CPAC: DARBY - Post-Tropical

[Kingarabian]

CPHC keeps it at 999mb and 50kts.

Also they keep the same track. Well east of the guidance majority.

[Kingarabian]

[cycloneye]

URPN15 KNHC 222052
AF308 0105E DARBY HDOB 32 20160722
204330 1803N 15121W 8277 01699 0067 +157 +151 314025 025 032 000 00
204400 1802N 15122W 8277 01700 0069 +153 //// 316026 026 032 000 01
204430 1801N 15124W 8275 01703 //// +151 //// 317027 028 032 000 01
204500 1800N 15125W 8277 01704 0071 +159 +151 319029 029 031 000 00
204530 1759N 15126W 8275 01705 0073 +156 +150 321030 030 030 000 00
204600 1758N 15127W 8277 01706 //// +151 //// 322030 030 030 000 05
204630 1757N 15129W 8274 01710 //// +150 //// 322028 029 029 000 01
204700 1755N 15130W 8277 01709 //// +150 //// 322028 028 029 000 01
204730 1754N 15131W 8275 01711 0082 +151 +148 321027 028 029 000 03
204800 1753N 15132W 8275 01714 0085 +150 +147 322027 027 030 000 03
204830 1752N 15134W 8275 01712 0087 +150 +147 323028 028 030 000 00
204900 1751N 15135W 8277 01712 0088 +150 +147 324028 028 030 000 00
204930 1750N 15136W 8276 01715 0084 +156 +145 325026 027 031 000 00
205000 1749N 15138W 8277 01715 0085 +158 +144 326029 029 031 000 03
205030 1748N 15139W 8275 01717 0088 +156 +144 327028 028 030 000 03
205100 1746N 15140W 8277 01715 0090 +153 +149 325028 029 029 000 03
205130 1745N 15141W 8275 01718 0087 +159 +147 321024 026 028 000 00
205200 1744N 15143W 8277 01717 0088 +156 +146 331026 027 028 000 00
205230 1743N 15144W 8277 01718 //// +149 //// 331025 026 029 000 01
205300 1742N 15145W 8277 01718 0091 +154 +150 328025 026 029 000 03
$$
;

[cycloneye]

Mission is over.

[cycloneye]

TROPICAL STORM DARBY DISCUSSION NUMBER 45
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP052016
1100 AM HST FRI JUL 22 2016

Deep convection associated with Darby was mainly in the
system's northern semicircle with persistent tops colder than
-70C. An SSMIS pass from 1732 UTC indicated the system was tilted
toward the east. The first Air Force Reserve 53rd Weather
Reconnaissance Squadron mission into Darby found maximum SFMR winds
of just over 50 knots but the initial passes had difficulty
determining the location of the low level center. Based on the
recon data thus far, the tropical storm force radius was expanded
slightly in the northern semicircle and Darby has been held at 50
kt for this advisory package.

Darby is estimated to be moving at 270/10 kt to the south of a
ridge. This ridge is forecast to weaken due to a low pressure system
digging southward to the north of Darby. This is expected to
decrease the forward motion over the next day, and increase the
amount of vertical shear on the tropical cyclone this weekend. The
trusted objective aids are consistent with this scenario but have
shifted southward slightly with some solutions indicating landfall
over the Big Island. As a result, the current forecast has been
shifted southward a bit and is between the dynamical consensus and
the previous forecast. Given current guidance trends, a direct
impact on the Big Island and Maui is a distinct possibility this
weekend.

The main factors affecting the intensity forecast include marginal
sea surface temperatures, the amount and timing of vertical wind
shear, and the effects of any potential interactions with the
Hawaiian Islands. Sea surface temperatures will remain marginal near
26.5C over the next couple of days but vertical shear is expected to
increase as the previously mentioned upper level trough digs farther
south. This shear increase is not expected to be significant until
later this weekend. Thus, the forecast is close to the previous
package which has Darby only slowly weakening and maintains the
cyclone as a tropical storm through the weekend. This is close to
the intensity consensus guidance. Note that interactions with the
main Hawaiian Islands may cause significant disruptions to Darby and
so the intensity forecast confidence is not high at this time.

