ATL GUSTAV: Tropical Depression - Discussion

[Enzo Aquarius]

http://philadelphiaweather.blogspot.com/2008/08/tv-imagery-from-new-orleans-tv.html

Updated imagery from the 8 ET hour from Fox 8 and WDSU in New Orleans.

Starting to look pretty nasty in the area by the look of those cloud photos. My prayers go out to all in the path of Gustav.

[KWT]

I'm tending to agree with the NHC, this may well be able to get to 110kts if the eyewall can close back off again and the small eye can stay clear without another big burst clouding it over again.

[Portastorm]

I guess it might be mentioned now that the strongest forecast landfall for Gustav was when he was cat-5 south of Cuba.

That's only 15 kts above where he is now.

And now Fox suggests that Gustav may hit near Lake Charles, or even on the Texas coast. I think that's a ridiculous assertion to make based upon one particular new model run.

To which "one particular new model run" do you refer?

[Weatherfreak000]

Incredible intensification....absolutely may reach Category 4 now...


I read somewhere back about a West Jog....I don't see that happening. You may perhaps be seeing the extension of the convection and getting confused....the storm seems to have returned to a NW heading after the NNW jog to me.

[wxman57]

No deviation from previous course. I just measured a 2-hr movement toward 302 degrees at 20 kts. Still racing along. That's heading for western Terrebonne parish, just as consensus models are saying.

6-hr movement 303 degrees at 16 kts.

We have recon out there confirming the movement which was NNW from the last drop..just a wobble im sure but Im gonna agree with recon

You have to remember that the center is quite a large area 20-25 miles across now. You can't judge movement from two VDMs.

[cpdaman]

I'm afraid I have to call out the SPC here on the gross lack of a tornado watch.

Should there be anyone there to worry about it?

i seriously hope not, from the interviews i watched on tv , seemed more people were getting out. Some mentioned not just fear of the winds, but fear of the lawlessness and gun happy blackwater peeps afterward, would NOT be around for the storm or the aftermath, no way no how.

[soonertwister]

TWC's Jim Cantore figures to hunker down in Houma for the blow.

I think that could be a mistake he might not want to make.

[Dean4Storms]

I'm afraid I have to call out the SPC here on the gross lack of a tornado watch.

Should there be anyone there to worry about it?

Uh, yes in Baton Rouge there will be people there.

[AJC3]

The best analysis I can find is from CIMSS, and it clearly shows at least 20 kts from the center northward. http://cimss.ssec.wisc.edu/tropic/real- ... g8shr.html

Something just hit me - if the shear is 20 knots from the south and the hurricane is moving NW at 17 knots would that not mean, and I'm not good at trigonometry, something likely "only" about 10 knots of effective shear?

Shear doesn't work that way... it's a difference between winds at different levels. 20 kts of shear is still 20 kts of shear, whether the difference is between an 80 kt wind aloft and a 60 kt wind below, or the difference between a 30 kt wind aloft, and a 10 kt wind below, and so on.

A hurricane moves with the steering flow, which is some weighted average of winds over a depth of the atmosphere, and is different for every system. A hurricane that is stationary and getting sheared from the south, if it started to move north, would experience less shear, not because it was moving "with" the shear, but because the low-level environmental winds have begun to line up more with the upper-level winds, both starting to move the hurricane north, and decreasing the shear at the same time.

I hope that makes sense, and any other met on here who wants to chime in with corrections or additions, please do so..

Let me just expand upon what Dan said...hopefully I don't confuse anyone.

Most shear computations that I've seen on line compute the difference between the 850MB wind and 250MB wind to compute the amount of upper tropospheric shear. Some use layers centered about each level. It's not just one windspeed minus another windspeed....it's a vector difference. For those who have not taken vector math, this may help...

http://www.wunderground.com/education/shear.asp

One can assume that if the storm motion is reasonably close to the magnitude and direction of the 850MB wind vector, then the shear computed is probably accurate.

[Sanibel]

Sanibel, when you say OFFICIAL, you better post a link or say IMHO...I havent seen, heard or read anything of that nature where someone says LAFAYETTE will be the OFFICIAL landfall.

The NHC track goes right over the top of it.

[Stormcenter]

I guess it might be mentioned now that the strongest forecast landfall for Gustav was when he was cat-5 south of Cuba.

