After growing extraordinarily quickly to Category 5 strength, and striking the Mexican coast less than a day later, Tropical Depression Patricia
is rapidly dissipating--leading to one of the most abbreviated life cycles on record for any Category 5 tropical cyclone. At 11 am EDT Wednesday, Patricia was a minimal tropical storm, with 40 mph winds. A mere 36 hours later, Patricia packed winds of 160 mph, eventually reaching 200 mph--the highest reliably measured surface winds in any tropical cyclone on Earth. After 36 more hours (at 11 am EDT Saturday) Patricia’s sustained winds were back down to 35 mph. As with all tropical cyclones, Patricia’s landfall was its downfall: the hurricane slammed into rugged coastal terrain while accelerating northeastward, which quickly shredded its low-level circulation. At 11 am EDT Saturday
, Patricia’s low-level center was located in central Mexico, about 100 miles northeast of Zacatecas. Unimpeded by the mountainous terrain, Patricia’s upper-level circulation is racing more quickly to the northeast, on its way to help generate a large area of torrential rain tonight across southern Texas.Figure 1.
MODIS image of Hurricane Patricia as seen from NASA's Aqua satellite just before landfall at 4:35 pm EDT Friday, October 23, 2015. At the time, Patricia was a Category 5 storm with 190 mph winds. Image credit: NASA.Figure 2.
Rainfall from Hurricane Patricia for the 24 hours ending at 8 am CDT October 24, 2015. The maximum rainfall was 11.43" (290.2 mm) in Nevado de Colima, marked by a triangle. Note: 1" = 25.4 mm. Image credit: Conagua.Why didn't Patricia cause more death and destruction?
After a landfall by a Category 5 storm that was the strongest landfalling hurricane ever recorded in the Eastern Pacific, many were expecting today to hear reports of huge swaths of mind-boggling devastation in Mexico. While it is too soon to be confident that major loss of life was avoided until we hear from the hardest-hit areas, there is reason to be optimistic that the death toll from Patricia will be low. The storm hit a relatively sparsely populated area, missing the cities of Puerto Vallarta (population 380,000) to its left and Manzanillo (population 100,000) to its right. The region of coast most affected by the storm surge did not have a large area of shallow water offshore conducive for piling up a huge storm surge. Patricia's Category 5 winds were confined to a relatively narrow swath about fifteen miles in diameter, and this swath missed major cities. While Patricia did dump torrential rains along its path, the storm was moving fast enough at landfall--about 20 mph--that these heavy rains did not stay in place long enough to generate the kinds of devastating floods we've seen in the past from Mexican hurricanes.Figure 3.
Soldiers evacuate residents to a shelter in Zoatlan, Nayarit state, about 150 km northwest of Guadalajara, Mexico, on Saturday, October 24, 2015, as Hurricane Patricia brought heavy rains to the region. Image credit: Eduardo Verdugo/AP.
Credit also needs to be given to Mexican civil defense efforts, which have historically been among the best in the world at getting people out of harm's way from approaching hurricanes. In 2005, Hurricane Emily
made landfall on the Mexican coast near Cozumel Island as a Category 4 storm with 135 mph winds and a storm surge of up to 15 feet. Emily went on to cross the Gulf of Mexico and slam ashore on the Mexican coast south of Brownsville, Texas, as a Category 3 hurricane. Only three people died in Mexico from Emily's double strike on the country as a major hurricane--two of the deaths from a helicopter that crashed while evacuating offshore oil rigs. In addition, Mexico suffered only eight deaths from Hurricane Wilma's
$7.5 billion four-day pounding in 2005. Wilma started out as a Category 4 hurricane with 150 mph winds when it hit Cozumel Island, and gradually weakened to a Category 2 hurricane as it plowed north over Cancun and eventually into the Gulf of Mexico. Mexico's feat of surviving two strikes from a Category 4 hurricane, plus a Category 3 strike to populated areas, with only eleven deaths, is a civil defense success unparalleled in hurricane history.Life-threatening floods possible through Sunday in central Texas
While not as dramatic as an approaching Category 5 hurricane, a mammoth heavy-rain episode this weekend in Texas has real potential for harm and damage. The locations at greater risk include from the Hill Country west of Austin and San Antonio, extending through these major metro areas to the Houston area. Rainfall amounts in some areas have already exceeded the top amounts produced by Hurricane Patricia’s landfall in Mexico, and more is on the way.Figure 4.
