Matt Lanza

Taking stock of the 2023 Atlantic hurricane season so far: Active with headwinds; more to come?

One-sentence summary

With the historical peak week of hurricane season upon us, we take a look at what has happened so far, how seasonal forecasts have performed, and what we can glean for the rest of hurricane season based on the active start and El Niño.

How are those seasonal forecasts holding up?

Back in June when we launched The Eyewall, one of the things we did was dive into the components of the seasonal forecast. We explained that the 2023 hurricane season would be trickier than normal, as the developing El Niño, which typically reduces storm activity would be battling an outrageously warm Atlantic Ocean, a feature that would be good for busy storm activity. So far, that battle seems to be exactly what’s playing out. The “consensus” forecast was 16 named storms, 7 hurricanes, and 3 majors. As of Monday, we sat at 12 named storms, 3 hurricanes, and 2 majors.

Our accumulated cyclone energy for the season, or ACE, sits around 125 percent of normal for the first week of September.

As of yesterday, the Atlantic was running about 125 percent of normal activity, from an ACE standpoint. (Colorado State University)

If the season ended right now, we would be sitting in the upper tier of “below normal” seasons. In other words, we already have one heck of a base and seem to be on our way to (at worst) an average season. The seasonal forecasts did a good job telegraphing this, and frankly some of the more active seasonal forecasts that I believed were more out of an abundance of caution are the ones most likely to verify.

And this isn’t because of ticky-tack storms that last a day or two. Idalia, Don, and Franklin, the three hurricanes account for nearly 75 percent of the seasonal ACE to date. So three legitimate storms make up the majority of the total. Back in June we said that we believed the Caribbean would struggle (it mostly has), the eastern Atlantic would be busy (it’s been more the central Atlantic, so that point is a little fuzzier), and that the most concerning items this season would be systems forming close to home (Idalia counts for that). So thus far, this is going mostly as expected, if not a little bit busier. Kudos to the seasonal forecasters for not just going all-in on El Niño.

Where are we going?

Well, this week we are likely to see another big jump in seasonal ACE when Lee forms.

The likely track of future Lee should go north of the islands but may impact Bermuda. It’s going to be a very strong storm. (Tomer Burg)

From our morning post, you can read how we expect that to become a major hurricane, likely at least a category 4 storm. This will be a big ACE adder, and I suspect we’ll see things shoot up at least into the 70s once Lee is done, pushing us into the “average” tier of seasons if it ended right there. Behind Lee, we may get another storm in the eastern Atlantic, so there’s an opportunity for a few more ACE units.

But here’s something. If you look at the European ensemble model forecast for wind shear in days 11 to 15, which pushes us out to near September 20th now, you can see that the Gulf and western Atlantic are ripping with shear.

Wind shear is forecast to remain well above normal in the Gulf and western Atlantic for mid-month. (Tropical Tidbits)

If that happens as forecast, anything in the Gulf will struggle, as would anything coming out of the Caribbean. However, the lower wind shear in the eastern Atlantic and central Atlantic suggests these would be the areas where storms could continue to form, continuing the legacy of the 2023 season to date. We may see less hostile conditions return to the Gulf and western Atlantic in the final days of September, but that’s obviously a long way off.

What does El Niño tell us?

Quite frankly, if we assume that El Niño is up and humming now and the influence is strengthening, then we should expect to see a lot of what we’ve already seen for the remainder of hurricane season. Here is a map of all hurricanes in Septembers and Octobers since 1950 when the Oceanic Niño Index (ONI) was 1.0 or greater for June-July-August (this year’s value is 1.1).

Hurricane seasons most similar to this one in terms of El Niño produced a lot of central Atlantic storms in September and October and not a lot of serious land impacts. (NOAA)

With a couple notable exceptions, this map shows a lot of fish storms and middling systems in the western Atlantic. The two most notable exceptions were Joaquin in 2015 which killed 34 people (33 of whom were aboard the El Faro). And also Betsy in 1965, which killed 81 and inundated New Orleans. Emily in 1987 hit Hispaniola and Bermuda. And I think that sums up the season so far: A lot of middling storms and mostly fish storms with one potent hit in Idalia.

All in all, given what we see on the maps right now and given how this season has gone, there are two primary areas that probably should watch for land impacts: Bermuda and the Greater Antilles. If we can relax shear enough late in the season and get a disturbance in the Caribbean that comes straight north, you never know what you can get out of that, and those often threaten Cuba, Jamaica, Hispaniola or the Bahamas. Bermuda remains in the target line I think for at least one or two more storms. Lastly, the eastern Gulf or off the Southeast coast may be secondary areas to watch, given the warm waters and potential for just the right things coming together at the wrong time, sort of like what we saw with Idalia and to a far less impactful extent, Harold in Texas earlier this season.

Will it be enough to drive ACE above normal for the season in the end? I’m not certain, but it will be close.

September 5, 2023 Outlook: Invest 95L should go off to the races and hopefully out to sea

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.

Invest 95L (center) should become Tropical Storm Lee later today. (Weathernerds.org)

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.

A majority of tropical modeling that’s tracked calls for 95L to eventually become a major hurricane, if not a category 4+ storm. (Tropical Tidbits)

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.

Invest 95L is expected to miss the islands to the north, but from there, where it goes relative to Bermuda is a difficult question to answer. (Tomer Burg)

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.

A lot of remnants in the Atlantic, but presently only 95L is of immediate concern. A system emerging off Africa will likely develop in the coming days and turn out to sea. (College of DuPage)

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.

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.