WTPA41 PHFO 290238

TCDCP1



POST-TROPICAL CYCLONE NIALA DISCUSSION NUMBER  17

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP062015

500 PM HST MON SEP 28 2015



LATEST SATELLITE IMAGES SHOW THAT THE SHRINKING LOW-LEVEL

CIRCULATION CENTER /LLCC/ OF NIALA HAS DEGRADED TO THE POINT THAT

THE ASSOCIATED CIRCULATION IS BECOMING INCREASINGLY DIFFICULT TO

IDENTIFY. PERSISTENT WESTERLY VERTICAL WIND SHEAR HAS CAUSED THE

SYSTEM TO BECOME SHALLOW...AND THE SHALLOW REMNANT IS LOSING ITS

IDENTITY AS IT BECOMES EMBEDDED WITHIN A LARGE-SCALE MONSOON TROUGH

THAT EXTENDS INTO THE CENTRAL PACIFIC FROM THE WEST. MID- AND

HIGH-LEVEL CLOUDS SPREADING FROM WEST TO EAST ARE BEGINNING TO

OBSCURE THE LLCC...AND ALSO HELP TO HIGHLIGHT THE DEBILITATING

WESTERLY WIND SHEAR...CURRENTLY ANALYZED TO BE NEAR 30 KT BY UW-

CIMSS. WHILE CONVECTION HAS RECENTLY FLARED IN THE VICINITY OF THE

SYSTEM...THIS IS MORE RELATED TO CONVERGENCE ASSOCIATED WITH THE

MONSOON TROUGH...AND LESS SO WITH NIALA/S CIRCULATION. WHILE SAB AND

PHFO DEEMED THE SYSTEM TOO WEAK TO CLASSIFY...PGTW DERIVED A CURRENT

INTENSITY OF 1.5/25 KT. GIVEN THIS DATA...NIALA IS DEEMED TO BE A

25 KT POST-TROPICAL LOW WITH THIS FORECAST PACKAGE.



THE INITIAL MOTION VECTOR FOR THIS ADVISORY IS 285/08 KT. THE

REMNANT LOW IS FORECAST TO MOVE GENERALLY TOWARD THE WEST THEN

WEST-SOUTHWEST THE NEXT TWO DAYS...SOUTH A PERSISTENT SURFACE RIDGE

OF HIGH PRESSURE FAR TO THE NORTH. AS IT DOES SO...GLOBAL MODELS

INDICATE THE REMNANT OF NIALA WILL CONTINUE TO MERGE INTO THE

MONSOON TROUGH AND DISSIPATE. WHILE A BROAD AREA OF LOW PRESSURE IS

EXPECTED TO EVENTUALLY DEVELOP WITHIN THE TROUGH...IT IS NOT LIKELY

THAT NIALA WILL REMAIN AN IDENTIFIABLE FEATURE...AND THE UPDATED

FORECAST CONSERVATIVELY CALLS FOR NIALA TO DISSIPATE WITHIN 48

HOURS. THIS FORECAST PHILOSOPHY IS GENERALLY SUPPORTED BY GFS AND

ECMWF GUIDANCE...BUT IS A LITTLE SLOWER THAN THESE MODELS IN

FORECASTING DISSIPATION.



THIS WILL BE THE LAST ADVISORY ISSUED BY THE CENTRAL PACIFIC

HURRICANE CENTER ON NIALA UNLESS REGENERATION OCCURS. ADDITIONAL

INFORMATION ON THIS SYSTEM CAN BE FOUND IN HIGH SEAS FORECASTS

ISSUED BY THE NATIONAL WEATHER SERVICE UNDER AWIPS HEADER HFOHSFNP

AND WMO HEADER FZPN40 PHFO.





FORECAST POSITIONS AND MAX WINDS



INIT  29/0300Z 15.5N 158.8W   25 KT  30 MPH...POST-TROP/REMNT LOW

 12H  29/1200Z 15.4N 159.6W   25 KT  30 MPH...POST-TROP/REMNT LOW

 24H  30/0000Z 15.1N 161.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

 36H  30/1200Z 14.9N 162.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

 48H  01/0000Z...DISSIPATED



$$



FORECASTER BIRCHARD