EPAC: DARBY - Advisories

[cycloneye]

BULLETIN
Hurricane Darby Advisory Number 20
NWS National Hurricane Center Miami FL EP052022
Issued by NWS Central Pacific Hurricane Center Honolulu HI
1100 PM HST Wed Jul 13 2022

...DARBY ENTERING THE CENTRAL PACIFIC AS A HURRICANE...
...RAPID WEAKENING ANTICIPATED SOON...


SUMMARY OF 1100 PM HST...0900 UTC...INFORMATION
-----------------------------------------------
LOCATION...16.2N 139.5W
ABOUT 1050 MI...1695 KM E OF HILO HAWAII
ABOUT 1250 MI...2015 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...110 MPH...175 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 15 MPH...24 KM/H
MINIMUM CENTRAL PRESSURE...971 MB...28.68 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 PM HST (0900 UTC), the center of Hurricane Darby was located
near latitude 16.2 North, longitude 139.5 West. Darby is moving
toward the west-northwest near 15 mph (24 km/h) and this motion is
expected to continue over the next 24 hours, followed by a turn to
the west thereafter.

Maximum sustained winds are near 110 mph (175 km/h) with higher
gusts. Significant weakening is forecast during the next 48
hours, and Darby is expected to become a post-tropical cyclone on
Friday before dissipating this weekend.

Hurricane-force winds extend outward up to 15 miles (30 km) from the
center and tropical-storm-force winds extend outward up to 45 miles
(75 km).

The estimated minimum central pressure is 971 mb (28.68 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
This is the last Public Advisory issued by the National Hurricane
Center on Darby. Future information on this system can be found in
Public Advisories issued by the Central Pacific Hurricane Center
beginning at 500 am HST Thursday, under AWIPS header HFOTCPCP1,
WMO header WTPA31 PHFO. Products will continue to be available on
the web at hurricanes.gov.

$$
Forecaster Birchard



Hurricane Darby Discussion Number 20
NWS National Hurricane Center Miami FL EP052022
Issued by NWS Central Pacific Hurricane Center Honolulu HI
1100 PM HST Wed Jul 13 2022

Darby's satellite presentation was still quite impressive near
analysis time this evening, with persistent cold cloud tops
surrounding a clear eye. However, some degradation in the cyclone's
appearance has been noted over the past couple of hours. The
eye has cooled and become a little elongated, and the cyclone
appears to be entraining environmental dry air, leading to
recently-observed breaks in the eye wall. The initial intensity is
estimated to be near 95 kt, representing a slight weakening from the
previous advisory, with Darby now below major hurricane strength.
This estimate is in line with a blend of the subjective Dvorak
intensity estimates from HFO/TAFB/SAB, the latest UW-CIMSS objective
Dvorak estimate of 95 kt, and a SATCON value of 97 kt.

Despite Darby holding its own over the past 24-36 hours,
significant weakening is anticipated over the next couple of days.
This is supported by all of the reliable guidance, with Darby
expected to dissipate by this weekend as it passes south of the
main Hawaiian Islands. The updated intensity forecast closely
follows the consensus IVCN, as well as the SHIPS guidance.

Darby lies on the southwestern periphery of a ridge aloft, in an
area characterized by light to moderate vertical wind shear. As
Darby is driven west-northwestward by a mid- and upper-level ridge
to the northeast in the short term, it will move closer to a
upper-level trough to it's northwest, into an environment
characterized by stronger vertical wind shear. This shear will
allow the cyclone to efficiently ingest the dry mid-level air that
prevails, while ths system moves over sub-26C SSTs. Darby is
expected to degrade to a shallow system over the next 48 hours, with
a persistent strong surface high north of Hawaii forcing Darby to
accelerate as it makes a turn toward the west. The updated track
forecast is close to the previous forecast, and lies very close to
the GFEX.

Darby is crossing into the central Pacific basin, and this will be
the final NHC advisory on this system. Future information on Darby
can be found in Forecast/Advisories issued by the Central Pacific
Hurricane Center beginning at 1500 UTC under AWIPS header HFOTCMCP1
and WMO header WTPA21 PHFO. For information specific to the
Hawaiian Islands, users should continue to consult products from
the National Weather Service Forecast Office in Honolulu, Hawaii,
at www.weather.gov/hfo.


