danielw
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The 0503Z vortex fix. Pressure 920mb, 35nm eye;winds146kts-NE quad.=flt level wind of 168.1mph, and surface wind of 151.3mph
Actually a met could probably answer that better. But I think they have left for the night. The ATLC high pressure ridge is keeping from making the turn northward. The trough (trof) is acting as a minor roadblock right now, but should turn into a rail for to ride along, or a deflector to limit his westward motion. Frank, you may be better at this one.
Edited by danielw (Mon Sep 13 2004 02:06 AM)
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RevUp
Weather Guru
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At this point, is at an intersection between influences from the ridge and trofs to the north. Generally, tropical cyclones are steered by the ridges south of 20 N, then as they drift north of 20 N, they encounter more trofs and sheer causing them to accelerate northward and eventually transition to extra-tropical systems. is still under more of an easterly flow regime right now, but it looks like that will be changing over the next 2 days.
Continued westward movement to the northern tip of the Yucatan isn't out of the question however. Surface pressures still remain relatively high at Havana and Key West compared to Cozumel and Cancun.
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"Let tomorrow worry about itself. Each day has enough trouble of its own."
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Steve
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scott,
I had it Moss Point to Seaside from early last week.
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Not too often that I disagree with Clark, Mike and Ed on a storm. Latest track is probably about right if not 50-100 miles too far east. I think the bullseye is on the MS/AL coasts, and where the storm goes in (thinking it will be moving NNE at landfall) and 150 miles eastward face the greatest threat. The storm won't be so bad for areas west of landfall as the advancing front should should provide enough of a SW flow to knock out whatever gets cooking when the steering currents relax in the 24-48 hour time period.
Steve
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MF'n Super Bowl Champions
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danielw
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From the 11pm discussion.
HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 90 MILES...150 KM... FROM THE CENTER...AND TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP
TO 200 MILES...325 KM.
In theory. Please correct me if I'm wrong.
Forward movement of 15mph, would give a person in the center of the path 6-12 hours of 65mph or better winds.
And 13-26 hours of 35mph winds or better.
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Clark
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Well, the simple answer to your question is: yes. But that doesn't really say a whole lot.
Early on, the high has more influence. Once the storm reaches the midlatitudes -- or a trough reaches into the tropics, whether the trough actually reaches the tropics or just erodes part of the ridge in the tropics -- the trough patterns tend to take over, leading to a more northward component of motion. Of course, there isn't always a trough to impact a storm's motion...but more often than not, there is.
To date, has been steered by the ridge. Right now, it is rounding the base of that ridge and should soon begin the feel the effects of the trough. In essence, in time, the ridge and trough will "combine" to form a channel for to follow to the north -- and either north-northwest or north-northeast, depending on the sharpness of the trough.
And that will be critical for the final landfall of the storm. North-northwest (~340ish degrees) will take it towards MS/AL. North-northeast (~020 degrees) will take it towards the central FL panhandle.
For effect, let's take a 20 degree difference averaged out from the T+48 hour position, 22.3 N and 85 W. The Gulf coast is roughly at 30 N. Assuming a due north motion, it is 855 or so km to the coast. A 20 degree shift to the left or right results in a 311km -- just under 200mi -- difference in landfall position. If you center this over a landfall point of Ft. Walton Beach from the 11pm advisory, you could see a landfall anywhere from near Mobile, AL to Panacea, FL along the coast. This serves to highlight how crucial the timing and sharpness of the trough that will ultimately pick up is to the ultimate landfall position...as well as shows how difficult track forecasting can be, despite very precise measurements of the track.
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Clark
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Technically, if you assume a radially symmetric (circular) storm and no weakening of the wind field as it goes over land, if you take a direct hit of the storm at the current forward speed (9 mph), you would experience hurricane force winds for 20 hours and tropical storm force winds for a whopping ~44.5 hours. Increase the forward speed to about 18, however, and you can halve both of those times. Thankfully though, the storm is not radially symmetric -- there are breaks in the wind field and it is not entirely circular -- and there will be some weakening of the wind field in all quadrants after landfall, even if part of the storm is still over water.
