A new day has dawned and there a whole new set of data to digest on Hanna and Ike. Hanna is pretty much set, so I'll begin focusing more on Ike. But there are definitely still some issues to deal with on Hanna. So, I will give her some attention. Ike is a beast of a different kind. The model guidance has shown a decided westward shift. And one of the northern group of models (the American) has jumped into the southern camp... making for a bit better agreement. But mostly, there was just a shift... no significant convergence. And now, with that shift, the threat to Hispaniola and Cuba is increased, as has the threat to Florida... and it is within the 5-day window, so we've really got to begin the process of trying to pin this down a bit - not an easy task. As always, updates will be posted as time allows (I do these write-ups in my spare time from work). So, if this is of interest/concern to you and we fail to make or get bumped off the rec list, please feel free to "subscribe" to or bookmark this diary.
Okay, let's start with Hanna. Her track is pretty well set. Here's the National Hurricane Center's official track for Hanna:
...I think Hanna may track just a touch to the west of that, but, really, it's splitting hairs. If Hanna were a major hurricane, it would matter much more. When considering the devestation of an eyewall impact, a 20 or 30 mile shift in track is critical, especially to people in harm's way. And the NHC track does have a significant population center (Wilmington, NC) very near landfall. However, in this particular case... Hanna has a broad wind field with no inner core. As a result, landfall near Wilmington, NC, or Myrtle Beach, SC is pretty meaningless in terms of wind impacts. That's not to say the wind itself will be meaningless. 50-60kt winds is enough to bring down tree limbs and weak trees and churn up enough surf (especially with Hanna large "fetch") to cause beach erosion and dangerous rip currents. So, don't take it lightly. My point is just that winds at Wilmington, NC and Myrtle Beach, SC will be pretty similar regardless of which of the two locales Hanna passes closest to. The biggest difference with the wind, in terms of erosion, will be its direction... for example, a landfall up near Wilmington would give Myrtle Beach an offshore wind and reduce some of the heavy surf and erosion impacts. Winds there also might be a bit lighter just because they'll be coming over land, reduced by frictional effects... but, again, the wind speed differences should be modest.
The only two issues with Hanna are whether she'll intensify before landfall and that subtle track differences do impact potentially flooding rainfall amounts (but Hanna's forward speed should reduce flooding concerns considerably). As for her intensification potential. Here's what she looked like just a little while ago:
...much like yesterday, an amorphous blob once again. But one difference from yesterday is that there is some convection (the dark reds) on that image. That convection is near (but not entirely over) the center, so it's impact is marginal. But it has managed to deepen the storm a bit (recall from previous write-ups that convection acts like a pump to decrease the central pressure of, or strengthen, a storm). According to aircraft reconnaissance reports the central pressure has dropped to 980mb... 8mb deeper than yesterday, which isn't dramatic, but neither is it insignificant. And, in fact, maximum flight level winds have increased to 70kts. That supports 60kts at the surface... though the NHC correctly points out that these winds are not getting to the surface as efficiently as is normally the case with a tropical cyclone. So, officially, Hanna has not intensified. But given the overall trend, I have to presume some very slight intensification will occur. The previous link shows NHC's forecast, and they indicate the same... up to 60kts by landfall. So, Hanna should be a strong tropical storm by landfall, with an outside chance of nudging up to a minimal hurricane.
As for the rainfall, that's much more sensitive to track. Here's a rainfall map from a model with a more eastward track:
...and one with a more westward track:
Note that that more eastward track is from the overnight medium-range American model (GFS). A new early morning run is more westward. And as I was already favoring the slightly more westward track, that means I prefer that second image above... though the model showing that (the short-range American model... called the NAM) appears to move Hanna a bit slow, which may overenhance rainfall a bit. So, I'm expecting the maximum rainfall to be a 4-6" swath from central MD up through easter PA, northern NJ, southeast NY, and up through western and central New England. Note that rainfall amounts of this magnitude aren't likely to cause major flooding problems - more localized effects. But it is close. For example, flash flood guidance for Pennsylvania for a 12hr period is right in that 4-6" range for most areas. Therefore, severe flooding isn't expected. But since we're right on the cusp of the flash flood guidance for the peak rainfall areas, there could be some minor stream and river flooding. So, that's a hazard to be aware of.
Moving on to Ike, the model guidance this morning has given me a few more gray hairs. What a mess. Here's how the overnight guidance looked:
...not a whole lot new since the above image was produced. But the GFS (the American model - labeled AVNO on that image) has had a new run, and it has shifted farther west into the eastern Gulf of Mexico. Though it does at least have a turn which is abrupt enough to get Ike up to the Florida Panhandle eventually. I don't mean to make that sound "good"... obviously, for Panhandle residents that's not a good thing. But just from a forecast perspective it's a bit of a relief. Recall, two days ago, I indicated little to no threat west of Florida. So, I'd really rather not see the model guidance shift out beyond the Panhandle. But we do have one model showing that! The European model, which is not on that graphic, for the second run in a row landfalls Ike on Louisiana next Saturday. But...
