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Hurricane Isaac, Part 3 - Analysis and Forecasting Thread


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This type of scenario was fairly well signaled. I remember conversations about a super slow/ stall etc.. main question was if it would happen before or after landfall. Prolific rains plus long duration strong winds should help kick up the wind damage a bit.

Depends on whom you talk to....I referenced in 'grinding to a hault" near the coastline at one point, and my post was quickly met with the rebutal that it would not stall entirely.

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I wish more would do this.

I ranted in the sne tropical thread late last week about how little autonomy mets display regarding the tropics....just spoon feeding the public TPC thoughts.

99% of the time I think this is a horrible, horrible idea for local mets to go cowboy...confusing the public, etc. And a lot really aren't qualified to do so.

However where NHC has a problem is right around landfalls when they stick to a movement that isn't real in hopes the forecast movement will resume, and it's just too obvious to ignore.

NHC could have at least mentioned the stall/due west movement models in the discussion, even if they were not reflected in the forecast.

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It looks like it's mostly wobbling in place in super long loops. I wouldn't necessarily call any of the other motions terribly meaningful. At some point it will probably resume a motion toward land.

It's one thing to ignore a 30 mile wobble 1000 miles from land. It's a totally different ballgame when the storm is pounding a major metropolitan area.

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Depends on whom you talk to....I referenced in 'grinding to a hault" near the coastline at one point, and my post was quickly met with the rebutal that it would not stall entirely.

They usually don't and that was sort of the counter.. Same when I was part of that discussion a few days ago... I did figure it might happen after landfall at tha pt tho. But the pattern was certainly arguing for it near landfall. There are of course a number of storms that have done weird stalls/loops/etc. In that sense it's not unheard of even if odd in any one place perhaps. In the last day or so especially a lot of guidance has had this coastal strafing scenario.

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It's one thing to ignore a 30 mile wobble 1000 miles from land. It's a totally different ballgame when the storm is pounding a major metropolitan area.

Well for a place like New Orleans I don't know if it makes much difference if the storm is where it is or a bit inland right now. Their main threat is arguably heavy rain and that's happening either way. It might make some difference in certain coastal areas and it prolongs the intensity at least a bit. But it was not forecast to rush through or anything. And despite the fact that it's remained offshore there's still no real indication it's increasing in intensity markedly or at all at this point.

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Product: Air Force Vortex Message (URNT12 KNHC)

Transmitted: 29th day of the month at 04:45Z

Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 308)

Storm Number & Year: 09L in 2012

Storm Name: Isaac (flight in the North Atlantic basin)

Mission Number: 32

Observation Number: 18

A. Time of Center Fix: 29th day of the month at 4:34:00Z

B. Center Fix Coordinates: 28°53'N 90°01'W (28.8833N 90.0167W) (View map)

B. Center Fix Location: 75 miles (121 km) to the S (178°) from New Orleans, LA, USA.

C. Minimum Height at Standard Level: 1,160m (3,806ft) at 850mb

D. Estimated (by SFMR or visually) Maximum Surface Wind: 59kts (~ 67.9mph)

E. Location of the Estimated Maximum Surface Wind: 31 nautical miles (36 statute miles) to the S (173°) of center fix

F. Maximum Flight Level Wind Inbound: From 275° at 71kts (From the W at ~ 81.7mph)

G. Location of Maximum Flight Level Wind Inbound: 29 nautical miles (33 statute miles) to the SSE/S (169°) of center fix

H. Minimum Sea Level Pressure: 969mb (28.61 inHg)

I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 17°C (63°F) at a pressure alt. of 1,523m (4,997ft)

J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 21°C (70°F) at a pressure alt. of 1,520m (4,987ft)

K. Dewpoint Temp (collected at same location as temp inside eye): 21°C (70°F)

K. Sea Surface Temp (collected at same location as temp inside eye): Not Available

L. Eye Character (Undecoded): Weak WSW

M. Eye Shape & Diameter: Circular with a diameter of 40 nautical miles (46 statute miles)

N. Fix Determined By: Penetration, Radar, Wind, Pressure and Temperature

N. Fix Level: 850mb

O. Navigation Fix Accuracy: 0.02 nautical miles

O. Meteorological Accuracy: 1 nautical mile

Remarks Section:

Maximum Flight Level Wind: 86kts (~ 99.0mph) in the northeast quadrant at 1:49:30Z

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Well for a place like New Orleans I don't know if it makes much difference if the storm is where it is or a bit inland right now. Their main threat is arguably heavy rain and that's happening either way. It might make some difference in certain coastal areas and it prolongs the intensity at least a bit. But it was not forecast to rush through or anything. And despite the fact that it's remained offshore there's still no real indication it's increasing in intensity markedly or at all at this point.

