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Hurricane Olga (2001)
Encyclopedia
Hurricane Olga was a late season Category 1 Atlantic hurricane
that formed during the 2001 Atlantic hurricane season
. The fifteenth named storm, ninth and final hurricane of the 2001 season, Olga formed as a subtropical cyclone
on November 24. After acquiring tropical characteristics later that day, Olga meandered westward, and eventually reached hurricane status on November 26. Olga’s winds peaked at 90 mph (150 km/h) before the storm turned southwestward and weakening back into a tropical storm. On November 30 it deteriorated further to a tropical depression, although it re-intensified two days later to tropical storm intensity. Olga then dissipated as a tropical cyclone on December 4 east of the Bahamas. Its damaging effects were limited to ships at sea. The cyclone's remnants produced heavy rainfall across the Bahamas and Florida
. It was a relatively rare storm to exist in December, which is outside of the normal Atlantic hurricane season.
and a small weather disturbance in the north Atlantic Ocean
, producing an extratropical
low
east of Bermuda
on November 22; fives other tropical cyclones and gales formed earlier in the season in the same manner. The low gradually intensified, developing an area of convection east of the center and producing a large area of gale force winds. By 0000 UTC
on November 24, the system organized enough to be classified as Subtropical Storm Two, while located about 900 mi (1450 km) east-southeast of Bermuda. Subsequently, the convection markedly increased and became more concentrated, with hints of an eye
feature. Within 12 hours of becoming a subtropical, it is estimated the cyclone transitioned
into Tropical Storm Olga; however, it was not purely tropical, due to being positioned beneath an upper-level low. Operationally, the National Hurricane Center
(NHC) did not initiate advisories until nine hours later, referring it as Subtropical Storm Two for two more days.
When advisories first began on Olga, forecasters were uncertain how long the storm would persist, due to the storm's presence within a much larger storm; one hurricane model anticipated an increase in wind shear
within 24 hours, which would likely cause quick dissipation. However, the NHC accurately forecast the storm to remain a cyclone for several days. Olga initially tracked northeastward, followed by a turn to the west due to a building ridge
to its north. On November 25, the storm began acquiring more characteristics of a tropical storm, such as detaching from the larger storm and developing more distinct convective rainbands. This was due to decreasing wind shear and continued atmospheric instability, although only marginally warm sea surface temperatures. After turning to the southwest, Olga resumed a northwest motion, and at 1200 UTC on November 26 intensified into a hurricane. By that time, an eye had developed in the center, and the previously large wind field had contracted. Upon attaining hurricane status, Olga was tracking northwestward due to an approaching trough
. The eye steadily became better defined as outflow
increased, and on November 27 Olga attained peak winds of 90 mph (150 km/h), along with a minimum pressure
of 973 mbar
(28.73 inHg
). While at peak intensity, the hurricane executed a double loop about 455 mi (730 km) east of Bermuda, due to interaction with a larger cyclonic circulation that was isolated from the westerlies
.
On November 28 after finishing the second loop, Olga turned to the southwest due to a building ridge to its northwest. Around the same time, it began a steady weakening trend, due to strong wind shear displacing the convection. The eye became poorly defined as the center became exposed, and on November 29 Olga weakened to tropical storm status. With the thunderstorms rapidly diminishing, the storm weakened quickly, and Olga deteriorated further to a tropical depression on November 30. Forecasters anticipated continued weakening until dissipation, although the cyclone was expected to move over an area of more favorable conditions, including warmer waters and lighter shear. Still existing as a tropical cyclone on December 1, Olga extended the hurricane season beyond its typical boundaries. It continued producing a small area of deep convection, prompting one forecaster to note that "Olga is stubbornly holding on to tropical cyclone status... for now." After reaching a position about 240 mi (385 km) northeast of the Turks and Caicos Islands
, the depression turned toward the north after a trough created a weakness in the ridge. After an decrease in wind shear, deep convection redeveloped over the center, and Olga re-intensified into a tropical storm on December 2.
