WTPA43 PHFO 202047 RRA

TCDCP3



TROPICAL STORM DARBY DISCUSSION NUMBER  37

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP052016

1100 AM HST WED JUL 20 2016



DARBY'S SATELLITE SIGNATURE HAS DEGRADED SLIGHTLY SINCE THE PREVIOUS

ADVISORY BUT CONVECTIVE CLOUD TOPS AS COLD AS -65C PERSIST NEAR THE

CENTER.  HOWEVER, MICROWAVE AND CONVENTIONAL SATELLITE IMAGERY

INDICATE THAT THE LOW LEVEL CENTER IS LOCATED ON THE SOUTHWEST SIDE

OF THE DEEP CONVECTION, WITH A 1615Z SSMI/S PASS HELPFUL IN LOCATING

THE CENTER.  SINCE THEN, VISIBLE IMAGERY SHOWS THAT THE CENTER HAS

BECOME PARTIALLY EXPOSED.  SUBJECTIVE DVORAK INTENSITY ESTIMATES

FROM PHFO/SAB BOTH INDICATED A CURRENT INTENSITY OF 3.0/45 KT, AND

THE INITIAL INTENSITY HAS BEEN LOWERED TO 45 KT FOR THIS ADVISORY.



THE INITIAL MOTION VECTOR IS 270/11 KT, WITH DARBY LOCATED WELL

SOUTH OF A MID-LEVEL RIDGE THAT IS SUPPORTED BY ANTICYCLONES

CENTERED FAR NORTH OF THE HAWAIIAN ISLANDS AND OVER THE CENTRAL

MAINLAND U.S.  THE FORECAST PHILOSOPHY WITH RESPECT TO TRACK HAS

CHANGED LITTLE FROM THE PREVIOUS ADVISORY.  THROUGH THE FIRST 48 TO

72 HOURS OF THE FORECAST, DARBY'S MOTION IS EXPECTED TO BE

INCREASINGLY INFLUENCED BY THE RIDGE BUILDING SOUTHEASTWARD FROM

NORTH OF THE HAWAIIAN ISLANDS.  THIS IS EXPECTED TO IMPART A MOTION

SLIGHTLY SOUTH OF DUE WEST UNTIL EARLY SATURDAY.  AFTER THAT TIME, A

BREAK IN THE RIDGE IS STILL EXPECTED IN RESPONSE TO A SOUTHWARD-

DIGGING LOW ALOFT.  THIS IS EXPECTED TO CAUSE DARBY TO TURN SHARPLY

TOWARD THE NORTHWEST AND NORTH ON DAYS 4 AND 5 AS IT BECOMES

EMBEDDED WITHIN DEEP SOUTHERLY FLOW BETWEEN THE LOW ALOFT AND A

RIDGE EXTENDING WESTWARD FROM THE EASTERN PACIFIC.  THE UPDATED=