The Eyewall

One-sentence summary

Invest 95L is very close to becoming our next tropical depression or storm, and it is expected to rapidly intensify this week passing just north of the Caribbean islands and worth keeping an eye on in Bermuda.

Invest 95L

Invest 95L is close to becoming a depression or tropical storm this morning. It’s got plenty of thunderstorm activity associated with it, and it’s beginning to show a little “twist” now on satellite loops. I would expect Tropical Storm Lee to form before day’s end.

We expect this system to go off to the races over the next few days. Thankfully, that should allow it to gain the latitude needed to bypass the islands to the north. Because I have to tell you, the intensity forecast for 95L is one of the most impressive I have ever seen for an Atlantic tropical system.

For those that are astute watchers of hurricane models, you’ll know the HWRF model tends to bias to the high side with intensity, and we’ve seen some wild forecasts over the years from that one. But seeing essentially all the tropical models close to or all aboard the Cat 4 train with this one from pre-inception has been something to witness. Expect to see quite a show in the Atlantic this week.

Assuming we have the next 72 to 96 hours mostly baked in, the biggest concern now is what will happen once this thing turns. Will it split the gap between the Carolinas and Bermuda and hook back out to sea? Will it turn sooner than that and actually go east of Bermuda? Or will Bermuda be in the way? The quick intensity gain expected this week is great for the Caribbean, but it may be precarious for Bermuda. As the system grows and rounds the periphery of the ridge, it will also probably erode the western flank enough to turn from northwest to north fairly quickly. You can see hints of that on the map above. From there it becomes a game of exactly where that happens and how much space it has to erode the northwest periphery of the ridge to turn northeast and ideally away from Bermuda. It will be close. Hurricane Sam in 2021 may be a decent analog to this one.

Either way, at this point, if you’re in Puerto Rico or the Virgin Islands, keep tabs on this to make sure it does what is expected. If you’re in Bermuda, watch closely later this week to see how it trends. If you’re on the U.S. Eastern Seaboard, another round of rough surf and rip currents may be on the menu next week.

Elsewhere

Things look mostly uneventful in terms of land impacts over the next 7 to 10 days. We have another wave emerging off Africa today that has a chance to develop over the next 5 or 6 days way out in the eastern Atlantic.

The remnants of Hurricane Franklin are back on the map today, as it circles back south to a spot in between the Azores and Portugal. Significant development seems unlikely, but whatever is left of this could end up near Iberia later in the week or next week.

Otherwise, that’s about all. The Gulf and Caribbean look quiet for the foreseeable future.

Later this morning, we’ll have a post looking at how we stand as we arrive at the peak week of hurricane season. How have seasonal forecasts done so far? And what do we expect from the rest of the season? Look for that around 11 AM ET/10 AM CT.

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.

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.

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.

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.

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.

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:

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.

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.