Matt Lanza

September 4, 2023 Outlook: Invest 95L should soon develop and hopefully thread the needle north of the Caribbean islands

One-sentence summary

Invest 95L is expected to become a depression or tropical storm soon as it comes west across the Atlantic, likely passing just north of the Caribbean islands, though it merits some continued watching.

Invest 95L

On satellite, Invest 95L is beginning to slowly get itself together. It has thunderstorms that have persisted, indicated by the brighter colors on the satellite loop shown here. It’s got a little swirl to it, but probably not quite enough to indicate a surface low is present.

Invest 95L is slowly beginning to get its act together. (Tropical Tidbits)

But it’s getting there, and that’s the takeaway today. The National Hurricane Center has boosted odds of development to 90 percent over the next several days. And this seems to be in line with almost all model guidance that shows this developing.

Invest 95L’s track

The track and intensity forecasts are somewhat intertwined. As is often the case, a stronger storm will be more apt to get steered poleward, or toward a recurve north. A weaker storm won’t get as much latitude. So the speed at which 95L organizes is somewhat important. Given that it is already starting to establish some structure, my thoughts today lean toward the stronger outcome and a faster recurve. That said, this remains a very close call in the islands.

Models have actually been in very good agreement through about day 4, which gets 95L some decent latitude. By day 5 (shown on the Euro ensemble mean below), 95L should already be near the same latitude as Puerto Rico. As long as that occurs, it should miss the islands to the north.

Invest 95L will be steered around a somewhat convoluted high pressure system in the central Atlantic. As long as 95L strengthens steadily this week and gradually builds latitude, it should curve out to sea north of the islands this coming weekend. (Tropical Tidbits)

So we believe that 95L will stay north of the islands, but it will be close. Of the many model ensemble members from the GFS, Euro, and Canadian models, about 90 to 95 percent or so stay north of the islands.

The majority of the model ensembles we look at for forecast keep 95L north of the islands this coming weekend. (Tomer Burg)

So the odds are generally good for minimal land impacts as 95L comes west. This is good, as the majority of model guidance shows this becoming a major hurricane in about 4 days. But still, you don’t rest entirely with 5 to 10 percent bringing it much closer. We’ll keep watching.

Beyond the islands

Once 95L (or likely Lee by that time) gets north of the islands, where it goes is a bit of an open question. Will it truly recurve north and threaten Bermuda or turn out to sea? Will it turn north but then turn back more west-northwest and threaten the Bahamas or the U.S. coast? How will the cooler water recently upwelled from Franklin and Idalia impact it if it comes north? It’s too early to say anything with confidence here, so we’ll leave it at that for now. Stuff for us to watch this week.

Elsewhere

We may see another system attempt to develop and basically follow in Katia’s footsteps way out at sea in the open eastern Atlantic. But aside from that and 95L, truthfully things look quiet, a potentially decent outcome for mid-September in the Atlantic.

September 3, 2023 Outlook: Invest 95L is a system to keep an eye on this week in the Atlantic as it moves toward the Caribbean

One-sentence summary

As Gert and Katia fade away, the Atlantic will be left with one primary feature, Invest 95L, whose progress should be monitored closely this week in the Lesser Antilles and Puerto Rico.

Happening Now: Gert & Katia

The Atlantic map is now down to two named storms and one invest that may develop in the next few days.

Gert and Katia are the only two active systems in the Atlantic. Idalia’s remnants should not regenerate. The next system, Invest 95L may develop early this week. (College of DuPage)

Idalia is no longer expected to regenerate into a tropical storm, however it is a fairly potent extratropical system. Rip currents remain high on East Coast beaches for the holiday weekend into tomorrow, so swimming caution is advised.

Tropical Storm Gert is expected to finally be absorbed into Idalia’s remnant circulation tomorrow, finally ending its run. Well off to the east, in the middle of the eastern Atlantic, Tropical Storm Katia formed this weekend. It is expected to fizzle out basically in place over the next 2 to 4 days.

Invest 95L: A system to watch

While Invest 95L is not much to look at right now, other than a blob of cloudiness, modeling continues to suggest it will come west and west-northwest and gradually develop into a formal tropical entity this week. The challenge right now is trying to predict when and at what latitude that will happen, because that may have critical implications on the Leeward Islands, Virgin Islands, and Puerto Rico in time.

We can look at lots of modeling right now for track potential from Invest 95L, and we’ll get a map that looks, broadly, like the one here:

The current European ensemble forecast for Invest 95L calls for a strong storm that has decent odds to go *just* north of the Caribbean islands. (Weathernerds.org)

This shows about 90-95% of European ensemble members missing the islands to the north with a stronger system. Remember, the ensemble takes a model and runs it many times (in this case 51) to produce a “spread” of possible outcomes, giving us a more realistic picture of what may happen down the line.

Importantly, this track goes north in most cases because of a weaker ridge of high pressure over the Atlantic and a rapidly intensifying storm that would curve “into” the high as it erodes the southwest periphery.

