Wednesday evening update: Humberto cast as lead actor with the dueling southwest Atlantic disturbances

In brief: Invest 93L was upgraded to Tropical Storm Humberto this afternoon, and it is not currently expected to threaten land. Invest 94L’s forecast remains directly related to Humberto and has a very high degree of uncertainty. This will continue to be a low-predictability situation for another couple days at least.

I think this is the first time all hurricane season we’ve done two posts in a day? We’ll call that a win. Anyway, this will be brief, but I want to catch you up on some changes today.

93L is now Humberto

Humberto will move and strengthen quite slowly over the next few days before perhaps threatening to become a major hurricane by early next week. (NOAA/NHC)

In a case of again dispensing with formalities, we took Invest 93L and skipped the tropical depression status and jumped right to tropical storm classification. Tropical Storm Humberto has winds of 40 mph. It’s certainly not the worst looking tropical storm we’ve ever seen.

Tropical Storm Humberto slowly gathering itself northeast of the Islands. (Weathernerds.org)

Thankfully most land will not likely need to worry about Humberto. However, interests in Bermuda should continue to monitor this storm’s progress. Various tropical models and most ensemble guidance curves Humberto on a trajectory similar to Erin earlier this summer, which would keep it west of Bermuda. However, depending on how well organized the system is, it could produce some meaningful impacts by early next week in Bermuda. Stay tuned.

Invest 94L

Meanwhile, the one we’re watching a little more closely, Invest 94L remains in the Caribbean. It was initialized this afternoon very near the southwest tip of Puerto Rico.

Invest 94L looking very disorganized but very stormy this evening. (Weathernerds.org)

But you can see that there are clusters of thunderstorms both north and south of the island. The system is quite strung out at the moment. While the surface reflection may be near Puerto Rico, there is clearly some sort of mid-level and upper-level reflection elsewhere. You’d like to see a system better vertically stacked before it can organize, but at this moment in time, 94L is anything but that. So, don’t expect this to pull a Humberto we wouldn’t think.

We have a good 2 to 3 days before this clears Hispaniola and makes it into the Bahamas. At that point, assuming it is not shredded by the mountains of Hispaniola, we would likely begin to see an environment more conducive to organization. Much like this morning, the frustrating reality is that we have no real clue what happens next. The operational model guidance is definitely dropping options though.

The GFS seems to favor a Fujiwhara interaction between 94L and Humberto, which would potentially pull 94L toward Humberto and pull Humberto a little farther west (offshore of the East Coast) before it all heads out to sea.

You can see how Humberto basically pulls the weaker 94L into its orbit on the GFS model, a scenario that while plausible isn’t any more likely than other scenarios. (Weathernerds.org)

This scenario is a realistic one for sure, but I’m not sure it’s any more likely than other possible scenarios. The European model basically leaves 94L behind once Humberto heads out to sea and does weird things with it, which again is plausible but not necessarily likely. Other options include literally nothing, a storm going up the East Coast, or just a storm that follows Humberto out to sea. Put all that together, and we’re still very much in “choose your own adventure” mode with regard to 94L’s future. Stay tuned, but I don’t expect much clarity on this for at least another day or two.

Notably, regardless of what transpires here, there will begin to be some heavy rain risk in the Carolinas and Virginia in about 3 or 4 days. After Helene last year, I know this won’t give people warm and fuzzies, but just bear in mind that this is a much different scenario than Helene from an entirely different direction. Certainly, keep tuned to the forecast, particularly near the coast, but we just want to offer a little reassurance that anything remotely like that is not currently in the cards on any model guidance.

The rainfall forecast over the next week calls for 1 to 3 inches, with isolated 4-to-5-inch totals in eastern Virginia and interior North Carolina, east of the mountains. (Pivotal Weather)

Rain totals of 1 to 4 inches are broadly forecast across Virginia and North Carolina down to about Columbia, SC over the next week. Notably, this is east of the mountains.

More tomorrow.

Twin tropical waves continue to bear watching in the coming days in the southwest Atlantic

In brief: The Atlantic Invests 93L and 94L will continue giving forecasters fits in the coming days as their proximity to one another, their sensitivity to how well organized one or the other gets, and their proximity to land will play a role in everything that ultimately happens. With so many moving parts, it’s tough to define a narrative of potential outcomes right now, so we walk through what we know and more importantly what we do not.

