WDPN31 PGTW 270900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (DOLPHIN) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.4N 176.7E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 680 NM EAST-SOUTHEAST OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: WESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS SPIRAL
BANDS OF DEEP CONVECTION AND VORTICAL HOT TOWERS DEVELOPING ALONG
THE SOUTHWESTERN AND SOUTHERN FLANKS OF A RAPIDLY DEVELOPING LOW
LEVEL CIRCULATION CENTER (LLCC). A 270619Z SSMIS 91GHZ MICROWAVE
IMAGE REVEALED A NEARLY CLOSED RING OF MODERATE TO DEEP CONVECTION,
WHILE THE 37GHZ IMAGE DEPICTED A WEAK LOW EMISSIVITY REGION (LER)
INDICATIVE OF A NASCENT MICROWAVE EYE FEATURE. AN EARLIER 270314Z
GMI COLOR-ENHANCED 36GHZ IMAGE REVEALED A WELL-DEFINED INNER CORE
ALREADY HAVING DEVELOPED AT THAT TIME, WITH A CYAN RING COMPLETELY
ENCIRCLING THE LLCC. ANIMATED WATER VAPOR IMAGERY DEPICTS STRONG
POLEWARD OUTFLOW INTO THE BASE OF A TROPICAL UPPER-TROPOSPHERIC
TROUGH (TUTT), AS WELL AS MODERATE WESTWARD OR EQUATORWARD OUTFLOW,
PROVIDING AMPLE UPPER-LEVEL DIVERGENCE TO TS 12W. THE INITIAL 
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE LOWER-LEVEL 
LER IN THE 37GHZ MICROWAVE IMAGE DISCUSSED ABOVE. THE INITIAL 
INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON A BLEND OF THE 
AVAILABLE SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES OUTLINED 
BELOW. THE ENVIRONMENT IS AS GOOD AS IT GETS, WITH MINIMAL DEEP-LAYER 
SHEAR, VERY WARM SSTS (29-31C), HIGH OHC (100-125 KJ PER CM2) AND 
STRONG DUAL-CHANNEL OUTFLOW AND IS HIGHLY CONDUCIVE TO EXTREMELY RAPID
INTENSIFICATION (ERI).

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) COMPLEX TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.5 - 35 KTS
   PHFO: T2.5 - 35 KTS
   CIMSS SATCON: 34 KTS AT 270410Z
   CIMSS ADT: 33 KTS AT 270600Z
   CIMSS AIDT: 31 KTS AT 270600Z
   CIMSS D-MINT: 32 KTS AT 270619Z
   CIMSS D-PRINT: 34 KTS AT 270710Z

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

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: TROPICAL STORM (TS) 12W (DOLPHIN) IS MOVING
QUICKLY (16 KTS) WEST-NORTHWESTWARD ALONG THE SOUTHERN PERIPHERY
OF A COMPLEX MID-TO-UPPER-LEVEL SUBTROPICAL RIDGE (STR) POSITIONED TO 
THE NORTH. THE TRACK IS FORECAST TO FLATTEN TO A MORE WESTWARD
TRAJECTORY THROUGH TAU 24 AS A SUBTROPICAL RIDGE EXTENSION MOVES IN
FROM THE NORTHWEST. IN THE LONGER TERM, A VERY LARGE, DEEP-LAYER 
UPPER-LEVEL LOW IS FORECAST TO DEVELOP FAR TO THE NORTHEAST AND TRACK 
SOUTHWESTWARD TO A POSITION NEAR 30N 180E BY TAU 48. THIS EVOLUTION 
IN THE UPPER-LEVEL PATTERN WILL RESULT IN A GENERAL DECELERATION, 
ESPECIALLY AFTER TAU 12, AS THE STEERING GRADIENT WEAKENS. 
SIMULTANEOUSLY, A NEW STR AXIS BEGINS TO BUILD EAST OF TS 12W AND 
EXTEND TO THE SOUTH OF THE UPPER-LEVEL LOW, SEVERING IT FROM THE MAIN 
FLOW AND CONNECTING WITH A LARGE STR COMPLEX EAST OF JAPAN. THIS WILL 
PRESENT TS 12W WITH A GENERALLY NORTHWEST-SOUTHEAST ORIENTED STEERING 
RIDGE, RESULTING IN A GRADUAL TURN NORTHWESTWARD AFTER TAU 24 AND 
CONTINUING THROUGH TAU 120. REGARDING INTENSITY, AS DISCUSSED ABOVE, 
THE ENVIRONMENT IS OPTIMAL FOR RI OR ERI. VWS IS FORECAST TO REMAIN
LOW, WHILE SSTS AND OHC INCREASE ALONG THE FORECAST TRACK. IN THE 
UPPER-LEVELS, THE SYSTEM MAINTAINS ITS COUPLING TO AN ANOMALOUSLY 
STRONG SUBTROPICAL JET AXIS THAT DEVELOPS ON THE SOUTHERN SIDE OF THE 
LARGE UPPER-LEVEL LOW, AT LEAST THROUGH TAU 60, WHICH WILL SUPPORT 
RAPID DEVELOPMENT. AFTER TAU 60, THE SYSTEM WILL BE SUFFICIENTLY 
STRUCTURED TO MAINTAIN SELF-SUSTAINED RADIAL OUTFLOW ALOFT. IN FACT, 
SOME MODEL GUIDANCE SUGGESTS THE SYSTEM MAY TRANSITION INTO AN 
ANNULAR STRUCTURE IN THE LONG-TERM, WHICH WILL BE MONITORED CLOSELY. 
THE FORECAST CALLS FOR THE SYSTEM TO COMMENCE RI BY TAU 24, AND REACH 
SUPER TYPHOON STRENGTH WITHIN 72 HOURS. THE SYSTEM WILL LIKELY 
MAINTAIN INTENSITY AFTER TAU 72, BUT THE ONSET OF EYEWALL REPLACEMENT 
CYCLES (ERCS) AND THE POTENTIAL FOR ANNULAR DEVELOPMENT PRECLUDE A 
DEFINITIVE FORECAST AT THIS TIME, MAKING SIGNIFICANT INTENSITY 
FLUCTUATIONS LIKELY AFTER TAU 72.  

