six of them from the sinking of the Andrea Gail, a fishing boat. The nor'easter received its name, playing off the common expression, after a conversation between Boston National Weather Service forecaster Robert Case and author Sebastian Junger.
The initial area of low pressure developed off the coast of Atlantic Canada on October 28. Forced southward by a ridge to its north, it reached its peak intensity as a large and powerful extratropical cyclone. Moving over warmer waters, the system transitioned into a subtropical cyclone and subsequently into a tropical storm. It then executed a counter-clockwise loop off the Mid-Atlantic states and turned toward the Northeast. On November 1, the system evolved into a Category 1 hurricane, with peak sustained winds of 75 miles per hour. The National Hurricane Center left it unnamed in order to avoid public confusion, since the storm was already widely reported in its earlier, extratropical phase. The tropical system weakened, striking Nova Scotia as a tropical storm before dissipating. The system was the twelfth and final tropical cyclone, the eighth tropical storm, and fourth hurricane in the 1991 Atlantic hurricane season.
Most of the damage occurred while the storm was extratropical, after waves up to struck the coastline from Nova Scotia to Florida and southeastward to Puerto Rico. In portions of New England, the damage was worse than that caused by Hurricane Bob two months earlier. Aside from tidal flooding along rivers, the storm's effects were primarily concentrated along the coast. A buoy off the coast of Nova Scotia reported a wave height of, the highest ever recorded in the province's offshore waters. In Massachusetts, where damage was heaviest, over 100 homes were destroyed or severely damaged. To the north, in Maine, more than 100 homes were affected, including the vacation home of then-President George H. W. Bush. More than 38,000 people were left without power and, along the coast, high waves inundated roads and buildings. Off the shore of New York's Long Island, an Air National Guard helicopter ran out of fuel and crashed; four members of its crew were rescued and one died. Two people died after their boat sank off Staten Island. High waves swept two people to their deaths, one in Rhode Island and one in Puerto Rico, and another person was blown off a bridge to his death. The tropical storm that formed late in the system's duration caused little impact, limited to power outages and slick roads; one person was killed in Newfoundland from a traffic accident related to the storm.
Meteorological history
A volcanic winter is thought to have started with the 1991 eruption of Mount Pinatubo. The large quantities of ash and sulfur dioxide it released into the stratosphere formed an aerosol layer that blocked sunlight from reaching the Earth's surface and reflected solar radiation back into space. This caused global temperatures to drop by up to 0.5 - 0.6 °C from 1991 to 1993. Some meteorologists speculate that the altered jet stream and cooler sea surface temperatures, possibly influenced by Pinatubo's aerosols, may have contributed to the storm's unusual development and strength.The Perfect Storm originated from a cold front that exited the East coast of the United States. On October 28, the front spawned an extratropical low to the east of Nova Scotia. At the same time, a ridge extended from the Appalachian Mountains northeastward to Greenland, anchored by a strong high-pressure center over eastern Canada. The blocking ridge forced the developing extratropical low, which would normally have moved northeastward, to track southeastward and then westward in a rare retrograde motion, initiating a set of meteorological circumstances estimated to occur only once every 50 to 100 years. On October 29, Hurricane Grace, a tropical system that had developed separately in the western Atlantic and that was moving northward, was swept into the warm conveyor belt of the deepening cyclone. By the next day, October 30, Grace was completely absorbed. The merger enhanced the intensity of the nor'easter, fueled by the sharp temperature contrast between cold air to the northwest and the warm, moist air from Grace's remnants.
