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Hurricane Gilma (1994)
Encyclopedia
Hurricane Gilma was one the most intense Pacific hurricane
s on record and the second of three Category 5 hurricanes during the active 1994 Pacific hurricane season
. Developing from a westward tracking tropical wave
over the open waters of the eastern Pacific Ocean on July 21, the pre-Gilma tropical depression was initially large and disorganized. Gradual development took place over the following day before rapid intensification
began. By July 23, the storm intensified into a hurricane and later a Category 5 storm on July 24. As Gilma reached this intensity, it crossed into the Central Pacific basin
, the fourth consecutive storm to do so.
The storm peaked early on July 24 with winds of 160 mph (260 km/h) and a barometric pressure estimated at 920 mbar (hPa; 27.17 inHg). The following day, unknown factors caused the storm to suddenly weaken before increasing wind shear
took over. The storm gradually weakened for the duration of its existence, turning slowly to the northwest. Late on July 28, the storm brushed Johnston Atoll
, bringing gusty winds and light rainfall to the region. Gilma persisted until July 31 at which time it was downgraded to a tropical depression and dissipated over open waters.
that moved off the coast of Africa and traversed the Atlantic Ocean during the second week of July 1994. The wave was of little note until it crossed Central America
and entered the Northeastern Pacific hurricane basin
on July 15-16. Convection
began to increase; however, the system remained disorganized. Tracking westward, gradual development took place, leading to the Dvorak classification
being initiated on July 20. Several hours later, the National Hurricane Center
(NHC) designated the system as Tropical Depression Seven-E. A strong ridge
situated north of the depression steered the system steadily westward. This movement would remain the same throughout most of the storm's existence. The depression was initially hard to locate due to its large size.
Following an increase in organization, the depression intensified into a tropical storm early on July 22, at which time it was named
Gilma. Deep convection developed around the center of circulation
throughout the day and banding features
became apparent on the west and south sides of the storm. Only 24 hours after becoming a tropical storm, Gilma quickly intensified into a hurricane. Low wind shear
and warm sea surface temperature
s, recorded up to 29 °C (84.2 °F) by a ship near the hurricane, allowed the storm to undergo rapid intensification
. This rate of intensification continued throughout most of July 23, resulting in the system attaining Category 4 status on the Saffir–Simpson Hurricane Scale. By this time, a small, well-defined eye
had developed within the center of the hurricane surrounded by very deep convection.
On July 24, the storm crossed 140°W
, entering the Central Pacific Hurricane Center
's (CPHC) area of responsibility
. Upon entering the region, Gilma became the fourth consecutive cyclone to move into the CPHC region. Several hours later, Gilma attained its peak intensity as a Category 5 hurricane with winds of 160 mph (260 km/h) and a barometric pressure estimated at 920 mbar (hPa; 27.17 inHg). After maintaining this intensity for roughly 12 hours, the storm abruptly weakened. Within a few hours, maximum winds decreased by 45 mph (75 km/h) to 115 mph (185 km/h), a low-end Category 3 hurricane. The reason for the sudden weakening is unknown; although the tropical upper tropospheric trough
originally located over the storm, providing it with a favorable anticyclonic flow
, shifted westward to the International Date Line
. Additionally, the storm's eye became obscured by cirrus cloud
s.
After maintaining Category 3 intensity for 24 hours, the combination of increasing wind shear and degrading outflow
, Gilma resumed its weakening trend. Late on July 27, the hurricane weakened to a tropical storm as winds fell below the 74 mph (119.1 km/h) threshold. Although weakening, CPHC forecaster Sasaki noted that the storm may have re-intensified slightly shortly after being downgraded. The following morning, the center of Gilma became devoid of convection, exposing the low-level circulation. By this time, the weakening storm began an west-northwesterly track, eventually taking the storm within 100 mi (160.9 km) of Johnston Atoll
late on July 28. Gradual weakening continued to take place throughout the rest of the storm's existence, leading to its downgrade to a tropical depression on July 30. Several hours after being declared a tropical depression, the storm dissipated early on July 31 over open waters south of Midway Atoll
.
. The island received light rain, wind gusts to near gale force, and some surf. No loss of life or damage was reported. Gilma's name was not retired after the 1994 season, and it was used again in the 2000
and 2006 seasons
. However, in 2007, the Central Pacific Hurricane Center requested that the name Gilma, along with 14 other names, be retired as they have become memorable due to the threat of damage. That proposal was not accepted and the name "Gilma" remains on the list for 2012.
Pacific hurricane
A Pacific hurricane or tropical storm is a tropical cyclone that develops in the northeastern part of the Pacific Ocean. For organizational purposes, the northern Pacific Ocean is divided into three regions: the eastern, , central , and western...
s on record and the second of three Category 5 hurricanes during the active 1994 Pacific hurricane season
1994 Pacific hurricane season
The 1994 Pacific hurricane season officially started on May 15, 1994 in the eastern Pacific, and on June 1, 1994 in the central Pacific, and lasted until November 30, 1994. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean...
