8/23/05 FCST: Hurricane Katrina

[MClarkson]

Advisories for the feature near the southern bahamas will begin at 5pm.

Looking at the GFS, and satellite derived flow, winds at upper levels are out of the east. Winds at lower levels appear to be a little more southeast, the GFS has generally easterly winds at all levels in the ~2 day range. ECMWF has something similar. This should drive the storm towards florida.

it looks like shear will be light. Right now there is some strong 30kt+ upper level winds across south florida but GFS ECMWF UKMET all decrease this feature. The storm should have a chance to intensify a little, but I dont think it will have enough time to become particularly strong, unless it misses florida to the south and gets into the gulf. The GFS currently has the center of low just off SW florida in 2 days.

 

[Mark Farnik]

I believe that T.D. 12 will likely become Katrina with what is likely T.D. 13 out in the far eastern Atlantic to be designated Lee. T.D. 12 is rapidly getting it's act together and Tropical Storm Katrina could be gracing us with her prescence by the 5 A.M. advisory tomorrow morning. One thing I have noticed is that she has a lot, and I mean a lot, of convection over a large area, a couple hundred miles in each direction. If all the convection around her gets pulled in we could be looking at a very large tropical system for the first time this season. It doesn't have the compact appearance Dennis and Emily did in their formative stages, so that leads me to tha particular conclusion. If the current forecast path verifies and with the SST's being as warm as they are, we could be looking at a strong hurricane headed in the general direction of southern Louisiana by the end of the weekend.

 

[Brett Adair]

Well, looks like Katrina will be visiting my neck of the woods if several models are correct. I expect a landfall around the MS/AL/FL coastlines once again as the ridge builds. I believe we will see a general WNW motion until it reaches the Cntrl GoM and then more of a NW motion and possibly another Dennis with a northerly jog near the coastline. Difference this time, there is no cool water eddy to work in a weakening trend. This one looks to strengthen all the way in. Also, upper level flow over the SE region is weak. All in all, no matter where this thing makes landfall, it is going to wreak havoc flooding wise.

 

[Doug_Kiesling]

Well, looks like Katrina will be visiting my neck of the woods if several models are correct. I expect a landfall around the MS/AL/FL coastlines once again as the ridge builds.

Yeah, that's if it rebuilds and if it gets over southern Florida in pretty good shape.

I was on standby to head to south Florida this morning but this storm is just not all that. I don't think it will make it to Hurricane status before it makes landfall tonight and into tomorrow. The tropical storms normally gain strenght at night and Katrina really did not pull together as expected overnight. Its very poorly organized right now and not worth the time to go chase in South Florida unless you live within 100 miles of this storm as it makes landfall.

But if you want to get your feet wet with a tropical storm for the first time, this one would be perfect since winds will be barely Cat 1 gust with mainly tropical storm force winds and mainly flooding in south Florida.

My eyes are watching what this thing does once it gets back into the gulf. Worst case, Katrina has time to rebuild then hits Pensacola as a Cat 2.

 

[MClarkson]

If she follows the current gfdl/ukmet and goes slowly into the mid gulf and then north she might have time to restrengthen significantly. Shear is light for the next few days, and waters very warm. However the longer the wait the stronger upper level winds over the extreme northern gulf might be, according to some models. The ECMWF keeps the northern gulf relatively shear free out to 5 days.

But what state will she be in upon reaching the gulf. We'll have to wait and see exactly how much of a bite Florida takes out of the storm. Its moving pretty slow and could spend quite some time overland. There is some mitigation from the everglades, however.

 

[David Wolfson]

I'm impressed by the radar presentation showing K not slowing and trending just south of due west. That, and the forecast models (except for the GFS... stay tuned for the 18Z) rolling the track back west. This is not a good scenario for offshore oil and possibly for New Orleans. Lots of deep, toasty water for K to suck off on her way through the north central GoM.

There also seems to be some nasty, sheared "eye"wall action just off Miami Beach. Tors a definite risk IMHO, FWIW.

 

[Doug_Kiesling]

Lots of deep, toasty water for K to suck off on her way through the north central GoM.

Yeah and what really makes me go hmmmmmm, check out the feeder bands on extended radar that go around the south tip of FL and pulling in energy. And the west track of this storm means that this could really be a player by Monday.

 

[Stuart Robinson]

Katrina has just been upgraded to a CAT1 Hurricane.

 

[Jeff Gammons]

update - Im sitting on Ft Lauderdale BEach attm in a pretty impressive cat 1 hurricane I have been in impressive northeast winds now for over a hour and the surge is moving up to A1A now. Alot of tree debris in the air and power flashes every few mins.

I belive Chris Collura is just north of me and Jim Edds is in Pompno Beach. There are a large amount of people that never left the coast and now trying to leave and getting stuck.