Image:Unnamed TS storm 02 nov 1991 1305Z borders.jpg|thumb|right|The tropical storm making landfall west of Halifax, Nova Scotia, Canada, on November 2
At approximately 12:00 UTC on October 30, while situated about south of Halifax, Nova Scotia, the nor'easter reached peak intensity, with a central pressure of 972 mbar and winds of up to. The strong pressure gradient between the storm and the blocking high to the north produced damaging winds and very large waves. Between the southern New England coast and the center of the storm, the pressure differential was. A buoy south of Halifax, Nova Scotia, recorded a wave height of, the highest ever measured on the Scotian Shelf, the oceanic shelf off the coast of Nova Scotia. East of Cape Cod, at approximately 15:00 UTC on October 30, a NOAA buoy located at recorded maximum sustained winds of with gusts to, and a significant wave height of. Another buoy, located at, recorded maximum sustained winds of with gusts to and a significant wave height of at approximately 00:00 UTC on October 31.
Upon peaking in intensity, the nor'easter turned southward and gradually weakened. By November 1, its pressure had risen to. The low moved over warm waters of the Gulf Stream, where bands of convection around the center began to organize. Around this time, the system attained subtropical characteristics. While the storm was moving in a counter-clockwise loop, a tropical cyclone had been identified at the center of the larger low. By approximately 14:00 UTC on November 1, an eye feature was forming, and the tropical cyclone reached its peak intensity with maximum sustained winds of ; 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 toward the northeast and quickly weakened back into a tropical storm. It made landfall near Halifax, Nova Scotia, at 14:00 UTC on November 2, with sustained winds of. While the storm was approaching the coast, weather radars depicted curved rainbands on the western side of the system. After crossing over Prince Edward Island, the storm fully dissipated late on November 2.
Preparations and naming
For several days, weather models forecast the development of a significant storm off New England. However, the models were inadequate in forecasting coastal conditions, which in one instance failed to provide adequate warning. In addition, a post-storm assessment found an insufficient number of observation sites along the coast. On October 27, the Ocean Prediction Center noted that a "dangerous storm" would form within 36 hours, with its wording emphasizing the unusual nature of the storm. The National Weather Service likewise issued warnings for the potential storm, providing information to emergency service offices as well as the media. The public, however, was skeptical and did not recognize the threat. The timely warnings ultimately lowered the death toll; whereas the Perfect Storm caused 13 deaths, the blizzard of 1978 killed 99 people, and the 1938 New England hurricane killed 564 people.From Massachusetts to Maine, thousands of people evacuated their homes and sought shelter. A state of emergency was declared for nine counties in Massachusetts, including Suffolk County, as well as two in Maine. In North Carolina, the National Weather Service offices in Hatteras and Raleigh first issued a heavy surf advisory on October 27, more than eight hours before the first reports of high waves. That same day, a coastal flood watch and later a warning was issued, along with a gale warning. The Hatteras NWS office ultimately released 19 coastal flood statements, as well as media reports explaining the threat from the wind and waves, and a state of emergency was declared for Dare County, North Carolina. The warnings and lead times in the region were described as "very good".
In Canada, the threat from the storm prompted the cancellation of ferry service from Bar Harbor, Maine, to Yarmouth, Nova Scotia, as well as from Nova Scotia to Prince Edward Island and between Nova Scotia and Newfoundland.
In its tropical cyclone report on the hurricane, the National Hurricane Center only referred to the system as "Unnamed Hurricane". The Natural Disaster Survey Report called the storm "The Halloween Nor'easter of 1991". The "perfect storm" moniker was coined by author and journalist Sebastian Junger after a conversation with NWS Boston Deputy Meteorologist Robert Case in which Case described the convergence of weather conditions as being "perfect" for the formation of such a storm. Other National Weather Service offices were tasked with issuing warnings for this storm in lieu of the typical NHC advisories. The OPC posted warnings on the unnamed hurricane in its High Seas Forecasts. The National Weather Service State Forecast Office in Boston issued Offshore Marine Forecasts for the storm. Local NWS offices along the East coast covered the storm in their Coastal Waters Forecasts.
Beginning in 1950, the National Hurricane Center named officially recognized tropical storms and hurricanes. The unnamed hurricane was reported to have met all the criteria for a tropical cyclone, but it was purposefully left unnamed. This was done to avoid confusion among 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 the system been named instead, it would have received the name Henri, which was the next name on the 1991 list after Grace.