WDPN31 PGTW 240300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 12W (TWELVE) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.8N 143.6E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 63 NM WEST-NORTHWEST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
DEPRESSION (TD) 12W WITH A DISORGANIZED LOW-LEVEL CIRCULATION
CENTER (LLCC) AND FLARING CONVECTION ALONG THE SOUTHERN PERIPHERY.
A 232111Z SSMIS 91 GHZ MICROWAVE IMAGE REVEALED THE DEEP CONVECTION
CONFINED TO THE SOUTHERN SEMICIRCLE OF THE CIRCULATION AND
LOW-LEVEL CLOUDS LOOSELY WRAPPING INTO THE ASSESSED CENTER.
ENVIRONMENTAL ANALYSIS INDICATES THAT 12W IS IN A MARGINALLY
FAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE EQUATORWARD OUTFLOW
ALOFT, HIGH (25-30 KTS) NORTHERLY VERTICAL WIND SHEAR, AND WARM
(29-30 C) SEA SURFACE TEMPERATURES. THE INITIAL POSITION IS PLACED
WITH MEDIUM CONFIDENCE BASED ON THE 240032Z METOP-C ASCAT IMAGE
SHOWING A BROAD CENTER NORTHWEST OF GUAM. THE INITIAL INTENSITY OF
30 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE SAME ASCAT
IMAGE SHOWING A PATCH OF 30 KNOT NON-FLAGGED BARBS WITHIN THE
SOUTHERN SEMICIRCLE.

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

CURRENT STEERING MECHANISM: WEAK RIDGING THAT IS BUILDING TO THE
EAST OF THE SYSTEM.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS ADT: 29 KTS AT 240020Z
   CIMSS AIDT: 32 KTS AT 240020Z
   CIMSS DPRINT: 22 KTS AT 240020Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE 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: TD 12W IS FORECAST TO BEGIN TRACKING NORTHWARD
AS RIDGING BUILDS IN TO THE EAST OF THE VORTEX. THIS NORTHWARD
TRACK IS FORECAST TO PERSIST THROUGH TAU 96 AS 12W RIDES ALONG THE
WESTERN PERIPHERY OF THE RIDGE. NEAR TAU 96, A SUBTROPICAL RIDGE
CENTERED OVER THE SEA OF JAPAN WILL BEGIN TO INTERACT WITH THE
VORTEX AND WILL PULL 12W NORTHWESTWARD THROUGH TAU 120. REGARDING
INTENSITY, 12W IS FORECAST TO STEADILY INTENSIFY OVER THE NEXT 72
HOURS. HOWEVER, THE ENVIRONMENT WILL BE COMPLEX, WITH ENVIRONMENTAL
FACTORS FIGHTING AGAINST EACH OTHER FOR THE DEVELOPMENT OF 12W. 
THROUGH TAU 48, THE WIND FIELD WILL CONTINUE TO CONSOLIDATE AND WILL 
ALLOW FOR INTENSIFICATION OF THE SYSTEM.  AFTER TAU 48, AN UPPER-
LEVEL TROUGH WILL SET UP TO THE NORTHEAST OF THE SYSTEM, DRASTICALLY 
ENHANCING EASTWARD AND EQUATORWARD OUTFLOW. AT THE SAME TIME, 
NORTHERLY VERTICAL WIND SHEAR WILL RISE TO ABOVE 40 KTS. THE RESULT 
OF THESE TWO FACTORS IS FORECAST TO RESULT IN SLIGHT INTENSIFICATION 
FROM 45 KTS AT TAU 48 TO 60 KTS AT TAU 96. AFTER TAU 96, DRY AIR 
ENTRAINMENT IS EXPECTED TO MARKEDLY INCREASE AS THE VORTEX BEGINS TO 
INTERACT WITH AN UPPER-LEVEL CYCLONE THAT FORMS SOUTH OF HONSHU. THIS 
WILL CAUSE 12W TO STOP INTENSIFYING THROUGH THE REMAINDER OF THE 
FORECAST PERIOD.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGH TAU 72 WITH THE PRIMARY OUTLIERS BEING THE GFS
AND THE GFS ENSEMBLE MEAN, WHICH ARE ABOUT 170 NM FURTHER NORTH AT
TAU 72 THAN THE BULK OF GUIDANCE. THE JTWC TRACK FORECAST IS PLACED
IN LINE WITH THE MULTI-MODEL CONSENSUS (SLIGHTLY SLOWER TO OFFSET
GFS) THROUGH TAU 96 AND THEN CLOSER TO THE ECMWF ENSEMBLE MEAN
THROUGH TAU 120. OVERALL, THERE IS MEDIUM CONFIDENCE IN THE JTWC
TRACK FORECAST THOUGH TAU 72 AND THEN LOW CONFIDENCE THEREAFTER.
INTENSITY GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 96 WITH ALL
MODELS SUGGESTING STEADY INTENSIFICATION. AFTER TAU 96, HWRF AND
GFS BOTH SUGGEST WEAKENING THROUGH TAU 120 WHILE HAFS-A SUGGESTS
FURTHER INTENSIFICATION. THE JTWC INTENSITY FORECAST IS PLACED
CLOSE TO CONSENSUS THROUGH TAU 96 AND THEN HALTS THE
INTENSIFICATION THROUGH TAU 120 DUE TO THE EXPECTED DEGRADED
ENVIRONMENT AS THE SYSTEM INTERACTS WITH THE UPPER-LEVEL CYCLONE.

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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