October 25, 2023 Outlook: After a shocking burst of intensification, Hurricane Otis makes a catastrophic landfall near Acapulco

One-sentence summary

We are going to talk about Otis today because of the hurricane’s dramatic intensification on Tuesday, and overnight landfall along the Southern Pacific coast of Mexico.

Rapid intensification

Otis made landfall on Tuesday night, near Acapulco, with maximum sustained winds of 165 mph. This was a worst-case scenario for this region. Why? Because no storms had been recorded in this area, this strong, before. On top of that, local residents and business owners had less than a day to prepare for the worst hurricane of their lives. So not only was this storm unexpected, there was no institutional memory about what to expect from a major hurricane.

Hurricane Otis nears the southern coast of Mexico on Tuesday. (NOAA)

With this startling burst in intensity, Otis has nearly set a record for rapid intensification within 24 hours. The system strengthened from a 50 mph tropical storm at 1 am CT on Tuesday to 165 mph just 23 hours later. That is 115 mph in 24 hours. It is second only to Hurricane Patricia, a Pacific storm in 2015 that saw its maximum sustained winds increase by 120 mph during a similar period.

This morning, as it moves inland, Otis is weakening. As of 7 am CT the storm had 110 mph winds, and will continue to lose intensity as it interacts with mountainous terrain. Nevertheless, Otis will continue to bring damaging winds into Southern Mexico today, along with dangerous storm surge. Heavy rains will remain a problem later this week, through Thursday, for much of Southern Mexico. They are likely to produce significant flooding and mudslides.

Forecast track for Hurricane Otis. (National Hurricane Center)

Completely blind-sided

Let’s wind things back to Monday night, and have a look at the model forecasts for the intensity of Hurricane Otis. At the time this was a tropical storm, and largely expected to remain so before its landfall into Mexico. None of our ‘best’ models for predicting tropical system intensity anticipated Otis growing beyond tropical storm-strength. In two decades of forecasting I do not recall a whiff like this one.

A plot of intensity forecasts for Hurricane Otis. (Tomer Burg, Blue Sky).

As a meteorologist, these kind of moments are humbling. Otis will be studied in the coming months and years to understand why it blew up so quickly, and so powerfully, in such a short period of time. In moments like these, forecasters utterly failed the people of Southern Mexico. We must do better.

Hurricane Tammy

Over in the Atlantic Ocean, Hurricane Tammy continues to dance around the Atlantic Ocean. This storm would be a curiosity given its meandering track, but for its potential to come near Bermuda this weekend. As of Wednesday morning, Tammy has sustained winds of 100 mph, and there is a chance for some slight strengthening today.

However, after today it is likely to interact with a cold front, and begin a transition to a non-tropical storm. There is a fair amount of uncertainty in track and intensity. But for now it looks like Tammy will remain far enough south, and just weak enough, to not bring anything more than garden-variety like storminess to Bermuda this weekend.

Tammy is going to have a walk-about in the Atlantic this week. (National Hurricane Center)

Beyond Tammy, happily, the Atlantic tropics look quiet.

October 18, 2023 Outlook: Another tropical system is likely to form and threaten the Lesser Antilles

One-sentence summary

We’re nearing the end of the Atlantic hurricane season, but we need to continue tracking Invest 94L as it is likely to track across or near the northern end of the Lesser Antilles this weekend, including the islands Antigua and Barbuda.

Happening now: Invest 94L

There is precisely one system we need concern ourselves with in the Atlantic, and that is an area of low pressure that is approaching the Caribbean Sea. It continues to lack a center of rotation, but the system is starting to get its act together. The National Hurricane Center projects that it has an 80 percent chance of becoming a tropical depression or storm over the next week. Even if it does not the tropical system will bring heavy rains to parts of the Lesser Antilles this weekend.

Hello Invest 94L. (National Hurricane Center)

By the way, what do we mean when we say the Lesser Antilles? It can be a little confusing, both for readers and forecasters. So let’s spend a moment walking through it. We’ll start with the Greater Antilles, which are the larger Caribbean islandsCuba, Hispaniola, Jamaica and Puerto Rico—that mark the northern boundary of the Caribbean Sea. As this arc of islands extends further eastward and to the south, the islands get smaller, places like Antigua and Barbuda, Barbados, and Saint Kitts and Nevis.

These islands stretch almost all the way south to South America, and form the eastern boundary of the Caribbean Sea. These are the “Lesser” Antilles since they’re smaller islands. To make things even more confusing, the islands of the Lesser Antilles are divided into three groups: the Windward Islands in the south, the Leeward Islands in the north, and the Leeward Antilles in the west. So Invest 94L is threatening the Leeward Islands, which are part of the Lesser Antilles. Still with me? Good. There will be a quiz at the end.

A map of the Caribbean Islands. (University of Minnesota)

The good news for the Leeward Islands is that if 94L organizes into a stronger system it is likely to turn to the northwest before reaching land. If it remains weaker, then it could follow a more westerly track into the islands, bringing some winds, high seas, and rains, but nothing too crazy. We’ll fine tune the forecast in a day or two.

