WTPA33 PHFO 241155
TCPCP3

BULLETIN
TROPICAL STORM DARBY INTERMEDIATE ADVISORY NUMBER  51A
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP052016
200 AM HST SUN JUL 24 2016

…HEAVY RAINS FROM DARBY CONTINUE TO IMPACT THE BIG ISLAND AS IT
MOVES SLOWLY AWAY…

SUMMARY OF 200 AM HST…1200 UTC…INFORMATION
———————————————-
LOCATION…19.6N 157.0W
ABOUT 70 MI…115 KM W OF KAILUA-KONA HAWAII
ABOUT 130 MI…210 KM SSE OF HONOLULU HAWAII
MAXIMUM SUSTAINED WINDS…40 MPH…65 KM/H
PRESENT MOVEMENT…WNW OR 290 DEGREES AT 10 MPH…17 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. These
conditions are expected over Maui County and Oahu today through
tonight, and over Kauai late tonight and Monday.

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 200 AM HST (1200 UTC), the center of Tropical Storm Darby was
located near latitude 19.6 North, longitude 157.0 West. Darby is
moving toward the west-northwest near 10 mph (17 km/h). Darby is
forecast to make a slight turn toward the northwest later tonight
and continue moving northwest over the next 48 hours, with little
change in forward speed.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts.
Little change in intensity is forecast through Sunday night with
slight weakening expected by Monday.

Tropical-storm-force winds extend outward up to 70 miles (110 km)
from the center. Tropical Storm force wind gusts continue across
much of the island chain.

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

HAZARDS AFFECTING LAND
———————-
WIND:  Tropical Storm force winds are occurring over portions of the
Big Island. These winds are expected over parts of Maui County and
Oahu today through tonight, and over Kauai late tonight and Monday.

SURF:  Swells generated by Darby are impacting the Hawaiian Islands,
and will continue over the next day or so, before diminishing.

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 500 AM HST.

$$
Forecaster Houston/Jelsema

WTPA43 PHFO 240914
TCDCP3

TROPICAL STORM DARBY DISCUSSION NUMBER  51
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP052016
1100 PM HST SAT JUL 23 2016

Darby was difficult to find this evening after it emerged from the
Big Island. A 0732z ASCAT pass seems to confirm the current position
estimate. However, the system is likely continuing to organize after
its encounter with volcanic peaks of nearly 14 thousand feet,
earlier today. This terrain severely disrupted the low level center,
which appears to have emerged slightly south of its previous
forecast track. This is often the case with tropical cyclones that
encounter major land areas, especially when mountainous terrain
is present. In addition, the amount of time the center was over land
removed it from its primary energy source, which is the Pacific
Ocean. Since the center is again over water, all of the satellite
fix agencies estimated the current intensity to be 2.5/35 kt,
while the CIMSS ADT estimates was 2.3/33 kt. We are maintaining
Darby as a 35 kt tropical storm for this advisory.

The initial motion is estimated to be 290/09 kt, with the
poorly-defined center of Darby currently located just west
of the Big Island coast. The system is expected to eventually turn
toward the northwest, with Darby moving generally northwest through
the remainder of the forecast period. There remains some spread in
the track guidance, but the models continue to suggest this
northwest motion is likely to continue. The models appear to be
influenced by a forecast weakness developing in the mid-level ridge
to its north over the next 18 to 24 hours, due to a deep-layer low
that remains nearly stationary far north of the Hawaiian Islands.
The updated track forecast is close to the previous and closely
follows the latest multi-model consensus TVCN and the latest GFEX.

The intensity forecast is maintaining Darby as a minimal tropical
storm through 36 hours. The warm water temperatures and ample
ocean heat content depicted in the most recent CIRA analysis south
of the main Hawaiian Islands are likely sufficient to maintain a
tropical storm. The latest SHIPS guidance appears to indicate Darby
may not weaken as fast as it had in the previous run. However,
within 48 hours, all of the guidance indicates steady weakening will
occur, as increasing vertical wind shear and gradually cooling
waters lie along the forecast track. The latest forecast again
indicates weakening to a remnant low in 72 hours, with dissipation
expected by the end of the forecast period. Of note, a recent 0836z
observation from the Oahu Forest NWR RAWS site in the Koolau
mountain range indicated sustained winds of 29 mph with gusts to
60 mph.

Note that another flight by the 53rd Weather Reconnaissance Squadron
is scheduled to fly into Darby after dawn Sunday morning to
determine what the intensity of Darby is after its circulation
spends several more hours over the warm ocean waters west of the Big
Island.

FORECAST POSITIONS AND MAX WINDS

INIT  24/0900Z 19.5N 156.8W   35 KT  40 MPH
12H  24/1800Z 20.2N 157.8W   35 KT  40 MPH
24H  25/0600Z 21.4N 159.1W   35 KT  40 MPH
36H  25/1800Z 22.7N 160.6W   35 KT  40 MPH
48H  26/0600Z 24.1N 162.1W   30 KT  35 MPH
72H  27/0600Z 27.3N 165.2W   25 KT  30 MPH…POST-TROP/REMNT LOW
96H  28/0600Z 30.0N 169.0W   25 KT  30 MPH…POST-TROP/REMNT LOW
120H  29/0600Z…DISSIPATED

$$
Forecaster Houston/Jelsema
H