The 1991 Pacific hurricane season was a near-average Pacific hurricane season. The worst storm this year was Tropical Storm Ignacio, which killed 23 people in Mexico and injured 40 others. Elsewhere, Hurricane Fefa caused flooding in Hawaii. Hurricane Kevin was the strongest system of the season and became the then longest-lasting hurricane in the eastern north Pacific basin at the time, and Hurricane Nora was the strongest November storm to that point. The season officially started on May 15, 1991, in the eastern Pacific, and on June 1, 1991, in the central Pacific. It lasted until November 30, 1991, in both basins. These dates conventionally delimit the period of each year when most tropical cyclones form in the northeastern Pacific Ocean.
Seasonal summary
During the season, a total of sixteen tropical cyclones developed, featuring ten hurricanes, four tropical storms and two tropical depressions. These totals are close to the climatological averages established since 1966, when satellite surveillance began. However, the season was less active than 1990, which had a record 16 hurricanes (more than 1991). Yet, it ended late with the first November hurricane on record in the satellite era. On the other hand, the months of July and August, often the most active ones in this basin, only produced two tropical cyclones each. The activity in July was four systems below the average of six at that time due to unusual circulation patterns aloft over the tropical Pacific. A shorter gap in activity from late August to early September was attributed to anomalous flow patterns near the Baja California Peninsula. Several tropical cyclones grew into specially long-lived and intense systems. For example, Hurricane Kevin endured as a hurricane for 12.5 days to the east of 140°W, establishing a new record for longevity in the eastern Pacific.
None of the tropical storms or hurricanes made landfall. One of the two tropical depressions of the season, Five-E, came ashore near Salina Cruz, Mexico, on the last day of June. Delores, Ignacio and Marty threatened the coast of Mexico, coming close enough to require tropical cyclone watches and warnings. Of these, Ignacio was also responsible for 40 injuries and 23 fatalities as the system passed just offshore of Lázaro Cárdenas. Public advisories were issued for four other systems due to the threat of heavy rain along the coast.
Tropical cyclone data was gathered at six hour intervals throughout the season. Even though most intensity assessments were estimates via the Dvorak Technique, there was a large research mission for tropical cyclogenesis in the Pacific. A NOAA research mission investigated Hurricane Jimena and gathered a few surface observations. Track forecasts were slightly more accurate than the past three years; intensity forecasts were comparable to the previous three seasons.
Systems
Tropical Storm Andres
On May 16, the first tropical depression of the season formed to the southwest of Baja California, out of a tropical disturbance that had developed during May 5 within the vicinity of Panama. During May 16 the depression gradually developed, before early the next day the National Hurricane Centre declared it a tropical storm and named it Andres. The newly named tropical cyclone reached its peak intensity of 60 mph (95 km/h), later that day. After maintaining its peak intensity for 24 hours, Andres started to gradually weaken as upper level windshear over the system increased before it dissipated during May 20. Throughout its life as a tropical cyclone, Andres moved very little and slowly executed a cyclonic loop, while remaining well away from any land.
Tropical Storm Blanca
A well organized tropical wave over West Africa entered the Atlantic Ocean on May 31. The wave never showed signs of organization while crossing the Atlantic. It emerged into the eastern north Pacific on June 10. It was not until June 13 when the convection associated with the wave became better organized. On June 14, Tropical Depression Two-E formed at a location about 515 mi (830 km) from Acapulco, Mexico.
For the next 48 hours, the depression moved toward the west and then northwest in response to a weakening ridge to the northwest. On June 17, the strong shear relaxed somewhat and the exposed center moved under the deep convection again. Thus, the depression strengthened into a tropical storm about 725 mi (1,165 km) south of the southern tip of Baja California. Tropical Storm Blanca experienced limited development, reaching its peak windspeed of 60 mph (95 km/h) early on June 20. Then, the center of Blanca became exposed again and weakened into a tropical depression on June 21. Finally, it dissipated on June 22 over colder waters about 1285 mi (2,380 km) southwest of the southern tip of Baja California. There were no casualties or damages attributed to this tropical cyclone.
Hurricane Carlos
A tropical wave moved off the coast of West Africa on June 4 showing some cyclonic curvature in the low clouds. It passed Barbados six days later, where a low-to-mid wind shift was detected. The wave was followed by a low level wind surge which was observed in Curaçao on June 12. Most of the shower activity associated with the wave moved westward over South America, and then over Panama on June 14. The convection became organized and developed into Tropical Depression Three-E on June 16 while it was located 350 mi (560 km) south of Salina Cruz. It became a tropical storm one day later. Carlos reached minimal hurricane strength on June 18. Two days later, Carlos was briefly downgraded to tropical storm status. A strong high pressure system forced Carlos to move over warmer waters and Carlos began to reintensify. Carlos regained hurricane status and developed a well-defined eye and excellent upper level outflow. On June 24, Carlos peaked at 955 mbar (28.2 inHg) central pressure and 115 mph (185 km/h) maximum sustained winds. The hurricane then weakened when it moved west over colder waters and encountered upper-level shear. Carlos dissipated on June 27. The National Hurricane Center received no reports of impact due to this tropical cyclone.
