Matt Lanza

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 23, 2023 Outlook: Tricky Tammy, Otis in the Pacific, and some heavy rain in the Southern Plains

One-sentence summary

Hurricane Tammy will take an unconventional track over the next few days, but it is expected to peak in intensity before weakening by the time it could maybe threaten land again.

Atlantic tropics: Tammy, Tammy, Tammy

Tammy has shifted north of the islands now, and it is unlikely to directly impact any land significantly for the foreseeable future. That said, there are still a lot of questions with Tammy’s future track. For one, how far north will it get before it turns west? This will have implications for Bermuda. And for how long will it maintain tropical characteristics?

Tammy is expected to track northeast and intensify the next day or two before running into some issues and hooking back west somewhere southeast of Bermuda. (NOAA NHC)

For now, the general thought is that Tammy will move north and northeast over the next couple days and strengthen some before slowing down and cutting back west while losing tropical characteristics. Some models do continue to push Tammy north and northeast out of the picture entirely, so there is a pretty healthy degree of uncertainty still. If this were September, I might be more intrigued and concerned by this, but given how late in the season it is, the stakes are probably not as high. Modeling is in good agreement that Tammy will peak in intensity early this week before weakening. Ultimately, we can probably just observe Tammy from afar without much more than bemusement at this point. That said, interests in Bermuda, the Bahamas, and Florida probably want to check back in on this through the week to make sure all is going to plan.

In the meantime, you can see some heavy thunderstorm activity remaining over the northeast Leeward Islands this morning. That should subside this afternoon as Tammy puts more distance between itself and the islands.

Tammy has plenty of moisture and thunderstorms with it, but it is definitely not the most classic looking hurricane. (Weathernerds.org)

Elsewhere in the Atlantic, Invest 95L is right off the coast of Central America and it has the potential to become a short-lived depression or storm before it moves inland tomorrow. In the interim, 3 to 6 inches of rain could fall in Nicaragua over the next day or two leading to some flash flooding.

Rain totals in Central America will be on the order of 2 to 6 inches, with the highest amounts in eastern Nicaragua. (Weathernerds.org) Editor’s note: I accidentally mislabeled Costa Rica as Panama in this image. My apologies!

Beyond Tammy and 95L, we don’t expect any other development in the Atlantic this week.

Pacific tropics: Mexico may notice Otis

Meanwhile, the Pacific is calming down a bit, but not before we deal with Tropical Storm Otis. That one is not currently expected to grow beyond tropical storm intensity as it tracks north and northwest toward the coast of Mexico this week.

Tropical Storm Otis is expected to make landfall later this week on the coast of Mexico near-ish to Acapulco. (NOAA NHC)

It’s expected to come in probably in Guerrero, not far from Acapulco. We’ll keep an eye on this through the week, but as of now, tropical storm watches are posted for a chunk of the Mexico coast.

Texas and Southern Plains rain

Just a quick closer today on the rainfall expected this week in the Southern Plains. Portions of west Texas up into Oklahoma are in the “slight” risk for excessive rainfall today and tomorrow (level 2 of 4). Locally heavy rain will occur in central and west Texas up into southern Oklahoma the next couple days.

Locally heavy rain may cause localized flash flooding in portions of west or central Texas and Oklahoma this week. (NOAA WPC)

Total rainfall over the next 3 days could exceed 4 inches portions of this area.

Anywhere from 2 to 5 inches of rain is possible from the Permian Basin of Texas into Oklahoma over the next few days. (Pivotal Weather)

For the most part this will be welcome rainfall in these areas.

Tomorrow, we’ll talk more about snow from Washington into Montana, as well as the potential for some chilly air to invade later this week and next week.

Quick Saturday check up on Tammy and Norma

One-sentence summary

Hurricane Tammy is scraping the northern half of the Lesser Antilles with tropical storm and isolated hurricane conditions through the day, while Norma is about to make landfall near Cabo as a formidable hurricane.

Hurricane Tammy scraping the Lesser Antilles

When you look at satellite, it’s kind of hard to believe that Tammy is a hurricane, but here we are!

Hurricane Tammy is just to the east of the Lesser Antilles and moving northwest. (Weathernerds.org)

Tammy has maximum winds of 80 mph, but as you can see from the satellite loop above, thankfully the majority of thunderstorm activity is east of the islands. This will help mitigate impacts a bit there through the day. However, with Tammy still having a bit of a westerly component to its track, some of that core that’s just east of Guadeloupe will probably begin to enter the islands. So from about Martinique northward, conditions could deteriorate through the day some.

Hurricane Tammy is expected to enter the islands today and exit tomorrow evening. (NOAA NHC)

The strongest winds from Tammy may occur near Antigua and Barbuda, and that’s where I’d put the highest odds of seeing some gusts closer to hurricane force. Otherwise, tropical storm conditions will impact the northern half of the Lesser Antilles. Heavy rain is also likely and flash flooding or mudslides in mountainous terrain will be a possibility.

For the Virgin Islands and Puerto Rico, the strongest winds should stay comfortably east of there, and the main concern will be rough surf, rip currents, and heavy rain. Today is another day with an elevated risk of excessive rainfall in most of Puerto Rico and the Virgin Islands.

Excessive rainfall has an elevated chance of leading to flash flooding across much of Puerto Rico and the Virgin Islands today. (NWS San Juan)

As Tammy lifts north, uncertainty in the track increases, but for the islands, conditions should improve into late Sunday and Monday.

Hurricane Norma about to make land in Cabo

Norma remains a hurricane this morning, with maximum winds of 110 mph. It is gradually weakening, but will still come ashore very soon in Cabo as a hurricane.