After becoming a tropical storm again, the thunderstorms organized into a rainband about 100 mi (160 km) away from the center, characteristics more typical of a subtropical cyclone. By late on December 2, the structure resembled that of a hurricane with an eye in the center, and although convection was weak, Olga was able to intensify further to winds of 45 mph (72.4 km/h). At the time, there was uncertainty whether the storm would strengthen further, possibly to near hurricane status, or rapidly weaken. Ultimately, an approaching trough caused weakening by increasing wind shear, while also forcing the storm eastward. On December 4, Olga again weakened to a tropical depression as it lost most of its convection. Later that day, the circulation turned to the southeast as a ridge built to its north, and Olga degenerated into a remnant low pressure area, about 690 mi (1,110.4 km) east of Nassau, Bahamas
. The remnant circulation turned to the south and west, completing a loop and later moving through the Bahamas before dissipating along the north coast of Cuba
on December 7.
In Bermuda, the Bermuda Weather Service
issued gale warnings and local marine warnings for boats and other small water craft. The approach of Olga also forced cancellation of the World Yacht regatta, but there was little damage on the island. Olga brought winds of 35-45 mph (56–72 km/h) and waves 15–22 ft (3.7-6.7 m) to the island for several days, but there were no reports of any damage. The hurricane also brought rough seas to the East Coast of the United States
, the Bahamas, and as far south and east as the Lesser Antilles
. A buoy near Guadeloupe
reported 12 ft (3.7 m) waves. High waves in Florida eroded beaches, threatening the foundations of two homes in Flagler County
. The remnants of Olga later produced heavy rainfall across the Bahamas, Cuba and south Florida.
Atlantic hurricane
North Atlantic tropical cyclones usually form in the northern hemisphere summer or fall. Tropical cyclones can be categorized by intensity. Tropical storms have one-minute maximum sustained winds of at least 39 mph , while hurricanes have one-minute maximum sustained exceeding 74 mph...
that formed during the 2001 Atlantic hurricane season
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, 2001, dates which by convention limit the period of each...
. The fifteenth named storm, ninth and final hurricane of the 2001 season, Olga formed as a subtropical cyclone
Subtropical cyclone
A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone. As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical or extratropical cyclones. They were officially recognized by the National...
on November 24. After acquiring tropical characteristics later that day, Olga meandered westward, and eventually reached hurricane status on November 26. Olga’s winds peaked at 90 mph (150 km/h) before the storm turned southwestward and weakening back into a tropical storm. On November 30 it deteriorated further to a tropical depression, although it re-intensified two days later to tropical storm intensity. Olga then dissipated as a tropical cyclone on December 4 east of the Bahamas. Its damaging effects were limited to ships at sea. The cyclone's remnants produced heavy rainfall across the Bahamas and Florida
Florida
Florida is a state in the southeastern United States, located on the nation's Atlantic and Gulf coasts. It is bordered to the west by the Gulf of Mexico, to the north by Alabama and Georgia and to the east by the Atlantic Ocean. With a population of 18,801,310 as measured by the 2010 census, it...
. It was a relatively rare storm to exist in December, which is outside of the normal Atlantic hurricane season.
Meteorological history
The origins of Hurricane Olga were from the interaction of a cold frontCold front
A cold front is defined as the leading edge of a cooler mass of air, replacing a warmer mass of air.-Development of cold front:The cooler and denser air wedges under the less-dense warmer air, lifting it...
and a small weather disturbance in the north Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, producing an extratropical
Extratropical cyclone
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...
low
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
east of Bermuda
Bermuda
Bermuda is a British overseas territory in the North Atlantic Ocean. Located off the east coast of the United States, its nearest landmass is Cape Hatteras, North Carolina, about to the west-northwest. It is about south of Halifax, Nova Scotia, Canada, and northeast of Miami, Florida...
