WDPN31 PGTW 100900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 14W (FOURTEEN) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.6N 145.7E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 126 NM SOUTH-SOUTHEAST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) AND GUAM RADAR IMAGERY 
DEPICT A BROAD, EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH 
FORMATIVE CONVECTIVE BANDS WRAPPING INTO THE BROAD LLCC. SUBSEQUENT 
RADAR IMAGERY AFTER 100600Z APPEARS TO INDICATE SOME IMPROVED BANDING 
OVER THE SOUTHWESTERN QUADRANT, HOWEVER, THE LLCC REMAINS BROAD. THUS, 
OVERALL CONFIDENCE IN THE INITIAL POSITION REMAINS MEDIUM. DUE TO THE 
BROAD NATURE OF THE CENTER, SIGNIFICANT JUMPS IN BOTH THE INITIAL 
POSITION AND CPA CALCULATIONS OVER THE GUAM REGION ARE POSSIBLE. 
UPPER-LEVEL ANALYSIS REVEALS A FAVORABLE ENVIRONMENT WITH A POINT 
SOURCE OVERHEAD PROVIDING NEAR RADIAL OUTFLOW AND LOW VERTICAL WIND 
SHEAR. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH 
CONFIDENCE BASED ON THE RJTD SUBJECTIVE DVORAK ESTIMATE OF T2.0 (30 
KNOTS) SUPPORTED BY THE CIMSS OBJECTIVE INTENSITY ESTIMATES RANGING 
FROM 28 TO 32 KNOTS. ADDITIONALLY, SURFACE OBSERVATIONS FROM PGUM AND 
PGUA INDICATE SUSTAINED WINDS OF 20 KNOTS GUSTING TO 30 KNOTS. UPPER-
AIR DATA FROM THE GUAM INDICATES INCREASING WINDS NEAR THE GRADIENT 
LEVEL OF 30 KNOTS.

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

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) ENTRENCHED TO THE EAST AND NORTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 29 KTS AT 100600Z
   CIMSS AIDT: 32 KTS AT 100600Z
   CIMSS DPRINT: 29 KTS AT 100500Z
   CIMSS DMINT: 28 KTS AT 100541Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE RADIAL

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: TROPICAL DEPRESSION (TD) 14W IS SLOWLY 
CONSOLIDATING BUT IS EXPECTED TO GRADUALLY INTENSIFY AS IT TRACKS
NORTHWESTWARD ALONG THE WESTERN PERIPHERY OF THE LOW- TO MID-LEVEL
STR THROUGH TAU 48. THE SYSTEM SHOULD REACH MINIMAL TROPICAL STORM
STRENGTH AS IT TRACKS NEAR GUAM AND INTENSIFY AT A SLIGHTLY FASTER
RATE TO ABOUT 55 KNOTS AT TAU 48. ENVIRONMENTAL CONDITIONS APPEAR
CONDUCIVE THROUGH TAU 48. AFTER TAU 48, THE SYSTEM WILL GRADUALLY
TURN WEST-NORTHWESTWARD AS IT TRACKS UNDER THE STEERING INFLUENCE
OF THE STR TO THE NORTH, WHICH SHOULD REMAIN STRONG THROUGH TAU 120
DUE TO THE ZONAL MIDLATITUDE FLOW AND LACK OF A SIGNIFICANT MAJOR
SHORTWAVE TROUGH THAT WOULD TYPICALLY WEAKEN THE STR. SIGNIFICANT
DRY AIR ENTRAINMENT IS FORECAST BY GFS AND ECMWF TO IMPACT AND
HINDER DEVELOPMENT FROM TAU 48 TO TAU 72. DRY AIR ENTRAINMENT IS
ALSO INDICATED IN THE MESOSCALE MODELS BUT WITH A LESSER,
SHORT-TERM EFFECT. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE REMAINS IN FAIR
AGREEMENT THROUGH TAU 72, WITH A 90NM CROSS-TRACK SPREAD IN
GUIDANCE FROM TAU 48 TO TAU 72. HOWEVER, UNCERTAINTY IN THE INITIAL
POSITION SUPPORTS MEDIUM TRACK CONFIDENCE. AFTER TAU 72, MODEL
GUIDANCE DIVERGES SHARPLY WITH INCREASING UNCERTAINTY IN THE TRACK
AND LOW OVERALL CONFIDENCE. ECMWF AND GFS ENSEMBLE GUIDANCE
INDICATES A LARGE SPREAD OF SOLUTIONS WITH STRAIGHT-RUNNER TRACKS
OVER TAIWAN TO RECURVE TRACKS OVER THE KOREAN PENINSULA AND WESTERN
JAPAN. RELIABLE INTENSITY GUIDANCE SHOWS A DOUBLE PEAK, AT TAU 48 AND 
AT TAU 120 DISRUPTED BY A PERIOD OF POSSIBLE DRY AIR ENTRAINMENT. THE 
DIFFERENCE IN THE DEGREE OF DRY AIR ENTRAINMENT BETWEEN THE GLOBAL 
MODELS AND THE MESOSCALE MODELS IS KEY TO UNDERSTANDING THE SPLIT IN 
INTENSITY GUIDANCE AT THIS TIME. SPECIFICALLY, GFS SHOWS A PEAK 
INTENSITY OF 85 KNOTS NEAR TAU 120 WHILE THE MESOSCALE MODELS
INDICATE A MUCH HIGHER PEAK INTENSITY OF 120-130 KNOTS. THEREFORE,
THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST THROUGH
TAU 72 AND LOW CONFIDENCE AFTER TAU 72.      

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