Hurricane Hilary (2011)
Encyclopedia
Hurricane Hilary was a very powerful and intense hurricane that developed during the 2011 Pacific hurricane season
. The fourth Category 4
and major hurricane, seventh hurricane, and eighth tropical storm of the season, Hilary developed from an area of low pressure off the Pacific coast of Central America
in mid-September. Organizing quickly, the system became a tropical depression on September 21, after gaining enough organization to be declared as such. While moving towards the west-northwest, the depression continued to gather strength, and was subsequently upgraded to a tropical storm just several hours later. On September 21, Hilary was declared as a Category 1 hurricane, while located close to the Mexican coastline, where the storm brought heavy rainfall and flooding. Undergoing rapid intensification
, Hilary strengthened into a Category 4 hurricane on September 22, recognized with a distinct eye
feature. Beginning to enter cooler Ocean temperatures, Hilary began to weaken by September 25, but briefly restrengthened into a Category 4 the following day. Atmospheric conditions became increasingly unfavorable late on September 26, and the system began to weaken. During the afternoon hours of September 30, Hilary became a remnant low, while located several hundred miles away from any landmasses.
associated with a broad area of low pressure was observed a couple of hundred miles south-southeast of the Gulf of Tehuantepec
as it moved west
ward. The following day, the area of disturbed weather began to become better organized, and the National Hurricane Center
(NHC) upgraded its chances of tropical cyclone development to the "Medium" category. Moving towards the west-northwest, the area of disturbed weather was upgraded into a tropical depression during the morning hours of September 21, after radar
data showed that the low pressure area had gained enough structure to be declared as such. Due to a favorable upper regime characterized by low wind shear
and a moist environment, the National Hurricane Center predicted intensification into a hurricane within two days. Later on September 21, despite the fact that rainbands
on the western semicircle of the depression became less defined, the depression acquired gale
-force winds, and was subsequently upgraded into a tropical storm, earning the name Hilary. That afternoon, the Government of Mexico issued a tropical storm watch for parts of the Mexican coastline, indicating that rainfall totals of 3-5 inches, with isolated 10 inch amounts, were possible.
On September 22, while quickly strengthening, Hilary was upgraded to a Category 1 hurricane on the Saffir-Simpson hurricane scale
. It was noted by the National Hurricane Center that strengthening into a major hurricane, defined by a hurricane with winds that exceed 111 miles per hour (178.6 km/h), was likely over the coming days. Just several hours later, Hilary was recorded as a rapidly strengthening Category 2 hurricane located in close proximity of the Mexican coastline. At 00:00 UTC September 23 (8:00 p.m. AST
September 22), Hilary was upgraded into a major hurricane, the fourth of the season. Continuing to rapidly strengthen, Hilary became a Category 4 hurricane just a few hours later after becoming a Category 3, and reached a peak intensity of 145 mph (235 km/h) at 0600 UTC September 23 (11 p.m. AST September 22). However, the storm began to enter an area of higher wind shear and cooler ocean temperatures on September 24, and Hilary began to weaken. The hurricane weakened back down to a Category 3 hurricane early on September 25, but was later upgraded briefly to a Category 4 again the following afternoon. Several hours later, the storm was once again downgraded into a Category 3 hurricane, and during the afternoon hours of September 27, Hilary was further downgraded into a Category 2 hurricane. Early the following morning, Hilary weakened into a Category 1 hurricane, and weakened into a tropical storm on September 28. Losing a lot of its convection on September 30, the National Hurricane Center noted that Hilary had weakened into a tropical depression. Several hours later, after sustaining no deep convection atop its centre, Hilary was declared a remnant low, located several hundred miles away from any landmasses. But over the next few days, Hilary's remnants continued to move northwestward, as a convectionless vortex. By late on October 2, the convectionless swirl had dissipated over Southern California
.
noted the possibility of up to 10 in (254 mm) of rain in the high-terrain of Guerrero
and Oaxaca
, and large swell
s were expected to impact coastal areas. Tropical cyclone watches and warnings were therefore issued for portions of the Pacific coast of Mexico. A red emergency alert was additionally in place for the region; officials urged residents to be prepared to evacuate, and tourists were advised to stay indoors. Due to rough surf, small craft advisories were put in effect, and swimmers were advised to take extreme caution. The port of Acapulco
was closed for small vessels, and a moderate to high alert for strong winds and rain was noted.