Interests outside of the warning areas in the Hawaiian islands
should monitor the progress of Darby, as it could eventually have
impacts on all islands through early next week. Remember, it is
important not to focus too closely on the exact track and intensity
forecasts because the average track error 72 hours out is near 100
miles, while the average intensity error is about 15 kt. In
addition, the hazards of a tropical cyclone can extend over a broad
area well away from the center.


FORECAST POSITIONS AND MAX WINDS

INIT 22/2100Z 18.5N 151.0W 50 KT 60 MPH
12H 23/0600Z 18.8N 152.5W 50 KT 60 MPH
24H 23/1800Z 19.4N 154.4W 45 KT 50 MPH
36H 24/0600Z 20.4N 155.7W 45 KT 50 MPH
48H 24/1800Z 21.4N 156.9W 40 KT 45 MPH
72H 25/1800Z 23.8N 159.3W 40 KT 45 MPH
96H 26/1800Z 26.0N 161.5W 35 KT 40 MPH
120H 27/1800Z 30.0N 162.5W 30 KT 35 MPH

$$
Forecaster Kodama

[Kingarabian]

18z GFS drops this to 997mb.

[Kingarabian]

Sustaining convection a lot better than yesterday.

WTPA33 PHFO 222356
TCPCP3

BULLETIN
TROPICAL STORM DARBY INTERMEDIATE ADVISORY NUMBER 45A
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP052016
200 PM HST FRI JUL 22 2016

...DARBY STILL MOVING WEST TOWARDS THE BIG ISLAND...


SUMMARY OF 200 PM HST...0000 UTC...INFORMATION
----------------------------------------------
LOCATION...18.5N 151.6W
ABOUT 240 MI...390 KM ESE OF HILO HAWAII
ABOUT 450 MI...720 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 12 MPH...19 KM/H MINIMUM
CENTRAL PRESSURE...1000 MB...29.53 INCHES

WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm warning is in effect for...
* Hawaii County
* Maui County, including the islands of Maui, Molokai, Lanai and
Kahoolawe

A Tropical Storm Warning means that tropical storm conditions are
expected within the warning area within 36 hours.

Interests elsewhere in the Hawaiian Islands should monitor the
progress of Darby. Watches and warnings may be required for
additional islands later today or tonight.

For storm information specific to your area, please monitor
products issued by the National Weather Service office in
Honolulu Hawaii.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 200 PM HST (0000 UTC), the center of Tropical Storm Darby was
located near latitude 18.5 North, longitude 151.6 West. Darby is
moving toward the west near 12 mph (19 km/h). Darby's forward
motion is expected to slow slightly Saturday followed by a turn
toward the northwest on Saturday night. On the forecast track, the
center of Darby is forecast to pass over or near the Big Island
on Saturday and Maui on Saturday night.

Maximum sustained winds are near 60 mph (95 km/h) with higher gusts.
Some weakening is forecast during the next 48 hours.

Tropical-storm-force winds extend outward up to 125 miles (205 km)
from the center.

The estimated minimum central pressure is 1000 mb (29.53 inches).


HAZARDS AFFECTING LAND
----------------------
WIND: Tropical-storm-force winds are expected over the Big Island
starting late tonight, and over portions of Maui County on Saturday.

SURF: Swells generated by Darby are expected to impact the
Hawaiian Islands over the next couple of days, possibly becoming
damaging along some coastlines through Saturday.

RAINFALL: Storm total rainfall of 10 to 15 inches with locally
higher amounts, could cause life-threatening flash floods as well as
landslides.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM HST.

$$
Forecaster Kodama

[Yellow Evan]

Darby looks ok, but I question how well stacked the system is. If this can become better stacked vertically, some deepening can not be ruled out as waters warm.

[cycloneye]

TROPICAL STORM DARBY DISCUSSION NUMBER 46
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP052016
500 PM HST FRI JUL 22 2016

Tropical Storm Darby is very asymmetric in the satellite images this
afternoon with deep convection mainly within a band wrapping around
its western semicircle. This was also seen in the 2231 UTC GPM
pass, along with a separate rainband southeast of the center. High
clouds have been streaming toward the northeast which indicates the
cyclone is beginning to feel an approaching upper level trough. One
of the later passes through Darby by the 53rd Weather Reconnaissance
Squadron's WC-130J helped confirm the center position of the system
toward the end of the morning mission though the aircraft had to fly
lower to find it. Based on the morning recon mission and the
maintenance of deep convection, the initial intensity has been held
at 50 kt. Note that this is higher than the subjective Dvorak
estimates of 45 kt from PHFO and SAB, and 30 kt from JTWC. The next
aircraft mission into Darby is scheduled for this evening.