...that solution is an outlier not just because it's so far west. It is also alone in how it gets there. Three cold fronts sweep across the country next week. All but one model now agree... the second cold front will pick up Ike. The only reason for the westward model shift is either Ike moving faster, the cold front moving slower, or a combination thereof. The one exception? The Euro model. It has Ike catching the third cold front. So, at this point, I believe it's wrong. But central/western Gulf residents should be aware that at least one bit of guidance does show a threat. So, the door is not completely closed to you... keep an eye out. (Eastern Gulf residents were never beyond threat - though it seemed reduced yesterday).
Similarly, this westward shift is accompanied, on some models, by a southward shift a well... so Cuba and Hispaniola also face a more serious threat. As you see from the above graphic, most models still do not show an actual landfall in either location (though the ones that do aren't unreliable models - so the threat is real). So, a direct strike on either island isn't low risk, but it's less than 50/50. And if Ike passes to the north, they'll be on the weak side of him. So, rainfall, flooding and mudslides will be the key threat down there. Check out the story about Hatian rescue efforts after rainfall from Tropical Storm Hanna. The last thing these poor folks need is Ike.
So, what does all this mean... a westward shift, but thinking that the Euro model is wrong, and that the southernmost tracks are overdone? Well, what it means is that, once again, the NHC seems to be on target. They are hedging a bit in their most recent forecast... just trying to split the difference of the models. But, I can't blame them. Given the seeming random shifts back and forth (models trended east yesterday), it is very difficult to nail Ike down. To be clear, the general idea is pretty simple... a west or westsouthwest track, bending around to west or westnorthwest over the coming three to four days, then gradually bending more northward in time thereafter. That seems pretty well set. It is the details that are a disaster. And I like how NHC is handling it. Here's their forecast:
...keep in mind, there is a large error, typically, in five day forecasts. So, south Floridians needn't panic just yet. But, obviously, folks throughout the Bahamas, southeastern U.S. (including eastern Gulf states), Cuba and Hispaniola need to be monitoring Ike extremely closely.
On the plus side, Ike has weakened some. Officially, he's down to 105kts, and here's a recent look at him:
...I will grant you that that image is still very impressive. But the convection around the eye is less symmetric (which has some important relation to a storm's intensity) than it was yesterday. And I grabbed that image when I began this write-up. Since then, some new imagery has come in. I'd encourage you to check it out here. If you look at the link (a loop of Ike) you'll see that he is deteriorating significantly in the face of strong northerly shear. That shear will continue today, and Ike will likely be knocked back to a Category 2 hurricane, and maybe even a Category 1 at some point. The model guidance intensity forecasts show the following:
...the HWRF and GFDN are the only two showing the appropriate short term weakening. So, I like how they handle Ike. So, what to they do in the longer range? Well, by the end of the period the HWRF has Ike up in the 110-120kt (125-140mph) range, while the GFDN is in the 90-105kt (105-120mph) range. NHC (the black line on that plot) handles it right again, in my view. The GFDN hasn't done great and has a track probably a bit too far north; but the HWRF has over-forecast almost every storm. So, split the difference. Obviously, there is a lot of room for error here - please keep that in mind... but the basic gist of it is that Ike should weaken to a Category 2 today and perhaps even down to a Category 1 tomorrow. Thereafter, he should rebound to somewhere in the Category 3 range approaching and moving through the Bahamas. Note that there is not universal agreement on this. The statistical model (called SHIPS) weakens Ike to a strong Category 1, but never re-intensifies him. The NHC addressed this in their discussion and they do not believe this model sufficiently reflects the reduction in wind shear after tomorrow. I concur... there should be at least some modest improvement in Ike beyond 48 hours. The only reason I could see this not occurring is if the inner core of Ike is too disrupted - if that occurs, it often takes storms many days to recover, if at all. So, let's hope that occurs. But, at this point, I don't believe that's likely. I'm in complete agreement with NHC's forecast, which has Ike at a Category 3 or Category 4 at landfall.
The biggest thing I have to remind people is that the potential landfall is about 5 days away (possibly later, depending on specifics). And earlier impacts on the Bahamas, Hispaniola and eastern Cuba are still 3-4 days away. So, there remains much room for error... both in track and intensity. So, if you're in a threatened area, please keep a close watch on Ike. But at this point, with so much doubt and question, there's no need for alarmism or panicky worry. Just stay on top of the situation. And, of course, I'll update here as time allows.
