Advisories

WDPN31 PGTW 271500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 30W (IN-FA) WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.5N 161.6E
   INITIAL INTENSITY: 105 KTS
   GEOGRAPHIC REFERENCE: 407 NM SOUTHWEST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A COMPACT 
SYSTEM WITH A SMALL, RELATIVELY CLOUD-FREE EYE AND DEEP CONVECTION 
RE-ESTABLISHING ALONG THE INNER EYEWALL. A 271311Z GMI 37 GHZ 
MICROWAVE IMAGE REVEALED A 12-NM WIDE MICROWAVE EYE FEATURE, WHICH IS 
ROUGHLY CONGRUENT WITH THE EIR-BASED EYE DIAMETER, WHILE AT 89 GHZ, 
THE OUTER EYE WAS MEASURED BY ARCHER AT APPROXIMATELY 48 NM. EARLIER 
MICROWAVE IMAGERY DEPICTED AN ERODING INNER EYEWALL AND A ROBUST 
SECONDARY EYEWALL, WHEREAS ALL VESTIGES OF THE ORIGINAL INNER EYEWALL 
HAVE NOW DISSIPATED IN THE GMI IMAGERY. THE CIMSS M-PERC PROBABILITY 
OF AN ACTIVE EYEWALL REPLACEMENT CYCLE (ERC) IS NOW NEARLY ZERO AS 
THIS CYCLE HAS EFFECTIVELY CONCLUDED, AND THE EYE IS CONTRACTING 
AGAIN IN EIR IMAGERY. IN THE UPPER LEVELS, ANIMATED WATER VAPOR 
IMAGERY DEPICTS THE EQUATORWARD EXTENT OF A 200 MB TROUGH JUST NORTH 
OF TY 30W, WITH OUTFLOW SPLITTING ALONG AN INFLECTION POINT DUE NORTH 
OF THE SYSTEM. OVERALL, OUTFLOW IS SOMEWHAT RESTRICTED AND CONFINED 
TO THE MESOSCALE ANTICYCLONE ALOFT OVER TY 30W. THE INITIAL POSITION 
IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE EYE IN EIR IMAGERY AND 
EXTRAPOLATION FROM THE ARCHER MICROWAVE CENTER FIX ON THE GMI. THE 
SYSTEM IS MOVING SLOWLY WESTWARD, STILL EMBEDDED IN A WEAK STEERING 
ENVIRONMENT. THE INITIAL INTENSITY REMAINS SET AT 105 KTS, ASSESSED 
WITH MEDIUM CONFIDENCE USING A BLEND OF SUBJECTIVE AND OBJECTIVE 
INTENSITY ESTIMATES OUTLINED BELOW. ENVIRONMENTAL CONDITIONS REMAIN 
FAVORABLE, CHARACTERIZED BY LOW DEEP-LAYER VERTICAL WIND SHEAR (VWS), 
WARM SEA SURFACE TEMPERATURES (SSTS), HIGH OCEANIC HEAT CONTENT 
(OHC), AND MODERATE RADIAL OUTFLOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMPETING STEERING PATTERN, WITH A
NEAR-EQUATORIAL RIDGE (NER) TO THE SOUTHEAST AND A SUBTROPICAL
RIDGE (STR) TO THE NORTHWEST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.0 - 115 KTS
   RJTD: T5.5 - 102 KTS
   RCTP: T5.5 - 102 KTS
   PHFO: T6.0 - 115 KTS
   CIMSS ADT: 109 KTS AT 271130Z
   CIMSS AIDT: 100 KTS AT 271130Z
   CIMSS D-MINT: 99 KTS AT 271117Z
   CIMSS D-PRINT: 111 KTS AT 271310Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE RADIAL

