8/23/05 FCST: Hurricane Katrina

[Kevin Scharfenberg]

Aside from the eyewall replacement cycle, it seems so far the hurricane has had wind speeds lighter than expected for such a low central pressure. It's a huge storm: the convection has extended out so far from the center that it can't develop as tight a pressure gradient as usual. However, in the last hour or so the convection appears on satellite to be consolidating a little closer to the center, so we may see the pressure gradient tighten and the recon wind reports increase. I expect a solid cat 4 storm by noon tomorrow (GFDL showed a borderline cat 5 storm).

BTW, the mayor of N.O. just told a local TV station (watching it now via streaming video) that he cannot call a mandatory evacuation for "legal reasons". :roll:

 

[Sam Sagnella]

I may be eating my words by this time tomorrow, but as dangerous hurricane Katrina continues to strengthen tonight (pressure down to 936mb at 0326z and stadium effect visible in satellite images at 0345z), it is not inconceivable that this could become one of the first annular hurricanes in recent GoM history. An annular hurricane is defined as containing one and only one ring of deep convection surrounding a large eye and maintains this state for at least three hours. One trait associated with these hurricanes is their 'invincibility' or relative lack of intensity change; with Katrina becoming Cat 4/Cat 5 tomorrow, it will likely maintain that ferocious intensity until landfall if the annular characteristics become prevalent.

With Max Mayfield phoning the Mayor of New Orleans earlier this evening and warning him that his city must be evacuated, this worst-case scenario is seeming more likely by the hour. New Orleans is one of the poorer metropolitan areas in the country with 100,000 people without the means to evacuate; with less than 24h before TS force winds buffet the area, there is NO WAY to evacuate the city in time and I truly fear that people will be stuck on highways during this violent hurricane. If this does unfold as is currently forecast, many residents of NOLA may not live to see the first of September. I pray that I'm wrong.

 

[Tim Vasquez]

We're running the familiar hurricane maps again:
http://www.stormtrack.org/special/

This time important oil terminals are marked as this could have a major impact on the oil markets. We'll go in with closer maps tomorrow night.

Tim

 

[Bob Schafer]

I have three reasons for some optimism:

First is the latest GFS run putting landfall east of New Orleans:

http://www.nco.ncep.noaa.gov/pmb/nwprod/an...fs_slp_048m.gif

as well as the NAM (although NAM is a poor model for 'canes)

Secondly, there is some pretty dry air (evidenced by wv imagery) between Katrina and LA, to maybe help keep this SOB in check.

Lastly, the timing seems about right for there to be another ERC just prior to landfall.

Keeping fingers crossed.....

Bob

 

[Alex Lamers]

FoxNews just had Governor Blanco from Louisiana on and she said that Max Mayfield talked to her and that he was "Extremely worried" about the city of New Orleans. She said that they are trying to evacuate as many people as possible but that TOO MANY PEOPLE ARE NOT HEEDING THE WARNING. President Bush has apaprarently declared a pre-hurricane state of emergency which has not occurred in years according to FEMA officials. She then went on to say that their wetlands have eroded and that now there's not much to stop a bad storm from severely impacting the city. She then went on to try and warn the people to get out of the way but of course Fox News needed to get their commercials in so they cut her off :roll:

...Alex Lamers...

 

[Robert Dewey]

Originally posted by Kevin Scharfenberg
Aside from the eyewall replacement cycle, it seems so far the hurricane has had wind speeds lighter than expected for such a low central pressure. It's a huge storm: the convection has extended out so far from the center that it can't develop as tight a pressure gradient as usual. However, in the last hour or so the convection appears on satellite to be consolidating a little closer to the center, so we may see the pressure gradient tighten and the recon wind reports increase. I expect a solid cat 4 storm by noon tomorrow (GFDL showed a borderline cat 5 storm).

BTW, the mayor of N.O. just told a local TV station (watching it now via streaming video) that he cannot call a mandatory evacuation for \"legal reasons\". :roll:

This isn't scientific or anything (I don't study hurricanes), but it often seems that when a hurricane deepens rather rapidly, the increase in SFC winds usually lags a little bit. For instance, the hurricane will deepen several millibars, then the convection will explode, and finally the wind speeds will increase several hours later...

 

[Jeff Snyder]

Wouldn't a hit to the immediate east of N.O. be almost as bad as a hit to the immediate west of the city? Typically the right-forward quadrant is worst given that it contains onshore flow (so winds don't experience frictional effects from the land and the waves are considerably larger). However, I read that, in N.O., a Cat 3+ northerly wind would push Lake Ponch. over the levee and flood the city anyway. It probably won't be AS bad as it would be if the hurricane landfalls immediately west of the city, but it certainly won't spare the city too much. In addition, given the approach from the south, the easterly winds to the north (ahead of) the storm will literally push the waters into Lake Ponch, only to end up in downtown N.O. when the winds switch to the north. Certainly better than the storm hitting directly west of the city, but catastrophic nonetheless.

