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Hurricane Hernan (2002)
Encyclopedia
Hurricane Hernan was the second of three Category 5 hurricanes
during the 2002 Pacific hurricane season
. The twelfth tropical cyclone
, tenth named storm and sixth hurricane of the season, Hernan originated from a tropical wave
that formed in the Atlantic Ocean and crossed to the Pacific Ocean. The wave spawned a low pressure system which organized into a tropical depression on August 30, a tropical storm on August 31 and a hurricane later that day. Hernan rapidly intensified and reached peak intensity as a Category 5 storm on the Saffir-Simpson Hurricane Scale
. Proceeding northwest, it maintained this strength for eight hours, but on September 2 it entered cooler waters and began to weaken. By September 6 it had degenerated into a remnant area of low pressure
.
Hernan was the second most intense hurricane of the season, and it maintained Category 5 status for the second-longest time of the season, behind Hurricane Kenna
. Although Hernan remained far from land, swells of caused minor beach erosion along the coast of Mexico. In addition, an associated remnant plume of moisture generated light shower activity in southern California
as it tracked just offshore.
left the coast of Africa. It traveled westward across the Atlantic Ocean, crossing over Central America and emerging in the eastern Pacific, where it merged with a pre-existing intertropical convergence zone
disturbance. The system gradually developed moderate convection
, and on August 30 it had developed sufficient convection to be designated Tropical Depression 10-E. The depression produced persistent strong thunderstorms, primarily in two areas of deep convection located to the northeast and west of the center of circulation. Although the center was elongated, wind shear
over the system remained light and outflow
was good, which led forecasters to predict modest intensification. On the afternoon of August 30, banding features became evident, and the depression was upgraded to Tropical Storm Hernan with sustained winds of 45 mph (72 km/h). Further organization occurred, and the center of circulation became encircled by convective thunderstorms. On August 31, the storm was upgraded to Hurricane Hernan as it moved northwestward about 400 miles (634 km) southwest of Acapulco.
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Light wind shear and favorable ocean temperatures led to steady intensification of the storm, and satellite images indicated that an eye
had developed late on August 31. Minimum pressure lowered to , and the maximum winds increased to 100 mph, Category 2 on the Saffir-Simpson Hurricane Scale
. The storm quickly reached Category 3, a major hurricane, and soon after, Category 4. As it did so, its eye became ragged, while its lateral movement to the northwest rose to 17 mph around the southern periphery of a strong deep-layer ridge over the United States. By September 1, the hurricane reached its peak intensity of 160 mph (260 km/h) and a minimum pressure of 921 mb (hPa). It had reached Category 5, the second of three such powerful storms that would do so during the season.
By September 2, the storm's convective thunderstorms warmed slightly, indicating weakening to just below Category 5. An eyewall replacement cycle took place, and two eye structures formed as gradual weakening continued. By September 2, the storm was downgraded to Category 3 just before it turned slightly to the west. The storm underwent another eyewall replacement cycle as winds decreased further. As the storm entered cooler waters, winds decreased to 100 mph (160 km/h), below major hurricane intensity. Soon Hernan was downgraded to Category 1, and the eye
became cloud-filled. On September 5, Hernan was downgraded to a tropical storm as winds rapidly weakened to 45 mph (72 km/h) despite developing a new band of convection. That same day, the storm was downgraded to a tropical depression as it began to lose tropical characteristics. Strong wind shear developed, further dissipating the depression. On September 6, the system degenerated into a remnant low-pressure system
which spawned a remnant plume of moisture that meandered off the coast of California, producing light showers.
off the coast of Mexico. Rough surf caused minor impact; in the open waters near the center of Hernan, waves generated by the storm were unofficially estimated to exceed 70 feet (21 meters). However, official buoys reported swells of 57 feet (17 meters). Along the coast of Mexico, waves reached , causing minor beach erosion. A portion of Hernan's remnant moisture off the southern California coast produced light rainfall and slippery roads. Hernan had no known effects on shipping.
When Hernan grew from tropical storm to Category 5, it intensified at a rate of , just under the threshold for "rapid intensification". However, for a 12-hour period from August 31 to September 1, it deepened at , within the range of "explosive deepening" due to favorable conditions including light wind shear and warm water.
Saffir-Simpson Hurricane Scale
The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
during the 2002 Pacific hurricane season
2002 Pacific hurricane season
The 2002 Pacific hurricane season was an event in tropical cyclone meteorology. The most notable storm that year was Hurricane Kenna, which reached Category 5 on the Saffir-Simpson Hurricane Scale. It made landfall near Puerto Vallarta, in the Mexican state of Jalisco, on October 25...
. The twelfth tropical cyclone
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
, tenth named storm and sixth hurricane of the season, Hernan originated from a tropical wave
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 formed in the Atlantic Ocean and crossed to the Pacific Ocean. The wave spawned a low pressure system which organized into a tropical depression on August 30, a tropical storm on August 31 and a hurricane later that day. Hernan rapidly intensified and reached peak intensity as a Category 5 storm on the Saffir-Simpson Hurricane Scale
Saffir-Simpson Hurricane Scale
The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
. Proceeding northwest, it maintained this strength for eight hours, but on September 2 it entered cooler waters and began to weaken. By September 6 it had degenerated into a remnant area of low pressure
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...