Hurricane Delores
Delores developed from a tropical wave which moved from Africa to the Atlantic on June 7. And it was not until June 22 when it gained organization and was identified as an area of disturbed weather south of Mexico.
The system immediately showed signs of rotation and it was designated Tropical Depression Four-E the same day. It was centered about 515 mi (830 km) south-southeast of Manzanillo, Mexico. Then, the depression reached storm strength, and was named Delores on June 24 while 145 mi (230 km) from the coast of Mexico. It rapidly intensified to a hurricane on June 25 as it approached to the coast. However it rapidly weakened and on June 27 it was downgraded to tropical storm status as it was moving over colder waters. Its deep convection gradually diminished and its west-northwestward motion abruptly halted as the system was being sheared. It weakened to a depression on June 28 near Socorro Island and it dissipated on June 29.
In response to Delores' approach, the Mexican government issued a tropical storm warning and a hurricane watch from Ixtapa to Manzanillo on June 24. The watch and the warning were dropped the next day. The cyclone remained far away enough that no reports of high winds were received. Satellite observations indicated that heavy rains fell in affected areas from June 23 to 26. However, no damages or casualties were reported.
Tropical Depression Five-E
A tropical disturbance south of the Gulf of Tehuantepec became better organized on June 29 and became a tropical depression. Strengthening was very limited as the depression was approaching land. It made landfall later that day very near Salina Cruz, Oaxaca. As it continued its west-northwest track, it dissipated inland after bringing torrential rains.
Five-E caused one fatality and some significant damage. Five-E destroyed up to 118 homes, injured 500, and also caused two people to go missing. Rainfall totals as high as 9.2 inches (230 mm) in 24 hours accompanied the depression over Southern Mexico.
Hurricane Enrique
Enrique formed from a westward-moving tropical wave that crossed the Atlantic from June 30 to July 8. A short-lived cyclonic circulation center within the wave was detected on satellite imagery when the system was over the eastern Atlantic. However, persistent deep convection did not occur until the wave neared the Gulf of Tehuantepec in the eastern Pacific Ocean on July 11. On July 12, the convection became more concentrated about 500 nmi (575 mi; 925 km) south of Acapulco, near a mid-level vortex within the wave; however, it had diminished the next day. On July 14, it became better organized. Based on reports from satellite imagery the low had developed into the season's sixth tropical depression on July 15. The depression intensified further and was upgraded to Tropical Storm Enrique the next day as it became better organized.
Enrique steadily intensified and by early on July 16, the National Hurricane Center was anticipating for the system to reach hurricane intensity. Continuing to strengthen, it reached hurricane status On July 17. However, this was for a short period of time as it developed an eye. Due to uncertainty in the storm's intensity that day, it is possible that it could have been a hurricane earlier than originally estimated. Wind shear associated with a trough and passage over cooler waters caused Enrique to begin weakening and the cyclone's center soon became exposed. Enrique was downgraded to a depression on July 19 and the weakening cyclone crossed into the central Pacific on July 20. The system persisted drifting northwestward for several days, while maintaining a well-defined, albeit weak, center of circulation. On July 27, after it passed well to the north of the Hawaiian Islands, Enrique managed to briefly re-intensify to tropical storm status, attaining a secondary peak intensity of 50 mph (85 km/h), while completing a clockwise loop. As Enrique headed toward the Midway Island, increased wind shear weakened the system, causing another downgrade to depression status. As the storm approached the International Dateline, the system started to restrengthen. Shortly after crossing the dateline, Enrique became a tropical storm again on August 1. It lasted for less than 24 hours before it lost its convection and thus the cyclone began to dissipate. No damages or casualties were caused by Enrique.
Hurricane Fefa
A westward-moving tropical wave exited the coast of Africa on July 17. It tracked the Atlantic and Caribbean without development, and crossed Central America into the eastern Pacific on July 25. The cloud pattern and convection began to become better organized on July 28, and a day later it developed into Tropical Depression Seven-E while located about 975 miles (1,569 km) south-southeast of Cabo San Lucas. Located over warm waters with fair upper-level outflow, the depression intensified into Tropical Storm Fefa twelve hours after forming. Fefa developed a curved cloud band over the southern and eastern portion of the center. Steered by a ridge to its north, Fefa moved to the west-northwest and slowly strengthened, becoming a hurricane on July 31. A large, ragged eye developed the next day, and Fefa reached peak winds of 120 mph (190 km/h) on August 2. After peaking, Fefa encountered cooler waters and drier air, causing it to weaken as it turned more to the west. On August 4, Fefa restrengthened after crossing over warmer waters, reaching a secondary peak intensity of 105 mph (169 km/h). Increasing wind shear caused the hurricane to weaken again. Fefa crossed into the central Pacific on August 5, and weakened into a tropical storm the next day while moving toward Hawaii. Late on August 7, Fefa weakened to a tropical depression a short distance of the island of Hawaii. Early on August 8, the depression degenerated into a tropical wave after moving onshore. The remnants tracked west-northwestward and passed south of the Hawaiian Islands until dissipating on August 9 to the northwest of Kauai.