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Second Shift
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Thanks to all of you guys for the explanation. I had 10 hours of met at the University of Kansas back in the dark ages, but
I realize that doesn't qualify me to be one LOL 
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danielw
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Thanks. Just a hypothetical question in respect to the length of time it would take for the wind to spin up, peak and wind down, over a point. As there is no "perfect storm" I understand the symmetry of the windfields. I found graphics for the question at . Even though they are old tracks.
Had I known Clark, Jason and some of the others were still here, I wouldn't have attempted to answer. They will always be more qualified for those questions.
Edited by danielw (Mon Sep 13 2004 02:49 AM)
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Clark
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No problem -- and truth be told, I thought I was going to bed over an hour ago!
I won't be around much of Monday, so I'll defer to the other mets & hobbiests on the board for the day. I'll be following the storm, however. Should be an interesting day...hopefully we'll know more tomorrow night, but I'm starting to sound like a broken record with those sorts of comments.
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Kal
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I know that wobble-watching can grow tiresome. But given my proximity to the forecast track, I'm watching every jog with the intensity of the media covering a scandalous celebrity trial.
The last few frames (thru 815 UTC) on the IR loop "seem" to be indicating a more northerly component...at least relative to what I've been observing over the past couple of days. I concede my amateur status, so I suppose this could be some sort of optical illusion created by the inner workings of the storm.
Thoughts???
Looks like there is less N movement than I "thought" I saw, but more than there has been. Visuals perhaps exagerrated by the process?
Edited by Kal (Mon Sep 13 2004 06:09 AM)
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AdmittedHacker
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The 5:00 am update is out... and it's time to face the facts! I've read everone's predictions with great interest. But those that still think this thing is going to make landfall along Florida's west coast (Cedar Key??) just aren't seeing the obvious... has persisted to skew west of all predictions by the as well as posters here. The latest forecaster admits that they would have adjusted the latest track even further westward, were it not for previous models.
Once in the GOM the steering currents will be even weaker, giving less reason to expect a dramatic shift in the course... let alone a 100+ degree turn to the right to get back to FL west coast. I just don't see it... Mobile, Biloxi even New Orleans are now in harms way.
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RedingtonBeachGuy
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well, for us in the Tampa Bay area, the new data suggests good news. However, I still worry that may come to a crawl in the GOM and make a sharp hook to the right under that ridge. I don't think Florida is out of it just yet (I am not a weather guru - just a hobbiest stating an opinion).
Opinions?
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GuppieGrouper
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There is a high over Texas that is likely to block a westerward movement and if no steering currents are available, has already been shown to avoid even tiny land masses, let alone massive air pressure. So the truth is that is going to find the hole in the wall to get through. This is why he has taken so long to get North of 20. As for making a turn, hurricanes do it all the time. They are like bumper cars at a carnival, one minute they are going forward the next minute they are turning or backing up. The outflow and inflow are one and the same. Of course it is easy to say that it is pointed in the direction of the Panhandle, unless your parents live there and are senior citizens with your father dependent on oxygen. But I am going to be honest here folks, I am officially wishcasting this thing my way so that my parents in the panhandle do not have to deal with this.
Edited by GuppieGrouper (Mon Sep 13 2004 05:40 AM)
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danielw
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Don't let your guard down. This is just a discussion. NOT a forecast!!
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NEW ORLEANS/BATON ROUGE LA
300 AM CDT MON SEP 13 2004
...MODEL SOLUTIONS DIFFER WITH THE PATH OF THIS MORNING BUT HAVE A GENERAL CONCENSUS TO BRING IT TOWARD THE WESTERN FLA PAN AREA. ON THE OTHER HAND THE ...ETA...CANADIAN...GFDL AND BAMD BRING THIS THING FARTHER WEST INTO THE NEW OREANS AREA. PROBLEM WITH ALL MODEL SOLUTIONS IS THE CURRENT GENERAL FLOW REGIME ACROSS THE ENTIRE GULF. THE GENERAL FLOW IS STILL WNW OUTSIDE THE ENVELOPE OF .
