Tropical Storm Norma was the fourteenth named

tropical cyclone A tropical cyclone is a rapidly rotating storm system with a low-pressure area, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depending on its locat ...

of the

1970 Pacific hurricane season The 1970 Pacific hurricane season was an active Northern hemisphere hurricane season, especially during its early months. It officially started on May 15, 1970, in the eastern Pacific Ocean (east of 140°W), and on June 1, 1970, in the ...

. The storm formed off the coast of Mexico and intensified rapidly, peaking as a strong tropical storm on September 3, before starting a weakening trend. It dissipated before making landfall on

Baja California Baja California, officially the Free and Sovereign State of Baja California, is a state in Mexico. It is the northwesternmost of the 32 federal entities of Mexico. Before becoming a state in 1952, the area was known as the North Territory of B ...

. While the storm never made landfall, the remnants from the storm fueled the Labor Day Storm of 1970, causing

floods A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

that resulted in heavy damage and loss of life. The rainfall from this storm broke records, mostly for 24-hour rainfall totals. Despite not being tropical when the damages were done, Norma is considered to be the deadliest disaster in

history.

Meteorological history

A tropical disturbance was first noted in a

satellite A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...

picture taken on August 30. Soon after, a weak low pressure center associated with the system formed southwest of

Acapulco Acapulco de Juárez (), commonly called Acapulco ( , ; ), is a city and Port of Acapulco, major seaport in the Political divisions of Mexico, state of Guerrero on the Pacific Coast of Mexico, south of Mexico City. Located on a deep, semicirc ...

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

. The system later went through

rapid intensification Rapid intensification (RI) is any process wherein a tropical cyclone strengthens very dramatically in a short period of time. Tropical cyclone forecasting agencies utilize differing thresholds for designating rapid intensification events, th ...

, becoming a tropical depression on August 31 and Tropical Storm Norma later that day. Initially, with a loose organization, Norma continued to organize and strengthen, reaching its peak of on September 2. Satellite pictures showed cirrus outflow was greater in the tops of the feeder bands than in the

eyewall The eye is a region of mostly calm weather at the center of a tropical cyclone. The eye of a storm is a roughly circular area, typically in diameter. It is surrounded by the eyewall, a ring of towering thunderstorms where the most severe weath ...

chimney. On September 3, Navy reconnaissance reported a 992 mbar pressure, Norma's lowest. Labor Day Storm of 1970 and Norma

Shortly after the 992 mbar report, however, Norma began to weaken. The same recon that reported the and 992 mbar reading reported back with a mere some time after. Despite the sudden drop in winds, the minimum pressure remained around 994 mbar. The weakening became obvious on satellite presentation, which showed cool inflow and a sheet of

stratocumulus A stratocumulus cloud, occasionally called a cumulostratus, belongs to a genus-type of clouds characterized by large dark, rounded masses, usually in groups, lines, or waves, the individual elements being larger than those in altocumulus, and the ...

clouds around the west semicircle extending under the storm clouds. Norma continued to weaken, degrading into a depression by September 4. At this point, the circulation forced moist and unstable maritime air into Arizona which resulted in disastrous floods during

Labor Day Labor Day is a Federal holidays in the United States, federal holiday in the United States celebrated on the first Monday of September to honor and recognize the Labor history of the United States, American labor movement and the works and con ...

along with a slow moving

cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface Trough (meteorology), trough of Low-pressure area, low pressure. It often forms behind an extratropica ...

. This system would become known as the Labor Day Storm of 1970. On September 5, a cloud spiral was still visible west of

, but the storm's circulation dissipated, with the remnants of the storm finally dissipating on September 6, just before making landfall on Baja California.

Impact

While Norma did not make

landfall Landfall is the event of a storm moving over land after being over water. More broadly, and in relation to human travel, it refers to 'the first land that is reached or seen at the end of a journey across the sea or through the air, or the fact ...

while

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

(even though it came close to making landfall on

before dissipating), the circulation introduced unstable air into

and

Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...

which, along with a cold front, resulted in record amounts of

rainfall Rain is a form of precipitation where water droplets that have condensed from atmospheric water vapor fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. ...

