Hurricane Hernan (2008)

The 2008 Pacific hurricane season was a near-average Pacific hurricane season which featured seventeen named storms, though most were rather weak and short-lived. Only seven hurricanes formed and two major hurricanes. This season was also the first since 1996 to have no cyclones cross into the central Pacific. The season officially began on May 15 in the East Pacific Ocean, and on June 1 in the Central Pacific; they ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Pacific basin. However, the formation of tropical cyclones is possible at any time of the year. Despite this, no tropical cyclones formed outside the usual limits of the season.

Several storms affected land this year. Tropical Storm Alma made landfall along the Pacific coast of Nicaragua, becoming the first known storm to do so. It killed 9 and caused over US$35 million in damage (value in 2008). Hurricane Norbert became the strongest hurricane to hit the western side of the Baja Peninsula on record, killing 25 and causing widespread damage over Baja California Sur, Sonora, and Sinaloa in Mexico. Tropical Depression Five-E made landfall along the south-western Mexican coastline in July 2008, producing heavy rainfall in parts of southwestern Mexico, which these rains triggered flooding that killed two people and left roughly $2.2 million in damages. Julio produced lightning and locally heavy rainfall, which left more than a dozen communities isolated due to flooding. The flooding damaged several houses and killed two people. Lowell left $15.5 million in damage as it made landfall in Baja California Peninsula as a tropical depression, and affected parts of West Coast and the Gulf Coast. Odile dumped squally rainfall on Central America as a tropical wave, while it brought heavy rainfall across southern Mexico.

Seasonal forecasts

On May 16, 2008, the Servicio Meteorológico Nacional posted their outlook for the 2008 Pacific hurricane season, forecasting 15 named storms, 7 hurricanes, and 2 major hurricanes. Three days later, the National Oceanic and Atmospheric Administration's Central Pacific Hurricane Center released their forecast for the central Pacific, predicting three or four tropical cyclones to form or cross into the basin; an average season sees four or five tropical cyclones, of which two further intensify into hurricanes. On May 22, meanwhile, the Climate Prediction Center released their outlook, forecasting a 70 percent probability of a below-average year, a 25 percent chance of a near-average year, and only a 5 percent chance of an above-average year. The organization predicted 11–16 named storms, 5–8 hurricanes, 1–3 major hurricanes, and an accumulated cyclone energy (ACE) index 40–100 percent of the long-term median. All three groups cited the effects of the ongoing La Niña, as well as the continuation of a multi-decadal decline in Pacific hurricane activity, as their reasoning behind the below-average forecasts.

Seasonal summary

The accumulated cyclone energy (ACE) index for the 2008 Pacific hurricane season as calculated by Colorado State University using data from the National Hurricane Center was 83.8 units. Broadly speaking, ACE is a measure of the power of a tropical or subtropical storm multiplied by the length of time it existed. It is only calculated for full advisories on specific tropical and subtropical systems reaching or exceeding wind speeds of .

The activity of the season was relatively quiet overall, with 16 named storms, 7 hurricanes, 2 major hurricanes; 1 tropical storm formed in the Central Pacific. The main contributing factor to a slower season was the 2007–08 La Niña event in the equatorial Pacific; although cold ocean temperature anomalies dissipated during the early summer of 2008, a La Niña-like atmospheric circulation persisted. This led to anomalously strong easterly wind shear across the East Pacific, hindering the intensification of most tropical cyclones. In addition, water temperatures across the basin were cooler than in years past, though still near the long-term average.

The first storm of the year, Alma, developed on May 29 farther east than any other East Pacific cyclone in recorded history, not including storms that originated in the Atlantic and continued into the basin. Later that day, it made landfall on the Pacific coast of Central America, the first cyclone to do so since the 1949 Texas hurricane. June and July saw near average tropical cyclone activity, while August was a below-average month overall. September 2008 was the quietest since reliable records began in 1971, with a monthly ACE index only 9 percent of average. In terms of ACE, seasonal activity ended about 75 percent of the long-term median.

