The Eyewall

One-sentence summary

Hurricane Lee is intensifying east of the Caribbean Islands, and it will likely become a category 4 or 5 storm this weekend before tracking northeast of the Bahamas and slowing down some, increasing uncertainty as to where it will ultimately track next week.

Hurricane Lee: 80 mph, moving WNW 13 mph

What’s changed since Wednesday?

Lee is now a hurricane and likely beginning its rapid intensification process. The forecast track remains highly uncertain beyond the weekend.

Lee’s intensity outlook

Hurricane Lee should be in an environment conducive to steady, if not rapid intensification over the next couple days. We’re likely to see this become a category 4, if not a category 5 storm. Once it gets there, it will hold, with some fluctuations for a few days. Storms that achieve category 5 intensity usually do not stay there for more than a day or so, as the storm becomes vulnerable to eyewall replacement cycles which weaken winds but expand the radius of strong winds. Other factors like shear and forward speed can impact storms more when they reach top-end intensity. It is going to remain a powerful hurricane for awhile, but its peak intensity may be (relatively) brief.

Once Lee comes farther west and begins to turn more northward, it will likely encounter more unstable water temperatures as well. It could be dealing with remnant cooler water churned up by Hurricanes Franklin and Idalia. It may also slow down for a time to a point where it churns up cooler water itself that could lead to some “self-destructive behavior” (insert your own jokes here). Just to be clear, I’m not trying to downplay it, quite the contrary. Folks should know that you are going to observe these fluctuations in intensity, and that is absolutely normal, expected behavior for powerful hurricanes that should not lead to dismissing it as a “bust” or to qualify it as “weaker.” Despite lower top-end wind speed, the storm will probably grow in physical size some as it figures out where it’s going next week.

Lee’s track

I really can’t emphasize enough that there are so many factors that will dictate Lee’s ultimate track. Each one of these factors will matter daily next week. Imagine trying to forecast for five completely disparate locations 6 to 7 days in advance and nailing every aspect of that forecast perfectly. You probably can’t. I’ve done this for almost 20 years now, and I know I can’t. Because to unlock the key to Lee’s end game, you have to basically do just that.

So the map above shows you what’s happening around 20,000 feet up on Monday night. Lee at this point is north of the Caribbean islands and east of the Turks and Caicos Islands. High pressure to the north of Lee should weaken enough to allow Lee to barge through and start coming northwest or north. Additionally, Invest 96L may play some role (the “L” on the map above) in determining the orientation of things to the east of Lee. One of the big issues will be exactly what things look like when that turn happens. Where does that happen and when does that happen, and what will the trough (blue area) over the Great Lakes look like when that occurs. Because ultimately, that trough is going to have a say in Lee’s trajectory, and that could determine if Lee tracks close enough to the East Coast to cause impacts. Additionally, high pressure over Atlantic Canada (which has strengthened some in forecasts since yesterday) may also play a key role. In other words, we’re still at a loss as to Lee’s future simply because there are too many players out there trying to influence Lee’s movement and trying to precisely place them 5 to 7 days out is difficult. That placement matters a lot.

So, folks on the East Coast should continue to monitor Lee. Bermuda and the Canadian Maritime provinces should continue to monitor Lee. And, yes, the Turks and Caicos and Bahamas should as well. This is a tricky, delicately balanced situation and hopefully some consensus will emerge in the coming days.

Elsewhere

As noted above, Invest 96L is still out there and going to make a go for development into the weekend. It will not threaten land, but it will be part of Lee’s answer key. The next name on the list is Margot. Besides that, I don’t see much else over the next week or so of note.

Pacific Hurricane Jova

Quick note because I have a minute. Here is Hurricane Jova.

Jova is a beastly storm thankfully in the open waters of the East Pacific. It will not threaten the U.S. or Mexico. But I point it out because it has 160 mph winds and is a category 5 storm after rapidly, furiously intensifying. Storms this large can influence some things around it, so there’s probably some inherent forecast uncertainty to the west of Lee thanks in part to this storm. Aside from that, category five storms are a heck of a thing to observe in real-time. Glad it’s over the open ocean.

