Hurricane Patricia, a record-breaking storm in the eastern Pacific, is on track to hit southwestern Mexico on Friday evening. The National Hurricane Center is warning about a "potentially catastrophic landfall," and authorities have been scrambling to evacuate the area:
This storm's rapid evolution over the past two days has shocked observers. On Wednesday, Patricia looked like an ordinary tropical storm, with 40 mile-per-hour winds. Since then, Patricia has grown into a monster Category 5 hurricane. By Friday morning, the cyclone had maximum sustained winds near 200 miles per hour, among the strongest storms that humans have ever measured.
Hurricane Patricia has already broken records
One of the telltale signs of hurricane strength is the low pressure in the center of the storm: the lower the pressure, the stronger the hurricane. On Friday morning, the National Hurricane Center announced that it had sent its reconnaissance aircraft into the cyclone and measured pressures of 880 millibars — the lowest ever observed in this region.
That made Patricia "the strongest hurricane on record in the ... Atlantic and the eastern North Pacific basins." (Note: There have been a few tropical cyclones recorded in the western North Pacific with even lower minimum central pressures, but those storms are called "typhoons." Same type of storm, just different basin and name.)
The storm's 200 mile-per-hour maximum sustained winds were also a record for any cyclone ever measured, and the rapid rate of intensification between Thursday and Friday was the fastest ever observed since satellite tracking began in the 1960s.
A few factors helped Patricia get so unusually fearsome in such a short period of time: First, the storm encountered relatively little wind shear, which can otherwise tear apart hurricanes. Second, and more importantly, the eastern tropical Pacific Ocean is unusually warm right now, with temperatures 1°C to 2°C above their historical baseline. As Jeff Masters of Weather Underground points out, Patricia passed over an area of particularly warm, deep, undisturbed water, helping it gather strength:
The ongoing El Niño in the Pacific Ocean is helping to lift surface temperatures in this area, so that's one obvious culprit. (On the flip side, El Niño events also tend to reduce the risk of hurricanes forming in the Atlantic basin.) But Pacific Ocean temperatures have also been rising over time, due to global warming. Andrew Freedman has much more on the climate-change context for Patricia.
Mexico has been scrambling to evacuate
Some of Mexico's most popular resort areas, including Puerto Vallarta, are in the storm's likely path, and at the moment, people are racing to get out of the way.
It's not yet clear how strong Patricia will be when it makes landfall later this evening; by Friday afternoon, the winds had weakened slightly to 190 mph. But the National Hurricane Center is still forecasting 8 to 12 inches of rainfall, along with life-threatening flash floods and mudslides. Storm surges could cause large waves reaching 39 feet high, officials said. The 15-mile swath directly in the path of the hurricane could also face winds strong enough to destroy buildings.
The World Meteorological Organization has compared Patricia to Typhoon Haiyan, another powerful Category 5 cyclone that left more than 7,300 dead or missing in the Philippines back in 2013. Storms and situations can vary widely, so that's not a prediction for what will happen in Mexico. But it provides a sense of the potential danger here.
According to the Wall Street Journal, Mexico is taking this very seriously: "Officials declared a state of emergency for 56 municipalities in the hurricane’s projected path and handed out sandbags in preparation for flooding. ... Authorities in Guerrero, Colima and Jalisco ordered schools to be closed Friday." Roughly 7.3 million people live in Jalisco state, and another 650,000 live in Colima.
It's hard to overstate how much devastation a powerful hurricane is capable of. Back in 2014, an NBER working paper by Solomon Hsiang and Amir Jina found that massive tropical cyclones don't just kill lots of people — they can also ravage a region's economy for years after the fact. Historically, the economists found, the very strongest cyclones "reduce per capita incomes by 7.4% two decades later [on average], effectively undoing 3.7 years of average development."
Again, this is not a prediction for this particular cyclone. So much depends on where Hurricane Patricia hits, how populated the area is, how successful evacuation efforts are, how long the storm lasts. But this paper should give a sense of scale here: the very strongest hurricanes can be unfathomably destructive.
-- Seth Borenstein has written a more detailed piece for the AP on why Patricia intensified so rapidly between Thursday and Friday.
-- Greg Laden once wrote a useful post breaking down what hurricane "landfall" means, exactly. As he rightly notes, hurricanes are huge, and start doing damage well before they officially hit land.
-- Here's handy map showing the parts of the world where tropical cyclones are called "hurricanes," the parts where they're called "typhoons," and the places where they're just known as "cyclones."