Systems

Tropical Storm Alma

A nearly stationary trough of low pressure formed over the extreme eastern Pacific in late May, and the system organized into a tropical depression around 00:00 UTC on May 29, becoming the easternmost-forming tropical cyclone on record in the basin. The newly formed system intensified into a tropical storm six hours later, earning the name Alma, and attained peak winds of around 18:00 UTC as an eye-like feature became apparent on satellite. Moving northward, Alma made landfall near León, Nicaragua, at that strength before rapidly weakening inland. Its low-level circulation dissipated over the mountains of western Honduras around 18:00 UTC on May 30, but remnant convective activity aided in the formation of Tropical Storm Arthur in the western Caribbean a day later.

Alma produced devastating rainfall across Central America, with peak accumulations of 14.82 in (376.4 mm) in Quepos, Costa Rica. The nearby cities of Guanacaste and Puntarenas were most heavily affected with over 1,000 homes damaged, of which over 150 were destroyed. Throughout all of Costa Rica, more than 100 roads and bridges were damaged, leaving several communities isolated for several days. In Nicaragua, the departments of León and Chinandega saw approximately 200 homes damaged; across Honduras, an additional 175 homes were adversely impacted. Six people died in Honduras: a young girl who was swept away by a fast-moving river and five people who perished following the crash of TACA Flight 390. Two more deaths occurred in Nicaragua due to electrocutions from downed power lines, and one death occurred offshore when a fishing vessel sank. Nine people on boats went missing in the wake of the cyclone.

Hurricane Boris

A westward-moving tropical wave departed the western coast of Africa on June 14 and entered the eastern Pacific a week later. A broad surface low formed in association with the feature south of the Gulf of Tehuantepec on June 23, and its organization led to the development of a tropical depression around 06:00 UTC on June 27. The cyclone only slowly organized in a moderate wind shear regime, becoming Tropical Storm Boris six hours later and remaining fairly steady state for a few days thereafter. Shear lessened on June 29, allowing Boris to attain hurricane intensity two days later as an eye developed. This feature was temporarily eroded late on July 1, but reappeared by 06:00 UTC on July 2 when the cyclone attained peak winds of . Cold waters and a more stable environment then prompted rapid weakening, and Boris ultimately degenerated to a remnant low by 12:00 UTC on July 4. The post-tropical cyclone continued westward until dissipating early on July 6.

Tropical Storm Cristina

The season's third tropical depression developed around 18:00 UTC on June 27 from a tropical wave that crossed Central America four days prior. In an environment of low shear but abundant dry air and marginal ocean temperatures, the depression intensified into Tropical Storm Cristina around 12:00 UTC on June 28 before attaining peak winds of six hours later. The cyclone moved west-northwest and then west as high pressure expanded to its north. Abundant dry air and stronger upper-level winds capped the storm's organization to intermittent, amorphous bursts of convection that eventually dissipated, and Cristina degenerated to a remnant low around 18:00 UTC on June 30. The low turned southward before dissipating on July 3.

Tropical Storm Douglas

An organized tropical wave departed the western coast of Africa on June 19 and reached the waters south of the Gulf of Tehuantepec late the next week. The system steadily congealed into a tropical depression by 18:00 UTC on July 1. Paralleling the coastline of southwestern Mexico, the depression intensified into Tropical Storm Douglas and attained peak winds of around 12:00 UTC the next morning, despite the effects of strong northeasterly wind shear. As upper-level winds increased further and Douglas tracked northwest into cooler waters, it began a weakening trend that ended in its degeneration to a remnant low around 06:00 UTC on July 4. The low turned west within low-level flow and dissipated two days later.

Due to the proximity to land, outer rain bands associated with Douglas produced tropical storm force winds in Manzanillo, Mexico. Minor flood damage was reported along the coastline in Colima, Jalisco, and Nayarit. Due to the proximity to land, the outer bands of Douglas produced tropical storm force winds in Manzanillo, Mexico. Minor flooding was reported along the coastline in Colima, Jalisco, and Nayarit. Moisture associated with Douglas produced light rain over parts of Baja California Sur, with heavier amounts in Todos los Santos.