Darby is estimated to be moving at 280/11 kt to the south of a
ridge. This ridge is forecast to weaken due to a low pressure system
digging southward to the north of cyclone. This weakness is expected
to decrease Darby's forward motion over the next day, and increase
the amount of vertical shear affecting the system this weekend. The
trusted dynamical models have remained largely consistent today,
bringing Darby over the Big Island on Saturday. Thus, the current
forecast has been nudged southward closer to the dynamical consensus
with a landfall on the Big Island, followed by a path over Maui
County and near Oahu. The latter part of this path assumes that
Darby survives its impact on the Big Island which is not a certainty.

The intensity forecast rationale remains the same since the last
package. The main factors affecting the intensity forecast include
marginal sea surface temperatures, the amount and timing of vertical
wind shear, and the effects of any potential interactions with the
Hawaiian Islands. Sea surface temperatures will remain marginal near
26.5C over the next couple of days but vertical shear is expected to
increase as the previously mentioned upper level trough digs farther
south. This shear increase is not expected to become strong
until later this weekend. The forecast calls for only slow
weakening with Darby maintaining tropical storm strength through
the weekend. This is consistent with the previous package but
slightly lower than the intensity consensus. Interactions with the
Big Island may cause significant disruptions to Darby so the
intensity forecast confidence is not high at this time.

The expected movement of Darby, as well as the latest wind
probability guidance, warrants the issuance of a Tropical Storm
Watch for the island of Oahu with this package.

Interests on Kauai and the Papahanaumokuakea Marine National
Monument should continue to monitor the progress of Darby. Remember,
it is important not to focus too closely on the exact track and
intensity forecasts because the average track error 72 hours out is
near 100 miles, while the average intensity error is about 15 kt. In
addition, the hazards of a tropical cyclone can extend over a broad
area well away from the center.



FORECAST POSITIONS AND MAX WINDS

INIT 23/0300Z 18.7N 152.1W 50 KT 60 MPH
12H 23/1200Z 18.9N 153.5W 50 KT 60 MPH
24H 24/0000Z 19.4N 154.7W 45 KT 50 MPH
36H 24/1200Z 20.2N 155.8W 45 KT 50 MPH
48H 25/0000Z 21.2N 157.1W 40 KT 45 MPH
72H 26/0000Z 23.5N 160.0W 40 KT 45 MPH
96H 27/0000Z 27.0N 163.0W 35 KT 40 MPH
120H 28/0000Z 31.0N 165.6W 30 KT 35 MPH

$$
Forecaster Kodama

[Aric Dunn]

Looking like from available data its south of the forecast track.. looks like it should come in right near the radar site actually.. makes it worse of a flash flood hazard..

[stormwise]

looks open i think.

[Kingarabian]

The sun sets and Darby begins to struggle:

[cycloneye]

TROPICAL STORM DARBY DISCUSSION NUMBER 47
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI EP052016
1100 PM HST FRI JUL 22 2016

Darby's satellite presentation continues to be messy, with deep
convection now on the decline and beginning to wrap around the
south and southwest quadrants. Cloud tops have warmed over the past
six hours and the best outflow continues to be toward the
northeast, consistent with southwesterly shear near 10 kt depicted
by SHIPS. The 53rd Weather Reconnaissance Squadron's WC-130J
aircraft did a fine job this evening finding the center of this
system, so we are confident we know where Darby is and how it is
moving. Based on aircraft SFMR data from the first pass through the
center, we will keep an initial intensity of 50 kt for this
advisory. Like before, this is higher than the objective Dvorak
satellite intensity estimates from the three satellite analysis
centers (HFO, JTWC and SAB). These range from 30 kt to 45 kt.
Interestingly, an 0630 UTC ASCAT pass only found 35 kt within the
northeast quadrant. The next aircraft reconnaissance mission into
Darby will be Saturday morning.

