I mentioned something below about “eyewall replacement cycles,” and I wanted to attempt an explanation of what I’m talking about. First, take a look at the infrared satellite images below of Hurricane Frances, which were taken today at 4:15 PM EDT and 9:45 PM EDT, respectively:
First, a basic orientation: the darker-colored cloud tops are colder, which means they’re higher in the atmosphere, which means the thunderstorms there are more intense. The colors, of course, are artificially added to make the contrasts easier to see. The eye itself is an area of cloudless calm; the surrounding eyewall is the region where the strongest winds and the most intense rains occur.
Now then, you’ll notice that in the second (later) image, the eye is substantially larger than it was in the first image. Normally, if a hurricane’s eye is getting bigger, that means it’s weakening; the pressure is rising, and the storm become less “tightly wrapped.” (Occasionally, intense hurricanes have huge eyes, but as a rule, a small eye indicates a strong storm.)
In this case, however, what we’re seeing is not a sudden weakening, but an eyewall replacement cycle — quite common in Category 3, 4 and 5 hurricanes — wherein the “inner eyewall” basically collapses in on itself, briefly producing the extremely tiny eye of the first image, which then falls apart and is replaced by the larger eye of the second image (previously the “outer eyewall”; you can actually see a hint of it in the lighter-colored cloud tops north of the eye in the first image).
Eyewall replacement cycles can produce temporary weakening, though the extent to which that occurs varies from storm to storm; in this storm, it seems to have been rather mild so far. Sometimes a temporary eyewall-replacement-triggered weakening trend can become more permanent, especially if it occurs concurrently with other unfavorable conditions (e.g., if dry air is sucked into the storm’s inner core). This is one reason why forecasters have so much trouble predicting the intensity of storms like these even a few hours into the future, let alone days.
On the other hand, once a replacement cycle is completed and the new eye and eyewall are fully formed, an intensification phase — sometimes a rapid one — can occur. A storm such as Frances can potentially replace its eyewall, drop its central pressure, and gain 20 mph in wind speed within a few hours. I’ve seen it happen before. (Remember how Charley strengthened from a Category 2 to a Category 4 in a matter of hours with no warning at all? I’m not sure if that’s what happened — I was on a desert island at the time, not watching TV or the Internet — but I’m guessing probably so.)
But again, whether such intensification occurs after an eyewall replacement cycle varies from storm to storm, and from cycle to cycle.
Mind you, I’m a layman, not a meteorologist, so I may be wrong on some of the details here. But this is my understanding, based on what I’m picked up from watching many, many Tropical Updates on The Weather Channel over the years. :)
I know this for sure: the processes that govern both eyewall replacement cycles and rapid intensification phases are very poorly understood by meteorologists, and so are almost impossible to predict. Monster storms like this really create their own environments, and are unlike any other weather phenomena we encounter on Earth. They’re remarkable, beautiful, awe-inspiring — and terrifying, if you’re in their path.
Say a prayer tonight for the people of the Bahamas and the southeastern United States, especially Florida.
The new advisory is out:
At 11 PM EDT…0300z…a Hurricane Watch has been issued for the Florida East Coast from Florida City northward to Flagler Beach…including Lake Okeechobee. Some or all of the Hurricane Watch area will likely be upgraded to a Hurricane Warning Thursday morning. A Hurricane Watch means that hurricane conditions are possible within the watch area…generally within 36 hours.
At 11 PM EDT…a Tropical Storm Watch has been issued for the middle and upper Florida Keys from south of Florida City southward to the Seven Mile Bridge…including Florida Bay.
Here’s a graphical illustration:
It’s still at 140 mph, and according to the discussion, that estimated strength “may be a little conservative.” Also:
Frances is expected to move over warmer water near and within the Bahama Islands chain in 24-48 hours. Given the already impressive outflow pattern…some additional strengthening seems plausible. Also…the very dry mid-level air…30-40 percent humidity…that Frances has been traversing through and ingesting over the past 5 days is forecast to increase to more than 60 percent in 36-60hr… which may also help with the intensification process.
Intensity forecasts for major hurricanes are notoriously unreliable, because the changes in strength are largely governed by internal “eyewall replacement cycles” which are still very poorly understood by scientists. Thus, the hurricane center generally shies away from making bold predictions about intensity in either direction once a hurricane reaches this level of strength, and instead just predicts “fluctuations in intensity.” That’s exactly what they’re doing now. But it sounds like, in their heart of hearts, the NHC forecasters expect Frances to get stronger before landfall.
