Tropical Storm Ignacio (1997)
Encyclopedia
Tropical Storm Ignacio was a weak tropical cyclone
that existed during August 1997. The 12th tropical cyclone
and 9th named storm of the 1997 Pacific hurricane season
, Ignacio formed west of Mexico
from a weather disturbance embedded within a more broad system. It was classified as a tropical depression on August 17, and although it quickly intensified into a tropical storm, harsher environmental conditions caused it to begin weakening as the cyclone moved northward. On August 19, Ignacio transitioned into an extratropical cyclone
as it approached California
, where its remnants produced unprecedented August rainfall, numerous traffic accidents, and 78,000 power outages.
, among multiple other disturbances. Later that day, banding features
formed and convection began turning counterclockwise around an area of low pressure
in the middle levels of the atmosphere. It continued to become better organized, and at 0000 UTC on August 17, the National Hurricane Center
classified it a tropical depression. At the time, the storm was situated approximately 520 mi (836.9 km) southwest of Cabo San Lucas
, outside of the area in which tropical cyclones usually form in the Eastern Pacific ocean basin.
The depression moved northwestward at 11 to 17 mph (17.7 to 27.4 km/h) under steering currents from a mid- to upper-level low pressure system offshore of California
and an associated trough
. A burst of deep convection formed near the cyclone's center early on August 17, and its estimated maximum sustained winds subsequently increased to 40 mph (64.4 km/h). As such, it was upgraded to Tropical Storm Ignacio at 1200 UTC. At the same time, the storm reached its lowest recorded barometric pressure of 1005 millibars
. However, due to increasingly colder waters and the presence of inhibiting southwesterly wind shear
, it immediately stopped intensifying. Ignacio maintained tropical storm status for a short time, and early on August 18, it weakened back into a depression.
During its weakening stage, deep convection existed only in the northwestern quadrant of the circulation. On August 19, cold cloud tops reappeared, although this brief revival was attributed to non-tropical baroclinic processes. At 1200 UTC, the depression was declared extratropical
, and it continued northward until dissipating near California a day later. Moisture from the system persisted as it passed through the state and the Pacific Northwest
, ultimately merging with a large extratropical cyclone involving the remnants of Hurricane Guillermo
.
which was estimated to be up to 7 ft (2.1 m) deep. Zinfandel
grape crops were disturbed by the heavy rainfall from Ignacio, and again from Hurricane Linda
in September.
Several weather-related traffic accidents occurred, at least one of which was described as "major". Two crashes on Interstate 80
forced the closure of four lanes for 30 minutes. It is unclear how many injuries resulted from the various incidents. Thunderstorms associated with the storm system left about 78,000 electric customers in Sonoma County
without power after lightning struck a power substation, although the outages lasted less than an hour. Lightning also knocked three workers unconscious in a vineyard near Lodi
, and they were in good condition after being hospitalized. Rainfall extended as far north as the Northwestern United States, ending an unusually long, 35-day dry spell at Astoria, Oregon
. It remains the most significant rainfall event from a tropical cyclone in Washington and Oregon
. Due to the lack of severe damage, the name Ignacio was not retired following its usage. It was reused during the 2009 season
, and remains on the rotating list of names.
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...
that existed during August 1997. The 12th 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...
and 9th named storm of the 1997 Pacific hurricane season
1997 Pacific hurricane season
The 1997 Pacific hurricane season was a very active hurricane season. With hundreds of deaths and billions of dollars in damage, this season was the costliest and one of the deadliest Pacific hurricane seasons. This was due to a strong El Niño...
, Ignacio formed west of Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
from a weather disturbance embedded within a more broad system. It was classified as a tropical depression on August 17, and although it quickly intensified into a tropical storm, harsher environmental conditions caused it to begin weakening as the cyclone moved northward. On August 19, Ignacio transitioned into an extratropical cyclone
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...
as it approached 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...
, where its remnants produced unprecedented August rainfall, numerous traffic accidents, and 78,000 power outages.
Meteorological history
Tropical Storm Ignacio originated in a broad weather system west of Mexico during the middle of August 1997. The specific precursor to Ignacio developed on August 16, well to the southwest of the Baja California PeninsulaBaja 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...
, among multiple other disturbances. Later that day, 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...
formed and convection began turning counterclockwise around 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...
in the middle levels of the atmosphere. It continued to become better organized, and at 0000 UTC on August 17, 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...
classified it a tropical depression. At the time, the storm was situated approximately 520 mi (836.9 km) southwest of Cabo San Lucas
Cabo San Lucas
Cabo San Lucas , commonly called Cabo, is a city at the southern tip of the Baja California peninsula, in the municipality of Los Cabos in the Mexican state of Baja California Sur. As of the 2010 census, the population was 68,463 people...
, outside of the area in which tropical cyclones usually form in the Eastern Pacific ocean basin.
The depression moved northwestward at 11 to 17 mph (17.7 to 27.4 km/h) under steering currents from a mid- to upper-level low pressure system offshore of 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...
and an associated 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...