on November 22; fives other tropical cyclones and gales formed earlier in the season in the same manner. The low gradually intensified, developing an area of convection east of the center and producing a large area of gale force winds. By 0000 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
on November 24, the system organized enough to be classified as Subtropical Storm Two, while located about 900 mi (1450 km) east-southeast of Bermuda. Subsequently, the convection markedly increased and became more concentrated, with hints of an eye
Eye (cyclone)
The eye is a region of mostly calm weather found at the center of strong tropical cyclones. The eye of a storm is a roughly circular area and typically 30–65 km in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the second most severe weather of a cyclone...
feature. Within 12 hours of becoming a subtropical, it is estimated the cyclone transitioned
Tropical cyclogenesis
Tropical cyclogenesis is the term that describes the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs...
into Tropical Storm Olga; however, it was not purely tropical, due to being positioned beneath an upper-level low. Operationally, the National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
(NHC) did not initiate advisories until nine hours later, referring it as Subtropical Storm Two for two more days.
When advisories first began on Olga, forecasters were uncertain how long the storm would persist, due to the storm's presence within a much larger storm; one hurricane model anticipated an increase in wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
within 24 hours, which would likely cause quick dissipation. However, the NHC accurately forecast the storm to remain a cyclone for several days. Olga initially tracked northeastward, followed by a turn to the west due to a building ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
to its north. On November 25, the storm began acquiring more characteristics of a tropical storm, such as detaching from the larger storm and developing more distinct convective rainbands. This was due to decreasing wind shear and continued atmospheric instability, although only marginally warm sea surface temperatures. After turning to the southwest, Olga resumed a northwest motion, and at 1200 UTC on November 26 intensified into a hurricane. By that time, an eye had developed in the center, and the previously large wind field had contracted. Upon attaining hurricane status, Olga was tracking northwestward due to an approaching trough
Trough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
. The eye steadily became better defined as outflow
Outflow (meteorology)
Outflow, in meteorology, is air that flows outwards from a storm system. It is associated with ridging, or anticyclonic flow. In the low levels of the troposphere, outflow radiates from thunderstorms in the form of a wedge of rain-cooled air, which is visible as a thin rope-like cloud on weather...
increased, and on November 27 Olga attained peak winds of 90 mph (150 km/h), along with a minimum pressure
Atmospheric pressure
Atmospheric pressure is the force per unit area exerted into a surface by the weight of air above that surface in the atmosphere of Earth . In most circumstances atmospheric pressure is closely approximated by the hydrostatic pressure caused by the weight of air above the measurement point...
of 973 mbar
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...
(28.73 inHg
Inch of mercury
Inches of mercury, ' is a unit of measurement for pressure. It is still widely used for barometric pressure in weather reports, refrigeration and aviation in the United States, but is seldom used elsewhere....
). While at peak intensity, the hurricane executed a double loop about 455 mi (730 km) east of Bermuda, due to interaction with a larger cyclonic circulation that was isolated from the westerlies
Westerlies
The Westerlies, anti-trades, or Prevailing Westerlies, are the prevailing winds in the middle latitudes between 30 and 60 degrees latitude, blowing from the high pressure area in the horse latitudes towards the poles. These prevailing winds blow from the west to the east, and steer extratropical...
.
On November 28 after finishing the second loop, Olga turned to the southwest due to a building ridge to its northwest. Around the same time, it began a steady weakening trend, due to strong wind shear displacing the convection. The eye became poorly defined as the center became exposed, and on November 29 Olga weakened to tropical storm status. With the thunderstorms rapidly diminishing, the storm weakened quickly, and Olga deteriorated further to a tropical depression on November 30. Forecasters anticipated continued weakening until dissipation, although the cyclone was expected to move over an area of more favorable conditions, including warmer waters and lighter shear. Still existing as a tropical cyclone on December 1, Olga extended the hurricane season beyond its typical boundaries. It continued producing a small area of deep convection, prompting one forecaster to note that "Olga is stubbornly holding on to tropical cyclone status... for now." After reaching a position about 240 mi (385 km) northeast of the Turks and Caicos Islands
Turks and Caicos Islands
The Turks and Caicos Islands are a British Overseas Territory and overseas territory of the European Union consisting of two groups of tropical islands in the Caribbean, the larger Caicos Islands and the smaller Turks Islands, known for tourism and as an offshore financial centre.The Turks and...
