WDPN32 PGTW 271500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 06W (SIX) WARNING NR 
002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.6N 137.9E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 186 NM NORTH OF YAP
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL DEPRESSION (TD) 06W (SIX) REMAINS VERY BROAD, AND
CONTINUES TO SLOWLY CONSOLIDATE. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY DEPICTS FLARING DISORGANIZED CONVECTION SCATTERED
AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC), HAVING YET TO
CONSOLIDATE INTO A COHERENT MASS. A 271147Z ASCAT-B SCATTEROMETER
PASS SHOWED AN ELONGATED, WEAK LLCC WITH A RADIUS OF MAXIMUM WINDS
(RMW) OF ABOUT 80NM, INDICATING LITTLE IN THE WAY OF CONSOLIDATION
SINCE THE PREVIOUS SCATTEROMETER PASS 12 HOURS AGO. BOTH THE
SCATTEROMETER AND A 270844Z SMOS PASS SHOWED MAXIMUM WINDS IN THE
25-30 KNOT RANGE ACROSS THE SOUTHERN HEMISPHERE OF THE STORM, WHILE
WINDS ON THE NORTHERN SIDE WERE SLIGHTLY LOWER AT 20-25 KNOTS. THE
ASCAT-B PASS PROVIDED HIGH CONFIDENCE IN BOTH THE INITIAL POSITION
AND INTENSITY, AND WAS SUPPORTED BY T1.5 DVORAK INTENSITY
ESTIMATES FROM BOTH PGTW AND RJTD, THOUGH ADT AND AIDT ESTIMATES
ARE SLIGHTLY HIGHER AT T2.0. THE ENVIRONMENT REMAINS MARGINALLY
FAVORABLE, WITH MODERATE TO STRONG EQUATORWARD OUTFLOW OFFSET BY
10-15 KNOTS OF SHEAR PRESSING DOWN FROM THE NORTH FROM THE OUTFLOW
ASSOCIATED WITH TY 05W. SSTS ARE FAVORABLE AT 29-30C. SHEAR HAS
PICKED UP A NOTCH OVER THE PAST SIX HOURS BUT REMAINS LOW, AS THE
SYSTEM LIES UNDER AN UPPER-LEVEL COL REGION AS THE UPPER-LEVEL FLOW
SPLITS, WITH SOME TURNING SHARPLY SOUTHWEST OVER TD 06W AND THE
REMAINDER HEADING NORTHEAST INTO A DEVELOPING TUTT-CELL OVER THE
NORTHERN MARIANAS.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF THE LOW TO
MID-LEVEL SUBTROPICAL RIDGE (STR) TO THE NORTH.  

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   CIMSS ADT: 28 KTS AT 271130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

