Matt Lanza

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.

October 19, 2023 Outlook: Tammy toys with the Caribbean islands, while Norma rapidly intensified overnight in the Pacific

One-sentence summary

Tropical Storm Tammy and Hurricane Norma strengthened overnight, but the hope is that most of their impacts will be glancing for the Caribbean Islands (Tammy) and Baja or Sinaloa (Norma) heading into this weekend.

Atlantic Tropical Storm Tammy: Strengthening and will be a close call in the Lesser Antilles

We will start today in the Atlantic, where Invest 94L leveled up to Tropical Storm Tammy yesterday. Tammy now has 60 mph winds after strengthening overnight.

Tammy is strengthening this morning, but its center remains fairly displaced to the north and west of most of the thunderstorm activity. (Weathernerds.org)

I’m not sure I’d classify Tammy as well-organized this morning, but it’s something. Whatever the case, given the higher starting point now, it won’t take much for Tammy to become a hurricane from here. Much of the northern Lesser Antilles are under tropical storm watches this morning. This includes Barbados, Dominica, Martinique, Guadeloupe, Antigua, Barbuda, Montserrat, St. Kitts, and Nevis. With the strengthening this morning, I would anticipate we see watches expanding and some hurricane watches or warnings hoisted later today.

In terms of track and impacts, Tammy will start to turn later today, first west-northwest and then northwest. Given how far south it’s starting from and how far west it already is, it will likely run into the islands before turning northward enough, meaning direct impacts are likely beginning tomorrow. Tropical storm force winds will probably arrive tomorrow morning sometime in Barbados, spreading north and west through the day. Tropical storm force winds would most likely arrive in Puerto Rico and the Virgin Islands on Saturday.

Tropical Storm Tammy is expected to scrape the northern half of the Lesser Antilles. It should track east of the Virgin Islands and Puerto Rico, but impacts are still a possibility there. (NOAA NHC)

A stronger Tammy would be more apt to turn northward a bit faster, so that may be good news for Puerto Rico, which could (should?) end up being spared any kind of meaningful wind impacts from Tammy. Still, it’s close enough, and it’s not as if there will be no impacts. The weather in Puerto Rico looks active the next couple days regardless, with excessive heat in San Juan and the north coast today and some locally strong thunderstorms and heavy downpours today and tomorrow in interior Puerto Rico. Folks should continue monitoring Tammy at least, but the hope is it will be a close miss to the east.

Heavy rain will be possible in the Leeward and northern Windward Islands with anywhere from 2 to 6 inches of rain possible. The heaviest rain will miss to the east as long as the track stays close to forecast. If Tammy does somehow track closer, as much as 8 to 10 inches of rain would be possible for some of the islands.

Beyond the islands, Tammy will continue turning north and head out to sea, looking as if it will pass well south and east of Bermuda at this time.

Pacific Hurricane Norma: Rapidly intensifying but should weaken a good bit on approach to land

Shifting west now, and we’ve had some changes overnight in Norma. As has been the case a couple times this season, rapid intensification outpaced the forecast, as Norma is now a category 3 storm with maximum winds of 120 mph.

Hurricane Norma exploded into a major hurricane overnight with winds now of 120 mph and much more classic looking structure. (Tropical Tidbits)

The good news for land is that Norma is expected to weaken as it approaches the coast of Mexico. So while we have a major hurricane now, should it track toward Baja or Cabo, it will likely not be a major hurricane there. It may still be a hurricane however or close to hurricane intensity as it approaches Baja on Saturday and Sunday. Thus, a hurricane watch was issued for Baja.

Norma is expected to slow down and weaken considerably as it approaches Baja. While it may still be a hurricane as it approaches, it will become a moisture-laden tropical storm with heavy rain possible for the southeast tip of Baja and perhaps parts of Mexico. (Tomer Burg)

Ultimately, Norma’s biggest impact may be rain. Moisture from Norma will spread northward across Mexico and probably into Texas.

Click to enlarge a map of forecast rain through next week from Mexico into Texas and the Southern Plains. (NOAA WPC/Google Earth)

Rain totals through midweek next week may approach 1 to 3 inches in much of interior Texas north into Oklahoma and Kansas. Additional rain may follow late next week with a front. So overall, while Norma is rather potent this morning, the hope is that it will bring mostly beneficial rainfall. That said, interests in Mexico, particularly Sinaloa and Baja should continue to watch Norma’s progress closely.

October 17, 2023 Outlook: Invest 94L still may develop, while Invest 90E in the Pacific will likely develop and eventually track toward Mexico

One-sentence summary

Invest 94L is slightly better organized this morning in the Atlantic but still has a long way to go to develop, while Invest 90E is likely to develop today or tomorrow and will eventually be a concern for Mexico.

Tropics: Invest 94L

Thunderstorm activity improved around Invest 94L yesterday evening, and this morning, while it’s clearly heavily sheared, it actually has a bit of a nascent organizational “shape” to it.

Invest 94L, while heavily sheared this morning, is at least maintaining robust thunderstorm activity, a necessary precursor to development. (Weathernerds.org)

There’s clearly still a long way to go here, but 94L is at least taking baby steps toward organization today. Whether or not it maintains those baby steps or throttles back in reverse remains to be seen.

The track forecast has not changed much for 94L’s future. In general, if it can get its act together over the next day or two, there’s a good chance it will start to shift northwest faster. If it remains a discombobulated mess, it will probably track toward the islands with some impacts, albeit most likely on the lower-end of the intensity spectrum.

