October 30, 2023 Outlook: Hurricane season won’t exactly go away quietly

One-sentence summary

The tropics refuse to go away quietly, with Pilar in the Pacific and a potential Caribbean system later this week that bears watching in Central America.

Atlantic update: Invest 96L unlikely to do much, but the Caribbean bears watching later this week

We are watching two areas in the Atlantic at the moment: Invest 96L near the Bahamas and a yet-to-develop system in the Caribbean. Let’s run through them.

Invest 96L

Though this is the most immediate item on the menu, it’s not the most notable. 96L was found with gusty winds but no real circulation to hone in on yesterday, so it remains just a disturbance. But it’s about to get smacked in the face by dry air and wind shear, as the much discussed significant U.S. cold front comes sweeping offshore tomorrow.

Invest 96L will soon run out of time to develop east of the Bahamas, as a cold front will sweep it away. (Weathernerds.org)

This should knock 96L out to sea and probably prevent any real development at all.


Despite their noisy operational guidance shows, both the GFS and European models are in decent agreement right now that a surface low pressure system is going to form in the Caribbean around midweek. It will drift west in the coming days toward Central America. Both sets of ensembles (which run the models 30 to 50 different times) show a favorable setup for development, but the GFS is tending to run “hot” right now, developing it slowly but intensely as it comes west. The Euro? Not so much. But this has been an issue throughout hurricane season. The GFS does tend to overcook Caribbean systems this time of year, and the Euro has tended to have an underforecast bias when it comes to intensity. To me, that argues for some type of developing tropical system in the western Caribbean by the weekend.

The average of all the GFS ensemble members for Wednesday evening shows a developing system south of Hispaniola in the Caribbean, likely to track due west or even west-southwest. While the GFS operational may be too aggressive at this point, this system will bear close watching in Central America. (Tropical Tidbits)

In general, I would expect this system to be steered generally west, if not even a little south of west around the periphery of sprawling high pressure that will extend from south of Bermuda across the Bahamas toward Cuba and the Yucatan this weekend. Exactly how far west this gets, how strong it gets, and where (if) it makes landfall is to be determined, but interests from the Yucatan and Belize south into Honduras and Nicaragua should probably be watching this rather closely in the meantime. We’ll update with the latest tomorrow.

Pacific Update: Pilar will likely bring heavy rain to El Salvador

Tropical Storm Pilar formed last night in the eastern Pacific. Over the next couple days it will drift toward El Salvador and Honduras. Tropical Storm Watches are posted there and Nicaragua. Pilar is not currently expected to become a hurricane, and it will primarily bring tropical storm conditions and heavy rain to the Pacific coastal communities between Guatemala and Nicaragua. Heavy rain could cause flooding and mudslides in some of these areas.

Pilar will take a funky track toward El Savador and Honduras over the next 36-48 hours before pulling a 180 and heading out to sea. (Tomer Burg)

Elsewhere in the East Pac, we don’t expect any significant development through the week.

U.S. Weather: Frost & freeze & Santa Ana winds in California

If you look at a National Weather Service hazards map of the U.S. right now, one thing sure stands out: Frost and freeze alerts all over the place. Freeze warnings extend from the Mexico/New Mexico border up into Ohio and Pennsylvania.

Freeze warnings extend from Arizona and the New Mexico border with Mexico up into Pennsylvania this morning. (Pivotal Weather)

Some cold nights are ahead this week with the first true wintry-type air mass of the season across the Lower 48.

And as is often the case, when cold air dumps into the Rockies and points east, Santa Ana winds are kicking up in California, leading to warm weather and critical fire danger today, particularly in the higher terrain around Los Angeles and into Ventura County.

A fairly classic Santa Ana wind pattern across metro SoCal today. The strongest winds and highest fire danger today will be in the mountains around LA, as well as in Ventura County. (Pivotal Weather)

We’ll hope for nothing serious in that part of the country. Winds should settle down on Tuesday.

Otherwise, it looks like a relatively quiet week nationally. A storm will enter the Pacific Northwest around Thursday, bringing heavy rain and mountain snow. Snow levels will be relatively high with these storms. That may be followed by a second or third system this weekend.

Mostly welcome precipitation over the next week will be fairly considerable from northern California into the Northwest, though snow levels will be a bit high. (Pivotal Weather)

We’ll keep tabs on all that as well.

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 24, 2023 Outlook: Otis should impact Mexico as a hurricane, while a significant winter storm impacts the northern U.S. and southern Canada

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.

Hurricane Tammy certainly looks a little ragged, but it is expected to intensify a little more before beginning to transition into an extratropical system. (Weathernerds.org)

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.

There remains significant uncertainty on Tammy’s future track in the Atlantic. (Tomer Burg)

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 is much healthier looking than Tammy as it approaches hurricane intensity and a likely landfall tomorrow near or west of Acapulco in Guerrero, Mexico. (Weathernerds.org)

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.

Otis should track near to Acapulco tomorrow as it makes landfall as a hurricane. (NOAA NHC)

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.

Winter Storm watches & warnings are posted for the northern Cascades and much of Montana (extending into North Dakota) as the season’s first major winter storm kicks into gear. (Pivotal Weather)

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.

Significant snow is likely across interior Montana later today and tomorrow, along with gusty winds. As much as 8 to 12 inches is expected over a rather large swath of the region. (NWS 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 of 8 inches or more should spread across North Dakota and into southern Manitoba. (NOAA WPC)

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.

Cold weather will take hold behind this storm in the northern Rockies and Cascades, as well as in much of southwest Canada. (Weather Bell)

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.

An aggressive push of colder air is likely in the Plains and portions of the Upper Midwest next week, with cool temps expanding south and east from there. (NOAA CPC)

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

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?