Initial motion is 280/09 kt as Darby slowly gains latitude along the
southern flank of a subtropical ridge. Low pressure farther to the
north is expected to dig southward, weakening the ridge. This will
simultaneously slow Darby's forward motion and deflect it to a more
northwesterly track. Vertical wind shear will also increase,
especially after 18 hours according to SHIPS, likely leading to
gradual weakening from 24 hours and beyond. Track guidance has
changed very little over the past 6 to 12 hours, depicting a gently
curving path across the main Hawaiian Island chain. The forecast
for this advisory track has changed very little and remains well
within the tightening guidance envelope and close to TVCN consensus.
This track takes Darby directly across the Big Island of Hawaii
between 12 and 24 hours.

The intensity forecast is based on the gradual toll that increasing
vertical shear will take on Darby, overtaking any sustaining
effects from marginal sea surface temperatures. However, this shear
is not expected to become strong until day 2. The forecast
calls for slow weakening with Darby maintaining tropical storm
strength through the weekend. This is consistent with the previous
package and represents a compromise between SHIPS, which weakens
DARBY quickly, and GHMI, which keeps Darby as a strong tropical
storm through day 5. It is important to note that weakening
due to land interaction has so far been ignored for that portion of
the track beyond the Big Island.

Interests outside of the watch and warning areas in the Hawaiian
Islands should continue to monitor the progress of Darby. Remember,
it is important not to focus too closely on the exact track and
intensity forecasts because the average track error 72 hours out is
near 100 miles, while the average intensity error is about 15 kt. In
addition, the hazards of a tropical cyclone can extend over a broad
area well away from the center.

FORECAST POSITIONS AND MAX WINDS

INIT 23/0900Z 18.8N 153.0W 50 KT 60 MPH
12H 23/1800Z 19.1N 154.4W 50 KT 60 MPH
24H 24/0600Z 19.8N 155.7W 45 KT 50 MPH
36H 24/1800Z 20.6N 156.7W 40 KT 45 MPH
48H 25/0600Z 21.7N 158.0W 40 KT 45 MPH
72H 26/0600Z 24.3N 160.8W 40 KT 45 MPH
96H 27/0600Z 27.6N 163.7W 35 KT 40 MPH
120H 28/0600Z 31.9N 166.3W 30 KT 35 MPH

$$
Forecaster Powell

[stormwise]

2016JUL23 093000 2.3 1006.9 33.0 1.8 1.5 1.5 NO LIMIT ON FLG 15.64 -14.64 SHEAR N/A -8.5 18.76 153.17 FCST GOES15 30.2
2016JUL23 090000 2.3 1006.9 33.0 1.9 2.1 2.1 NO LIMIT ON FLG 15.04 -15.10 CRVBND N/A -8.5 18.75 153.09 FCST GOES15 30.1
2016JUL23 083000 2.3 1006.9 33.0 1.9 1.6 1.5 0.5T/hour ON FLG 11.24 -14.41 SHEAR N/A -8.5 18.80 153.05 FCST GOES15 30.1
2016JUL23 080000 2.3 1006.9 33.0 2.0 1.7 1.5 0.5T/hour ON FLG 6.74 -14.09 SHEAR N/A -8.5 18.79 152.98 FCST GOES15 30.1

[cycloneye]

 https://twitter.com/MikeAdcockWx/status/756823169290293249

[NDG]

There's no way Darby still has 60 mph winds this morning.
They are being too aggressive with it, keeping it as a TS as it tracks through the Islands. IMO.

[wxman57]

There's no way Darby still has 60 mph winds this morning.
They are being too aggressive with it, keeping it as a TS as it tracks through the Islands. IMO.

Most agencies (like CPHC) don't like to acknowledge weakening prior to landfall. They don't want the general public to "relax" just in case there's a sudden intensification before landfall. That ASCAT is very representative of what the recon plane found yesterday, with the exception of a tiny area of squalls that generated a few 50kt 10-sec wind gusts. ASCAT isn't that finely-detailed. General winds around Darby are in the 30-35 mph range.

[Alyono]

better organized this morning on radar. I'd expect winds of 45 kts at landfall in a small area. Main threat remains rainfall

[NDG]

Darby looks a little better on radar than on Satellite this morning.

[JtSmarts]

Iselle made landfall with 45 kt winds I believe. Is Darby more or less organized than Iselle was?