Hurricane Willa was a powerful tropical cyclone that brought torrential rains and destructive winds to southwestern Mexico, particularly the states of Sinaloa and Nayarit, during late October 2018. It was the twenty-fifth tropical cyclone, twenty-second named storm, thirteenth hurricane, tenth major hurricane, and record-tying third Category 5 hurricane of the 2018 Pacific hurricane season. Willa was the first major hurricane to make landfall in the Mexican state of Sinaloa since Lane in 2006.
Willa originated from a tropical wave that the United States-based National Hurricane Center (NHC) began to monitor for tropical cyclogenesis in the southwestern Caribbean Sea on October 14. However, the system subsequently crossed over Central America into the East Pacific, without significant organization. The NHC continued to track the disturbance until it developed into a tropical depression on October 20, off the coast of southwestern Mexico. The depression strengthened into Tropical Storm Willa later in the day as a period of rapid intensification commenced. Willa peaked as a Category 5 hurricane with sustained winds of on the following day. Afterward, a combination of an eyewall replacement cycle and increasing wind shear weakened the hurricane, and early on October 24, Willa made landfall as a marginal Category 3 hurricane in the Mexican state of Sinaloa. Following landfall, Willa rapidly weakened, dissipating later that day over northeastern Mexico.
Up to its landfall, Willa prompted the issuance of hurricane and tropical storm watches and warnings for western Mexico. The hurricane killed nine people, and caused Mex$16.2 billion (US$825 million) in damage, mostly around the area where it moved ashore. The storm knocked out power to nearly 100,000 people in four states. Willa caused significant damage to many schools, a hospital, and infrastructure in the city of Escuinapa, with totals estimated at Mex$6 billion (US$306 million). The overflow of multiple rivers damaged structures and left many areas in Sinaloa and Nayarit without a supply of potable water. In the surrounding states, flooding and landslides were the main sources of damage and injury. The remnants of Willa later entered the United States and caused flash floods in Texas. After the storm, multiple individuals did not receive direct help from the Mexican government until many months had passed. The victims mainly relied on help from charitable organizations to recover and rebuild their damaged property. The Sinaloa state government delivered rotten mattresses to storm victims and the federal government lost track of funds it had appropriated for relief efforts. Reconstruction was not slated to begin in some areas until a few months after the storm.
Meteorological history
The origins of Hurricane Willa can be traced back to a tropical wave that left the west coast of Africa on October 2, 2018. Over the next few days, the wave produced intermittent bursts of deep convection, or thunderstorms; however, strong wind shear blasted the convection away from the center while the wave traveled westward across the Atlantic Ocean. On October 14, the United States-based National Hurricane Center (NHC) began monitoring the wave for tropical development while it was located in the southwestern Caribbean Sea. On the next day, the system became better organized southeast of the Yucatán Peninsula, and the storm encountered more favorable conditions as it neared land. As a result, a WC-130 aircraft from the United States Air Force Reserve 53rd Weather Reconnaissance Squadron was scheduled to survey the system for further development. However, the wave made landfall in Belize on October 16, hindering further organization.
The tropical wave moved into the East Pacific early on October 17; however, the system failed to coalesce into a tropical cyclone, and became increasingly disorganized and elongated on the next day. A new low-pressure trough, an elongated region of low atmospheric pressure, developed to the east of the original low early on October 19, which organized into Tropical Storm Vicente later that day. The original low to the west gradually organized while moving westward, and at 00:00 UTC on October 20, the system developed into a tropical depression while located approximately south of Manzanillo, Colima, Mexico. Banding featuressignificantly elongated, curved bands of rain cloudsbegan to develop south of the center, while cloud tops west of the center became as cold as . The system then developed a tight inner core, strengthening into a tropical storm around 12:00 UTC, while located about south-southwest of Manzanillo. At this point, the NHC assigned it the name Willa from its rotating list of names.
Shortly thereafter, Willa began to rapidly intensify, with its low-level center becoming embedded beneath a central dense overcast, which is the large area of thunderstorms surrounding the storm's circulation center. At the same time, Willa turned towards the northwest as it began traveling around the western edge of a mid-level ridge. Environmental conditions around the cyclone and aloft were favorable, with very low wind shear, high levels of moisture, and sea surface temperatures of . These conditions allowed Willa to strengthen into a hurricane around 06:00 UTC on October 21. Around the storm, outflow became well-established, and in the center of the convection, a small eye developed. Willa reached Category 3 status by 18:00 UTC, with its eye becoming well-defined on both infrared and satellite imagery, making it the tenth major hurricane of the season. Continuing to rapidly intensify, Willa reached peak intensity as a Category 5 hurricane with maximum sustained winds of and a minimum central pressure of at approximately 06:00 UTC on October 22, while located about south-southwest of Cabo Corrientes, Mexico. This capped off a 48-hour period in which Willa's winds increased by . Over the next few days, Willa recurved towards Mexico; the system turned to the north as it rounded the edge of the ridge and later to the northeast due to an approaching mid-to-upper-level trough.
