Typhoon Meranti (2004)
Encyclopedia
Typhoon Meranti was the first of the record nine named storms to develop during August within the 2004 Pacific typhoon season
. Forming from an area of low pressure on August 3, Meranti gradually strengthened. On August 5, the storm underwent a brief period of rapid intensification
, attaining its peak intensity later day. According to the Japan Meteorological Agency
, the storm attained winds of 140 km/h (85 mph 10-minute winds) while the Joint Typhoon Warning Center
reported that the storm attained winds of 165 km/h (105 mph 1-minute winds). The following day, the typhoon quickly weakened to a tropical storm due to unfavorable conditions. By August 9, the system completed an extratropical transition
; the remnants of the storm persisted until August 13, at which time it was absorbed by a large, non-tropical low.
about 475 km (295 mi) south of Wake Island
on August 2. Little deep convection
accompanied the weak system despite being situated within an area of moderate diffluence and weak to moderate wind shear
. Initially, the system was thought to have been much closer to Wake Island; however, following the development of deep convection, the location of the center of circulation
was corrected. Around 0000 UTC
on August 3, the Japan Meteorological Agency
(JMA), the Regional Specialized Meteorological Center
for the western Pacific basin
, designated the system as a tropical depression. Development continued as the depression moved into an area of divergence near a tropical upper-tropospheric trough cell. Several hours after the JMA issued their advisory on the depression, the Joint Typhoon Warning Center
(JTWC) issued a tropical cyclone formation alert
, stating that the system was likely to develop into a tropical storm within 24 hours.
Later on August 3, the JTWC issued their first advisory on the storm, classifying it as Tropical Depression 14W. Located to the west of a mid-level ridge
, the depression was steered towards the north. Early the next day, the JTWC upgraded 14W to a tropical storm; the JMA later upgraded it to a tropical storm around 1200 UTC. At that time, the storm received the name Meranti, a name that was contributed by Cambodia
. Little intensification took place until August 5, at which time convection became increasingly organized and underwent a brief period of rapid intensification
. By 1200 UTC, both the JMA and JTWC upgraded Meranti to a typhoon. Several hours later, the storm reached its peak intensity; the JMA assessed it to have had winds of 140 km/h (85 mph 10-minute winds) while the JTWC assessed it to have attained Category 2 status on the Saffir–Simpson Hurricane Scale with winds of 165 km/h (105 mph).
Upon attaining typhoon status, Meranti turned towards the northeast in response to a strengthening near-equatorial
ridge south of the typhoon. Visible satellite images of the typhoon depicted a small, ragged eye within a well-developed cyclone. Gale-force winds extended 155 km (100 mi) at this time. Well-developed outflow
allowed the storm to maintain its peak intensity for roughly 18 hours before dry air became entrained in the circulation. The combined effects of decreasing sea surface temperature
s and increasing wind shear caused Meranti to quickly weaken. By 0600 UTC on August 6, the eye was no longer visible on satellite imagery and several hours later deep convection rapidly diminished, leading to both agencies downgrading the typhoon to a tropical storm.
Later on August 6, the weakening trend briefly halted as outflow significantly improved due to an area of low pressure north of Meranti. However, wind shear drastically increased, displacing convection to the northwest of the circulation center. By this time, the storm began to undergo an extratropical transition
. Due to the influence of a major shortwave trough approaching from the west, Meranti took a sharp northward turn. The JTWC issued their final advisory on the weakening cyclone around 0600 UTC on August 8. The JMA continued to monitor Meranti as a tropical cyclone until August 9. Shortly after becoming extratropical, the remnants of the storm executed a slow, counter-clockwise loop until August 12. Shortly after crossing the International Date Line
on August 13, the storm was absorbed by a large non-tropical low over the Bering Sea
.
were issued in response to the storm. Although Meranti passed near Wake Island as a tropical depression, no effects were recorded.
2004 Pacific typhoon season
The 2004 Pacific typhoon season has no official bounds; it ran year-round in 2004, but most tropical cyclones tend to form in the northwestern Pacific Ocean between May and November...
. Forming from an area of low pressure on August 3, Meranti gradually strengthened. On August 5, the storm underwent a brief period of 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...
, attaining its peak intensity later day. According to the Japan Meteorological Agency
Japan Meteorological Agency
The or JMA, is the Japanese government's weather service. Charged with gathering and reporting weather data and forecasts in Japan, it is a semi-autonomous part of the Ministry of Land, Infrastructure and Transport...
, the storm attained winds of 140 km/h (85 mph 10-minute winds) while the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...
reported that the storm attained winds of 165 km/h (105 mph 1-minute winds). The following day, the typhoon quickly weakened to a tropical storm due to unfavorable conditions. By August 9, the system completed 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...
; the remnants of the storm persisted until August 13, at which time it was absorbed by a large, non-tropical low.
Meteorological history
Typhoon Meranti originated out of an area of low pressureLow 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...
about 475 km (295 mi) south of Wake Island
Wake Island
Wake Island is a coral atoll having a coastline of in the North Pacific Ocean, located about two-thirds of the way from Honolulu west to Guam east. It is an unorganized, unincorporated territory of the United States, administered by the Office of Insular Affairs, U.S. Department of the Interior...
on August 2. Little deep 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...
accompanied the weak system despite being situated within an area of moderate diffluence and weak to moderate 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...
