WDPN31 PGTW 150900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN) 
WARNING NR 020//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.7N 154.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 576 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 21 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A VERY
DISORGANIZED AND BROAD CIRCULATION, LACKING IN DEEP CONVECTION,
WITH NO CLEAR CUT LOW LEVEL CIRCULATION CENTER (LLCC). THERE IS A
SMALL AREA OF FLARING DEEP CONVECTION DISPLACED WELL TO THE
SOUTHEAST OF THE REMAINDER OF THE BROAD CIRCULATION. A 150609Z
SSMIS 91 GHZ MICROWAVE IMAGE HELPED TO REFINE THE INITIAL POSITION,
THOUGH WITH ONLY LOW CONFIDENCE DUE TO THE BROAD NATURE OF THE
CIRCULATION AND LACK OF A DISTINCT CENTER OF ROTATION. THE INITIAL
INTENSITY IS ASSESSED AT A GENEROUS 30 KNOTS WITH LOW CONFIDENCE
BASED ON MULTI-AGENCY CURRENT INTENSITY ESTIMATES. WHILE AUTOMATED
VERTICAL WIND SHEAR VALUES (VWS) REMAIN LOW, ANALYSIS OF ANIMATED
UPPER-LEVEL WATER VAPOR IMAGERY SUGGESTS THE PRESENCE OF MODERATE
EASTERLY FLOW AND CONVERGENCE AT THE BASE OF A NORTH-SOUTH
UPPER-LEVEL RIDGE, WHICH IS APPLYING SOME PRESSURE ON THE EASTERN
SIDE OF THE SYSTEM. WATER VAPOR IMAGERY AND MODEL DERIVED
CROSS-SECTIONS ALSO DEPICT THE PRESENCE OF MID-LEVEL DRY AIR ON THE
EAST SIDE. THE TUTT CELL REMAINS ENTRENCHED ABOUT 900 NM TO THE
NORTHWEST, PROVIDING SOME ENHANCED POLEWARD OUTFLOW, BUT NOT ENOUGH
TO OFFSET THE UPPER-LEVEL CONVERGENCE AND DRY AIR IMPINGING ON THE
SYSTEM FROM THE EAST.

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

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   CIMSS ADT: 37 KTS AT 150540Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: LOW
   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: TD 16W HAS MOVED SLIGHTLY NORTH OF DUE WEST
OVER THE PAST TWELVE HOURS, BUT THE UNCERTAINTY IN THE INITIAL
POSITION LENDS HIGH UNCERTAINTY IN THE EXACT TRACK AND THE
INCREASED FORWARD SPEED OBSERVED OVER THE PREVIOUS TWELVE HOURS.
THE SYSTEM IS EXPECTED TO RESUME A MORE WESTWARD TRACK AS IT
PROPAGATES ALONG THE SOUTHERN PERIPHERY OF THE STR TO THE NORTH AND
IS STILL EXPECTED TO PASS VERY CLOSE TO THE ISLAND OF GUAM AROUND
TAU 36. AFTER PASSING GUAM, THE STEERING RIDGE TO THE NORTH IS
FORECAST TO MOVE WEST AND REORIENT, ALLOWING FOR A TURN TO THE
NORTHWEST THROUGH THE REMAINDER OF THE FORECAST. OVER THE NEXT 24
HOURS, PERSISTENT EASTERLY FLOW ALOFT AND THE PRESENCE OF
RELATIVELY DRY AIR IN THE MID-LEVELS WILL RETARD DEVELOPMENT, WITH
THE SYSTEM EXPECTED TO WEAKEN TO 25 KNOTS DURING THIS TIMEFRAME. BY
TAU 36 THE SYSTEM IS FORECAST TO MOVE INTO AN AREA OF LOWER
EASTERLY SHEAR WITH INCREASING MID-LEVEL MOISTURE, MARKING THE
BEGINNING OF A PERIOD OF INTENSIFICATION THAT PEAKS AT 75 KNOTS BY
TAU 120.  

MODEL DISCUSSION: TRACK GUIDANCE IS IN GOOD AGREEMENT, PARTICULARLY
IN THE EXTENDED FORECAST PERIOD. IN THE NEAR-TERM HOWEVER, MODELS
SHOW MUCH MORE SPREAD THAN IN PREVIOUS RUNS, WITH NAVGEM, COAMPS-TC
AND HWRF NOW INDICATING A TRACK FURTHER SOUTH WHILE THE REMAINDER
OF THE CONSENSUS MEMBERS REMAIN CLOSELY CLUSTERED AROUND A TRACK
OVER THE ISLAND OF GUAM. TRACK SPREAD PEAKS AT 95 NM AT TAU 36,
DECREASING TO 75 NM AT TAU 48. THE BROAD NATURE OF THE LLC AND
UNCERTAINTY SURROUNDING THE EXACT CENTER COULD LEAD TO ADJUSTMENTS
IN THE TRACK AND CLOSEST POINT OF APPROACH (CPA) TIMING OVER THE
NEXT TWO DAYS. IN LIGHT OF THE UNCERTAINTY IN THE NEAR-TERM MOTION
AND BEST TRACK POSITION, THERE IS MEDIUM CONFIDENCE IN THE JTWC
FORECAST TRACK. INTENSITY GUIDANCE HAS COME INTO BETTER AGREEMENT
ON THE OVERALL SCENARIO, WITH THE MAJORITY OF THE GUIDANCE
INDICATING LITTLE TO NO INTENSIFICATION THROUGH TAU 24. HOWEVER IN
LIGHT OF THE ASSESSMENT OF THE CURRENT AND FORECAST ENVIRONMENT,
THE JTWC FORECAST DIVERGES LOWER THAN ALL GUIDANCE THROUGH TAU 24,
THEN CLOSELY TRACKS THE SHIPS-GFS INTENSIFICATION TREND THROUGH THE
REMAINDER OF THE FORECAST.  

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