That's only 15 kts above where he is now.

And now Fox suggests that Gustav may hit near Lake Charles, or even on the Texas coast. I think that's a ridiculous assertion to make based upon one particular new model run.

To which "one particular new model run" do you refer?

What model?!?!?!?

[TCmet]

No doubt Gus is strengthening on approach. Obviously a delayed reaction from the loop current.

We saw the same thing - delayed intensification - to a lesser degree just before the Cuba landfalls. Also - there was some "delayed weakening" after the Cuba passage. The delayed strengthening now is perhaps a function of the fast forward speed.

[Weatherfreak000]

No deviation from previous course. I just measured a 2-hr movement toward 302 degrees at 20 kts. Still racing along. That's heading for western Terrebonne parish, just as consensus models are saying.

6-hr movement 303 degrees at 16 kts.

We have recon out there confirming the movement which was NNW from the last drop..just a wobble im sure but Im gonna agree with recon

You have to remember that the center is quite a large area 20-25 miles across now. You can't judge movement from two VDMs.

No offense....but what are you talking about? Please explain.

[soonertwister]

I guess it might be mentioned now that the strongest forecast landfall for Gustav was when he was cat-5 south of Cuba.

That's only 15 kts above where he is now.

And now Fox suggests that Gustav may hit near Lake Charles, or even on the Texas coast. I think that's a ridiculous assertion to make based upon one particular new model run.

To which "one particular new model run" do you refer?

They couldn't be bothered with details like that, being such great weathermen. Early today a talking head said that Katrina was the 3rd strongest US hurricane at landfall, and Gustav was problably going to be the strongest ever.

That's the kind of crap you get when you aren't playing attention to NHC.

[Enzo Aquarius]

I'm afraid I have to call out the SPC here on the gross lack of a tornado watch.

Should there be anyone there to worry about it?

Uh, yes in Baton Rouge there will be people there.

Wasn't the main evacuation zone namely the New Orleans area anyways? A Tornado Watch would allow citizens to know that tornadoes are possible rather than waiting for a *BAM!* Tornado Warning and have to rush to prepare.

[Dean4Storms]

TWC's Jim Cantore figures to hunker down in Houma for the blow.

I think that could be a mistake he might not want to make.

He has never been through an eye of a hurricane so he picked one heckuva one to see the sights!

[CajunMama]

Sanibel, when you say OFFICIAL, you better post a link or say IMHO...I havent seen, heard or read anything of that nature where someone says LAFAYETTE will be the OFFICIAL landfall.

The NHC track goes right over the top of it.

Lafayette can't be "official" landfall. We're not directly on the coast.

[Houstonia]

Just wondering if someone can explain why the hurricane warning has been extended west...

thanks!

http://forecast.weather.gov/wwamap/wwat ... %20warning

HURRICANE GUSTAV LOCAL STATEMENT
NATIONAL WEATHER SERVICE LAKE CHARLES LA
633 PM CDT SUN AUG 31 2008

...HURRICANE WARNING EXTENDED WEST TO JUST EAST OF HIGH ISLAND...

.AT 400 PM CDT...THE CENTER OF HURRICANE GUSTAV WAS LOCATED NEAR
LATITUDE 26.4 NORTH...LONGITUDE 87.3 WEST...OR ABOUT 215 MILES
SOUTH- SOUTHEAST OF THE MOUTH OF THE MISSISSIPPI RIVER.

[Texashawk]

I guess it might be mentioned now that the strongest forecast landfall for Gustav was when he was cat-5 south of Cuba.

That's only 15 kts above where he is now.

And now Fox suggests that Gustav may hit near Lake Charles, or even on the Texas coast. I think that's a ridiculous assertion to make based upon one particular new model run.

That would be a disaster if that happened, since we (Houston) have basically done nothing in the way of evac and it's way, way, way, way too late now.

[ekal]

I'm afraid I have to call out the SPC here on the gross lack of a tornado watch.

Should there be anyone there to worry about it?

Uh, yes in Baton Rouge there will be people there.

Unfortunately, even New Orleans is probably not 100% evacuated. There are people who have stayed for whatever reason (or lack thereof). I have not heard any official estimates, but I would be surprised if the official evac percentage is higher than 90-95%.

Granted, that 5-10% probably is not waiting for the SPC to issue a watch.