Except that, had it in fact been moving NW at 8 mph like NHC has been insisting all evening, the eye would have been inland for a number of hours and the storm would already have been starting to weaken, right?

It's just not anywhere close to where they kept saying it would be, and it's been obvious for hours that NW at 8 mph wasn't close to accurate. It shouldn't matter whether it "makes a difference," it should matter if it's accurate.

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99% of the time I think this is a horrible, horrible idea for local mets to go cowboy...confusing the public, etc. And a lot really aren't qualified to do so.

However where NHC has a problem is right around landfalls when they stick to a movement that isn't real in hopes the forecast movement will resume, and it's just too obvious to ignore.

NHC could have at least mentioned the stall/due west movement models in the discussion, even if they were not reflected in the forecast.

As usual, the truth lays somewhere int he middle...

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WNW at 7mph per NHC... as discussed above, some hints of W or WSW motion from radar

summary of 1200 am CDT...0500 UTC...information

-----------------------------------------------

location...29.0n 90.0w

about 60 mi...95 km se of Houma Louisiana

about 70 mi...110 km S of New Orleans Louisiana

maximum sustained winds...80 mph...130 km/h

present movement...WNW or 290 degrees at 7 mph...11 km/h

minimum central pressure...969 mb...28.61 inches

Read more at http://www.wunderground.com/tropical/at201209.public.html#ijuA8PBVvikit6a7.99

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Its interesting, I was thinking the marshes are really shallow water and were probably even warmer than most of the gulf, but with the constant rain for the last 12 hours they must be cooling significantly and while they might have helped it earlier they will probably work against Issac now.

Oceanic Heat Content, which takes into account DEPTH when calculating potential energy, is lower.

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Except that, had it in fact been moving NW at 8 mph like NHC has been insisting all evening, the eye would have been inland for a number of hours and the storm would already have been starting to weaken, right?

It's just not anywhere close to where they kept saying it would be, and it's been obvious for hours that NW at 8 mph wasn't close to accurate. It shouldn't matter whether it "makes a difference," it should matter if it's accurate.

I suppose. It might be weaker, a bit. It's a well developed low pressure.. it's not going to wind down too quick I don't think. Overall I think NHC has done extremely well with the storm so it's somewhat of a minor quibble at this point. If it ends up seriously changing the outcome of the forecast then it's a bigger issue maybe.

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WNW at 7mph per NHC... as discussed above, some hints of W or WSW motion from radar

summary of 1200 am CDT...0500 UTC...information

-----------------------------------------------

location...29.0n 90.0w

about 60 mi...95 km se of Houma Louisiana

about 70 mi...110 km S of New Orleans Louisiana

maximum sustained winds...80 mph...130 km/h

present movement...WNW or 290 degrees at 7 mph...11 km/h

minimum central pressure...969 mb...28.61 inches

Read more at http://www.wunderground.com/tropical/at201209.public.html#ijuA8PBVvikit6a7.99

No way, center fix you posted is south of that

F

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No way, center fix you posted is south of that

F

yeah not sure what's going on, here's the discrepancy:

last recon center fix was 12:45 EST: 28°53'N 90°01'W

1AM EST / 12AM CDT fix NHC report: 29.0n 90.0w

perhaps too subtle to make a difference, but the eye location is much less ambiguous than it was hours ago

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Doesn't look like it's moving now. Euro has that and then a general stop and start NNW over the next 5 hours

It's basically wobbling around while drifting west at less than 10 mph based on recon, keeping the same distance between itself and the coast. Unbelievable how it stopped right at the coast like that, on the anniversary of Katrina.

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It's basically wobbling around while drifting west at less than 10 mph based on recon, keeping the same distance between itself and the coast. Unbelievable how it stopped right at the coast like that, on the anniversary of Katrina.

Just saying,but most reliable models showed this, didn't they? Where he goes from here will be interesting....

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