Hurricane Willa's dangerous intensification, explained

After a massive intensification over the weekend, Hurricane Willa is whirling towards Mexico's West Coast as a Category 4 storm. Everything about the storm will be life-threatening, the National Hurricane Center warns: hurricane-force winds, flash flooding, landslides, and storm surge are predicted along the storm's path. "Preparations to protect life and property should be completed," the National Hurricane Center says.

Just days ago, Hurricane Willa was a tropical storm, CNN carryforwards. By Monday morning, Willa had become a Category 5 hurricane with winds reaching speeds of 165 miles per hour. By Monday afternoon, the winds have been slackened to a small to 150 miles per hour, and the National Hurricane Center is down to the east coast. Mexico later in the day.

While the storm is expected to continue losing strength, the National Hurricane Center predicts it will probably drop to a significant amount of steam before it hits Mexico. "Unfortunately landfall is tomorrow, so it does not have a weakening of your time," says Phil Klotzbach, an atmospheric scientist at Colorado State University. The storm is still at a major hurricane when it strikes land. "It definitely looks like a pretty serious threat," he says.

After back-to-back hurricanes pummeling the east coast of the US, a hurricane on the Pacific coast of North America may seem surprising. But in fact, the northeastern Pacific is actually more prone to hurricanes than the Atlantic, Klotzbach says. So far, this is a category that is likely to be a combination of favorable atmospheric conditions and warm ocean waters. And taking storm frequency, duration, and intensity into account, this is the most active hurricane season on record, he says

The Verge with Klotzbach about hurricanes in the Pacific, Willa 's speedy intensification, and why this year is so odd.

This interview has been edited for clarity and brevity.

Is Hurricane Willa unusual?

It's unusual in that it intensified that quickly. The models were always really aggressive at developing this storm. Tea [National] Hurricane Center has been watching this thing for a while, and it was not really doing much – and then basically coming back from a tropical depression to a category 5 in like 48 hours, which is very impressive. Not the fastest, but definitely up there in terms of intensifying quickly.

In terms of its track, that's pretty typical for late summer in the east Pacific. They tend to move west and then go back to Mexico. So for the western coast of Mexico, getting into uncommon stuff. I think it's probably going to weaken. But even if it's a bit better than it's a stronger storms that have hit them.

Is there a pattern to hurricane training in the Pacific, and does Hurricane Willa fit that pattern?

In the Pacific, we are not hurricanes hitting California – and also the shear gets quite strong. So storms in the northeast Pacific form a nice tight little latitude-longitude area. And then most of them go west and track north, get to cold water, and die. Most hurricanes in the northeast Pacific do not really impact people. Which is why frankly, in research, it is probably the most neglected hurricane basin.

But then you do get these storms obviously, like we had Patricia [in 2015], which is probably the one that people remember the most. Hurricane Kenna in 2002 was a very strong hurricane that went into the western part of Mexico, and killed four people when it made landfall. Certainly you do not want these things to go wrong in Mexico, and it's a very good analog in terms of its track because it made landfall [Category] 4th of October 25th – so about the same time. These kinds of powerful hurricanes have been successful in the past few years in Mexico.

We do not hear about hurricanes in the Pacific as often as we hear about hurricanes in the Atlantic, is that because there are fewer?

There are actually more! This is the most active northeast Pacific hurricane season on record, and no one pays attention to the storms because they usually go to the middle of nowhere and die. So unless they go and hit Hawaii, like Lane did, people just kind of ignore them and go, "Oh, it's a pretty pretty hurricane out of the middle of nowhere doing impacts to anyone." But it's been a phenomenally active northeast Pacific season. Climatologically the Atlantic has 12 storms, and the northeast Pacific has 16, so they do get more. Not every year, but in general it's more active than the Atlantic.

Why is that?

A lot of it is just that the shear is lower. Shear is the change in wind direction with height in the atmosphere. So the idea is that hurricanes want to be upright. If you have shear – if you have winds in one direction blowing, say, out of the east, and winds in the other direction blowing out of the west – that will basically tilt the circulation hurricane. It disrupts the vortex, and you can not get the deep thunderstorms you need to support the storm. So shear is detrimental for hurricanes, and when you get a lot of shear it tends to really knock down the season.

So you have an area of ​​low shores right on the coast of Mexico, and the waters there are still plenty warm to support nasty hurricanes. One of the ideas is that a lot of the storms that form in the northeast. If they do not develop in the Atlantic, sometimes they'll [go all the way across the caribbean and] develop in the eastern Pacific. So in a lot of ways, the Atlantic and the North Pacific tend to be inversely related: when the Atlantic is very active, the northeast Pacific tends to be quiet, and vice versa.

Is this what's happening this year?

This year is kind of an oddball year. This year's a little above normal in the Atlantic. But when the northeast is active, you would not expect the Atlantic to have much activity, so it's a little unusual in that regard. That's one of the many things we're trying to figure out for this year.

Why did Willa intensify so quickly?

The waters are warm. I looked for Willa, they're running about a degree warmer than normal. The interesting thing is that there is some basic research that can be done at a certain level, the hurricane can only get so strong.

So Willa is right in the heart of the water. Which hurricanes are nowhere near they can get better for the water temperatures because of shear, and other factors that come into play and knock down the storm down. The thing with Willa is that theoretically it really is, given the water temperatures that it's under. And it looks like the shear is going to go up. So even though the water temperatures are going to get a little bit warm, the shear is going to go up, and that should hit the storm.

What's the role of climate change in the Pacific hurricane season, and with Willa?

In general, you have warmer waters, [which] provides more fuel for the storms. I would say that certainly, yes, it's not going to help matters. But it's not so simple and straightforward as you feel about the surface of the ocean, you're going to get stronger hurricanes. There's other factors that come into play, too. When you warm the atmosphere in climate change, you warm up the atmosphere, not just the ocean surface, and that takes a little bit of the edge of just warming the ocean's surface.

This year we've had really low shear, which is probably driven by El Niño-like conditions. And El Niño is mostly a natural event that has been well established on the planet, and probably before then. People want like, "Humans are eight percent responsible." But it's really hard to say for sure in that look.

I'm concerned with sea level if the storm does not change at all with its intensity, if, say, the sea level is 6 inches higher than it used to be, you're going to get more inundation – especially where the coast slopes up very gradually. And also I think there is a lot of evidence that these storms will bring rain. Obviously Florence and Harvey are extreme examples of that, but that's something we expect to see.

What else do you want to know about Willa?

It's a serious storm, it's going to make landfall tomorrow. You have a Florence, and an Irma, and people think, "Oh, you have two weeks notice that a hurricane's coming." And that's not always the way it is. Sometimes these storms come very quickly – and certainly we saw that with Michael and with Willa, too. The storms that come back in the middle of the day, but this is going well. So we're just going to have hope and pray that it's weakens before it hits. We've got a little over a day. If people happen to be there, follow the advice of local emergency management, they know the storm and will be the best people on the ground to provide advice on what to do.