Norma is about to make landfall in Cabo as a formidable hurricane. (NOAA NHC)

Norma will continue off to the north and east tonight and tomorrow before dissipating over Mexico on Monday. Conditions should improve in Baja and Cabo tonight. Tropical storm conditions are expected in Sinaloa tomorrow with rain arriving earlier than that.

October 20, 2023 Outlook: Tammy and Norma deliver their impacts this weekend before the tropics quiet down some

One-sentence summary

Tammy will impact the Lesser Antilles with gusty winds and heavy rain this weekend, while Norma clips Baja tomorrow as a fading hurricane.

Tropical Storm Tammy will scrape the northern Lesser Antilles before heading out to sea

Tammy remains a 60 mph tropical storm this morning, and it is one that is struggling a bit to really get itself in a mode to intensify quickly. That’s good news for sure, but a slow intensification remains likely, so Tammy is expected to still become a hurricane over the Leeward Islands tomorrow.

Despite having a very robust area of thunderstorms, Tammy’s center is displaced a bit to the west side of most of the activity, indicating that it’s a formidable but slightly disheveled storm. (Weathernerds.org)

You can see from the satellite image above that the majority of Tammy’s storms are displaced somewhat to the east of the center. This spares most areas for now, but that will likely change as Tammy creeps northwest.

Numerous watches and warnings are posted for the Lesser Antilles and conditions are expected to be at their worst over the next 36 to 48 hours before Tammy lifts north enough to start pulling away.

Tammy is expected to become a hurricane tomorrow as it begins to (slowly) exit the Lesser Antilles. Impacts are likely in the northern half of the island chain. (NOAA NHC)

What to expect in the northern half of the Lesser Antilles? Obviously you’ll see rough surf and some high tides there. Tropical storm force winds will approach from the south and east into tonight and tomorrow. At this time, I don’t necessarily expect much wind to get any farther west than Anguilla or St. Kitts and Nevis. Obviously, continue monitoring Tammy this weekend in Puerto Rico and the Virgin Islands, but for now any direct wind impacts seem minimal to unlikely.

With Tammy’s thunderstorm activity a bit lopsided to the east and a track taking the center near or just east of the Lesser Antilles, the heaviest of the rain will also probably stay east of most of the islands. Still, locally heavy rain is likely with flash flooding a possibility across the northern islands and even perhaps into Puerto Rico and the Virgin Islands as well. There is an elevated risk of excessive rainfall across Puerto Rico today from isolated to scattered thunderstorms. That risk may continue this weekend even with Tammy staying comfortably east of the region.

The European model rainfall forecast shows the axis of heaviest rainfall missing most of the islands, but still anywhere from 30 to 60 mm (1-2″+) of rain falling across the islands, some of which may fall quickly and produce localized flooding. (Weather Bell)

Tammy will exit north of the islands by the end of the weekend. While it’s expected to slowly head out to sea, Tammy might get left behind well north of the islands, allowing it to meander over the open Atlantic. Tammy will intensify further north of the islands until shear begins to enact a toll on Tammy next week. Despite being comfortably away from land, Tammy may continue to produce rough surf on the north-facing shores of the Caribbean islands.

Hurricane Norma has peaked but it will deliver impacts to Baja and Sinaloa

Norma has peaked in intensity and is now slowly weakening. That said, it’s still a category 3 hurricane with 115 mph maximum sustained winds.

Hurricane Norma is beginning to feel the effects of shear and slightly drier air as it comes north and a slow weakening will continue (Weathernerds.org)

Despite this downward trend in intensity, Norma is still expected to be a hurricane as it approaches Baja on Saturday. Norma will come close to making landfall in Baja before curving to the east toward mainland Mexico and coming ashore there as a tropical storm or depression.

Heading to Cabo this weekend? Check ahead to make sure everything is copacetic, but impacts there should be moderate with gusty winds and heavy rain.

Total rainfall of 4 to 8 inches is likely in southern Baja, heaviest to the north and east of Cabo, with another 3 to 6 inches possible on the coast of Sinaloa in Mexico. (NOAA WPC/Google Earth)

Rain totals are shown above for Mexico, with the heaviest rain on the southeast tip of Baja and in coastal Sinaloa.

Winds of hurricane-force are possible in Baja as Norma passes but mostly tropical storm type impacts are expected from wind.

What weather is on our radar for next week?

Next week looks a little more active across the U.S., but the tropics should settle down. Here are the things we’ll be watching.

Tropics: What exactly does Tammy do in the Atlantic? We expect Tammy to go north and out to sea, but as noted above, a handful of models do “trap” it between the Caribbean islands and Bermuda. This would not impact land at all, but it might inject some forecast uncertainty into the picture. Beyond that, we don’t expect any other real notable systems in the Atlantic or Pacific.

Rainfall: There should be a substantial amount of rain with a cold front and some moisture from Norma and the Pacific across portions of Texas into the Plains early to mid next week.

Rain totals of 4 inches or higher are possible in North Texas and Oklahoma near the Red River next week. You can also see this weekend’s heavy rain in the Northeast, locally heavy rain in the Upper Midwest, and the fingerprint of snow risk in Montana above. (Pivotal Weather)

Totals of 1 to 4 inches with isolated higher amounts seems reasonable.

Severe storms: Significant severe weather is not expected next week, but we will keep tabs on the Plains for some isolated potential with a stalled out front in the area.

Snow: There is some potential for a healthy dose of snow in portions of Montana’s mountains, specifically near Glacier National Park and the Lewis Range next Wednesday and Thursday. There’s a slight chance some of that will expand into other high terrain south and east of Glacier late next week.

Heavy snow is possible in portions of Montana midweek. (NOAA WPC)

Temperatures: Ahead of the cold front next week, we have the potential to set some record warm minimum temperatures in the Central U.S. into Texas. Nothing too extreme, but it will not feel like autumn everywhere.