The 2016 Pacific hurricane season was tied as the fifth-most active Pacific hurricane season on record, alongside the 2014 season. Throughout the course of the year, a total of 22 named storms, 13 hurricanes and six major hurricanes were observed within the basin. Although the season was very active, it was considerably less active than the previous season, with large gaps of inactivity at the beginning and towards the end of the season. It officially started on May 15 in the Eastern Pacific (north of the Equator and east 140°W), and on June 1 in the Central Pacific (from 140°W to the International Date Line); they both ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in these regions of the Pacific Ocean. However, tropical development is possible at any time of the year, as demonstrated by the formation of Hurricane Pali on January 7, the earliest Central Pacific tropical cyclone on record. After Pali, however, no tropical cyclones developed in either region until a short-lived depression on June 6. Also, there were no additional named storms until July 2, when Tropical Storm Agatha formed, becoming the latest first-named Eastern Pacific tropical storm since Tropical Storm Ava in 1969.
Hurricane Darby brushed the Hawaiian islands as a tropical storm causing only minor damage; while hurricanes Lester and Madeline also threatened to make landfall in Hawaii but weakened significantly before approaching the islands. Tropical Storm Javier and Hurricane Newton both made landfall in Mexico, with the latter being responsible for at least nine fatalities as it came ashore near Baja California Sur. Hurricane Ulika was a rare and erratic storm which zig-zagged across 140°W a total of three times. Hurricane Seymour became the strongest storm of the season, forming in late October. Finally, in late November, Hurricane Otto from the Atlantic made an unusual crossing over Central America, emerging into the East Pacific as a moderate tropical storm but dissipated shortly after. Damage across the basin reached $95 million (2016 USD), while 11 people were killed by Celia and Newton overall.
Seasonal forecasts
On May 6, 2016, the Servicio Meteorológico Nacional (SMN) issued its first outlook for the Pacific hurricane season, forecasting a below average season with 10 named storms, 7 hurricanes, and 3 major hurricanes. On May 27, NOAA released their outlook, forecasting 13-20 named storms, 6-11 hurricanes, and 3-6 major hurricanes. NOAA admitted that this season would be difficult to predict because of changing conditions, but both organizations cited a dissipating El Niño and the formation of a La Niña event, which resulted in the prediction of a near-normal season in both basins. In the Central Pacific, about four to seven cyclones would form or enter within the basin, citing an equal 40% chance of an above-normal or near-normal season.
Seasonal summary
The accumulated cyclone energy (ACE) index for the 2016 Pacific hurricane season as calculated by Colorado State University using data from the National Hurricane Center was 184.9 units.
As the new year began, Pali formed on January 7, in the central Pacific, two days before the date Tropical Storm Winona formed in 1989. Pali subsequently surpassed Hurricane Ekeka's record as the earliest hurricane on January 11. When Pali reached a peak intensity of 100 mph, it surpassed Winona to become the strongest January tropical cyclone east of the International Date Line.
In the eastern Pacific, no tropical depressions or storms formed during the month of May for the first time since 2011, and then, no named storms formed during June for the first time since 2007. When Agatha formed on July 2, it became the latest first named storm on record in the eastern Pacific proper since 1969. Despite this, the season set a record for the most number of storms during the first half of July. When Georgette formed on July 21, it became the seventh named storm to form in the month of July; equaling the previous record set in 1985 and 2015 for the most active July since reliable records began. And when Frank became a hurricane (after Georgette did so), it marked a record-high 5 hurricanes in July. Finally, Howard formed on July 31, however, was not named until August 1, one named storm shy of the record. Despite that, the season tied the record set in 1985 with the most named storms in July. Activity in August was slightly less active than July. Lester and Madeline threatened the Big Island at hurricane strength. Lester passed north of the islands, Madeline brought some rain as the storm dissipated south of Hawaii. Javier and Newton followed similar paths close to the Mexican coast, with both making landfall in the Baja California Peninsula in August and early September respectively. After Newton led off September; Hurricanes Orlene, Paine and Tropical Storm Roslyn followed forming far from land. Hurricane Ulika became the first tropical cyclone on record to cross 140°W three times. It formed and was designated a tropical depression in the eastern Pacific, but did not develop into a tropical storm until after entering the central Pacific, where, like Pali, it was named from the basin's Hawaiian language lists of names. After an unusually quiet October, Hurricane Seymour became the sixth major hurricane of the season, as well as the strongest. Tropical Storm Tina formed close to the coast of Mexico in mid-November. In late November, Tropical Storm Otto entered the basin from the Atlantic, becoming only the eighteenth cyclone to do so; however, it dissipated quickly due to unfavorable conditions.
Systems
Hurricane Pali
A powerful and long-lived westerly wind burst—a feature commonly associated with strong El Niño events—spurred cyclogenesis within a persistent low-latitude, west-to-east oriented surface trough, resulting in the formation of an area of low pressure on January 6. Fueled by unusually high sea surface temperatures, estimated at 29.5 °C (85.1 °F), the system gradually coalesced into a tropical depression on January 7. A ridge aloft centered directly overhead the system enhanced its poleward outflow, enabling the development of deep convection around its center, which soon strengthened into a tropical storm receiving the name Pali, becoming the earliest such system in the northeastern Pacific on record. Pali continued intensifying through the first half of January 8 and nearly reached hurricane strength, but easterly vertical wind shear caused by the ridge disrupted its center, causing it to start weakening and move northwestward. Steady weakening continued through January 9 as Pali's deep convection was displaced to the west of its low-level center and intermittently pulsed, later leading to a dramatic decrease in intensity. By the end of that day, Pali barely maintained tropical storm strength, and the lack of persistent deep convection permitted it to be less affected by the easterly wind shear, causing its forward motion to decrease significantly. As the ridge weakened and retreated southward on January 10, causing vertical wind shear to gradually diminish, Pali started re-intensifying, with persistent deep convection redeveloping near its center and within its western quadrant. On January 11, the ridge passed directly over Pali, leading to the reestablishment of poleward outflow and eventual development of southwesterly flow, enabling its convection to slowly increase in coverage and organization within all quadrants and establishing a northeastward movement.
