Category 3 Hurricane Willa Approaches Landfall in Mexico

Update: Hurricane Willa made landfall near 9 pm EDT October 22, 2018, about 50 miles southeast of Mazatlán, Mexico. At landfall, Willa was a Category 3 storm with 120 mph winds, making it the 11th strongest Pacific hurricane on record to hit Mexico. Willa was Mexico's 13th major Pacific landfalling hurricane since records began in 1949.

Hurricane Willa was pounding the Mexican islands of Las Islas Maria late Tuesday morning as the storm headed north-northeast at 6 mph toward an expected Tuesday evening landfall about 50 miles southeast of Mazatlán (population 660,000). An Air Force hurricane hunter aircraft found Willa’s top winds had decreased to 125 mph and the central pressure had risen to 966 mb, thanks to an eyewall replacement cycle that had caused the inner eyewall to collapse. We’ll never know exactly how strong Willa was on Monday afternoon when it reached Category 5 status, since the Air Force plane that flew into the hurricane was struck by lightning in one of the outer rain bands and had to return to base due to safety issues with some of the onboard equipment.

#HurricaneWilla
Three #Copernicus views of the same phenomenon:
The beast and its eye as seen by #Sentinel3
Salt aerosol forecast by @CopernicusECMWF Atmosphere Monitoring Service
Wave height forecast by @CMEMS_EU Marine Environment Monitoring Service pic.twitter.com/SHnNIyuBhq

— Copernicus EU (@CopernicusEU) October 23, 2018

Satellite images early Tuesday afternoon showed that Willa had degraded significantly in appearance from when it was a Category 5 storm on Monday afternoon. The eye was no longer as distinct, and the eyewall thunderstorms were not as intense or well-organized. Willa still had a favorable environment for intensification, though, according to the 12Z Tuesday analysis from the SHIPS model: moderately high wind shear of 15 - 20 knots, a moist atmosphere with a mid-level relative humidity of 65%, and warm waters of 29°C (84°F). Warm waters extended to great depth beneath the hurricane, giving Willa plenty of heat energy to work with (nearly 50 kilojoules per square centimeter). Willa was an average-sized hurricane, with hurricane-force winds that extended out up to 40 miles from the center, and tropical storm-force winds that extended out up to 125 miles.

Willa's dangerous eastern eyewall was passing directly over Mexico's northern Islas Marias on Wednesday morning. The largest of the islands, Isla Maria Madre, includes about 1000 residents as well as hundreds of prisoners at the Islas Marias Federal Prison, the last island-type penal colony remaining in the Americas.

Figure 1. Predicted surface winds (colors) and sea level pressure (black lines) for 8 pm EDT Tuesday, October 23, 2018, from the 6Z Tuesday run of the HWRF model. The model predicted that Willa would make landfall in Mexico as a weakening Category 2 hurricane with 105 mph winds and a 980 mb pressure. Image credit: Levi Cowan, tropicaltidbits.com.

Willa likely to weaken before landfall

Wind shear is expected to increase to 20 – 25 knots Tuesday afternoon as Willa approaches landfall, and the storm will also begin to interact with the high terrain of Mexico. These factors should lead to steady weakening just before landfall. Still, landfall as a major Category 3 hurricane is quite possible, though NHC and most of our reliable intensity models predict that Willa will be a Category 2 or weaker storm at landfall.

Likely impacts

All three of the hurricane’s hazards—wind, storm surge, and heavy rain—are a significant threat along a region about 70 miles wide near the landfall location. Fortunately, Willa is expected to make landfall along a stretch of Mexico’s coast where there is not much development. Given the lack of coastal infrastructure in the expected landfall zone, wind damage is likely to be much more costly than storm surge damage. The largest city in the region, Mazatlán, is expected to be on the weaker (left) side of Willa’s circulation, limiting the amount of wind damage to be expected there. Flashing flooding and mudslides from Willa’s expected heavy rains of 6 – 12” are the chief threat for loss of life from the storm.

Weather.com will be featuring live coverage on Willa in a special segment available on the Weather Channel app and Facebook page starting at 5 pm EDT Tuesday.

