CPAC: DARBY - Post-Tropical

[Kingarabian]

Not sure if it's a hurricane or not.

[NDG]

Still suffering from slight northeasterly shear and dry air intrusion, IMO.

[Alyono]

Not sure if it's a hurricane or not.

I do not beleive it is. The microwave signature is that of a 50-55 kt TS. I do not understand why the winds are being increased

[cycloneye]

HURRICANE DARBY DISCUSSION NUMBER 10
NWS NATIONAL HURRICANE CENTER MIAMI FL EP052016
900 PM MDT WED JUL 13 2016

Darby has developed a large CDO pattern and a 2314Z SSMI/S microwave
pass indicated a 15-20 nmi diameter eye embedded in the center of
the central dense overcast. Subjective intensity estimates are a
consensus T4.0/65 kt from TAFB and SAB, and the latest UW-CIMSS ADT
and AMSU estimates were T4.4/75 kt and 72 kt, respectively. The
advisory intensity of 70 kt is based on an average of these values.

The initial motion estimate is 280/10 kt. The expansive deep-layer
ridge to the north of Darby is forecast by the global models to
remain entrenched across the eastern and central Pacific for the
next several days, which should act to keep Darby moving in a
general westerly direction throughout the 5-day forecast period.
Other than some differences in forward speed, there remains very
little cross-track difference noted among the more reliable models.
The new official track forecast is essentially just an extension of
the previous advisory track, and lies close to a consensus of the
GFS and ECMWF model solutions.

Darby is expected to encounter the most favorable combination of
atmospheric and oceanic conditions during the next 24 hours or so,
and steady intensification is forecast as a result during that time.
By 36-48 h, Darby will be moving across cooler SSTs near 26 deg C
and into a drier airmass, so leveling off of the intensity is
expected. Steady weakening is forecast to begin after that time as
the hurricane moves over 25-26 deg C SSTs. However, the weakening
rate is expected to be a little slower than normal due to low
vertical wind shear conditions that both the GFS and ECMWF models
are forecasting to affect Darby between 72-120 h. The new NHC
intensity forecast is similar to the previous forecast, and closely
follows the SHIPS intensity forecast guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 14/0300Z 15.6N 114.6W 70 KT 80 MPH
12H 14/1200Z 15.9N 116.5W 80 KT 90 MPH
24H 15/0000Z 16.3N 119.0W 90 KT 105 MPH
36H 15/1200Z 16.7N 121.5W 90 KT 105 MPH
48H 16/0000Z 17.0N 123.6W 85 KT 100 MPH
72H 17/0000Z 17.5N 127.6W 70 KT 80 MPH
96H 18/0000Z 18.1N 131.6W 60 KT 70 MPH
120H 19/0000Z 18.9N 136.4W 50 KT 60 MPH

$$
Forecaster Stewart

[Alyono]

what microwave did NHC see? From the TCD

"Darby has developed a large CDO pattern and a 2314Z SSMI/S microwave
pass indicated a 15-20 nmi diameter eye embedded in the center of
the central dense overcast"

Maybe I need a new pair of glasses. That does not look like the eye is in the middle of the CDO on the microwave

[TropicalAnalystwx13]

Are people really questioning whether this is a hurricane or not?

[Yellow Evan]

Not sure if it's a hurricane or not.

I do not beleive it is. The microwave signature is that of a 50-55 kt TS. I do not understand why the winds are being increased

I respectfully disagree. Given the partially closed ring on microwave and a DT of T4.5 from SAB and CMISS ADT estimates of T4.3, I think 70 knots is fair. Yes, there is a slight sheared appearance, hence why all the upper level outflow is equatorial and yes there is a small high basis at this Dvorak range, however.

[stormwise]

Multiplatform Tropical Cyclone Surface Winds Analysis.


I know its JTWC

Advanced Dvorak Technique (v8.1.4)
2016JUL14 010000 4.5 981.5 77.0 4.5 4.5 3.8 MW ON OFF OFF -68.46 -65.29 UNIFRM N/A 30.5 15.47 114.36 FCST GOES15 29.9

[Yellow Evan]

what microwave did NHC see? From the TCD

"Darby has developed a large CDO pattern and a 2314Z SSMI/S microwave
pass indicated a 15-20 nmi diameter eye embedded in the center of
the central dense overcast"

Maybe I need a new pair of glasses. That does not look like the eye is in the middle of the CDO on the microwave

Here's where the NHC has the center. It's not in the middle of the CDO but not exactly on the edge either.