.
Hernan was the second most intense hurricane of the season, and it maintained Category 5 status for the second-longest time of the season, behind Hurricane Kenna
Hurricane Kenna
Hurricane Kenna was the second-most intense Pacific hurricane to strike the west coast of Mexico in recorded history. Kenna was the sixteenth tropical depression, thirteenth tropical storm, seventh hurricane, sixth major hurricane, and third Category 5 hurricane of the 2002 Pacific hurricane season...
. Although Hernan remained far from land, swells of caused minor beach erosion along the coast of Mexico. In addition, an associated remnant plume of moisture generated light shower activity in southern California
California
California is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
as it tracked just offshore.
Meteorological history
On August 16, 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...
left the coast of Africa. It traveled westward across the Atlantic Ocean, crossing over Central America and emerging in the eastern Pacific, where it merged with a pre-existing intertropical convergence zone
Intertropical Convergence Zone
The Intertropical Convergence Zone , known by sailors as The Doldrums, is the area encircling the earth near the equator where winds originating in the northern and southern hemispheres come together....
disturbance. The system gradually developed moderate convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
, and on August 30 it had developed sufficient convection to be designated Tropical Depression 10-E. The depression produced persistent strong thunderstorms, primarily in two areas of deep convection located to the northeast and west of the center of circulation. Although the center was elongated, 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...
over the system remained light and 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...
was good, which led forecasters to predict modest intensification. On the afternoon of August 30, banding features became evident, and the depression was upgraded to Tropical Storm Hernan with sustained winds of 45 mph (72 km/h). Further organization occurred, and the center of circulation became encircled by convective thunderstorms. On August 31, the storm was upgraded to Hurricane Hernan as it moved northwestward about 400 miles (634 km) southwest of Acapulco.
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...
had developed late on August 31. Minimum pressure lowered to , and the maximum winds increased to 100 mph, Category 2 on the Saffir-Simpson Hurricane Scale
Saffir-Simpson Hurricane Scale
The Saffir–Simpson Hurricane Scale , or the Saffir–Simpson Hurricane Wind Scale , classifies hurricanes — Western Hemisphere tropical cyclones that exceed the intensities of tropical depressions and tropical storms — into five categories distinguished by the intensities of their sustained winds...
. The storm quickly reached Category 3, a major hurricane, and soon after, Category 4. As it did so, its eye became ragged, while its lateral movement to the northwest rose to 17 mph around the southern periphery of a strong deep-layer ridge over the United States. By September 1, the hurricane reached its peak intensity of 160 mph (260 km/h) and a minimum pressure of 921 mb (hPa). It had reached Category 5, the second of three such powerful storms that would do so during the season.
By September 2, the storm's convective thunderstorms warmed slightly, indicating weakening to just below Category 5. An eyewall replacement cycle took place, and two eye structures formed as gradual weakening continued. By September 2, the storm was downgraded to Category 3 just before it turned slightly to the west. The storm underwent another eyewall replacement cycle as winds decreased further. As the storm entered cooler waters, winds decreased to 100 mph (160 km/h), below major hurricane intensity. Soon Hernan was downgraded to Category 1, and the 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...
became cloud-filled. On September 5, Hernan was downgraded to a tropical storm as winds rapidly weakened to 45 mph (72 km/h) despite developing a new band of convection. That same day, the storm was downgraded to a tropical depression as it began to lose tropical characteristics. Strong wind shear developed, further dissipating the depression. On September 6, the system degenerated into a remnant low-pressure system
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...
which spawned a remnant plume of moisture that meandered off the coast of California, producing light showers.
Impact and intensity
Hurricane Hernan remained far from shore and caused little damage to land. It brought light wind to Socorro IslandSocorro Island
Socorro Island is a small volcanic island in the Revillagigedo Islands, a Mexican possession lying some 600 kilometers off the country's western coast at 18°48'N, 110°59'W. The size is 16.5 by 11.5 km, with an area of 132 km².- Geology :...
off the coast of Mexico. Rough surf caused minor impact; in the open waters near the center of Hernan, waves generated by the storm were unofficially estimated to exceed 70 feet (21 meters). However, official buoys reported swells of 57 feet (17 meters). Along the coast of Mexico, waves reached , causing minor beach erosion. A portion of Hernan's remnant moisture off the southern California coast produced light rainfall and slippery roads. Hernan had no known effects on shipping.
When Hernan grew from tropical storm to Category 5, it intensified at a rate of , just under the threshold for "rapid intensification". However, for a 12-hour period from August 31 to September 1, it deepened at , within the range of "explosive deepening" due to favorable conditions including light wind shear and warm water.
See also
- Other tropical cyclones named Hernan
- List of Category 5 Pacific hurricanes
- List of California hurricanes
