Good morning everyone. As I've done all week, it's time to take a look at Gustav. This situation is becoming increasingly threatening. Before getting to the discussion, let me thank the commenters yesterday who did such a wonderful job of keeping everyone informed. I am out of town, busy working on a house (repairs from major flood damage, so I sympathize with those in harm's way!), and in a pretty remote location - relegated to 24kbps dialup modem. So, I'm lucky I can even post what I can. I may be back home and in full broadband mode by this afternoon... so, "normal" updates later today may be back on. In the meantime... commenters, keep it flying!! Thanks!!
Well, it's a good news, bad news morning with Gustav. Let's get the bad news out of the way. Given the discussion yesterday, you'll recall that Gustav persistently ran east of the forecasts. I checked again last night... briefly (though didn't issue an update, since we'd rolled off the rec list, so probably no one would see an update)... and saw that Gustav continued to push east of the forecasts. In fact, one of the supposed-to-be-best forecast models out there (called the HWRF) was simply abysmal. By yesterday evening, its most recent forecast was already incorrect (after only 6-hours into the forecast) by a half a degree longitude. That is a massive error from one of the "best" models. Not surprisingly, it, and most other models have nudged eastward. Here's what the latest guidance looks like:
As I write this, I'm awaiting some new model data (and, yes, it'll be in before I finish this), but the point is... Gustav is clearly tracking on the eastern edge of the guidance - actually, almost east of all of it. And, now, a track very near New Orleans is becoming increasingly likely. The will put New Orleans in the eyewall and in the core of the storm. Of course, we shouldn't forget our friends in the more rural areas and smaller cities. While this is all bad news for folks in New Orleans, Pascagoula, Bay St Louis, and even Mobile... this is good news for the smaller towns throughout south-central and southwestern Louisiana, as well as Cameron, Lake Charles, Beaumont, Port Arthur, Houston and Galveston. UPDATE See below for that new model data, which actually implies more of the westward track again... of course, it's just a model.
Nonetheless, with New Orleans always having been the biggest city closest to the track... this track adjustment is simply not good news.
But there is some genuinely good news as well. Satellite imagery indicates that Gustav has weakened dramatically. To be clear, he remains a strong storm and may well rebound some. But in the satellite depiction:
...notice how Gustav doesn't exactly have the classic hurricane depiction. He is clearly being disrupted by non-optimal (for development) upper level conditions. You'll hear a lot about how he weakened over Cuba. He did. But this is not all about Cuba. Gustav has also weakened due to less favorable upper level conditions. This is very important because it means that he may not be able to re-intensify as much as fast. Some re-intensification still looks like a good bet, since Gustav will be traversing some very hot water. But, immediate, massive intensification looks unlikely.
...this is verified be reconnaissance aircraft data. Even though Gustav has been back out over water for some time, his central pressure (which is indicative of intensity ...lower pressure = stronger storm) has held steady. Most recently (just after 7AM EDT), the aircraft reported a pressure in Gustav of 960mb. Prior to that, it reported 959mb. Though it also got 960mb prior to that - so, I don't think Gustav continues to weaken. But he is not re-intensifying. Those same aircraft reports have gotten winds "only" up to 113kts (130mph). At their flight level, surface winds should be 100-110kts (115-125mph), but their onboard instrumentation (called a Stepped-Frequency Microwave Radiometer) which can "see" surface winds - to put it simply - estimates those winds to be, at most, 100kts (115mph). Officially, as of 5AM EDT (8AM update not yet available as I write this... but given Gustav's steady-state, they may well just leave it alone) the official National Hurricane Center advisory had Gustav at 110kts (125mph). But, as you can see from the above data, this is probably a high estimate (and NHC acknowledges this in their discussion). In reality, Gustav is around a 100kt storm... still a major hurricane... but barely.
Okay, that new model data I was awaiting is in. The latest HWRF (one of two hurricane-specific models) has, a bit surprisingly, actually shifted west a bit, back towards a central Louisiana landfall. It shows landfall Monday afternoon (*yes, this is earlier than previously anticipated and means LESS time for preparations*). And with little change in intensification along the way, has Gustav landfalling as a Category 3. Notably, though its pressure reflection looks poor, in terms of winds, the HWRF does knock Gustav back a bit immediately, before he recovers some... this does appear to be what's going on. Perhaps the HWRF just got lucky on that, given its mediocre performance to date, but that intensity forecast looks reasonable. As for the other hurricane-specific model, the GFDL (which is generally more highly regarded than the HWRF, even though the HWRF is newer), it has a nearly identical track (shifted a bit west, to central Louisiana). But it, unfortunately, shows a "better" (...worse, for Louisianans) recovery for Gustav, having him just attaining Category 4 strength before plowing ashore. The GFDL has landfall a bit later, but still Monday... Monday evening.