FORECAST POSITIONS AND MAX WINDS

INIT 14/0900Z 16.2N 139.5W 95 KT 110 MPH
12H 14/1800Z 16.6N 141.6W 85 KT 100 MPH
24H 15/0600Z 17.0N 144.2W 70 KT 80 MPH
36H 15/1800Z 17.1N 146.9W 55 KT 65 MPH
48H 16/0600Z 17.0N 149.8W 40 KT 45 MPH...POST-TROPICAL
60H 16/1800Z 16.9N 153.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 17/0600Z...DISSIPATED

$$
Forecaster Birchard

[cycloneye]

BULLETIN
Hurricane Darby Advisory Number 21
NWS Central Pacific Hurricane Center Honolulu HI EP052022
500 AM HST Thu Jul 14 2022

...DARBY ENTERS THE CENTRAL PACIFIC...
...RAPID WEAKENING ANTICIPATED SOON...


SUMMARY OF 500 AM HST...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...16.6N 140.9W
ABOUT 955 MI...1540 KM E OF HILO HAWAII
ABOUT 1155 MI...1860 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...105 MPH...165 KM/H
PRESENT MOVEMENT...WNW OR 290 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...977 MB...28.85 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM HST (1500 UTC), the center of Hurricane Darby was located
near latitude 16.6 North, longitude 140.9 West. Darby is moving
toward the west-northwest near 16 mph (26 km/h) and this motion is
expected to continue over the next 24 hours, followed by a turn to
the west thereafter. On the forecast track, Darby will pass a few
hundred miles south of the main Hawaiian Islands this weekend.

Maximum sustained winds are near 105 mph (165 km/h) with higher
gusts. Significant weakening is forecast during the next 48
hours, and Darby is expected to become a post-tropical cyclone on
Saturday before dissipating by Sunday.

Hurricane-force winds extend outward up to 15 miles (30 km) from the
center and tropical-storm-force winds extend outward up to 45 miles
(75 km).

The estimated minimum central pressure is 977 mb (28.85 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM HST.

$$
Forecaster Birchard



Hurricane Darby Discussion Number 21
NWS Central Pacific Hurricane Center Honolulu HI EP052022
500 AM HST Thu Jul 14 2022

Darby crossed longitude 140W and officially entered the central
Pacific basin just after midnight HST this morning. The cyclone's
satellite appearance has gone through some fluctuations since the
previous advisory, but an elongated and somewhat ragged 5-10 nm
wide eye has persisted. Pulsing convection continues to encircle the
center, but has become much less symmetric. The initial intensity is
estimated to be 90 kt, supported by a blend of the subjective Dvorak
intensity estimates from SAB and HFO, the latest UW-CIMSS objective
Dvorak estimate of 87 kt, and a SATCON near 83 kt.

Darby lies on the southwestern periphery of a ridge aloft, in an
area characterized by moderate southerly vertical wind shear. Darby
is moving closer to an upper-level trough to its northwest, into an
environment characterized by even stronger vertical wind shear, as
evidenced by transverse banding in the northwest semicircle. This
shear will allow the cyclone to efficiently ingest the dry mid-level
air that prevails, while moving over sub-26C SSTs. Since Darby
continues to be a small system, it will quickly respond to the
debilitating environment into which it is moving, with rapid
weakening expected over the next 48 hours before dissipation occurs
by 72 hours. The updated intensity forecast closely follows the
consensus IVCN, as well as the SHIPS guidance.

The initial motion estimate for this advisory is 290/14kt. As Darby
degrades to a shallow system over the next 48 hours, a persistent
strong surface high north of Hawaii will force it to accelerate as
it makes a turn toward the west. The updated track forecast is close
to the previous forecast, and lies very close to the GFEX.


FORECAST POSITIONS AND MAX WINDS

INIT 14/1500Z 16.6N 140.9W 90 KT 105 MPH
12H 15/0000Z 17.1N 142.9W 75 KT 85 MPH
24H 15/1200Z 17.2N 145.6W 60 KT 70 MPH
36H 16/0000Z 17.2N 148.7W 50 KT 60 MPH
48H 16/1200Z 17.1N 152.1W 40 KT 45 MPH
60H 17/0000Z 16.9N 155.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 17/1200Z...DISSIPATED

$$
Forecaster Birchard

[cycloneye]

BULLETIN
Hurricane Darby Advisory Number 22
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 AM HST Thu Jul 14 2022

...HURRICANE DARBY SLOWLY WEAKENING FAR EAST-SOUTHEAST OF THE
HAWAIIAN ISLANDS WITH MORE RAPID WEAKENING EXPECTED SOON...


SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.0N 142.1W
ABOUT 870 MI...1405 KM E OF HILO HAWAII
ABOUT 1070 MI...1725 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...100 MPH...155 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...980 MB...28.94 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM HST (2100 UTC), the center of Hurricane Darby was located
near latitude 17.0 North, longitude 142.1 West. Darby is moving
toward the west near 16 mph (26 km/h), and this motion is expected
to continue for the next few days. On the forecast track, the
center of Darby, or it's remnant, will pass south of the Big Island
on Saturday.

Maximum sustained winds are near 100 mph (155 km/h) with higher
gusts. Significant weakening is forecast during the next 48
hours, with Darby expected to become a post-tropical cyclone on
Saturday before dissipating by Sunday.

Darby is a small tropical cyclone with hurricane-force winds
extending outward up to 15 miles (30 km) from the center.
Tropical-storm-force winds extend outward up to 45 miles
(75 km).

The estimated minimum central pressure is 980 mb (28.94 inches).


HAZARDS AFFECTING LAND
----------------------
None.


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

$$
Forecaster R Ballard/M Ballard




Hurricane Darby Discussion Number 22
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 AM HST Thu Jul 14 2022

Although Darby's appearance was fairly impressive overnight, the
hurricane has recently taken on a very ragged appearance, with the
central dense overcast becoming much less symmetrical around the
center as shear begins to impact the core convection. The initial
intensity was estimated to be 85 kt, a blend of the Dvorak estimates
from PHFO (77 kt), PGTW (90 kt) and the latest UW-CIMSS ADT (87
kt).

The initial motion is 280/14, with Darby located on the southwest
periphery of a mid-level ridge. An upper level trough to the NW of
Darby has been drawing the TC a little north of due west. This
motion is expected to continue for the next day or so, then turn
more toward due west as Darby gets farther away from the influence
of this trough, and becomes increasingly steered by the lower level
flow. At that time, strong high pressure north of Hawaii will aid in
an increase in forward speed. The track guidance remains tightly
clustered, and our official forecast lies just north of the the
middle of the guidance envelope.

Darby remains a small tropical cyclone over 26C sea surface
temperatures, and is riding along a strong gradient of deep layer
shear, currently about 20 kt near the center. The shear is
expected to remain moderate, with marginal SSTs along the
forecast track, so the guidance is unanimous about additional
weakening. Our forecast remains just a touch more conservative with
the rate of weakening shown by the guidance owing to the recent
persistence of the well-developed core, but still shows Darby
becoming a remnant low on Saturday.


FORECAST POSITIONS AND MAX WINDS

INIT 14/2100Z 17.0N 142.1W 85 KT 100 MPH
12H 15/0600Z 17.3N 144.1W 75 KT 85 MPH
24H 15/1800Z 17.4N 147.0W 60 KT 70 MPH
36H 16/0600Z 17.4N 150.3W 50 KT 60 MPH
48H 16/1800Z 17.2N 153.6W 40 KT 45 MPH
60H 17/0600Z 17.0N 157.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 17/1800Z...DISSIPATED

$$
Forecaster R Ballard/M Ballard

[cycloneye]

BULLETIN
Hurricane Darby Advisory Number 23
NWS Central Pacific Hurricane Center Honolulu HI EP052022
500 PM HST Thu Jul 14 2022

...WEAKENING HURRICANE DARBY MOVING WESTWARD FAR EAST-SOUTHEAST OF
THE HAWAIIAN ISLANDS...


SUMMARY OF 500 PM HST...0300 UTC...INFORMATION
----------------------------------------------
LOCATION...17.5N 143.4W
ABOUT 780 MI...1255 KM E OF HILO HAWAII
ABOUT 980 MI...1575 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...983 MB...29.03 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 500 PM HST (0300 UTC), the center of Hurricane Darby was located
near latitude 17.5 North, longitude 143.4 West. Darby is moving
toward the west near 16 mph (26 km/h) and this motion is expected to
continue for the next few days. The forecast track will bring the
center of Darby, or it's remnant, south of the Big Island on
Saturday.

