9/7, 4:44 PM EDT: That’s the question Alan Sullivan is asking, as he watches the satellite loop and sees a distinct northerly component to Hurricane Ike’s motion over the last several hours. I see it, too.
It’s too early to say, however, whether this is a mere “trochoidal wobble” or an actual change in course. The consensus at the Eastern U.S. WX Forums is that it’s probably just a “wobble” — unsurprising, given that the storm is currently going through an eyewall replacement cycle. Likewise, Dr. Jeff Masters, commenting on his own blog, wrote at 3:09 PM EDT:
Yes, there has been some WNW motion the past hour, as pointed out. This is probably a wobble, and the storm will resume a W motion within the next two hours. The models are pretty firm that the WNW turn is not due yet. Still, every wobble north increases the chances of a Cat 3+ in the Florida Straits.
I suspect the 5pm NHC advisory will say something similar. The forecasters tend to be very conservative about wobbles, as they know from experience how often such events prove transitory.
On the other hand, Sullivan — who, remember, is (like me) not a meteorologist, just a weather buff with a strong layperson’s knowledge of hurricanes — thinks this “wobble” is the real deal:
Leaving the tip of Grand Inagua Island, the eye of Ike was heading straight west, but in the last couple of hours its course shows a shift to the right. This could be just a wobble, but on the larger-scale vapor-loop, I am seeing subtle changes in the steering pattern over the Atlantic, Caribbean, and Gulf — changes that also hint at a rightward shift. If this trend bears out in the next hours, it will increase the likelihood of a swipe at the lower Keys.
We shall see.
Even if this apparent course change is “just” a wobble, it could be significant nonetheless, as one poster on the Eastern WX forums pointed out: “Every WNW wobble that is not countered by a WSW wobble will shave [time from the storm’s passage] over Cuba . . . given the trajectory from which it will be moving and the anticipated turn. Every single wobble is potentially very significant.”
UPDATE, 5:24 PM EDT: It looks to me like the wobble is over, and Ike is moving due west again.
UPDATE, 6:21 PM EDT: Sullivan writes in comments, “Yes, but previously it was moving WSW. I still think we could be seeing a course change.” Meanwhile, on his blog, he posts an update:
I see the wobbles, but I think they overlie a course-change that has in fact begun. For that reason, let me propose a best case scenario. Everyone loves worst cases. There is still a chance that Ike won’t cause a major disaster. Imagine that the hurricane wobbles along the north coast of Cuba, but never quite drives ashore, and weakens as it interacts with land. Next, it passes a bit south of Key West, battering the town only moderately. Ike moves into the Gulf and scares the bejezus out of everyone, then encounters shear and dry air. Eventually it heads ashore in Texas at category one, and drops rain on droughty areas inland. Best case. And it could happen.
Sounds good, though to truly be “best case,” it would have avoid “scaring the bejezus” out of New Orleans, in particular, to the point of evacuation. If New Orleanians are forced to evacuate their city twice in two weeks, for two “false alarms,” I fear it will set back disaster preparedness in that city for a generation. Don’t get me wrong: another evacuation order would be necessary if the risk once again gets high enough. No doubt about that. But the fact remains, there are only so many times you can tell people to flee the next potential ”mother of all storms” before they stop listening — and twice is two weeks is too often. So, as I said earlier, I hope New Orleans gets not just a near-miss, but a far-miss.
After causing “huge,” “terrible” damage overnight in the Turks and Caicos Islands, Hurricane Ike is holding steady at 135 mph, with a pressure of 949 mb, and its eye is now parked directly over Great Inagua in the Bahamas:
“Rainbow” infrared satellite view at 11:45 AM EDT. Live loop here.
Ike is continuing west toward Cuba, where it is expected to make landfall tonight. The official forecast track has Ike traversing almost the entire island from east to west, which would greatly weaken the storm, but would also, in Alan Sullivan’s words, “cause massive devastation. Cuba is accustomed to hurricances, but rarely have I seen such an ominous looking onset. A large part of the country could be ravaged, including Havana.” Will Castro’s government again claim “no casualties,” as they rather implausibly did with Gustav, and again refuse international aid, a la the Burmese junta?
Ike could be somewhat less of a disaster for Cuba if it takes a slightly different course — for instance, “bouncing” off the coast and taking its WNW turn a little sooner than expected, tracing the north shore, which would keep the right-front quadrant over water — and this is entirely possible. Cuba is a long, narrow island, so a tiny “wobble” could have a huge impact. Such a lucky event for Cuba would be unlucky for the U.S., however, as it would keep Ike stronger as it approaches the Gulf of Mexico. As the National Hurricane Center’s 11am EDT discussion puts it:
ONCE INLAND…WEAKENING IS EXPECTED BUT THE DEGREE OF WEAKENING DEPENDS ON HOW LONG THE CENTER REMAINS INLAND. THE LATEST OFFICIAL FORECAST KEEPS IKE INLAND FOR APPROXIMATELY 36 HOURS SO SIGNIFICANT WEAKENING [TO A MINIMAL HURRICNAE] IS SHOWN. HOWEVER…ONLY A SMALL DEVIATION FROM THE FORECAST TRACK COULD RESULT IN THE CENTER OF IKE MOVING BACK OVER WATER SOONER.
Also, if Ike deviates a bit north of the current track (as opposed to south, which is also possible), Key West would be back in the bullseye. This could happen with little warning, which is why Sullivan continues to urge his fellow Floridians in the Keys to get the hell out:
I must remind residents of Key West that several models only brush the storm along the Cuban coast, retaining plenty of punch for the lower Keys. One outlier still brings Ike through the Florida Straits without Cuban landfall, and runs the storm directly over Key West. The scenario cannot be ruled out! If it occurs, Key West will be completely overwashed. I know you Conchs are a tough and prideful bunch, but what’s so great about dying like a damn fool because you didn’t take the Big One seriously? Leave today!
After Cuba (and perhaps the Keys) comes of Gulf of Mexico. Once Ike exits Cuba — whenever and wherever, exactly, that happens — and re-emerges over water, re-strengthening is expected. The Gulf of Mexico is still warm (in spite of moderate upwelling caused by Gustav), and, crucially, wind shear is expected to be low (though that, too, could change).
