Uncategorized

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.

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.

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.

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.

Beyond Tammy, happily, the Atlantic tropics look quiet.

One-sentence summary

Tammy continues to provide some uncertainty, and Otis will come ashore near Acapulco as a hurricane tomorrow, while the U.S. sees its first big winter storm in the North that will help usher in a round of colder air.

Tropics: Tammy being tricky, while Otis approaches Acapulco tomorrow

Hurricane Tammy continues to plod along in the southwest Atlantic moving northeast just under 10 mph. It continues to take on a less than classic look for a hurricane, but it is still maintaining hurricane intensity.

Tammy still has just a handful of showers trailing it into the islands, but otherwise, impacts from Tammy are limited to rough surf and rip currents at this time. The forecast track for Tammy continues to fan out all over the Atlantic, as various features that will dictate Tammy’s future track remain a bit uncertain.

This is one of the sloppiest tropical system forecasts I’ve seen this year. The 180° spread in options is one of my least favorite ones to manage during hurricane season. Thankfully, the stakes are not as high in late October usually, and in this instance there is good agreement among the models that Tammy will slowly weaken such that most impacts to either Bermuda or the Bahamas and Florida would be modest at worst. We will keep an eye on things regardless, but at this time, Tammy is not an overly serious concern down the line.

Meanwhile, in the Eastern Pacific, Otis is likely to become a hurricane. Very few storms have not outpaced their forecast intensity this year it seems in the East Pac, and Otis will be another.

Otis should become a category one hurricane tonight or tomorrow before making landfall in the state of Guerrero in Mexico, probably just west of Acapulco. Hurricane warnings are up for the coast of Guerrero, with tropical storm warnings extending southeast into a portion of Oaxaca.

Beyond Otis, the Pacific should quiet down some.

Elsewhere in the tropics, things look fairly quiet. Tropical Depression 21 formed near Nicaragua yesterday and is ashore this morning, producing areas of heavy rain for Central America. There are no other serious things to watch at this time heading into the rest of the week.

U.S. Weather: Significant northern tier winter storm will usher in colder air that eventually spreads south and east

Winter Storm watches and warnings are posted from Washington across Montana and into North Dakota today as the first real big winter storm of the season gets going in the U.S.

Snow and cold temperatures will kick into gear across central and western Montana, with 8 to 12 inches of snow possible for places like Great Falls.

Over the next 3 days, snow will likely spread into North Dakota, and the current 50th percentile forecast for the next 72 hours will be 8 inches or higher there

Snow should expand north into southern Manitoba and southeast Saskatchewan as well. Travel will be pretty rough across the northern tier over the next couple days. The first significant storm of the season always usually causes extra travel headaches too, so if you plan to be up north at all this week, take it easy.

It will turn quite chilly behind this storm over the next few days, with much below average temperatures across Montana and Alberta. Cool temperatures will expand into the Dakotas and much of the West Coast as well.

A handful of record lows are possible up that way. Meanwhile, downstream from the storm, extremely warm temperatures will dominate with numerous record warm low temperatures expected over the next few days.

Beyond this, a more potent south and east push of colder air is likely next week, erasing most of the warm weather for now in the Central and Eastern U.S.

Halloween should be a cooler one in much of the Central and Eastern U.S.

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.

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 islands—Cuba, 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.

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?