Landfalling major hurricanes are uncommon along Mexico’s Pacific coast

(Updated for WIlla): Landfalling major Pacific hurricanes are uncommon in Mexico, having occurred an average of once every five years since 1957, according to NOAA’s HURDAT2 database and historical hurricane tracks web site. Of the thirteen Pacific major hurricanes that have made landfall in Mexico since record keeping began in 1949, five were Cat 4s, and eight were Cat 3s:

Category 4 Mexico landfalls (Pacific)
----------------------------------------
Patricia, October 23, 2015: 150 mph
Madeline, October 7, 1976: 145 mph
Unnamed, October 27, 1959: 140 mph
Unnamed, October 22, 1957: 140 mph
Kenna, October 25, 2002: 140 mph
Liza, October 1, 1976: 130 mph

Category 3 Mexico landfalls (Pacific)
----------------------------------------
Odile, September 15, 2010: 125 mph
Lane, September 16, 2006: 125 mph
Tico, October 19, 1983: 125 mph
Olivia, October 14, 1967: 125 mph
Willa, October 24, 2018: 120 mph
Kiko, August 27, 1989: 115 mph
Olivia, October 25, 1975: 115 mph

As we discussed in yesterday’s post, Willa was Earth’s ninth Category 5 storm of the year, and maintained Category 5 strength for six hours. Willa puts 2018 into a tie for second place for most Category 5 storms in one year. Willa is also one of only four October Category 5 storms ever observed in the Eastern Pacific (east of 180˚W). The others were Hurricane Patricia (October 23, 2015), Hurricane Kenna (October 24 – 25, 2002), and Hurricane Rick (October 18, 2009). Willa brought this year’s accumulated cyclone energy (ACE) in the Eastern Pacific to a new all-time record.

Just eight Eastern Pacific hurricanes have had their names retired because of their landfall impacts in Mexico. The most expensive Pacific hurricane for Mexico was Hurricane Manuel of 2013, which did $4.4 billion in damage (2013 dollars). The deadliest was an unnamed 1959 Category 4 hurricane that hit the coast near Manzanillo, killing over 1800.

Explosive rapid intensification from low-end tropical storm to Category 5 hurricane in 48 hours -- zooming in on the core of #Willa pic.twitter.com/4XJ9aASOuS

— Stu Ostro (@StuOstro) October 22, 2018

Figure 3. Predicted precipitation for the 7-day period ending at 12Z (8 am EDT) Tuesday, October 30, 2018. The remnants of Willa are predicted to dump 1 - 2” of rain in portions of Texas and northern Mexico. Energy and moisture from Willa are expected to feed a non-tropical coastal storm that will bring 1 – 3” of precipitation along much of the U.S. Gulf Coast and East Coast. Image credit: National Weather Service.

Willa’s remnants will contribute to rains from Texas to the East Coast

Willa will weaken rapidly and dissipate by late Wednesday as it traverses hundreds of miles of dry, rugged train across northwest Mexico. Although Willa will no longer be a tropical cyclone by Thursday, some of the moisture and energy from its remnants may enhance rainfall across Texas associated with a developing coastal low. This non-tropical surface low will hug the northern Gulf Coast through Friday, then strengthen off the Southeast and mid-Atlantic coast over the weekend. Off the Northeast coast, it’s expected to morph into the season's first nor’easter, bringing cold, blustery rain to the coast and some wet snow inland.

Rains of 1” – 2” are expected across the bulk of central and southern Texas from Wednesday into Thursday. These are unlikely to produce major flooding on their own, although they could keep some rivers running high in the wake of last week’s historic flooding in the Hill County northwest of Austin. Huge amounts of mud, silt, and debris are hobbling Austin’s water treatment plants; the city has warned residents to boil water and to cut their usage by 15-20 percent, reported weather.com.

Figure 4. Total autumn precipitation (Sept. 1 - Nov. 30) in the Dallas–Fort Worth area from 1898 to 2018. The 2018 total is for Sept. 1 - Oct. 22, but it already exceeds the three-month total for all previous autumns. Image credit: NOAA Regional Climate Centers.

