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