WTPA33 PHFO 240557
TCPCP3

BULLETIN
TROPICAL STORM DARBY INTERMEDIATE ADVISORY NUMBER  50A
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP052016
800 PM HST SAT JUL 23 2016

…DARBY EMERGES BACK OVER WATER WEST OF THE BIG ISLAND…

SUMMARY OF 800 PM HST…0600 UTC…INFORMATION
———————————————-
LOCATION…19.4N 156.3W
ABOUT 25 MI…40 KM SW OF KAILUA-KONA HAWAII
ABOUT 165 MI…265 KM SE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS…40 MPH…65 KM/H
PRESENT MOVEMENT…W OR 275 DEGREES AT 11 MPH…18 KM/H
MINIMUM CENTRAL PRESSURE…1004 MB…29.65 INCHES

WATCHES AND WARNINGS
——————–
CHANGES WITH THIS ADVISORY:

None.

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Warning is in effect for…
* All islands in the state of Hawaii.

A Tropical Storm Warning means that tropical storm conditions are
imminent or already occurring. In this case, tropical storm
conditions are occurring over portions of the Big Island, and are
expected over Maui County and Oahu later tonight and Sunday.

Interests in the eastern portion of the Papahanaumokuakea Marine
National Monument should monitor the progress of Darby.

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 800 PM HST (0600 UTC), the apparent center of Tropical Storm
Darby has emerged off the west coast of the Big Island, and is
located near latitude 19.4 North, longitude 156.3 West. Darby is
moving toward the west near 11 mph (18 km/h). Darby is forecast to
make a turn toward the northwest later tonight and continue moving
northwestward over the next 48 hours, with little change in forward
speed.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts.
Slight weakening is forecast during the next 48 hours.

Tropical storm force winds extend outward up to 70 miles (110 km)
from the center. Sustained winds of 43 mph and wind gusts to 61
mph were reported in Kohala Ranch on the Big Island earlier this
afternoon.

The estimated minimum central pressure is 1004 mb (29.65 inches).

HAZARDS AFFECTING LAND
———————-
WIND:  Tropical storm force winds are expected over the Big Island
tonight, over portions of Maui County later tonight and Sunday, over
Oahu Sunday and Sunday night, and over Kauai County Sunday night and
Monday.

SURF:  Swells generated by Darby are expected to impact the
Hawaiian Islands over the next day or so, with swells diminishing
thereafter.

RAINFALL:  Storm total rainfall of 8 to 12 inches, with possible
isolated maximum amounts of 15 inches. These rains could produce
life-threatening flash floods and landslides.

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

$$
Forecaster Houston/Jelsema

WTPA43 PHFO 240307 CCA
TCDCP3

TROPICAL STORM DARBY DISCUSSION NUMBER  50
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP052016
500 PM HST SAT JUL 23 2016

The 53rd Weather Reconnaissance Squadron flew through Darby for a
good portion of the day, and departed the storm just before the
poorly-defined center came ashore over the southeastern portion of
the Big Island near Pahala around 2 pm.  The center is estimated to
be traversing the southern slopes of the Big Island at this time.
Surface pressures were rising each time the plane sampled the
system, and flight-level winds indicated that Darby’s intensity
had weakened to near 35 kt, and that is the initial intensity for
this advisory.  Another reconnaissance flight is scheduled for early
Sunday morning to determine what remains of Darby’s circulation
after it emerges from the Big Island.

The initial motion is estimated to be 275/09 kt, with the
poorly-defined center of Darby currently estimated to be over
interior portions of the Big Island.  After emerging from the Big
Island later this evening, a turn toward the northwest is expected,
with Darby moving toward the northwest through the remainder of the
forecast period.  Darby is still expected to move into a weakness in
the mid-level ridge to its north over the next 24 hours, as a deep-
layer low remains nearly stationary far north of the Hawaiian
Islands.  While the spread in the track guidance has increased
slightly from the previous cycle, it continues to indicate a steady
northwest motion.  The updated track forecast is close to the
previous and the multi-model consensus TVCN.

As the center of Darby is currently over the Big Island, there is
considerable uncertainty as to what will remain of the low-level
circulation once it moves back over water later this evening.  The
intensity forecast is conservatively maintaining Darby as a minimal
tropical storm through 24 hours until it is clear that re-
development will not occur.  Thereafter, steady weakening is
anticipated, as increasing shear and gradually cooling waters lie
along the forecast track.  The updated forecast indicates weakening
to a remnant low in 72 hours, with dissipation expected by the end
of the forecast period.  This is a slower rate of weakening than
depicted by global models through the first 24 hours, and the
intensity consensus, IVCN, but closely follows IVCN thereafter. If
Darby’s circulation does not survive its interaction with the Big
Island’s rugged terrain, than dissipation will likely occur much
sooner.

FORECAST POSITIONS AND MAX WINDS

INIT  24/0300Z 19.3N 155.8W   35 KT  40 MPH…INLAND
12H  24/1200Z 20.0N 156.9W   35 KT  40 MPH
24H  25/0000Z 21.0N 158.4W   35 KT  40 MPH
36H  25/1200Z 22.2N 159.8W   30 KT  35 MPH
48H  26/0000Z 23.6N 161.3W   30 KT  35 MPH
72H  27/0000Z 27.0N 164.7W   25 KT  30 MPH…POST-TROP/REMNT LOW
96H  28/0000Z 30.8N 167.8W   20 KT  25 MPH…POST-TROP/REMNT LOW
120H  29/0000Z…DISSIPATED

$$
Forecaster Birchard
H