Maximum sustained winds are near 90 mph (150 km/h) with higher
gusts. Continued weakening is forecast during the next few days,
with Darby expected to become a tropical storm Friday, and further
weaken to a post-tropical cyclone on Saturday before dissipating.

Darby is a small tropical cyclone with hurricane-force winds
extending outward up to 10 miles (20 km) from the center. Tropical
-storm-force winds extend outward up to 45 miles (75 km).

The estimated minimum central pressure is 983 mb (29.03 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 1100 PM HST.

$$
Forecaster M Ballard/R Ballard





Hurricane Darby Discussion Number 23
NWS Central Pacific Hurricane Center Honolulu HI EP052022
500 PM HST Thu Jul 14 2022

Darby is becoming less organized on satellite with pulses of
increasingly ragged deep convection starting to become sheared from
the low level center. The UW-CIMSS deep layer shear analysis
suggests the core of Darby is now experiencing shear of 20 to 25
knots. Dvorak estimates from PHFO, SAB, PGTW all agree with the
latest UW-CIMSS ADT estimate of 77 kt, thus giving good confidence
with an initial intensity of 80 kt with this advisory.

The initial motion is 290/13. Little has changed with the synoptic
situation, with Darby continuing along the southwest periphery of a
mid-level ridge. Darby is moving on a track just north of west,
partly in response to an upper level trough to the northwest of the
system. As it moves further west over the next 24 hours, the upper
level trough will lose some of its influence on the system,
allowing Darby to take a more due west heading. During this time,
the system will weaken further, and the track will be influenced
more by the low level trade wind flow. After 24 hours, a high
pressure system north of the Hawaiian islands will help drive Darby
to the west. The track guidance remains tightly clustered. Our
official track remains close to the previous forecast track, which
remains just a bit north of the middle of the guidance envelope.

The forecast track into Saturday keeps Darby over sea surface
temperatures (SST) of 25-26C. Deep layer shear near the system is
expected to remain 20-25 kt for the next few days. This combination
of shear and marginal SST continue to support weakening. The
intensity guidance agrees and remains tightly clustered as well.
Initially our forecast remains on the higher side of the guidance
envelope, with Darby still expected to become a remnant low by
Saturday night.


FORECAST POSITIONS AND MAX WINDS

INIT 15/0300Z 17.5N 143.4W 80 KT 90 MPH
12H 15/1200Z 17.7N 145.4W 70 KT 80 MPH
24H 16/0000Z 17.7N 148.6W 60 KT 70 MPH
36H 16/1200Z 17.6N 151.9W 50 KT 60 MPH
48H 17/0000Z 17.4N 155.4W 40 KT 45 MPH
60H 17/1200Z 17.2N 158.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 18/0000Z...DISSIPATED

$$
Forecaster M Ballard/R Ballard

[cycloneye]

BULLETIN
Hurricane Darby Advisory Number 24
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 PM HST Thu Jul 14 2022

...HURRICANE DARBY WEAKENS FURTHER AND BARELY HOLDING ON TO
HURRICANE STATUS...


SUMMARY OF 1100 PM HST...0900 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.5N 144.8W
ABOUT 690 MI...1110 KM E OF HILO HAWAII
ABOUT 890 MI...1435 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...75 MPH...120 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...990 MB...29.24 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 PM HST (0900 UTC), the center of Hurricane Darby was located
near latitude 17.5 North, longitude 144.8 West. Darby is moving
toward the west near 16 mph (26 km/h) and this motion is expected to
continue during the next couple days with a slight increase in
forward speed. The forecast track will bring the center of Darby,
or its remnant low, south of the Big Island late Saturday.

Maximum sustained winds are near 75 mph (120 km/h) with higher
gusts. Steady weakening is expected during the next couple days,
with Darby expected to weaken into a tropical storm later tonight,
and to a post-tropical remnant low on Saturday before dissipating.

Darby is a small tropical cyclone with hurricane-force winds
extend outward up to 10 miles (20 km) from the center.
Tropical-storm-force winds extend outward up to 60 miles (95 km).