. Developing from a westward tracking 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...
over the open waters of the eastern Pacific Ocean on July 21, the pre-Gilma tropical depression was initially large and disorganized. Gradual development took place over the following day before rapid intensification
Rapid deepening
Rapid deepening, also known as rapid intensification, is a meteorological condition that occurs when the minimum sea-level atmospheric pressure of a tropical cyclone decreases drastically in a short period of time. The National Weather Service describes rapid deepening as a decrease of...
began. By July 23, the storm intensified into a hurricane and later a Category 5 storm on July 24. As Gilma reached this intensity, it crossed into the Central Pacific basin
Central Pacific Hurricane Center
The Central Pacific Hurricane Center of the United States National Weather Service is the official body responsible for tracking and issuing tropical cyclone warnings, watches, advisories, discussions, and statements for the Central North Pacific Basin...
, the fourth consecutive storm to do so.
The storm peaked early on July 24 with winds of 160 mph (260 km/h) and a barometric pressure estimated at 920 mbar (hPa; 27.17 inHg). The following day, unknown factors caused the storm to suddenly weaken before increasing 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...
took over. The storm gradually weakened for the duration of its existence, turning slowly to the northwest. Late on July 28, the storm brushed Johnston Atoll
Johnston Atoll
Johnston Atoll is a atoll in the North Pacific Ocean about west of Hawaii. There are four islands located on the coral reef platform, two natural islands, Johnston Island and Sand Island, which have been expanded by coral dredging, as well as North Island and East Island , an additional two...
, bringing gusty winds and light rainfall to the region. Gilma persisted until July 31 at which time it was downgraded to a tropical depression and dissipated over open waters.
Meteorological history
Hurricane Gilma 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...
that moved off the coast of Africa and traversed the Atlantic Ocean during the second week of July 1994. The wave was of little note until it crossed Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
and entered the Northeastern Pacific hurricane basin
Pacific hurricane
A Pacific hurricane or tropical storm is a tropical cyclone that develops in the northeastern part of the Pacific Ocean. For organizational purposes, the northern Pacific Ocean is divided into three regions: the eastern, , central , and western...
on July 15-16. Convection
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...
began to increase; however, the system remained disorganized. Tracking westward, gradual development took place, leading to the Dvorak classification
Dvorak technique
The Dvorak technique is a widely used system to subjectively estimate tropical cyclone intensity based solely on visible and infrared satellite images. Several agencies issue Dvorak intensity numbers for cyclones of sufficient intensity...
being initiated on July 20. Several hours later, 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) designated the system as Tropical Depression Seven-E. A strong ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
situated north of the depression steered the system steadily westward. This movement would remain the same throughout most of the storm's existence. The depression was initially hard to locate due to its large size.
Following an increase in organization, the depression intensified into a tropical storm early on July 22, at which time it was named
Tropical cyclone naming
Tropical cyclones have officially been named since 1945 and are named for a variety of reasons, which include to facilitate communications between forecasters and the public when forecasts, watches, and warnings are issued. Names also reduce confusion about what storm is being described, as more...
Gilma. Deep convection developed around the center of circulation
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...
throughout the day and banding features
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...
became apparent on the west and south sides of the storm. Only 24 hours after becoming a tropical storm, Gilma quickly intensified into a hurricane. Low 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...
and warm 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, recorded up to 29 °C (84.2 °F) by a ship near the hurricane, allowed the storm to undergo rapid intensification
Rapid deepening
Rapid deepening, also known as rapid intensification, is a meteorological condition that occurs when the minimum sea-level atmospheric pressure of a tropical cyclone decreases drastically in a short period of time. The National Weather Service describes rapid deepening as a decrease of...
. This rate of intensification continued throughout most of July 23, resulting in the system attaining Category 4 status on the Saffir–Simpson Hurricane Scale. By this time, a small, well-defined 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...
had developed within the center of the hurricane surrounded by very deep convection.
On July 24, the storm crossed 140°W
140th meridian west
The meridian 140° west of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, North America, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole....
, entering the Central Pacific Hurricane Center
Central Pacific Hurricane Center
The Central Pacific Hurricane Center of the United States National Weather Service is the official body responsible for tracking and issuing tropical cyclone warnings, watches, advisories, discussions, and statements for the Central North Pacific Basin...
's (CPHC) area of responsibility
Area of responsibility
Area Of Responsibility is a pre-defined geographic region assigned to a Combatant commanders of the Unified Command Plan , that are used to define an area with specific geographic boundaries where they have the authority to plan and conduct operations; for which a force, or component commander...
