Hurricane Willa was the strongest tropical cyclone to make landfall in the Mexican state of Sinaloa since Lane in 2006. The twenty-second named storm, thirteenth hurricane, tenth major hurricane, and record-tying third Category 5 hurricane of the 2018 Pacific hurricane season, Willa originated from a tropical wave that the National Hurricane Center (NHC) first began monitoring for tropical cyclogenesis in the southwestern Caribbean Sea, on October 14. 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. Later in the day, the system became a tropical storm as it began to rapidly intensify. On October 21, Willa became a Category 4 major hurricane, before strengthening further to Category 5 intensity on the next 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 Sinaloa of the northwestern Mexico. Following landfall, Willa rapidly weakened, dissipating later on the same 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 six people, and caused $536.8 million (2018 USD) in damages, mostly around the area where it moved ashore, becoming the sixth-costliest Pacific hurricane on record.
Willa's origins can be traced back to a tropical wave that departed from the west coast of Africa on October 2. Over the next few days, the wave produced intermittent bursts of deep convection near a well-defined mid-level circulation center; however, the convection was soon sheared away by strong vertical wind shear from the west and southwest as the system traveled westward at a speed between 15–20 kn (17–23 mph; 28–37 km/h). On October 14, the 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; a Hurricane Hunter aircraft was scheduled to survey the system for further development. However, organization was hindered as the system quickly made landfall in Belize on the next day. Early on October 17, the tropical wave moved into the East Pacific and quickly organized; however, the system failed to coalesce into a tropical cyclone and became increasingly disorganized and elongated on the next day. Early on October 19, a new low-pressure trough developed to the east of the original low, 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 265 mi (425 km) south of Manzanillo, Mexico. At that time, the NHC noted that banding features had begun to develop south of the center and that the system had very cold cloud top temperatures of −85 to −91 °C (−121 to −132 °F). Around 12:00 UTC, the system strengthened into a tropical storm and was assigned the name Willa while located about 290 mi (465 km) south-southwest of Manzanillo. The NHC stated that outer banding features had increased and that the system had developed a tight inner core.
Soon after its genesis, Willa began to rapidly intensify, with its low-level center becoming embedded beneath a central dense overcast. At the same time, Willa turned towards the northwest as it began traveling around the western edge of a mid-level ridge. Environmental conditions under the cyclone and aloft were favorable, with very low wind shear, high levels of moisture, and sea surface temperatures of 29 °C (84 °F). Around 06:00 UTC on October 21, Willa strengthened into a hurricane. The system developed an intermittent pinhole eye in the center of its convection as outflow became well-established. Twelve hours later, the NHC upgraded Willa to Category 3 status after its eye had become well-defined on both infrared and satellite imagery, making it the tenth major hurricane of the season. At approximately 06:00 UTC on October 22, Willa reached peak intensity with maximum sustained winds of 160 mph (260 km/h) and a minimum central pressure of 925 mbar (27.3 inHg) while located about 195 mi (315 km) south-southwest of Cabo Corrientes, Mexico. At that time, the NHC stated that Willa's winds had increased by 110 knots, with the system strengthening from a tropical depression to a Category 5 hurricane in 48 hours.[nb 1] 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 ongoing structural changes, with the storm's eye becoming cloud-filled. On October 23 at 06:00 UTC, Willa weakened to Category 3 as southwesterly wind shear was increasing. The weakening trend abated as the eyewall replacement cycle ended; Willa remained a low-end Category 3 hurricane as it approached Mexico. At approximately 17:45 UTC, Willa's eye passed over Isla San Jaunito and Isla María Madre, with 15-minute sustained winds of 77 kn (89 mph; 143 km/h) and gusts of 97 kn (112 mph; 180 km/h) being reported at the Isla María Madre airport. At 01:20 UTC on October 24 (7:20 pm on October 23, local time), Willa made landfall as a Category 3 hurricane near Palmito del Verde [sv], Sinaloa, with 1-minute sustained winds of 115 mph (185 km/h) and a minimum central pressure of 968 mbar (28.6 inHg). At the same time, it was noted that Willa's eye was fading on satellite imagery. 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 NHC noting that the mid- and upper-level circulations had decoupled from the lower-level circulation. The remnants of Willa continued to travel northeastward, bringing rain to multiple states in the United States.
