WTPA45 PHFO 190251

TCDCP5



TROPICAL DEPRESSION FIVE-C DISCUSSION NUMBER   1

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP052015

500 PM HST FRI SEP 18 2015



THE TROPICAL DISTURBANCE CENTERED ABOUT 360 MILES WEST-NORTHWEST OF

JOHNSTON ISLAND DEVELOPED WELL-DEFINED BANDING WITHIN THE EASTERN

SEMICIRCLE AND NORTHERN QUADRANT TODAY. A 2102 UTC ASCAT PASS

DETECTED A CLOSED CIRCULATION AROUND AN ELONGATED CENTER WITH A

SURFACE TROUGH EXTENDING TO THE SOUTHWEST AND NUMEROUS AREAS OF 30

KT WINDS WITHIN THE NORTHERN SEMICIRCLE. THEREFORE...ADVISORIES ARE

BEING INITIATED ON TROPICAL DEPRESSION FIVE-C...THE TENTH TROPICAL

CYCLONE IN THE CENTRAL NORTH PACIFIC FOR THE 2015 SEASON. DVORAK

CURRENT INTENSITY ESTIMATES CAME IN AT 2.0/30 KT FROM HFO AND SAB

AND 1.5/25 KT FROM JTWC. THE INITIAL INTENSITY WILL BE SET AT 30 KT.



THE INITIAL MOTION IS TOWARD THE NORTHEAST...OR 35 DEGREES...AT 13

KT. THE DEPRESSION IS MOVING ALONG THIS TRACK BETWEEN A DEEP RIDGE

FAR TO THE NORTHEAST AND A DIGGING MID TO UPPER LEVEL TROUGH

APPROACHING FROM THE NORTHWEST. ASIDE FROM A SLIGHT DECREASE IN

FORWARD MOTION...LITTLE CHANGE IN THE MOTION IS EXPECTED INTO

SATURDAY. THE CYCLONE WILL TURN TOWARD THE NORTH AND ACCELERATE ON

SUNDAY THROUGH TUESDAY AS IT INCREASINGLY INTERACTS WITH THE SLOW

MOVING MID TO UPPER LEVEL TROUGH. THE TRACK FORECAST IS NEAR THE

MIDDLE OF A RATHER TIGHTLY CLUSTERED DYNAMICAL AND CONSENSUS MODEL

ENVELOPE THROUGH 72 HOURS AND IS ON THE LEFT SIDE OF DIVERGING

GUIDANCE THEREAFTER.



SLOW INTENSIFICATION IS EXPECTED IN THE SHORT TERM. THE CYCLONE

WILL BE MOVING OVER VERY WARM SEA SURFACE TEMPERATURES...BUT THE

BIG CHALLENGE IS HOW THE SYSTEM RESPONDS TO VERTICAL WIND SHEAR.

FIVE-C IS CURRENTLY NORTH OF THE RIDGE AXIS ALOFT AND IS

EXPERIENCING SOUTHWESTERLY UPPER LEVEL WINDS. THIS FLOW IS

RESTRICTING OUTFLOW IN THE SOUTHWEST QUADRANT BUT IS PRODUCING AN

OUTFLOW CHANNEL TO THE NORTH AND EAST. AS THE UPPER LEVEL TROUGH

EDGES CLOSER...VERTICAL WIND SHEAR WILL RAMP UP QUICKLY AND ARREST

THE INTENSIFICATION TREND. THE OFFICIAL FORECAST FOLLOWS LGEM

CLOSELY AND ASSUMES THAT THIS PROCESS WILL BEGIN LATE SATURDAY OR

SUNDAY. THIS FORECAST IS ON THE LOWER END OF THE GUIDANCE

ENVELOPE...IN WHICH MOST MEMBERS ALLOW THE SYSTEM TO INTENSIFY

SLIGHTLY LONGER.



TROPICAL STORM WATCHES HAVE BEEN ISSUED FOR THE CENTRAL PORTIONS OF

THE PAPAHANAUMOKUAKEA NATIONAL MARINE MONUMENT FROM LISIANSKI

ISLAND TO MARO REEF TO FRENCH FRIGATE SHOALS. IF CURRENT TRENDS

CONTINUE...WARNINGS WILL LIKELY BE ISSUED TONIGHT OR SATURDAY.





FORECAST POSITIONS AND MAX WINDS



INIT  19/0300Z 18.6N 174.5W   30 KT  35 MPH

 12H  19/1200Z 19.8N 173.5W   35 KT  40 MPH

 24H  20/0000Z 21.1N 172.9W   40 KT  45 MPH

 36H  20/1200Z 22.9N 172.6W   45 KT  50 MPH

 48H  21/0000Z 24.8N 172.3W   45 KT  50 MPH

 72H  22/0000Z 29.5N 172.2W   45 KT  50 MPH...POST-TROPICAL

 96H  23/0000Z 37.1N 172.9W   40 KT  45 MPH...POST-TROPICAL

120H  24/0000Z 42.2N 176.8W   35 KT  40 MPH...POST-TROPICAL



$$

FORECASTER WROE