If it reaches 156 mph, it would be the first Category Five hurricane to hit the U.S. since Andrew, and only the fourth ever.
“Hellstorm,” indeed.
P.S. Jeb Bush has declared a state of emergency for the the entire state of Florida, and nearly a half-million people have already been ordered to evacuate. The Kennedy Space Center is closing down.
According to the AP: “The last time two major hurricanes hit Florida in rapid succession was 1950. Hurricane Easy struck Tampa around Sept. 4 of that year and Hurricane King hit Miami six weeks later on Oct. 17. They were Category 3 storms, smaller than Charley or Frances.”
Here’s what the computer models are saying. Here’s another look. The NHC is expecting some very valuable data out of its next “model run” later tonight, and the forecast may be significantly updated — quite possibly to the “left,” or south, of the current track — when the 5:00 AM advisory comes out.
P.P.S. See above for evidence that Matt Drudge’s head has exploded (again).
More on eyewall replacement cycles further above.
I have an orientation session at 4:00 PM, so really, what’s the point of continuing to try to read CrimLaw now? I’ll buckle down after 5:00, I swear it. :) In the mean time, some Wonkette posts from the Republican National Convention for you:
Naked protesters (possibly NSFW)
Giant-penis hats (SFW, not safe for elephants)
Cringe-inducing Bush daughters
And last but not least, the RNC’s elusive black people!
Not fair, but funny. And entirely on par with Wonkette’s usual standards. :)
UPDATE: Speaking of questionable fashion, here’s an image of the graphic on the t-shirt BoiFromTroy will be wearing tonight during Cheney’s speech:
P.S. Yes, I do now have an image file in my blog/images directory called “boifromtroy-dick.jpg.” And yes, I’m okay with that. :)
P.P.S. Incidentally, Boi, who is in New York, loved Schwarzenegger’s speech last night. He watched it from a bar where there was a Log Cabin Republican event:
The hot item of the night was the “I’m with Arnold” t-shirt, which in the gay bar, received a 80% nonplussed / 15% ‘fantastic!’ / 5% “how can you be gay and republican you spawn of satan” response.
I’m guessing the “I love Dick” shirt would go over a little better, if possibly for the wrong reasons. :)
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Categories: Election 2004
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Thanks be to Photoshop, the techie blog Gizmodo has posted a safe-for-work version of Playboy’s photo of a naked Washingtonienne using an iBook, the same photos that caused me to proclaim yesterday without elaboration, “She’s a Mac user!!”
Gizmodo asks the question that’s on everyone’s mind upon viewing the photo: “Do they have a special iBook with the Apple Logo removed, or are their photoshop people just that good?”
Well, it question was on my mind, anyway. :)
Less raunchy, but with the Apple logos intact:
:)
Okay, back to work, again. Man, I just opened up my computer to check the time, and I ended up online for 20 minutes… dammit…
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Categories: Technology & Nerdy News
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The latest National Hurricane Center discussion on Category 4 Hurricane Frances suggests that Hurricane Watches will definitely be up in advance of Bush’s acceptance speech tomorrow night. In fact, they may be posted around the time Cheney is speaking tonight:
The official forecast brings the core of the hurricane near the Florida East Coast within 3 days. However…the hurricane is expected to have a large area of tropical storm force winds which are forecast to approach the coast much earlier. This may require a Hurricane Watch for portions of the Florida East Coast this evening or early Thursday.
Bush is definitely going to be competing with Frances for news-cycle primacy tomorrow and Friday. Frances will dominate the weekend. I wonder how this will affect the convention bounce?
In other news, forget the Saffir-Simpson scale; Matt Drudge has come up with a new designation for Frances: “Hellstorm.”
Incidentally, if the current forecast track holds, the storm surge and wind damage could be very severe at Cape Canaveral. As if NASA needed any more problems.
UPDATE: The Florida delegation at the RNC is, understandably, worried about Frances. “Saturday is D-Day,” one said.
If it hits Florida at its current strength, scarcely three weeks after Charley, “it would be the worst double hurricane strike on one state in at least a century,” according to the AP.