Moreover, the current forecast takes Ike directly over the Loop Current, which could fuel rapid re-intensification. And, as the Houston Chronicle’s Eric Berger explains, we can’t count on Gustav Redux in this regard:
[T]here’s a reasonable chance a storm coming off Cuba would pass over the Loop Current, allowing for significant and rapid re-intensification.
But wait, didn’t forecasters say that about Hurricane Gustav? Yes, the forecasters predicted that. What they didn’t foresee was slightly higher than anticipated shear as Gustav crossed Cuba, which caused the storm’s vortex — it’s central tower — to become off-centered.
This could also happen with Ike, but we just cannot know at this time. Wind shear isn’t forecast to be a significant impediment in three to five days time, but such forecasts aren’t wholly reliable.
There are other potential mitigating factors in the Gulf, too. As noted by the forecasters at the Houston/Galveston office of the National Weather Service, one is the potential to encounter dry air along the Gulf Coast like that which has kept our recent mornings most pleasant. An incursion of dry air could also disrupt Ike’s circulation.
All right, so Ike is headed for the Gulf of Mexico, with the potential to be a major hurricane — either because of less-than-forecast weakening over Cuba (due to a slight course variation) or because of rapid re-strengthening, or both. But where will it go? Isn’t that the million-dollar question.
Of course, we’re talking about a 5-7 day forecast, so it’s impossible to say with any precision. As the NHC discussion says, “IT IS MUCH TOO EARLY TO ANTICIPATE WHICH AREAS ALONG THE GULF COAST COULD BE IMPACTED BY THIS SYSTEM.” Anyone from Tampico to Tampa Bay could potentially be at risk. “From Corpus Christi to the Louisiana-Mississippi border remain the likeliest landfall locations,” according to Berger.
Extrapolating from the forecast track and the computer models, the current “bullseye” would appear to be somewhere between Houston/Galveston and the Texas/Louisiana border region. But that can, and probably will, change. (Case in point: just over 48 hours ago, Miami appeared to be in the bullseye; 24 hours ago, New Orleans did.) All anyone can really say at this point is, stay tuned.
Incidentally, Ike is now officially the only active storm left in the Atlantic basin. Josephine was downgraded to a remnant low yesterday, and the final advisory on Hanna — which proved, as expected, to be “little more than a windy rainstorm” for the East Coast — was issued at 5:00 this morning. Hanna’s extratropical remnant is now over Atlantic Canada, speeding northeastward. So Ike is now the only game in town. Moreover, Sullivan thinks Ike may be the last blockbuster storm of the season: “Fall is deepening prematurely. We will not see many more Cape Verde storms. Hanna’s remnant, caught in the polar jet, has rocketed all the way to Nova Scotia in the last few hours. Hurricane season has peaked. Once we’re done with Ike, things will be quieter.” We shall see.
P.S. In comments yesterday, a couple of questions:
Technical query: I often hear that warm waters power hurricanes. Does this mean that hurricanes cool the waters they pass over, so that another hurricane following too closely will typically be at a disadvantage?
and
I do not understand completely how a “lode of dry air” and a high pressure system affects a hurricane. Is this information available somewhere, hopefully in short form and non technical language.
I’ll start with the first question. Hurricanes do indeed tend to cool the waters they’re over, particularly if they move slowly or stall over those waters, due to “upwelling” — the winds dredge up cooler waters from beneath the surface. However, this has far less impact on areas, like the Loop Current, with a very high Tropical Cyclone Heat Potential, meaning the warm water is deep — in other words, there isn’t as much cool water under the surface to “upwell”!
With regard to Question #2: “dry air” is damaging to a tropical cyclone because these systems depend on moist air to power ther development. If a patch of dry air gets sucked into the circulation of a hurricane, it can cause significant short-term weakening. If a continuous stream of dry air is getting “entrained” into the storm’s core, the effect can be longer-lasting.
As for the high-pressure: in the post that spawned those comments, I had referenced an upper-level high pressure system that is steering Ike. (”Upper-level” meaning higher up in the atmosphere.) That is a key role of high-pressure systems vis a vis hurricanes: they tend to steer storms around their clockwise rotation, which generally means east to west in the Northern Hemisphere. (A “weakness” in the high can result in the storm moving more north. I like to think of high pressure as pushing hurricanes, whereas troughs of low pressure pull them.)
Another key role of upper-level high-pressure systems is in promoting a hurricane’s “outflow,” and thus helping to strengthen it. If an upper-level high-pressure system parks directly over the hurricane (which is itself a lower-level low-pressure system), this promotes healthy “outflow” of air from the hurricane into the surrounding environment, and leads to intensification. (By contrast, if an upper-level low-pressure system gets too close to a hurricane, it will cause “wind shear” and weaken the storm.)
A good source for reasonably non-technical explanations of lots of hurricane questions is the NOAA Hurricane FAQ.
“Rainbow” infrared satellite image at 8:15 PM EDT. Live loop here.
Hurricane Ike has regained Category 4 intensity this evening, with maximum sustained winds of 135 mph, and its long-term prognosis has changed dramatically: the monster storm now appears more likely to eventually hit Louisiana or Texas than to make landfall on the Florida peninsula, as once seemed likely. (The Florida Keys, however, remain at substantial risk, particularly Key West, and folks there should heed the evacuation order — Ike’s track is way too close for comfort.)
More imminently, Ike is about to slam into the Turks and Caicos Islands. Alan Sullivan writes: “There will be complete devastation on those low islands. This is certain. They will be in the north eyewall a few hours from now. It is too late for any wobble to spare them.” [UPDATE: In a 10pm update, Sullivan writes: “I shouldn’t make categorical statements. Ike’s course has wobbled back to WSW. Providenciales (i.e., the capital city of Turks and Caicos) may be just outside the eyewall.”]
