ATL: PALOMA - Tropical Depression - Discussion

[jinftl]

At the risk of being run out of town for even ‘going there’……for those wondering what the NHC probabilities of Florida impacts from Paloma are (and this may be 'climatologically based', as measured by wind speed probability…the % probability of at least 34kt winds is as follows:

Marathon is the highest with 16%, followed by Key West with 15%, Miami 13%, and West Palm 9%.


TROPICAL STORM PALOMA WIND SPEED PROBABILITIES NUMBER 3
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL172008
0900 UTC THU NOV 06 2008

CHANCES THAT THE MAXIMUM SUSTAINED (1-MINUTE AVERAGE) WIND SPEED OF
THE TROPICAL CYCLONE WILL BE WITHIN ANY OF THE FOLLOWING CATEGORIES
AT EACH OFFICIAL FORECAST TIME DURING THE NEXT 5 DAYS.
PROBABILITIES ARE GIVEN IN PERCENT.
II. WIND SPEED PROBABILITY TABLE FOR SPECIFIC LOCATIONS

CHANCES OF SUSTAINED (1-MINUTE AVERAGE) WIND SPEEDS OF AT LEAST
...34 KT (39 MPH... 63 KPH)...
...50 KT (58 MPH... 93 KPH)...
...64 KT (74 MPH...119 KPH)...
FOR LOCATIONS AND TIME PERIODS DURING THE NEXT 5 DAYS

- - - - WIND SPEED PROBABILITIES FOR SELECTED LOCATIONS - - - -

FROM FROM FROM FROM FROM FROM FROM
TIME 06Z THU 18Z THU 06Z FRI 18Z FRI 06Z SAT 06Z SUN 06Z MON
PERIODS TO TO TO TO TO TO TO
18Z THU 06Z FRI 18Z FRI 06Z SAT 06Z SUN 06Z MON 06Z TUE

FORECAST HOUR (12) (24) (36) (48) (72) (96) (120)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
LOCATION KT )

W PALM BEACH 34 X X( X) X( X) X( X) 1( 1) 6( 7) 2( 9)
W PALM BEACH 50 X X( X) X( X) X( X) X( X) 2( 2) 1( 3)
W PALM BEACH 64 X X( X) X( X) X( X) X( X) 1( 1) X( 1)

MIAMI FL 34 X X( X) X( X) X( X) 3( 3) 8(11) 2(13)
MIAMI FL 50 X X( X) X( X) X( X) X( X) 3( 3) 2( 5)
MIAMI FL 64 X X( X) X( X) X( X) X( X) 1( 1) 1( 2)

MARATHON FL 34 X X( X) X( X) 1( 1) 4( 5) 9(14) 2(16)
MARATHON FL 50 X X( X) X( X) X( X) 2( 2) 4( 6) 1( 7)
MARATHON FL 64 X X( X) X( X) X( X) X( X) 2( 2) 1( 3)

KEY WEST FL 34 X X( X) X( X) 1( 1) 5( 6) 8(14) 1(15)
KEY WEST FL 50 X X( X) X( X) X( X) 2( 2) 3( 5) 1( 6)
KEY WEST FL 64 X X( X) X( X) X( X) 1( 1) 2( 3) 1( 4)

[jlauderdal]

Here is a refresher on da cone:

Definition of the NHC Track Forecast Cone

Definition:

The cone represents the probable track of the center of a tropical cyclone, and is formed by enclosing the area swept out by a set of circles (not shown) along the forecast track (at 12, 24, 36 hours, etc). The size of each circle is set so that two-thirds of historical official forecast errors over a 5-year sample fall within the circle. The circle radii defining the cones in 2008 for the Atlantic and eastern North Pacific basins are given in the table below.

One can also examine historical tracks to determine how often the entire 5-day path of a cyclone remains completely within the area of the cone. This is a different perspective that ignores most timing errors. For example, a storm moving very slowly but in the expected direction would still be within the area of the cone, even though the track forecast error could be very large. Based on forecasts over the previous 5 years, the entire track of the tropical cyclone can be expected to remain within the cone roughly 60-70% of the time.

http://www.nhc.noaa.gov/aboutcone.shtml

THIS post and Derek's earlier post saying basically the same thing is just fascinating to me. I had no idea how "disconnected" the cone shape is from current atmospheric dynamics. The cone is really a pretty blunt instrument. Thanks for posting this guys.

yep, the beauty of the cone is there is no guesswork, its nothing but statistics based on past performance. There really should be no arguing about cones as long as people understand them.

[wxman57]

At the risk of being run out of town for even ‘going there’……for those wondering what the NHC probabilities of Florida impacts from Paloma are (and this may be 'climatologically based', as measured by wind speed probability…the % probability of at least 34kt winds is as follows:

Marathon is the highest with 16%, followed by Key West with 15%, Miami 13%, and West Palm 9%.

snip...