The storm's outer bands
produced torrential rains over Chiapas
and Tabasco
, with 24-hour accumulations of up to 8.58 in (217.9 mm) in Tabasco. Also in the state, four rivers overflowed their banks; one river received 51 in (1,295.4 mm) of excess water in a single day. Low-lying areas, such as grassland
s and pastures, experienced major flooding, prompting farmers to evacuate their livestock. In Villahermosa
, the downpours resulted in the collapse of water drains, flooding many streets and stranding cars. Across Guerrero
, three people were initially reported missing, but all three were later found. Twenty-thousand residents were advised to evacuated due to rising floodwaters. Offshore Colima
, large waves of 9 ft (2.7 m) to 15 ft (4.6 m) high were recorded.
2011 Pacific hurricane season
The 2011 Pacific hurricane season is an ongoing, annual cycle of tropical cyclone formation. The season officially started on May 15, 2011, for the eastern Pacific, and started on June 1, 2011, for the central Pacific, both of which ended on November 30, 2011. These dates conventionally...
. The fourth Category 4
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...
and major hurricane, seventh hurricane, and eighth tropical storm of the season, Hilary developed from an area of low pressure off the Pacific coast of 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...
in mid-September. Organizing quickly, the system became a tropical depression on September 21, after gaining enough organization to be declared as such. While moving towards the west-northwest, the depression continued to gather strength, and was subsequently upgraded to a tropical storm just several hours later. On September 21, Hilary was declared as a Category 1 hurricane, while located close to the Mexican coastline, where the storm brought heavy rainfall and flooding. Undergoing 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...
, Hilary strengthened into a Category 4 hurricane on September 22, recognized with a distinct 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. Beginning to enter cooler Ocean temperatures, Hilary began to weaken by September 25, but briefly restrengthened into a Category 4 the following day. Atmospheric conditions became increasingly unfavorable late on September 26, and the system began to weaken. During the afternoon hours of September 30, Hilary became a remnant low, while located several hundred miles away from any landmasses.
Meteorological history
During the nighttime hours of September 18, an area of showers and thunderstormsAtmospheric 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...
associated with a broad area of low pressure was observed a couple of hundred miles south-southeast of the Gulf of Tehuantepec
Gulf of Tehuantepec
Gulf of Tehuantepec is a large body of water on the Pacific coast of the Isthmus of Tehuantepec, southeastern Mexico, at . Most of the hurricanes that form in the Eastern Pacific organize in or near this body of water...
as it moved west
West
West is a noun, adjective, or adverb indicating direction or geography.West is one of the four cardinal directions or compass points. It is the opposite of east and is perpendicular to north and south.By convention, the left side of a map is west....
ward. The following day, the area of disturbed weather began to become better organized, 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) upgraded its chances of tropical cyclone development to the "Medium" category. Moving towards the west-northwest, the area of disturbed weather was upgraded into a tropical depression during the morning hours of September 21, after radar
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
data showed that the low pressure area had gained enough structure to be declared as such. Due to a favorable upper regime characterized by 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 a moist environment, the National Hurricane Center predicted intensification into a hurricane within two days. Later on September 21, despite the fact that rainbands
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...
on the western semicircle of the depression became less defined, the depression acquired gale
Gale
A gale is a very strong wind. There are conflicting definitions of how strong a wind must be to be considered a gale. The U.S. government's National Weather Service defines a gale as 34–47 knots of sustained surface winds. Forecasters typically issue gale warnings when winds of this strength are...
-force winds, and was subsequently upgraded into a tropical storm, earning the name Hilary. That afternoon, the Government of Mexico issued a tropical storm watch for parts of the Mexican coastline, indicating that rainfall totals of 3-5 inches, with isolated 10 inch amounts, were possible.
On September 22, while quickly strengthening, Hilary was upgraded to a Category 1 hurricane 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...
. It was noted by the National Hurricane Center that strengthening into a major hurricane, defined by a hurricane with winds that exceed 111 miles per hour (178.6 km/h), was likely over the coming days. Just several hours later, Hilary was recorded as a rapidly strengthening Category 2 hurricane located in close proximity of the Mexican coastline. At 00:00 UTC September 23 (8:00 p.m. AST
Atlantic Standard Time Zone
The Atlantic Standard Time Zone is a geographical region that keeps time by subtracting four hours from either Coordinated Universal Time or Greenwich Mean Time , resulting in UTC-4 or GMT-4...