Ike will then likely hit Great Inagua, the southernmost island in the Bahamas, with similarly terrible force tomorrow. After that, Ike’s predicted course takes it across Cuba, wreaking further devastation on an island already reeling from Gustav. Such a passage of Cuba would also substantially weaken the storm, but it could potentially restrengthen over the Gulf of Mexico. (On the other hand, as Sullivan writes in comments here, “Water temps are even lower than the were for Gustav, and another lode of dry air has come off the continent. IMO, Ike has no chance of coming ashore at full force in the northern Gulf.”)
That, again, is what the current forecast calls for. However, the computer model consensus has been shifting steadily to the “left,” or west, over the last two days, so who knows whether the current forecast will finally be the correct one? Maybe Ike will cross southeastern Cuba, re-emerge over the western Caribbean, and make a beeline for the Yucatan Peninsula. That would be the natural progression of the leftward model trend. We just don’t know at this point whether the models are finished “shifting.”
The shift in the computer model tracks is not just some random variation. Basically, the forecasts initially called for a “weakness” to develop in the upper-level high pressure system north of Ike, which would allow the storm to “turn right” and move northward, instead of chugging steadily west along the periphery of the high’s clockwise rotation. However, as Eric Berger explained at 8:58 PM EDT, “few of the models now forecast the hurricane to find a weakness in the high-pressure ridge.” This means “the system could follow a due west, or a west-northwest course, once it enters the Gulf.”
If Ike does indeed head west or west-northwest, that would be a relief to New Orleans. The current official forecast track, as of 5pm EDT (it’ll be replaced at 11pm with a new forecast), has Ike moving straight northwest, directly toward the Big Easy, raising the specter of a second evacuation in as many weeks. The Times-Picayunereported earlier today that FEMA’s chief of Louisiana operations, Bob Fenton, said of Ike, “Yesterday we were keeping one eye on it, but today we’re keeping two eyes on it.” That’s a good plan. Ike could move W or WNW, as Berger says, but it could also move NW, and that would put New Orleans in the bullseye.
Mind you, we’re talking about a potential threat that is perhaps a week away, so it’s certainly nothing imminent — no need for hype or panic. But here’s hoping the track shifts far enough away from New Orleans that hype and panic won’t become the norm in a few days. The last thing that city needs is yet another hurricane threatening its survival, even if it would end up being another near-miss. A far-miss would be much preferable.
Anyway, quoting Berger again, the Houston Chronicle weatherblogger notes that Ike’s leftward computer model shift “means that Texas is as likely a candidate for a final landfall as any other Gulf Coast state.” He adds:
If Ike follows the model consensus (and why should it start now?) it will spend a couple of days over Cuba, which should weaken the storm significantly.
The GFDL model, for example, sees Cuba’s terrain weaken Ike from a Category 4 hurricane to a Category 1 storm as it traces the spine of the narrow, mountainous island. The HWRF model is similar. . . . All of this potential interaction with land muddies the question of how strong Ike will become once over the Gulf of Mexico again, but I think it’s safe to assume some re-strengthening is likely.
It’s way too early to say where the hurricane might go once back in the Gulf, but tonight the odds of a Texas landfall are considerably higher than they were just a day ago. . . . The primary consolation for Texans is that the long-range model projections have been changing all week, and there’s no reason we shouldn’t expect them to continue to change.
As Berger also notes: “Amazingly, just 36 hours ago, we were talking about the likelihood of a Miami landfall.” Indeed — it’s been a remarkably swift change in Ike’s prognosis, and who knows how things will look in another 24 or 36 hours?
UPDATE: The official NHC forecast track has, as I expected, shifted slightly further left as of 11:00 PM EDT. This change simply reflects the above-described model shift. The five-day forecast is no longer “aimed” at New Orleans. However, that means very little, if anything, at this point. The entire Gulf Coast needs to watch Ike.
ONCE IKE MOVES OUT OF CUBA…AND MOVE[S] TO THE OPEN GULF OF MEXICO IT COULD REGAIN SOME OF THE FORMER INTENSITY AS INDICATED IN THE OFFICIAL FORECAST. IT [IS] INTERESTING TO NOTE THAT THE HWRF MAKES IKE AN INTENSE HURRICANE AGAIN…AND GLOBAL MODELS…PRIMARILY THE GFS…MAKE IKE A VERY LARGE HURRICANE IN THE GULF OF MEXICO. . . .
I HAVE CONFIDENCE IN THE TRACK FORECAST…BUT NOT CONFIDEN[CE] ENOUGH TO KNOW IF IKE WILL MOVE OVER CUBA OR OVER WATER SINCE CUBA IS LONG BUT NARROW. HOWEVER…I AM A LITTLE MORE CONFIDENT THAT IN FIVE DAYS…THERE WILL BE A LARGE HURRICANE IN THE CENTRAL GULF OF MEXICO.
There’s no question Hurricane Ike’s threat to South Florida is easing. The projected path continues to shift farther south, putting Cuba more at peril than this region. … [However,] [b]ecause it is a strong hurricane to our southeast (and because most of this area remains in that darn cone of uncertainty) – it would be wise to check the storm’s position occasionally through the weekend.
In the Florida Keys, meanwhile, it remains wise to not merely watch Ike, but to flee Ike, just in case. A slight “wobble” — or a “bounce” off Cuba — could still be disastrous for those ultra-vulnerable islands, and by the time such a thing would occur, it would be too late to evacuate. Better safe than sorry: get out now. Alan Sullivan writes:
The big question for tomorrow is whether Ike will hit the island or rebound to the right and stay just offshore. Each hour on its present [west-southwesterly] course diminishes the danger to my location in Dania Beach, Florida, just south of Fort Lauderdale; however, risk remains for the Keys, and especially for Key West. I must repeat my earlier admonition to citizens of the Conch Republic: take no chances with Ike. This is not some piddly tropical storm like Fay. If Ike misses Cuba, it will probably spin up to category three or four in the Florida Straits. You do not want to be in Key West during a category four hurricane! Your chances of survival would not be good.
