Hurricane Karen was a hurricane of non-tropical origin that formed in October of the

2001 Atlantic hurricane season The 2001 Atlantic hurricane season was a fairly active Atlantic hurricane season that produced 17 tropical cyclones, 15 named storms, nine hurricanes, and four major hurricanes. The season officially lasted from June 1, 2001, to November 30, 200 ...

. It developed out of the interaction between a

cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure. It often forms behind an extratropical cyclone (to the west in the Northern ...

and an upper level trough on October 10 located to the south of

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, and quickly strengthened as an

extratropical Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are low-pressure areas which, along with the anticyclones of high-pressure areas, drive the weather over much of the Earth. Extratropical cyclones are capable of p ...

storm. The storm passed near Bermuda on October 12, producing hurricane-force winds on the island. It then organized, becoming a

subtropical cyclone A subtropical cyclone is a weather system that has some characteristics of both tropical and an extratropical cyclone. As early as the 1950s, meteorologists were uncertain whether they should be characterized as tropical or extratropical cyclon ...

on the 12th and a

tropical cyclone A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depen ...

on the 13th. Karen strengthened to reach 80 mph (130 km/h) winds as a Category 1 hurricane on the Saffir-Simpson Hurricane Scale, and after weakening over cooler waters, it made landfall on

Nova Scotia Nova Scotia ( ; ; ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. Nova Scotia is Latin for "New Scotland". Most of the population are native Eng ...

as a tropical storm. It quickly became extratropical. On Bermuda, winds from the precursor extratropical storm produced moderate damage, primarily to power lines and marine interests. Over 2/3 of the island's power subscribers were left without power during the worst of the storm, and several boats sank or ran aground from the high winds. Damage on Bermuda totaled to over $1.4 million (2001 USD; $1.7 million 2008 USD). In Atlantic Canada, Tropical Storm Karen produced light winds and rain, but caused minimal damage.

Meteorological history

A cold front stalled a couple hundred miles southeast of

on October 10. During that day, a strong upper-level trough moved southeastward off the southeast coast of the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territori ...

. Due to several factors, including upward motion and strong diffluence—the rate at which a fluid moves—the area became baroclinically unstable. This caused the interaction between the trough and the front to develop into an extratropical low about 345 miles (555 km) southeast of Bermuda on October 11. The low moved quickly northward, then northwestward, strengthening quickly due to the instability of the atmosphere. Late on October 11, the system slowed, and the upper-level circulation became aligned with the low-level circulation. The extratropical storm began to develop tropical characteristics late on October 11, including surface temperatures warmer than the surrounding environment, and vertical wind characteristics of a tropical cyclone. Based on its organization, the system developed into Subtropical Storm One early on October 12 while located about 35 miles (55 km) south of Bermuda. While passing to the south of Bermuda, the subtropical storm maintained winds of 70 mph (110 km/h), with wind gusts on the island surpassing 100 mph (160 km/h). After becoming dissociated from the

Westerlies The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and trend t ...

, the system turned northward, and began to develop convection over the center. In addition, the frontal characteristics of the subtropical storm continually weakened. On October 13, based on an Advanced Microwave Sounding Unit observation that stated that a warm core was present throughout the system, the National Hurricane Center designated the system as a

tropical storm A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Dependi ...

, and gave it the name ''

Karen Karen may refer to: * Karen (name), a given name and surname * Karen (slang), a term and meme for a demanding woman displaying certain behaviors People * Karen people, an ethnic group in Myanmar and Thailand ** Karen languages or Karenic l ...

''. At this point, Karen was located 200 miles (320 km) north of Bermuda. Karen slowly strengthened over the warm waters of the Gulf Stream, and the storm intensified to a hurricane later on October 13. Convection continued to develop, and organized into a ring around the eye as Karen reached its peak intensity of 80 mph (130 km/h) on October 14 while located about 400 miles (640 km) south of

Halifax, Nova Scotia Halifax is the capital and largest municipality of the Provinces and territories of Canada, Canadian province of Nova Scotia, and the largest municipality in Atlantic Canada. As of the 2021 Census, the municipal population was 439,819, with 348 ...

. Karen quickly weakened as it moved over cooler waters, and late on October 14 it degenerated back into a tropical storm as it accelerated northward.

Convection Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the conve ...

gradually decreased, and Karen made landfall on southwestern

with winds of 45 mph (70 km/h) on October 15. Karen retained its tropical characteristics during and after making landfall, based on a research flight out of Halifax intended to study the early stages of extratropical transition. The flight reported arced bands and a warm-core system transitioning into a more typical mid-latitude system. Under the influence of a mid-latitude system, the storm turned sharply to the northeast, and after losing the remaining of its convection it became extratropical shortly after landfall. Continuing northward, the remnant low quickly weakened, and dissipated as it was absorbed by a larger extratropical storm over the

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Preparations

On October 10, as the precursor extratropical storm was forming, the

Bermuda Weather Service The Bermuda Weather Service is Bermuda's national meteorological service. It provides public, marine, tropical and aviation weather forecasts as well as warnings and climatolological services. The service began operations under contract from the De ...

issued a gale and later a storm warning for the

island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atolls can be called islets, skerries, cays or keys. An island ...