The strength and orientation of high pressure to the north of 95L will be critical in determining where exactly it tracks going forward. (Tropical Tidbits)

But here is the rub. If that high pressure area comes in stronger than forecast or a little more southwest of forecast, the exit door out to sea may (initially) be blocked or may not be as robust as it looks above. Or it could force the system to temporarily track more south of west for a short time. In that case, 95L would continue tracking much closer to the islands and a potential impact. In my own opinion, this setup is very, very precarious and needs to be watched closely because the models are generally in good agreement on the idea that this could become a relatively strong system. So interests in the Caribbean should be watching this very closely.

Assuming it does eventually recurve, interests in Bermuda may need to watch this one as well. We will keep you posted.

Elsewhere

Modeling has really, really quieted down elsewhere. The western Caribbean and Gulf look very quiet over the next 7 to 10 days with nothing really showing up even in fringe ensemble cases. We may see yet another Katia-type system in the Atlantic later this week, but that is TBD. Either way, it’s not looking like a land impact system.

Basically, the only item to watch (closely) is Invest 95L and its progress this week.

September 1, 2023 Outlook: Idalia wanders to Bermuda, while we play whac-a-mole in the rest of the Atlantic

One-sentence summary

Idalia is expected to become a tropical storm again as it approaches Bermuda, while multiple other systems out there are of no land concern at the moment.

Post-tropical Idalia

Idalia is in a post-tropical phase currently, meaning it’s no longer a “warm core” system feeding off of warm water. Basically, Idalia is an “extratropical cyclone” without thunderstorms and with fronts, akin to a broad nor’easter off the East Coast.

Idalia has been reduced to a broad swirl of clouds without thunderstorms. It will bring periods of rain and gusty to Bermuda over the next few days. (Weathernerds.org)

Over the next couple days, Idalia will wander toward Bermuda, eventually probably feeding off the warmer water near the island, which could (should?) allow it to regain tropical characteristics and become a tropical storm again. As Idalia does this, there could be periods of heavy rain and gusty winds on Bermuda. Tropical Storm watches are posted for the island. This is probably not going to be a damaging storm there, but frankly if you have a trip planned to Bermuda over the next few days, I have to apologize.

Idalia is slowing down and drifting southeast. It will pick up the pace next week as it passes Bermuda. (NOAA NHC)

One other note on Idalia: Because it has grown quite large in size, it will likely continue to churn up rough seas off the U.S. East Coast. This will probably keep rip current risk high for the holiday weekend, so if you are beaching it there this weekend, please use caution in the water. Rip currents can be very dangerous.

Lastly, what does Idalia do beyond Bermuda? Yes. That’s the answer. Yes.

In all seriousness, there is a huge disparity in model guidance regarding Idalia’s track forecast after about day 4 (Monday/Tuesday).

Idalia’s track forecast after day 4 or so is highly uncertain, with a convoluted steering pattern in the Atlantic, but Idalia should remain generally a weak to moderate tropical storm. (Weathernerds.org)

Once Idalia passes Bermuda it will be subject to the whims of building high pressure in the central Atlantic and whatever steering flow is present in the northwest Atlantic. Because there is a lot of action in the Atlantic right now, it makes the pattern forecast into next week a little challenging to decipher with specificity. We’ll call it convoluted. Could Idalia turn left and head to New England? Certainly. Could it head out to sea? Certainly. Could it just meander and eventually fall apart? Certainly. Anyone speaking with confidence on this right now is not serious. We’ll watch it through the weekend and see how this evolves. We’ll keep you posted this weekend as well.

Franklin and Jose and Gert and 94L

Franklin, Jose, and Gert need to learn a thing or two about personal space. Because right now, they’re not really giving any of that to each other.

Hurricane Franklin, Tropical Storm Jose, and newly reformed Tropical Depression Gert are crowded together east of Bermuda. (Weathernerds.org)

Remember Tropical Storm Gert? Of course you don’t. It formed a couple weekends ago, then dissipated, and managed to fester long enough to regenerate this morning back to Tropical Depression Gert. It’s just southwest of Tropical Storm Jose, which is just southeast of Hurricane Franklin. Neither of these is a threat to land. All of these will have some impact on the broader pattern in the Atlantic. Alas.

Meanwhile, east of all this, occupying its own personal space is Invest 94L, which should become Tropical Storm Katia today or tomorrow. It is also of no threat to land.

Next week’s next wave

Lastly, we continue to have visibility in modeling on the next tropical wave which may develop by mid to late next week in the central Atlantic. Given the potential location of this wave, it probably is worth keeping tabs on in the islands for next weekend or late next week.