The probabilities are computed using a combination of climatology, past forecast error, the projected size of Paloma's wind field (and typical error in predicting wind field size).

As for the cone issue, as has been stated, it's just a representation of the 66th percentile of forecast error over the past 5 years, meaning that 66% of the time in the past 5 years of Atlantic Basin forecast, the track remained completely inside the cone. It doesn't matter how confident the forecaster is in a track, the cone size never changes. And the cone can't be adjusted to remove "impossibilities" such as a westward moving storm near 10N tracking south of the Equator (or the quite unlikely occurrence of Paloma brushing the Keys).

[Sanibel]

2008 was Cuba's year. Bad year for crops down there.


Sorry 15 storm folks. That number busts.

[jinftl]

This is a more general question and not for this thread...but it makes me wonder...should the NHC and forecasters really be telling people to focus on the cone and not the black line? How do we know when a cone is based on climatology more than forecasted threat? If the cone coming close to south florida is the 'yes, but not really a threat' climatological cone, there has to be other storms where being in or near the cone was not a true threat.

Before the village starts missing its idiot, I have to ask....if Paloma was moving west right now, would we see the same cone since climatology and history would dictate a storm in november isn't moving west, say, to the western gulf?

At the risk of being run out of town for even ‘going there’……for those wondering what the NHC probabilities of Florida impacts from Paloma are (and this may be 'climatologically based', as measured by wind speed probability…the % probability of at least 34kt winds is as follows:

Marathon is the highest with 16%, followed by Key West with 15%, Miami 13%, and West Palm 9%.

snip...

The probabilities are computed using a combination of climatology, past forecast error, the projected size of Paloma's wind field (and typical error in predicting wind field size).

As for the cone issue, as has been stated, it's just a representation of the 66th percentile of forecast error over the past 5 years, meaning that 66% of the time in the past 5 years of Atlantic Basin forecast, the track remained completely inside the cone. It doesn't matter how confident the forecaster is in a track, the cone size never changes. And the cone can't be adjusted to remove "impossibilities" such as a westward moving storm near 10N tracking south of the Equator (or the quite unlikely occurrence of Paloma brushing the Keys).

[Derek Ortt]

its not based upon climatological movement. The cone is based upon the 10-year mean ABSOLUTE forecast error. So if the MAE is 300NM, a circle is drawn around the forecast point with a radius of 300NM

[jlauderdal]

its not based upon climatological movement. The cone is based upon the 10-year mean ABSOLUTE forecast error. So if the MAE is 300NM, a circle is drawn around the forecast point with a radius of 300NM

10 year or 5 year?

[Derek Ortt]

http://www.nrlmry.navy.mil/tc-bin/tc_ho ... =composite

looks like an eye is forming

[tolakram]

Before the village starts missing its idiot, I have to ask....if Paloma was moving west right now, would we see the same cone since climatology and history would dictate a storm in november isn't moving west, say, to the western gulf?

Yes. The cone equation is fixed and does not change based on local or seasonal climatology. The cone equation remains the same and always follows the forecast path.

It's actually a radius drawn around each forecast point, but drawn as a cone for readability.

Make 4 dots on a piece of paper and call them forecast points. Each forecast point out from the current should have a bigger circle drawn around it, centered on the forecast position. The diameter of the circle is determined by how far the forecast point is from the current position. I'm not sure on the exact equation used to determine the diameter but the equation does not change based on the location of the storm or the time of year.

[jinftl]

Is there a correlation between areas in the statistical cone and hurricane watches and warnings? I guess it could be said that if you are still in the cone close enough where watches and warnings are needed, you are in fact at risk.

If I am getting it...can it be said:
Black line = NHC estimate of forecast, possibly a consensus of models they are using or see as valid
Cone = statistical range around that forecast track
Models = based on computerized analysis of atmospheric conditions input
Model shift = not based solely on history and climatology

If models shift, track forecast shifts, cone moves with it?

Before the village starts missing its idiot, I have to ask....if Paloma was moving west right now, would we see the same cone since climatology and history would dictate a storm in november isn't moving west, say, to the western gulf?

Yes. The cone equation is fixed and does not change based on local or seasonal climatology. The cone equation remains the same and always follows the forecast path.

It's actually a radius drawn around each forecast point, but drawn as a cone for readability.

Make 4 dots on a piece of paper and call them forecast points. Each forecast point out from the current should have a bigger circle drawn around it, centered on the forecast position. The diameter of the circle is determined by how far the forecast point is from the current position. I'm not sure on the exact equation used to determine the diameter but the equation does not change based on the location of the storm or the time of year.