Shes moving so slow I'll have time to have dinner in the eye and then play the eastern quad late this evening.

 

[B Ozanne]

Can we get a now thread going? I'd like to see storm reports, wind data, and some general talk on the action.

This storm is looking like a real Cat 1. It seems like its been awhile since a hurricane has even come close to matching its given intensity.

Reports of 68mph gust at For Lauderdale...movement is still very slow to the west, with some wobbles.

 

[Jeff Snyder]

Some very intense rainfall and accumulations to the southwest of Miama... MIA radar showing storm-total amts up to 21" in areas, so even if it is 2x overestimating, that's still 10-11" of rainfall. Local statements from NHC and MIA NWSFO have indicated that rain gauges have recorded up to 14" so far. The "pivot point" for the heavest precip band appeared to be just to the southwest of MIA, almost directly over the 88D out there. The western eyewall (though ragged on radar) is just beginning to move offshore. I'm relatively impressed that the structure of the storm looks as good as it does given it was a Cat 1 hurricane and has been on land for 6 hours. I guess the abrupt turn to the southwest (as indicated by GFDL and NAM actually the past few runs) has resulted in the least amt of time over land that could be expected given all model output.

0z/12z runs: http://euler.atmos.colostate.edu/~vigh/gui...ntic/early2.png
6z/18z runs: http://euler.atmos.colostate.edu/~vigh/gui...antic/late2.png
0z/12z intensity forecasts: http://euler.atmos.colostate.edu/~vigh/gui.../intensity2.png

The latest 0z model guidance shows that it'll probably begin to move northward in 18 hours and likely impact the FL panhandle. The interesting model in my eyes is the GFDN run (which is the Navy version of the GFDL IIRC), which takes Katrina smack dab into New Orleans. In addition, a look at the intensity forecasts shows that the same model (GFDN) brings Katrina to a 130kt storm... So, if the GFDN verifies, there will be a high-end cat 4 in New ORleans by the end of the weekend. Of course, that model is the left-most model, so it's unlikely to verify (or so consensus would let us believe). The water is plenty warm, and shear shouldn't be a big problem for a couple of days. Then again, residence time over land tends to disrupt the core of hurricanes, and thus lead to delayed strengthening. In addition, evidence of dry air to the north of the storm can be readily seen in satellite and radar observations, as there is very little precip in the northern 1/2 of the storm.

I do think that strengthening storms tends to be more "fierce" than weakening storms of the same advisory strength. I mean, we've seen weakening Cat 2-3 storms come ashore with little verification of the anticipated/advisory winds. Recon reports and observations such as the fact that the cloud tops, per IR imagery, continued to cool well after landfall certainly signifies that this storm was strengthening nicely right up to landfall.

 

[MClarkson]

the only inhibitting factor I see is some dry air at 500 and 700 mb to the north/west of the storm that the gfs has progged for 2-3 days.

Its time to start considering a major hurricane chase for the I10 corridor...


again.

 

[Justin Walker]

The LBAR is joining GFDN in bringing Katrina into New Orleans. The subtropical ridge should start weakening today, letting Katrina begin her northward turn. However, if the trough slows down or digs a little further south before moving eastward, the subtropical ridge could let Kat track a little further west. If this occurs, then we could see all the models jumping westward as a couple of them already have. It will be interesting to watch how this unfolds, she has very warm water and little shear to weaken her. The only weakening factor I see is the dry air that Jeff and MClarkson echoed earlier. Last year, Ivan was in this situation and the dry air that entrained into the storm weakened Ivan right before he made landfall, which prevented Ivan "The Terrible" causing even more damage then what occured. I not saying Kat will be anything like Ivan, Ivan was much stronger. I'm just simple comparing the enviroments.



EDIT: Well, there is the shift of the models west. Watch out New Orleans!

 

[Jeff Snyder]

Yeah, the 12z models shifted westward for the most part, and the NOGAPS joins the GFDN with a landfall near New Orleans... The 12z GFDN still has 130kt landfall intensity... The latest NHC discussion (a "special" statement to include the latest recon and dropsonde data) brings the storm to "near category four" strength by landfall (likely over 110kts). The GFDL has handled the storm pretty well so far, as it was one of the only models to forecast a sharp southwest turn right at the southeastern FL coast. The model also forecast rapid strengthening when it emerged over the Gulf, which seems to be holding pretty well at this time. The dry air to the north of the storm isn't helping any, however.

 

[David Wolfson]

The latest GFS has lined up with the general trend of the models back to the west and puts K as a major hurricane just about on top of New Orleans in three days. Ground truth still shows K chugging along just south of west, very good outflow even to the north, steady intensification, and near-term entry to the high heat content of the central GoM. My forecast is that I've sold some investments for a few days with exposure to a Cat 4 or 5 ripping through the offshore LA fields. FWIW.