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1970 Pacific hurricane season
Season summary map
Seasonal boundaries
First system formed	May 30, 1970
Last system dissipated	November 8, 1970
Strongest storm
Name	Lorraine
• Maximum winds	100 mph (155 km/h) (1-minute sustained)
• Lowest pressure	963 mbar (hPa; 28.44 inHg)
Seasonal statistics
Total depressions	21
Total storms	19
Hurricanes	5
Major hurricanes (Cat. 3+)	0
Total fatalities	0 direct, 22 indirect
Total damage	Unknown
Pacific hurricane seasons 1968, 1969, 1970, 1971, 1972

The 1970 Pacific hurricane season began on May 15, 1970 in the east Pacific, and on June 1, 1970 in the central Pacific. It ended on November 30, 1970. These dates conventionally delimit the period of time when tropical cyclones form in the eastern Pacific Ocean.

This season had an above average number of storms. There were twenty-one tropical cyclones, of which eighteen reached tropical storm strength. Four storms became hurricanes, of which none reached major hurricane strength. In the central Pacific, one hurricane and one tropical depression formed. One of the depressions crossed the dateline to become a typhoon.

Storms

Tropical Storm Ione 1

Tropical storm (SSHWS)
Duration	July 22 – July 26
Peak intensity	50 mph (85 km/h) (1-min);

A tropical depression developed off the southern coast of Mexico on July 22. A larger, more active, and intensifying tropical cyclone was spotted by satellite at 2235 on the 24th near 17°N., 111°W. When the expanding circulation of this storm center reached the area of lone No. 1, winds in the latter area decreased and lone No. 1 disappeared abruptly. The second storm, also called lone, moved north-northwestward and began to weaken. Her top winds were apparently reached about the time of the picture on the 24th which indicated speeds of 55 or 60 kn. Maximum winds on the 25th were 45 kn. near 20. N.,112°W. These winds decreased to 25 kn. the next day as storm activity faded rapidly near 16 N., 113°W'. What was unusual about the system was that another tropical storm developed just to its northeast on July 24. That storm, also named Ione, tracked northward, reaching a peak of 60 mph (97 km/h) winds before dissipating on July 25. Operationally, these were considered to be the same storm.

Tropical Storm Ione 2

Tropical storm (SSHWS)
Duration	July 24 – July 25
Peak intensity	60 mph (95 km/h) (1-min); 1007 mbar (hPa)

A tropical depression was discovered near 14°N.,102°W., at 1800 on July 22, but it became disorganized as seen on satellite pictures the next day. Later events indicate it was splitting into two tropical cyclones, both of which were to attain tropical storm strength. The tropical storm first called lone was encountered by the KANIKAWA MARU at 2100 on July 24. That ship was buffeted by 48-kn southeasterly winds and 15-ft seas near 21°N, 107°W. The storm washed out the next day.

Tropical Storm Joyce

Tropical storm (SSHWS)
Duration	July 29 – August 4
Peak intensity	60 mph (95 km/h) (1-min); 1000 mbar (hPa)

A broad, flat low-pressure area persisted south of Baja California after Ione dissipated. On July 29, a small low circulation developed with a center about 120 nautical miles (220 km) south of Manzanillo. The system was given the name Joyce after winds of 40 mph (64 km/h) were reported by a ship. In a similar way to Hurricane Francesca, Tropical Storm Joyce's low level center was unclear due to a cap of cirrus clouds. Joyce reached its peak intensity on July 31 with winds of near 60 mph (97 km/h) before weakening, becoming a depression on August 1. Joyce dissipated on August 4.

Tropical Storm Kristen

Tropical storm (SSHWS)
Duration	August 5 – August 8
Peak intensity	50 mph (85 km/h) (1-min); 1005 mbar (hPa)

Kristen was a loosely organized storm that formed from a disturbance that was causing squalls near the Mexican coast. Tropical storm-force winds were found on August 5. Kristen was tracked by ship reports and satellite pictures. Kristen reached its peak intensity of 50 mph (80 km/h) winds on August 6. The storm dissipated on August 8 while over cold water.

Tropical Storm Maggie

Tropical storm (SSHWS)
Duration	August 20 – August 27
Peak intensity	60 mph (95 km/h) (1-min); 993 mbar (hPa)

A flat low-pressure system appeared in an area of showers to the west-southwest of hurricane Lorraine around 1800 on the 20th. The French refrigerated cargo carrier BIAFRA was buffeted by 38-kn southerly winds, with a barometer reading 1006 mbar, near 13'N, 132'W, by the soon to be named tropical storm Maggie at 0000 on the 21st. Maggie intensified slowly while moving west-northwestward at 9 kn; her maximum winds were estimated at 55 kn at 0300 on the 25th. Maggie passed about 80 mi south of the island of Hawaii on the 25th, dumping torrential rains over the big island. Rainfall amounts ranged from 10 to 15 in on the windward side of the island from the Hamuka coast to Puna and from 1 to 7 in on the leeward side. Maggie was downgraded to a tropical depression at 0900 on the 26th near 18N, 157W. A westward turn saved Hawaii from a direct hit, but Maggie still brought strong surf and heavy yet beneficial rain to the island of Hawaii. There is some evidence that the remains of Maggie redeveloped into Hurricane Dot in the Central Pacific on September 1.