THE TROUGH THAT IS SUPPOSED TO PICK UP IS NOT BRINGING THIS FLOW MORE NORTH ATTM. IF THE TROUGH DOES NOT PICK THE HURRICANE UP...IT MAY LEAD TO A SLOWING TREND OVER TIME. ANOTHER LONG WAVE TROUGH WILL ENTER THE WED AND WILL DIG TOWARD THE SOUTH THURSDAY AND FRIDAY. IF DOES NOT FEEL THE PULL FROM THE CURRENT TROUGH IT MAY SIT OVER THE GULF WITH VERY WEAK STEERING CURRENTS BEFORE EVENTUALLY FEELING THE NEXT TROUGH'S PULL. THIS IS POSSIBLE BUT ACCORDING TO TPC'S FORECAST NOT PROBABLE. WOULD LIKE TO SEE A MORE NORTHWARD SHIFT IN 'S TRACK BEFORE FEELING MORE COMFORTABLE.
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AdmittedHacker
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Guppie.. we all expect a turn. My point is merely that if the current trend continues it will be further west than predicted, as will eventual landfall... by 50 to 80 nm if continues to fool the as it has done so far.
Just look at the 0500 EST position, which is already 15.6 miles SW of its anticipated location which was just predicted on the 2300 EST update...
Continously further west than the models, a lot of stored energy and inertia headed WNW, and no significant steering currents to alter its course... New Orleans had better be watching!
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berrywr
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13 Sep - 1000Z - Your observation is correct; is now moving NW. I read the discussion issued at 09Z and please note the forecaster was prepared to make the track more west than continuity would allow; that said, the current shear over the Gulf coast is quite impressive; 70 knots over Central Alabama, and forecasted to remain above the criteria necessary to sustain a Category 4/5 hurricane. If this is indeed the beginning of the long expected right turn, it is doubtful that will track to the La. coast. I suspect the boys have this advisory thought out and is correct for gradual weakening; assuming the shear persists as currently forecasts by SHIP model. There will be some impact by the current shortwave traversing through the Gulf coast states today, but the next one now over the inter-mountain area of the US is expected to be what pulls north and northeast in the 72 hour forecast period; perhaps sooner. It has to be said, that model guidance is very suspect beyond 72 hours, and with every advisory, course correction has been made westward. I doubt beyond the 11 am advisory there will be anymore westward adjustment.
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Sincerely,
Bill Berry
"Survived Trigonometry and Calculus I"
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GuppieGrouper
Weather Master
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Please don't take my emotional ramblings to heart. I am just a worried daughter, who would much rather worry about myself, since I am a capable human being, rather than worry about my parents who are aging and becoming like children who are depending on the weather channel to keep them safe. I will now be quiet unless I can think of something constructive to say.
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God commands. Laymen guess. Scientists record.
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tikibar
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I think the turn will start coming soon (12-24hrs)
I base that on the flattening of the front of the storm.
Disclaimer:
Not a met. Never said I was.
professional rookie on a closed course! Individual results may vary. 
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berrywr
Weather Analyst
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In intense storms greater than Category 3 it is normal for storms to undergo a concentric eyewall replacement. The outer eyewall robs moisture and heat from the inner eye wall which results in an increase in pressure and drop in winds; this process normally takes between 6 and 12 hours, upon completion the eye is bigger; but begins to contract and as it does so, the storm re-intensifies by using the theory referred to as the Conservation of Angular Momentum; like the water down a drain, as the circulation tightens, the particles - air and water increase in speed until two other forces act upon it as well - centripetal and centrifugal which all lead to the formation of the eye. In intense storms it is possible to have multiple eye walls. Hall and lightning are not as uncommon as you may think; remembering how tall these cells are at very, very cold temperatures in excess of negative 85. There is no known way to forecast intensity changes nor the predicatability of eyewall replacements with what is known today.
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Sincerely,
Bill Berry
"Survived Trigonometry and Calculus I"
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berrywr
Weather Analyst
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It is standard procedure to make an effort to follow continuity in forecasting future plots of hurricanes; though I disagree with the tactic. Models have been off on this storm several days and with each passage push the track west. You read like the current advisory 13/10Z - Track guidance ( a number of hurricane models predicting coordinates) never agree with each other from run to run except within 72 hours of landfall. That guidance normally allows the to take the track right down the middle. When you don't see the change, you'll here the say right of guidance or left... That's continuity. You don't want forecasters saying Key West get ready, and suddenly on the next run - Mobile, AL instead. They do so very gradually in the case of a sudden course change and simply common sense!
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Sincerely,
Bill Berry
"Survived Trigonometry and Calculus I"
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