ATL GUSTAV: Tropical Depression - Discussion

[rtd2]

For those interested, I used the latest recon data to work out it's current trajectory (for the past 98 minutes):

I used 25'51''N, 86'33''W to 26'2''N, 86'54'' and used the FCC website to account for differences in heading dependent upon latitude to get a precise value of:

300.3 degrees at 21.9 knots.
Note that the heading for the previous six hours was an average of 315 degrees at 15 knots.

So it has sped up a little and for the past 1.5 hours has been heading on a more westerly track than prior.

Sped up a LITTLE? if those numbers were accurate it would push landfall WAY up....

Not necessarily. By going on a more westerly path, it would delay landfall substantially. I extrapolated the past 1 hour and a half movement, and it took me to west of the Texas/Louisiana border, an unlikely (but not impossible) event. You have to consider much longer time periods for landfall projections. It will be interesting to examine the next couple recon reports to look at the average.

RECON

B. Center Fix Coordinates: 26°04'N 86°56'W (26.0667N 86.9333W) (View map)
B. Center Fix Location: 303 miles (487 km) to the S (177°) from Pensacola, FL, USA.

[vbhoutex]

For those interested, I used the latest recon data to work out it's current trajectory (for the past 98 minutes):

I used 25'51''N, 86'33''W to 26'2''N, 86'54'' and used the FCC website to account for differences in heading dependent upon latitude to get a precise value of:

300.3 degrees at 21.9 knots.

Note that the heading for the previous six hours was an average of 315 degrees at 15 knots.

So it has sped up a little and for the past 1.5 hours has been heading on a more westerly track than prior.

Are you sure of the speed calculation? That seems high to me, especially since Gustav is probably starting push up against the ridge and slow down some(though probably not a lot). The heading is believable and if it holds true will miss the NHC points to the west somewhat. I certainly don't have the tools to check your work, but just expressing my concerns. IE if it held on your heading we could be talking a SW LA landfall vs. the current projected landfall. Thanks for you work and posting this for discussion.

[wxman57]

A ship 150 nm due North of Gustav reported 60 kt sustained winds and 46 foot waves a little over a half hour ago.



http://www.ndbc.noaa.gov/radial_search.php?storm=at2

Ummmm....46 foot waves? WOW! Were any waves like this recorded for Katrina. This seems very high.

I believe Ivan had near 100 foot wave heights... no surprise since it made it from the Caribbean to GOM without land interaction.

That was almost certainly a poor wave estimate. The NOAA buoy just east of the center reported only 34 ft waves. And other wind observations near the ship were 30-40 kts. No way it had a 46 ft significant wave. And Ivan's significant waves were 50-55 feet, not 100 feet. There was an estimate of the highest likely wave of 100 feet. A "significant wave", by the way, is the highest 1/3 of all waves. Maximum waves are typically 1.5 times the significant wave.

[superfly]

Looks better on visible, but IR is still a mess. The MLC seems to be displaced 30 miles north of the LLC, from looking at satellite and what recon is saying.

[HarlequinBoy]

How long until landfall? My cousin and his wife in Schriever, Louisiana haven't evacuated yet. They were going to wait until around dusk today to decide.

[RL3AO]

Movement between VDMs was 304 at 15.2 kt.

[HouTXmetro]

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm6.html

Ridge is really feeling in.

[wxman57]

For those interested, I used the latest recon data to work out it's current trajectory (for the past 98 minutes):

I used 25'51''N, 86'33''W to 26'2''N, 86'54'' and used the FCC website to account for differences in heading dependent upon latitude to get a precise value of:

300.3 degrees at 21.9 knots.

Note that the heading for the previous six hours was an average of 315 degrees at 15 knots.

So it has sped up a little and for the past 1.5 hours has been heading on a more westerly track than prior.

Are you sure of the speed calculation? That seems high to me, especially since Gustav is probably starting push up against the ridge and slow down some(though probably not a lot). The heading is believable and if it holds true will miss the NHC points to the west somewhat. I certainly don't have the tools to check your work, but just expressing my concerns. IE if it held on your heading we could be talking a SW LA landfall vs. the current projected landfall. Thanks for you work and posting this for discussion.

I just measured a 2 hour movement to 301 degrees at 19 kts. I just put my mouse cursor in the center of the eye at 1745Z and advanced the satellite loop 2 hours forward and read a distance of 38nm. Landfall by 9am tomorrow, maybe earlier. That's allowing for a significant slow-down.

[Brent]

How long until landfall? My cousin and his wife in Schriever, Louisiana haven't evacuated yet. They were going to wait until around dusk today to decide.

