Advisories

WDPN31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 037//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 143.6E
   INITIAL INTENSITY: 85 KTS
   GEOGRAPHIC REFERENCE: 206 NM SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 27 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A RAPIDLY 
DEGRADING TYPHOON (TY) CHARACTERIZED BY A RAGGED, BANDED EYE FEATURE, 
FRAGMENTED POCKETS OF DEEP CONVECTION, AND AN ERODING NORTHWESTERN 
QUADRANT ASSOCIATED WITH MID-TROPOSPHERIC DRY AIR ENTRAINMENT AND 
ENHANCED VERTICAL WIND SHEAR (VWS). THE VORTEX HAS REMAINED QUASI-
STATIONARY WITHIN A 40-NM RADIUS OVER THE PAST 24 HOURS, INDUCING 
PRONOUNCED OCEANIC UPWELLING. ALTHOUGH IN-SITU SEA SURFACE 
TEMPERATURE (SST) OBSERVATIONS ARE UNAVAILABLE, COUPLED OCEAN-
ATMOSPHERE THERMODYNAMIC MODELS SUGGEST UPWELLED SSTS MAY BE AS LOW 
AS 24 CELSIUS BENEATH THE INNER CORE, THOUGH ASSESSED SSTS ARE 
BETWEEN 25 AND 27 CELSIUS. A PARTIAL 011256Z GPM 89-GHZ MICROWAVE 
PASS DEPICTS RAPID AND SEVERE STRUCTURAL EROSION OF THE INNER CORE OF 
TY 30W, PARTICULARLY WHEN COMPARED TO THE ANTECEDENT 010912Z SSMIS 
89-GHZ PASS. THE ENTIRE WESTERN SEMICIRCLE OF THE INNER-CORE 
CONVECTIVE STRUCTURE HAS DISSIPATED, RESTRICTING RESIDUAL DEEP 
CONVECTION TO THE DOWN-SHEAR EASTERN PERIPHERY. A 011118Z ASCAT PASS 
PROVIDES A HIGH-CONFIDENCE CENTER FIX FOR THE INITIAL POSITION AS 
WELL AS A HIGH-CONFIDENCE ASSESSMENT OF THE GALE- AND STORM-FORCE 
WIND RADII, WHICH REMAIN HIGHLY SYMMETRIC. THE INITIAL INTENSITY IS 
ASSESSED CONSERVATIVELY AT 85 KTS, SUPPORTED BY THE OBJECTIVE AND 
SUBJECTIVE INTENSITY ESTIMATES OUTLINED BELOW. AS THE CIMSS ADT 
CURRENTLY APPLIES A DVORAK WEAKENING CONSTRAINT OF 0.5 T-NUMBER PER 
SIX HOURS, THE UNCONSTRAINED ADJUSTED AND RAW-T INTENSITY METRICS ARE 
LIKELY MORE REPRESENTATIVE OF THE TRUE INTENSITY IN THIS CASE, 
INDICATING T4.5 (77 KTS) OR LOWER. ENVIRONMENTAL CONDITIONS ARE 
MARGINALLY UNFAVORABLE, WITH UPWELLING-INDUCED COLD WAKE SSTS, MID-
TROPOSPHERIC DRY AIR INTRUSION, AND ENHANCED WESTERLY MID-LEVEL SHEAR 
OFFSETTING THE ROBUST DUAL-CHANNEL UPPER-TROPOSPHERIC OUTFLOW ALOFT

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: TYPHOON (TY) 30W IS TRAPPED IN A 
COMPETING STEERING PATTERN, WITH DEEP SUBTROPICAL RIDGING (STR) 
ANCHORED BOTH TO THE EAST AND THE WEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.0 - 90 KTS
   CIMSS SATCON: 90 KTS AT 010913Z
   CIMSS ADT: 97 KTS AT 011130Z
   CIMSS AIDT: 98 KTS AT 011130Z
   CIMSS D-MINT: 91 KTS AT 011055Z
   CIMSS D-PRINT: 90 KTS AT 011200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 0-5 KTS
   SST: 25-27 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD
   OTHER FACTORS: UPWELLING INDUCED, LOCALIZED COOL SSTS. 