Twin Invests 93L and 94L

Both Invest 93L and 94L have high chances of developing in the coming days. And the situation has grown no less complicated.

Both invests look less well organized than they did 24 hours ago. (Weathernerds.org)

The first thing I can say with some confidence about all this is that we are looking at a somewhat lengthy process here. We may be watching these systems for the next week. While Invest 93L seems likely to not be a land threat (though it could tease Bermuda), it may ultimately help influence Invest 94L, which could be a land threat on the Southeast or Mid-Atlantic coasts.

Invest 93L

First off, Invest 93L is the better looking of the two this morning, and all along it has been the more likely of the two to develop. Still, we’re not there yet. It seems 93L is dealing with the broader circulation on the backside of Gabrielle, as well as a pocket of wind shear impinging on its southwest flank. It’s just not in an optimal location at this particular moment, so we’re probably still a day or two away from this getting together into something more formal.

Both the European ensemble suite and AI modeling supports 93L sitting somewhere a few hundred miles north of the Caribbean islands on Saturday evening, probably beginning to strengthen. (Weathernerds.org)

So that’s in about 84 hours. Beyond this point, the general idea is that 93L should continue off to the northwest before turning northward near or southwest of Bermuda. The only real unanswered question with 93L is whether it ultimately threatens Bermuda. Models keep it southwest of the island, so depending on how well developed, how strong, and how close it comes to the island will determine how significant the impacts are. Suffice to say, interests in Bermuda should monitor the progress of 93L.

Invest 94L

Meanwhile, the same cannot be said about Invest 94L. There is virtually nothing we really can say about Invest 94L with any strong confidence one way or another. The spread by Sunday morning in ensemble members with 94L is much wider and the intensity is a good deal lower than 93L at that point. So there is going to inherently be more uncertainty on location because it will probably be a somewhat sloppy system.

The potential location of 94L’s center is much more uncertain than 93L on Sunday morning, and the intensity is likely still on the lower-end. Confidence in any specific forecast outcome is very low. (Google Weather Lab)

In theory, the track of Invest 94L should be more longitudinal in nature by the time we get to Sunday or Monday. Low pressure over Appalachia, high pressure near Bermuda, and a general south to north upper air pattern would theoretically allow 94L to track north or north-northwest by then. But this is partially where Invest 93L’s potential input on this outcome begins to come into play. If 93L is well-developed, it could force 94L to remain buried in the Bahamas for a couple days, could force it to remain weak, or it could even absorb it completely (the 00z GFS model showed this). If 93L struggles, then almost all bets are off.

By the time you get to midweek next week, there is just an enormous spread of possible outcomes with 94L.

Twinvestment advice

If you live in Bermuda, the Bahamas, or on the East Coast between Florida and New England, you will want to continue to follow this forecast each day. I really cannot emphasize enough how uncertain it is. When you get two systems like this close together, weird things can happen. Anything from a significant land impact to much ado about nothing remains in play. Stay tuned.

Hurricane Gabrielle

Elsewhere, Hurricane Gabrielle remains a major category 3 storm today as it tracks toward the Azores Islands, where a hurricane warning has been issued.

Gabrielle is expected to lose tropical characteristics as it moves through the Azores but it will bring hurricane-force winds to the islands. (Polarwx.com)

Gabrielle should cross through the islands tomorrow night delivering hurricane impacts. As it continues to move over cooler water, it will likely steadily weaken. That said, it will also get a jet stream “boost” as it passes the islands, allowing for hurricane-force winds to continue there. Hence the hurricane warnings. Gabrielle will fully lose tropical characteristics after it passes the Azores and approaches the Iberian Peninsula this weekend as a remnant low.

European model forecast for Sunday morning showing Gabrielle’s remnant hugging the coast of Portugal but tracking southeasterly. (Tropical Tidbits)

It will still be capable of bringing some gusty winds and rain to Portugal or Spain, but the current forecast track does keep the strongest conditions offshore right now, with the system tracking into the Gulf of Cadiz and near the Strait of Gibraltar. Still, probably something worth watching for Portugal at least! Rain would be welcome, especially in the northern half of Portugal which is experiencing a serious drought.