[Alyono]

Are people really questioning whether this is a hurricane or not?

yeah, we are. If I were forecasting tonight, I would have given a microwave Dvorak of 3.5 (yes, we have a technique to do Dvoraks on microwave where I work). I'd have split the difference and went 65 kts, however

[TropicalAnalystwx13]

Are people really questioning whether this is a hurricane or not?

yeah, we are. If I were forecasting tonight, I would have given a microwave Dvorak of 3.5 (yes, we have a technique to do Dvoraks on microwave where I work). I'd have split the difference and went 65 kts, however

There are several issues with that, the foremost being accuracy. If the NHC doesn't have enough confidence in crafting a Dvorak scale based on microwave, why does your work?

Darby's current satellite presentation looks between a T4.0 and T4.5. SAB and TAFB at 65kt (SAB DT is actually T4.5), UW-CIMSS ADT at 77kt, and CIMSS AMSU at 72kt blends well to 70kt.

[Kingarabian]

Are people really questioning whether this is a hurricane or not?

[img]http://i.imgur.com/axrm9O7.gif[/mg]

That almost looks like a CCC. Which is why it hasn't intensified much.

I respectfully disagree. Given the partially closed ring on microwave and a DT of T4.5 from SAB and CMISS ADT estimates of T4.3, I think 70 knots is fair. Yes, there is a slight sheared appearance, hence why all the upper level outflow is equatorial and yes there is a small high basis at this Dvorak range, however.

I remember there would be clear cut closed rings on MW and the NHC would refuse to classify the storm as a hurricane. And the MW appearance is not that impressive.

[Yellow Evan]

I remember there would be clear cut closed rings on MW and the NHC would refuse to classify the storm as a hurricane. And the MW appearance is not that impressive.

At least the eye feature on microwave has been persistent, unlike those quick fire tropical cyclones like Kevin last season that the NHC never brough above 50 knots despite a microwave eye.

[Alyono]

Are people really questioning whether this is a hurricane or not?

yeah, we are. If I were forecasting tonight, I would have given a microwave Dvorak of 3.5 (yes, we have a technique to do Dvoraks on microwave where I work). I'd have split the difference and went 65 kts, however

There are several issues with that, the foremost being accuracy. If the NHC doesn't have enough confidence in crafting a Dvorak scale based on microwave, why does your work?

Darby's current satellite presentation looks between a T4.0 and T4.5. SAB and TAFB at 65kt (SAB DT is actually T4.5), UW-CIMSS ADT at 77kt, and CIMSS AMSU at 72kt blends well to 70kt.

accuracy with a microwave Dvorak? It produces MORE accurate results from what we have found. It is proprietary, however so no, I am not sharing the technique. It has been used successfully world wide and I have found it more accurate with compared to recon than IR

[Kingarabian]

MUCH better.

[Alyono]

agreed! MUCH better. That microwave does justify 70 kts

[Yellow Evan]

Looks about ready to take off.

[1900hurricane]

That dry air wrap is still pretty pronounced though. I imagine it's going to continue limiting the rate of intensification for the time being. If it weren't for that, Darby probably would have been a fair bit more intense by now.

[Yellow Evan]

Code: Select all

             ----- Current Analysis -----
     Date :  14 JUL 2016    Time :   033000 UTC
      Lat :   15:37:00 N     Lon :  114:42:09 W

     
                CI# /Pressure/ Vmax
                4.6 / 979.5mb/ 79.6kt

     
             Final T#  Adj T#  Raw T#
                4.6     4.6     3.8

 Center Temp : -61.2C    Cloud Region Temp : -63.2C

 Scene Type : UNIFORM CDO CLOUD REGION w/ MW EYE

 Positioning Method : FORECAST INTERPOLATION


[Kingarabian]

Looks like the 00z GFS is just south of the big island. Odd looking as well because it carefully rounds the south of the big island and then shoots up as it passes the big island.