Meanwhile, Hanna continues to dump rain on the Mid-Atlantic and Northeast. Here’s a live radar loop from the NWS:
9/6, 9:53 AM EDT: I wrote on Thursday that “Hanna is not worthy of much hype. It will bring rain and storminess to the East Coast, but will hardly be a disaster.” As it turns out, this was exactly right. Yesterday’s return to fully tropical status, and last-minute strengthening, was mostly just a meteorological curiosity; Hanna did not pack much of a punch, after all.
Even the “rain and storminess” was limited by Hanna’s very fast forward speed. This storm is zipping along, limiting is potential to dump flooding rains or batter those in its path with sustained strong winds over an extended period of time. The Wilmington Star-News reports little damage. Bob Owens, directly under the storm’s core, calls it “Much Ado About Nothing.”
Of course, as anybody reading this blog for the last several days has known, Hanna was never going to be the blockbuster storm of the Hanna-Ike-Josephine trio, and to the extent the media suggested otherwise, they were being irresponsible and inaccurate. (I barely ever watch cable news coverage of hurricanes anymore, so I can only assume they over-hyped Hanna — generally a fair assumption.) The “potential blockbuster” label belongs, as it always has, to Hurricane Ike, and he continues to be a major threat. But Alan Sullivan offers reasons to hope Ike’s re-intensification may not be too explosive — while at the same time urging that folks in the Florida Keys take this storm seriously:
Model consensus for Ike has shifted further left, and NHC has adjusted the track to brush the Cuban coast before recurvature. Ike has weakened further overnight, but reconnaissance finds the hurricane’s core intact, with a closed eye, so restrengthening may begin. Later today, however, Ike will move over waters well-worked by Hanna, and they may be less than generous feeding warmth to another storm so soon. Tomorrow there could be land interaction with Cuba. So we must consider Ike’s strength uncertain, and course-dependent.
With Ike threading the needle of the Florida Straits, or actually hitting Cuba (where Gustav caused “no casualties,” and US media repeated the lie) the threat to South Florida’s urban strip is diminishing. The Keys remain at greater risk. Only a small deviation could put Key West in the eye of a major hurricane. Take Ike seriously, citizens of the Conch Republic. This is not the time to buy booze for your storm party. This is time to get the hell out! …
I suppose I should mention the Gulf. Remember Gustav? It hit cooler water, entrained dry air, and went ashore with less force than expected. Don’t worry too much about Ike just yet. First, let’s see how it fares, if the core is disrupted by land interaction. Second, let’s get some notion of the later track. Third, let’s consider the dry air, which is spilling south ahead of schedule this fall. Yes, fall. It’s only technically summer now. The patterns resemble those typical of September’s last week, not its first.
Sound advice on all counts. With regard to the Keys, it’s quite possible Ike will be a “near miss,” or another “could have been worse” storm, but that’s no reason not to evacuate. We can’t know yet exactly where Ike will go, and by the time we do, it’ll be too late to evacuate. The Keys, like New Orleans, is one of those places that is inevitably going to be cursed with more than its fair share of “false alarms,” for the simple reason that folks have to evacuate early, if they’re ever going to evacuate at all — and the degree of vulnerability makes “never evacuating at all” an utterly foolhardy option, at least when we’re talking about major hurricanes.
9/6, 11:55 PM EDT: Can’t sleep, so I’ll post a late update on the Atlantic’s tropical trio: Hanna, Ike and Josephine.
Hanna is still a tropical storm as of 11:00 PM EDT, but Charleston radar seems to show a western eyewall trying to form, and the minimum central pressure has dropped to 978 millibars. This would normally signify roughly a borderline Category 1/2 hurricane, though every storm is a little different in terms of the exact relationship between pressure and wind speed. Regardless, the pressure has dropped 3 millibars since 8:00 PM and 6 millibars since 5:00 PM. So Hanna is certainly “deepening.”
Because a storm’s winds often take a few hours to “catch up” to drops in pressure, it wouldn’t be at all surprising to see Hanna’s maximum wind speed ramp up to minimal Cat. 1 hurricane status just before, or even immediately after, landfall — which, incidentally, should take place in 3-6 hours along the northeastern South Carolina coast (in contradiction to my earlier incorrect “midnight” reference; sorry about that). Of course, as the NHC points out, “THERE IS NOT MUCH DIFFERENCE BETWEEN A [70 MPH] TROPICAL STORM AND A [75 MPH] HURRICANE.”
You can follow Hanna’s progress live via this NWS radar loop, which should stay current throughout the night and morning:
Jared W. Smith, on his Charleston Weather Blog, writes at 10:34 PM EDT that “Hanna’s made a very sharp jog to the left”:
It’s looking more and more that unless the [predicted] northeast turn happens in the next couple hours from now, landfall will indeed be in northern Charleston County near Awendaw and Bulls Bay. . . . It’s hauling butt . . . As I write this, a squall associated with the inner core of the storm — which is rapidly regenerating — is coming ashore.
With regard to the NHC’s failure to upgrade Hanna to a hurricane, Alan Sullivan writes: “Maybe NHC is getting cautious about these borderline designations, after so many roastings by bloggers.” Heh. Sullivan himself, of course, has been one of the chief “roasters” in that regard. Anyway, he adds: “I see no dramatic wind readings at buoys or coastal stations. Still, Hanna will be an unpleasant experience for people in its path. Very heavy rain is falling in a band just inland and parallel to the coast of South and North Carolina. The intense squalls of the core are about to rake the shoreline near Myrtle Beach. Hunker down!”
THE TRACK GUIDANCE HAS COME INTO BETTER AGREEMENT . . . AND HAS ONCE AGAIN SHIFTED SOUTH AND WESTWARD. IN FACT…MOST OF THE RELIABLE GUIDANCE NOW TAKES HANNA EITHER OVER OR ALONG THE NORTH COAST OF CUBA. THE NEW TRACK HAS BEEN SHIFTED SOUTH AND WESTWARD OF THE PREVIOUS ADVISORY…AND IT IS ALSO A LITTLE FASTER. IT SHOULD BE NOTED…THAT THE DYNAMICAL MODEL CONSENSUS AND SEVERAL OF THE INDIVIDUAL MODELS ARE SOUTHWEST OF THE 4 AND 5 DAY NHC POSITIONS AND IF THIS TREND CONTINUES SOME ADDITIONAL WESTWARD SHIFT COULD BE REQUIRED.