A delicate ballet will unfold in the southwest Atlantic over the next several days but the choreography is far from determined

In brief: As Gabrielle heads out to sea and toward the Azores, we’ll begin to pay close attention to two newly minted Invests, 93L and 94L in the southwest Atlantic. The whole pattern bears watching for the East Coast over the next week or so. But uncertainty is extremely high, with a lot happening over a small area and any one feature having impacts on the others. We explain the delicate ballet unfolding today.

Major Hurricane Gabrielle

(NOAA/NHC)

We’ll be quick on this one. Gabrielle intensified into a category 4 storm with 140 mph winds. The storm has probably peaked in intensity now and is going to move eastward out to sea.

Gabrielle is a very classic looking Atlantic hurricane as it begins to move out to sea. (Tropical Tidbits)

The next questions for Gabrielle are how it will impact the Azores and if it can make it to Europe. Gabrielle should remain a fairly formidable, albeit less intense storm as it moves near the Azores on Thursday or Friday. More details to come on that. It’s still a bit too soon to say how it will impact Europe, but it’s possible a remnant low approaches Portugal by early next week. In the near-term, interests in the Azores should be monitoring Gabrielle’s progress.

Atlantic Invests

The two disturbances we’re watching in the Atlantic are less than 1,000 miles apart, and both look fairly healthy this morning. (Weathernerds.org)

The area in the Atlantic with higher development odds right now is Invest 93L. This trailing disturbance has a 90% chance of development. Invest 93L has a similar look and feel to Gabrielle right now, and the models are indeed latching onto a higher chance that this develops by Thursday. Invest 94L will be moving into the Caribbean over the next couple days, so it’s likely that land interaction will inhibit its development. By Thursday morning, we expect to see 93L northeast of the islands and probably on the way to becoming a tropical depression. Invest 94L should be in the Turks and Caicos Islands or near Hispaniola as a tropical wave/disturbance.

Google AI and European ensemble model forecast locations of the two invests on Thursday morning (Google Weather Lab)

Up to this point, the forecast should be rather straightforward. Beyond this point?

There are about a million things that could happen after Thursday or Friday. The complicating factors right now include a.) What happens to 94L in the islands? That will help determine how far west it can get before being tugged north. b.) How strong does 93L get and how fast? That could help determine where it’s placed relative to 94L by the weekend which could influence both the track and development of 94L; they are fairly close together after all. c.) What about the trough in the Southeast? Will it be progressive enough to try to “capture” 94L and pull it into the Southeast or Mid-Atlantic? Or will it leave 94L stuck between a rock and a hard place with little opportunity to maneuver?

The upper air pattern in the southwest Atlantic is an utter mess this weekend, which means forecast uncertainty increases dramatically. (Tropical Tidbits)

The bottom line in all this is that there is a *lot* of uncertainty in the pattern this weekend. Inject two possible tropical systems into the mess, with all these players residing over less than 1,500 miles of distance and you have a recipe for extreme uncertainty. As the Southeast trough exits, it could theoretically “capture” the disturbance and pull it more north or north-northwest toward the Southeast or Mid-Atlantic coastline by Sunday or Monday. Or later. And I think that’s where much of the concern sits right now in terms of land impact. It’s one of several possible outcomes. Folks on the East Coast from Florida through New England should monitor the progress of these systems in the next few days to see if we can pull a signal out of this. Because right now, we can’t.

A spaghetti plot of Google AI ensembles shows a “choose your own adventure” outcome by early to mid-next week. (Weathernerds.org)

Bottom line: No one has any idea what these are going to do, and all you can do at this point is monitor the forecast and make sure you check on your hurricane plans and kits on the East Coast.

In the very near-term, Invest 94L will bring heavy rain to Puerto Rico and the Virgin Islands today.

(NWS San Juan)

Localized flooding is a possibility in the heaviest rains. This will continue tomorrow and Thursday as well, easing up by Friday and Saturday.

Atlantic Tropics shifting into a potential busier mode over the next 10 days

In brief: Gabrielle became a hurricane and then a major hurricane overnight and this morning. It should head out to sea now, but it may bring some impacts to the Azores or even Europe eventually. Disturbance 1 from the NHC carries a 70% chance of development and is currently not a serious land threat. Disturbance 2 from the NHC carries a 40% chance of development and has a high degree of uncertainty in its forecast heading toward the weekend. We explain it all below.

