Tropical Storm Blanca (2009)
Encyclopedia
Tropical Storm Blanca was a short-lived tropical cyclone
during the 2009 Pacific hurricane season
. Forming out of a trough
of low pressure
on July 6, Blanca was immediately classified a tropical storm roughly 420 mi (675 km) south-southwest of the southern tip of the Baja California Peninsula
. Later that day, the storm reached its peak intensity with winds of 50 mph (85 km/h) and a barometric pressure of 998 mbar (hPa; 29.47 inHg) as deep convection
persisted around the center of circulation. Shortly after, the system began to weaken. Intermittent bursts of convection occurred on July 7 before Blanca weakened to a tropical depression. The following day, the system degenerated into a remnant low pressure system, devoid of shower and thunderstorms. The remnants were monitored by the National Hurricane Center for another day. Although the storm did not impact land as a tropical cyclone, its remnants produced unseasonable rains in southern California and moisture from the system contributed to flooding in Mexico.
that moved off the western coast of Africa into the Atlantic Ocean
on June 19. Traveling westward, the wave existed in a region of strong wind shear
, preventing convective activity
from developing. By June 29, the wave had crossed Central America
and moved into the eastern Pacific basin
. Several days later, the National Hurricane Center
(NHC) began monitoring the system as a disorganized area of shower and thunderstorm activity
off the southwest coast of Mexico. Early the next day, a trough
of low pressure
developed within the system; wind shear
in the path of the storm were expected to be low enough to allow tropical cyclone
development. On July 4, curved banding-features
developed along the periphery of the wave, indicating that an area of low pressure
had developed. Gradual organization took place over the follow days. Early on July 6, the low had become sufficiently organized to attain tropical depression strength roughly 435 miles (700 kilometres) south of Cabo San Lucas, Mexico. However, the system was not operationally declared a depression; instead, the first advisory by the NHC was issued several hours later and immediately declared the cyclone as Tropical Storm Blanca.
Upon being classified a tropical storm, Blanca had already developed an eye-feature
, though it not expected to develop into a hurricane. The storm maintained a general northwestward track throughout its existence due to a mid-level ridge
well to the west of the circulation. Shortly after, a central dense overcast, a large area of deep convection
, developed over the center of circulation and large banding features
developed along the periphery of the cyclone. Late on July 6, Blanca reached its peak intensity with winds of 50 mph (85 km/h) and a barometric pressure of 998 mbar (hPa; 29.47 inHg). Although the storm had intensified, its overall structure had deteriorated, with cloud tops warming and convection shrinking.
By July 7, most of the deep convection associated with Blanca had dissipated, and the remaining convection was confined to an outer band southeast of the center. Later that day, the system was barely holding on to tropical storm intensity as the center became devoid of shower and thunderstorm activity. A brief burst in convection allowed Blanca to maintain 40 mph (65 km/h) winds, minimal tropical storm intensity, for several more hours before being downgraded to a tropical depression.
Early on July 8, another brief burst in convection near the center of Blanca occurred. In this area, satellites found sustained winds around 40 mph (65 km/h). However, the convection quickly dissipated and the winds were not considered to be representative of the storm's true intensity. By later that day, convection had not reformed around the center of circulation and Blanca degenerated into a non-convective remnant low pressure system, corresponding with the final public advisory from the NHC. Although no longer a tropical cyclone, the remnants of Blanca maintained a well-defined low pressure center as it continued its northwesterly movement. Early on July 11, the system turned northward and gradually weakened. The following day, the remnants of Blanca dissipated over open waters.
, Jalisco
, Nayarit
, Baja California Sur
and Colima
and advised ships to remain at port. These advisories were discontinued the following day as Blanca moved out to sea. After weakening to a tropical depression, moisture from the system enhanced a frontal system
over Coahuila
. The system produced upwards of 22.2 mm (0.874015748031496 in) in the span of a few hours, triggering flooding throughout the state. Numerous streets were closed due to flooding and local fire departments were deployed to assist in draining the water. No injuries or structural damage resulted from the flooding.
The remnants of the storm also brought unseasonable rainfall, although negligible, to parts of southern and central California
on July 11. The moisture reached the region after being pulled northward by an upper-level low off the coast of Oregon
. While over open waters, the storm produced usually heavy rainfall, exceeding 2 in/h (50 mm/h) at times.
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...
during the 2009 Pacific hurricane season
2009 Pacific hurricane season
The 2009 Pacific hurricane season was an active event in the annual cycle of tropical cyclone formation, due to a moderate El Niño, unlike the 2009 Atlantic hurricane season, which was relatively quiet. The season officially started on May 15 in the eastern Pacific, and on June 1 for the central...
. Forming out of a trough
Trough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
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...
on July 6, Blanca was immediately classified a tropical storm roughly 420 mi (675 km) south-southwest of the southern tip of the Baja California Peninsula
Baja California Peninsula
The Baja California peninsula , is a peninsula in northwestern Mexico. Its land mass separates the Pacific Ocean from the Gulf of California. The Peninsula extends from Mexicali, Baja California in the north to Cabo San Lucas, Baja California Sur in the south.The total area of the Baja California...
. Later that day, the storm reached its peak intensity with winds of 50 mph (85 km/h) and a barometric pressure of 998 mbar (hPa; 29.47 inHg) as 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...
persisted around the center of circulation. Shortly after, the system began to weaken. Intermittent bursts of convection occurred on July 7 before Blanca weakened to a tropical depression. The following day, the system degenerated into a remnant low pressure system, devoid of shower and thunderstorms. The remnants were monitored by the National Hurricane Center for another day. Although the storm did not impact land as a tropical cyclone, its remnants produced unseasonable rains in southern California and moisture from the system contributed to flooding in Mexico.
