WDPN31 PGTW 161500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN) 
WARNING NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.5N 148.2E
   INITIAL INTENSITY: 20 KTS
   GEOGRAPHIC REFERENCE: 193 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL DEPRESSION 16W REMAINS VERY DISORGANIZED SYSTEM, AND
DIFFICULT TO LOCATE PRECISELY. ANIMATED ENHANCED INFRARED (EIR)
SATELLITE IMAGERY SHOWS THE LOW-LEVEL CLOUD LINES THAT DEFINE THE
OUTER PERIPHERY OF THE BROAD CIRCULATION. SCATTERED FLARING
CONVECTION TO THE NORTH IS PRODUCING CONVECTIVE BLOWOFF TRANSITING
OVER TOP OF THE ASSESSED CENTER LOCATION, PRECLUDING IDENTIFICATION
OF A DISCREET LOW LEVEL CIRCULATION CENTER (LLCC). A 161022Z
ASCAT-A PASS DEPICTED A VERY DISORGANIZED AND VERY BROAD
CIRCULATION WITH MULTIPLE AREAS OF POSSIBLE SMALL-SCALE ROTATION.
RADAR STORM TRACK DATA FROM ANDERSEN AB IS ALSO STARTING TO PICK UP
THE FIRST HINTS OF CYCLONIC TURNING BUT NOT THE LLCC YET. THE
INITIAL POSITION IS PLACED IN THE NORTHERN MOST EDGE OF THE
NORTHERN AREA OF ROTATION IN THE SCATTEROMETER DATA, CONSISTENT
WITH THE LOW-LEVEL CLOUD LINES IN THE EIR. HOWEVER, IN LIGHT OF THE
WEAK WINDS AND ILL-DEFINED STRUCTURE, THERE IS MEDIUM CONFIDENCE IN
THE INITIAL POSITION. THE INITIAL INTENSITY REMAINS AT 20 KNOTS, AS
THE AFOREMENTIONED SCATTEROMETER DATA SHOWS A VERY WEAK WIND FIELD
WITH MAXIMUM WINDS OF 20 KNOTS CONFINED TO SMALL AREA ABOUT 100 NM
TO THE NORTH OF THE LLCC. ANIMATED WATER VAPOR IMAGERY SHOWS A VERY
LARGE TUTT CELL APPROXIMATELY 600 NM TO THE EAST OF TD 16W, A
SMALLER TUTT APPROXIMATELY 900 NM TO THE NORTHWEST AND AN INDUCED
NORTH-SOUTH RIDGE BETWEEN THEM LYING OVER TOP OF TD 16W WITH WEAK
DIVERGENT FLOW TO THE WEST. GLOBAL MODELS SHOW THIS OVERALL
PATTERN, BUT ARE STILL INDICATING STRONG 200 MB NORTHEASTERLY FLOW
OVER TD 16W, WHILE THE WATER VAPOR AND CONVECTIVE BLOWOFF INDICATE
A STRONG NORTHWESTERLY WIND FLOW TO THE EAST OF THE RIDGE AXIS, AND
DIVERGENT WESTWARD FLOW TO THE WEST OF THE RIDGE.

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

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   CIMSS ADT: 30 KTS AT 1150Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: WHILE THE INITIAL INTENSITY HAS BEEN REDUCED
TO BELOW THE JTWC WARNING THRESHOLD, THE SYSTEM IS FORECASTED TO
REGAIN TROPICAL STORM STRENGTH WITHIN THE NEXT 48 HOURS AND THUS
WARNINGS WILL CONTINUE TO BE ISSUED. TD 16W IS FORECAST TO CONTINUE
TRACKING WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STEERING
RIDGE THROUGH TAU 12, THEN BEGIN A GRADUAL TURN TO THE NORTHWEST
THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE SYSTEM IS
EXPECTED TO CROSS OVER THE NORTHERN TIP OF GUAM, OR JUST TO THE
NORTH, WITHIN THE NEXT 12 TO 15 HOURS. DUE TO VERY BROAD NATURE OF
THE CIRCULATION, THE EXACT CENTER LOCATION, AND THUS THE FORECAST
TRACK, MAY SHIFT PRIOR TO LANDFALL. AS PREVIOUSLY DISCUSSED, THE
UPPER-LEVEL PATTERN IS SOMEWHAT COMPLEX, CONTINUES TO EVOLVE AND IS
CURRENTLY MARGINALLY UNFAVORABLE FOR DEVELOPMENT. HOWEVER, GLOBAL
MODEL FIELDS DEPICT THE TUTT AND TD 16W MOVING WEST AT ROUGHLY THE
SAME SPEED, WHICH KEEPS THE STRONGEST NORTHWESTERLY WINDS OFFSET TO
THE EAST JUST ENOUGH TO ALLOW THE DEVELOPMENT OF SOME DIVERGENT
WESTWARD AND EQUATORWARD OUTFLOW OVER TD 16W. THIS WILL ALLOW FOR
THE SYSTEM TO BEGIN TO INTENSIFY AFTER PASSING GUAM, REACHING
TROPICAL STORM STRENGTH BY TAU 48, AND INTENSIFYING STEADILY
THERAFTER TO A PEAK OF 75 KNOTS BY TAU 120. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN VERY GOOD AGREEMENT THROUGH
THE EARLY PORTION OF THE FORECAST, WITH ONLY A 60 NM SPREAD OUT TAU
48. CROSS TRACK SPREAD INCREASES TO A MODEST 150 NM AT TAU 120.
HOWEVER, THE ECMWF ENSEMBLE AND UKMET ENSEMBLE BOTH LOSS THE VORTEX
AFTER TAU 48, WHICH PULLS BACK CONSENSUS MEAN, LEADING TO
SIGNIFICANT ALONG TRACK SPREAD AFTER TAU 72. THE JTWC FORECAST LIES
ALONG THE SOUTHERN EDGE OF THE GUIDANCE ENVELOPE THROUGH THE
DURATION OF THE FORECAST, AND WELL AHEAD OF THE CONSENSUS MEAN
AFTER TAU 72. INTENSITY GUIDANCE IS IN OVERALL AGREEMENT WITH
LITTLE TO NO INTENSIFICATION THROUGH TAU 12, THEN STEADY
INTENSIFICATION THROUGH THE REMAINDER OF THE FORECAST. THE JTWC
FORECAST CLOSELY TRACKS THE CONSENSUS MEAN THROUGH THE FORECAST
PERIOD WITH MEDIUM CONFIDENCE. 

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