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 30W HAS COMMENCED A SLOW WESTWARD DRIFT AFTER 
EXECUTING A CYCLONIC LOOP OVER THE PAST 24 HOURS, WITH THE LOW-LEVEL 
CIRCULATION CENTER (LLCC) NOW POSITIONED APPROXIMATELY 40 NM SOUTH OF 
ITS 24-HOUR POSITION. TY 30W REMAINS EMBEDDED WITHIN A WEAK-STEERING 
COL REGION BETWEEN COMPETING STR CELLS TO THE EAST AND WEST; 
CONSEQUENTLY, TRANSLATION SPEEDS WILL REMAIN SLOW THROUGH THE NEXT 48 
TO 60 HOURS. OVER THE NEXT 12 HOURS, THE SYSTEM WILL ESTABLISH A 
STEADIER WESTWARD TRAJECTORY AS THE BROADER SYNOPTIC PATTERN 
RETROGRADES WESTWARD WHILE RETAINING ITS OVERALL ORIENTATION AND 
RELATIVE POSITIONAL GEOMETRY. BETWEEN TAU 36 AND TAU 48, A TRANSIENT 
MID-LATITUDE SHORTWAVE TROUGH WILL PROPAGATE TO THE NORTH AND ERODE 
THE NORTHEASTERN PERIPHERY OF THE WESTERN STR. BY TAU 60, THE WESTERN 
RIDGE IS FORECAST TO RETROGRADE INTO SOUTHERN CHINA, WHILE THE 
EASTERN RIDGE AMPLIFIES AND EXPANDS WESTWARD, ASSUMING THE DOMINANT 
STEERING INFLUENCE. TY 30W WILL RECURVE POLEWARD BY TAU 60, CREST THE 
STR AXIS SHORTLY THEREAFTER, AND ACCELERATE NORTHEASTWARD BY TAU 72. 
AFTER TAU 72, TY 30W WILL ACCELERATE RAPIDLY NORTHEASTWARD AT 
TRANSLATION SPEEDS EXCEEDING 30 KTS, PHASING WITH THE BAROCLINIC MID-
LATITUDE WESTERLIES EAST OF JAPAN. REGARDING INTENSITY, THE SYSTEM 
WILL STEADILY SPIN DOWN BY AN ADDITIONAL 10-15 KTS OVER THE NEXT 12 
HOURS AS IT TRAVERSES THE UPWELLED COLD-WAKE POOL. AFTER TAU 24, AS 
TY 30W EMERGES OVER UNPERTURBED, CLIMATOLOGICALLY TYPICAL SSTS AND 
ELEVATED OCEAN HEAT CONTENT (OHC) WATERS, IT WILL RE-INTENSIFY UNDER 
MORE FAVORABLE THERMODYNAMIC AND DYNAMIC CONDITIONS. AFTER TAU 72, 
THE SYSTEM WILL RAPIDLY WEAKEN DUE TO STRONG BAROCLINIC VWS, STEEPLY 
COOLING MERIDIONAL SST GRADIENTS, AND THE ONSET OF EXTRATROPICAL 
TRANSITION (ETT) BY TAU 96. THE VORTEX WILL BECOME EMBEDDED IN THE 
MID-LATITUDE JET, UNDERGO BAROCLINIC FRONTOGENESIS, AND COMPLETE ETT 
AS A STORM-FORCE EXTRATROPICAL CYCLONE NO LATER THAN TAU 120. 

MODEL DISCUSSION: TRACK GUIDANCE CONTINUES TO EXHIBIT SUBSTANTIAL 
SPREAD, PARTICULARLY REGARDING ALONG-TRACK TRANSLATION SPEED AND THE 
ZONAL EXTENT OF WESTWARD PROGRESSION PRIOR TO POLEWARD RECURVATURE. 
CONSEQUENTLY, THE MULTI-MODEL TRACK CONSENSUS (CONW) MEMBERSHIP HAS 
BEEN SELECTIVELY FILTERED TO EXCLUDE EXTREME OUTLIERS (NAVGEM, UKMET 
ENSEMBLE, AND GALWEM) THAT WERE INTRODUCING A DISPROPORTIONATE BIAS 
INTO THE CONSENSUS MEAN. THE ADJUSTED CONW COMPRISES DETERMINISTIC 
AND ENSEMBLE GLOBAL GUIDANCE (GFS, ECMWF, GEFS, AND EPS) ALONG WITH 
SIX AI MODELS. THE REVISED CONSENSUS EXHIBITS TIGHT CROSS-TRACK 
CLUSTERING, WITH A SPREAD OF ONLY 50 NM THROUGH TAU 72, BOUNDED BY 
THE ECMWF ON THE WESTERN PERIPHERY AND THE GFS AND GEFS ON THE 
EASTERN PERIPHERY OF THE GUIDANCE ENVELOPE. EVEN BEYOND TAU 72, 
CROSS-TRACK DISPERSION REMAINS WELL CONSTRAINED AT ONLY 110 NM AT TAU 
120. CONVERSELY, ALONG-TRACK PHASE UNCERTAINTY IS PRONOUNCED EVEN 
WITHIN THE FILTERED CONSENSUS, PARTICULARLY DURING POST-RECURVATURE 
ACCELERATION AFTER TAU 72. BY TAU 96, ALONG-TRACK SPREAD EXPANDS TO 
150 NM BETWEEN THE SLOWER ADJUSTED CONW AND THE FASTER ECMWF-AIFS, 
DIVERGING FURTHER BY TAU 120 TO 840 NM BETWEEN THE SLOWER 
DETERMINISTIC ECMWF AND THE ACCELERATED ECMWF-AIFS. THE ADJUSTED CONW 
LIES WITHIN A COMPACT CLUSTER COMPRISING GOOGLE DEEPMIND (GDM), GEFS, 
AND ECMWF-AIFS. THE OFFICIAL JTWC TRACK FORECAST IS POSITIONED NEAR 
THE ADJUSTED CONW THROUGH THE FORECAST PERIOD. INTENSITY GUIDANCE 
REMAINS IN RELATIVELY GOOD OVERALL AGREEMENT. THE COUPLED OCEAN-
ATMOSPHERE MESOSCALE MODELS CONTINUE TO DEPICT MORE PRONOUNCED NEAR-
TERM WEAKENING, FOLLOWED BY A SUBSEQUENT RE-INTENSIFICATION PHASE 
(WITH HAFS-A PROJECTING THE MOST AGGRESSIVE RE-INTENSIFICATION TO 105 
KTS) AND RAPID BAROCLINIC WEAKENING AFTER TAU 72. THE MAJORITY OF THE 
INTENSITY GUIDANCE SUPPORTS A SECONDARY PEAK INTENSITY OF 80-90 KTS 
NEAR TAU 48. THE OFFICIAL JTWC INTENSITY FORECAST CLOSELY TRACKS THE 
HWRF SOLUTION THROUGH TAU 60, THEN TRANSITIONS TO THE MULTI-MODEL 
INTENSITY CONSENSUS (ICNW) THROUGH THE REMAINDER OF THE FORECAST 
PERIOD.  

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