The 1968 Pacific hurricane season tied the record for the most active August in terms of tropical storms. It officially started on May 15, 1968, in the eastern Pacific and June 1 in the central Pacific and lasted until November 30, 1968. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean.
Several notable systems formed during the season. Five named storms—Hyacinth, Iva, Liza, Naomi, and Pauline—had effects in the United States. Two others—Annette and Tropical Depression Two—affected Mexico, and Tropical Storm Simone made a rare landfall on Guatemala. Tropical Storm Virginia, which formed in the West Pacific, crossed into the basin at a high latitude.
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Season summary
Twenty-five tropical cyclones formed this season, resulting in 501 advisories being issued in the Eastern Pacific (east of 140°W), and 30 being issued for the Central Pacific (between 140°W and the International Date Line), both records at the time. Of these, six remained depressions, thirteen peaked as tropical storms, and six reached hurricane strength. There were no major hurricanes this season. Many of the tropical cyclones this season – including all six hurricanes – formed from Intertropical Convergence Zone (ITCZ) disturbances. Eight tropical storms formed in August this year, a record for the most active August in the East Pacific, excluding Virginia. The eight named storms forming in August this year also made it the most tropical storms to ever form in a month in the East Pacific since 1966. However, this record was tied during the 2009 Pacific hurricane season. Because of a lack of Hurricane Hunter data, a majority of the intensity readings from this season were later removed from the best track file. Only one pressure reading from this season – a reading taken from Hurricane Pauline on October 29 when it was a tropical depression – was left on the best track data, although a pressure of taken from Tropical Storm Simone was used to set its peak intensity.
Systems
Tropical Storm Annette
Even though the James Lykes noted that an area of disturbed weather south of the Pacific coast of Mexico was poorly organized, it reported south-southwest winds of on June 20. It made landfall and dissipated near Manzanillo on June 22. The satellite that was orbiting over Annette never took a picture with the storm in view since the storm was usually at the edge of the satellite. A computerized mosaic showed a spiral vortex with the center over land, which was unhelpful in tracking the storm because ship reports noted that the circulation was over water. Damage, if any, is not known.
Tropical Storm Bonny
The first of a large group of tropical cyclones that developed from ITCZ disturbances this season, a low pressure center in the ITCZ rapidly developed late on July 3. Becoming a tropical storm on July 4, the storm received the name Bonny. The newly named storm tracked west-northwest for 24 hours before turning to the north overnight on July 5 into July 6. As a result, winds of were measured on Socorro Island, which was located to the east-northeast of the storm's center. At this time, satellites revealed that cooler sea surface temperatures and stratus inflow were starting to take their toll on Bonny. The storm began a slow dissipation and, by the time a nearby ship reported the status of the weakening storm, the system had already dropped to depression strength with winds. The storm dissipated on July 9. The remnant low of Bonny had no kinetic energy, causing the forecasters to note that it had a ragged appearance on satellite imagery.
Tropical Storm Celeste
The disturbance that became Celeste was first noticed by the Eastern Pacific Hurricane Center on July 13. The disturbance slowly intensified, becoming a tropical depression on July 14 and reaching storm strength on the next day. The intensity when the system was named was , but in post-season analysis the storm's peak wind speed was downgraded into . This difference in intensity was blamed on brightness issues on the photo taken by satellite, making the storm look more powerful than it really was. The storm never strengthened past the peak it had reached when it became a storm. The storm would continue uneventfully until July 17, when stratus inflow was starting to become entrained in the atmospheric circulation and, shortly after peaking, the storm began to weaken after strong inflow of cool air to the northwest. The weakening Celeste became less discernible in recon reports, but the cloud vortex was still well defined. On July 20, the storm was downgraded into a depression and dissipated 24 hours afterward.
Tropical Storm Diana
While Celeste was weakening, a tropical disturbance associated with the ITCZ first appeared on July 19. After Celeste lost its tropical identity on July 21, the former had strengthened enough to be upgraded to tropical storm strength and was given the name "Diana". The banding in the center of the upgraded system was obscured by heavy cirrus outflow. The initial intensity set was . The Anco Swan, a ship north of Tropical Storm Diana, indicated that the tropical storm had reached its peak intensity around this time, which was maintained for two days. Then, cool inflow had become elongated in the storm, resulting in weakening. The storm degenerated into a depression on July 24 and continued moving westward. The depression finally dissipated on July 26, well away from land.
