Updating both storms this morning, as Hanna is becoming somewhat of a larger threat (nothing dramatic ...yet ...just some worrying signs). Im posting a little later than usual this morning, so let's get right to it...
While Louisiana gets hammered today, there actually is some good news from Gustav... several different points...
- According to recent aircraft reports from Gustav, he has continued to weaken... slightly ...sort of. Actually, his central pressure has just nudged up and down and is, for the most part, unchanged. This should mean no change in Gustav's intensity. Nonetheless, the aircraft has failed to find any impressive winds. As a result, the most recent National Hurricane Center advisory indicates - correctly, in my opinion - that Gustav is down to a Category 2. Of course, he's a high-end Cat 2, but still weaker, nonetheless.
- The latest forecast track:
...continues to indicate that Gustav will track far enough south for the core to avoid New Orleans. To be sure, New Orleans will get some nasty bands of rain and wind. In fact, they already have. But the eyewall will pass significantly far enough away to spare them the brunt. Unfortunately, locations around Morgan City will fare much worse. But as for the potential for a repeat disaster in New Orleans. I guess we can only wait and see how the levees hold. But the specifics of Gustav are such that New Orleans should come through this fine.
- Another issue helping to spare New Orleans is Gustav's lopsidedness. Check out the recent satellite image:
...most of the deep convection (i.e., heavy thunderstom activity ...the reds on that image) is to the south of Gustav's center. As a result, New Orleans, and really almost all of Louisiana not right on Gustav's direct path, will miss the worst of the storm.
That's really about it on Gustav. Not much to discuss in terms of forecast as Gustav is already coming ashore - definitely somewhat sooner than expected. Here's a radar image as of about 9:30AM:
...you can see the eye of Gustav already coming ashore.
So, now, switching gears to Hanna. Latest satellite loops, both "visible" and "infrared" are rather concerning. All the talk for the next 24-48 hours is supposed to be wind shear, wind shear, wind shear. Here's how Hanna looks now (this is "water vapor" imagery):
...the lack of clouds "fanning out" to the north is indicative of that northerly shear. So, clearly, there is some shear. But if you click on one of the satellite loops above, you'll see (as of Monday morning) the cloud shield and deep convection rebuild northward a bit, over the center of Hanna.
Likewise, the National Hurricane Center's latest discussion on Hanna talks about the fact that Hanna may be stronger than they are currently indicating. They are awaiting (as am I!!) aircraft to get to Hanna later today and get a better read on her intensity.
Here's where various models sent Hanna:
...you can see pretty good agreement there, other than the yellow line on that map. All other models are focused between Jacksonville, FL and Charleston, SC. Based on the overall upper level flow, I'm anticipating landfall near the western potion of this "envelop" of solutions... probably somewhere between Savannah, GA and Jacksonville, FL.
Word of warning, if landfall is where I'm thinking... Due to the concave shape of the coastline, combined with the typical direction of motion of storms in that area, that stretch of coastline rarely suffers a direct hit from a hurricane. They get plenty of remnant, of course, but a direct landfall? ...very uncommon. So, I'm concerned that folks there may be unprepared.
At this point, the National Hurricane Center projects Hanna to be only a Category 1 at landfall. That would be a relief as Category One's usually do little damage ...*usually* (Katrina was pretty nasty in Florida). The problem is, there seems to be a large possibility for Hanna to be stronger. First, there's NHC's aforementioned comment - that Hanna may already be stronger. And, next, here are what the intensity models show:
...the National Hurricane Center (black line on that map) show landfall as a 65kt (75mph) storm. The tropical models, though, are cranking Hanna up much, much stronger. One tropical model, called the HWRF, bring Hanna to about 95kts... nearly a Category 3 and as strong as Gustav is now. The other key tropical model, the GFDL, has her at about the same (gets her to 100kts - Category 3 - briefly, but ticks her down to 95kts by landfall). And, third, there is an outside chance of a period of rapid intensification - which is something the models don't typically handle well. So, Hanna could ramp up quickly at some point and even exceed model forecasts. She'll be crossing the Gulf Stream and there will be upper level atmospheric conditions developing - after the shear abates - that will be very favorable for development. The NHC discussion linked above talks about the 200mb winds and double-jet structure, etc. Let me just briefly explain what they're talking about...
...air rises rapidly in a hurricane (except in the eye). As a result, in the high levels of the atmosphere (200mb is a level of the atmosphere which is quite high up), the air pushes outward from the hurricane. So, any surrounding atmospheric flow that assists this can actually help pull the air out of the storm and force more upward motion. The "jet" they mention is the high level jet stream... a streak of fast wind... that will assist in pulling air out of the storm. In other words, those conditions will help Hanna intensify.
Bottom line with Hanna... NHC's forecast:
...has Hanna making landfall Friday near the GA/SC border as a Category 1 hurricane. Obviously, that's the official word based on which people should be preparing. By my own thinking is that Hanna comes ashore Friday a little further south, perhaps towards Savannah, as a Category 2 hurricane. But please remember, Hanna is sort of wandering around right now. Any weird gyrations in her motion may force the eventual track to shift around. So, we just need to keep watching her right now.
Running very late now, so going to end it here and get this posted.