WTPA41 PHFO 302047 RRA

TCDCP1



TROPICAL STORM WALAKA DISCUSSION NUMBER   5

NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   CP012018

1100 AM HST SUN SEP 30 2018



DEEP CONVECTION AROUND WALAKA HAS ASSUMED A GOOD WRAPPING PATTERN

THIS MORNING, INCREASING POSITION CONFIDENCE WITH DEVELOPMENT OF A

RELATIVE DRY SLOT ALONG THE SOUTHEAST QUADRANT OF THE CIRCULATION.

THE NORTHERN PORTION OF THIS SLOT, WHICH IS ALSO QUITE WARM, MAY

SOON DEVELOP INTO AN EYE. CONVECTIVE TOPS REMAIN QUITE COLD, IN THE

-80 TO -90 DEGREE C RANGE. SUBJECTIVE DVORAK CURRENT INTENSITY

ESTIMATES RANGED FROM 3.0/45 KT FROM JTWC TO 4.0/65 KT FROM SAB.

PHFO PROVIDED 3.5/55 KT WHILE ADT FROM UW-CIMSS WAS 58 KT. THE

INITIAL INTENSITY IS SET AT 55 KT BASED ON A MIX OF THESE

ESTIMATES.



WALAKA IS TRACKING SLIGHTLY NORTH OF DUE WEST ALONG THE SOUTHERN

FLANK OF THE SUBTROPICAL RIDGE. GLOBAL MODELS SHOW A DEEP UPPER

TROUGH WILL DIG SOUTHWARD, ERODING THE WESTERN EDGE OF THE

SUBTROPICAL RIDGE TO THE NORTH OF WALAKA ON MONDAY. THIS WILL STEER

THE TROPICAL CYCLONE NORTHWESTWARD, THEN NORTHWARD ON TUESDAY. THE

SYSTEM SHOULD CURVE BACK NORTH-NORTHWESTWARD ON THURSDAY AS IT

BEGINS TO INTERACT WITH THE UPPER TROUGH. TRACK GUIDANCE IS VERY

TIGHTLY CLUSTERED THROUGH FRIDAY, GREATLY INCREASING CONFIDENCE IN

THE TIMING OF THE CURVE NORTHWARD. OUR FORECAST CLOSELY FOLLOWS THE

PREVIOUS ONE, WITH A SLIGHT TAP TO THE WEST BEYOND 36 HOURS NEEDED

TO STAY WITHIN THE VERY TIGHT GUIDANCE ENVELOPE.  FSSE AND CTCI

MARK THE RIGHT AND LEFT ENVELOPE LIMITS, WITH LITTLE DIFFERENCE

BETWEEN THEM THROUGH DAY 3. WITH THE OFFICIAL FORECAST TRACK

BRINGING THE CENTER OF WALAKA VERY NEAR JOHNSTON ATOLL ON TUESDAY, A