Baja California

For an stretch of the coat, waves were measured. Winds of were recorded at Bahia Tortugas, a village on Punta Eugenia.

Arizona

The rainfall in Arizona produced deadly

flash floods A flash flood is a rapid flooding of low-lying areas: washes, rivers, dry lakes and depressions. It may be caused by heavy rain associated with a severe thunderstorm, hurricane, or tropical storm, or by meltwater from ice and snow. Flash fl ...

which caused over $1 million in damages and killed 23 people, 14 of whom died when Tonto Creek, which was in the vicinity of Kohl's Ranch, became flooded. Other deaths were reported among

automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

drivers. Total rainfall exceeded 7 inches in certain locations, with Workman's Creek receiving of rain. Other amounts were recorded in Upper Parker Creek (9.09 inches),

Mount Lemmon Mount Lemmon, with a summit elevation of , is the highest point in the Santa Catalina Mountains. It is located in the Coronado National Forest north of Tucson, Arizona, United States. Mount Lemmon was named for botany, botanist Sara Plummer Lemm ...

(8.74 inches), Sunflower (8.44 inches),

Kitt Peak Kitt Peak () is a mountain in the U.S. state of Arizona, and at is the highest point in the Quinlan Mountains. It is the location of the Kitt Peak National Observatory. The radio telescope at the observatory is one of ten dishes comprising the ...

(8.08 inches), Tonto Creek Fish Hatchery (7.12 inches), and Crown King (7.02 inches). There were also reports of injuries by campers in

Mogollon Rim The Mogollon Rim ( or or ) is a topography, topographical and geological feature cutting across Northern Arizona, the northern half of the U.S. state of Arizona. It extends approximately , starting in northern Yavapai County, Arizona, Yavapa ...

and Scottsdale reported significant

property damage Property damage (sometimes called damage to property) is the damage or destruction of real or tangible personal property, caused by negligence, willful destruction, or an act of nature. Destruction of property (sometimes called property de ...

. As many as 23 lives were lost due to the unprecedented nature of the floods, with 14 deaths reported from flash flooding near Tonto Creek. The major flooding in the state prompted a presidential disaster declaration.

Utah

While the storm was causing floods in Arizona, the lower cities of

were also experiencing heavy rainfall. The most noteworthy rainfall total was recorded in Bug Creek, which experienced an estimated of rain in a 24-hour period. No deaths or damage was reported in connection to the storm.

Records

When of rain fell at Workman's Creek in a 24-hour period, it became the highest amount of rain to fall in

in a 24-hour period. The record stood until 1997, when the remnants of Hurricane Nora produced of rain on the top of Harquahala Mountain. A similar record was recorded in Utah when of rain fell in Bug Creek in a 24-hour period. Unlike the Arizona rainfall record, this record still stands today. When the rains of Norma caused the San Juan River to flood its banks, a size of 1,090 m³ was obtained, making this the largest flood of the San Juan since 1962, when the Navajo Dam was completed. The most runoff from the storm was downstream from the reservoir.Changes in Riparian Vegetation in the Southwestern United States: Floods and Riparian Vegetation on the San Juan River, Southeastern Utah
/ref> With 23 associated deaths in

, Norma was the deadliest storm in the state's history.

References

External links

Monthly Weather Reports from up to 1972 (PDF files).

A more extensive collection of Monthly Weather Reports up to and including 2006 (PDF files.
{{DEFAULTSORT:Norma (1970)

Norma Norma may refer to: * Norma (given name), a given name (including a list of people with the name) ** Norma Lizbeth Ramos, a Mexican bullying victim Astronomy *Norma (constellation) * 555 Norma, a minor asteroid * Cygnus Arm or Norma Arm, a spiral ...

Norma 1970 Norma 1970 Tropical Storm Norma Tropical Storm Norma Hurricanes and tropical depressions of the Gulf of California 1970 in Arizona Hurricanes in Baja California Sur Hurricanes in Baja California Hurricanes in Sonora Hurricanes in Utah