ATL: Ex COLIN - Discussion

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Re: ATL : Tropical Storm Colin - DISCUSSION

#1341 Postby ozonepete » Wed Aug 04, 2010 8:04 pm

Wthrman13 wrote:
ozonepete wrote:
Thanks for pointing that out. I wasn't clear enough. I wasn't talking about conservation of angular momentum within its own fluid envelope. And you are certainly right that there are other forces involved - I didn’t want to get into it too heavily here. However, I wasn’t applying the laws of motion to it as if it were a solid object. I fully understand that a hurricane is not a solid object like a ball or a car (I would hope!). But even though a TC is not a solid object, but indeed a rotating fluid, it still has angular momentum with respect to the earth’s axis. The conservation of that momentum causes a westward moving cyclone to experience an acceleration to the east as it move’s northward. That’s what I was talking about.
I also totally agree that many aspects of the interaction of the vortex with its steering currents is highly non-linear. But non-linear doesn’t exclude angular momentum.


Thanks for clarifying. I just see the misconception of "hurricane as huge lumbering freight train" quite often, and I erred in assuming you were propagating that.



:) That's funny. BTW I love reading your posts. You ARE an expert. Correct me anytime you want.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1342 Postby ozonepete » Wed Aug 04, 2010 8:07 pm

hurricaneCW wrote:Something insane would have to happen to allow it to come further west than forecast. According to the model suite, it's still moving between wnw and nw at 21 knots. The track looks to be very Bill-ish.


But remember the models are bad on weak systems. Having said that, I also think it's a fish. :)
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1343 Postby hurricaneCW » Wed Aug 04, 2010 8:10 pm

Does anyone have the shear forecasts? Colin could really become strong if the shear were to really subside. It'll be difficult to organize right now even though ex-Colin is clearly trying to.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1344 Postby HURAKAN » Wed Aug 04, 2010 8:14 pm

hurricaneCW wrote:Does anyone have the shear forecasts? Colin could really become strong if the shear were to really subside. It'll be difficult to organize right now even though ex-Colin is clearly trying to.


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SHEAR (KT)        15    24    24    20    20    21    21    17    15     3    10    10    14
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1345 Postby Wthrman13 » Wed Aug 04, 2010 8:16 pm

wjs3 wrote:
ozonepete wrote:
Thanks for pointing that out. I wasn't clear enough. I wasn't talking about conservation of angular momentum within its own fluid envelope. And you are certainly right that there are other forces involved - I didn’t want to get into it too heavily here. However, I wasn’t applying the laws of motion to it as if it were a solid object. I fully understand that a hurricane is not a solid object like a ball or a car (I would hope!). But even though a TC is not a solid object, but indeed a rotating fluid, it still has angular momentum with respect to the earth’s axis. The conservation of that momentum causes a westward moving cyclone to experience an acceleration to the east as it move’s northward. That’s what I was talking about.
I also totally agree that many aspects of the interaction of the vortex with its steering currents is highly non-linear. But non-linear doesn’t exclude angular momentum.


Hey, um, Pete--

You lost me on the highlighted part. If a TC is moving westward, how does it accelerate to the east as it moves northward? It's gotta be doing one or the other--westward OR northward, right? I think (?) what you mean is that as a westward moving cyclone turns northward, there's an eastward component?

Wouldn't that element be tiny compared to the effect of steering currents, BTW? In this case in particular, the ridge got crushed, right?

WJS3


I think he is talking about the beta effect, but this wouldn't result in an eastward acceleration, but rather a northwestward acceleration, for a westward moving tropical cyclone. See, e.g., http://www.aoml.noaa.gov/hrd/hrd_sub/motion.html and http://arjournals.annualreviews.org/doi ... 903.175702

Note that the beta effect involves the change in Coriolis force with latitude (i.e. an increase as one moves poleward), and, in particular, the linear and nonlinear interaction of a TC vortex with this gradient.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1346 Postby Wthrman13 » Wed Aug 04, 2010 8:20 pm

ozonepete wrote:
Wthrman13 wrote:
ozonepete wrote:
Thanks for pointing that out. I wasn't clear enough. I wasn't talking about conservation of angular momentum within its own fluid envelope. And you are certainly right that there are other forces involved - I didn’t want to get into it too heavily here. However, I wasn’t applying the laws of motion to it as if it were a solid object. I fully understand that a hurricane is not a solid object like a ball or a car (I would hope!). But even though a TC is not a solid object, but indeed a rotating fluid, it still has angular momentum with respect to the earth’s axis. The conservation of that momentum causes a westward moving cyclone to experience an acceleration to the east as it move’s northward. That’s what I was talking about.
I also totally agree that many aspects of the interaction of the vortex with its steering currents is highly non-linear. But non-linear doesn’t exclude angular momentum.