, expecting winds of 50 to 60 mph (60 to 95 km/h). Several radio interviews and television stations issued information on the expected storm. Many residents believed they were insufficiently warned, though it is acknowledged that emergency managers and citizens pay less attention to gale warnings than they do for tropical cyclone warnings. On October 12, as the storm was passing to the south of the island, officials closed all schools and government offices. Many private businesses closed as well. At the time of Karen's landfall, gale warnings were issued for coastal waters, while inland wind warnings were in effect for

Cape Breton Cape Breton Island (french: link=no, île du Cap-Breton, formerly '; gd, Ceap Breatainn or '; mic, Unamaꞌki) is an island on the Atlantic coast of North America and part of the province of Nova Scotia, Canada. The island accounts for 18. ...

. In addition, heavy rainfall warnings were issued for large portions of

including Halifax, southeastern

New Brunswick New Brunswick (french: Nouveau-Brunswick, , locally ) is one of the thirteen provinces and territories of Canada. It is one of the three Maritime provinces and one of the four Atlantic provinces. It is the only province with both English and ...

Fundy National Park Fundy National Park is a national park of Canada located on the Bay of Fundy, near the village of Alma, New Brunswick. It was officially opened on 29 July 1950. The park showcases a rugged coastline which rises up to the Canadian Highlands, the ...

, and

Prince Edward Island Prince Edward Island (PEI; ) is one of the thirteen provinces and territories of Canada. It is the smallest province in terms of land area and population, but the most densely populated. The island has several nicknames: "Garden of the Gulf", ...

Impact

Bermuda

While passing to the south of the island, the tight

pressure gradient In atmospheric science, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular location. The p ...

between the precursor extratropical storm and high pressures resulted in strong winds on the island, including sustained winds of hurricane status at Fort George. Gusts on the island officially peaked at 100 mph (161 km/h) at

Devonshire Devon ( , historically known as Devonshire , ) is a ceremonial county, ceremonial and non-metropolitan county, non-metropolitan counties of England, county in South West England. The most populous settlement in Devon is the city of Plymouth, ...

. A cruise ship anchored at harbor reported a wind gust of 118 mph (190 km/h), though it could have been caused by a

downdraft In meteorology, an updraft is a small-scale current of rising air, often within a cloud. Overview Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding region, ...

. The storm also dropped moderate rainfall of just over 3 inches (76 mm), resulting in minor flooding of streets. Because the storm developed quickly, wave-induced beach erosion was minor. The strong winds left considerable tree and powerline damage. At the worst of the storm, 23,000 of the island's 30,000 power subscribers were without

electricity Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as describ ...

. Damage to power lines totaled to $385,000 (2001 USD, $468,700 2008 USD). The strong winds also caused considerable damage to vegetation. Three cruise ships weathered the storm at St. George's Harbour, where the powerful winds ripped out a post and snapped a mooring line, leaving a ship drifting in the harbor. One crew member was minorly injured. Over a dozen boats broke free from their moorings, resulting in them running aground or sinking. In all, 87 boats were affected to some degree, with marine damage totaling to about $665,000 (2001 USD, $809,600 2008 USD). The winds also caused minor damage to 175 properties on the island, primarily to houses. Damage to houses amounted to about $425,000 (2001 USD, $517,400 2008 USD). Overall damage was moderate, totaling to about $1.4 million (2001 USD, $1.7 million 2008 USD). No fatalities were reported, though a few storm-related injuries occurred.

Canada

Tropical Storm Karen produced light to moderate winds across Atlantic Canada, peaking at 47 mph (76 km/h) with a gust of 64 mph (103 km/h) in Cape George in

Antigonish County, Nova Scotia , nickname = , settlement_type = County , motto = , image_skyline = Antigonish Harbour Panorama2.jpg , image_caption = , image_flag = , flag_size ...

, along with a 26 mph (42 km/h) report in

Charlottetown, Prince Edward Island Charlottetown is the capital and largest city of the Canadian province of Prince Edward Island, and the county seat of Queens County. Named after Queen Charlotte, Charlottetown was an unincorporated town until it was incorporated as a city in 1 ...

Rainband A rainband is a cloud and precipitation structure associated with an area of rainfall which is significantly elongated. Rainbands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar im ...

s in the storm dropped light rainfall of up to 1.8 inches (46 mm) in

Yarmouth, Nova Scotia Yarmouth is a town in southwestern Nova Scotia, Canada. A port town, industries include fishing, and tourism. It is the terminus of a ferry service to Bar Harbor, Maine, run by Bay Ferries. History Originally inhabited by the Mi'kmaq, the regi ...

and 1.4 inches (35 mm) in

Saint John, New Brunswick Saint John is a seaport city of the Atlantic Ocean located on the Bay of Fundy in the province of New Brunswick, Canada. Saint John is the oldest incorporated city in Canada, established by royal charter on May 18, 1785, during the reign of K ...

, most of which fell in a short amount of time. Skewed to the left side of the transitioning storm, the rainfall was beneficial for the drought-stricken areas of Nova Scotia and New Brunswick. Due to the fast-moving nature of the storm, though, most areas reported only around half an inch of rain. A buoy in

Halifax Harbour Halifax Harbour is a large natural harbour on the Atlantic coast of Nova Scotia, Canada, located in the Halifax Regional Municipality. Halifax largely owes its existence to the harbour, being one of the largest and deepest ice-free natural harbo ...

reported wave heights of up to 16.7 feet (5.1 m), causing breaking waves at docks white caps along the ocean. Damage in Canada was minor due to the storm, limited to an uprooted tree in

New Glasgow, Nova Scotia New Glasgow is a town in Pictou County, in the province of Nova Scotia, Canada. It is situated on the banks of the East River of Pictou, which flows into Pictou Harbour, a sub-basin of the Northumberland Strait. The town's population was 9,075 ...

and several other trees with damaged branches. There were no injuries or fatalities in Canada.

References