Probably about 14-18 hours.

[superfly]

How long until landfall? My cousin and his wife in Schriever, Louisiana haven't evacuated yet. They were going to wait until around dusk today to decide.

18 hours or so, but conditions will start to deteriorate long before that.

[hiflyer]

Anyone know what the winds are here in the Tampa Bay area? Specifically along the beach of Pinellas County. Both peak wind gust and sustained. I'm surprised at how strong they've been.

The winds surprised me, too. I'm in NW Hillsborough County. I just checked the weather station in my backyard, and it had recorded a 55 mph gust.

Yeah, we've got some branches and limbs down. What are we 200 miles away?

Latest hourly showing gusts 30-35 kts on the coast around TPA....ouch!
http://www.srh.noaa.gov/tbw/html/tbw/Ta ... ather.htm#

[KWT]

Problem is wxman57 its not really a very well defined eye in terms of the convection from the eyewlal overspilling into the eye, recon suggests a slower motion then that as well over a slightly shorter timeframe granted.

[Laser3003]

I feel like our time is due in the Tampa area. There are a lot of storms out there.
I'm worried, thank god this one missed us.

[wxman57]

Problem is wxman57 its not really a very well defined eye in terms of the convection from the eyewlal overspilling into the eye, recon suggests a slower motion then that as well over a slightly shorter timeframe granted.

I used the same relative point from one image to another. Doesn't matter if I'm seeing the LLC or not. The 1pm position was 1-2 hours ahead of the 10am forecast.

[Shoshana]

How long until landfall? My cousin and his wife in Schriever, Louisiana haven't evacuated yet. They were going to wait until around dusk today to decide.

Eep.

Somewhere between late tomorrow morning and midafternoon is what I'm reading and seeing online and on tv. I'd think the NHC would have the latest info.

It's going to be rough even before official landfall... I suggest that you urge him to leave ASAP.

[vaffie]

For those interested, I used the latest recon data to work out it's current trajectory (for the past 98 minutes):

I used 25'51''N, 86'33''W to 26'2''N, 86'54'' and used the FCC website to account for differences in heading dependent upon latitude to get a precise value of:

300.3 degrees at 21.9 knots.

Note that the heading for the previous six hours was an average of 315 degrees at 15 knots.

So it has sped up a little and for the past 1.5 hours has been heading on a more westerly track than prior.

Are you sure of the speed calculation? That seems high to me, especially since Gustav is probably starting push up against the ridge and slow down some(though probably not a lot). The heading is believable and if it holds true will miss the NHC points to the west somewhat. I certainly don't have the tools to check your work, but just expressing my concerns. IE if it held on your heading we could be talking a SW LA landfall vs. the current projected landfall. Thanks for you work and posting this for discussion.

You're right, my speed was off because I forgot that it was in 98 minutes. Corrected, it's now 300.3 degrees at 13.5 knots, so it has slowed down slightly and turned to the west somewhat.

[tolakram]

This buoy east of center.

http://www.ndbc.noaa.gov/station_page.php?station=42003

[Windy]

How long until landfall? My cousin and his wife in Schriever, Louisiana haven't evacuated yet. They were going to wait until around dusk today to decide.

If they don't leave soon, they won't be able to. The storm will be upon them by early Monday morning; hurricane force winds may arrive before sunrise. You ever try to drive on a road in 80 mph winds? As a storm chaser, I usually just turn my car into the wind at that point. Your cousin is a braver man than I. Braver or dumber, I dunno.

[KWT]

18 hours or so, but conditions will start to deteriorate long before that.

Yep the thing is with such a large system TS winds will probably be coming ashore long before the eye itself comes onshore.

wxman57, yeah thats fair enough, it doesn't matter anyway because recon data shows its slowed down from the faster motion about an hour ago or so.

[HouTXmetro]

Anyone know what the winds are here in the Tampa Bay area? Specifically along the beach of Pinellas County. Both peak wind gust and sustained. I'm surprised at how strong they've been.

The winds surprised me, too. I'm in NW Hillsborough County. I just checked the weather station in my backyard, and it had recorded a 55 mph gust.

Yeah, we've got some branches and limbs down. What are we 200 miles away?

Latest hourly showing gusts 30-35 kts on the coast around TPA....ouch!
http://www.srh.noaa.gov/tbw/html/tbw/Ta ... ather.htm#

Ridge is building near Tampa so the Pressure Gradient is really tightening up. Probably why the winds are increasing.

http://cimss.ssec.wisc.edu/tropic/real- ... 8dlm6.html