You might want to pack up, and then watch the 10 am CDT projections to see whether the probabilities go down. The most likely scenario still seems to be that it will track just east of New Orleans. The highest probability is at Buras, LA.
My houseguests from Houston are supposed to be leaving today. Maybe I'll just follow them home. Of course, the normally 4-hour drive will probably take 20 hours with all the traffic.
http://www.millenniumweather.com/tropical/discuss.html
Tropical Weather Discussion
by Gary Gray
Katrina struggled to spin up most of Saturday afternoon and evening. Although her pressure dropped slowly and steadily and, after a bit of raggedness in the morning, she improved in appearance as well. However, the spiral nature of her inner core made development of a well defined eye impossible. In fact, her pressure dropped to 939mb, supportive of a Category 4 hurricane, yet recon measurements were barely topping 100kts at flight level and the aircraft reports were continuing to indicate a ragged eye.
That all began to change late last night. There were hints of an improved eye structure beginning at around 9PM Saturday. Then, almost suddenly, at about 11:30PM Saturday a much "truer" eye appeared. Since then, it has only become more and more impressive and it's as if a bomb has gone off in the atmosphere. That last recon report indicated a central pressure of 915mb and maximum flight level winds of 144kts. Note that I'm writing this at 7AM EDT Sunday; TPC/NHC in their 5AM EDT discussion referenced the most recent recon report of 935mb! These two reports were just about four hours apart, indicating a rapid pressure drop of 5mb/hr... which also means that Katrina's winds probably haven't spun up all the way yet either.
So, Katrina is intensifying rapidly and she is essentially on track. There has been a slight shift east in the model guidance, but, other than the far east NAM model, the shift is almost negligible. The models are, overall, very consistent and Katrina, having finally begun her turn mid to late Saturday, is on course. So, let's get down to brass tacks...
Current Conditions: As noted, Katrina has intensified incredibly overnight. An eyewall dropsonde around the time of the 915mb pressure report indicate 127kt winds just 1mb above the surface. TPC/NHC put her at 125kts at 5AM, but that was based on an earlier recon report. This later one does not indicate much high winds, implying that, strong as she is, Katrina still has some spinning up to do... I expect the next recon to be even more impressive. But, it is fair to say, given the 127kt report and the fact that that was reported almost two hours ago as I write this, Katrina is up to at least 130kts now. That is a mere 6kts shy of Category 5 strength. If she spins up in accordance with her pressure (915mb), that typically yield about a 145 to 150kt hurricane... well up above the Category 5 threshold. Even JUST as I write this a brand new recon report has come in with 153kt flight level winds and a 910mb pressure. Doing the conversion to surface winds, 153kts would yield 135-140kts... closer to 140kts. Meanwhile, 910mb would nominally support 150kts, so Katrina may well now be a Category 5 and might not quite be done strengthening yet. Incredible. As for her motion, using the last few recon fixes for a 6-hour motion... Katrina has been moving at 304-degrees at 10kts. So, she's almost come around to straight northwest... a considerable amount of turning from 24 hours ago.
Model Discussion: Other than the NAM we have excellent model agreement focused on a landfall between 89 and 90W longitude... a few are a shade east of 89W. That puts the focus basically between Pascagoula and New Orleans. Obviously, Katrina is very large and very strong, so a wide area will get whacked good. But in terms of the utter devestation from a Category 4 or 5 hurricane (whatever she is when she comes ashore... probably no less than a four), this landfall location is important. Folks about 20-30 miles either side of it, particularly on the east side, are the ones who will feel the brunt of Katrina. At any rate, given the agreement, we'll just run through the solutions fairly quickly...