Things have escalated a bit in the tropics, but there are still more questions than answers in some cases. Let’s walk through the development areas and explain what we know in each case.

Major Hurricane Gabrielle

(NOAA/NHC)

Last week we were scoffing at how paltry Gabrielle looked. But we said despite that it had a chance to become a hurricane, if not a major hurricane by Sunday or Monday. Well, here we are, and we got our major hurricane. Gabrielle has maximum sustained winds of 120 mph this morning, and it looks spectacular.

A static satellite image of Gabrielle this morning shows a well-organized storm with ample thunderstorms around its eye. (Tropical Tidbits)

Gabrielle is in a bit of a precarious position, as it moves over much warmer than normal water. The water will be gradually cooling, however as it moves north and northeast. Still, Gabrielle has a good 24 hours in a favorable environment, and we could see it take a quick run at category 4 intensity this afternoon before peaking. From here, Gabrielle strolls out to sea and slowly weakens.

That said, Gabrielle probably won’t fizzle out. Impacts from Gabrielle are possible in the Azores by Friday and perhaps even in Iberia by Sunday or Monday. Exactly what those impacts will be are TBD. Uncertainty in the forecast from the Azores to Europe increases with time in Gabrielle’s forecast.

70% chance of development area

I want to preface this by saying that there are two distinct disturbances in the Atlantic, and the models are still sorting things out with each one. For now, I’m going to focus on the Central Atlantic one discussed here as the most likely to develop and also farthest east. A tropical wave in the central Atlantic is carrying a 70 percent chance of development over the next week as it comes west and northwest.

The next wave to watch will move north of the islands later this week. (NOAA NHC)

This system will be interesting, though I’m not particularly concerned about it making landfall right now. That said, it bears some watching. We’re still several days away from it getting north of the islands and south of Bermuda. But when it gets to that area, the upper level pattern is supportive of a system that moves slowly, possibly even stalling out. High pressure will block its exit east, at least initially, and a trough over the Southeast will sort of inhibit westward movement.

Upper-level pattern supports a system slowing or stalling south of Bermuda and north of the Caribbean islands by the weekend. (Tropical Tidbits)

On the one hand, the high is expected to eventually weaken enough to allow for an exit out to sea, possibly by Tuesday or Wednesday of next week. On the other hand, systems that stall out inherently have high uncertainty and bear watching. If one of the puzzle pieces currently in place in the forecast ends up shifting, the overall outcome could also shift. For now, I would say continue to monitor this system, but it’s probably not worth losing sleep over at this very moment.

40% chance of development area

And then ahead of the above discussed area, we have another area to watch. This one is carrying a 40 percent chance of development over the next week.

The third system is a disturbance with a 40 percent chance of development over the next week. (NOAA NHC)

Looking on satellite, both the previously discussed disturbance and the leading one look fairly healthy. The trailing the disturbance is in a slightly better environment, hence the better odds right now.

Satellite imagery of two NHC identified areas of interest in the Atlantic. (Weathernerds.org)

The leading disturbance discussed here will probably track off to the northwest, staying fairly low-end over the next 2 to 3 days. In fact, by Thursday, 1 Google Deep Mind ensemble member develops this area, while about half develop the trailing wave with higher odds. This disturbance has to deal with a bit more shear and also Gabrielle’s wake a little more. However, by Saturday evening, a little under half of the Google ensembles develop this disturbance near or just east of the Bahamas.

A number of Google AI ensemble members develop the 2nd disturbance by Saturday night in some fashion near or just east of the Bahamas. (Weathernerds.org)

Notably, about the same percentage of European ensemble members are doing the same thing here. So there is growing model support for something in this area in about 6 days. What it looks like, what it is, what its impacts will be? We don’t know yet. But interests in the Bahamas and Turks and Caicos Islands should be monitoring the progression of the NHC Disturbance 2 over the coming days. For the U.S. Southeast? It’s too soon to say much about this. Folks in Florida up through the Carolinas should continue to monitor but understand that there is a very high amount of uncertainty with this wave. Confidence in Disturbance 1 is a bit higher both in track and in details right now. Confidence in this Disturbance 2 would be classified as low to lower than average. More to come.