WTPA45 PHFO 191500

TCDCP5



TROPICAL DEPRESSION FIVE-C DISCUSSION NUMBER   3

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP052015

500 AM HST SAT SEP 19 2015



INFRARED SATELLITE IMAGES SHOW THAT A MASS OF COLD CLOUD TOPS

ASSOCIATED WITH THE CYCLONE HAS PERSISTED SINCE THE PREVIOUS

ADVISORY. IN THE ABSENCE OF ANY TIMELY OR USEFUL MICROWAVE PASSES...

BI-SPECTRAL IMAGERY SHOWS HINTS OF LOW CLOUD LINES CURVING INTO WHAT

APPEARS TO BE A LOW LEVEL CIRCULATION CENTER LOCATED ON THE

NORTHWESTERN EDGE OF THE COLD CLOUD TOPS. THE DIFFICULTY IN FINDING

THE LOW LEVEL CENTER IS HIGHLIGHTED BY THE LATEST SUBJECTIVE DVORAK

INTENSITY ESTIMATES FROM PHFO/PGTW/KNES...WHICH ARE NEARLY 2 DEGREES

APART IN THEIR CENTER POSITION ESTIMATES. LATEST T-NUMBERS RANGE FROM

2.0/30 KT FROM PHFO/KNES WHILE JTWC DERIVED 2.5/35 KT. DUE TO

UNCERTAINTIES ASSOCIATED WITH THE POSITION OF THE LOW LEVEL

CENTER...THE INITIAL INTENSITY FOR THIS ADVISORY WILL BE MAINTAINED

AT 30 KT.



FOR REASONS DESCRIBED ABOVE...THE INITIAL MOTION VECTOR FOR THIS

ADVISORY IS A SOMEWHAT UNCERTAIN 045/08 KT. THE DEPRESSION IS

CURRENTLY BEING STEERED BY THE FLOW BETWEEN A MID- AND UPPER-LEVEL

RIDGE LOCATED TO ITS SOUTHEAST...AND AN APPROACHING CLOSED LOW ALOFT

CENTERED TO THE DISTANT NORTHWEST. THIS SHOULD CONTINUE THROUGH THE

NEXT 12 HOURS OR SO...WITH A TURN TOWARD THE NORTH AND AN INCREASE

IN FORWARD SPEED EXPECTED THEREAFTER. THIS WILL OCCUR AS THE DEEP

LAYER FLOW BECOMES INCREASINGLY SOUTHERLY...AS THE LOW TO THE

NORTHWEST DRAWS CLOSER...AND A NORTH-SOUTH ORIENTED RIDGE DEVELOPS

NEAR THE MAIN HAWAIIAN ISLANDS. THE UPDATED TRACK FORECAST IS ONCE

AGAIN CLOSE TO THE PREVIOUS...AND LIES NEAR THE MIDDLE OF THE

RELIABLE GUIDANCE...WHICH IS TIGHTLY CLUSTERED IN TAKING THE CENTER

OF THE CYCLONE VERY CLOSE TO LAYSAN. ALTHOUGH THERE ARE LITTLE IN

THE WAY OF ACROSS-TRACK DIFFERENCES BETWEEN THE RELIABLE TRACK

MODELS...THERE REMAIN SIGNIFICANT ALONG TRACK DIFFERENCES BETWEEN

MODELS DUE TO DIFFERENCES IN THE FORECAST FORWARD SPEED OF THE

CYCLONE.



SOME INTENSIFICATION IS EXPECTED IN THE SHORT TERM AS THE CYCLONE

MOVES OVER VERY WARM SEA SURFACE TEMPERATURES...WITH WATER

TEMPERATURES STEADILY DIMINISHING AFTER ABOUT 48 HOURS. THE MORE

SIGNIFICANT CHALLENGE WITH RESPECT TO THE INTENSITY FORECAST

HOWEVER CONTINUES TO HINGE ON THE INTERACTION BETWEEN THE CYCLONE

AND THE PERSISTENT SOUTHWESTERLY TO SOUTHERLY WIND SHEAR TO WHICH

IT WILL BE EXPOSED. AS THE DISTANCE BETWEEN THE CLOSED LOW ALOFT TO

THE NORTHWEST AND THE CYCLONE DECREASES...VERTICAL WIND SHEAR WILL

RAMP UP QUICKLY...INCREASING FROM CURRENT VALUES OF 15-20 KT TO

30-40 KT AFTER 72 HOURS. THE UPDATED INTENSITY FORECAST ANTICIPATES

SHORT TERM STRENGTHENING TO A TROPICAL STORM IN LINE WITH LATEST

SHIPS GUIDANCE. GRADUAL WEAKENING...AND TRANSITION TO AN

EXTRATROPICAL LOW...IS EXPECTED BEFORE DISSIPATION OCCURS ON DAY 5.

THIS WILL OCCUR AS THE SYSTEM GETS ENGULFED IN THE LARGE CYCLONIC

CIRCULATION ASSOCIATED WITH THE APPROACHING CLOSED LOW ALOFT.



THE LATEST FORECAST NECESSITATES THE ISSUANCE OF A TROPICAL

STORM WARNING FOR CENTRAL PORTIONS OF THE PAPAHANAUMOKUAKEA MARINE

NATIONAL MONUMENT...FROM FRENCH FRIGATE SHOALS TO MARO REEF

TO LISIANSKI ISLAND. GIVEN THE INHERENT UNCERTAINTIES IN TRACK AND

INTENSITY FORECASTS...A TROPICAL STORM WATCH HAS BEEN ISSUED FOR

THE AREA FROM LISIANSKI ISLAND TO PEARL AND HERMES.





FORECAST POSITIONS AND MAX WINDS



INIT  19/1500Z 19.4N 173.3W   30 KT  35 MPH

 12H  20/0000Z 20.5N 173.0W   35 KT  40 MPH

 24H  20/1200Z 22.1N 172.5W   40 KT  45 MPH

 36H  21/0000Z 23.9N 172.1W   45 KT  50 MPH

 48H  21/1200Z 26.5N 171.8W   45 KT  50 MPH

 72H  22/1200Z 31.2N 172.5W   40 KT  45 MPH

 96H  23/1200Z 37.5N 174.0W   40 KT  45 MPH...POST-TROP/EXTRATROP

120H  24/1200Z...DISSIPATED



$$



FORECASTER BIRCHARD