Wettest autumn on record (already) in Dallas-Fort Worth

This week’s rain will continue to goose some already exceptional autumn totals for two of Texas’s biggest metro areas. From Sept. 1 through Tuesday, Dallas–Fort Worth (DFW) picked up 24.99”. This already tops the 21.82” record from 2015 for any autumn season (Sept.-Nov.), with more than five weeks to go (see Figure 4 above). Records for the DFW area go back to 1898. San Antonio has recorded 21.28” so far this autumn, and this week’s rains could put them close to the autumn record of 23.04” from 1998. Records for San Antonio go back to 1885.

Interestingly, despite the heavy rains upstream and the flood-related problems in the city itself, Austin is a long way from record territory for autumn rainfall. The city's 14.86” through Tuesday is well short of the 23.19” record.

Tropical Storm Vicente kills 11 in Mexico

Tropical Storm Vicente brought torrential rains that triggered flash floods and mudslides in Oaxaca, Mexico over the past two days, which have killed at least 11 people, according to Mexico News Today. Vicente made landfall over the Mexican state of Michoacan as a tropical depression on Tuesday morning, and has now degenerated into a remnant low. Vicente’s remnants are expected to bring heavy rains of 3 to 6”, with local amounts to 10”, to portions of Guerrero, Michoaca, Colima, and Jalisco in Mexico through Wednesday.

A central Atlantic disturbance to watch late this week

A broad area of low pressure is expected to form late this week in the central Atlantic a few hundred miles east-northeast of the northern Leeward Islands. Some tropical or subtropical development of this system is possible by the weekend while it meanders over the central Atlantic. The 0Z Tuesday run of the GFS ensemble model had more than 50% of its 20 members predict development by early next week, as did more than 40% of the 50 members of the European model ensemble forecast. Bermuda is probably the only land area potentially at risk from this system. In their 8 am EDT Tuesday Tropical Weather Outlook, NHC gave this system 2-day and 5-day odds of development of 0% and 20%, respectively. The next name on the Atlantic list of names is Oscar.

Figure 5. Enhanced infrared satellite image of Typhoon Yutu at 1310Z (9:10 am EDT) Tuesday, October 23, 2018. Image credit: RAMMB/CIRA/CSU.

Yutu takes aim on Northern Mariana Islands; could become Earth’s next Category 5 storm

Typhoon warnings are up for parts of the Northern Mariana Islands as Yutu rapidly strengthens in the Northwest Pacific. As of 8 am EDT Tuesday, Yutu was packing sustained winds of 105 mph, according to the Joint Typhoon Warning Center (JTWC). The environment ahead of Yutu is nearly ideal for strengthening. Wind shear is predicted to become light, around 10 knots or less, as Yutu moves over SSTs of 29-30°C (84-86°F) within a very moist atmospheric envelope.

Yutu is on a fairly straightforward west-northwest track, but the path projected by JTWC now bends just far enough south to put the islands of Saipan and Tinian at risk of a direct hit on Wednesday local time. By that point, Yutu is likely to be a Category 4 storm. Although Guam and Rota are expected to be on the storm’s weaker left-hand (south) side, they could still experience high wind and heavy squalls. Saipan, Tinian, and Rota are in a typhoon warning, with Guam in a tropical storm warning.

Beyond the Marianas, Yutu is predicted by JTWC to reach Category 5 super typhoon strength by Saturday local time, a prognosis supported by the high-resolution HWRF model. Steering currents are expected to weaken early next week, which adds a great deal of uncertainty to the outlook for Yutu as it spins off the East Asia coast.

Bob Henson co-wrote this post.

Figure 6. Predicted surface winds (colors) and sea level pressure (black lines) for 2 pm EDT Wednesday, October 24, 2018, from the 6Z Tuesday run of the HWRF model. The model predicted that Yutu would pass about 60 miles to the north of Saipan and Tinian islands in the Northern Mariana Islands as a strengthening Category 3 typhoon with 125 mph winds and a 934 mb pressure. Image credit: Levi Cowan, tropicaltidbits.com.