The storm’s trajectory at the end of the five-day forecast period is, it must be said, a bit alarming — not New Orleans again! — but I suspect a sharper turn after 120 hours would be the expectation, leading to a landfall closer to the Florida panhandle. If anything, this might be another Ivan scenario, where the storm seems to take dead aim at N.O. but the forecast insists on a right turn, and we all bite our nails waiting for that predicted turn to happen. But of course, that’s all rampant speculation, as forecasts beyond five days pretty much always are. Bottom line, the whole eastern half of the Gulf coast needs to be watching Ike closely, and at this point, no one particular location is much more at risk for an eventual landfall than any other.
Well, except Key West, which is now in line for a direct hit from a 125 mph hurricane, if the official forecast is correct. That would be, um, bad. I really hope people heed the warnings:
With the potential of Hurricane Ike developing into a dangerous Category 4 storm that hits the Florida Keys, Monroe County authorities are urging everyone to take it seriously and heed evacuation orders issued Friday.
“This is a serious storm,” Key West Police Chief Donie Lee said. “People need to leave.”
Tourists must leave by 8 a.m. Saturday and residents must evacuate on Sunday in phases: by 8 a.m. for Lower Keys residents, noon for the Middle Keys and 4 p.m. for the Upper Keys.
“It sounds like we are at ground zero right now,” Marathon Mayor Pete Worthington said.
National Weather Service Key West office Chief Meteorologist Matt Strahan said people should not be fooled by any apparent weakening in the hurricane because that is expected to be temporary.
“Monroe County residents should not be lulled into a false sense of security,” Strahan said, explaining that Ike’s wind speeds could fluctuate — on Friday it dropped from a Category 4 to a 3 and could drop to a 2 even — but as Hanna pulls away, the hurricane could intensify into a Category 3 or 4 by Sunday.
“As a general rule, you could see your house not just flooded, but washed away if you’re on the right side of the track,” Strahan said. “If you are on the left side, the flooding could be as bad as Wilma. … “It’s a very dangerous storm track. It may look like its declining over the next few days, but it should pick back up.”
Speaking of which, I quote from the NHC discussion again, with regard to the intensity forecast:
THE NORTHEASTERLY SHEAR CURRENTLY DISRUPTING THE HURRICANE IS FORECAST TO ABATE DURING THE NEXT 12 TO 24 HOURS. SINCE IKE STILL APPEARS TO BE A VERY HEALTHY HURRICANE…LITTLE IF ANY ADDITIONAL WEAKENING IS EXPECTED BEFORE IT REACHES THE SOUTHEASTERN BAHAMAS. BEYOND 36 HOURS…THE SHEAR IS FORECAST TO BE VERY LIGHT AND THE ONLY NEGATIVE FACTOR FOR STRENGTHENING WILL BE POSSIBLE LAND INTERACTION. WITH THE OFFICIAL TRACK PREDICTION ALONG THE NORTHERN COAST OF CUBA…IT SHOWS ONLY SLIGHT WEAKENING DUE TO LAND. HOWEVER…IKE COULD BE WEAKER THAN SHOWN BELOW IF THE CENTER MOVES OVER CUBA…AND CONVERSELY COULD BE A LITTLE STRONGER IF IT REMAINS OVER WATER.
Stay tuned, as they say.
* * * * *
Oh, and if you’re wondering about Josephine — she’s been downgraded to a tropical depression, and advisories may be discontinued soon:
EXCEPT FOR A SMALL BURST OF CONVECTION THAT HAS RECENTLY DEVELOPED ABOUT 120 NM NORTHWEST OF THE CENTER OF JOSEPHINE…THE CYCLONE HAS BEEN UNABLE TO PRODUCE A SIGNIFICANT AREA OF DEEP THUNDERSTORM ACTIVITY FOR WELL OVER 12 HOURS. IN MOST CASES A SYSTEM LIKE THIS WOULD NORMALLY BE DECLARED A REMNANT LOW. SINCE THERE APPEARS TO BE SOME CHANCE FOR RE-STRENGTHENING LATER IN THE FORECAST PERIOD… ADVISORIES WILL BE CONTINUED FOR NOW. ADVISORIES COULD BE DISCONTINUED SOON…BUT COULD ALWAYS BE RESTARTED AGAIN IF THE SYSTEM RE-INTENSIFIES DOWN THE ROAD.
[T]he latest 18Z (2 pm EDT) computer model runs have completed. The newest tracks of the GFDL, HWRF, and UKMET are all about 50 miles further south than before, bringing Ike over eastern Cuba, then along Cuba or just south of Cuba before popping out into the Gulf of Mexico. The other two models, the GFS and NOGAPS, did not change their forecasts appreciably, and forecast a track through the Keys without hitting Cuba. These new model runs imply a slight lessening of the risk of Ike hitting South Florida, Southwest Florida, and the central and western Bahamas. However, the risk to the Keys is still unacceptably high, and a mandatory evacuation order has been given. I urge all Keys residents to comply with the evacuation orders. Ike is capable of causing a 14-foot storm surge in the Keys, as Hurricane Donna did in 1960. This is a storm you must evacuate for.
Here is the latest computer-model “spaghetti” track, courtesy of Jonathan Vigh, Colorado State University:
The easternmost turquoise track, it should noted, is not a “real” computer model, but a “dummy” model based purely on climatology and persistence. Likewise, the gray track that takes Ike over eastern Cuba and continues west-southwestward is simply the extrapolation of the current forward motion — not a computer model at all. In between those two lines lie the various reasonably likely scenarios for Ike’s future path. A wide range, as you can see.
The paths that take Ike over significant portions of Cuba would mean a weaker storm near south Florida, but would also guarantee that Cuba absorbs a terrible blow from a hurricane for the second time in barely a week — and on the opposite side of the island. A more southward track would also be terrible news for storm-ravaged Haiti, as Charles Fenwick points out. And such a track might not even save the U.S. coast, as Ike could easily re-strengthen over the Gulf after exiting Cuba, particularly if it heads toward the northern Gulf coast rather than Florida’s west coast. (Just because Gustav didn’t, doesn’t mean Ike won’t.) Still, the worst-case scenario for the U.S. remains if Ike “shoots the gap” between Florida and Cuba. And that’s still entirely possible.
