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Hurricane Isaac, Part 3 - Analysis and Forecasting Thread


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Rick Knabb is not going to announce on TWC that they are upgrading to a hurricane. The NWS has very strict policies on that kind of information being disseminated via products.

USAF plane about to penetrate eye has extrap SLP of 968.4 mb with 32 knot north winds. Will be interesting to see what the drop shows.

That was a bad ob, obviously. They just penetrated with extrap around 976 mb which makes a lot more sense.

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It looks like this will really be remembered for the very heavy rains like Debby and the earlier non named very moist system that lifted north to the Gulf Coast from the Yucatan.

Couldn't the slow movement and large size of this 'cane also result in a very prolonged east or southeast wind piling up tons of water into Lake Borgne and then into Lake Pontchartrain? Isn't that similar to what happened in Katrina more than the rains? So could the 20 inches of rain plus the water piled in from the wind create conditions in Ponchartrain similar to Katrina? I know the levees are better, so it probably would not result in the same catastrophe, but still, there seems to be some potential here for something much worse than your average CAT 1 'cane.

I agree with NHC not upgrading it to a hurricane if they did not find hurricane strength winds--otherwise, why even have the criteria. But I still think it is inevitable that this will become a hurricane, probably by 11am.

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:lol: ADT is computer automated and totally objective. And why would anyone bother with satellite estimates when there has been full time recon coverage for the last 3 days?

The discussion is on reconciling sat presentation and storm pressure verdus actual results. Why should we even bother looking at satellite pics ir radar, then. Let's just put up a map of the plane and post dropsonde data.

Sent from my Milestone X 2

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The discussion is on reconciling sat presentation and storm pressure verdus actual results. Why should we even bother looking at satellite pics ir radar, then. Let's just put up a map of the plane and post dropsonde data.

Sent from my Milestone X 2

There is no "reconciling." When recon is in the storm and differs from Dvorak, Dvorak is wrong, recon is right.

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The discussion is on reconciling sat presentation and storm pressure verdus actual results. Why should we even bother looking at satellite pics ir radar, then. Let's just put up a map of the plane and post dropsonde data.

If all you're trying to do assess current intensity and there is full recon coverage, that is literally all you need. That's all NHC looks at.

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I think the human touch works better than ADT until the storm has a well developed eye and it can compare/contrast warm pixels in the eye with cold pixels in the eyewall.

Even human Dvorak has, IIRC, often been found to be a complete Cat off from actually recon measured strength...

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There is no "reconciling." When recon is in the storm and differs from Dvorak, Dvorak is wrong, recon is right.

I think the point needs to be made that while recon is all you currently need to assess current intensity, IT IS important to observe the satellite/radar data and try to make sense of it....this helps set precedence for future storms, and if enough evidence is presented over the years, perhaps our ESTIMATION technique can be updated the more we learn.

Yes, recon is all you need right now for this next warning, but look at the bigger picture as well.

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I think the human touch works better than ADT until the storm has a well developed eye and it can compare/contrast warm pixels in the eye with cold pixels in the eyewall.

Even human Dvorak has, IIRC, often been found to be a complete Cat off from actually recon measured strength...

I think the point needs to be made that while recon is all you currently need to assess current intensity, IT IS important to observe the satellite/radar data and try to make sense of it....this helps set precedence for future storms, and if enough evidence is presented over the years, perhaps our ESTIMATION technique can be updated the more we learn.

Yes, recon is all you need right now for this next warning, but look at the bigger picture as well.

Yep, and that's the point of SATCON. It correlates IR AND microwave imagery to aircraft recon to get a better estimate of the actual wind speed. It is the best satellite estimate out there currently, but unfortunately is limited by the availability of AMSU passes.

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One difference this time might be that we are seeing some semblance of an inner core try to form, and it doesn't looks like the dry air is penetrating that. We will see....

From the WV you can see the drier air continuing to get sucked into the circulation, Honestly doubt it drops more the 4-5 mb prior to landfall.

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Multiple clean 60-63 kt SFMR datapoints with a FL wind of 80 kt and peak 10s FL wind of 86 knots.

We can probably say, welcome hurricane Isaac.

