Hurricane Fran (1973)
Encyclopedia
Hurricane Fran, also referred initially as Subtropical storm Bravo, was a long-tracked Category 1 hurricane that caused little damage during its existence in early October 1973. Originating from a tropical wave
that developed off the coast of Hispaniola
on October 1, the precursor to Fran slowly developing during the first week of October. By October 4, a surface low
formed within the system and convective activity
increased. The system was eventually classified as a subtropical depression
on October 8 and was upgraded to Subtropical Storm Bravo shortly thereafter. Bravo became increasingly tropical throughout the day as it intensified. Following a reconnaissance mission into the storm on October 10, it was deemed fully tropical and upgraded to a hurricane, at which time it was renamed Fran.
Hurricane Fran rapidly tracked towards the northeast in response to an area of low pressure within the westerlies
. By October 11, the hurricane attained its peak winds of 80 mph (130 km/h) and its lowest barometric pressure of 978 mbar (hPa; 28.88 inHg) after bypassing the Azores
islands. Situated over exceedingly cold waters, Fran transitioned into an extratropical cyclone
late on October 12 as it neared the French
coastline. Shortly before reaching land, the system was absorbed by a cold front
. Throughout its existence, Fran had little effect on land.
associated with an area of convection north of Hispanola on October 1. The system tracked westward at 15 mph (24.1 km/h) but gained little strength and the National Hurricane Center
(NHC) did not anticipate development of the storm. By October 4, the system interacted with a mid-tropospheric trough near the southeast United States, resulting in the formation of a surface low. Tracking eastward, showers and thunderstorms began to develop around the circulation; however, the structure of the system was not fully tropical. On October 7, ships in the vicinity of the low reported decreasing barometric pressures, indicating a strengthening system. Satellites monitoring the system depicted a disorganized storm with mainly subtropical characteristics
. Late on October 8, the cyclone had become sufficiently organized to be classified a subtropical depression.
Cold air from the remnants of a cold front
became entrained within the circulation; however, the cold air gradually warmed. On October 9, winds increased to gale-force and the depression was upgraded to a subtropical storm, at which time it was given the name Bravo. By October 10, Bravo had intensified substantially, as hurricane hunters recorded hurricane-force winds roughly 15 mi (25 km) from the center of the storm. Following this finding, the National Hurricane Center reclassified the system as a tropical system and renamed it Fran, dropping its previous designation of Bravo. Upon becoming tropical, Fran developed a strong outflow
and several convective feeder bands
. Additionally, the storm had developed a 35 mi (55 km) wide eye
.
Steered generally eastward by a deep surface low in the westerlies
, Fran accelerated towards the Azores Islands. The storm traveled at a rapid pace of 30 to 35 mph (48.3 to 56.3 km/h) but continued to organize. By October 11, the hurricane began to undergo an extratropical transition
as it continued to move unusually fast towards the northeast. Around this time, Fran attained its peak winds of 80 mph (130 km/h). Shortly after bypassing the Azores islands on October 12, the system moved over an area with sea surface temperature
s around 60 °F (15.6 °C), well below what is required for tropical cyclone development
. Later that day, the central pressure of Fran decreased to 978 mbar (hPa; 28.88 inHg), the lowest recorded in relation to the hurricane. Shortly after reaching this intensity, the hurricane transitioned into an extratropical cyclone and quickly merged with a cold front off the coast of France
.
and French
coastlines recorded winds up to 60 mph (95 km/h) as the extratropical remnants of Fran passed through the region.
Tropical wave
Tropical waves, easterly waves, or tropical easterly waves, also known as African easterly waves in the Atlantic region, are a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which move from east to west across the tropics causing areas of...
that developed off the coast of Hispaniola
Hispaniola
Hispaniola is a major island in the Caribbean, containing the two sovereign states of the Dominican Republic and Haiti. The island is located between the islands of Cuba to the west and Puerto Rico to the east, within the hurricane belt...
on October 1, the precursor to Fran slowly developing during the first week of October. By October 4, a surface 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...
formed within the system and convective activity
Atmospheric convection
Atmospheric convection is the result of a parcel-environment instability, or temperature difference, layer in the atmosphere. Different lapse rates within dry and moist air lead to instability. Mixing of air during the day which expands the height of the planetary boundary layer leads to...
increased. The system was eventually classified as a subtropical depression
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 October 8 and was upgraded to Subtropical Storm Bravo shortly thereafter. Bravo became increasingly tropical throughout the day as it intensified. Following a reconnaissance mission into the storm on October 10, it was deemed fully tropical and upgraded to a hurricane, at which time it was renamed Fran.