The next tropical wave will be an issue to watch for the islands by next weekend. Too much uncertainty exists right now to say anything with confidence. (Weathernerds.org)

Modeling seems to be in good agreement on this area developing and potentially getting close to the islands by next weekend or so. Its track will ultimately be determined by exact placement of features in the Atlantic and how strong the system itself can get. These are questions we can’t answer right now. We’ll watch it through the weekend and update with more once we get some clarity.

August 31, 2023 Outlook: Idalia off to Bermuda, Franklin out to sea, but what else is out there?

One-sentence summary

A much less intense Idalia should move toward Bermuda heading into this weekend, but there is a bit of uncertainty about what happens next week, while a couple other systems meander out to sea elsewhere.

Tropical Storm Idalia: 60 mph, moving ENE 21 mph

Idalia is moving off the coast of the Carolinas now, as it begins its march toward Bermuda.

Idalia’s track will take it east and then probably eventually southeast, nearing Bermuda by later in the weekend. (NOAA NHC)

Heavy rain continues from Idalia over far east North Carolina, with some flash flood warnings posted for the Outer Banks this morning. Some locally hefty rainfall amounts are occurring in that area. Wind gusts generally in the 40 to 50 mph range with a couple exceptions have also been occurring. A tropical storm impact in this region for sure.

Heavy rain continues over the Outer Banks, where flash flood warnings are posted. (RadarScope)

Idalia will continue eastward today and tomorrow with gradually improving weather over the Carolinas.

As Idalia heads out to sea it should hold its own or weaken a bit further, encountering a lot of wind shear. Because of Idalia’s size, tropical storm conditions or breezy rainfall could begin in Bermuda as early as later tomorrow or Saturday.

Through day 5, the forecast for Idalia is pretty straightforward. It will slow down as it approaches Bermuda and meander for a couple days, so by Monday it’s somewhere near or north of Bermuda.

From there, things get weird. On the map below I plotted the 500 mb pattern, or what would steer Idalia at about 20,000 feet up. Areas highlighted in red indicate warmer than normal, or what we’d refer to as “above normal heights.” Areas highlighted in blue are below normal. The yellow is an overlay I did of “spin” in the mid-levels of the atmosphere to identify Idalia relative to the 500 mb pattern. Confusing? A little, but it paints a picture I can use as a meteorologist.

As high pressure expands over the eastern Atlantic and without any real catalyst to “pick up” Idalia, the path may begin to get weird. (Tropical Tidbits)

The lack of blue color means there is a lack of lower heights or troughs that could pick up and move Idalia. Instead, Idalia on Monday night is stuck between a rock (high pressure over the Eastern U.S.) and a hard place (building high pressure from near the Cabo Verde Islands). This should produce erratic, uncertain movement early next week. And it’s plausible that Idalia has a lack of an exit, so whatever is left of it at this point would just sit and spin. This isn’t spectacular news as this could lead to an extended period of rough surf and rip tides on the East Coast that began this week and may extend into next week.

It also does open the door up for weird things like a track back toward the coast, except in the Northeast, not Florida. A couple things to note here: Idalia may or may not be a tropical system at this point. It surely should not be a strong tropical system if it is, but it may be a broad one size-wise, which means it would be capable of rough surf or offshore gale conditions. I think once we see how Hurricane Franklin’s exit goes, we’ll have higher confidence in the early next week period, hopefully in a day or two. But in general, we have a long way to go here, so we’ll keep an eye on things. Idalia should impact Bermuda in some fashion beginning by this weekend.

A busy Atlantic tropics continues, with 3 named storms, and a 4th area that may develop. (College of DuPage)

Elsewhere

Hurricane Franklin: 100 mph, moving ENE 15 mph

Franklin remains a category 2 hurricane, but it is beginning the process of accelerating out to sea.

Hurricane Franklin will pick up the pace out to sea over the next 2 to 3 days. (NOAA NHC)

No other impacts to land are expected as Franklin heads out.

Tropical Storm Jose: 40 mph, moving N 5 mph

As all the chaos broke with Idalia, Tropical Depression 11 formed out in the middle of the Atlantic this week. Overnight, that became Tropical Storm Jose. This will be a short-lived storm, and there’s no way Jose will impact land.

Invest 94L

Far out in the eastern Atlantic, we have Invest 94L , which is currently over the Cabo Verde Islands. This has about a 70 percent chance of becoming a tropical system over the next few days. But it will be heading northwest or due north away from any land impacts.

Invest 94L may become a lower-end tropical system in the coming days as it moves northwest in the open Atlantic. The next name on the list is Katia. (Tropical Tidbits)

Looking ahead

Other than monitoring Idalia, it will be a relatively quiet weekend into early next week. There are some signals of another Cabo Verde type system that could get going later next week or next weekend, but that’s far out there, and given the high uncertainty in the northern half of the Atlantic, I don’t really want to speculate on what might happen with that one.

That’s about it at the moment. We have a couple days to catch our breath and focus on hopefully lower-end impacts of Idalia in Bermuda. We’ll then see what happens next week and keep tabs on the next system emerging off Africa later next week.