WDPN31 PGTW 031500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 17W (SEVENTEEN) 
WARNING NR 007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.5N 158.3E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 985 NM EAST-SOUTHEAST OF MISAWA, JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TD 17W HAS STRUGGLED TO CONSOLIDATE DUE PRIMARILY TO SIGNIFICANT
DRY AIR ENTRAINMENT THROUGH THE MID- AND UPPER-LEVELS OF THE
SYSTEM. CONSEQUENTLY, DEEP CONVECTION IS ISOLATED TO THE SOUTHWEST
QUADRANT OF THE SYSTEM. ANIMATED ENHANCED INFRARED SATELLITE IMAGERY 
REVEALS SHALLOW BANDING WRAPPING INTO AN ELONGATED, EXPOSED LOW 
LEVEL CIRCULATION CENTER (LLCC) POSITIONED ON THE NORTHERN EDGE OF A 
CLUSTER OF FLARING DEEP CONVECTION, WHICH PROVIDES MEDIUM CONFIDENCE 
IN THE INITIAL POSITION. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED 
WITH MEDIUM CONFIDENCE BASED ON THE LATEST DVORAK INTENSITY 
ESTIMATES. EQUATORWARD OUTFLOW REMAINS ROBUST DUE TO AN UPPER-LOW 
POSITIONED TO THE SOUTHWEST.

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

CURRENT STEERING MECHANISM: LOW- TO MID-LEVEL SUBTROPICAL RIDGE
(STR) POSITIONED TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T1.0 - 25 KTS
   CIMSS SATCON: 38 KTS AT 031027Z
   CIMSS ADT: 30 KTS AT 031140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 15-20 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT


ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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 IS FORECAST TO ACCELERATE NORTHEASTWARD 
THROUGH TAU 36 AS IT ROUNDS THE NORTHWEST PERIPHERY OF THE STR. TD 
17W WILL BEGIN TO ENCOUNTER STRONG VERTICAL WIND SHEAR (25 KNOTS) 
ASSOCIATED WITH THE MIDLATITUDE WESTERLIES AND COOLER SEA SURFACE 
TEMPERATURES (24-21C) AFTER TAU 24, WHICH WILL LEAD TO DISSIPATION 
BY TAU 36. THE SYSTEM IS NOT EXPECTED TO TRANSITION INTO A STRONG 
COLD CORE LOW DUE TO THE LACK OF UPPER-LEVEL TROUGH SUPPORT BUT WILL 
LIKELY GET ABSORBED INTO THE FRONTAL BOUNDARY NEAR OR NORTH OF 40N.  

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN TIGHT 
AGREEMENT AND SUPPORTS THE JTWC FORECAST TRACK WITH HIGH CONFIDENCE. 
THERE IS MEDIUM CONFIDENCE IN THE JTWC INTENSITY FORECAST WITH HWRF 
AND SHIPS (GFS) GUIDANCE INDICATING INTENSIFICATION TO 35-40 KNOTS 
AFTER TAU 24 BUT THIS SCENARIO IS CURRENTLY ASSESSED AS LOW 
PROBABILITY.  

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