. A burst of deep convection formed near the cyclone's center early on August 17, and its estimated maximum sustained winds subsequently increased to 40 mph (64.4 km/h). As such, it was upgraded to Tropical Storm Ignacio at 1200 UTC. At the same time, the storm reached its lowest recorded barometric pressure of 1005 millibars
Bar (unit)
The bar is a unit of pressure equal to 100 kilopascals, and roughly equal to the atmospheric pressure on Earth at sea level. Other units derived from the bar are the megabar , kilobar , decibar , centibar , and millibar...
. However, due to increasingly colder waters and the presence of inhibiting southwesterly 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...
, it immediately stopped intensifying. Ignacio maintained tropical storm status for a short time, and early on August 18, it weakened back into a depression.
During its weakening stage, deep convection existed only in the northwestern quadrant of the circulation. On August 19, cold cloud tops reappeared, although this brief revival was attributed to non-tropical baroclinic processes. At 1200 UTC, the depression was declared extratropical
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...
, and it continued northward until dissipating near California a day later. Moisture from the system persisted as it passed through the state and the Pacific Northwest
Pacific Northwest
The Pacific Northwest is a region in northwestern North America, bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains on the east. Definitions of the region vary and there is no commonly agreed upon boundary, even among Pacific Northwesterners. A common concept of the...
, ultimately merging with a large extratropical cyclone involving the remnants of Hurricane Guillermo
Hurricane Guillermo (1997)
Hurricane Guillermo was the sixth strongest Pacific hurricane on record, attaining peak winds of 160 mph and a barometric pressure of 919 mbar . Forming out of a tropical wave on July 30, 1997, roughly 345 mi south of Salina Cruz, Mexico, Guillermo tracked in a steady...
.
Impact
As a tropical cyclone, Ignacio had little or no effect on land. However, its remnants produced unprecedented precipitation in parts of coastal California. The rainfall reached record levels in some areas, amounting to as much as 2.17 in (55.1 mm). San Francisco received about 1 in (25.4 mm) of precipitation, leading to its wettest August on record, and the first time it had ever experienced measurable rainfall on August 19. In contrast, the area usually receives only a trace of moisture during August. The unusual rainfall triggered isolated flash flooding and a debris flowDebris flow
A debris flow is a fast moving, liquefied landslide of unconsolidated, saturated debris that looks like flowing concrete. It is differentiated from a mudflow in terms of the viscosity and textural properties of the flow. Flows can carry material ranging in size from clay to boulders, and may...
which was estimated to be up to 7 ft (2.1 m) deep. Zinfandel
Zinfandel
Zinfandel is a variety of red grape planted in over 10 percent of California vineyards. DNA fingerprinting revealed that it is genetically equivalent to the Croatian grape Crljenak Kaštelanski, and also the Primitivo variety traditionally grown in Puglia , where it was introduced in the 18th century...
grape crops were disturbed by the heavy rainfall from Ignacio, and again from Hurricane Linda
Hurricane Linda (1997)
Hurricane Linda was the strongest eastern Pacific hurricane on record. Forming from a tropical wave on September 9, 1997, Linda steadily intensified and reached hurricane status within 36 hours of developing. It rapidly intensified, reaching winds of and an estimated central pressure...
in September.
Several weather-related traffic accidents occurred, at least one of which was described as "major". Two crashes on Interstate 80
Interstate 80
Interstate 80 is the second-longest Interstate Highway in the United States, following Interstate 90. It is a transcontinental artery running from downtown San Francisco, California to Teaneck, New Jersey in the New York City Metropolitan Area...
forced the closure of four lanes for 30 minutes. It is unclear how many injuries resulted from the various incidents. Thunderstorms associated with the storm system left about 78,000 electric customers in Sonoma County
Sonoma County, California
Sonoma County, located on the northern coast of the U.S. state of California, is the largest and northernmost of the nine San Francisco Bay Area counties. Its population at the 2010 census was 483,878. Its largest city and county seat is Santa Rosa....
without power after lightning struck a power substation, although the outages lasted less than an hour. Lightning also knocked three workers unconscious in a vineyard near Lodi
Lodi, California
Lodi is a city located in , in the northern portion of California's Central Valley. The population was 62,134 at the 2010 census. The California Department of Finance's population estimate as of January 1, 2011 is 62,473....
, and they were in good condition after being hospitalized. Rainfall extended as far north as the Northwestern United States, ending an unusually long, 35-day dry spell at Astoria, Oregon
Astoria, Oregon
Astoria is the county seat of Clatsop County, Oregon, United States. Situated near the mouth of the Columbia River, the city was named after the American investor John Jacob Astor. His American Fur Company founded Fort Astoria at the site in 1811...
. It remains the most significant rainfall event from a tropical cyclone in Washington and 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...
. Due to the lack of severe damage, the name Ignacio was not retired following its usage. It was reused during the 2009 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...
, and remains on the rotating list of names.
See also
- Other tropical cyclones named Ignacio
- List of California hurricanes