...now, one thing we should quickly examine, given the ongoing errors... These models take some time to run. So, even though they're brand new information, their "initial time" was six hours ago. So, we can already begin to verify them. In six hours (by 8AM EDT Sunday) the GFDL put Gustav at 24.64N, 85.24W. The HWRF had 24.80N, 85.30W. The 7AM aircraft "fix" has him at 24.53N, 85.33W. That, for a big change, is actually southwest of the model predictions. The GFDL is quite close (so its slightly later landfall may well be correct). This, perhaps, negates some of that "bad news" mentioned up top, as Gustav may still manage to hold west of New Orleans just far enough. Nonetheless, this is still east from some of the track forecasts we saw 24 hours ago. Not to mention that fact that, as we've seen repeatedly, these models are prone to errors. So, I'm certainly not sounding an all-clear for N.O. ...just saying that Gustav may hold just west enough to spare them.
Hopefully, these more westward tracks will verify. I have repeatedly argued that even a central Louisiana landfall would spare New Orleans the brunt. There is a new theme at the NHC about not focusing on the precise landfall point. There is some relevance to that, but it is as much due to potential forecast errors as the storm itself. That is, for the storm impacts, precise landfall location is critical. The eye diameter is typically (with significant storm to storm variations) only about 20 miles wide. And the eyewall, where the massive destruction tends to occur, is only about a 10 mile wide ring around the eye (again, with some variation depending on the storm). That's only about a 40 mile wide swath of destruction... maybe a bit larger, since the winds don't just drop off instantaneously beyond the eyewall. So, let's just roughly estimate it at 60miles. That's 30 miles either side of the eye. So, all Gustav needs to do is come into Louisiana more than 30 miles west of New Orleans and they'll be spared the destructive winds AND, more importantly, the destructivly high storm surge. For eample, here's the GFDL's wind field near landfall:
...notice that in New Orleans it's little more than a simply windy day. Over the friction-free open waters of Lake Ponchartrain the winds are howling to hurricane force, but they'd be out of the southeast. So, communities on the northwest side of the lake may see some problems, but New Orleans would avoid significant issues.
On the negative side, Gustav slowing after landfall could cause some freshwater flooding problems (rain). Here's the GFDL's rainfall map:
...concentrate on the image on the left (total rainfall). New Orleans picks up about 20cm (about 8") of rain from Gustav. The only good thing is, they're not in the bullseye... That's up near the "ArkLaTex" where over 16" of rain falls.
Okay, that's a loooooong write-up this morning. So, let's summarize here:
- Gustav no longer running east of track. In fact, the hurricane models (HWRF and GFDL) have actually shifted west a bit. But that is on the western side of the track guidance, so I'd still anticipate Gustav coming in a bit east of them. That means still expecting landfall near Morgan City, LA. And, I should clarify, given the Louisiana coastline, Gustav is actually likely to cross land in a smaller coastal town to the southeast of Morgan City.
- Still expecting landfall as a Category 3, as Gustav should intensify modestly in the next 24 hours, then weaken slightly prior to landfall.
- The one change... timing ...Gustav looks to come ashore Monday evening - possibly even early evening (4-6PM). Note that that's the time for the actual eye making landfall ...conditions will turn nasty in Louisiana long before that. This is important... it means that today is it, folks. If you live in or have loved ones in the threatened area, today is the final day to get out - if traffic conditions even allow that at this point - or complete preparations.
- Flooding from rainfall will also be an issue, so folks living very near volatile streams and rivers should also consider evacuating. Do not assume that, since the rainfall is a days-long event, and some rivers take time to crest, that you can easily leave later. Remember, tree damage may render certain roads impassible. I'm not trying to recommend excess evacuations (*over*-evacuating can be as much a problem as people not evacuating ...some inland folks needlessly evacuating can clog the roads for people who truly must get out), but be sensible ...and rainfall flooding is another serious thing to consider.
In closing, note that at 8AM EDT the NHC official update has (correctly) nudged Gustav's intensity down a bit (to 105kts ...or 120mph ...and that may still be a little high). New reconnaissance aircraft data is limited (no new "fix", just some additional general reports), but suggests little change. Ditto for recent satellite imagery. And, on a side note, I have no comment on Hanna. My slow connection and time limitations have me focused on the more imminent threat... Gustav.
Again today, updates will be limited, due to my circumstances. So, I'd encourage commenters to share the latest facts. But I will try to get updates out if/when I can... esp. later this afternoon.