. Initially, the system was thought to have been much closer to Wake Island; however, following the development of deep convection, the location of 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...
was corrected. Around 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 August 3, the Japan Meteorological Agency
Japan Meteorological Agency
The or JMA, is the Japanese government's weather service. Charged with gathering and reporting weather data and forecasts in Japan, it is a semi-autonomous part of the Ministry of Land, Infrastructure and Transport...
(JMA), the Regional Specialized Meteorological Center
Regional Specialized Meteorological Center
A Regional Specialized Meteorological Centre is responsible for the distribution of information, advisories, and warnings regarding the specific program they have a part of, agreed by consensus at the World Meteorological Organization as part of the World Weather Watch.-Tropical...
for the western Pacific basin
Pacific typhoon
A typhoon is a mature tropical cyclone that develops in the northwestern part of the Pacific Ocean between 180° and 100°E. This region is referred to as the northwest Pacific basin. For organizational purposes, the northern Pacific Ocean is divided into three regions: the eastern , central , and...
, designated the system as a tropical depression. Development continued as the depression moved into an area of divergence near a tropical upper-tropospheric trough cell. Several hours after the JMA issued their advisory on the depression, the Joint Typhoon Warning Center
Joint Typhoon Warning Center
The Joint Typhoon Warning Center is a joint United States Navy – United States Air Force task force located at the Naval Maritime Forecast Center in Pearl Harbor, Hawaii...
(JTWC) issued a tropical cyclone formation alert
Tropical Cyclone Formation Alert
A Tropical Cyclone Formation Alert is a bulletin released by the U.S. Navy-operated Joint Typhoon Warning Center in Honolulu, Hawaii or the Naval Maritime Forecast Center in Norfolk, Virginia, warning of the possibility of a tropical cyclone forming from a tropical disturbance that has been...
, stating that the system was likely to develop into a tropical storm within 24 hours.
Later on August 3, the JTWC issued their first advisory on the storm, classifying it as Tropical Depression 14W. Located to the west of a mid-level ridge
High pressure area
A high-pressure area is a region where the atmospheric pressure at the surface of the planet is greater than its surrounding environment. Winds within high-pressure areas flow outward due to the higher density air near their center and friction with land...
, the depression was steered towards the north. Early the next day, the JTWC upgraded 14W to a tropical storm; the JMA later upgraded it to a tropical storm around 1200 UTC. At that time, the storm received the name Meranti, a name that was contributed by Cambodia
Cambodia
Cambodia , officially known as the Kingdom of Cambodia, is a country located in the southern portion of the Indochina Peninsula in Southeast Asia...
. Little intensification took place until August 5, at which time convection became increasingly organized and underwent a brief period of 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...
. By 1200 UTC, both the JMA and JTWC upgraded Meranti to a typhoon. Several hours later, the storm reached its peak intensity; the JMA assessed it to have had winds of 140 km/h (85 mph 10-minute winds) while the JTWC assessed it to have attained Category 2 status on the Saffir–Simpson Hurricane Scale with winds of 165 km/h (105 mph).
Upon attaining typhoon status, Meranti turned towards the northeast in response to a strengthening near-equatorial
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
ridge south of the typhoon. Visible satellite images of the typhoon depicted a small, ragged eye within a well-developed cyclone. Gale-force winds extended 155 km (100 mi) at this time. Well-developed 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...
allowed the storm to maintain its peak intensity for roughly 18 hours before dry air became entrained in the circulation. The combined effects of decreasing 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 and increasing wind shear caused Meranti to quickly weaken. By 0600 UTC on August 6, the eye was no longer visible on satellite imagery and several hours later deep convection rapidly diminished, leading to both agencies downgrading the typhoon to a tropical storm.
Later on August 6, the weakening trend briefly halted as outflow significantly improved due to an area of low pressure north of Meranti. However, wind shear drastically increased, displacing convection to the northwest of the circulation center. By this time, the storm 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...
. Due to the influence of a major shortwave trough approaching from the west, Meranti took a sharp northward turn. The JTWC issued their final advisory on the weakening cyclone around 0600 UTC on August 8. The JMA continued to monitor Meranti as a tropical cyclone until August 9. Shortly after becoming extratropical, the remnants of the storm executed a slow, counter-clockwise loop until August 12. Shortly after crossing 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...
on August 13, the storm was absorbed by a large non-tropical low over the Bering Sea
Bering Sea
The Bering Sea is a marginal sea of the Pacific Ocean. It comprises a deep water basin, which then rises through a narrow slope into the shallower water above the continental shelves....
.
Impact
As Typhoon Meranti never threatened any land masses, no watches or warningsTropical cyclone warnings and watches
Warnings and watches are two levels of alert issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of tropical storm or hurricane intensity. They are notices to the local population and civil authorities to make appropriate...
were issued in response to the storm. Although Meranti passed near Wake Island as a tropical depression, no effects were recorded.