Meanwhile, Alan Sullivan updates Hanna, the less dangerous but more imminent storm:
Hanna is maintaining strong, continuous convection at its core, and I would not be surprised to see an upgrade to hurricane at 11 PM advisory time. A strong outer band has recently formed northeast of the core and is racing toward the Outer Banks at this time. Weather will be worsening all night along this stretch of coast. From the present trend of coastal radar, Hanna’s center should come ashore obliquely southwest of Myrtle Beach. At present there is intense thunderstorm activity near the center, but no eyewall structure is discernable. That may change in the last hours before landfall.
This will be my last update tonight; I’m retiring now, to get some sleep and nurse my sore throat and cold. Next update will be sometime in the morning. In the mean time, you can track Hanna via the radar links above, and follow both Ike and Hanna via the various links in my sidebar at right.
First of all, I apologize for the long delay between updates. I’m feeling a bit under the weather (no pun intended) and, as a result, have been slacking on my hurricane-blogging duties. Sorry!
Anyway: Tropical Storm Hanna has regained its tropical-storm street cred, shedding the “subtropical” characteristics that had earned the scorn of some weatherbloggers yesterday. It will make landfall around midnight tonight, and wallop much of the East Coast tomorrow and early Sunday. Tropical storm and hurricane watches and warnings cover a wide area, from Georgia to Massachusetts:
Although it still won’t be a major disaster, Hanna is no longer just a glorified nor’easter. Alan Sullivan, who wrote yesterday morning that “if NHC were truly in the hurricane business, it would deem Hanna extratropical,” changed his tune last night, writing:
If present convective configuration persists until morning, the storm could hit the coastal waters with more force than I expected. In fact, I was premature in writing Hanna off as a tropical system. It seems to be reforming a core, and I am now quite sure it will be a minimal hurricane at landfall. Look out, Cape Lookout.
Hanna is almost a hurricane, and it will be at landfall. As I said earlier, look out, Cape Lookout. Hanna has recovered tropical characteristics. It has formed a new core, and it is feasting on the Gulf Stream. For a small area of the coast, right at the point of landfall, Hanna will be quite nasty. … The acceleration of forward speed means a stronger storm sooner for the Chesapeake Bay area.
Radar animations from the Charleston, SC radar show that Hanna does not have an eyewall, so this will limits its intensification potential. … [But] wind shear has fallen from 20 knots to 15 knots this afternoon, which may allow Hanna to intensify slightly before landfall. Visible satellite loops of Hanna show a much more symmetric and well-organized system, and Hanna will may start building an eyewall in the next few hours. However, it doesn’t have much time to do so, and the strongest it can get is a Category 1 hurricane with 80 mph winds.
Officially, as of 5:00 PM EDT, Hanna is just under hurricane strength with 70 mph maximum sustained winds. She has two more chances to be upgraded to a hurricane before landfall: at the 8:00 PM intermediate advisory, and at the 11:00 PM full advisory. As always, these advisories will be available at the National Hurricane Center website.
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Meanwhile, as expected, Hurricane Ike has weakened today, to a low-end Category 3 hurricane with 115 mph winds. However, the storm’s core is holding together, at least for now, as you can see on satellite. If that continues, strengthening — perhaps even rapid intensification back to a Cat. 4 monster — is likely later in the weekend, once the current wind shear diminishes.
The two scenarios most likely to prevent, or limit, significant re-intensification would be if: 1) the shear, over the course of the next day, significantly disrupts the organization of Ike’s core, which would likely slow the pace of re-organization once the shear abates (as we saw with Gustav in the Gulf); or 2) land interaction with Cuba further disrupts the storm.
At present, however, the forecast track does not predict the second scenario, and Dr. Masters wrote in a live chat earlier today that “there’s a very good chance [Ike] will ’shoot the gap’ between Cuba and S. Florida.” As for the first scenario, Ike’s core looks, if anything, better organized in the past few hours. Again quoting Dr. Masters from the live chat: “Remember how Gustav weakened and never recovered? That is possible with Ike, but I’d rate it only 20% likely that Ike won’t regain Cat 4 status in the future.” He gives Ike a slightly higher chance — 20-30% — of becoming a Category 5.
With regard to Ike’s likely U.S. target, the track has shifted left, and the storm is now a greater threat to the Gulf coast than previously thought. It’s too early to get overly exercised about that (we’re talking about a 5-7 day forecast at this point), but the more immediate worry is for the Florida Keys, which have been listed as the country’s third most vulnerable area to a hurricane strike (New Orleans is first). In the words of Dr. Masters: “If Ike misses Cuba, . . . the Keys can expect a major Category 3 or higher hurricane.” He adds:
The Florida Keys are highly vulnerable to hurricanes, and are at great risk from Ike. With only one road connecting the Keys to the mainland, 48-72 hours are required to evacuate the Keys. Tropical storm force winds can be expected in the Keys as early as Monday night, which means officials in the Keys may need to start ordering evacuations on Saturday morning. This would likely begin as an evacuation of visitors and tourists.
Of course, it’s not just the Keys that need to be concerned. The entire Florida peninsula is within the “cone of uncertainty,” and all Floridians, especially South Floridians, should be watching Ike closely this weekend. Hurricane Watches are likely by Sunday, and although nothing is certain, this storm could be a major disaster — for somebody — early next week.
As for why the track has shifted to the left, Dr. Masters explains:
The trough of low pressure expected to turn Ike to the north is, in general, weaker and slower moving than originally forecast, resulting in a delayed turn by Ike to the north. Several models–the UKMET, ECMWF, and Canadian–forecast the trough will not pull Ike to the north at all, and the storm will track west-northwest into the middle of the Gulf of Mexico by the middle of next week. The other models–NOGAPS, GFS, HWRF, and GFDL–all foresee a turn to the north, but this turn is delayed until Ike reaches the Keys. All of these scenarios look bad for the Florida Keys, and there is a high probability the Keys will have to be evacuated. . . .
