Monday, October 26, 2015

The Short but Spectacular Life of Hurricane Patricia

Hurricane Patricia as seen from the International Space Station
on October 23.
Photo by Astronaut Scott Kelly
Most of the weather buzz on Friday, both on social media and in the news, concerned Hurricane Patricia. This storm was born a tropical depression with winds of 35 mph on Tuesday morning, October 20, and by late Thursday evening it was a Category 5 hurricane with sustained winds of 160 miles per hour. It continued to grow from there to become the strongest hurricane ever recorded in the eastern Pacific, peaking at sustained winds of 200 mph and a central pressure of 879 millibars. It made landfall along the Mexican coast between Manzanillo and Puerto Vallarta.


Patricia's four-day lifetime was not that unusual in itself. However the rate of intensification, a pressure drop of 100 millibars in 24 hours, may be a new record, and the strength of the storm was a record for the eastern north Pacific and is the third strongest tropical cyclone on record. Supertyphoon Nancy in 1961 produced winds of 215 mph to top the list. Patricia is the strongest hurricane ever recorded in the Western Hemisphere. The lowest pressure recorded in Patricia, 879.4 millibars broke a record that was set in 2005 when Hurricane Wilma bottomed out at 882 millibars.

Chart showing the history of Hurricane Patricia taken from 6-hourly updates from the National Hurricane Center.


All of these records are still provisional until data is analyzed and final.

Patricia's incredible intensification and record strength were fueled by extremely warm waters over the eastern Pacific. Sea surface temperatures were in the mid 80s, and the layer of warm water was deep. This limited the amount of cooling due to upwelling, or the transport of colder deep water to the surface. Upper level wind shear (increasing speed with height) was also minimal, and together with abundant moisture these conditions contributed to unimpeded intensification.

Sea surface temperatures over the Pacific showing temperatures 30°C (86°F) off the Mexican and Central America coasts


Patricia made landfall at about 6:15 p.m. on Friday, October 23, about 55 miles west-northwest of Manzanillo, Mexico near the town of  Cuixmala. Sustained winds at landfall were estimated at 165 mph, although a weather station located at Chamela-Cuixmala recorded sustained winds of 186 mph at 5:50 p.m. CDT, and winds greater than 160 mph for more than an hour.

Some have called the designation of Patricia's impact as potentially "catastrophic" as over-hype. However, the observations alone mentioned in the preceding paragraph counter this characterization as well as the destruction experienced by the towns and villages in the area Patricia made landfall. Patricia did make landfall in a sparsely populated  region. Had this hurricane made landfall further north or south, directly affecting the much high population densities in Manzanillo or Puerto Vallarta, the impacts could have been more devastating.

Graphic credit: Mike Lowry via Twitter/Weather Channel

As of this writing six deaths have been attributed to the storm in Mexico. Destruction to trees and structures near landfall is extensive, both from the wind and from the storm surge. So far I have not seen any figures on the height of the storm surge, but witnesses reported seeing a wall of water. The Mexican Water Commission warned of waves as high as 39 feet. Storm chaser Josh Morgerman provided this account of Patrica's landfall near "ground zero". You can follow Morgerman on Facebook at iCyclone.


Hurricane PATRICIA. All I can say is: terrifying storm.
    After an hour or two of violent, destructive winds in Emiliano Zapata (our location: 19.38973N 104.96391W), the pressure bottomed out at 937.8 mb at 6:12 pm. We saw brightness in the sky and some touches of blue, and while the wind was still dangerous, it seemed to be a little less energetic for a few minutes. (I notice that the NHC's landfall point was *very* close to us! So it looks like we might have been skirting the edge of the eye at this time.) Then the pressure started to rapidly rise, and I assumed the worst of the hurricane had passed. Actually, it hadn't started. (Ugh.)
    At 6:34 pm the wind shifted sharply to the W, and a wall of wind and rain swept in, engulfing the hotel with a howling, whistling sound. There was a complete whiteout. The building trembled. Things were crashing-- big crashes as the hotel started to blow apart. Erik and I retreated to our room. A frightened hotel worker joined us and we stood in the dark, not sure what to do. We heard a terrific explosion and assumed the roof had blown off. (We were right.) Minutes later a man burst into the room-- a family across the hall was in trouble-- their room had torn open-- roof, ceiling, and all had blown away. Erik rushed across the hall-- which was now a wind tunnel-- and helped them into our room. Then all of us-- six adults and two children-- crammed into the tiny bathroom: the family around the toilet, Erik and me in the shower stall, two hotel workers next to the sink, all of us pressed against each other in the darkness like trapped animals. Roaring. Crashing. The mother wept-- she was freaked out. I told her not to worry-- told her (in broken Spanish) we were totally safe-- but I was talking nonsense, telling a lie. More crashing. We put pillows and blankets over the children, and Erik and I put computer bags over our heads and got low. Water was streaming from the ceiling and we expected it to blow away any second. So Erik and the two workers and I pulled the mattress off the bed and squeezed it into the bathroom. We tore the shower doors out to make room, then lifted the mattress up over everyone and wedged it in to make an extra ceiling. And we waited.
    The howling continued, but the pressure was rising fast-- into the 960s, then '70s-- and I knew we'd clear the core soon... just a few more minutes of this insanity. And by maybe 7 pm or so, we did. We crept out to look at the devastation-- smashed rooms, mountains of debris, trees stripped bare. And as it got dark the wind slowly calmed... And we had a tranquil night sleeping on a damp mattress, the crickets chirping all hours in the black, sticky calm.
    On a meteorological note: The pressure gradient in the core of this cyclone was frightening. The pressure recovered explosively-- 31 mb in 26 minutes (6:24 - 6:50 pm) (!!) and an incredible 15 mb in just 9 minutes (6:34 - 6:43 pm) while the winds ripped apart the hotel. It was an incredible, frightening experience (and honor) to punch the core of this Cat-5 hurricane-- the strongest known landfall ever in the Eastern Pacific. My video footage is messy, shaky, and wild, but I believe it captures the terror of the experience and I hope to post it soon.

Rainfall was heaviest along the coast. 24-hour rainfall totals ranged between 5 and 12 inches, and there were likely higher amounts in the mountains as Patricia moved inland and weakened.

Precipitation accumulation for the 24-hour period ending the morning of October 24.

Hurricane Patricia went from a tropical storm to a Category 5 hurricane in just 24 hours, and then to a remnant post-tropical low in just 12 hours. The mountainous terrain and uncoupling of the storm from the warm Pacific waters contributed to the storm's rapid decline, as is typical with tropical systems.

video


In the final analysis Hurricane Patricia will go down not only as the strongest hurricane recorded in the eastern Pacific, but also as one that caused much less damage and loss of life than it could have. The low population density near landfall, as well as the preparedness of Mexican authorities mitigated Patricia's impact. The population heeded warnings that were issued, and more than 15,000 people were evacuated to shelters prior to the storm's arrival. The forecasts issued by the National Hurricane Center of the hurricane's track were consistent. The models did forecast the storm to intensify but fell short of the actual intensification. Nevertheless the NHC did issue advisories indicating the storm strengthening before landfall, and the warnings communicated the extremely dangerous nature of this storm.

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