Hurricane Fran rapidly tracked towards the northeast in response to an area of low pressure within 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...
. By October 11, the hurricane attained its peak winds of 80 mph (130 km/h) and its lowest barometric pressure of 978 mbar (hPa; 28.88 inHg) after bypassing the Azores
Azores
The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...
islands. Situated over exceedingly cold waters, Fran transitioned into an extratropical cyclone
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...
late on October 12 as it neared the French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
coastline. Shortly before reaching land, the system was absorbed by a cold front
Cold 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...
. Throughout its existence, Fran had little effect on land.
Meteorological history
Hurricane Fran originated from a tropical waveTropical wave
Tropical waves, easterly waves, or tropical easterly waves, also known as African easterly waves in the Atlantic region, are a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which move from east to west across the tropics causing areas of...
associated with an area of convection north of Hispanola on October 1. The system tracked westward at 15 mph (24.1 km/h) but gained little strength and 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 anticipate development of the storm. By October 4, the system interacted with a mid-tropospheric trough near the southeast United States, resulting in the formation of a surface low. Tracking eastward, showers and thunderstorms began to develop around the circulation; however, the structure of the system was not fully tropical. On October 7, ships in the vicinity of the low reported decreasing barometric pressures, indicating a strengthening system. Satellites monitoring the system depicted a disorganized storm with mainly subtropical characteristics
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...
. Late on October 8, the cyclone had become sufficiently organized to be classified a subtropical depression.
Cold air from the remnants of a cold front
Cold 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...
became entrained within the circulation; however, the cold air gradually warmed. On October 9, winds increased to gale-force and the depression was upgraded to a subtropical storm, at which time it was given the name Bravo. By October 10, Bravo had intensified substantially, as hurricane hunters recorded hurricane-force winds roughly 15 mi (25 km) from the center of the storm. Following this finding, the National Hurricane Center reclassified the system as a tropical system and renamed it Fran, dropping its previous designation of Bravo. Upon becoming tropical, Fran developed a strong 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...
and several convective feeder bands
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 imagery, this precipitation elongation is referred to as...
. Additionally, the storm had developed a 35 mi (55 km) wide 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...
.
Steered generally eastward by a deep surface low in 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...
, Fran accelerated towards the Azores Islands. The storm traveled at a rapid pace of 30 to 35 mph (48.3 to 56.3 km/h) but continued to organize. By October 11, the hurricane began to undergo an extratropical transition
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...
as it continued to move unusually fast towards the northeast. Around this time, Fran attained its peak winds of 80 mph (130 km/h). Shortly after bypassing the Azores islands on October 12, the system moved over an area with sea surface temperature
Sea surface temperature
Sea surface temperature is the water temperature close to the oceans surface. The exact meaning of surface varies according to the measurement method used, but it is between and below the sea surface. Air masses in the Earth's atmosphere are highly modified by sea surface temperatures within a...
s around 60 °F (15.6 °C), well below what is required for tropical cyclone development
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...
. Later that day, the central pressure of Fran decreased to 978 mbar (hPa; 28.88 inHg), the lowest recorded in relation to the hurricane. Shortly after reaching this intensity, the hurricane transitioned into an extratropical cyclone and quickly merged with a cold front off the coast of France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
.
Preparations and impact
Although Fran passed near the Azores as a hurricane, winds on the islands only reached 45 mph (75 km/h) and no damage was recorded. On October 12, a French ship encountered the storm, recording sustained winds of 40 mph (65 km/h) and an air pressure of 981 mbar (hPa; 28.97 inHg). Ships near the EnglishUnited Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
coastlines recorded winds up to 60 mph (95 km/h) as the extratropical remnants of Fran passed through the region.
See also
- 1973 Atlantic hurricane season1973 Atlantic hurricane seasonThe 1973 Atlantic hurricane season was the first season to use the Saffir-Simpson Hurricane Scale, a scale developed in 1971 by Herbert Saffir and Robert Simpson used for rating the intensity of tropical cyclones. The season produced 24 tropical and subtropical cyclones, of which only 8 reached...
- Other storms named Fran