What else is out there?

Not much in the Atlantic Ocean.

After 94L does whatever it does, the only other watch area over the next 10 days or so will be in the southern or southeastern Caribbean Sea, where we may see a home-grown storm develop. But that is only a vague threat at this point. And as we approach the end of October, we can generally expect to see the Atlantic tropics winding down for the year.

Here’s the quiz: Anyone got any problems with that?

October 11, 2023 Outlook: Lidia is gone, Sean is here briefly, and the Gulf is gonna see some rain

One-sentence summary

Tropical Storm Lidia dissipated this morning over Mexico, but will bring rainfall and mudslides to part of the country; and its remains will merge with other moisture in the Gulf to bring rains later this week in the southern United States.

Tropics now: Goodbye Lidia, and hello Sean

After rapidly intensifying on Tuesday and slamming into the Pacific Coast of Mexico, Lidia has been shredded by the mountainous terrain of Central Mexico. The big concern with Lidia, accordingly, is now rainfall. The remnants of the system could cause urban flooding and mudslides in Western Mexico today.

After today, those remnants will be drawn into the Gulf of Mexico along with the remains of another Pacific storm, Max, as well as a warm front lifting north. This mess will eventually move to the northeast, toward Florida. We have zero expectations for these lows to congeal into something threatening from a tropical storm standpoint, but it should heighten rain chances for areas from Louisiana through Florida.

NOAA rainfall forecast for now through Friday. (Pivotal Weather)

Overall rainfall totals look fine, with 1 to 3 inches from Southern Louisiana along the Gulf coast all the way to the Tampa area of Florida. Some locations may see higher amounts, but this system will be pushed out of the region by Friday and Saturday as a broad front brings drier air into the southern United States. So, not a huge concern.

Hi Sean, Goodbye Sean

Tropical Storm Sean has formed in the Atlantic tropics, about halfway between Africa and the Caribbean Sea. This system is expected to piddle along for a few days before it gets swamped by wind shear this weekend most likely. It will not threaten land. That’s probably about all we need to say about Sean.

Tropics later

Beyond Sean there are some mildly interesting features that we are watching.

If this tropical system develops, it likely will be slow to do so. (National Hurricane Center)

The first of these is a tropical wave that just moved off of Africa, and should continue to move due westward through the weekend. The atmosphere isn’t overly favorable for development, so the National Hurricane System only gives this system a 30 percent chance of becoming a tropical storm over the next week. But eventually, and we’re talking at least a week to 10 days from now, this system might be something that eventually approaches the Leeward Islands. It’s not something I am really concerned about at all right now, but we will continue to watch it for you.

Beyond this, we probably need to be wary of some late-season development in the Caribbean Sea. Waters remain very warm in those sun-bathed seas, and there are some hints of potential storminess during the last 10 days of October. There’s not much of a threat to point to, just the potential for something to eventually spin up.

October 4, 2023 Outlook: Philippe to track toward Bermuda

One-sentence summary

Philippe is finally lifting north after lashing the Leeward Islands earlier this week, and it may move toward Bermuda as a tropical storm by Friday or so.

Philippe is disheveled, but not dead

Tropical Storm Philippe has a rather ragged appearance this morning, and it continues to struggle with wind shear. After proving to be a rainmaker for islands such as Barbuda and Dominica, as well as the Virgin Islands, the storm should finally find a passage north as a high pressure system gets out of its way. It has open water for a couple of days before it reaches the vicinity of Bermuda. So what will happen to the storm’s organization over the next two days?

A fairly disorganized Philippe on Wednesday morning. (NOAA)

There is a ton of uncertainty, as Philippe could use this brief window of opportunity to strengthen into a Category 1 hurricane, or it could essentially be wiped out. Given its initial disheveled state, it’s difficult to parse whether the storm will, in fact, get its act together. The official forecast from the National Hurricane Center splits the difference, calling for a strong tropical storm with 60 mph tropical storm winds as Philippe nears Bermuda. This seems like a reasonable best guess.

After interacting with Bermuda, Philippe should begin transitioning into an extratropical cyclone as it heads toward the Canadian Maritimes and northern New England. The primary threat there will be some additional heavy rainfall this weekend before the system dies out completely over Canada. Areas including Maine and Nova Scotia should continue to track the storm’s progress for a few more days until we can say au revoir to Philippe.

Five-day forecast track for Philippe. (National Hurricane Center)

Beyond Philippe: Some Pacific mischief?

After Philippe’s exit, the Atlantic looks quiet for a little while. The one feature we probably need to watch is a disturbance in the Pacific Ocean south of Guatemala that is likely to become a tropical storm over the next five days or so. Much of our model guidance indicates this will move across Mexico and into the Gulf of Mexico next week.

Area of interest in the Pacific Ocean. (NOAA)

This could bring some heavy rainfall to coastal areas of Mexico, as well as the Gulf coasts of Texas and Louisiana later next week. But we’re at the point where there is just the threat of this happening, rather than any certainty. We’ll continue to watch it for you.