Rainfall amounts (in inches) observed in the 24 hours from 12Z Friday, October 23, through Saturday, October 24. Image credit: NOAA Advanced Hydrologic Prediction Service
. Figure 5.
Rainfall amounts predicted for the 3-day period from 12Z (8:00 am EDT) Saturday, October 24, through Tuesday, October 27. Some local amounts will be significantly higher than the larger-scale totals shown here. Image credit: NOAA/NWS Weather Prediction Center
Several ingredients are converging across the heart of Texas to produce an event that will be unusually intense and prolonged even for this flood-familiar region. Heavy rains have been lumbering across the northwestern two-thirds of the state since Thursday, the result of a large upper-level trough over the Rockies coupled with strong, moist southerly flow. Showers and thunderstorms intensified across central TX on Friday night along an east-west surface boundary just south of the Dallas-Fort Worth area. From Thursday morning through noon CDT Saturday, a total of 19.07” of rain fell at Corsicana, where Interstate 45 was closed in both directions at midday Saturday. Coastal low could produce noteworthy flooding on Texas coast
With the main upper trough lifting out, a stronger cold front will plow southeast tonight, colliding with the upper-level remnants of Patricia over central and southeast Texas. A low-level jet will likely develop, importing even more moisture into the area. The upper-level energy from Patricia will help focus a new surface low near the middle Texas coast tonight that will translate slowly northeast near Houston on Sunday and into Louisiana on Monday. Models suggest that winds along the Texas coast could approach tropical storm strength near this surface low, and it may exhibit some subtropical characteristics, but the low will be driven mainly by nontropical processes and it is unlikely to be classified or named by the National Hurricane Center. The prolonged, strengthening southeast flow ahead of the low will lead to some coastal and tidal flooding, especially in the Houston-Galveston area.Figure 6.
WunderMap depiction of surface winds (in knots; multiply by 1.15 for mph) predicted by the 06Z Saturday run of the GFS model for 18Z (1:00 pm CDT) Sunday, October 25, 2015.
Storm surge expert Hal Needham, who is in the area this weekend for a conference, notes that water levels at Galveston have been running more than a foot above normal for several days, and a three-foot surge is possible on Sunday as the coastal low strengthens. In a blog post on Saturday morning
, he warned: “Although a 3-foot (0.91 m) storm surge is not phenomenal for Galveston, a prolonged 2-3 foot (0.6-0.91 m) surge could have dire impacts if accompanied by 10 or more inches of rain. Most drainage around the Houston- Galveston area is gravity-fed, meaning the drainage depends on a noticeable slope between the ground and the water body into which the rainwater is discharged, like a bayou, channel, Galveston Bay or the Gulf of Mexico. If Galveston Bay is elevated 2-3 ft (0.6-0.91 m) above normal, the slope between land and water is reduced considerably, making rainfall drainage less efficient. This becomes a major concern when looking at the extraordinary rainfall in the forecast.” Needham (@Hal_Needham
on Twitter) will be in the Houston-Galveston area through the weekend and invites readers to send him questions, comments, photos, or videos related to this event.Record atmospheric moisture at hand
Atmospheric moisture is already at record levels for late October across far south Texas (see Figure 7), and rainfall rates as high as 4.5”/hour have already observed. With the factors above converging after dark on Saturday, extremely intense rains can be expected over a large part of southern Texas from Saturday night into Sunday. People in flood-prone areas such as the Hill Country will need to be especially vigilant. Urban flooding is a particular concern tonight in Austin and San Antonio and on Sunday in Houston, where it could be compounded by the surge issues mentioned above. Isolated tornadoes are also possible on Saturday afternoon and evening, especially near the Texas coast, as highlighted by the Storm Prediction Center in its latest convective outlook
Jeff Masters and Bob HensonFigure 7.
Precipitable water (water vapor) in the atmosphere above Brownsville, TX, in soundings from all radiosondes launched from Brownsville, TX, from Jan. 1, 1948, through Oct. 26, 2014. The spiky red line shows the record-high values observed on each date. Depicted with the starburst at upper right is the record value of 2.62” measured at 12Z on Saturday morning, October 24, 2015. This is the highest value ever observed in Brownsville on any date between September 16 and June 19. At Corpus Christi, TX (not shown), Saturday morning’s value of 2.52” is a record for any date between October 20 and June 20. Image credit: NOAA Storm Prediction Center