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

FORECAST DISCUSSION: THROUGH THE NEXT 12 TO 18 HOURS, TD 06W IS
FORECAST TO TRACK GENERALLY WEST ALONG THE SOUTHERN SIDE OF THE LOW
TO MID-LEVEL STR TO THE NORTH. AS THE SYSTEM INTENSIFIES, THE
STEERING LEVEL WILL INCREASE IN HEIGHT SUCH THAT BY TAU 24 THE
STEERING INFLUENCE SHIFTS TO THE DEEP-LAYER NEAR EQUATORIAL RIDGE
(NER) CENTERED EAST OF GUAM, WHICH WILL PUSH TD 06W ONTO A MORE
POLEWARD TRACK AFTER TAU 24. THE SYSTEM WILL ACCELERATE ON A
NORTH-NORTHWESTWARD TRACK AFTER TAU 36 AS THE NER PUSHES WEST AND
TIGHTENS THE STEERING GRADIENT. BY TAU 72, THE NER WEAKENS AND
SHIFTS SOUTHWESTWARD, WHILE THE STRONG STR CENTERED NEAR TOKYO
BUILDS TOWARDS THE WEST, MORPHING INTO AN EAST-WEST ORIENTED RIDGE
COMPLEX EXTENDING FROM JAPAN, ACROSS THE KOREAN PENINSULA AND INTO
EASTERN CHINA. THIS RIDGE COMPLEX WILL SERVE TO FORCE TD 06W ONTO A
MORE WEST-NORTHWEST TRACK IN THE LATER PORTIONS OF THE FORECAST
AFTER TAU 72. THE RECENT SCATTEROMETER DATA CONFIRMS THAT TD 06W IS
ONLY VERY SLOWLY CONSOLIDATING, AND THUS THERE IS NO CHANGE TO THE
FORECAST CALLING FOR THE SYSTEM TO REMAIN RELATIVELY BROAD AND WEAK
FOR THE FIRST 24 TO 36 HOURS OF THE FORECAST. BY TAU 36, THE RADIUS
OF MAXIMUM WINDS (RMW) IS EXPECTED TO HAVE REDUCED SIGNIFICANTLY,
WHICH WILL PREP THE STAGE FOR FUTURE RAPID INTENSIFICATION (RI).
THE TUTT-CELL MENTIONED ABOVE, CURRENTLY OVER THE NORTHERN MARIANAS
IS FORECAST TO MOVE WEST-NORTHWEST OVER THE NEXT DAY OR SO,
ULTIMATELY MERGING WITH AND ELONGATED TUTT ALREADY SITTING SOUTH OF
HONSHU. BY TAU 48 THIS TUTT-CELL WILL SLIDE TO THE WEST INTO A
FAVORABLE POSITION IN RELATION TO TD 06W, AND THE DRAMATIC INCREASE
OF OUTFLOW INTO THE TUTT WILL SUPPORT RI BETWEEN TAU 48 AND 96. BY
TAU 96 THE UPPER-LEVEL PATTERN WILL SHIFT ONCE AGAIN, WITH AN
ANTICYCLONE BUILDING ALOFT OVER KYUSHU, DUE NORTH OF THE SYSTEM,
WHICH WILL INDUCE EASTERLY SHEAR INTO THE EQUATION AND LIKELY LIMIT
FURTHER INTENSIFICATION AFTER TAU 96. JUST HOW STRONG THE SYSTEM
CAN GET PRIOR TO TAU 96 WILL DETERMINE THE ULTIMATE IMPACT OF THE
EASTERLY SHEAR, AND FURTHER INTENSIFICATION IS POSSIBLE IN THE EAST
CHINA SEA BEYOND TAU 120. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE REMAINS IN VERY GOOD
AGREEMENT THROUGH THE BULK OF THE FORECAST. THE GFS IS A NOTABLE
OUTLIER THROUGH TAU 12, TAKING THE SYSTEM TO THE SOUTHWEST, BUT
LIKELY THE GFS IS JUMPING TO A SEPARATE VORTEX WITHIN THE BROAD LLC
DURING THE EARLY PHASE OF THE FORECAST. THE REMAINDER OF THE
GUIDANCE REMAINS TIGHTLY CONSTRAINED IN AN ENVELOPE THAT GRADUALLY
EXPANDS TO 105NM AT TAU 72, WITH THE BULK OF THAT SPREAD INCURRED
BY THE JGSM WHICH LIES WELL EAST OF THE REMAINDER OF THE CONSENSUS
FROM TAU 00 TO TAU 72. THE ENVELOPE GRADUALLY EXPANDS TO ABOUT
140NM BY TAU 120. THE SUPER-ENSEMBLE MEAN, CONSISTING OF THE ECENS,
GEFS, MOGREPS AND CMC ENSEMBLE MEANS LIES VERY NEAR THE
DETERMINISTIC CONSENSUS MEAN AS WELL, WITH THE GEFS BEING THE
NORTHERN SIDE OUTLIER. THE JTWC TRACK FORECAST LIES WEST OF THE
MEAN THROUGH TAU 48, THEN CLOSELY TRACKS BOTH THE DETERMINISTIC AND
ENSEMBLE MEANS WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS STILL
INTENSIFYING THE SYSTEM TOO QUICKLY, AND THE JTWC FORECAST IS BELOW
THE CONSENSUS MEAN THROUGH TAU 48, THEN QUICKLY SHIFTS
SIGNIFICANTLY HIGHER THAN THE MEAN THROUGH THE REMAINDER OF THE
FORECAST, WITH THE PEAK 35 KNOTS ABOVE THE MEAN, BUT IN LINE WITH
THE HWRF AND CTR4 SOLUTIONS. THE LATEST COAMPS-TC ENSEMBLE RI
PROBABILITIES ARE CONSISTENT WITH THE EARLIER RUN, SHOWING 60
PERCENT LIKELIHOOD OF RI BETWEEN TAU 48 AND TAU 96, LENDING
INCREASED CONFIDENCE IN THIS SCENARIO. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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