Hurricane Willa nearing landfall in Sinaloa on October 23.
On October 21, at 15:00 UTC, the Government of Mexico issued a Hurricane Watch for the western coast of Mexico from San Blas to Mazatlán, and a Tropical Storm Watch from Playa Perula to San Blas. At 21:00 UTC, the Tropical Storm Watch for Playa Perula to San Blas was changed to a Tropical Storm Warning. At the same time, a Tropical Storm Watch was issued for Mazatlán to Bahia Tempehuaya. At 03:00 UTC on October 22, the Hurricane Watch for San Blas to Mazatlan was replaced with a Hurricane Warning. The warnings were discontinued on October 24, after Willa weakened to a tropical storm over Durango.
Sinaloa Governor Quirino Ordaz Coppel declared a state of emergency for seven municipalities. About 40,000 people in Jalisco, Nayarit, and Sinaloa evacuated their homes due to the storm, utilizing 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. Emergency authorities evicted over 4,250 people in costal cities from their homes and established 58 shelters before the storm hit.
Hurricane Willa's landfall in Sinaloa left two municipalities isolated – Escuinapa and Rosario. High winds damaged homes and knocked down trees, which blocked roads. The storm left 96,200 people without power in four states: Sinaloa, where it moved ashore, as well as Nayarit, Durango, and Michoacán. In Escuinapa, the storm damaged the hospital and the municipal water system, and the preliminary damage were confirmed at MX$350 million (US$17.9 million). In Morelia, the damage were at MX$35 million (US$1.79 million), while loss in Lerdo, Durango were about MX$140 million (US$7.14 million).
Known Pacific hurricanes with at least $500 million in damage
In the state of Nayarit, Willa killed four people – three drowned along the San Pedro River, and the other was discovered by fishermen. Across the state, the hurricane displaced more than 10,000 people. A hydro-agricultural system in northern Mexico was damaged, resulting in MX$700 million (US$35.7 million) in losses. Total damage in the state was estimated at MX$10 billion (US$510 million). Heavy rainfall killed two more people in Nogales, Sonora, where floods also swept away cars and entered homes and businesses.
On October 24, the remnants of Hurricane Willa brought heavy rainfall and thunderstorms to Texas, which had already been saturated from excessive rainfall within the past month. A Flash Flood Warning was issued for Galveston County, in southeastern Texas.
After Willa moved ashore in southwestern Mexico, Mexican officials in Nayarit sent 76 vehicles with medical supplies to reach the most affected residents in the northern part of the state. For one week, officials made Mexican Federal Highway 15D – a toll road – free of charge, and instead collected more than MX$1.1 million (US$57,000) in donations for the residents left homeless by the hurricane.
In the Escuinapa Municipality in Sinaloa, it was reported that over 2,000 families were living under plastic rooves six months after the storm. Additionally, Mayor Emmet Soto Grave stated that there were many irregularities in the damage reported by the previous government. In total, 144 houses had been counted from October 23–28, while more than 2,000 were actually affected. After President Andrés Manuel López Obrador had federal officials visit the city, more inaccuracies regarding damage to roads, educational institutions, and areas of tourism were discovered. Around the same time, the National Water Commission reported that the Baluarte River had seen a major increase in chromium, mercury, and nickel concentrations a month after the storm.
^Operationally, Willa was reported as having intensified by 105 knots to a high-end Category 4 hurricane in 48 hours, but the timing of the system's peak intensity was adjusted in the post-storm reanalysis.
^ abLixion Avilia (October 24, 2018). Hurricane Willa Discussion Number 16. National Hurricane Center (Report). Miami, Florida: National Oceanic and Atmospheric Administration. Retrieved April 13, 2019.