WDPN31 PGTW 290300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 12W (DOLPHIN) WARNING NR 009//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1N 169.1E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 343 NM SOUTH-SOUTHEAST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
THE CONVECTIVE SIGNATURE OF TYPHOON (TY) 12W HAS DEGRADED ON
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI). THE EYE HAS COOLED,
AND CLOUD TOP TEMPERATURES ASSOCIATED WITH THE COMPACT CENTRAL
DENSE OVERCAST (CDO) HAVE WARMED. THIS DETERIORATION IS THE RESULT
OF AN ONGOING EYEWALL REPLACEMENT CYCLE (ERC), WHICH IS CLEARLY
EVIDENCED BY THE CONCENTRIC CONVECTIVE RINGS IN THE 281841Z SSMIS
91 GHZ IMAGE. THE SURROUNDING ENVIRONMENT IS LARGELY FAVORABLE. A
SUBTROPICAL JET ALONG 22N LATITUDE CONTINUES TO ENHANCE POLEWARD
OUTFLOW ALOFT, WHILE WARM SEA SURFACE TEMPERATURES (SST) OF 29-30
DEGREES CELSIUS AND HIGH OCEAN HEAT CONTENT (OHC) OF 125 KJ PER CM2
PROVIDE AMPLE ENERGY. THESE FACTORS ARE SLIGHTLY OFFSET BY LOW TO
MODERATE EASTERLY VERTICAL WIND SHEAR (VWS), WHICH IS EXERTING SOME
PRESSURE ON THE EASTERN PERIPHERY OF THE VORTEX. THE STORM'S
TROCHOIDAL MOTION RESULTED IN A BRIEF STAGNATION IN FORWARD SPEED
BETWEEN 281600Z AND 281900Z. SINCE THEN, THE SYSTEM HAS RESUMED A
STILL-WOBBLY NORTHWESTWARD MOTION AT 09 KTS. A CRUCIAL 282153Z
ASCAT-C PASS REVEALED A COMPACT WIND FIELD, WITH GALE-FORCE WINDS
EXTENDING OUTWARD TO 75 NM AND STORM-FORCE WINDS UP TO 40 NM FROM
THE CENTER. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE PINHOLE EYE. DUE TO THE DEGRADED STRUCTURE OF TY 12W,
THE INITIAL INTENSITY HAS BEEN LOWERED TO 120 KTS, WHICH IS IN LINE
WITH THE AGENCY FIXES AND THE OBJECTIVE INTENSITY ESTIMATES FROM
CIMSS RANGING FROM 109 KTS TO 126 KTS.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA

CURRENT STEERING MECHANISM: THE SOUTHWESTERN PERIPHERY OF A
DEEP-LAYER SUBTROPICAL RIDGE (STR) COMPLEX OVER THE CENTRAL NORTH
PACIFIC

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T6.5 - 127 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T6.0 - 115 KTS
   KNES: T6.5 - 127 KTS
   PHFO: T5.5 - 102 KTS
   CIMSS SATCON: 97 KTS AT 282030Z
   CIMSS ADT: 117 KTS AT 290000Z
   CIMSS AIDT: 109 KTS AT 290000Z
   CIMSS D-MINT: 122 KTS AT 282303Z
   CIMSS D-PRINT: 115 KTS AT 290000Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: HIGH