Meteorological history
Tropical Storm Blanca 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 western coast of Africa into the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
on June 19. Traveling westward, the wave existed in a region of strong 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...
, preventing 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...
from developing. By June 29, the wave had 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 moved into the eastern Pacific 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...
. Several days 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) began monitoring the system as a disorganized area of shower and thunderstorm 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...
off the southwest coast of Mexico. Early the next day, a trough
Trough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
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...
developed within the system; 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...
in the path of the storm were expected to be low enough to allow 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...
development. On July 4, curved 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...
developed along the periphery of the wave, indicating that an 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...
had developed. Gradual organization took place over the follow days. Early on July 6, the low had become sufficiently organized to attain tropical depression strength roughly 435 miles (700 kilometres) south of Cabo San Lucas, Mexico. However, the system was not operationally declared a depression; instead, the first advisory by the NHC was issued several hours later and immediately declared the cyclone as Tropical Storm Blanca.
Upon being classified a tropical storm, Blanca had already developed an eye-feature
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...
, though it not expected to develop into a hurricane. The storm maintained a general northwestward track throughout its existence due to a mid-level ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
well to the west of the circulation. Shortly after, a central dense overcast, a large area of 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...
, developed over the center of circulation and large 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...
developed along the periphery of the cyclone. Late on July 6, Blanca reached its peak intensity with winds of 50 mph (85 km/h) and a barometric pressure of 998 mbar (hPa; 29.47 inHg). Although the storm had intensified, its overall structure had deteriorated, with cloud tops warming and convection shrinking.
By July 7, most of the deep convection associated with Blanca had dissipated, and the remaining convection was confined to an outer band southeast of the center. Later that day, the system was barely holding on to tropical storm intensity as the center became devoid of shower and thunderstorm activity. A brief burst in convection allowed Blanca to maintain 40 mph (65 km/h) winds, minimal tropical storm intensity, for several more hours before being downgraded to a tropical depression.
Early on July 8, another brief burst in convection near the center of Blanca occurred. In this area, satellites found sustained winds around 40 mph (65 km/h). However, the convection quickly dissipated and the winds were not considered to be representative of the storm's true intensity. By later that day, convection had not reformed around the center of circulation and Blanca degenerated into a non-convective remnant low pressure system, corresponding with the final public advisory from the NHC. Although no longer a tropical cyclone, the remnants of Blanca maintained a well-defined low pressure center as it continued its northwesterly movement. Early on July 11, the system turned northward and gradually weakened. The following day, the remnants of Blanca dissipated over open waters.
Preparations and impact
On July 6, Mexican officials posted high seas advisories for MichoacánMichoacán
Michoacán officially Estado Libre y Soberano de Michoacán de Ocampo is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 113 municipalities and its capital city is Morelia...
, Jalisco
Jalisco
Jalisco officially Estado Libre y Soberano de Jalisco is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is located in Western Mexico and divided in 125 municipalities and its capital city is Guadalajara.It is one of the more important states...
, Nayarit
Nayarit
Nayarit officially Estado Libre y Soberano de Nayarit is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 20 municipalities and its capital city is Tepic.It is located in Western Mexico...
, Baja California Sur
Baja California Sur
Baja California Sur , is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. Before becoming a state on October 8, 1974, the area was known as the South Territory of Baja California. It has an area of , or 3.57% of the land mass of Mexico and comprises...
and 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....
and advised ships to remain at port. These advisories were discontinued the following day as Blanca moved out to sea. After weakening to a tropical depression, moisture from the system enhanced a frontal system
Weather front
A weather front is a boundary separating two masses of air of different densities, and is the principal cause of meteorological phenomena. In surface weather analyses, fronts are depicted using various colored lines and symbols, depending on the type of front...
over Coahuila
Coahuila
Coahuila, formally Coahuila de Zaragoza , officially Estado Libre y Soberano de Coahuila de Zaragoza is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico...
. The system produced upwards of 22.2 mm (0.874015748031496 in) in the span of a few hours, triggering flooding throughout the state. Numerous streets were closed due to flooding and local fire departments were deployed to assist in draining the water. No injuries or structural damage resulted from the flooding.
The remnants of the storm also brought unseasonable rainfall, although negligible, to parts of southern and central 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...
on July 11. The moisture reached the region after being pulled northward by an upper-level low off the coast of Oregon
Oregon
Oregon is a state in the Pacific Northwest region of the United States. It is located on the Pacific coast, with Washington to the north, California to the south, Nevada on the southeast and Idaho to the east. The Columbia and Snake rivers delineate much of Oregon's northern and eastern...
. While over open waters, the storm produced usually heavy rainfall, exceeding 2 in/h (50 mm/h) at times.
See also
- 2009 Pacific hurricane season2009 Pacific hurricane seasonThe 2009 Pacific hurricane season was an active event in the annual cycle of tropical cyclone formation, due to a moderate El Niño, unlike the 2009 Atlantic hurricane season, which was relatively quiet. The season officially started on May 15 in the eastern Pacific, and on June 1 for the central...
- Timeline of the 2009 Pacific hurricane seasonTimeline of the 2009 Pacific hurricane seasonBelow is the Timeline of the 2009 Pacific hurricane season, documenting all the storm formations, strengthening, weakening, landfalls, extratropical transitions, as well as dissipation. The 2009 Pacific hurricane season officially began on May 15, 2009, and will last until November 30. For...