 

[Justin Bailey]

K

it almost seems like this thing is the perfect hurricane, with nothing to weaken it. it appears that its only option is to strengthen more and more. everybody is talking about the wind. but what about the rain. there are places that could see rainfall ammounts possible close to 30" if the slow movement persists. and also once it gets up into my neck of the woods, Nashville, it is forcasted to put down 7-10" with locally higher ammounts and still have sustained winds of 45 mph with higher gusts. there will be widespread flooding from the gulf coast to new england. that alone will do alot of damage and probably cause many more casualties.

 

[Brandon Clement]

Looking at the Dvorak and IR on satellite Katrina is about to really start showing off. It has been quite a show watching each new frame come in and I would expect the winds in the next update to jump to 130-140. I just hope the trough picks her up a little bit quicker than expected. I hate to wish Katrina on the Ms/Al gulf coast, but it would save a lot of lives if she stays away from La (especially Nola and the north shore of lake Ponchatrain). I will be watching closely and will head out if it does look like the northern gulf coast is going to get hit, if not I will have to sit this one out since I don't feel safe enough in a category 4 or 5 in south La.

I was listining to a WWl 870am out of NO and they had a surveyor that has been shooting many of the levees on for an interview. The surveyor was saying how the Levees were built to withstand a low cat 3 and that many places of the levees have been sinking over the years (as much as 3 meters in some places) and he does not think they would hold up on a direct hit for any hurricane stronger than a moderate cat 2. So even if she does continue the trend and does weaken just before landfall it could still be a very dangerous situation.

 

[Alex Lamers]

Originally posted by rdewey+--><div class='quotetop'>QUOTE(rdewey)</div>

<!--QuoteBegin-Kevin Scharfenberg

Aside from the eyewall replacement cycle, it seems so far the hurricane has had wind speeds lighter than expected for such a low central pressure. It's a huge storm: the convection has extended out so far from the center that it can't develop as tight a pressure gradient as usual. However, in the last hour or so the convection appears on satellite to be consolidating a little closer to the center, so we may see the pressure gradient tighten and the recon wind reports increase. I expect a solid cat 4 storm by noon tomorrow (GFDL showed a borderline cat 5 storm).

BTW, the mayor of N.O. just told a local TV station (watching it now via streaming video) that he cannot call a mandatory evacuation for \"legal reasons\". :roll:

This isn't scientific or anything (I don't study hurricanes), but it often seems that when a hurricane deepens rather rapidly, the increase in SFC winds usually lags a little bit. For instance, the hurricane will deepen several millibars, then the convection will explode, and finally the wind speeds will increase several hours later...[/b]

It is the same way with wake lows. It is (correct me if I am wrong) a general rule of thumb in meteorology that it takes winds several hours to respond to mesoscale changes in pressure. Thus I believe you would be correct

A couple more points...

1) A landfall like the GFS/GFDL/UKMET...etc etc are predicting to the east of New Orleans by a little bit is the WORST possible track because east-southeast winds would shove the gulf (quite literally) into Lake Ponchatrain north of the city and then as the eye passed...northerly winds would dump that into the saucer that is NO.

2) Water temperatures south of the New Orleans area are EXTREMELY warm and should provide the necessary energy to keep this from choking just before the coast.

The ONLY thing that could kill this just about would be an ERC immediately before landfall but it would still be a major hurricane and any way you slice it...someone is gonna get clobbered.

(My source on that one comment was from some other board and a person apparently in that area?? not sure if its credible but I do know the mayor was on the phone with NHC)

...Alex Lamers...

 

[Robert Dewey]

I'm just keepin my eye on the IR satellite and WV loops. That little bit of dry air on the WV loop looks like a result of descending air around the fringe of the hurricane, and that trough over the central US doesn't look like it's moving fast enough. The IR still shows this thing heading more west, so unless it makes a strong jog to the north, I think New Orleans is still in great danger. The GFDL model still has a track right over New Orleans, the UKMET is a bit further east, more in line with the GFS. Still, it's a powerful hurricane and will do some major destruction no matter where it hits.

I just hope people along other parts of the coast aren't thinking "no need to worry, it's hitting New Orleans and not us" - Cuz if it DOES jog more to the east, it will hit those folks by surprise.

 

[Jeff Snyder]

Re: K

Originally posted by Justin Bailey
it almost seems like this thing is the perfect hurricane, with nothing to weaken it. it appears that its only option is to strengthen more and more.