The estimated minimum central pressure is 990 mb (29.24 inches).


HAZARDS AFFECTING LAND
----------------------
SURF: Large swells generated by Darby are expected to affect
portions of the Hawaiian Islands over the weekend. These swells are
likely to produce hazardous surf and dangerous rip current
conditions. Please consult products from your local National
Weather Service office in Honolulu, Hawaii for further details.


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

$$
Forecaster Jelsema


Hurricane Darby Discussion Number 24
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 PM HST Thu Jul 14 2022

Darby's satellite presentation has deteriorated this evening as it
continues to be influenced by moderate west-southwesterly vertical
wind shear of around 20 knots as indicated by UW-CIMSS vertical
wind shear analysis, and cool sea surface temperatures (SSTs) of
around 25C shown in the NASA SPoRT SST composite. The latest
subjective Dvorak current intensity estimates from PHFO/SAB/JTWC
ranged from 4.0 (65 knots) to 4.5 (77 knots) while the UW-CIMSS
objective ADT current intensity estimate was 3.8 (61 knots).
Additionally, a SATCON estimate at 14/0404Z estimated the cyclones
strength at 64 knots. Given the satellite degradation and
incorporating a blend of the above intensity estimates, Darby's
initial intensity has been lowered to 65 knots with this advisory.
Darby continues on its westward course, with the estimated initial
motion set at 280/14 knots.

Darby will remain in a hostile environment during the next couple
days, characterized by cool SSTs of 25-26C, moderate to strong
westerly vertical wind shear of 20 to 30 knots, and surrounded by
dry mid-level air with relative humidity values of less than 50
percent. As a result, we expect Darby to continue to steadily
weaken during the next couple days. The tropical cyclone is expected
to weaken into a tropical storm later tonight, then weaken further
into a remnant low late Saturday, before dissipating Saturday
night. The intensity forecast has been lowered based on the rapid
rate of weakening the system is experiencing, and follows a blend of
the dynamical and statistical intensity guidance.

The tropical cyclone will continue to be directed westward during
the next couple days, influenced initially by a gradually building
mid and upper level ridge to the north of the system, while deep
convection persists. The cyclone will then begin to move slightly
south of due west at a faster forward speed as deep convection
becomes more sporadic, allowing Darby to be pushed along by the low
level trade wind flow. The forecast track closely follows a blend
of the latest GFS and ECMWF guidance (GFEX) through dissipation,
and is nearly a carbon copy of the previous official forecast track.


FORECAST POSITIONS AND MAX WINDS

INIT 15/0900Z 17.5N 144.8W 65 KT 75 MPH
12H 15/1800Z 17.6N 147.0W 55 KT 65 MPH
24H 16/0600Z 17.6N 150.3W 45 KT 50 MPH
36H 16/1800Z 17.5N 154.0W 35 KT 40 MPH
48H 17/0600Z 17.2N 157.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 17/1800Z...DISSIPATED

$$
Forecaster Jelsema

[cycloneye]

BULLETIN
Tropical Storm Darby Advisory Number 25
NWS Central Pacific Hurricane Center Honolulu HI EP052022
500 AM HST Fri Jul 15 2022

...DARBY WEAKENS TO A TROPICAL STORM WELL EAST OF HAWAII...


SUMMARY OF 500 AM HST...1500 UTC...INFORMATION
----------------------------------------------
LOCATION...17.5N 146.1W
ABOUT 610 MI...980 KM ESE OF HILO HAWAII
ABOUT 810 MI...1305 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...70 MPH...110 KM/H
PRESENT MOVEMENT...W OR 275 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...993 MB...29.33 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 500 AM HST (1500 UTC), the center of Tropical Storm Darby was
located near latitude 17.5 North, longitude 146.1 West. Darby is
moving toward the west near 16 mph (26 km/h) and this motion is
expected to continue during the next couple days with a slight
increase in forward speed. The forecast track will bring the center
of Darby, or its remnant low, south of the Big Island on Saturday.

Maximum sustained winds are near 70 mph (110 km/h) with higher
gusts. Weakening is forecast during the next couple days, with
Darby expected to weaken into a post-tropical remnant low late
Saturday or Saturday night before dissipating on Sunday.