Invest 94L should track west or west-northwest toward the islands, unless it develops quickly, in which case it would follow the northern edge of that track density plot. (Tomer Burg)

This remains a system to keep an eye on in the Caribbean islands, but probably nothing to worry a ton over still at this point. We’ll continue to watch it closely through the week.

Pacific Invest 90E

Meanwhile, in the other ocean, Invest 90E is on the cusp of developing into a tropical depression or storm.

Invest 90E (center) is likely to become a depression or storm in the next 24 hours or so. (Weathernerds.org)

Invest 90E is a little more intriguing from a potential impact standpoint, as this is expected to organize rather considerably and track toward Mexico. This bears watching from southern Baja to northern Jalisco and Puerto Vallarta in Mexico.

Next significant U.S. weather event? Not for a bit

With a quiet stretch ongoing across the country much of this week, the question is: When will we experience our next significant weather event? Well, we may be looking at another 1 to 3 inches of rain this weekend in parts of the Northeast, an area that has seen below normal rain in portions of New Hampshire and Vermont and almost 200 percent of normal rain in portions of Southern New England and near New York City.

Rainfall since mid-August has been dramatically above normal in Southern New England and in the NYC metro, while it has varied in northern New England and across Upstate New York. Another 1 to 3 inches is expected this weekend. (High Plains Regional Climate Center)

So how wet your soils are depends a bit on where you live in the Northeast or parts of the Mid-Atlantic. I would suspect 1 to 3 inches of rain wouldn’t cause any serious flooding issues, but it’s something to watch.

Record warmth

California is set to experience a couple days of near record and record warmth for mid to late week. Thursday’s forecast highs show records in a few spots in interior California from east of San Diego all the way north to Medford, Oregon.

Any location boxed in on the map above is expected to see a record high temperature on Thursday. (Weather Bell)

Weak to moderate offshore winds will also help keep temps up overnight, allowing many locations to set or tie record warm minimum temperature levels on Wednesday night and Thursday night. Some of that record warmth will expand into the Desert Southwest and Texas heading toward the weekend.

But truthfully, aside from these items, it’s a quiet stretch for autumn here in the States. I suspect we will want to watch the Pacific tropical system and a potential cold front later next week for some more significant weather chances, but that’s a long way off. For now, enjoy the quiet.

October 16, 2023 Outlook: Invest 94L has a muddy future in the Atlantic, while the Pacific heats up a little

One-sentence summary

Invest 94L in the Atlantic is struggling as it continues to plod west toward the Caribbean, while Invest 90E in the Pacific has some potential to develop and impact Mexico in the next 7 to 10 days.

Tropical Outlook: Invest 94L’s on-again/off-again potential

It’s been interesting to watch Invest 94L over the last several days. We’ve seen cycles of model runs that are quite bullish on development, followed up by cycles of model runs that are not. We are currently in the latter, where model support has waned for Invest 94L’s development. That’s not say it’s impossible (the NHC still gives it 70% odds over the next week), but it is not looking nearly as robust as it did late last week.

Thunderstorm activity around Invest 94L is not exactly organized this morning. (Weathernerds.org)

On satellite this morning, you can see the convection (thunderstorm activity) this morning around 94L struggling a bit. There is no organization to this. It looked far better on Saturday, then collapsed yesterday. And here we are. Over the next 2 to 3 days it should plod west and will probably wax and wane in organization.

The total density track plot for 94L as of yesterday showed a broad track toward the Lesser Antilles, but low confidence in how much development we’d see on that path. (Tomer Burg)

Folks in the islands probably want to continue to monitor the progress of 94L, as it almost certainly tracks in that direction. Overall, 94L certainly looks less menacing than last week. But it still has a chance at becoming a tropical storm or better. Beyond the islands, 94L would probably turn north and eventually out to sea, assuming it organizes. We’ll keep an eye on it this week.

Elsewhere, Sean finally met its demise late last night. Sean tied for the 6th least amount of generated ACE this season in the Atlantic meaning it was not much of a storm. There are no current signs of any further activity behind Sean’s remnants and Invest 94L at this time.

Pacific outlook

The most interesting of the potential tropical systems in the Atlantic or Pacific is probably in the Pacific. Invest 90E seems likely to develop over the next couple days as it meanders over the open Pacific. Steering currents do suggest that this one will shift back north and eventually east toward the coast of Mexico at some point, so this bears close watching there.

From the Euro ensemble overnight, you can see a pretty basic calculus for Invest 90E. If it develops with some potency, it will likely turn north or northeast back toward Mexico. If it struggles, it may meander south of Baja offshore. (Weathernerds.org)

Much like in the Atlantic, a weaker storm would probably plod farther out to sea, whereas one that organizes more quickly would be apt to turn north and eventually northeast. Right now, given that 90E has pretty robust thunderstorm activity, the money may be on the latter outcome. We’ll see what we’ve got here over the next few days.

U.S. Weather update: Quiet but warming

We will have a pretty quiet week across the country this week, with no real serious weather to speak of. We will likely have some warm temperatures building out of the West, with some record highs and a number of record warm minimum temperatures later in the week.

Temperatures will begin the week cool in the East, but building warmth in the Western U.S. is likely to spread eastward as the week goes on. (Weather Bell)

Otherwise, it looks pretty quiet for most of this week across the country!