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TYPHOON (TY) 30W HAS MOVED WESTWARD AT A VERY 
SLOW PACE OVER THE PAST SIX HOURS, STILL EMBEDDED IN A COMPETING 
STEERING PATTERN BETWEEN THE NER TO THE SOUTHEAST AND THE STR TO THE 
NORTHWEST. OVER THE NEXT 12 TO 24 HOURS, THE NER IS FORECAST TO 
WEAKEN AND DISSIPATE, ULTIMATELY MERGING WITH THE STR AS IT EXPANDS 
EAST AND STRENGTHENS. TY 30W WILL GRADUALLY ACCELERATE WEST-
NORTHWESTWARD ALONG THE SOUTHERN FLANK OF THE DOMINANT STR THROUGH 
TAU 72. AFTER TAU 72, THE PASSAGE OF A STRONG MID-LATITUDE TROUGH 
MOVING EAST OF JAPAN WILL INDUCE A WEAKNESS IN THE STR, AND TY 30W 
WILL BEGIN TO DECELERATE AS IT APPROACHES THIS BREAK. BY TAU 96, TY 
30W WILL ENTER THE COL REGION ASSOCIATED WITH THE BREAK IN THE RIDGE 
PATTERN AND DECELERATE RAPIDLY, BECOMING QUASI-STATIONARY. BY TAU 
120, THE SYSTEM WILL BE POSITIONED CENTRALLY WITHIN THE COL REGION, 
WITH SIGNIFICANT UNCERTAINTY AS TO ITS PROJECTED MOTION, WHICH IS 
CONTINGENT UPON THE TIMING AND POSITIONING OF COL REGION GENESIS. 
REGARDING INTENSITY, THE RECENT ERC HAS COMPLETED, AND THE EYE IS 
ALREADY CLEARING OUT. TY 30W IS FORECAST TO INTENSIFY OVER THE NEXT 
24 TO 36 HOURS; HOWEVER, INTENSIFICATION WILL BE TEMPERED BY 
RESTRICTED UPPER-LEVEL OUTFLOW, WITH NO DISTINCT POLEWARD OUTFLOW 
CHANNEL DEVELOPING, AS WELL AS OCCASIONAL INFLUXES OF ELEVATED MID-
LEVEL SHEAR AND TRANSIENT DRY AIR INTRUSIONS. THE SYSTEM IS FORECAST 
TO REACH A PEAK INTENSITY OF 120 KTS BY TAU 36, AT WHICH POINT 
MULTIPLE MESOSCALE MODELS ANTICIPATE THE ONSET OF ANOTHER ERC. AFTER 
TAU 60, THE SYSTEM WILL GRADUALLY WEAKEN DUE TO ENHANCED SHEAR BEFORE 
LEVELING OFF BY THE END OF THE FORECAST AS IT TAPS INTO A POLEWARD 
OUTFLOW CHANNEL.

MODEL DISCUSSION: TRACK GUIDANCE IS IN STRONG AGREEMENT THROUGH THE
SHORT-TERM FORECAST, WITH CROSS-TRACK SPREAD INCREASING TO JUST
65 NM BY TAU 72. BEYOND TAU 72, GUIDANCE QUICKLY DIVERGES AS THE
SYSTEM ENTERS THE COL REGION, WITH CROSS-TRACK SPREAD INCREASING TO
310 NM BY TAU 120. AFTER TAU 96, NAVGEM AND THE EC-AIFS ENSEMBLE
DIVERGE TO THE NORTHEAST, WHILE THE EXPERIMENTAL GOOGLE DEEPMIND
(GDM) AND WINDBORNE MODELS DEPICT THE SYSTEM TRACKING SLOWLY
NORTHWESTWARD. THE REMAINDER OF THE GUIDANCE SHOWS THE SYSTEM MAKING 
A SHARP WEST- OR SOUTHWESTWARD TURN AFTER TAU 96, WITH ECMWF MAKING 
THE SHARPEST TURN, AND THE AI CONSENSUS (AICN) AND OPERATIONAL GDM 
DEPICTING THE SHALLOWEST WESTWARD TURN. ENSEMBLE GUIDANCE DEPICTS A
LARGE AMOUNT OF MEMBER DISPERSION AND SIGNIFICANT UNCERTAINTY AFTER 
TAU 96. THE JTWC TRACK FORECAST IS POSITIONED ALONG THE SOUTHERN 
SIDE OF THE TRACK ENVELOPE, NEAR GDM, THROUGH TAU 72. BEYOND TAU 72, 
THE JTWC FORECAST IS PLACED NEAR THE AICN MEAN. INTENSITY GUIDANCE AS 
A WHOLE HAS TRENDED DOWNWARD OVER THE PAST TWO MODEL CYCLES. IN THIS 
RUN, GDM IS THE MOST AGGRESSIVE MODEL, DEPICTING A PEAK INTENSITY OF 
JUST UNDER 125 KTS, WHILE MESOSCALE HAFS-A, HWRF, AND CTCX, AS WELL 
AS THE CONSENSUS MEAN, ARE ALL IN AGREEMENT WITH GDM ON THE OVERALL 
SHAPE OF THE INTENSITY CURVE BUT POSITIONED ABOUT 10-15 KTS LOWER. 
THE JTWC INTENSITY FORECAST IS PLACED NEAR GDM THROUGH THE FORECAST 
PERIOD. 

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