Tropical-storm-force winds extend outward up to 60 miles (95 km)
from the center.

The estimated minimum central pressure is 993 mb (29.33 inches).


HAZARDS AFFECTING LAND
----------------------
SURF: Large swells generated by Darby are expected to affect
portions of the Hawaiian Islands over the weekend. These swells are
likely to produce hazardous surf and dangerous rip current
conditions. Please consult products from your local National
Weather Service office in Honolulu, Hawaii for further details.


NEXT ADVISORY
-------------
Next complete advisory at 1100 AM HST.

$$
Forecaster Jelsema/Gibbs


Tropical Storm Darby Discussion Number 25
NWS Central Pacific Hurricane Center Honolulu HI EP052022
500 AM HST Fri Jul 15 2022

Darby's satellite presentation has degraded further overnight and
continues to be influenced by moderate west-southwesterly vertical
wind shear of around 20 knots as indicated by UW-CIMSS vertical
wind shear analysis, along with cool sea surface temperatures
(SSTs) of around 25C shown in the NASA SPoRT SST composite. The
latest subjective Dvorak current intensity estimates from
PHFO/SAB/JTWC all came in at 4.0 (65 knots) while the UW-CIMSS
objective ADT current intensity estimate was 3.1 (47 knots).
Additionally, a SATCON estimate at 14/1046Z estimated the cyclones
strength at 54 knots. Given the satellite degradation and
incorporating a blend of the above intensity estimates, Darby's
initial intensity has been lowered to 60 knots with this advisory,
making the cyclone a tropical storm. Darby continues on its westward
course, with the estimated initial motion set at 275/14 knots.

Darby will remain in a hostile environment during the next couple
days, characterized by cool SSTs of 25-26C, moderate to strong
westerly vertical wind shear of 20 to 30 knots, and surrounded by
dry mid-level air with relative humidity values of less than 50
percent. As a result, Darby is expected to continue to weaken
quickly today, with a more steady decline thereafter through
dissipation. The tropical cyclone is expected to weaken into a
remnant low late Saturday or Saturday night, before dissipating on
Sunday. The intensity forecast has been adjusted downward with
this advisory package, and follows a blend of the dynamical and
statistical intensity guidance.

The tropical cyclone will continue to be directed westward during
the next couple days, influenced initially by a gradually building
mid and upper level ridge to the north of the system, while deep
convection persists. The cyclone will then begin to move slightly
south of due west at a faster forward speed as deep convection
becomes more sporadic, allowing Darby to be pushed along by the low
level trade wind flow. The forecast track closely follows a blend
of the latest GFS and ECMWF guidance (GFEX) through dissipation,
and is essentially the same as the previous official forecast track.


FORECAST POSITIONS AND MAX WINDS

INIT 15/1500Z 17.5N 146.1W 60 KT 70 MPH
12H 16/0000Z 17.5N 148.5W 45 KT 50 MPH
24H 16/1200Z 17.5N 152.0W 40 KT 45 MPH
36H 17/0000Z 17.3N 155.9W 35 KT 40 MPH
48H 17/1200Z 16.9N 159.8W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 18/0000Z...DISSIPATED

$$
Forecaster Jelsema/Gibbs

[cycloneye]

BULLETIN
Tropical Storm Darby Advisory Number 26
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 AM HST Fri Jul 15 2022

...WEST-MOVING DARBY CONTINUES TO WEAKEN EAST-SOUTHEAST OF
HAWAII...


SUMMARY OF 1100 AM HST...2100 UTC...INFORMATION
-----------------------------------------------
LOCATION...17.6N 147.7W
ABOUT 505 MI...815 KM ESE OF HILO HAWAII
ABOUT 710 MI...1145 KM ESE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...W OR 270 DEGREES AT 20 MPH...31 KM/H
MINIMUM CENTRAL PRESSURE...1002 MB...29.59 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND OUTLOOK
----------------------
At 1100 AM HST (2100 UTC), the center of Tropical Storm Darby was
located near latitude 17.6 North, longitude 147.7 West. Darby is
moving toward the west near 20 mph (31 km/h) and this motion is
expected to continue over the next couple of days. The forecast
track brings the center of Darby, or its remnant, south of the
Big Island on Saturday.

