WTPA41 PHFO 250234

TCDCP1



TROPICAL DEPRESSION SIX-C DISCUSSION NUMBER   1

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP062015

500 PM HST THU SEP 24 2015



RECENT SATELLITE IMAGES SHOWED THAT A TROPICAL DISTURBANCE SOUTHEAST

OF THE MAIN HAWAIIAN ISLANDS HAS DEVELOPED DEEP CONVECTION WITHIN A

CURVED BAND NEAR ITS CENTER. IN ADDITION...A 1953 UTC ASCAT PASS

SHOWED WINDS AT 30 KT WITHIN 80 NM OF THE DISTURBANCE/S EASTERN

SEMICIRCLE. SUBJECTIVE DVORAK FIXES UNANIMOUSLY CAME IN AT 2.0/30

KT. AS A RESULT OF THESE DATA...ADVISORIES ARE BEING INITIATED ON

TROPICAL DEPRESSION SIX-C. THIS IS THE ELEVENTH TROPICAL CYCLONE IN

THE CENTRAL NORTH PACIFIC BASIN FOR THE 2015 SEASON AND TIES THE

RECORD FOR THE MOST ACTIVE SEASON WHICH WAS SET IN 1992 AND

REPEATED IN 1994.



THE DEPRESSION IS MOVING AT 320/7 KT TOWARDS A WEAKNESS IN THE

SUBTROPICAL RIDGE. THIS MOTION IS EXPECTED TO CONTINUE OVER THE NEXT

COUPLE OF DAYS. A LARGE MIDDLE AND UPPER LEVEL LOW PRESSURE SYSTEM

CURRENTLY FAR NORTHEAST OF THE HAWAIIAN ISLANDS IS FORECAST TO MOVE

TOWARD THE SOUTHEAST. AN ASSOCIATED TROUGH EXTENDING SOUTHWEST FROM

THE LOW WILL SHIFT SOUTHWARD...RESULTING IN AN INCREASE IN UPPER

LEVEL SOUTHWESTERLIES...AND VERTICAL WIND SHEAR...THAT WILL IMPACT

THE TROPICAL CYCLONE. GLOBAL MODELS SHOW THAT THE VERTICAL SHEAR

WILL DECOUPLE THE SYSTEM BEYOND 48 HOURS...WHICH MEANS THE

CYCLONE WILL BECOME SHALLOW AND MOVE WITH THE LOWER LEVEL STEERING

CURRENT. THE RELIABLE DYNAMICAL MODELS ARE IN GENERAL AGREEMENT WITH

THIS SCENARIO AND ARE FAIRLY CLOSE TO EACH OTHER WITH THE MAIN

DIFFERENCES BEING THE FORWARD SPEED AFTER DECOUPLING OCCURS. THE

TRACK FORECAST FOR THIS ADVISORY CLOSELY FOLLOWS THE DYNAMIC

CONSENSUS AND IS BETWEEN THE GFS TO THE SOUTH AND THE ECMWF TO THE

NORTH.



TROPICAL DEPRESSION SIX-C IS PASSING OVER WARM WATER...28C TO 29C

BASED ON THE LATEST ANALYSIS. MODERATE SHEAR IS ALREADY AFFECTING

THE SYSTEM ACCORDING TO THE 0000 UTC CIMSS ANALYSIS AND IS FORECAST

TO INCREASE...ESPECIALLY BEYOND 48 HOURS. BEFORE THE STRONGER SHEAR

SETS IN AND DECOUPLES THE CYCLONE...THERE APPEARS TO BE A WINDOW OF

OPPORTUNITY FOR STRENGTHENING. THUS...THE FORECAST CALLS FOR SIX-C

TO BECOME A TROPICAL STORM TONIGHT FOLLOWED BY STEADY WEAKENING

AFTER 36 HOURS. IF IT DOES BECOME A TROPICAL STORM IT WILL BE NAMED

NIALA...PRONOUNCED NEE-AH-LA.





FORECAST POSITIONS AND MAX WINDS



INIT  25/0300Z 14.5N 149.3W   30 KT  35 MPH

 12H  25/1200Z 15.1N 150.0W   35 KT  40 MPH

 24H  26/0000Z 16.2N 151.0W   40 KT  45 MPH

 36H  26/1200Z 17.0N 152.2W   40 KT  45 MPH

 48H  27/0000Z 17.4N 153.5W   35 KT  40 MPH

 72H  28/0000Z 17.5N 156.0W   30 KT  35 MPH

 96H  29/0000Z 17.0N 157.5W   30 KT  35 MPH

120H  30/0000Z 16.5N 159.0W   25 KT  30 MPH



$$

FORECASTER KODAMA