On January 12, light vertical wind shear and high sea surface temperatures enabled Pali to strengthen into a Category 1 hurricane. Later that day, Pali strengthened further into a Category 2 hurricane while travelling southwards, reaching its peak intensity. During the next few days, Pali rapidly weakened while turning back towards the south-southeast, due to steady increases in southerly vertical wind shear and loss of Coriolis force. Further decay in the organization of deep convection made Pali being downgraded into a remnant low late on January 14. While weakening, Pali reached a minimum latitude of 2.6°N, making it the second-lowest latitude tropical cyclone on record in the Western Hemisphere, behind Tropical Depression Nine-C which attained a minimum latitude of 2.2°N just two weeks prior. Pali completed a broad and looping track, by dissipating approximately 50 nmi (58 mi; 93 km) from where it initially developed. Unrelated to Pali, Hurricane Alex developed over the Atlantic during the last few days of Pali's existence. This marked the first known occurrence of simultaneous January tropical cyclones between the two basins.
Hurricane Pali had severe impacts in Kiribati. Pali's storm surge caused major coastal flooding, with the island nation reporting significant property damage. Pali also caused a cargo ship to run aground on the coast of Kiribati, killing four people.
Tropical Depression One-E
On June 4, the National Hurricane Center began monitoring an area for possible development. Over the next few days, the chances of the storm forming were low. Unexpectedly, however, on June 6, advisories began to be issued on Tropical Depression One-E. This led the Government of Mexico to issue a Tropical Storm Watch for its coast. On June 7, the watch was removed as the storm weakened slightly. Early on June 8, the storm made landfall in Mexico near the Gulf of Tehuantepec and dissipated.
As a precautionary measure, temporary shelters were opened across Chiapas. The depression caused minor damage across Oaxaca, primarily within the Salina Cruz municipality. Heavy rains led to some street flooding and a sinkhole that damaged one home.
Tropical Storm Agatha
On June 30, the National Hurricane Center began to monitor an area for possible formation. On July 1, organization unexpectedly increased. Seven hours later, early on July 2, the tropical disturbance strengthened into Tropical Depression Two-E. The system quickly organized, and later that day, the NHC upgraded Two-E into Tropical Storm Agatha. Agatha slightly strengthened to peak intensity on July 3. Winds topped off at 50 mph. Soon after, Agatha weakened slightly, with winds lowering to 40 mph later that day. The storm continued westwards over the next two days. Early on July 5, Agatha became post-tropical.
Hurricane Blas
On June 27, the NHC began to monitor a tropical wave moving over Central America for possible development. A low-pressure area formed south of Mexico on June 30, and early on July 3, the storm gained enough organization to be designated Tropical Depression Three-E. Six hours later, amid a favorable environment with warm sea surface temperatures and decreasing vertical wind shear, it intensified into Tropical Storm Blas. Steady strengthening ensued, and Blas intensified into a hurricane on July 4. Intensification stalled for the remainder of that day as dry air wrapped into the circulation; however, Blas began to rapidly deepen on July 5, and it became the first major hurricane of the season that evening. Blas quickly reached peak intensity at Category 4 strength on July 6. Blas weakened to a Category 3 hurricane soon after, before transitioning into an annular tropical cyclone and maintaining intensity. However, Blas soon passed over decreasing sea surface temperatures, resulting in a slow weakening trend; Blas weakened below major hurricane status late on July 7, and down to a Category 1 hurricane by the next day. Blas further degraded to a tropical storm on July 9, as weakening accelerated amid a stable air mass and increasing southwesterly shear. Over sea surface temperatures of 24 °C (75 °F), Blas weakened to a tropical depression on July 10, and degenerated into a post-tropical cyclone soon after.
Moisture associated with the remnants of Blas brought showers to Hawaii. Peak daily rainfall totals primarily ranged between 1 and 2 in (25 and 50 mm) and did not cause any serious flooding.
Hurricane Celia
On June 27, the NHC began monitoring a tropical wave over Central America. The wave entered the East Pacific the following day, eventually gaining sufficient organization to be declared a tropical depression by 21:00 UTC on July 6. The newly formed cyclone initially struggled to intensify with upwelling resultant from Hurricane Blas, but a formative central dense overcast and several spiral bands prompted an upgrade to Tropical Storm Celia by 15:00 UTC on July 8. Celia began to intensify after moving into warmer waters, obtaining Category 1 hurricane intensity by 21:00 UTC on July 10 and peaking as a Category 2 hurricane with winds of 100 mph (160 km/h) the next afternoon. Thereafter, progressively cooler waters caused the system to weaken: it fell below hurricane intensity by 09:00 UTC on July 13, weakened to a tropical depression by 21:00 UTC on July 15 after entering the Central Pacific, and degenerated into a remnant low well east-northeast of Hawaii six hours later.
Although the remnants of Celia passed north of Hawaii, it disrupted the typical trade winds, resulting in higher humidity across the island group and brief but heavy showers over central Oahu and the windward slopes of Maui and the Big Island on July 18. Precipitation totals ranged form 1 to 2.5 in (25 to 65 mm), prompting flash flood advisories. In addition to the rain, large swells as high as 15 ft (4.6 m) generated by Celia and its remnants affected the east-facing shores of the Hawaiian Islands. resulting in high surf advisories. These swells produced rough surf that caused two drowning deaths on the southeastern shore of the island of Oahu on July 16.