One-sentence summary

While Tropical Storm Lee’s ultimate future is unknown, it is likely to become a hurricane today, and it is still forecast to miss to the north of the islands with some modest fringe impacts there.

Tropical Storm Lee: 65 mph, moving WNW 14 mph

What’s changed since yesterday?

Invest 95L became Tropical Depression 13 briefly, and then it became Tropical Storm Lee yesterday afternoon. It is organizing and tracking west-northwest. Confidence that it will miss a direct impact on the islands is increasing. Confidence on anything beyond there is low.

Lee’s intensity

Lee is in a tremendously ideal environment for intensification. It has deep warm water, low shear, and plenty of moist air in the neighborhood for the next 5 or 6 days. Models have suggested since last week that this would go to the moon intensity-wise, and there’s no reason to doubt that today. The NHC forecast for Lee was one of its most aggressive on record, taking it to a category 4 storm by Sunday or Monday, something they will not commit to without confidence.

Once Lee manages category 4 or 5 intensity by Friday or Saturday, it will likely fluctuate in intensity up and down for a few days, probably remaining a major, if not Cat 4-5 storm much of the time. Heading into next week, the question will become where Lee tracks relative to the cold wake in the Atlantic from upwelled water left behind by Hurricanes Franklin and Idalia.

So, for now, expect a pretty impressive hurricane into early next week, followed up by some potential significant fluctuations in intensity as it comes northwest.

So where is Lee headed?

We have about 5 hurdles with respect to Lee’s track over the next 10 days or so. First, Puerto Rico and the Leeward Islands. Second, the Turks and Caicos and southeast Bahamas. Third, Bermuda. Fourth, the US coast, and lastly the Canadian Maritimes.

First, with respect to Puerto Rico and the islands, Lee is expected to pass to the north, comfortably enough to avoid significant impacts but definitely close enough to keep watch and expect fringe impacts (a few outer bands with gusty winds, rough surf, rip currents, etc.). So if you’re in Puerto Rico or the Virgin Islands, stay tuned and keep watch, but you are almost at the point of being able to exhale.

Beyond that, it remains to be seen what happens. Lee will be steered around the periphery of high pressure over the Atlantic. This should ensure it gets to a point northeast of the Bahamas early next week. From there, the players on the field become more difficult to assess. How strong is the high? Does it collapse, weakening steering currents? If it doesn’t collapse, where is it centered? Will the trough over the Great Lakes be strong enough to try to “capture” Lee and draw it more toward the East Coast? If Lee splits the gap between Bermuda and the Carolinas, will New England or the Maritimes be in the way on its way out? Will Lee be strong enough to just barge north toward Bermuda anyway? How much of a role will the cooler water out there play in Lee’s intensity? The map below shows the situation on Sunday evening.

There will be some people out there speaking with conviction about the future of Lee, and if so, you can tune them right out. Every question I just rhetorically asked has no answer yet. None. I personally think Lee will split the gap between Bermuda and the Carolinas and then hook out to sea, but I see a path where the trough digging in from the Lakes could try to draw it back west, especially if it’s weakened some by the cooler water west of Bermuda. I see how it could hit Bermuda directly or pass very close. I see a path where it misses Bermuda and the US but runs into Atlantic Canada. What I don’t have is confidence in any of those outcomes right now. There are too many “known unknowns” for confidence. I realize this answer won’t generate a lot of excitement, but this is exactly why we’re here…to provide sober, steady analysis of significant storms. Welcome to The Eyewall!

Anyway, let’s keep tabs on this over the next few days, and we’ll monitor the progress of the features that will steer Lee in the future. One thing I can say with confidence? Expect more rough surf and rip currents on the East Coast next week.

Beyond Lee

We recycled into Invest 96L yesterday, which is a very robust tropical wave just off the coast of Africa. That has a decent chance to become either Tropical Depression 14 or Tropical Storm Margot in the coming days. It is unlikely to threaten land other than some initial heavy rainfall in the Cabo Verde Islands.

After we get past 96L, there is a minimal chance of additional development in the Atlantic next week. The Gulf looks closed off, as does the western Caribbean, loaded with shear. The overall background state of the basin should be hostile to tropical development into next week. We may flip back to a more lively pattern again in the final 10 days of the month. We’ll see!