Advisories

WDPN31 PGTW 010900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 036//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.3N 144.1E
   INITIAL INTENSITY: 90 KTS
   GEOGRAPHIC REFERENCE: 215 NM SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 29 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A RAPIDLY 
DETERIORATING, COMPACT SYSTEM, WITH THE PREVIOUSLY WELL-DEFINED EYE 
FEATURE RAPIDLY FILLING AND DISSIPATING WITHIN THE PAST TWO HOURS. 
THE CENTRAL DENSE OVERCAST (CDO) CLOUD TOPS HAVE CONTINUED TO WARM 
AND HAVE BECOME INCREASINGLY ASYMMETRIC AND RAGGED AS THE EYE HAS 
BECOME CLOUD-FILLED. A 010614Z SSMIS 91GHZ MICROWAVE IMAGE REVEALS 
PRONOUNCED STRUCTURAL DEGRADATION OF TYPHOON (TY) 30W, WITH LIMITED 
CONVECTIVE BANDING CONFINED TO THE SOUTHWESTERN FLANK AND A 
FRAGMENTED REMNANT EYEWALL THAT IS BREACHED TO THE NORTHWEST. CIMSS 
DEEP-LAYER VERTICAL WIND SHEAR (VWS) ANALYSIS INDICATES LOW (5-10 
KTS) NORTHWESTERLY SHEAR, WHILE MODEL-DERIVED SOUNDINGS INDICATE 
MODERATE TO HIGH (20-25 KTS) NORTHWESTERLY MID-LEVEL SHEAR AND 
CONCOMITANT DRY AIR ENTRAINMENT, CORROBORATING THE STRUCTURAL 
ASYMMETRY OBSERVED IN THE MICROWAVE IMAGERY. IN THE UPPER LEVELS, THE 
EQUATORWARD BASE OF A 200-HPA TROUGH IS POSITIONED JUST NORTHWEST OF 
TY 30W, WHILE 200-HPA ANTICYCLONES ARE LOCATED TO THE EAST AND 
SOUTHWEST, AND A COMPACT UPPER-LEVEL ANTICYCLONIC POINT SOURCE 
OVERLAYS THE SYSTEM. OUTFLOW REMAINS STRONGEST POLEWARD, WHILE A 
WEAKER EQUATORWARD OUTFLOW CHANNEL PERSISTS. WHILE NO IN-SITU OCEANIC 
MEASUREMENTS EXIST, COUPLED OCEAN-ATMOSPHERE MODEL FIELDS INDICATE 
THAT SUBSTANTIAL OCEANIC UPWELLING HAS ALREADY OCCURRED AS TY 30W 
EXECUTED A CYCLONIC LOOP WHILE REMAINING QUASI-STATIONARY OVER THE 
PAST 18 HOURS. ESTIMATED SEA SURFACE TEMPERATURES (SSTS) ARE 26-27 
CELSIUS, BUT LOCALIZED UPWELLED WATERS MAY BE SEVERAL DEGREES COOLER. 
THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
REMNANT EYE IN THE EIR AND THE AFOREMENTIONED MICROWAVE IMAGERY. THE 
INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, BASED ON A 
BLEND OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES OUTLINED 
BELOW. ENVIRONMENTAL CONDITIONS ARE MARGINALLY UNFAVORABLE, WITH 
RAPIDLY COOLING SSTS AND LOW OCEAN HEAT CONTENT (OHC) INDUCED BY 
UPWELLING, COMBINED WITH MODERATE TO HIGH MID-LEVEL SHEAR AND DRY AIR 
INTRUSION, OFFSETTING THE STRONG POLEWARD OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: PERSISTENCE AND OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: COMPETING STEERING PATTERN. SYSTEM IS
TRAPPED IN A COL REGION BETWEEN SUBTROPICAL RIDGE (STR) CENTERS TO
THE NORTHEAST AND THE WEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.0 - 90 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.0 - 90 KTS
   CIMSS SATCON: 99 KTS AT 010530Z
   CIMSS ADT: 107 KTS AT 010530Z
   CIMSS AIDT: 96 KTS AT 010530Z
   CIMSS D-MINT: 91 KTS AT 010537Z
   CIMSS D-PRINT: 88 KTS AT 010530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: STRONG OCEANIC UPWELLING. 