UPDATE 12:50PM EDT ...a very, very brief update. Gustav continues to hold steady or weaken slightly. No reconnaissance aircraft in a while, but the last one showed a 962mb central pressure. That's up (weaker) by 2mb than early in the morning. Indeed, the National Hurricane Center has pretty much held Gustav steady, at 105kts. I still think this is a bit too high. Likewise, I think they push him up in intensity a bit too much by landfall... they put him on the Category 3/4 cusp... at 115kts (about 135mph). I believe Gustav is likely presently at about 100kts, that he'll be up to 110kts tomorrow morning, then back down slightly to 105kts by landfall.
The latest satellite imagery tells the picture:
..notice the lack of "blowoff" clouds on the south side. That is being caused by southerly shear. Notice also the rather ill defined nature of the eye. Gustav is clearly struggling (which is a good thing). But also notice that there is still some deep significant deep convection around the eye. So, Gustav also isn't going to be weakening much either.
Anyway, really not much change to the forecast. Like I said, I think the NHC has Gustav a bit strong. But, no matter, he'll likely still landfall as a major hurricane. Also, if you notice their track forecast, it's pretty much what's been talked about here... so, there's a lot of agreement on this... Gustav coming ashore near Morgan City (actually, to the southeast of there) during the second half of the day Monday (NHC does have landfall a bit earlier than I was thinking... but that really doesn't matter - conditions will be nasty long before landfall). So, that's about it for now.
UPDATEx2 5PM EDT ...unfortunately, I need to head out the door for the evening. So, this will be my last update today. I will likely post tomorrow morning, but at that point it's mostly just the fine-tuning look at the last minute specifics. Of course, it won't be irrelevant - after all Gustav could easily take a last minute bump east or west, which would be critical for New Orleans (and surrounding areas). So, we'll still take a look at the situation Monday morning. Also, I'll probably take a look at Hanna. I don't want to continually flood dKos - "Politics Central" for me!! - with weather stuff. But there seems to be interest and, in my view (though, as a meteorologist, maybe my view is skewed!), the real life immediacy of a tropical cyclone takes precedent over campaign tactics and whether or not I like Sarah Palin (I do not... gee, how did you guess?).
Anyway, I wish I could report to you that Gustav has continued weakening. Unfortunately, I cannot. Recent reconnaissance aircraft reports show a central pressure of 957mb. This is back down (down = stronger storm) from earlier in the day. It is not an impressive drop, and Gustav is not showing any signs of rapid intensification. Recent visible satellite imagery:
...continues to show no well defined eye. As commenters have noted throughout the day, there have been moments when Gustav's eye looked like it was becoming more prominent. But, it's been just coming and going. And, right now, it's not very visible. Moreover, infrared satellite imagery:
...shows that Gustav remains lopsided, with most of the deep convection (the red in that image) to the southwest of the center.
So, the good news is that Gustav has made no great intensification strides today. And the better news is that so long as he remains lopsided to the south, the most severe conditions may remain offshore (once that convective mass gets onshore, Gustav's eye will already be ashore and, so, he will be weakening). Unfortunately, like I said, it's not all good news. That convection (which drives a storm) is plenty deep and just organized enough to push down Gustav's pressure a bit. As such, winds (and resultant storm surge) may come up a bit overnight. The winds often lag the pressure, and recon has shown no signs of a wind increase yet. Gustav is still a 100kt hurricane, in my view (NHC's official report says he's a bit stronger).
...any intensification that does occur, since the storm is still struggling, should be modest, as noted in my previous update. And I do still anticipate some minor weakening prior to landfall. So, a 100-105kt Category 3 hurricane remains the best bet.
Recent track models:
...focus - on average - a little west of what my thinking has been. But there's certainly a cluster aiming towards Morgan City, and short-term verifications from the recon positions once again indicate that Gustav is leaning towards the right (east) side of the tracks. So, I'm still thinking that Morgan City will be the target (again, some point to the southeast of that will be the actual landfall point.
As I finish this up, I see the new NHC forecast is in and they have (*correctly*) reduced Gustav's initial intensity to 100kts. The do bring him back up a bit overnight, but as discussed, that seems perfectly reasonable. And they have held their track... to the east... near Morgan City. So, with their very slight reduction in intensity (current and forecast), I have to say, I agree 100% with exactly what the National Hurricane Center is presently projecting.
On a final note, since potential landfall may be less than five days away, here's a track map of the models for Hanna:
...note that they are focused on a landfall around Friday in the Southeastern U.S... with a wide amount of variation. Frankly, I don't have a strong opinion on this just yet, except that I'd be generally more favorable to a more westward track (FL/GA/SC rather than NC). Also, please be aware that most of the best models are stronger than the National Hurricane Center's official forecast. I can definitely understand NHC's hesitancy, given Hanna's slow development to date. So, I have no problem with what they've got so far. But just know that there is some potential for a more significant storm.