. Upon entering the region, Gilma became the fourth consecutive cyclone to move into the CPHC region. Several hours later, Gilma attained its peak intensity as a Category 5 hurricane with winds of 160 mph (260 km/h) and a barometric pressure estimated at 920 mbar (hPa; 27.17 inHg). After maintaining this intensity for roughly 12 hours, the storm abruptly weakened. Within a few hours, maximum winds decreased by 45 mph (75 km/h) to 115 mph (185 km/h), a low-end Category 3 hurricane. The reason for the sudden weakening is unknown; although the tropical upper tropospheric trough
Tropical Upper Tropospheric Trough
A tropical upper tropospheric trough , also known as the mid-oceanic trough, is a trough situated in upper-level tropics. Its formation is usually caused by the intrusion of energy and wind from the mid-latitudes into the tropics. It can also develop from the inverted trough adjacent to an upper...
originally located over the storm, providing it with a favorable anticyclonic flow
Anticyclone
An anticyclone is a weather phenomenon defined by the United States' National Weather Service's glossary as "[a] large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere"...
, shifted westward to the International Date Line
International Date Line
The International Date Line is a generally north-south imaginary line on the surface of the Earth, passing through the middle of the Pacific Ocean, that designates the place where each calendar day begins...
. Additionally, the storm's eye became obscured by cirrus cloud
Cirrus cloud
Cirrus clouds are atmospheric clouds generally characterized by thin, wispy strands, giving them their name from the Latin word cirrus meaning a ringlet or curling lock of hair...
s.
After maintaining Category 3 intensity for 24 hours, the combination of increasing wind shear and degrading 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...
, Gilma resumed its weakening trend. Late on July 27, the hurricane weakened to a tropical storm as winds fell below the 74 mph (119.1 km/h) threshold. Although weakening, CPHC forecaster Sasaki noted that the storm may have re-intensified slightly shortly after being downgraded. The following morning, the center of Gilma became devoid of convection, exposing the low-level circulation. By this time, the weakening storm began an west-northwesterly track, eventually taking the storm within 100 mi (160.9 km) of Johnston Atoll
Johnston Atoll
Johnston Atoll is a atoll in the North Pacific Ocean about west of Hawaii. There are four islands located on the coral reef platform, two natural islands, Johnston Island and Sand Island, which have been expanded by coral dredging, as well as North Island and East Island , an additional two...
late on July 28. Gradual weakening continued to take place throughout the rest of the storm's existence, leading to its downgrade to a tropical depression on July 30. Several hours after being declared a tropical depression, the storm dissipated early on July 31 over open waters south of Midway Atoll
Midway Atoll
Midway Atoll is a atoll in the North Pacific Ocean, near the northwestern end of the Hawaiian archipelago, about one-third of the way between Honolulu, Hawaii, and Tokyo, Japan. Unique among the Hawaiian islands, Midway observes UTC-11 , eleven hours behind Coordinated Universal Time and one hour...
.
Impact
The hurricane's only impact was on Johnston AtollJohnston Atoll
Johnston Atoll is a atoll in the North Pacific Ocean about west of Hawaii. There are four islands located on the coral reef platform, two natural islands, Johnston Island and Sand Island, which have been expanded by coral dredging, as well as North Island and East Island , an additional two...
. The island received light rain, wind gusts to near gale force, and some surf. No loss of life or damage was reported. Gilma's name was not retired after the 1994 season, and it was used again in the 2000
2000 Pacific hurricane season
The 2000 Pacific hurricane season was an event in tropical cyclone meteorology. There were few notable storms this year. Tropical Storms Miriam, Norman, and Rosa all made landfall in Mexico with minimal impact. Hurricane Daniel briefly threatened the U.S. state of Hawaii while weakening...
and 2006 seasons
2006 Pacific hurricane season
The 2006 Pacific hurricane season was the most active Pacific hurricane season since 2000 producing 19 tropical storms or hurricanes. Eighteen developed within the National Hurricane Center area of warning responsibility, which is east of 140ºW, and one storm formed between 140ºW and the...
. However, in 2007, the Central Pacific Hurricane Center requested that the name Gilma, along with 14 other names, be retired as they have become memorable due to the threat of damage. That proposal was not accepted and the name "Gilma" remains on the list for 2012.
See also
- List of Category 5 Pacific hurricanes
- 1994 Pacific hurricane season1994 Pacific hurricane seasonThe 1994 Pacific hurricane season officially started on May 15, 1994 in the eastern Pacific, and on June 1, 1994 in the central Pacific, and lasted until November 30, 1994. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean...
- Hurricane Emilia (1994)Hurricane Emilia (1994)Hurricane Emilia was the fifth tropical cyclone, second Pacific hurricane, and the first major hurricane of the 1994 Pacific hurricane season. It was the third most intense tropical cyclone in the central Pacific Ocean, attaining a minimum central pressure of 926 mbar on July 19—only Gilma...
– a similar hurricane that preceded Gilma