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TY 12W WILL MAINTAIN A NORTHWESTWARD
TRAJECTORY THROUGH TAU 96, STEERED ALONG THE SOUTHWESTERN PERIPHERY
OF A COMPLEX RIDGE OVER THE CENTRAL NORTH PACIFIC. TOWARD THE END
OF THE FORECAST PERIOD, A LONGWAVE TROUGH OVER THE KURIL ISLANDS
WILL WEAKEN, ALLOWING FOR THE STR TO BUILD NORTH OF THE SYSTEM.
THIS CHANGE IN THE STEERING PATTERN WILL INDUCE A WESTWARD TURN AT
TAU 120. TY 12W IS CURRENTLY ON A TEMPORARY WEAKENING TREND, WHICH
WILL CONTINUE UNTIL THE ERC COMPLETES. GIVEN THE COMPACT NATURE OF
THE SYSTEM, THE FORECAST CALLS FOR THE ERC TO CONCLUDE WITHIN THE
NEXT 6-12 HOURS. ONCE THIS OCCURS, ANOTHER PERIOD OF SIGNIFICANT
INTENSIFICATION WILL COMMENCE. THE PREDICTED ENVIRONMENT FOR THIS
SYSTEM APPEARS TO BE EVEN MORE CONDUCIVE THAN WHAT IT EXPERIENCED
IN THE PREVIOUS 24 HOURS. THE SYSTEM WILL TRAVERSE OVER
EXCEPTIONALLY WARM SST OF 31-32 DEGREES CELSIUS AND POCKETS OF VERY
HIGH OHC EXCEEDING 150 KJ PER CM2. FURTHERMORE, THE LOW TO MODERATE
VWS CURRENTLY IMPACTING THE SYSTEM WILL EASE TO 5-10 KTS AFTER TAU
36. THEREFORE, THE FORECAST CALLS FOR TY 12W TO RAPIDLY INTENSIFY
AND ACHIEVE A SECOND, HIGHER PEAK INTENSITY OF 150 KTS. ANY
SUBSEQUENT ERC EVENTS WILL LIKELY LEAD TO LESS PREDICTABLE
INTENSITY FLUCTUATIONS AND AN EXPANSION OF THE WIND FIELD. AT THE
END OF THE FORECAST PERIOD, THE SYSTEM WILL WEAKEN AS IT ENCOUNTERS
LOWER OHC AND A MORE COMPLEX SHEAR ENVIRONMENT.

MODEL DISCUSSION: THE FULL MODEL SUITE CONCURS ON A NORTHWESTWARD
TRACK FOLLOWED BY A TURN TOWARD THE WEST-NORTHWEST IN THE EXTENDED
FORECAST PERIOD. THE GUIDANCE IS TIGHT, WITH A CROSS-TRACK SPREAD
THAT INCREASES FROM 45 NM AT TAU 48 TO 105 NM AT TAU 72, ONCE
NAVGEM IS EXCLUDED AS A CONSISTENT POLEWARD OUTLIER. THE SPREAD
INCREASES MORE SIGNIFICANTLY AT TAU 96 AND TAU 120, DRIVEN BY THE
UNCERTAINTY IN THE TIMING OF THE WESTWARD TURN. THE JGSM, ECMWF,
AND GALWEM SOLUTIONS ARE AMONG THE FASTER MEMBERS, DEPICTING AN
EARLIER TURN, WHILE THE AI MEMBERS FAVOR A SLIGHTLY LATER ONE. THE
JTWC FORECAST TRACK IS POSITIONED NEAR THE CONSENSUS AND IS CLOSEST
TO THE GFS AND DEEPMIND MODELS. RELIABLE INTENSITY GUIDANCE FOR
THIS FORECAST IS LIMITED AND SHOWS SIGNIFICANT SPREAD. THE
INTERPOLATED HAFS-A OUTPUT NOW SHOWS A PEAK OF 130 KTS,
REPRESENTING A SHARP DROP OF 40 KTS FROM THE PREVIOUS RUN AND A
SEVERE DEPARTURE FROM THE PREVIOUSLY CONSISTENT 160+ KT OUTPUT,
WHEREAS ITS 281800Z PARENT MODEL STILL DEPICTED A 150 KT PEAK.
GIVEN THIS UNCERTAINTY, THE JTWC INTENSITY FORECAST IS INITIALLY
ANCHORED TO THE OBSERVED SATELLITE TRENDS, ACCOUNTING FOR THE
ONGOING ERC WITH SLIGHT WEAKENING AT TAU 12. THEREAFTER, THE
FORECAST MAINTAINS THE PHILOSOPHY OF RAPID INTENSIFICATION AFTER
THE ERC COMPLETES. CONSEQUENTLY, THE JTWC FORECAST IS SET ABOVE THE
BULK OF THE CURRENT GUIDANCE. THE MAJORITY OF THE AIDS SHOW GRADUAL
WEAKENING AT TAU 96-120.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: LOW
   INTENSITY 72-120 HR: LOW//
NNNN