Tropical Storm Estelle
Estelle was a tropical storm that spent most of its life as a depression as a result of a southward shift in trade winds and the ITCZ, which provoked an early weakening and prevented re-intensification. The storm originated in a disturbance associated with the ITCZ. The disturbance had become a tropical depression on July 23 and reached storm strength the next day. The new tropical storm maintain a intensity for only 30 hours, when it weakened back to a depression. The weakened Estelle continued westward, passing into the Central Pacific around July 31. The group that oversaw the Central Pacific at the time – the Joint Hurricane Warning Center – issued the depression's final advisory on August 1. Tropical Storm Estelle was notable in that it had advisories issued on it in the Central Pacific despite never actually crossing into the area of responsibility. It dissipated at a longitude of 139.6°W, whereas the Central Pacific begins at 140°W. However, last operational advisory centered the storm at 141.6°W.
Hurricane Fernanda
The trade winds that had resulted in the weakening of Estelle in late July had decreased in early August, allowing a weak disturbance in the ITCZ to organize near Acapulco. By August 5, the disturbance had developed a vortex and advisories were started on the newly formed depression. The depression would continue to strengthen and, after acquiring significant cirrus outflow, was upgraded to tropical storm intensity on August 6. Fernanda continued to develop, despite the proximity of Tropical Storm Gwen, which was to the east-northeast of the center. On August 8, the storm had developed an eye in a tightly wound spiral overcast and became a hurricane while moving westward. Cool inflow began to get trapped in the circulation, causing the hurricane to weaken to a storm on August 9, but due to the hurricane moving over warmer water, it was not enough to begin dissipation alone. The feeder bands, which helped the hurricane to reach its peak intensity, continued to persist over warm water until August 11, when the cirrus cap over Fernanda became uncoupled to the east, thus exposing the west side of the storm. Plane reports showed the hurricane had moved under westerly winds in the troposphere, which resulted in the storm weakening to a depression on August 13. Shower activity from the hurricane continued diminishing until August 14, and, early on August 15, Fernanda dissipated, having never affected land.
Tropical Storm Gwen
The ITCZ-based depression which developed into Gwen was first noted on August 5 while south of Tehuantepec. Although a ship in the region reported winds and waves, a satellite picture revealed a cloud mass of amorphous quality. Although a little vortex in the region was visible, the system would show little development for 48 hours until, on August 7, stronger rotation and outflow were apparent in satellite imagery. The next day, a ship north of the center reported waves and winds. Data based on satellite images, and the ship report, were enough to upgrade the system to Tropical Storm Gwen. Around this time, the track of the newly named system was being affected by the stronger Fernanda to its west via Fujiwhara effect. Shortly thereafter, satellite photos showed an exposed atmospheric circulation in the northwest section of the storm with cloud cover lagging behind it, and the storm was downgraded to a depression on August 8. The circulation was completely exposed by the next day, and Gwen dissipated. The remnants of Gwen continued to interact with Fernanda until complete dissipation.
Tropical Storm Hyacinth
The origins of Hyacinth were linked to a cold front that was over Texas on August 11. There was no activity associated with the disturbance until August 16, when a circular overcast broke away from the front. The overcast breaking away was related to a newly formed low, which moved north-northwest while rapidly intensifying, becoming a tropical storm on August 17. Hyacinth continued to move north-northwestward, entering the mouth of the Gulf of California later that day, and a ship reported a barometric pressure of . Another ship report, showing winds of , was received at the same time. The storm passed east of La Paz, Baja California Sur, on August 18, and the next day, it made landfall near Los Mochis, Sinaloa. The clouds associated with the storm were tracked into the southwestern United States, causing showers and thunderstorms over Arizona, New Mexico, and Colorado on August 20. The storm dissipated on August 21. No deaths were reported in connection to Hyacinth, and damage from Mexico is unknown.
Tropical Storm Iva
While the moisture and clouds associated with Hyacinth moved northward, an area of rain-producing clouds along the ITCZ stretched from the Gulf of Tehuantepec to Clipperton Island. On August 20, two disturbances formed southwest of Mexico, the first was found via satellite imagery and the second was found by ship report. The disturbance further west developed into Tropical Storm Iva while the other disturbance ultimately became Hurricane Joanne. Ship reports on August 21 led to the disturbance to be upgraded into a tropical storm. However, in best track data, Iva was at depression strength throughout this date, becoming a tropical storm on August 22. Winds of up to were recorded north of the center, which had shifted to 13.5°N, 98.5°W. Despite the winds, a satellite photo of the storm showed poor organization. The storm intensified slowly while moving west-northwest at for the next 48 hours. On August 24, the storm passed south of Socorro Island, which reported winds of . By this time, the storm was moving northwestward at due to the influence of strengthening Hurricane Joanne. Later on August 24, a picture of Iva and Joanne showed that the cirrus cap over Iva was becoming separated from the circulation. The storm began weakening afterward, weakening to a depression on August 25 after moving over cool sea surface temperatures. The rain clouds associated with the weakening depression moved westward, producing rains for 12 hours until the storm dissipated early on August 26.