Tropical Storm Norma

Tropical storm (SSHWS)
Duration	August 31 – September 6
Peak intensity	95 km/h (60 mph) (1-min); 988 hPa (mbar)

Norma was an indirect but essential cause of a flood disaster in Arizona that became known as the "Labor Day Storm of 1970". A depression formed August 31 and rapidly intensified into a tropical storm. Moving rapidly, it headed out to sea before slowing down and weakening. Norma's circulation fed humid unstable air into a large extratropical cyclone over Arizona. As Norma dissipated, record rains fell over the state from September 4 to September 6.

The rains were deadly. There were a total of 22 deaths, including 14 from a flash flood on a creek. The damage amounted to over 1 million dollars.

Hurricane Dot

Category 1 hurricane (SSHWS)
Duration	September 1 – September 4
Peak intensity	80 mph (130 km/h) (1-min); 993 mbar (hPa)

A tropical disturbance, possibly the remnants of Tropical Storm Maggie, became a tropical depression on September 1 to the northwest of Hawaii. It moved to the northwest, coming within miles of the International Date Line and Midway Island but remaining in the Central Pacific. Dot turned to the northeast, reaching tropical storm strength on September 2 and hurricane strength September 3 before being absorbed by a cold core system the next day. When Dot became a hurricane at 35° north, it became the highest latitude for a storm to reach hurricane strength east of the International Dateline. This record was soon eclipsed by Hurricane 12 of the 1975 season. A flight flown into Dot also flew into Typhoon Clara.

Tropical Storm Orlene

Tropical storm (SSHWS)
Duration	September 7 – September 9
Peak intensity	65 mph (100 km/h) (1-min); 995 mbar (hPa)

65 mph (105 km/h) Tropical Storm Orlene hit Mexico in eastern Oaxaca on September 8, having maintained a northeast track for its short lifetime.

Hurricane Patricia

Category 2 hurricane (SSHWS)
Duration	October 4 – October 11
Peak intensity	100 mph (155 km/h) (1-min); 972 mbar (hPa)

Hurricane Patricia was a strong Category 2 hurricane with winds of 95 mph, Patricia formed on October 4 and dissipated on October 11.

Tropical Storm Rosalie

Tropical storm (SSHWS)
Duration	October 21 – October 23
Peak intensity	55 mph (90 km/h) (1-min); 1006 mbar (hPa)

Rosalie's existence was confirmed on October 21 by observation from a ship. Reconnaissance on the 22nd reported a central pressure of 1006 mb. After a slight regeneration on the 23rd, Rosalie began rapid dissipation, finally dissipating on the 23rd.

Tropical Storm Selma

Tropical storm (SSHWS)
Duration	November 1 – November 8
Peak intensity	70 mph (110 km/h) (1-min); 995 mbar (hPa)

The final storm of the season, Tropical Storm Selma, developed on November 1 to the southwest of Mexico. It meandered to the north, turning to the northeast and northwest before heading southeastward and dissipating on November 8.

1970 Storm Names

These names were used for storms that formed in the east Pacific Ocean this season. It is the same list used in the 1966 season. Names not retired from this list were used again in the 1974 season. Storms were named Norma, Orlene, Patricia, Rosalie, and Selma for the first time this season. Names not used this year are marked in gray.

One storm, Ione, was treated as one storm operationally but was found to have been two storms in post-analysis. Another storm, Dolores, was found to have been a tropical depression in post-season analysis and shouldn't have been named.

The central Pacific used names and numbers from the west Pacific's typhoon list. One name— Dot— was required.

The name Adele was retired from this list for no particular reason. It was replaced in the 1974 season with Aletta.

This is the only time that the name Kristen was used. In the 1966 season the name Kirsten was used. It was changed to Kristen this year, perhaps due to a clerical error. In the 1974 season, it reverted to Kirsten.

Administrative Changes

This is the first season that the Redwood City-based Eastern Pacific Hurricane Center started issuing advisories on tropical cyclones in the eastern north Pacific. It replaced the previous forecaster, Fleet Weather Central.

The Central Pacific Hurricane Center started to issue advisories on tropical cyclones in its area of responsibility this season. It replaced the Joint Hurricane Warning Center.

See also

• List of Pacific hurricanes
• List of Pacific hurricane seasons
• 1970 Atlantic hurricane season
• 1970 Pacific typhoon season
• 1970 North Indian Ocean cyclone season
• Southern Hemisphere tropical cyclone seasons: 1969–70, 1970–71

References

1. Climatological Data National Summary 1970

• Unisys Storm Tracks accessed November 17, 2005
• CPHC Archive accessed November 17, 2005
• NOAA Monthly Weather Review accessed November 17, 2005
• Arizona's tropical cyclones accessed November 17, 2005

External links

• Eastern Pacific Hurricane Season of 1970
• CPHC Season Summary
• ATCR Eastern Pacific summary
• Unisys Storm Tracks

v t e Tropical cyclones of the 1970 Pacific hurricane season
	1Adele TSBlanca TSConnie TDDolores TSEileen 2Francesca TSGretchen TSHelga TSIone Two TSIone One TSJoyce TSKristen 2Lorraine TSMaggie TSNorma 1Dot TSOrlene 2Patricia TSRosalie TSSelma
Category

• Pacific hurricane seasons
• 1970 Pacific hurricane season