CPAC: ISELLE - Post-Tropical

[Kingarabian]

Why are they dropping the intensity?

SAB gives at a 4.5, but TAFB has 5.5, and ADT has 6.0.

Eye is well defined, has really warmed and microwave imagery shows a core enough organized to match a cat.3 storm.

[Alyono]

Those models seem to be overdeveloping the system south of Hawaii/ It's causing Iselle to move farther north

[Yellow Evan]

Why are they dropping the intensity?

Cloud tops are warming.

[Kingarabian]

[cycloneye]

HURRICANE ISELLE DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL EP092014
800 PM PDT SUN AUG 03 2014

Iselle's satellite appearance has essentially been steady state
since the last advisory. The cyclone continues to exhibit many of
the characteristics of an annular hurricane, with a nearly
axisymmetric convective structure and a curious lack of convective
features outside the well-defined cental dense overcast. A circular
but cloud-filled 20-25 n mi wide eye is also evident in last-light
visible imagery. The initial intensity is reduced only slightly to
95 kt in accordance with the latest CI numbers from TAFB and SAB.

The initial motion estimate is a steady 280/10, with perhaps more of
a due-west wobble during the last couple of hours. A mid-latitude
trough extending southwestward along 130w is forecast to weaken the
subtropical ridge north of Iselle during the next 24 hours. The
effect of the weakened ridge should be a decrease in the cyclone's
forward motion for a brief period during the next day or two as it
approaches 140w. By day 3, the cyclone should find itself south of
a newly established central Pacific ridge, which should steer Iselle
west-northwestward at a considerably faster forward speed by days
4-5. The track forecast is little changed from the previous one
and is in the middle of the guidance envelope, very close to the
multi-model consensus TVCE.

Even though Iselle is moving over marginally warm sea surface
temperatures, its current annular structure in a very light-shear
environment suggests that the cyclone might retain a higher
intensity than the guidance might suggest if the large-scale
environmental conditions do not vary much at least during the next
day or possibly two. After that, significantly less favorable
thermodynamic factors, such as increasingly drier and more stable
air and water temperatures just below 26C, should result in
weakening while Iselle nears the Hawaiian Islands. An accelerated
weakening may take place as Iselle makes its closest approach to the
Hawaiian chain when environmental conditions become even more
hostile. The intensity forecast is about the same as the previous
one and is near the multi-model consensus IVCN and the SHIPS/LGEM
output.


FORECAST POSITIONS AND MAX WINDS

INIT 04/0300Z 15.9N 134.8W 95 KT 110 MPH
12H 04/1200Z 16.0N 136.2W 90 KT 105 MPH
24H 05/0000Z 16.0N 137.8W 85 KT 100 MPH
36H 05/1200Z 16.0N 139.3W 80 KT 90 MPH
48H 06/0000Z 16.5N 141.3W 75 KT 85 MPH
72H 07/0000Z 18.1N 146.8W 60 KT 70 MPH
96H 08/0000Z 20.1N 153.1W 45 KT 50 MPH
120H 09/0000Z 22.3N 159.2W 40 KT 45 MPH

$$
Forecaster Kimberlain

[supercane4867]

AHI has rised from a marginal 1 to 3 in the 00z SHIPS data. I wonder what it takes to reach 100

## ANNULAR HURRICANE INDEX (AHI) EP092014 ISELLE 08/04/14 00 UTC ##
## PASSED SCREENING STEP, MIGHT BE ANNULAR, CALCULATE AHI FROM DISCRIMINANT ANALYSIS ##
## AHI= 3 (AHI OF 100 IS BEST FIT TO ANN. STRUC., 1 IS MARGINAL, 0 IS NOT ANNULAR) ##

[Kingarabian]

[supercane]

Solid ring on microwave:

[Kingarabian]

110 mph storm?

[TropicalAnalystwx13]

Definitely starting to take on annular characteristics this evening.

[Yellow Evan]

110 mph storm?

I'd go with 100 knts personally, but keep in mind, cloud tops are not that cold.

[Kingarabian]

Wow.

[TropicalAnalystwx13]

110 mph storm?

It's a tough one. The eye is warming and the storm has great structure, but an increasingly marginal environment is moderating eyewall convection generally warmer than -65C. In the absence of recon, we'll never know its current strength.

[Yellow Evan]

110 mph storm?

It's a tough one. The eye is warming and the storm has great structure, but an increasingly marginal environment is moderating eyewall convection generally warmer than -65C. In the absence of recon, we'll never know its current strength.

Recon is a couple days away, but won't porbs be this strong by that time.

Emilia 12 looked like this when it was 95 knts.

Epsilon 05 in the ATL was 75 knts, but that had a beyond terrible IR presentation and was super shallow.

[Cyclenall]

Definitely starting to take on annular characteristics this evening.

*Image Cut*

Yes its transforming into an annular hurricane now. It was easy to predict due to the conditions ahead.

It's a tough one. The eye is warming and the storm has great structure, but an increasingly marginal environment is moderating eyewall convection generally warmer than -65C. In the absence of recon, we'll never know its current strength.

Someone nudge the NHC to pull recon on it, its heading for Hawaii after all. Let's pretend its going to be a big deal just to get more recon data on forming annular storms . Warmer cloud tops seems to go hand in hand with A word TC's so it could be strengthening quickly right now without much notice.

[Kingarabian]

Deep convection around the eye is back in play.

[Kingarabian]

Definitely starting to take on annular characteristics this evening.

*Image Cut*

Yes its transforming into an annular hurricane now. It was easy to predict due to the conditions ahead.

It's a tough one. The eye is warming and the storm has great structure, but an increasingly marginal environment is moderating eyewall convection generally warmer than -65C. In the absence of recon, we'll never know its current strength.

Someone nudge the NHC to pull recon on it, its heading for Hawaii after all. Let's pretend its going to be a big deal just to get more recon data on forming annular storms . Warmer cloud tops seems to go hand in hand with A word TC's so it could be strengthening quickly right now without much notice.

We should have a NOAA flight soon. AF Recon on Wednesday.

[Yellow Evan]

Someone nudge the NHC to pull recon on it, its heading for Hawaii after all. Let's pretend its going to be a big deal just to get more recon data on forming annular storms . Warmer cloud tops seems to go hand in hand with A word TC's so it could be strengthening quickly right now without much notice.

Recon goes out on Tuesday I think.

[Yellow Evan]

http://i.imgur.com/1NmElND.jpg

Deep convection around the eye is back in play.

Eye looks better defined as well.

[Kingarabian]

http://i.imgur.com/1NmElND.jpg

Deep convection around the eye is back in play.

Eye looks better defined as well.

It could be going through RI again. If that red circles the eye completely then we're going to be looking at a Cat.4. This is speaking from years of tracking hurricane intensities through the means of satellite imagery and no recon.

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