, the depression turned toward the north after a trough created a weakness in the ridge. After an decrease in wind shear, deep convection redeveloped over the center, and Olga re-intensified into a tropical storm on December 2.
After becoming a tropical storm again, the thunderstorms organized into a rainband about 100 mi (160 km) away from the center, characteristics more typical of a subtropical cyclone. By late on December 2, the structure resembled that of a hurricane with an eye in the center, and although convection was weak, Olga was able to intensify further to winds of 45 mph (72.4 km/h). At the time, there was uncertainty whether the storm would strengthen further, possibly to near hurricane status, or rapidly weaken. Ultimately, an approaching trough caused weakening by increasing wind shear, while also forcing the storm eastward. On December 4, Olga again weakened to a tropical depression as it lost most of its convection. Later that day, the circulation turned to the southeast as a ridge built to its north, and Olga degenerated into a remnant low pressure area, about 690 mi (1,110.4 km) east of Nassau, Bahamas
Nassau, Bahamas
Nassau is the capital, largest city, and commercial centre of the Commonwealth of the Bahamas. The city has a population of 248,948 , 70 percent of the entire population of The Bahamas...
. The remnant circulation turned to the south and west, completing a loop and later moving through the Bahamas before dissipating along the north coast of Cuba
Cuba
The Republic of Cuba is an island nation in the Caribbean. The nation of Cuba consists of the main island of Cuba, the Isla de la Juventud, and several archipelagos. Havana is the largest city in Cuba and the country's capital. Santiago de Cuba is the second largest city...
on December 7.
Preparations and impact
Forecasters at the National Hurricane Center began issuing advisories on Olga on November 24 anticipating that the storm would threaten shipping lanes in the Atlantic. Several ships and boats in the path of Olga reported seas of 12 ft (3.7 m) or higher. One boat, the Manana Tres, reported a barometric pressure of 989 millibars (29.2 inHg) and sustained structural damage.In Bermuda, the Bermuda Weather Service
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 Department of Airport Operations, Ministry of...
issued gale warnings and local marine warnings for boats and other small water craft. The approach of Olga also forced cancellation of the World Yacht regatta, but there was little damage on the island. Olga brought winds of 35-45 mph (56–72 km/h) and waves 15–22 ft (3.7-6.7 m) to the island for several days, but there were no reports of any damage. The hurricane also brought rough seas to the East Coast of the United States
East Coast of the United States
The East Coast of the United States, also known as the Eastern Seaboard, refers to the easternmost coastal states in the United States, which touch the Atlantic Ocean and stretch up to Canada. The term includes the U.S...
, the Bahamas, and as far south and east as the Lesser Antilles
Lesser Antilles
The Lesser Antilles are a long, partly volcanic island arc in the Western Hemisphere. Most of its islands form the eastern boundary of the Caribbean Sea with the Atlantic Ocean, with the remainder located in the southern Caribbean just north of South America...
. A buoy near Guadeloupe
Guadeloupe
Guadeloupe is an archipelago located in the Leeward Islands, in the Lesser Antilles, with a land area of 1,628 square kilometres and a population of 400,000. It is the first overseas region of France, consisting of a single overseas department. As with the other overseas departments, Guadeloupe...
reported 12 ft (3.7 m) waves. High waves in Florida eroded beaches, threatening the foundations of two homes in Flagler County
Flagler County, Florida
Flagler County was created in 1917 from portions of Saint Johns and Volusia counties. It was named for Henry Morrison Flagler, a famous railroad builder who built the Florida East Coast Railway. Bunnell is the county seat of Flagler County....
. The remnants of Olga later produced heavy rainfall across the Bahamas, Cuba and south Florida.