Let's start with the outlier... The 06Z NAM is quite slow, which allows the trough more time to come east and, therefore, turns Katrina harder to the east. It has landfall Monday evening near or just west of Pensacola, FL. The 00Z NGM has a Monday AM "landfall" near Buras, LA... I put landfall in quotes because it's quite marshy in that area and that part of LA (Plaquemines Parish) is a peninsula, so... given the motion, Katrina might make come offshore (barely) and make a second landfall around Biloxi or Gulfport, MS. The 06Z GFS has landfall Monday morning near Grand Isle, LA. The 06Z NOGAPS is identical... Grand Isle, Monday morning. The 00Z RGEM is also nearly identical; it may be just the slightest hint east of Grand Isle at landfall. The 00Z GGEM is a bit of an outlier to the east, but not as bad as the NAM. It has landfall near Mobile, AL Monday morning. The 00Z UKMET actually matches that but may even be a touch east of Mobile Monday morning. The 00Z ECMWF is more in line with the model majority... landfall near Grand Isle, LA on Monday morning. The 06Z GFDL is a touch slow and east, showing landfall near Biloxi around midday Monday, but, like the NGM, it just clips the tip of Plaquemines Parish, LA. Incidentally, it has Katrina weakening from this point forward and "only" a Category 3 at landfall. And its handling of her in the immediate short term was quite good... dropping her pressure to 908mb and increasing her wind to 131kts by 12Z Sunday. So, perhaps this provides some glimmer of hope that Katrina will collapse to Category 3... though even that is quite impressive... by landfall.
My thinking: Given Katrina's notable turning within the past 24hrs and the model shift east, I will also shift my forecast east just a bit. I had been aiming towards Houma, LA. I will now aim towards Buras, LA. I'm going to go a bit east of Grand Isle, quite frankly, just in deference to the more eastern model solutions. Most of those models do not seem trustworthy. For example, I don't buy the NAM's slow motion, given Katrina's steady 9-10kt forward speed. Also, the GGEM runs very similar in terms of its physics to the RGEM, but I'm more inclined to buy into the regional model solution (RGEM), which is further west. My real concern is the UKMET... one of the only models to "see" the southward turn... which is well to the east towards Mobile, while most of the other models have also shaded east, just to a much lesser degree. So, I'm not going to push my track all the way out east towards Mobile or Pensacola, but I will nudge it east of the model majority, which aims at Grand Isle. Landfall timing pretty clearly seems to be Monday morning... about 8-10AM local time. Of course, Katrina is large, so major impact will be felt long before then. In fact, preparations across the northern Gulf should be rushed to immediate completion this morning. Scattered showers associated with Katrina are already approaching the coast and "significant" weather will reach the coast this evening.
Katrina's intensity at landfall is a question mark. The GFDL holds out hope that she could crumble to a mere Category 3 by landfall. While that is still a major storm with rather severe impacts, it pales in comparison to what a Category 5 would bring. Given that the latest recon dropsonde reported near-surface winds a bit higher than the GFDL shows, and that is supported with a flight level to surface conversion, we can at least say that the GFDL's peak is a bit too low. Given its higher starting point doesn't necessarily mean it'll be equally off at landfall, but since it could be, it would be prudent to round the GFDL up to get its best estimate. That would be 110kts at landfall. SHIPS, on the other hand, shows Katrina intensifying right up to landfall, striking as a 140kt Category 5 hurricane. My thinking is that some weakening will take place as shear increases in advance of the trough. However, typically that type of shear is slow to impact a storm, especially a major one whose outflow can help protect it from the battering winds of shear. So, I'm going to call for Katrina to peak soon, at about 145kts, then drop her to 130kts by landfall.
Note that as I finish this up, TPC/NHC has, indeed, officially upgraded Katrina to a Category 5 hurricane. This is not at all unexpected given the above discussion of the most recent recon reports. They officially put her at 160mph, which equates to about 140kts, which absolutely seems reasonable. With such a powerful hurricane approaching, all interests throughout the Louisiana, Mississippi and Alabama coastline need to complete their preparations quickly. And folks in evacuation areas should already be gone, or headed to shelters. Even folks in the western portion of the Florida Panhandle should be taking precautions. There is an outside chance, if one believe the easternmost model solutions, of a direct hit there (though it's not what I'm forecasting), and even barring that, this is a very sizable hurricane and you're on the stronger, eastern side of it. But, right now, SE LA, MS and AL are the focal points.