It appears that way, but one thing that's been learned in the past is that we can never perfectly forecast hurricanes (especially intensity)! There have been many hurricanes that looked like they'd strengthen rapidly, yet they fall apart. Heck, nobody anticipated that Ivan would rapidly weaken last year before it made landfall. The dry air around the hurricane could get wrapped into the circulation and, if it made it to the eye (which is what happened to Ivan), could result in a rapid weakening phase. Yes, current model guidance does not suggest that there will be inhibiting factors through landfall, but hurricane forecasting is NEVER a given. The track forecast is particularly difficult in this case since it depends entirely on the rate of curvature. It'd be a little easier if the environment was more static and the track was forecast to be straight. In this case, however, with the dynamic /changing synoptic environment, a slight increase or decrease in the rate of change in direction could result in very different landfall.

 

[Morgan Palmer]

Latest ob at 12:06 shows 141mph FL winds, which translates to the 125 or so at the surface. Unfortunately, we're in an eclipse period on satellite, but no matter. The storm is quickly becoming one of the most impressive looking ones I've ever seen.

Also, now looking at the WV loop to around midnight, it looks like we're able to pick out now a bit of a weakness to the east of the Texas trof. And, of course, that means the runway lights have been turned on for the middle to southeastern LA coast. At least that's what I'm seeing.

There's no way, IMO that this thing can't go ahead and strengthen. Drawing a parallel, I don't think I've ever heard a definitive reason why Lili died just offshore. I was there at the time and it was a huge break for the Lafayette/Cameron area. I know "gut" doesn't mean a thing when it comes to tropical systems, though with the unusual history of Katrina (causing a lot of damage as a cat 1), I am beginning to think that I'd be packing up the truck, the dogs, and maybe the aquarium fish right about now if I was in the Orleans metro. Will be interesting to see what the traffic is after people wake up in the morning. Contraflow is in effect on north and west bound roadways. Probably will pay off, since I also have a feeling that people really are going to take this one seriously.

 

[MClarkson]

NO is not the only vulnerable location. Biloxi has all those casinos right on the water and Mobile bay would channel the surge right up into Mobile.

NO is the most vulnerable but this storm has to go just to the west of somewhere.

And like Jeff said, just to the east of New Orleans could still submerge the city.

 

[Brandon Clement]

Wouldn't a hit to the immediate east of N.O. be almost as bad as a hit to the immediate west of the city? Typically the right-forward quadrant is worst given that it contains onshore flow (so winds don't experience frictional effects from the land and the waves are considerably larger). However, I read that, in N.O., a Cat 3+ northerly wind would push Lake Ponch. over the levee and flood the city anyway. It probably won't be AS bad as it would be if the hurricane landfalls immediately west of the city, but it certainly won't spare the city too much. In addition, given the approach from the south, the easterly winds to the north (ahead of) the storm will literally push the waters into Lake Ponch, only to end up in downtown N.O. when the winds switch to the north. Certainly better than the storm hitting directly west of the city, but catastrophic nonetheless.

It would still be bad just from the rainfall, but surge would be significantly less. I know that in hurricane Georges that there was some flooding and it moved very slowly. The surge in the lake was pretty high, I know on the lake front in Mandeville, La which is on the north side of Lake Ponchatrain that flooding was bad. There were places were the water was 5-6 feet over the retaining wall and had waves on top of that. Luckily the flooding didn't last long becasue it came in quickly and when the winds shifted it pushed it right back out. Georges was not a "near miss" the eye moved in 60 miles east, but passed a little more than 40 miles to the East of the city.

To answer your question, nobody really knows. My best guess is that the water that is pushed up in lake Ponchatrain would devistate the north shore (where there is only a 3 foot retaining wall in some places and nothing in others). When the wind shifts I would think the water would rush right back into the gulf since there would be no resistance, but I sure wouldn't want to be in New Orleans to find out.

If you look at a map of Mandeville/Covington area I-12 runs E-W about 7 miles north of the lake and EOC officials have stated repeatedly over the years that surge would make it as far as I-12 in a category 4 hurricane and could push north of Covington in a strong 5. They issued a mandatory evacation of anything south of 12 and my dad lives about 3/4 of a mile north of the lake and I have witnessed first hand some of the flooding that occurs from a minimal T.S. so it is a very scary thought. Slidell area has major flooding issues from the Pearl River when there is more than 6" of rain, and that city would be wiped out if there was a direct landfall. The surge would be so bad that houses would be under water and the rainfall would cause the Pearl River to add to the problems. The flooding there would last for days if it stayed on the current track. Unfortunatly the problems have been known for a very long time and Louisiana's politics are so backwards that no solution has ever been agreed on. It is going to take a major catastrophe before that ever changes and I hope that Katrina is not the one that does it but it appears that she will.