WTPA41 PHFO 301506 RRA

TCDCP1



TROPICAL STORM WALAKA DISCUSSION NUMBER   4

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP012018

500 AM HST SUN SEP 30 2018



THE SATELLITE PRESENTATION OF WALAKA HAS IMPROVED SIGNIFICANTLY

OVERNIGHT, WITH A LARGE AREA OF DEEP CONVECTION FEATURING

-80 TO -90C CLOUD TOPS OVER THE DIFFICULT TO LOCATE LOW LEVEL

CIRCULATION CENTER. DUE TO THE LACK OF ANY RECENT MICROWAVE IMAGERY

TO ASSIST IN CONFIDENTLY DETERMINING THE CENTER LOCATION, THE

INITIAL POSITION WAS BASED ON EXTRAPOLATION FROM EARLIER MICROWAVE

PASSES AND CURRENT GEOSTATIONARY SATELLITE ANIMATIONS. THE LATEST

SATELLITE INTENSITY ESTIMATES FROM PHFO AND SAB WERE 3.0 (45

KNOTS), AND 2.5 (35 KNOTS) FROM JTWC. MEANWHILE, THE ADT VALUE FROM

UW-CIMSS CONTINUES TO APPEAR UNREALISTICALLY HIGH AT 4.1 (67 KNOTS).

GIVEN THE IMPROVEMENT IN ORGANIZATION AND APPEARANCE OF WALAKA SINCE

THE 12Z SATELLITE INTENSITY ESTIMATES, THE INITIAL INTENSITY FOR

THIS ADVISORY HAS BEEN INCREASED TO 50 KNOTS. THE INITIAL MOTION HAS

BEEN SET AT 275/14 KNOTS.



WALAKA IS EXPECTED TO TRACK NEARLY DUE WEST ALONG THE SOUTH SIDE OF

A SUBTROPICAL RIDGE TODAY AND TONIGHT, WITH A GRADUAL DECREASE IN

FORWARD SPEED. A DEEP NORTH PACIFIC UPPER TROUGH WILL ERODE THE

SUBTROPICAL RIDGE TO THE NORTH OF WALAKA ON MONDAY AND STEER THE

TROPICAL CYCLONE NORTHWESTWARD, WITH A TURN TOWARD THE NORTH

EXPECTED ON TUESDAY ALONG WITH AN INCREASE IN FORWARD SPEED. THE

SYSTEM SHOULD THEN SLOW DOWN AND BE PULLED BACK TO THE NORTH-

NORTHWEST ON THURSDAY AS IT BEGINS TO INTERACT WITH THE UPPER

TROUGH. THE GUIDANCE IS FAIRLY TIGHTLY CLUSTERED THROUGH ENTIRE

FORECAST CYCLE, WITH A BIT MORE SPREAD NOTED BY FORECAST HOUR 120.