September 22), Hilary was upgraded into a major hurricane, the fourth of the season. Continuing to rapidly strengthen, Hilary became a Category 4 hurricane just a few hours later after becoming a Category 3, and reached a peak intensity of 145 mph (235 km/h) at 0600 UTC September 23 (11 p.m. AST September 22). However, the storm began to enter an area of higher wind shear and cooler ocean temperatures on September 24, and Hilary began to weaken. The hurricane weakened back down to a Category 3 hurricane early on September 25, but was later upgraded briefly to a Category 4 again the following afternoon. Several hours later, the storm was once again downgraded into a Category 3 hurricane, and during the afternoon hours of September 27, Hilary was further downgraded into a Category 2 hurricane. Early the following morning, Hilary weakened into a Category 1 hurricane, and weakened into a tropical storm on September 28. Losing a lot of its convection on September 30, the National Hurricane Center noted that Hilary had weakened into a tropical depression. Several hours later, after sustaining no deep convection atop its centre, Hilary was declared a remnant low, located several hundred miles away from any landmasses. But over the next few days, Hilary's remnants continued to move northwestward, as a convectionless vortex. By late on October 2, the convectionless swirl had dissipated over Southern California
Southern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...
.
Preparations and impact
The NHCNational 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...
noted the possibility of up to 10 in (254 mm) of rain in the high-terrain of Guerrero
Guerrero
Guerrero officially Estado Libre y Soberano de Guerrero is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo....
and Oaxaca
Oaxaca
Oaxaca , , officially Estado Libre y Soberano de Oaxaca is one of the 31 states which, along with the Federal District, comprise the 32 federative entities of Mexico. It is divided into 571 municipalities; of which 418 are governed by the system of customs and traditions...
, and large swell
Swell (ocean)
A swell, in the context of an ocean, sea or lake, is a series surface gravity waves that is not generated by the local wind. Swell waves often have a long wavelength but this varies with the size of the water body, e.g. rarely more than 150 m in the Mediterranean, and from event to event, with...
s were expected to impact coastal areas. Tropical cyclone watches and warnings were therefore issued for portions of the Pacific coast of Mexico. A red emergency alert was additionally in place for the region; officials urged residents to be prepared to evacuate, and tourists were advised to stay indoors. Due to rough surf, small craft advisories were put in effect, and swimmers were advised to take extreme caution. The port of Acapulco
Acapulco
Acapulco is a city, municipality and major sea port in the state of Guerrero on the Pacific coast of Mexico, southwest from Mexico City. Acapulco is located on a deep, semi-circular bay and has been a port since the early colonial period of Mexico’s history...
was closed for small vessels, and a moderate to high alert for strong winds and rain was noted.
The storm's outer 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...
produced torrential rains over Chiapas
Chiapas
Chiapas officially Estado Libre y Soberano de Chiapas is one of the 31 states that, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 118 municipalities and its capital city is Tuxtla Gutierrez. Other important cites in Chiapas include San Cristóbal de las...
and Tabasco
Tabasco
Tabasco officially Estado Libre y Soberano de Tabasco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 17 municipalities and its capital city is Villahermosa....
, with 24-hour accumulations of up to 8.58 in (217.9 mm) in Tabasco. Also in the state, four rivers overflowed their banks; one river received 51 in (1,295.4 mm) of excess water in a single day. Low-lying areas, such as grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...
s and pastures, experienced major flooding, prompting farmers to evacuate their livestock. In Villahermosa
Villahermosa
Like most of the Tabasco, Villahermosa has a tropical climate. The city specifically features a tropical monsoon climate. Temperatures during spring and summer seasons reach upwards of 40°C , with humidity levels hovering around 30% during the same period...
, the downpours resulted in the collapse of water drains, flooding many streets and stranding cars. Across Guerrero
Guerrero
Guerrero officially Estado Libre y Soberano de Guerrero is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo....
, three people were initially reported missing, but all three were later found. Twenty-thousand residents were advised to evacuated due to rising floodwaters. Offshore Colima
Colima
Colima is one of the 31 states which, with the Federal District, make up the 32 Federal Entities of Mexico. It shares its name with its capital and main city, Colima....
, large waves of 9 ft (2.7 m) to 15 ft (4.6 m) high were recorded.
See also
- Other storms with the same name
- List of California hurricanes
- 2011 Pacific hurricane season2011 Pacific hurricane seasonThe 2011 Pacific hurricane season is an ongoing, annual cycle of tropical cyclone formation. The season officially started on May 15, 2011, for the eastern Pacific, and started on June 1, 2011, for the central Pacific, both of which ended on November 30, 2011. These dates conventionally...