Advisories

WDPN31 PGTW 310900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 032//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.2N 142.9E
   INITIAL INTENSITY: 115 KTS
   GEOGRAPHIC REFERENCE: 179 NM SOUTH-SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 50 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TYPHOON (TY) 
30W MAINTAINING A WELL-DEFINED EYE FEATURE, WHICH HAS CONSTRUCTED 
SLIGHTLY OVER THE PAST SIX HOURS TO 37 NM. MULTIPLE MESOVORTICES ARE 
CLEARLY VISIBLE ROTATING ALONG THE INNER EYEWALL, GENERATING A 
WAVENUMBER-3 ASYMMETRY. OVER THE PAST SIX HOURS, THE PRIMARY EYEWALL 
HAS BEGUN TO DEGRADE AND BECOME MORE ASYMMETRIC, THOUGH INNER-EYE 
TEMPERATURES REMAIN NEAR 19C. A 310300Z AMSR3 COLOR-ENHANCED 89 GHZ 
MICROWAVE IMAGE DEPICTS A SYMMETRICAL INNER EYEWALL, ROUGHLY 10 NM 
WIDE, SEPARATED BY A THIN (APPROXIMATELY 10 NM WIDE) MOAT FEATURE 
FROM A ROBUST, 40 NM WIDE SECONDARY EYEWALL. THE CIMSS M-PERC 
HOVMOLLER DIAGRAM CLEARLY INDICATES THAT SECONDARY EYEWALL FORMATION 
(SEF) BEGAN AROUND 301800Z, AND THE SECONDARY EYEWALL HAS SINCE BEEN 
GRADUALLY CONTRACTING IN SIZE WHILE THE INNER EYEWALL SLOWLY 
DEGRADES. AT THE SYNOPTIC SCALE, A WEAK FRONTAL BOUNDARY IS LOCATED 
APPROXIMATELY 400 NM NORTHWEST OF TY 30W, MOVING SOUTHEASTWARD. IN 
THE UPPER-LEVELS, ANIMATED WATER VAPOR IMAGERY DEPICTS A MESOSCALE 
POINT-SOURCE OUTFLOW PATTERN DIRECTLY OVERLYING 30W, AND DUAL UPPER-
TROPOSPHERIC ANTICYCLONES AT 200 MB BOTH EAST AND WEST OF THE SYSTEM, 
PROVIDING STRONG RADIAL OUTFLOW ENHANCED BY A ROBUST POLEWARD OUTFLOW 
CHANNEL. THE INITIAL MOTION VECTOR IN THE ANALYSIS IS NORTH AT 08 
KNOTS; HOWEVER, THIS SMOOTHS OUT A TEMPORARY NORTHEASTWARD TRAJECTORY 
OBSERVED FROM ABOUT 0300Z TO 0600Z BASED ON THE ANIMATED MSI. THE 
INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE WELL-
DEFINED EYE IN THE MSI. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM 
CONFIDENCE, BASED ON A BLEND OF THE OBJECTIVE AND SUBJECTIVE 
INTENSITY ESTIMATES OUTLINED BELOW. ENVIRONMENTAL CONDITIONS ARE 
FAVORABLE OVERALL, BUT REMAIN TEMPERED BY THE ONGOING EYEWALL 
REPLACEMENT CYCLE (ERC) AND THERMODYNAMIC LIMITATIONS FROM SELF-
INDUCED OCEANIC UPWELLING AS THE SYSTEM DECELERATES AND BECOMES 
QUASI-STATIONARY.

INITIAL WIND RADII BASIS: EYEWALL REPLACEMENT CYCLE (ERC) AND
OCEANIC UPWELLING. 