UPDATE 11:15AM EDT First, Hanna. Nothing much to report based on the latest NHC advisory. They've shifted their track a bit west, but nothing much else of note. However, there is some "real time" data which is more revealing and important. First, Hanna's center shifted westward under the deep convection (see satellite image from the original post). So, this confirms NHC's official shift. This means landfall between Charleston and Myrtle Beach, SC. As noted in the main discussion, this precise landfall point won't mean too much. But, it will increase surf and erosion for places who were previously expected to be on the south side of landfall (most notably, Myrtle Beach), and will allow for more nasty weather further down the coast.
The other "real time" update with Hanna is intensity. NHC hasn't adjusted her intensity, as radar velocities do no support it. But radar out of Jacksonville can't "see" all of Hanna, and reconnaissance aircraft is en route, but not on site yet. Based on the persistence of convection over the center, combined with earlier reports of pressure falls, I suspect Hanna may be intensifying... not rapidly... but intensifying. With less than 24hrs before landfall, and only slow intensification, I'm not sure she'll make it up to a Category 1 hurricane, but the threat of that is certainly increased.
With Ike, he continues to take a beating and is tracking south of west. The weakening is expected and in line with the forecast - no surprise there. But the track is running on the south side of guidance. So, NHC now tracks Ike south of Florida by day 5 (but close enough for major impact). It should be noted that a turn is beginning late in the period on their forecast... so, it still looks like a hard turn north to the Florida west coast, across Florida and up or off the East Coast. To be clear, that is beyond the NHC forecast and NHC is NOT forecasting that. I'm merely projecting beyond that based on their forecast. But, typically, even the four and five day errors are pretty large. So, projecting beyond that is mainly guesswork - I'm merely sharing that so that you know what that best guess may be at this point.
Next update (this afternoon) I'll try to provide some graphics. And as I finish this up, new recon hints (no actual fix yet) that pressure continue to fall in Hanna, but slowly... so, very slow intensification may, indeed, be underway. I do not anticipate major intensification of her prior to landfall.
UPDATE 2:30PM EDT A whole new round of model data and some new reconnaissance data, and, yet, only a little bit of important info to pass along. First, on Hanna...
The 2PM EDT intermediate advisory from NHC has upped Hanna to a 60kt (70mph) tropical storm. This is strongly supported by some of the most recent aircraft recon data, which clocked flight level winds of 75kts (85mph). The typical reduction to surface for these winds is 65kts (75mph), or a Category 1 hurricane. However, the NHC continues to opt to hedge low on the surface winds. Can't say that I blame them... buoy and dropsonde reports don't even really support 60kts. But with flight level winds increasing to 75kts, pressures holding rather low (for a mere tropical storm), and continued improved satellite presentation, you've got to increase her intensity a bit, under the assumption that the strongest surface winds simply haven't been sampled... and they've done so. Speaking of her satellite presentation, here it is:
...compared to the image posted earlier, you can see she's much better organized, although not impressive. So, there remains a very real chance of her becoming a minimal hurricane by landfall. And as for where that landfall occurs... no change since the 11AM update. Hanna has begun accelerating north, so there seems to be little concern for another last-minute westward adjustment. So, that's on track, as is the rain forecast - similar to that discussed above.
As for Ike, he continues getting run over be shear. Here's how he looks now:
...no eye, and much poorer presentation. Recon has indicated that he is likely down to a strong Category 2 now. They've clocked flight level winds of 105kts, which reduces to surface winds of 95kts. This is not official at this time, so we can only wait and see what NHC does, but that's what recon supports.
The track remains a complicated mess. Rather surprising is that the lone, outlier from yesterday, has been joined by both the UK model and the Canadian in its far west solution, all the while holding to its west solution. I argued yesterday and even in the comments of this thread that such a solution seems highly unlikely... it seemed virtually impossible to get Ike that far west with two strong troughs swinging by the the north. Yet, here we sit with three models on board. How do they manage this trick? Push Ike further south and across Cuba to avoid the troughs to the north. The real difficulty here is that the remaining solutions have tightened up, with the HWRF, GFS and NOGAPS all agreeing on a track across or just south of southern Florida, then a hard turn up the Florida west coast... this is within the range of the previous thinking. It is also virtually identical to the NHC track.
So, we've got a battle of three models on each side. Which is correct? Well, I'm continuing to lean towards the GFS/NOGAPS/HWRF solution. Why? The GFDL mostly agrees. It does start farther south, slamming Cuba first, but it also then turns pretty hard towards the Florida west coast. Second, regardless of the UK and Canadian agreement, the Euro still has a left of track (west) bias. Meanwhile, the three worst models this season have been the UK, Canadian and Navy... two of them team up with the Euro, one with the GFS. Finally, with such a questionable forecast, I find it reasonable to defer to NHC. For all those reasons, I'd say follow the NHC track, which is generally in line with expectations anyway, but be very aware of the high level of uncertainty. That's it for now.