There are three systems to watch right now in the tropical Atlantic, the kind of activity you might expect in the middle of September. Closest to home, in the Caribbean, is Invest 92L, which continues its maddening oscillation between bursts of convection late in the day, making it look like a new cyclone is certainly forming, and complete convective collapses late in the day. It has been moving across ideal conditions for development ever since it entered the Caribbean, but is now running out of time, with the Yucatan looming up ahead, like a windshield in front of a struggling moth. And it's a good thing too, with the off-the-charts levels of heat content in the Caribbean right now; if that thing had established a surface circulation, we could have a monster on our hands in no time. We still could, but it's getting increasingly unlikely.
Furthest away, Tropical Storm Julia has joined the scene in the eastern Atlantic, and is forecast to slowly strengthen to a minimal hurricane and head straight northwest into the middle of nowhere, and eventually, it is to be expected, waste away in lonely isolation.
The big story, however, is of course Hurricane Igor, which is proudly taking its place among the Terrible I's of September: Isabel, Ivan, Ike, and now Igor. Hopefully Igor will not end, like those three, by plowing a path of destruction along the US coast, but it may take its place alongside them as an enormous ACE producer. (ACE, of course, is Accumulated Cyclone Energy--the measure of the aggregate energy generated by a hurricane over its lifetime.) Igor ballooned from a 80-mph Cat. 1 to a 150-mph Cat. 4 during the day Sunday, one of the most impressive bouts of rapid intensification I have ever seen, given that the 80 to 135 jump occurred in just nine hours. Since that time, Igor has been merrily defying predictions that he would ramp up to a Cat. 5, that an eyewall replacement cycle would begin, and that he would turn northwest.
Indeed, Igor seems to have found his comfort zone. There is an odd tendency I have noticed with many hurricanes that undergo rapid intensification: as soon as it's finished, they're done--they don't want to intensify anymore. It's as if they are saying, "All right, I've shown you my stuff, I ain't got nothin' else I need to prove, so I'm just resting on my laurels and staying just how I am." You would think that a storm, after finishing rapid intensification, might then go on intensifying slowly, or after pausing to catch its breath might ramp up aggressively some more, but nope. These storms seem to find the ceiling they've picked for themselves and then just sit there. We saw it with Danielle at 135 mph, with Earl at 145 mph, and now with Igor at 150 mph. There is no reason right now why Igor couldn't strengthen further, but he has stubbornly refused to all day.
These past three major storms should perhaps serve as a reminder of just what a rare and special thing a Category 5 hurricane really is. I think we all got just a bit jaded from 2003-07, when there were eight Category 5s, and four in one year (compared to just 19 in the 50 previous years). We started to think that any hurricane that got its act together and did rapid intensification would go to Cat. 5...we all thought it with Gustav and Ike in 2008, and on Jeff Masters's blog, I've seen everyone thinking it with Danielle, Earl, and Igor this year. We've forgotten that a hurricane can be one epic scary beautiful beast and still never be a Cat. 5. It's worth noting that if Igor had become a Cat. 5 before 11 AM today, it would've been the furthest east any storm ever did so (Cleo did at 49.8W in 1958). As it is, Igor was one of the furthest-east Cat. 4 storms ever, reaching that intensity at 46.1W (the furthest that I have found was 1995's Luis, at 43.6W).
Notably, however, Igor has not only refused to strengthen, but also to weaken. The NHC advisories have been predicting an eyewall replacement cycle to begin all day, but still there is no sign. The eye has remained the same size, the eyewall the same shape, everything pretty much unchanged all day. The result is that we have been treated to the rare and breathtaking display of a large and powerful hurricane at maximum intensity throughout an entire day's worth of visible satellite images. The result is also that we can expect, as mentioned above, Igor to rack up an enormous ACE. Danielle and Earl were not puny by any means--Danielle's ACE, I think, was around 22, Earl's around 27. Igor, though, is already up to 12.175 (more than half of that in the last 24 hours), and, if the NHC forecast verifies, it will be at 41.2825 five days from now, with several days of significant life left, most likely. It could easily be the tenth ever over-50 ACE storm, one of the all-time greats, along with hurricanes like Luis, Isabel, and Ivan. I should mention, though, that I don't expect the 150-mph intensity to last for much longer, as cloud tops have warmed distinctly in the past few hours, though the hurricane remains as beautifully symmetrical as ever.
Most importantly, however, Igor has stubbornly refused to turn northwest. For days now, the NHC has been predicting a northward turn, first around 40W, then around 45W, and then, adamantly and sharply, at 50W. And yet Igor has plowed on due westward, or even occasionally a bit south of west. The NHC has continued to call for an imminent northward turn, but has had to keep adjusting the forecast west to account for the initial position. The big test was whether it would pass 50W without showing any northward motion. Igor passed 50W just a few hours ago, and since that time has started to show just a wee bit of northward movement, though it's too soon to tell yet if that's a turn.
This is of course quite important because the further west, the more serious the threat to the US East Coast and Canada become, a threat that looked remote a couple of days ago, but is now looking like a real (though still relatively small) possibility. The greatest danger right now is for Bermuda, which is currently right in the bullseye of the forecast track to be hit about five and a half days from now by a storm that could rival Fabian. In any case, the East Coast can gear up for another round of powerful swells and rip currents.