Once the storm reaches the Keys, we have three models that turn Ike to the north, resulting in a Gulf Coast landfall along the west coast of Florida. Ike’s path and intensity could well imitate those of Hurricane Donna of 1960, which blasted through the Keys as a Category 4 hurricane, then up the west coast of Florida.
It is also possible that the trough of low pressure will not be strong enough to turn Ike to the north, and that the storm will enter the Gulf of Mexico. A second trough of low pressure would then turn Ike north later in the week, resulting in an eventual landfall on the Gulf Coast between the Florida Panhandle and Texas. This is the forecast of the ECMWF, UKMET, and Canadian models. It is too early to speculate where on the Gulf Coast Ike would hit.
As Masters put it in the aforementioned live chat, “Pretty much every spot on the entire Gulf Coast has had a model run that takes Ike there. The atmophere is too chaotic to make a skilled forecast more than 4 days out on Ike.”
P.S. Another important note from the live chat: “Ike will grow in size in coming days, and be about 2/3 Katrina size by the time it gets to the Keys. This will be a bigger hurricane than Andrew was.”
Just a quick update: Eric Berger writes that the computer models analyzing Hurricane Ike’s future have “clustered” around a track that takes the storm toward South Florida in 5-6 days. (See here.) Intensity estimates vary, but one important model, the HWRF, shows a 140-mph hurricane slamming Miami on Tuesday:
Of course, you can’t trust a five-day consensus forecast, let alone a five-day forecast from an individual computer model, with any degree of precision — and the models often overstate intensity — but, just to be clear, Ike is a real threat. Certainly, he is expected to be a major hurricane (i.e., 115 mph or above) at landfall, if he makes landfall. Ike will weaken tonight and tomorrow, but don’t let that fool you. Re-strengthening is expected.
Alan Sullivan, in Dania Beach, writes: “I just booked a room in Fort Myers. We’re getting out on Monday, if this thing is still on track.”
The 11:00 AM EDT advisories from the National Hurricane Center are filled with good news, as the trio of storms churning up the Atlantic — Tropical Storm Hanna, Hurricane Ike, and Tropical Storm Josephine — have all weakened a bit in the last six hours, and all are likely to either weaken or hold steady in the short term.
Hanna, for one, is arguably not truly a tropical cyclone anymore, and the odds of it becoming a hurricane seem to have diminished. Ike remains a much more serious threat, as I’ll explain in more detail after discussing Hanna.
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Hanna’s top winds have dropped from 70 mph to 65 mph, and although the storm is still officially predicted to reach hurricane strength before tomorrow night’s landfall in the Carolinas, the discussion suggests that such an eventuality has become less likely:
VERY DRY AIR ASSOCIATED WITH THE UPPER-LEVEL LOW OVER THE NORTHWESTERN BAHAMAS IS CHOKING OFF CONVECTION NEAR THE CORE OF HANNA…AND THE CYCLONE HAS A VERY SUBTROPICAL APPEARANCE. CONVECTION HAS DIMINISHED SUBSTANTIALLY OVER THE PAST 6-12 HOURS AND THE HIGHEST FLIGHT-LEVEL AND SFMR WINDS HAVE COME DOWN AS WELL. . . . CONDITIONS ARE NOT CONDUCIVE TO STRENGTHENING RIGHT NOW…WITH MODERATE SOUTHERLY SHEAR AND POOR THERMODYNAMICS. THE GFS SUGGESTS THAT DRY AIR IS LIKELY TO CONTINUE TO BE AN ISSUE UP TO LANDFALL. HOWEVER…AS HANNA AND THE UPPER LOW BEGIN TO SEPARATE SOME OF THE GLOBAL MODELS…INCLUDING THE GFS…SUGGEST THAT THE SHEAR WILL LESSEN SOMEWHAT. THIS WOULD ALLOW FOR SOME INTENSIFICATION…AND SO THE OFFICIAL FORECAST CONTINUES TO SHOW HANNA ATTAINING HURRICANE STRENGTH. THIS IS IN GOOD AGREEMENT WITH THE HWRF…ALTHOUGH THE GFDL AND SHIPS GUIDANCE IS LOWER.
The wind probabilities chart shows that whether Hanna will be a hurricane in 36 hours, just before landfall, is a meteorological coin toss: 50% chance it will, 50% chance it won’t. My gut would put those odds at more like 40%-60%.
It should also be noted that the concept of “landfall” is really rather meaningless, as it was with Fay. As the NHC puts it, “BECAUSE OF THE LARGE…SPRAWLING NATURE OF THE CIRCULATION…THE EXACT TRAJECTORY OF THE CENTER IS RELATIVELY UNIMPORTANT.” The worst weather will be north and east of the center. Hanna will be more like a strongish nor’easter than a major landfalling hurricane.
Indeed, the NHC forecasters are not the only ones to note that Hanna “HAS A VERY SUBTROPICAL APPEARANCE.” Dr. Jeff Masters writes:
Tropical Storm Hanna is a large and very odd looking near-hurricane. In fact, it looks to me like it is more like a subtropical storm than a tropical storm. A subtropical storm tends not to have any heavy thunderstorm activity near its center. Instead, the heaviest rain is located in a band 100 or more miles from the center. Satellite loops show that this is the case with Hanna.
Tropical storm Hanna does not look at all tropical this morning. . . . But there is little convection in Hanna now, and it is widely scattered along an arc that resembles a nor’easter, exactly as I foretold this time yesterday, when I observed the upper low deepening near Hanna. If NHC were truly in the hurricane business, it would deem Hanna extratropical. Even if convection flares anew before Carolina landfall, this will never be a genuine, warm-core tropical cyclone again. . . . For the coast, from the Carolinas northward, this will just be a warm version of a bad winter storm.
Bottom line, Hanna is not worthy of much hype. It will bring rain and storminess to the East Coast, but will hardly be a disaster.