Shortly after Willa reached peak intensity, microwave satellite imagery detected the presence of an outer eyewall, indicating that Willa was beginning to undergo an eyewall replacement cycle. Willa also began to interact with the smaller Tropical Storm Vicente to the southeast at about this time. Despite a favorable environment, Willa began to weaken due to the eyewall replacement cycle, with the storm's eye becoming cloud-filled; Willa weakened to Category 3 strength on October 23 around 06:00 UTC, as southwesterly wind shear began to increase. The weakening trend abated as the eyewall replacement cycle ended, and Willa's eye passed over Isla San Juanito and Isla María Madre at approximately 17:45 UTC. The system made landfall as a Category 3 hurricane near , Sinaloa, at 01:20 UTC on October 24 (7:20 PM MDT on October 23), with 1-minute sustained winds of and a minimum central pressure of . This made it the first Pacific major hurricane to strike Mexico since Hurricane Patricia in 2015, and the first landfalling major hurricane in Sinaloa since Hurricane Lane in 2006. Willa's eye soon faded away on satellite imagery as it progressed inland. Following landfall, mountainous terrain and southwesterly wind shear took a toll on the storm's strength, and Willa rapidly weakened, degenerating into a tropical storm by 06:00 UTC. Six hours later, Willa dissipated over northeastern Mexico, with the mid- and upper-level circulations decoupling from the lower-level circulation. The remnants of Willa continued to travel northeastward, bringing rain to multiple states in the United States. Energy from the remnants contributed to the formation of a nor'easter in the eastern United States.
Preparations
The Government of Mexico issued a hurricane watch on October 21 at 15:00 UTC for the western coast of Mexico from San Blas to Mazatlán, and a tropical storm watch from Playa Perula to San Blas. Six hours later, a tropical storm watch was issued for Mazatlán to . The hurricane watch and tropical storm watches were replaced with warnings at 03:00 UTC on October 22. All warnings were discontinued at 06:00 UTC on October 24 after Willa weakened to a tropical storm over Durango.
Various other weather-related alerts were issued as Willa approached Mexico's Pacific coast. Red alerts, indicative of the maximum level of danger, were issued for portions of Nayarit and Sinaloa in Willa's direct path. In central Sinaloa and Puerto Vallarta, Jalisco, orange alerts were issued due to high danger. A majority of Chihuahua was under a yellow alert, meaning moderate danger, due to the threat of heavy rainfall. A green alert, signaling minimal danger, was issued for Baja California Sur as a precautionary measure due to waves along the coast. Admiral Vidal Francisco Soberón Sanz of the Mexican Secretariat of the Navy activated the Prevention Phase of the Marine Plan, a military disaster preparation and relief plan, in the states of Sonora, Sinaloa, Nayarit, Jalisco, Colima, and Michoacán. Small vessels were restricted in the ports of Comondú, La Paz, and Los Cabos as well as in the Gulf of California and Sea of Cortez. Classes were canceled in the Sinaloan municipalities of Concordia, Cosalá, Elota, Escuinapa, Mazatlán, Rosario, and San Ignacio. Approximately 1,265 schools were also closed along the northern and southern coasts of Jalisco.
Approximately 200,000 people were evacuated from their homes in Nayarit and Sinaloa. About 40,000 of those people utilized more than 2,900 shelters, assisted by the Mexican Army, Navy, and emergency crews. Businesses and industries in the storm's path closed. Mazatlán International Airport closed during the storm, as did nearby hotels. Thirty neighborhoods in the municipality of Mazatlán were evacuated due to the risk of flooding. Emergency authorities evicted over 4,250 people in coastal cities from their homes and established 58 shelters before the storm hit. In Jalisco, 2,500 people were evacuated ahead of Willa and 23 temporary shelters were established. At least 6,000 people were evacuated from Escuinapa due to the proximity of Willa. Fonden, Mexico's natural disaster relief agency, allocated 99.2 US tons (90 metric tons) of food for affected people in advance of Willa's landfall. The Mexican Navy set up a collection center for food and supplies in La Paz, Baja California Sur, in the hours before the storm.
Hurricane Willa and Tropical Storm Vicente together forced the Norwegian Bliss cruise ship to divert to San Diego, California, on October 23. Despite the threat that Willa posed, Petróleos Mexicanos, the state-owned petroleum company, announced that it intended to maintain normal operations in Jalisco, Nayarit, Colima, Sonora and Sinaloa. All economic activity and public transportation were suspended in Sinaloa as a precaution. Roads and businesses were closed in Nayarit, with officials requesting that citizens remain in their homes. In order to prevent damage to water pumping equipment during the storm, service was shut off to 27 neighborhoods in Tepic, Nayarit, on October 23. The Jalisco state Ministry of Communications and Transportation (SCT) employed 400 people to observe 322 bridges and over of roads. The SCT also readied 60 machines, including backhoes, in case of landslides. The number of road crews available was increased from 22 to 40 during the storm.
Impact Mexico
The eye of Hurricane Willa crossed over two of the offshore Islas Marías, producing wind gusts of , and average sustained winds of for a 15-minute period; the latter value equated to 1-minute sustained winds of around . The Marías Islands Prison was damaged during the storm; palm trees were uprooted, roofs collapsed, and barbed wire was ripped from fences.