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Hurricane Isaac, Part 3 - Analysis and Forecasting Thread


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That's obviously a flawed statement because we've been dealing with dry air entrainment all day.

My post was vague in that regard which is why I deleted it. I was simply observing that dry air without a mechanism to reach the core is not in and of itself a detrimental feature. I was not commenting on Isaac and his issues yesterday/today.

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FWIW NHC initialized 0Z models as a 60 knot TS, not a HU.

AL, 09, 2012082800, , BEST, 0, 267N, 865W, 60, 981, TS, 34, NEQ, 150, 160, 100, 180, 1008, 230, 30, 0, 0, L, 0, , 0, 0, ISAAC, D,

AL, 09, 2012082800, , BEST, 0, 267N, 865W, 60, 981, TS, 50, NEQ, 50, 60, 50, 40, 1008, 230, 30, 0, 0, L, 0, , 0, 0, ISAAC, D,

This was out for the 8pm advisory and there is no reason to upgrade this to a hurricane.

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There is no way anyone will be seeing a eye in satellite imagery right now. Heck, this thing has very little convection in the northern and eastern quadrants. I had to step back and take a little break, but this thing looks really disorganized right now. I'm honestly surprised how low the pressure was able to get with it in such poor condition. That said, it is ready to go if convection is finally able to fill in.

Product: NOAA Vortex Message (URNT12 KWBC)

Transmitted: 28th day of the month at 00:31Z

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: 28

Observation Number: 27

A. Time of Center Fix: 27th day of the month at 23:54:23Z

B. Center Fix Coordinates: 26°47'N 86°27'W (26.7833N 86.45W)

B. Center Fix Location: 257 miles (413 km) to the S (170°) from Pensacola, FL, USA.

C. Minimum Height at Standard Level: 2,981m (9,780ft) at 700mb

D. Estimated (by SFMR or visually) Maximum Surface Wind: 53kts (~ 61.0mph)

E. Location of the Estimated Maximum Surface Wind: 90 nautical miles (104 statute miles) to the WSW (258°) of center fix

F. Maximum Flight Level Wind Inbound: From 325° at 60kts (From the NW at ~ 69.0mph)

G. Location of Maximum Flight Level Wind Inbound: 110 nautical miles (127 statute miles) to the W (265°) of center fix

H. Minimum Sea Level Pressure: 983mb (29.03 inHg) - Extrapolated

I. Maximum Flight Level Temp & Pressure Altitude Outside Eye: 12°C (54°F) at a pressure alt. of 3,060m (10,039ft)

J. Maximum Flight Level Temp & Pressure Altitude Inside Eye: 15°C (59°F) at a pressure alt. of 3,032m (9,948ft)

K. Dewpoint Temp (collected at same location as temp inside eye): 11°C (52°F)

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

L. Eye Character: Poorly Defined

M. Eye Shape: Not Available

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 Wind: 70kts (~ 80.6mph) in the southeast quadrant at 22:34:49Z

Maximum Flight Level Wind Outbound: 63kts (~ 72.5mph) in the east quadrant at 0:00:53Z

Remarks Section - Additional Remarks...

SLP EXTRAP FROM 10K FT

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There is no way anyone will be seeing a eye in satellite imagery right now. Heck, this thing has very little convection in the northern and eastern quadrants. I had to step back and take a little break, but this thing looks really disorganized right now. I'm honestly surprised how low the pressure was able to get with it in such poor condition. That said, it is ready to go if convection is finally able to fill in.

It has shallow convection around the entire eye. The IR can't see it but the recent microwave passes have confirmed this. Yes, the eye itself is poorly defined, but the inner core as a whole has continued to steadily organize.

Also, the track appears to be almost 100 km east of the NHC forecast.

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Yes, which is why its key to see if its still developing a robust eye at the same period. Heres a nice dprog/dt animation of the last few model cycles. If anything, it has trended stronger as the hour selected here (05z... 1am) is moving closer and closer to real time. The overall forecast motion seems to also be slowing given that its shifted to the south and east form the initial 14 hour forecast.

dprog_dt_hrrr.gif

Looking at the later frames of the 21UTC version, it's interesting as it starts to align it more North-South with outflow channels to the south and north. As opposed to it's current east-west squished look. I think it's clear that some major reorganization is going to occur b/n now and daybreak. I think that is partly due to the interaction w/ the incoming trough. I think we'll see a nice feathery cirrus look over the east coast and midwest tomorrow.

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No....that is just the cirrus anvils from the new thunderstorms near the center....the eye's diameter is measure at a much lower level and is listed as about 20-25 miles.

Good call. But there are definitely cold top storms erupting around the center at this time. Let's see if they persist and start to encircle the center.

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It has shallow convection around the entire eye. The IR can't see it but the recent microwave passes have confirmed this. Yes, the eye itself is poorly defined, but the inner core as a whole has continued to steadily organize.

Also, the track appears to be almost 100 km east of the NHC forecast.

Exactly. Just because right at this moment there aren't cold tops completely encircling the center doesn't mean it can't have a well developed circulation with increased organization of the overall system. But obviously if further significant intensification is going to occur that will need to happen.

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18z GFDL is considerably stronger near the Miss. delta:

18zgfdl500mbHGHTPMSL036.gif

Yeah, FWIW, I think this is by far the strongest run of the GFDL while Isaac has been in the Gulf. Looks like it bottoms out around 963 mb with around 90 kt winds. It had been having trouble even getting it to cat 1 before this run as far I have seen.

Also interesting to note how impressive and large Isaac's wind field is. Just noted that on the way home the USAF plane reported flight level winds at 850 mb of 65 kt with unflagged SFMR of nearly 50 kt just off the LA bird's foot.

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I live just north of greenville,nc (90 miles from coast), had over 14inches of rain from Irene and lost 3 trees, one was oak tree over 80 years old. No power for over 36 hours. Call it what you want, but we still have people that have not recovered from that "tropical storm" a year later....

sorry, not trying to derail thread, just stating facts.

http://www.accuweath...top-ten-1/54348

No one was making light of the fact that Irene did significant damage up and down the east coast. They were merely pointing out that while Irene did have a very low central pressure as a tropical storm at landfall, it had weakened from a Category 3 hurricane. Isaac is much different in that it has a unusually low pressure for a tropical storm that has not yet reached hurricane strength.

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Storm still looks pretty awful on satellite.

It might not look great, but its actually very comparable to what the HRRR is depicting in the near future.

For example. Current Infrared:

2m5fr5y.png

Lets compare that to the HRRR OLR valid for 7z:

i41ste.png

eerily similar right?... although this is suppose to be 5 hours in the future. If we go forward to the end of the most recent HRRR run you get something like this.

1z20r3l.png

So yes, not a great presentation right now, but it could be the beginning of substancial banding we need on satellite imagery to mix out of the rest of this possible dry air.

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