Isabel fighting like hell ...

[Stormsfury]

Latest RECON fix shows a 2 mb drop down to 953 mb, and the eye is open S-SE. The eye has shrunk 5 miles since the last fix and convection is initiating along the northern and NW flank.

982
URNT12 KNHC 172344
VORTEX DATA MESSAGE
A. 17/2344Z
B. 31 DEG 25 MIN N
73 DEG 29 MIN W
C. 700 MB 2688 M
D. NA
E. NA
F. 225 DEG 97 KT
G. 133 DEG 073 NM
H. 953 MB Down 2 MB since the last fix 2 hours ago.
I. 15 C/ 3056 M
J. 17 C/ 3050 M
K. 12 C/ NA
L. OPEN S-SE
M. C45 5 NM smaller than the last fix.
N. 12345/7
O. .1 /2 NM
P. AF977 2313A ISABEL OB 05
MAX FL WIND 97 KT SE QUAD 2323Z. (Measured where the eyewall is open)

Dry air has been a problem BUT Isabel is vigorously fighting ... A huge plume of dry air will eventually sneak into Isabel, but IMO, it has some time beforehand to regain more convection. Obviously, Isabel has been bursting off and on.

How Isabel responds to the dry air entrainment and the counteracting Gulf Stream, and better established outflow is crucial to the intensity of Isabel at landfall. The absolute nightmare is the deeper convection reestablishing itself in the coming hours just before landfall and with the RECON's reports of a very strong wind field at flight level but a lack of deep convection to mix sustained winds down to the surface, a reestablishment of sustainable deep convection around the eyewall would increase sustained winds by 10 mph immediately at the surface and COULD POSSIBLY increase another 10 mph-15 mph sustained just before landfall. This is the worse case scenario.

WV Loop
http://hadar.cira.colostate.edu/ramsdis ... geir3.html

IMO, Isabel will be a CAT 3 at landfall ... probably 115 mph ... based on four factors ...two positive, two negative ...

Pluses

1) Gulf Stream / SST's
2) Decent Outflow on the northern semicircle

Negatives

1) Dry air entrainment
2) Large envelope of winds and not enough time to consolidate

[PuertoRicoLibre]

Don't you think they should be more conservative and flatly state it is already a minimum Cat. 3?

[wxman57]

Good analysis, SF, but I think the four factors will balance out to a draw. Isabel appears to be too spread out to consolidate before landfall. We'll probably see periods of convection near the center as we have for the past 24-36 hours but it probably won't be able to persist for long enough.

[wow]

I sure hope a tree doesn't come falling on my car tomorrow.

[coriolis]

As I'm looking at the satellite images, the Isabel appears to be strongest in the NW quadrant. That part of the storm is presently over the Gulf Stream, isn't it? That would support the idea of intensification as the center passes over the Gulf Stream.

[wxman57]

New vortex is in, no real change. Pressure up 3 mb, FL wind 97kts. No sign of those 121kt winds from earlier today. If 97 kts is all they can find, then surface winds are probably down to 90 mph or possibly less. Dry air appears to be winning the tug-of-war tonight. Still about 16 hours or so until the center reaches the coast, but outer bands are already moving into the coast. I'm wondering if the recon has also be overestimating the surface winds away from the center of if they've been dropping dropsondes to fix all the wind radii. Highest winds I've seen around the perimeter of the storm have been about 40kts today, but there are no buoys close to the center - yet.

URNT12 KNHC 180117
VORTEX DATA MESSAGE
A. 18/0117Z
B. 31 DEG 38 MIN N
73 DEG 38 MIN W
C. 700 MB 2699 M
D. NA
E. NA
F. 307 DEG 85 KT
G. 225 DEG 041 NM
H. 956 MB
I. 14 C/ 3035 M
J. 17 C/ 3062 M
K. 13 C/ NA
L. OPEN S-SW
M. C25
N. 12345/7
O. .1 /2 NM
P. AF977 2313A ISABEL OB 12
MAX FL WIND 97 KT SE QUAD 2323Z. MAX FL TEMP 17C 226/036NM FROM
FL CNTR.

[Bane]

Eye has contracted to 25 miles.

[wxman57]

Eye has contracted to 25 miles.

It's not much of an eye though. Just an open ring of relatively weak convection. The convection that fired up north of the center an hour ago has dissipated.

[Stormsfury]

I noticed that Isabel based on RECON fixes appears to be moving NW now. The eye was 45 nm earlier, and now down to 25 mb.

http://hadar.cira.colostate.edu/ramsdis ... geir4.html

Looking at the latest IR loop, I cannot help but think that the deeper moisture ahead is just about to give Isabel a boost after this latest wind down. Another area just to the NW is flaring up but a little away from the center.

Side note
Earlier the eye was C50 and closed. Then it was 45 nm, and open S-SE, and the last fix was open S-SW ... warmest flight level temp SW of the center at 17 C ...

SF

[Stormsfury]

Isabel's still fighting ...

Convection has now wrapped all the way around the center. RECON found a slight drop (1 mb) at 955mb, and a circular 30 NM eye... although open S-SW and the winds are up at flight level to 109 kts.

http://hadar.cira.colostate.edu/ramsdis ... geir4.html

URNT12 KNHC 180401
VORTEX DATA MESSAGE
A. 18/0400Z
B. 32 DEG 06 MIN N
73 DEG 55 MIN W
C. 700 MB 2703 M
D. NA
E. NA
F. 137 DEG 109 KT
G. 043 DEG 050 NM
H. 955 MB
I. 14 C/ 3068 M
J. 16 C/ 3081 M
K. 13 C/ NA
L. OPEN S-SW
M. C30
N. 12345/7
O. .1 /1 NM
P. AF977 2313A ISABEL OB 23
MAX FL WIND 109 KT NE QUAD 0346Z.

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