CURRENT STEERING MECHANISM: WEAK STEERING PATTERN INFLUENCED BY A 
BIFURCATED SUBTROPICAL RIDGE (STR) TO THE EAST AND TO THE WEST NEAR 
TAIWAN, AND A SHALLOW MID-LATITUDE TROUGH TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   CIMSS SATCON: 108 KTS AT 310500Z
   CIMSS ADT: 112 KTS AT 310530Z
   CIMSS AIDT: 110 KTS AT 310530Z
   CIMSS D-PRINT: 117 KTS AT 310600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON (TY) 30W HAS BEGUN TURNING POLEWARD IN 
REACTION TO THE IMMINENT PASSAGE OF A MODERATELY DEEP MID-LATITUDE 
TROUGH TO THE NORTH, WHICH IS ERODING THE WESTERN FLANK OF THE 
EASTERN STR. WHILE THE TROUGH IS STRONG ENOUGH TO WEAKEN THE RIDGE, 
GLOBAL DYNAMICAL MODELS SUGGEST THAT IT LACKS THE AMPLITUDE AND 
DYNAMICS NECESSARY TO FACILITATE EXTRA-TROPICAL TRANSITION OR PULL TY 
30W POLEWARD INTO THE MID-LATITUDE WESTERLIES AT THIS TIME. THUS, TY 
30W REMAINS TRAPPED IN A COL BETWEEN COMPETING RIDGES TO THE EAST AND 
WEST, AND THE TROUGH TO THE NORTH. THE SYSTEM WILL DRIFT SLOWLY 
NORTH-NORTHEASTWARD FOR THE NEXT 12 HOURS IN RESPONSE TO A SLIGHT 
REORIENTATION OF THE EASTERN STR, AS WELL AS THE APPROACH OF THE WEAK 
FRONTAL BOUNDARY MOVING IN FROM THE NORTHWEST. BY TAU 24, THE SYSTEM 
BECOMES QUASI-STATIONARY, AND MAY PERFORM A CYCLONIC LOOP, AS THE 
FRONTAL BOUNDARY WEAKENS AND PROPAGATES OFF TO THE NORTHEAST, THE 
DEEP-LAYER RIDGE TO THE EAST ERODES AND RETROGRADES, AND THE STR TO 
THE WEST BUILDS SLIGHTLY, TRAPPING TY 30W INSIDE A WEAK AND COMPETING 
STEERING PATTERN. FROM TAU 36 TO TAU 48, THE ENTIRE COL REGION BEGINS 
TO SHIFT WESTWARD, AS BOTH STR CENTERS TRANSLATE WESTWARD WHILE 
MAINTAINING THE SAME OVERALL ORIENTATION TO ONE ANOTHER. BY TAU 60, 
THE STR OVER TAIWAN WEAKENS AND MOVES WESTWARD, WHILE A SUBSEQUENT 
MID-LATITUDE TROUGH ERODES THE REMNANT RIDGING TO THE NORTH OF TY 
30W. AT THE SAME TIME, A SECOND, MORE ROBUST FRONTAL BOUNDARY BEGINS 
MOVING SOUTH FROM JAPAN. TY 30W WILL BEGIN A RAPID RECURVE AFTER TAU 
60, ACCELERATING NORTHEASTWARD AFTER ROUNDING THE DEEP-LAYER STR 
AXIS. REGARDING INTENSITY, TY 30W WILL FACE TWO NEAR-TERM NEGATIVE 
INFLUENCES; THE ONGOING ERC AND OCEANIC UPWELLING. DUE TO THE 
INCREASING INFLUENCE OF COOLER UPWELLED SEA SURFACE TEMPERATURES 
(SSTS), THE ERC IS UNLIKELY TO FULLY COMPLETE, AND IN FACT, THE 
SYSTEM MAY WEAKEN MORE APPRECIABLY THAN ANTICIPATED IN THE CURRENT 
FORECAST, DEPENDING ON THE PACE OF THE THERMAL UPWELLING. AFTER THE 
SYSTEM MOVES AWAY FROM THE UPWELLING REGION (BY TAU 48), IT IS 
EXPECTED TO ENCOUNTER MORE FAVORABLE OCEANIC CONDITIONS AND TAP INTO 
AN ENHANCED POLEWARD OUTFLOW CHANNEL, CREATING THE CONDITIONS FOR IT 
TO MAINTAIN INTENSITY OR RECOVER SLIGHTLY IF IT WEAKENS MORE THAN 
FORECAST. AS THE SYSTEM RECURVES AFTER TAU 72, MORE SIGNIFICANT 
WEAKENING IS EXPECTED AS THE SYSTEM ENCOUNTERS INCREASED VERTICAL 
WIND SHEAR, DRY AIR ENTRAINMENT, AND DECREASING SSTS. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN 
GOOD AGREEMENT ON THE OVERALL TRACK SCENARIO, WITH ALL MEMBERS OF THE 
GUIDANCE SUITE SUPPORTING A QUASI-STATIONARY MOTION FROM TAU 12 TO 
TAU 24, FOLLOWED BY A SHORT PERIOD OF WESTWARD TRANSLATION, THEN A 
RECURVATURE AFTER TAU 60. DISCOUNTING THE EGRR AND UKMET (WHICH ARE 
UNREALISTICALLY SLOW AND TRACK TOO FAR WEST) OUTLIERS, THE REMAINDER 
OF THE GUIDANCE DEPICTS A CROSS-TRACK SPREAD OF 165 NM AT TAU 72. THE 
ECMWF ENSEMBLE MEAN IS CLOSELY ALIGNED WITH ITS AI VERSION ON THE 
INSIDE (EAST) OF THE TRACK PACKAGE, WHILE THE GFS AND NAVGEM ARE 
CLUSTERED ON THE OUTSIDE (WEST) EDGE. THE REMAINDER OF THE GUIDANCE 
IS ROUGHLY EVENLY SPREAD BETWEEN THE OUTLIERS. THE JTWC FORECAST IS 
PLACED NEAR THE AI-CONSENSUS MEAN AND THE NEARBY ECMWF DETERMINISTIC 
TRACKER WITH MEDIUM CONFIDENCE THROUGH TAU 72. BEYOND TAU 72, THE 
CROSS-TRACK SPREAD REMAINS ROUGHLY THE SAME, UP TO 180 NM BETWEEN THE 
NAVGEM ON THE WEST SIDE, AND THE ECEPS AND AI-ECEPS ON THE EAST. 
ALONG-TRACK SPREAD INCREASES TO NEARLY 300 NM BETWEEN THE SLOW 
CONSENSUS MEAN (CONW) AND THE PROGRESSIVE AIFS TRACKERS. THE 
REMAINDER OF THE JTWC FORECAST IS PLACED NEAR THE AI-CONSENSUS, 
OPERATIONAL GOOGLE DEEPMIND (GDM), AND ECMWF THROUGH TAU 120 WITH 
MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD AGREEMENT, DEPICTING 
A STEADY WEAKENING TO BETWEEN 85-95 KNOTS BY TAU 36, THEN EITHER A 
FLAT INTENSITY TREND OR SLIGHT RE-INTENSIFICATION FROM TAU 48 TO TAU 
72, FOLLOWED BY MORE RAPID WEAKENING THROUGH THE END OF THE FORECAST 
PERIOD. THE JTWC FORECAST IS PLACED NEAR THE HWRF TRACKER AND THE 
INTENSITY CONSENSUS (ICNW) THROUGH THE FORECAST PERIOD WITH MEDIUM 
CONFIDENCE. 

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