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Ike, on the other hand, is most definitely a genuine tropical cyclone, and unquestionably has the potential to be a disaster. But Ike, too, has weakened this morning, from 145 mph to 140 mph. More importantly, it is likely to weaken further, according to the discussion:
IKE CONTINUES TO DISPLAY A WELL-DEFINED EYE WITH VERY COLD CLOUD TEMPERATURES IN THE EYEWALL. HOWEVER THE CLOUD PATTERN IS NOW ASYMMETRIC DUE TO SOME NORTHERLY SHEAR AFFECTING THE CYCLONE. . . . GLOBAL MODELS UNANIMOUSLY INCREASE THE SHEAR OVER IKE AND KEEP STRONG NORTHEASTERLY WINDS NEAR THE CYCLONE FOR THE NEXT FEW DAYS. THIS PATTERN SHOULD INDUCE A STEADY WEAKENING. IN ADDITION…INNER-CORE EYEWALL CYCLES COULD OCCUR…WHICH COULD WEAKEN IKE AS WELL. IN THE LONGER-TERM…THE SHEAR IS FORECAST TO RELAX AND SOME STRENGTHENING COULD OCCUR. HOWEVER…DEPENDING ON THE EXACT TRACK OF IKE…THE HURRICANE COULD BE IMPACTED BY COOLER WATERS NEAR THE SOUTHEASTERN BAHAMAS THAT HAVE BEEN STIRRED UP BY HANNA. THE OFFICIAL FORECAST IS LOWER THAN THE PREVIOUS ONE BUT STILL SHOWS IKE AS A POWERFUL HURRICANE THROUGHOUT THE PERIOD.
Specifically, the forecast calls for Ike to eventually restrengthen “only” to 115 mph, not 130 mph. And it sounds like the NHC thinks even that forecast might be a bit high, especially if Ike tracks into the southeastern Bahamas — which, as it happens, would be the most ominous track in terms of a potential U.S. landfall. In other words, the more likely Ike is to threaten land, the less likely it is to be a monster hurricane in five days. That’s a pretty good trade-off.
That said, there’s still time for additional strengthening even after the end of the five-day forecast — and furthermore, let’s not forget how poor our intensity-forecast skill is. Without question, Ike remains a serious threat. Blogging from his perch in South Florida, the usually hype-averse Sullivan writes that he has “a really bad feeling about Ike”:
[Ike] has overtaken Hanna’s outflow, and it is visibly weakening in the latest images. I would expect a significantly diminished Ike through the next day, with winds dropping under 110 mph by tomorrow. Ike’s course has also shifted more northwest. I am glad to see Ike gain latitude, but I am not confident that the storm will fail to dip back [south] again, as the offshore wind environment is shifting very rapidly. When a west or west southwest course sets up, Ike may also regain major hurricane status. This will be a very dangerous onset for the East Coast. Ike could make landfall anywhere from the Florida Keys to New England, depending on the exact time and pace of its recurvature, which is impossible to foretell at present.
Bottom line: I have a really bad feeling about Ike. Its early symmetry foretold rapid intensification. Its predecessor Hanna remains fairly weak, and will not use much of the available energy in waters off the eastern US. Ike is likely to strike some part of the eastern US with category three force or worse. Offshore recurvature is unlikely, though not beyond hope.
1. South Florida strike: I spoke with a hurricane scientist I know in Miami yesterday and he was quite concerned about this possibility. The models certainly support this, and the heat potential of the waters near the Bahamas and Florida is quite high enough to support a major hurricane.
2.Re-Curve into the Atlantic: The GFS model has been advertising this solution for a couple of days now. The Bahamas would still likely get hammered, but the mainland United States would be spared. This scenario is most consistent with the climatology outlined below.
3. Northeast U.S. Coast: As bad as a strike on Miami would be, a strike on New York is worse. (How do you evacuate 4 million people from New York?). A major hurricane striking New York remains a low threat, high consequence scenario, even with Ike. But the climatology below suggests it’s possible, and some models have been hinting at such a scenario.
One of the inevitable problems with the New York scenario (in any storm, not just Ike) is that, because a hurricane threatening the Northeast will almost by definition be moving very fast by the time it gets there, any potential NYC evacuation would have to be ordered when the storm is still ridiculously far away — like, down by Florida or Georgia — and when the forecast track is necessarily still subject to enormous errors, due to the distance and the oblique angle of approach. Once the storm is accelerating past the Carolinas and the Delmarva, it’s already too late to order big-city evacuations in the Northeast.
Anyway, “low threat, high consequence” is right. The odds of a disastrous New York landfall are always very low, as the conditions must line up just so — like threading a needle. But someday it’ll happen, and it’ll be bad. Here’s hoping “someday” isn’t next week!
Anyway, Dr. Masters discusses the various Ike scenarios in more detail; read the whole thing. And for what it’s worth, here’s the official forecast. But, as Sullivan, Berger, Masters and the NHC all say, it’s just too early to know where this thing will go.
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Last and least, Josephine, which continues to look like a “fish” storm — i.e., one that will stay safely out at sea — has weakened from 60 mph to 50 mph. That’s not as drastic as it might sound; because of the way the NHC rounds to the nearest 5 mph when it converts knots to miles-per-hour, there is no such thing as a 55 mph tropical storm.
However, as with Ike, this morning’s slight downgrade portends further weakening in the short term. The discussion notes that wind shear has blown away Josephine’s convection, exposing its center, and this shear is likely to continue for the next 36-48 hours. In addition, the water underneath Josephine is about to get cooler.
If Josephine survives the next two days, she may get stronger again, as shear may decrease and the storm will move back over warmer water. But, as I said, this storm is probably a “fish,” so my attention will remain squarely focused on Hanna and Ike for the moment.
I’ll be pretty busy this evening, liveblogging John McCain’s acceptance speech over on my other blog. But I will try to post at least one brief evening update here, particularly if anything major changes with Hanna or Ike. In the mean time, as always, you can get the latest official information from the NHC website, and the latest analysis from the weatherbloggers linked in my sidebar at right. Particularly worth waiting for is Dr. Masters’s afternoon update.
