Advisories

WDPN31 PGTW 311500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 033//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.8N 143.5E
   INITIAL INTENSITY: 110 KTS
   GEOGRAPHIC REFERENCE: 170 NM SOUTHEAST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 46 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 
CONTRACTING EYE, NOW MEASURED AT 31 NM, CHARACTERIZED BY COOLING EYE 
TEMPERATURES (15C) AND WARMING CLOUD-TOP TEMPERATURES WITHIN THE 
CENTRAL DENSE OVERCAST (CDO). A SERIES OF MICROWAVE IMAGES, 
CULMINATING WITH A 310926Z SSMIS 91 GHZ PASS, INDICATES THE RAPID 
PROGRESSION OF AN EYEWALL REPLACEMENT CYCLE (ERC), WHICH IS NEARLY 
COMPLETED. THE CIMSS M-PERC HOVMOLLER DIAGRAM CLEARLY REVEALS A WEAK 
REMNANT INNER EYEWALL CONSOLIDATING WITH THE SECONDARY EYEWALL AS OF 
THE 0926Z SSMIS PASS. THIS EVOLUTION IS ALSO EVIDENT IN THE ANIMATED 
EIR IMAGERY, AS THE DECAYING INNER EYEWALL DETACHES FROM THE 
SECONDARY EYEWALL RING AND STRUCTURALLY DEGRADES, CREATING A WELL-
DEFINED MOAT FEATURE, PARTICULARLY IN THE SOUTHWESTERN QUADRANT. AT 
THE SYNOPTIC SCALE, THE FRONTAL BOUNDARY TO THE NORTHWEST IS RAPIDLY 
DISSIPATING AND FRAGMENTING AS IT PROPAGATES SOUTHEASTWARD, AND IS 
CURRENTLY LOCATED APPROXIMATELY 300 NM NORTHWEST OF TYPHOON (TY) 30W. 
UPPER-LEVEL ANALYSIS REVEALS A MESOSCALE POINT-SOURCE DIRECTLY OVER 
30W PROVIDING SYMMETRIC RADIAL OUTFLOW ALOFT, WHILE A ROBUST 200 MB 
ANTICYCLONE IS POSITIONED TO THE EAST, SUPPORTING ENHANCED POLEWARD 
OUTFLOW. THE MICROWAVE SUITE ALSO REVEALS THAT TY 30W IS 
THERMODYNAMICALLY ISOLATED WITHIN A NARROW CORRIDOR OF DEEP 
TROPOSPHERIC MOISTURE, PERIPHERALLY ENCIRCLED BY A DRY, SUBSIDING AIR 
MASS, ESPECIALLY TO THE NORTHWEST AND SOUTH. THE INITIAL POSITION IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE EYE IN THE EIR IMAGERY. 
THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE 
CONGRUENCE OF THE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES 
OUTLINED BELOW. ENVIRONMENTAL CONDITIONS ARE MARGINAL, PRIMARILY DUE 
TO STRUCTURAL DISRUPTIONS FROM THE ERC AND THE INCEPTION OF 
SIGNIFICANT SELF-INDUCED OCEANIC UPWELLING, WHICH WILL TEMPER 
OTHERWISE FAVORABLE CONDITIONS OF LOW DEEP-LAYER VERTICAL WIND SHEAR 
(VWS) AND ROBUST POLEWARD OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK, BIFURCATED STEERING PATTERN, WITH 
SUBTROPICAL RIDGING (STR) LOCATED BOTH TO THE NORTHEAST AND TO THE 
WEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T6.0 - 115 KTS
   RCTP: T5.5 - 102 KTS
   CIMSS SATCON: 113 KTS AT 311030Z
   CIMSS ADT: 109 KTS AT 311130Z
   CIMSS AIDT: 110 KTS AT 311130Z
   CIMSS D-MINT: 109 KTS AT 311116Z
   CIMSS D-PRINT: 107 KTS AT 311130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 5-10 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: EYEWALL REPLACEMENT CYCLE (ERC) AND OCEANIC
UPWELLING. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 ITS EAST-
NORTHEASTWARD TURN OVER THE PAST SIX HOURS AS THE STR TO THE EAST 
SHIFTS SUBTLY SOUTHWARD AND ITS NORTHWESTERN BOUNDARY ERODES IN 
RESPONSE TO A MID-LATITUDE SHORTWAVE TROUGH PASSING TO THE NORTH. THE 
MOST RECENT FRAMES OF EIR IMAGERY, HOWEVER, SUGGEST THE SYSTEM IS 
EXHIBITING MINOR TROCHOIDAL WOBBLING AS THE ERC CONCLUDES. ONCE THE 
TROUGH PASSES TO THE NORTH IN THE NEXT 6-12 HOURS, THE STR TO THE 
WEST WILL STRENGTHEN AND BUILD EASTWARD, WHILE THE RIDGE TO THE EAST 
WEAKENS AND SHIFTS SOUTHWARD. BY TAU 12, THE ENTIRE SYNOPTIC-SCALE 
RIDGE PATTERN BEGINS TO SHIFT WESTWARD, WITH THE TWO PRIMARY RIDGING 
CENTERS TRANSLATING ABOUT 10 DEGREES LONGITUDE TO THE WEST WHILE 
MAINTAINING THEIR OVERALL RELATIONSHIP WITH ONE ANOTHER. TY 30W WILL 
REACH AN INFLECTION POINT BY TAU 12, AT ROUGHLY 144E, WHEREUPON IT 
WILL RAPIDLY SHIFT DIRECTION BACK TOWARD THE WEST-SOUTHWEST, MOVING 
WITHIN THE SHIFTING SYNOPTIC PATTERN. BEYOND TAU 36, A SERIES OF 
SHORTWAVE TROUGHS WILL PASS TO THE NORTH, PROGRESSIVELY ERODING THE 
NORTHEASTERN PORTION OF THE STR OVER TAIWAN, ALLOWING TY 30W TO 
GRADUALLY TURN NORTHWESTWARD THROUGH TAU 60. AFTER TAU 60, THE STR 
SHIFTS SHARPLY WESTWARD INTO CHINA, WHILE THE RIDGE OVER THE CENTRAL 
PACIFIC BUILDS AND BECOMES THE DOMINANT STEERING INFLUENCE ON TY 30W. 