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: OVER THE PAST 12 HOURS, TY 30W HAS EXECUTED A 
CYCLONIC LOOP WHILE REMAINING QUASI-STATIONARY, TRAPPED WITHIN THE 
COL REGION BETWEEN COMPETING STR CENTERS TO THE NORTHEAST AND WEST. 
THE SYSTEM IS STILL DRIFTING SLOWLY SOUTHWARD BASED ON THE MOST 
RECENT EIR IMAGERY; HOWEVER, OVER THE NEXT SEVERAL HOURS, IT WILL 
BEGIN TO TRACK WESTWARD AS THE BROADER SYNOPTIC PATTERN RETROGRADES 
WESTWARD WHILE RETAINING ITS OVERALL ORIENTATION AND RELATIVE 
POSITIONAL GEOMETRY. BETWEEN TAU 24 AND TAU 36, A TRANSIENT MID-
LATITUDE SHORTWAVE TROUGH WILL PASS TO THE NORTH AND ERODE THE 
NORTHEASTERN PERIPHERY OF THE WESTERN RIDGE, WHILE SIMULTANEOUSLY THE 
EASTERN RIDGE CONTINUES TO AMPLIFY AND EXPAND SUBTLY WESTWARD. BY TAU 
48, THE EASTERN RIDGE WILL BECOME THE DOMINANT STEERING MECHANISM, 
AND TY 30W WILL BEGIN TO ROUND THE STR AXIS AND RECURVE POLEWARD. BY 
TAU 72, TY 30W WILL ACCELERATE NORTHEASTWARD AFTER CLEARING THE RIDGE 
AXIS, EMBEDDING WITHIN THE MID-LATITUDE WESTERLIES. REGARDING 
INTENSITY, TY 30W WILL REMAIN OVER THE COLD WAKE OF UPWELLED WATERS 
AND WILL CONTINUE TO WEAKEN STEADILY OVER THE NEXT 24 HOURS, DECAYING 
TO A MINIMUM OF 70-75 KTS BY TAU 24. BY TAU 36, THE SYSTEM WILL 
EMERGE FROM THE COLD POOL OVER HIGHER-OHC WATERS, ALLOWING IT TO 
RECONSOLIDATE A STRONG CONVECTIVE CORE AND RE-INTENSIFY THROUGH TAU 
48. TY 30W WILL SUBSEQUENTLY DECELERATE AS IT REACHES THE RIDGE AXIS, 
INDUCING ADDITIONAL LOCALIZED UPWELLING. HOWEVER, SYNOPTIC 
ENVIRONMENTAL FACTORS WILL BE MORE FAVORABLE DURING THIS PERIOD, 
WHICH SHOULD PARTIALLY MITIGATE THE THERMODYNAMIC IMPACTS OF LIMITED 
UPWELLING. CONSEQUENTLY, THE FORECAST CALLS FOR THE SYSTEM TO 
MAINTAIN A STEADY INTENSITY FROM TAU 48 TO TAU 72 UNDER THESE 
COMPETING ENVIRONMENTAL INFLUENCES. FROM TAU 72 ONWARDS, TY 30W WILL 
ENCOUNTER SHARPLY DECREASING SSTS, INCREASING BAROCLINIC VWS, AND DRY 
AIR ENTRAINMENT AS IT INITIATES EXTRATROPICAL TRANSITION (ETT), 
LEADING TO STEADY TO RAPID WEAKENING THROUGH THE REMAINDER OF THE 
FORECAST PERIOD.  

MODEL DISCUSSION: NUMERICAL TRACK GUIDANCE EXHIBITS INCREASING 
SPREAD, PARTICULARLY IN ALONG-TRACK TIMING. CONSEQUENTLY, THE MULTI-
MODEL CONSENSUS MEMBERSHIP HAS BEEN MODIFIED TO EXCLUDE EXTREME 
OUTLIERS (NAVGEM, UKMET ENSEMBLE, GALWEM, AND JGSM) THAT WERE 
EXERTING AN DISPROPORTIONATE BIAS ON THE CONSENSUS MEAN. THE ADJUSTED 
CONSENSUS COMPRISES THE GFS, ECMWF, GEFS, ECEPS, AND SIX AI MODELS. 
THROUGH TAU 72, THIS ADJUSTED CONSENSUS IS IN GOOD ALONG-TRACK 
AGREEMENT AND EXHIBITS A CROSS-TRACK SPREAD OF 150 NM. HOWEVER, 
UNCERTAINTY INCREASES SUBSTANTIALLY BEYOND TAU 72, WHERE EVEN THE 
ADJUSTED CONSENSUS (CONW) DEPICTS SIGNIFICANT ALONG-TRACK DIVERGENCE, 
PRIMARILY BIFURCATED BETWEEN THE ECMWF, WHICH IS RELATIVELY SLOW TO 
RECURVE THE SYSTEM, AND THE GFS ALONG WITH THE MAJORITY OF THE AI 
MODELS, WHICH ACCELERATE THE SYSTEM RAPIDLY TO THE NORTHEAST. THE 
RESULTING ALONG-TRACK SPREAD AT TAU 120 APPROACHES 700 NM. THE JTWC 
FORECAST TRACK IS PLACED NEAR THE ADJUSTED CONSENSUS MEAN THROUGH THE 
FORECAST PERIOD. INTENSITY GUIDANCE IS IN GENERALLY GOOD AGREEMENT. 
THE COUPLED MESOSCALE MODELS ALL DEPICT SIGNIFICANTLY GREATER NEAR-
TERM WEAKENING THAN THE AI AND STATISTICAL-DYNAMICAL (SHIPS) 
GUIDANCE, WITH HAFS-A DEPICTING A MINIMUM INTENSITY OF 70 KTS AND 
HWRF AND CTCX INDICATING NEAR 75 KTS. ALL GUIDANCE INDICATES AN 
INTENSITY RECOVERY AFTER TAU 24, FOLLOWED BY A PLATEAU AFTER TAU 48 
PRIOR TO THE ONSET OF RAPID WEAKENING AFTER TAU 72. THE JTWC 
INTENSITY FORECAST IS ALIGNED WITH THE CTCX-HWRF BLEND THROUGH TAU 
72, THEN TRACKS CLOSE TO THE CONSENSUS MEAN THROUGH TAU 120. 

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