Maximum sustained winds are near 60 mph (95 km/h) with higher gusts.
Darby is expected to continue to weaken, to a tropical depression
Friday night, then become a post-tropical cyclone Saturday before
dissipating by Sunday night.

Tropical-storm-force winds extend outward up to 60 miles (95 km)
from the center.

The estimated minimum central pressure is 1002 mb (29.59 inches).


HAZARDS AFFECTING LAND
----------------------
SURF: Large swells generated by Darby are expected to affect
portions of the Hawaiian Islands over the weekend. These swells are
likely to produce hazardous surf and dangerous rip current
conditions. Please consult products from your local National
Weather Service office in Honolulu, Hawaii for further details.

RAINFALL: Darby is expected to produce localized storm total
rainfall of up to 2 to 4 inches along portions of mainly windward
Big Island and windward Maui. These rains may cause nuisance
flooding especially in low-lying and poor drainage areas.


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

$$
Forecaster M Ballard/R Ballard




Tropical Storm Darby Discussion Number 26
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 AM HST Fri Jul 15 2022

Darby lost its deep convection around 1400Z, as a result of
persistent shear of 25 to 30 kt, per the UW-CIMSS deep shear
analysis. The loss of deep convection has left behind an exposed
low level center. Dvorak intensities from PHFO and PGTW were 55 kt,
SAB at 45 kt and UW-CIMSS ADT at 35 kt. The CIMSS SATCON from
1638Z had a CI of 49 kt. With the convection gone, and a high
confidence in the downward trend, have opted to go with a
conservative blend of these intensities for an initial value of 50
kt.

The initial motion is 275/13. With the convection sheared off, but
cloud tops still reaching near 20K feet, the mid levels are helping
to guide Darby. Over the next day or so, the low-level flow will
become the steering force for the system. Both the mid- and
low-levels are dominated by a large anticyclone far to the north
of the cyclone, which will maintain a westerly track. The track
guidance has become a little less tightly clustered as it has
been over the last several runs, with some variations in how the
models are handling the rate of weakening. The current forecast
track remains close to the past track, near the center of the
guidance envelope.

The forecast track keeps Darby in a moderately sheared environment
for the next couple of days, and continuing along the 25-26C sea
surface temperatures (SST). The shear, SST and climatologically low
mid-level relative humidity values near the track all work against
redevelopment of Darby. The intensity forecast has been lowered some
from the past forecast, to be in line with the latest guidance
consensus, which leads to dissipation of the remnant circulation by
Sunday night.


FORECAST POSITIONS AND MAX WINDS

INIT 15/2100Z 17.6N 147.7W 50 KT 60 MPH
12H 16/0600Z 17.6N 150.2W 40 KT 45 MPH
24H 16/1800Z 17.5N 153.9W 35 KT 40 MPH
36H 17/0600Z 17.2N 157.7W 30 KT 35 MPH
48H 17/1800Z 16.9N 161.5W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 18/0600Z...DISSIPATED

$$
Forecaster M Ballard/R Ballard

[cycloneye]

Tropical Storm Darby Discussion Number 28
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 PM HST Fri Jul 15 2022

Deep convection associated with Darby remains limited, with only
a few small deep convective bursts occurring over the past 12
hours. CIMSS SATCON intensity estimates ranged from 37 to 44 kt.
The various satellite intensity estimates ranged from 30-40 kt
from PHFO and SAB. Based on these data, and convective trends,
the initial intensity remains at 40 kt.

The initial motion is now 265/18 kt. Darby will continue to move
westward in the low-level trade wind flow until the system
dissipates. The new forecast track is in the center of the
tightly-clustered track guidance, with very little change from the
previous track.

Darby will continue to weaken as it moves over 25-26C sea surface
temperatures and ingests drier air. This combined with moderate
shear will translate to the system becoming a post-tropical cyclone
by 24 hours, and the global models are in good agreement that the
system will dissipate to a surface trough by 36 hours. The new
intensity forecast is very similar to the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 16/0900Z 17.4N 151.2W 40 KT 45 MPH
12H 16/1800Z 17.4N 154.3W 35 KT 40 MPH
24H 17/0600Z 17.2N 158.2W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 17/1800Z...DISSIPATED

$$

Forecaster Jelsema/Gibbs

[cycloneye]

Tropical Storm Darby Discussion Number 29
NWS Central Pacific Hurricane Center Honolulu HI EP052022
500 AM HST Sat Jul 16 2022

Deep convection associated with Darby remains limited, with only
a recent burst of convection north of the low-level circulation
center over the past few hours. CIMSS SATCON intensity estimates
remain around 40 kt. The current satellite intensity estimate
from PHFO is 35 kt. Based on these data, and convective trends, the
initial intensity remains at 40 kt.

