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Hurricane Isaac, Part 3 - Analysis and Forecasting Thread


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Product: NOAA Vortex Message (URNT12 KWBC)

Transmitted: 28th day of the month at 22:21Z

Aircraft: Lockheed WP-3D Orion (Reg. Num. N42RF)

Storm Number & Year: 09L in 2012

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

Mission Number: 33

Observation Number: 09

A. Time of Center Fix: 28th day of the month at 21:59:55Z

B. Center Fix Coordinates: 28°46'N 89°03'W (28.7667N 89.05W)

B. Center Fix Location: 103 miles (166 km) to the SE (144°) from New Orleans, LA, USA.

C. Minimum Height at Standard Level: 2,917m (9,570ft) at 700mb

D. Estimated (by SFMR or visually) Maximum Surface Wind: Not Available

E. Bearing & Range from Center of Estimated Maximum Surface Wind (Undecoded):301 deg 1 nm

F. Maximum Flight Level Wind Inbound: From 83° at 80kts (From the E at ~ 92.1mph)

G. Location of Maximum Flight Level Wind Inbound: 45 nautical miles (52 statute miles) to the NNW (343°) of center fix

H. Minimum Sea Level Pressure: 971mb (28.67 inHg)

I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 12°C (54°F) at a pressure alt. of 3,061m (10,043ft)

J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 17°C (63°F) at a pressure alt. of 3,066m (10,059ft)

K. Dewpoint Temp (collected at same location as temp inside eye): 13°C (55°F)

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

L. Eye Character: Open in the southwest

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: 700mb

O. Fix Determined By / Fix Level (Undecoded): 1 / 1 nm

Remarks Section - Remarks That Were Decoded...

Maximum Flight Level Temp: 17°C (63°F) which was observed 7 nautical miles to the NE/ENE (56°) from the flight level center

Remarks Section - Additional Remarks...

MAX OUTBOUND FL WIND AND MAX FL WIND 91 KT NE QUAD 22:10:20Z

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I don't really agree it has the appearance of RI.

You're certainly entitled to disagree :) . I don't see a 40mb drop in 24 hours, but I don't think the Euro's pressure forecast is out of the question either of 950-960mb. It all depends on which way it drifts/etc.

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FWIW The Gustav surge at Shell Beach was 9.5 ft; looks like this will be easily beaten.

Surge suddenly started dropping at the station on Lake Ponchartrain, though - not sure why.

Figured out the answer I think, that gauge is likely in the London ave canal since 2.5 ft is the "safe point" according to local officials. They closed off the gates between the canal and the lake and keep pumping water out whenever it reaches 2.5 ft.

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You're certainly entitled to disagree :) . I don't see a 40mb drop in 24 hours, but I don't think the Euro's pressure forecast is out of the question either of 950-960mb. It all depends on which way it drifts/etc.

Agreed.

Also of note is that the highest OHC on the Gulf Coast is where Isaac currently is positioned. Can't be a bad thing.

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My best estimate looking at radar is that the inner "eyewall" (or whatever it is) will pass over or just east of Boothville, and perhaps slightly east of Hopedale thereafter. There's really not much along that path - just some marshland and various deltas branching off from the Mississippi river. If Isaac continues along a straight line, that would put it somewhere near or just east of Slidell, but I suspect we see a slight jog to the west before then.

In either case, many more hours of easterly winds blowing right into Borgne and Pontchartrain.

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My best estimate looking at radar is that the inner "eyewall" (or whatever it is) will pass over or just east of Boothville, and perhaps slightly east of Hopedale thereafter. There's really not much along that path - just some marshland and various deltas branching off from the Mississippi river. If Isaac continues along a straight line, that would put it somewhere near or just east of Slidell, but I suspect we see a slight jog to the west before then.

In either case, many more hours of easterly winds blowing right into Borgne and Pontchartrain.

And many hours of potential strengthening as that is all warm marshland and brackish lake region. The idea that Plaquemines Parish, most of which is likely part of the Gulf of Mexico right now, is going to halt the intensification trend is laughable.

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While the inner ring of convection appears to be an eyewall structurally, radial velocities (and I believe the latest HH flight as well) are still showing stronger winds in the outer eyewall. Seems to be a case of "too little too late" with too much radial enthalpy flux being robbed and angular momentum confined to the much larger, outer eyewall.

edit to add: Maybe I spoke too soon. Superstorms93's post suggests that the inner eyewall is ramping up quickly.

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18z GFS still insists on taking Isaac due west for 30 hours, considering continued movement at present I think we can discount that possibility. Even seems to be a bit East of forecast at the moment.

considering that the 18z GFS has some support from other models including the Euro, I don't discount anything at this point, including a west drift. The movement north could just be from the inner core consolidating and wobbling.

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While the inner ring of convection appears to be an eyewall structurally, radial velocities (and I believe the latest HH flight as well) are still showing stronger winds in the outer eyewall. Seems to be a case of "too little too late" with too much radial enthalpy flux being robbed and angular momentum confined to the much larger, outer eyewall.

I would disagree with that assessment.

http://www.ndbc.noaa.gov/show_plot.php?station=kmis&meas=wdpr&uom=E&time_diff=-5&time_label=CDT

Data from the above station shows a pronounced drop after the outer eyewall passed, with the 'inner' eyewall ramping things up considerably. Latest gusts in excess of 100 miles per hour.

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I would disagree with that assessment.

http://www.ndbc.noaa...&time_label=CDT

Data from the above station shows a pronounced drop after the outer eyewall passed, with the 'inner' eyewall ramping things up considerably. Latest gusts in excess of 100 miles per hour.

I know for a fact that station isn't anywhere near the inner eyewall feature, it's still in the outer eyewall.

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