Tropical Depression Five-E

A tropical wave departed the western coast of Africa on June 23 and began steady organization after entering the eastern Pacific over a week later. The system acquired sufficient organization to be declared a tropical depression around 18:00 UTC on July 5 and embarked on a northwesterly course parallel to the coastline of Mexico. The following day, however, a weakening mid-level ridge to its north directed the cyclone more poleward. Strong easterly wind shear prevented the formation of banding features while keeping the overall cloud pattern disorganized, and the depression moved ashore near Lázaro Cárdenas, Michoacán, early on July 7 without attaining tropical storm intensity. It dissipated over the mountainous terrain a few hours later.

The tropical depression produced of rain in Manzanillo, with other locations also experiencing isolated rainfall. Cerro de Ortega, Colima reported of rain in a 24-hour period. The community of Ometepec reported . Other locations reported moderate rainfall, ranging around . One person was swept away by flood waters, reaching in depth. Heavy rains from the depression resulted in a traffic accident that killed one person and injured two others. In all, damages from the storm amounted to MXN 30 million ($2.2 million).

Hurricane Elida

A tropical wave, indistinguishable in the Atlantic basin, crossed the coastline of Central America on July 8 and organized into a tropical depression three days later around 18:00 UTC. With a mid-level ridge extending from the Gulf of Mexico into western Mexico, the newly formed cyclone moved west-northwest within an increasingly favorable environment, intensifying into Tropical Storm Elida by 06:00 UTC on July 12 and becoming the season's first hurricane around 12:00 UTC on July 14. An abrupt increase in wind shear briefly weakened the storm the next day, but by 18:00 UTC on July 16, the formation of an eye within Elida's round central dense overcast showcased its peak as a Category 2 hurricane with winds of . The system then tracked into cooler waters and stronger upper-level winds, causing it to fall below hurricane intensity by 06:00 UTC on July 18 and degenerate to a remnant low early the next morning, although it maintained a well-defined circulation. The low ultimately dissipated well east-southeast of Hawaii by 00:00 UTC on July 22.

Due to the proximity of Elida to Mexico, the Government of Mexico warned residents about the possibility of heavy rains from the outer edges of the storm. Thunderstorms related to Elida developed over Oaxaca, Guerrero, Michoacán, Colima and Jalisco. In Nayarit, Elida produced storms that dropped torrential rainfall and hail that injured at least one person. The rainfall resulted in the formation of a lake roughly deep. Several trees feel, blocking streets for several hours. Street flooding reached a depth of , inundating shops and some homes. Indirect effects, such as large swells, were felt along the Mexican coastline as the storm produced waves up to . However, as trade winds increased during the middle of July, the remnants of Elida brought rainfall to east-facing slopes of the Island of Hawaii and Maui. Frequent rain showers produced of precipitation in those regions, but no significant flooding occurred.

Hurricane Fausto

A tropical wave exited western Africa on July 4, which moved westward across the Atlantic without development. It entered the eastern Pacific on July 12 and began to show signs of development the next day. On July 16, the system organized into Tropical Depression 7E, located about southeast of Acapulco, Mexico. Steered by a ridge to the north, the system moved generally northwestward throughout its duration. With thunderstorms located around the circulation amid moderate wind shear, the depression quickly intensified into Tropical Storm Fausto. As a large cyclone, Fausto slowly intensified, with relaxing wind shear and warm waters. Although the circulation was occasionally exposed from the thunderstorms, a banding eye feature began to develop on July 18. Fausto attained hurricane status later that day. On July 20, Fausto attained peak winds of and a minimum pressure of 977 mbar (hPa; ). Around that time, the hurricane passed between the islands of Clarion and Socorro. Cooler waters caused Fausto to weaken, diminishing convective activity. On July 21, the hurricane weakened to a tropical storm, and further to a tropical depression the next day. With little or no remaining convection, the system degenerated into a remnant low-pressure area as it traveled towards the west-northwest. The remnants of Fausto dissipated on July 24, while located about 1,065 mi (1,715 km) west of Cabo San Lucas.

The outer bands