Microwave presentation is still not amazing, but thats a decent building eyewall. Since this shot, radar shows its trying to close off with reflectivity now on the north side of the eye-wall feature...

akh5kl.jpg

The 9z HRRR now shows a mainly west track today, with the center still offshore at 00z with a very impressive satellite signature. Quite a large shift left in the track in the past 4-5 run cycles, giving credit to the ECMWF and GFS.

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I can't believe this thing is still heading due west... What are the chances it misses NO at this point?

This really isn't the thread for this kind of post...much better in the banter thread. However I do think it's important to point out that the strongest winds are well displaced from the center so exactly where it ends up tracking probably won't impact the conditions you feel in NO very much.

Kermit just found an 88 knot FL wind over 80 miles east of the center to illustrate the point.

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Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)

Transmitted: 28th day of the month at 12:54Z

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

Storm Number: 09

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

Mission Number: 30 seeall.png

Observation Number: 20

Part B: Data For Significant Levels...

Significant Temperature And Relative Humidity Levels...
Level Air Temperature Dew Point 988mb (Surface) 25.8°C (78.4°F) 25.3°C (77.5°F) 850mb 19.8°C (67.6°F) 18.4°C (65.1°F) 764mb 17.0°C (62.6°F) 16.0°C (60.8°F) 752mb 14.8°C (58.6°F) 14.8°C (58.6°F)

Significant Wind Levels...
Level Wind Direction Wind Speed 988mb (Surface) 195° (from the SSW) 70 knots (81 mph) 983mb 190° (from the S) 67 knots (77 mph) 970mb 185° (from the S) 77 knots (89 mph) 939mb 190° (from the S)
81 knots (93 mph)
909mb 195° (from the SSW) 74 knots (85 mph) 896mb 200° (from the SSW) 67 knots (77 mph) 850mb 210° (from the SSW) 64 knots (74 mph) 752mb 220° (from the SW) 54 knots (62 mph)
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Product: NOAA Temp Drop (Dropsonde) Message (UZNT13 KWBC)

Transmitted: 28th day of the month at 12:54Z

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

Storm Number: 09

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

Mission Number: 30 seeall.png

Observation Number: 20

Part B: Data For Significant Levels...

Significant Temperature And Relative Humidity Levels...
Level Air Temperature Dew Point 988mb (Surface) 25.8°C (78.4°F) 25.3°C (77.5°F) 850mb 19.8°C (67.6°F) 18.4°C (65.1°F) 764mb 17.0°C (62.6°F) 16.0°C (60.8°F) 752mb 14.8°C (58.6°F) 14.8°C (58.6°F)

Significant Wind Levels...
Level Wind Direction Wind Speed 988mb (Surface) 195° (from the SSW) 70 knots (81 mph) 983mb 190° (from the S) 67 knots (77 mph) 970mb 185° (from the S) 77 knots (89 mph) 939mb 190° (from the S)
81 knots (93 mph)
909mb 195° (from the SSW) 74 knots (85 mph) 896mb 200° (from the SSW) 67 knots (77 mph) 850mb 210° (from the SSW) 64 knots (74 mph) 752mb 220° (from the SW) 54 knots (62 mph)

Surface winds of 70kt is good enough for an upgrade for sure.
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Time: 13:17:00Z

Coordinates: 28.6333N 87.6833W

Acft. Static Air Press: 842.9 mb (~ 24.89 inHg)

Acft. Geopotential Hgt: 1,410 meters (~ 4,626 feet)

Extrap. Sfc. Press: 991.6 mb (~ 29.28 inHg)

D-value: -

Flt. Lvl. Wind (30s): From 139° at 85 knots (From the SE at ~ 97.7 mph)

Air Temp: 16.0°C* (~ 60.8°F*)

Dew Pt: 16.0°C* (~ 60.8°F*)

Peak (10s) Flt. Lvl. Wind: 89 knots (~ 102.3 mph)

SFMR Peak (10s) Sfc. Wind: 56 knots (~ 64.4 mph)

SFMR Rain Rate: 6 mm/hr (~ 0.24 in/hr)

(*) Denotes suspect data

If this stuff starts coming down to the surface soon, look out.

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