[jlauderdal]

Is there a correlation between areas in the statistical cone and hurricane watches and warnings? I guess it could be said that if you are still in the cone close enough where watches and warnings are needed, you are in fact at risk.

If I am getting it...can it be said:
Black line = NHC estimate of forecast, possibly a consensus of models they are using or see as valid
Cone = statistical range around that forecast track
Models = based on computerized analysis of atmospheric conditions input
Model shift = not based solely on history and climatology

If models shift, track forecast shifts, cone moves with it?

Before the village starts missing its idiot, I have to ask....if Paloma was moving west right now, would we see the same cone since climatology and history would dictate a storm in november isn't moving west, say, to the western gulf?

Yes. The cone equation is fixed and does not change based on local or seasonal climatology. The cone equation remains the same and always follows the forecast path.

It's actually a radius drawn around each forecast point, but drawn as a cone for readability.

Make 4 dots on a piece of paper and call them forecast points. Each forecast point out from the current should have a bigger circle drawn around it, centered on the forecast position. The diameter of the circle is determined by how far the forecast point is from the current position. I'm not sure on the exact equation used to determine the diameter but the equation does not change based on the location of the storm or the time of year.

NHC takes the guesswork out of watches and warnings just like the cone.


Hurricane Warning:
A warning that sustained winds 64 kt (74 mph or 119 km/hr) or higher associated with a hurricane are expected in a specified coastal area in 24 hours or less. A hurricane warning can remain in effect when dangerously high water or a combination of dangerously high water and exceptionally high waves continue, even though winds may be less than hurricane force.

Hurricane Watch:
An announcement for specific coastal areas that hurricane conditions are possible within 36 hours.

[Derek Ortt]

the Hurricane warning is now issued when according to the WS probabilities, the chance of hurricane force winds exceeds 10%. It is dropped when the chance falls below 1%

[CrazyC83]

Looks to be rapidly intensifying. I wouldn't be shocked for Recon to find Hurricane Paloma.

[jinftl]

So is it correct that warnings are based on climatological/historical probabilities...on the cone, in other words?

Right now, the WS probabilities for ts force (34kt) winds is 14% for Marathon, 13% for Key West, and 10% for Miami....if those stay above 10% as the thershold timeframe for warnings approaches, could we see ts warnings for those areas?

the Hurricane warning is now issued when according to the WS probabilities, the chance of hurricane force winds exceeds 10%. It is dropped when the chance falls below 1%

[Tampa Bay Hurricane]

So is it correct that warnings are based on climatological/historical probabilities...on the cone, in other words?

Right now, the WS probabilities for ts force (34kt) winds is 14% for Marathon, 13% for Key West, and 10% for Miami....if those stay above 10% as the thershold timeframe for warnings approaches, could we see ts warnings for those areas?

the Hurricane warning is now issued when according to the WS probabilities, the chance of hurricane force winds exceeds 10%. It is dropped when the chance falls below 1%

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products

Given how large this is, with the convection extending north hundreds of miles-
I expect the windfield to expand significantly over the next 3 days, which
I think may bring tropical storm warnings to parts of south Florida and the Keys...

The hurricane conditions will impact Cuba the hardest...category 2 looks conservative

[jinftl]

That said, i am still unclear why the 'all clear' has been sounded for florida...maybe the eye passing over downtown miami is not going to happen....but i am not convinced fringe effects are not impossible...that may change as we get closer and better data....but still not seeing the evidence for the categorical 'no florida effects' message...maybe it is the pessimist in me...or realist...LOL

So is it correct that warnings are based on climatological/historical probabilities...on the cone, in other words?

Right now, the WS probabilities for ts force (34kt) winds is 14% for Marathon, 13% for Key West, and 10% for Miami....if those stay above 10% as the thershold timeframe for warnings approaches, could we see ts warnings for those areas?

the Hurricane warning is now issued when according to the WS probabilities, the chance of hurricane force winds exceeds 10%. It is dropped when the chance falls below 1%

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products

Given how large this is, with the convection extending north hundreds of miles-
I expect the windfield to expand significantly over the next 3 days, which
I think may bring tropical storm warnings to parts of south Florida and the Keys...

The hurricane conditions will impact Cuba the hardest...category 2 looks conservative

[Sanibel]

A touch east of trop point I think.

Nothing will pull this towards Florida in my opinion.

Should get stronger with more distance from Honduras over the day. Doubt it would plow into a trough.

[fci]

Seems like the errors in these type of storms tend to be that they go further "east" than expected.

All of the Pro Mets seem to totally discount a Florida impact which is why I suspect it is not even mentioned at all in any forecasting.

[Sanibel]

Increasing depth along convergence axis as you proceed NE from center:

[Weatherfreak000]

Ahh.. the P and still perhaps the R storm yet for the season.

Do dynamics support a major?