1970 Pacific hurricane season
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| First storm formed: | May 30, 1970 |
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| Last storm dissipated: | November 8, 1970 |
| Strongest storm: | Lorraine - 963 mb, Patricia - 95 knots |
| Total storms: | 19 |
| Major storms (Cat. 3+): | 0 |
| Total damage: | minimal direct, 1 million indirect (1970 USD) |
| Total fatalities: | 0 direct, 22 indirect |
| Pacific hurricane seasons 1950-1969, 1969, 1970, 1971, 1972 |
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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.
| Saffir-Simpson Hurricane Scale | ||||||
| TD | TS | 1 | 2 | 3 | 4 | 5 |
[edit] Storms
[edit] Hurricane Adele
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| Duration | May 30—June 7 | |||
| Intensity | 85 mph (140 km/h), ≤993 mbar | |||
The first named storm and hurricane of the season developed on May 30 southwest of Mexico. Adele tracked westward, becoming a hurricane on June 1. It slowly died down, and dissipated on June 7. Despite that it remained away from any land masses, Adele was retired after this season for unknown reasons.
[edit] Tropical Storm Blanca
The tropical disturbance that became Blanca was first noted on June 8th from satellite pictures. The new disturbance would reach tropical storm strength 24 hours later. Blanca moved in a northwest direction throughout its short life, dissipating on the 12th.
[edit] Tropical Storm Connie
Near the same location where Hurricane Adele formed two weeks earlier, a disturbance was noted on June 13th. The disturbance abruptly became a tropical storm on June 17th. The newly named Connie moved slowly to the northwest, reaching a peak intensity of 50 mph on June 18. Connie started weakening on the 19th, finally dissipating on June 21 after stalling 100 nautical miles from Clarion Island.
[edit] Tropical Depression Dolores
A disturbance first noted on June 19th had efficient outflow to be called a tropical depression. Satellite photos taken the same day revealed cloud structure that resembled a tropical storm forming, resulting in the system being called Dolores. The day after, no traces of a storm or of "Dolores" were found by reconnaissance. Post season analysis revealed Dolores to have only been a tropical depression.
[edit] Tropical Storm Eileen
A tropical depression formed just off the southern coast of Mexico on June 26. It headed northwestward, reaching storm strength on June 28. The next day, Eileen turned to the northeast, reached a peak of 45 mph winds, and hit western Mexico.
[edit] Hurricane Francesca
Francesca was a category 2 hurricane which was, for a period of time, obscured by a cap of clouds above the hurricane's eye, distorting the appearance of the hurricane.
The precursor disturbance to Hurricane Francesca was first noticed on July 1st. The system became a tropical depression later that day and reached tropical storm strength the next day. On July 3rd, data from a ship indicated winds of near 100 mph, which indicate a storm of Category 2 strength, near the center of Francesca. The cloud cap, which remained over the hurricane since it first became a hurricane, started to move off the lower clouds around the center of the system around July 5th. A center fix was obtained, but the maximum sustained winds were unobtainable from the sea surface because of cloud cover in and around the center. Francesca started weakening on July 6th, a fact made clear by reconnaissance which indicated that the system had weakened to a tropical storm. The further weakening was obscured by the cloud cover. The final reconnaissance on the weakening system was reported on July 8th, two days before Francesca dissipated.
[edit] Tropical Storm Gretchen
Gretchen was first noticed on satellite imagery on July 14th. From then on out, Gretchen was a hard storm to predict, leading to large errors in forecasting. The storm dissipated on the July 21st.
[edit] Tropical Storm Helga
The system that became Helga was first noticed on July 16th. The next day, reconnaissance found a minimal tropical storm with winds of only 40 mph. Based on satellite imagery, Helga was believed to be gaining strength as it approached Baja California. At one point during intensification, the storm abruptly started weakening, and on July 19th, after stalling less than 100 nautical miles south of the tip of Baja California, Helga dissipated.
[edit] Tropical Storm Ione
A tropical depression developed off the southern coast of Mexico on July 22. It tracked westward, reaching tropical storm strength on the two days later before dissipating on July 26. 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 winds before dissipating on July 25.
[edit] Tropical Storm Joyce
A broad, flat low-pressure area persisted south of Baja California after Ione dissipated. On July 29th, a small low circulation developed with a center about 120 nautical miles south of Manzanillo. The system was given the name Joyce after winds of 40 mph 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 31st with winds of near 60 mph before weakening, becoming a depression on August 1st. Joyce dissipated on August 4th.
[edit] Tropical Storm Kristen
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 5th. Kristen was tracked by ship reports and satellite pictures. Kristen reached its peak intensity of 50 mph winds on August 6th. The storm dissipated on August 8th while over cold water.
[edit] Hurricane Lorraine
Tropical Storm Lorraine, which formed on August 16 south of Mexico, intensified to a hurricane on the 20th. Two days later over open waters, it reached a peak of 95 mph (153 km/h) winds, but estimates from the Central Pacific Hurricane Center estimated it had winds of 115 mph (185 km/h). Without a chance to strengthen further, Lorraine weakened, finally dissipating on August 27 due to dry air.
[edit] Tropical Storm Maggie
A small cloud vortex slowly organized into a tropical depression on August 20 while southeast of Hawaii. It headed west-northwestward, becoming a tropical storm that night and reaching a peak of 60 mph (97 km/h) winds on August 23. 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.
[edit] Tropical Storm Norma
- Main article: Tropical Storm Norma (1970)
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.
[edit] Hurricane Dot
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 35º north, it became the second highest latitude for a storm to reach hurricane strength, only behind Hurricane 12 of the 1975 season.
[edit] Tropical Storm Orlene
65 mph Tropical Storm Orlene hit Mexico in eastern Oaxaca on September 8, having maintained a northeast track for its short lifetime.
[edit] Hurricane Patricia
Hurricane Patricia, the strongest storm of the season with winds of 95 knots, remained over the open waters of the Eastern Pacific. It lasted from October 4 to October 11.
[edit] Tropical Storm Rosalie
Rosalie's existence was confirmed on October 21st 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.
[edit] Tropical Storm Selma
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.
[edit] 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.
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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 first and 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 back to Kirsten.
[edit] 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.
[edit] See also
- List of notable tropical cyclones
- 1970 Atlantic hurricane season
- 1970 Pacific typhoon season
- 1969-70 Southern Hemisphere tropical cyclone season
- 1970-71 Southern Hemisphere tropical cyclone season
- Pre-1980 North Indian cyclone seasons
[edit] References
- 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