Thanks for clarifying. I just see the misconception of "hurricane as huge lumbering freight train" quite often, and I erred in assuming you were propagating that.



:) That's funny. BTW I love reading your posts. You ARE an expert. Correct me anytime you want.


No problem, and I do appreciate that. I have to confess though, that my area of expertise in meteorology is severe local storms and tornadoes, and not as much tropical cyclones (but there is obviously a lot of overlap in the dynamics, etc). I always enjoy discussing these things on forums, because it often forces me to go back to the books and make sure I know what the heck I'm talking about if I'm going to correct somebody! Your post prompted me to go refresh myself on the beta effect, etc. Everyone learns.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1347 Postby Macrocane » Wed Aug 04, 2010 8:29 pm

It's always interesting to read the comments of the pro mets especially in complex systems like Colin, keep teaching us we appreciate.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1348 Postby hurricaneCW » Wed Aug 04, 2010 8:36 pm

HURAKAN wrote:
hurricaneCW wrote:Does anyone have the shear forecasts? Colin could really become strong if the shear were to really subside. It'll be difficult to organize right now even though ex-Colin is clearly trying to.


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SHEAR (KT)        15    24    24    20    20    21    21    17    15     3    10    10    14


That's not too good. It will definitely not allow Colin to become a hurricane.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1349 Postby HURAKAN » Wed Aug 04, 2010 8:38 pm

hurricaneCW wrote:
HURAKAN wrote:
hurricaneCW wrote:Does anyone have the shear forecasts? Colin could really become strong if the shear were to really subside. It'll be difficult to organize right now even though ex-Colin is clearly trying to.


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TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
SHEAR (KT)        15    24    24    20    20    21    21    17    15     3    10    10    14


That's not too good. It will definitely not allow Colin to become a hurricane.


That's if you believe SHIPS ... my opinion, throw it out of the window!!!

ULL / TUTT are hard to predict and because of that, that forecast is likely erroneous.

Nonetheless, is less shear than it has been getting
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1350 Postby ozonepete » Wed Aug 04, 2010 8:39 pm

hurricaneCW wrote:
HURAKAN wrote:
hurricaneCW wrote:Does anyone have the shear forecasts? Colin could really become strong if the shear were to really subside. It'll be difficult to organize right now even though ex-Colin is clearly trying to.


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TIME (HR)          0     6    12    18    24    36    48    60    72    84    96   108   120
SHEAR (KT)        15    24    24    20    20    21    21    17    15     3    10    10    14


That's not too good. It will definitely not allow Colin to become a hurricane.


?? You're missing the very low shear out at 72 hours and later. Only 3-15 knots. That's basically no shear at all. Of course it has to hold on through 20 knots or so of shear until then, but 20 knots is considered only moderate shear and many cyclones easily survive that, especially depending on the direction of the shear relative to the cyclone.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1351 Postby canes101 » Wed Aug 04, 2010 10:26 pm

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#1352 Postby HURAKAN » Wed Aug 04, 2010 10:31 pm

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Accuwx's take
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#1353 Postby TwisterFanatic » Wed Aug 04, 2010 10:33 pm

Do you think the NHC makes it a code red at 2AM?
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#1354 Postby Gustywind » Wed Aug 04, 2010 10:34 pm

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Re: ATL : Tropical Storm Colin - DISCUSSION

#1355 Postby fci » Wed Aug 04, 2010 10:40 pm

hurricaneCW wrote:One of the few times where the Herbert Box doesn't apply. The storm crossed 60W south of 20N, and even now is near 20N and 63W. Also, kind of unusual to see a storm curve out like that in early August where the Bermuda Ridge should be at its strongest.

The Hebert box is not an absolute! If a storm crosses into it that does not equal a US strike. It merely presents some statistics regarding frequency of strikes when a tropical cyclone passes through the box. Stating it is one of the "few" to not strike is simply not correct. Just like a TC that does NOT pass through is not automatically not going to strike
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#1356 Postby RL3AO » Wed Aug 04, 2010 10:48 pm

Continuing on the Hebert Box (not Herbert) thing, it says that many of Florida's storms moved through one of those two boxes, not that most storms that move through one of those boxes hit Florida.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1357 Postby SouthFloridawx » Wed Aug 04, 2010 11:09 pm

So if it's not being listed as a storm under the NHC's website, why are models still being run under 04L?
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1358 Postby AJC3 » Wed Aug 04, 2010 11:30 pm

fci wrote:
hurricaneCW wrote:One of the few times where the Herbert Box doesn't apply. The storm crossed 60W south of 20N, and even now is near 20N and 63W. Also, kind of unusual to see a storm curve out like that in early August where the Bermuda Ridge should be at its strongest.