AT TAU 72, THE SYSTEM BEGINS TO RECURVE AROUND THE RIDGE AXIS, 
ASSISTED IN ITS NORTHWARD TRAJECTORY BY THE APPROACH OF A COLD 
FRONTAL BOUNDARY MOVING SOUTHEASTWARD FROM JAPAN. REGARDING 
INTENSITY, TY 30W IS FORECAST TO STEADILY WEAKEN OVER THE NEXT 36 
HOURS, PRIMARILY DUE TO THE ONSET OF SIGNIFICANT LOCALIZED UPWELLING 
AS ITS TRANSLATIONAL SPEED REDUCES. BY TAU 48, AS THE SYSTEM 
TRANSLATES AWAY FROM THE SELF-INDUCED COLD POOL, IT WILL RE-INTENSIFY 
SLIGHTLY. BY TAU 96, TY 30W WILL BEGIN TO WEAKEN ONCE MORE AS IT 
TRAVERSES COOLER SEA SURFACE TEMPERATURES (SSTS) AND EXPERIENCES 
SHARPLY DEGRADED DYNAMICS FROM STRENGTHENING SHEAR AND DRY AIR 
ENTRAINMENT.  

MODEL DISCUSSION: TRACK GUIDANCE REMAINS IN GOOD OVERALL AGREEMENT ON 
THE SYNOPTIC SCENARIO; HOWEVER, BOTH CROSS- AND ALONG-TRACK 
UNCERTAINTY HAVE INCREASED SINCE THE LAST DETERMINISTIC RUN. ALL 
MEMBERS OF THE GUIDANCE PACKAGE AGREE ON SOME ADDITIONAL 
NORTHEASTWARD MOVEMENT BEFORE THE SYSTEM BECOMES QUASI-STATIONARY, 
PRIOR TO SHIFTING SHARPLY WEST-SOUTHWESTWARD AFTER TAU 12. THROUGH 
TAU 72, THE BULK OF THE GUIDANCE (WITH THE EXCEPTION OF NAVGEM, 
GALWEM, AND EGRR) IS TIGHTLY CLUSTERED IN AN 80 NM WIDE ENVELOPE. THE 
PREVIOUSLY MENTIONED MODELS LIE TO THE SOUTHWEST, APPROXIMATELY 75 NM 
BEYOND THE MOST WESTERN OF THE CLUSTERED MODELS, WHICH IS THE 
CONSENSUS MEAN, PULLING THE CONW TOO FAR SOUTHWESTWARD. ON THE 
EASTERN SIDE OF THE ENVELOPE RESIDE THE ECEPS, THE AI-CONSENSUS, AND 
THE AIFS TRACKERS. BY TAU 120, THE OVERALL ORIENTATION OF THE 
GUIDANCE PACKAGE REMAINS THE SAME, WITH THE NAVGEM, GALWEM, AND EGRR 
PUSHING FAR OUT TO THE WEST BEFORE TURNING POLEWARD, WHILE THE AICN, 
AIFS, AND ECEPS TURN THE SYSTEM FASTER AND REMAIN ON THE INSIDE EDGE. 
DISCOUNTING THE THREE WESTWARD OUTLIERS, CROSS-TRACK SPREAD REMAINS 
RELATIVELY CONSTRAINED AT 115 NM BY TAU 120. ALONG-TRACK SPREAD, 
HOWEVER (EVEN WHEN OMITTING THE THREE OUTLIERS), INCREASES SHARPLY TO 
NEARLY 400 NM BETWEEN THE SLOW ECMWF AND THE PROGRESSIVE AIFS, GFS, 
AND AICN. THE JTWC FORECAST IS POSITIONED BETWEEN THE ECMWF AND AICN 
THROUGH TAU 72, THEN NEAR A CLUSTER OF AI MODELS, THOUGH 
CONSERVATIVELY SHORT OF THE AGGRESSIVELY FAST AICN, THROUGH TAU 120. 
INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT THE SYSTEM WILL WEAKEN 
SIGNIFICANTLY THROUGH TAU 36, THEN LEVEL OFF AND RE-INTENSIFY THROUGH 
TAU 72 BEFORE MORE SIGNIFICANT WEAKENING OCCURS BEYOND TAU 72. THE 
JTWC FORECAST IS PLACED NEAR THE HWRF SOLUTION THROUGH 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//
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