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH
TAU 72, WITH CROSS-TRACK SPREAD GRADUALLY INCREASING TO 110NM AT
TAU 72. THE ECENS AND GEFS ENSEMBLE MEANS ARE BOTH POSITIONED ON
THE NORTHERN EDGE OF THE GUIDANCE ENVELOPE WHILE GALWEM AND EC-AIFS
ARE ON THE SOUTHERN EDGE THROUGH TAU 72. THE JTWC FORECAST IS PLACED 
NEAR THE EXPERIMENTAL AI (FNV3) AND THE ECMWF TRACKERS, ALONG THE 
NORTHERN EDGE OF THE INNER GROUPING OF MODELS, THROUGH TAU 72 WITH 
HIGH CONFIDENCE. BEYOND TAU 72, THE MODELS BEGIN TO QUICKLY DIVERGE. 
NAVGEM IN PARTICULAR IS A SIGNIFICANT OUTLIER, TAKING THE SYSTEM 
NEARLY NORTHWARD INTO THE RIDGE, A HIGHLY UNLIKELY SCENARIO. THE GFS 
AND JGSM ON THE OTHER HAND PULL THE SYSTEM TO A MORE WESTWARD TRACK, 
INCREASING THE CROSS-TRACK SPREAD TO 380NM BY TAU 120. DISCOUNTING 
NAVGEM HOWEVER, THE ENVELOPE IS A MORE MODEST 230NM WIDE. ENSEMBLE 
GUIDANCE ALSO DEPICTS RAPIDLY INCREASING UNCERTAINTY AFTER TAU 72, 
WITH THE EXPERIMENTAL JTWC SUPER-ENSEMBLE SHOWING A ROUGHLY 50-50 
SPLIT IN MEMBERS TRACKING THE SYSTEM NORTHWESTWARD AND THOSE TRACKING 
IT MORE WESTWARD. THE JTWC FORECAST REMAINS POSITIONED CLOSE TO THE 
AI AND ECMWF DETERMINISTIC TRACKER THROUGH TAU 120, BUT CONFIDENCE IS 
REDUCED DUE TO INCREASED ENSEMBLE DIVERGENCE. INTENSITY GUIDANCE IS 
IN FAIRLY GOOD AGREEMENT, WITH THE MAJORITY OF THE MODELS SUPPORTING 
RI OR ERI, THOUGH WITH A SPREAD IN PEAK INTENSITY VALUES BETWEEN 125 
KTS (COAMPS-TC AND FGNI) AND 155 KTS (HAFS-A) WITH HWRF IN BETWEEN 
THE TWO. MOST OF THE GUIDANCE REACHES PEAK INTENSITY AROUND TAU 72, 
THEN FLATTENS OFF THROUGH TAU 120. DUE TO ISSUES WITH THE SHIPS SST 
VALUES, NORMALLY AVAILABLE RI GUIDANCE IS NOT PRESENT, THOUGH THE 
INDEPENDENT COAMPS-TC ENSEMBLE RI MODEL (CTR1) IS SHOWING ERI UP TO A 
PEAK APPROACHING 160 KTS BY TAU 84. THE JTWC FORECAST IS PLACED 
AMONGST THE MORE AGGRESSIVE MESOSCALE MODELS AND GENERALLY CLOSE TO 
THE HAFS-A THROUGH THE FORECAST PERIOD. CONFIDENCE IS MEDIUM IN THE 
LONG-TERM DUE TO UNCERTAINTIES REGARDING POTENTIAL ERCS AND ANNULAR 
TRANSITION.  

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