The Hebert box is not an absolute! If a storm crosses into it that does not equal a US strike. It merely presents some statistics regarding frequency of strikes when a tropical cyclone passes through the box. Stating it is one of the "few" to not strike is simply not correct. Just like a TC that does NOT pass through is not automatically not going to strike


Absolutely. Peeps are misunderstanding the methodology of how Paul Hebert came up with his two boxes. Firstly, Paul only looked at HURRICANES, as opposed to all tropical cyclones. Moreover, he looked at hurricanes that struck south Florida FIRST, then noted that most of them passed through one of his two infamous 5 x 5 boxes.

What he DID NOT do was to look at all hurricanes that passed through these boxes, then noted that most of them wound up striking south Florida.

It's like the old logic problem: "If A occurs, then there's a higher than average chance that B occurred first" is not the same thing as "If B occurs, then there's a higher than average chance that A will occur".

Consequently, stating that "If a hurricane strikes south Florida, then there's a higher than average chance that it passed through one of those two boxes." is not the same thing as saying "If a hurricane passes through one of the Hebert Boxes, then it has a higher than average chance of striking south Florida. The former (i.e. Hebert's study) does not equate to the latter. As Paul himself said, it's less of a correlation and more of a "you better pay attention if it does" sort of thing.

I encourage peeps to take a look here, and take note of the conclusions: http://www.hurricanecity.com/hebertbox.htm

So what does all this mean when a Hurricane passes or develops in the Hebert Box east of Puerto Rico since 1950?

1)N Carolina has as much of a chance to get hit as Florida.
2)20.58% or most go out to sea without hitting land.
3)Only 8.82% make it into the Gulf of Mexico when they pass through the box as a hurricane.
4)Puerto Rico will get hit 20.58% of the time (the highest outside of n Antilles).

What about Box #2,Hurricanes developing or moving through after Oct 1st since 1950?

Cuba & the Bahamas are at highest risk late in the season.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1359 Postby clfenwi » Wed Aug 04, 2010 11:59 pm

SouthFloridawx wrote:So if it's not being listed as a storm under the NHC's website, why are models still being run under 04L?


Probably a vagary of how the Automated Tropical Cyclone Forecasting (ATCF) system (which handles all of the data/forecast products) is set up. I'm guessing that the alternative would be to open a new invest and it wouldn't be possible to re-number that invest to storm 04L if needed. Reasoned speculation on my part; don't think you can read anything beyond it still being run as 04L other than NHC still considers what's out there to be ex-Colin.
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Re: ATL : Tropical Storm Colin - DISCUSSION

#1360 Postby clfenwi » Thu Aug 05, 2010 12:39 am

2 AM TWO remarks

THE REMNANT OF TROPICAL STORM COLIN...A BROAD AREA OF LOW
PRESSURE...IS LOCATED A COUPLE HUNDRED MILES NORTH OF THE
NORTHERNMOST LEEWARD ISLANDS AND IS MOVING TOWARD THE NORTHWEST AT
20 TO 25 MPH. SATELLITE IMAGES INDICATE THAT THE ASSOCIATED CLOUD
PATTERN CONTINUES TO SHOW SIGNS OF ORGANIZATION...BUT SURFACE
OBSERVATIONS SUGGEST THAT IT LACKS A WELL-DEFINED CIRCULATION.
TROPICAL STORM FORCE WINDS ARE LIKELY OCCURRING OVER WATER WELL TO
THE NORTH-NORTHEAST OF THE LEEWARD ISLANDS AND ALTHOUGH UPPER-LEVEL
WINDS ARE NOT FAVORABLE FOR SIGNIFICANT DEVELOPMENT...THE SYSTEM
HAS THE POTENTIAL TO REGAIN TROPICAL STORM STATUS LATER TODAY OR ON
FRIDAY. AN AIR FORCE RESERVE UNIT RECONNAISSANCE AIRCRAFT IS
SCHEDULED TO INVESTIGATE THE AREA LATER TODAY IF NECESSARY. THERE
IS A MEDIUM CHANCE...40 PERCENT...OF THIS SYSTEM BECOMING A
TROPICAL CYCLONE DURING THE NEXT 48 HOURS.
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