The initial motion is now 270/19 kt. Low- to mid-level easterly
flow associated with high pressure to the north supports the
westerly track persisting until the system dissipates. The new
forecast track is in the center of the tightly-clustered track
guidance, with only a slight increase in forward speed compared to
the previous forecast.

Darby will continue to weaken as it moves over 25-26C sea surface
temperatures and ingests drier air. This combined with moderate
shear will translate to the system becoming a post-tropical cyclone
by 24 hours, and the global models are in good agreement that the
system will dissipate to a surface trough by 36 hours. The new
intensity forecast is very similar to the previous forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 17.5N 153.3W 40 KT 45 MPH
12H 17/0000Z 17.3N 156.4W 35 KT 40 MPH
24H 17/1200Z 17.2N 160.3W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 18/0000Z...DISSIPATED

$$
Forecaster Jelsema/Gibbs

[cycloneye]

Tropical Storm Darby Discussion Number 30
NWS Central Pacific Hurricane Center Honolulu HI EP052022
1100 AM HST Sat Jul 16 2022

Deep convection redeveloped in the northern semicircle near the
center last night. High clouds from this convection briefly obscured
the center but it has become exposed once again. The convection
appears to be poorly organized and is not persistent near the center
over time. This pulsing of convection is typical behavior of a
central Pacific tropical cyclone as it goes through its weakening
process toward dissipation. The center of Darby is visible in the
South Point radar data and indicates the center passing south of the
Big Island at this time. The current satellite intensity estimate
from PHFO came in at 2.0/30 kt. This was the only subjective
estimate available. The CIMSS ADT was 2.0/30 kt, and the latest
available SATCON from 1208 UTC was 37 kt. The initial intensity for
this advisory is 35 kt, though this may be generous.

Darby is a shallow system and is being steered by the low- to
mid-level easterly flow. This steering current will remain in place
until the system dissipates. The forecast track is just an update
to the previous track.

Although SSTs are expected to slowly increase along the remaining
forecast track, vertical shear is forecast to increase above 30 kt
tonight in both the GFS and ECMWF SHIPS guidance. Thus,
reintensification is not expected. Thus, the forecast keeps the
weakening trajectory of the previous forecast, which makes Darby a
post-tropical system tonight and dissipates it by Sunday. If
additional data are received that indicate the circulation has
opened up to a trough, or if deep convection does not persist near
the center, the system could be dropped as a tropical cyclone
sooner.


FORECAST POSITIONS AND MAX WINDS

INIT 16/2100Z 17.7N 155.5W 35 KT 40 MPH
12H 17/0600Z 17.7N 158.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
24H 17/1800Z...DISSIPATED

$$
Forecaster Kodama

[cycloneye]

Remnants of Darby Discussion Number 31
NWS Central Pacific Hurricane Center Honolulu HI EP052022
500 PM HST Sat Jul 16 2022

Scatterometer data from ASCAT-B at 2034 UTC showed 35-40 kt winds,
and ASCAT-C at 1946 UTC showed several 35 kt barbs in the northern
quadrant. However, the wind field from both datasets did not show a
well-defined circulation center. This was also evident in the
earlier CFOSAT scatterometer pass from 1722 UTC. With the lack of a
low level circulation center, Darby has opened up into a trough and
is no longer considered to be a tropical cyclone.

As a result, this is the last advisory issued by the Central Pacific
Hurricane Center on Darby. Additional information on this system can
be found in the High Seas Forecasts issued by the National Weather
Service in Honolulu under AWIPS header HFOHSFNP and WMO header
FZPN40 PHFO.


FORECAST POSITIONS AND MAX WINDS

INIT 17/0300Z 17.7N 157.5W 35 KT 40 MPH
12H 17/1200Z...DISSIPATED

$$
Forecaster Kodama