Advisories

WDPN32 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (PEILOU) 
WARNING NR 026//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 32.0N 168.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 766 NM NORTH OF WAKE ISLAND
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A FULLY EXPOSED 
LOW LEVEL CIRCULATION CENTER (LLCC) WITH ISOLATED POCKETS OF DEEP 
CONVECTION FLARING ALONG THE EASTERN FLANK, ALONG THE CONVERGENT 
STREAMLINES. OTHER NEARBY FEATURES OF NOTE IN THE MSI ARE A SMALL AREA 
OF ROTATION DEVELOPING TO THE SOUTHWEST, ALONG A DEVELOPING FRONTAL 
BOUNDARY, AND A SMALL CYCLONIC CIRCULATION TO THE WEST, EMBEDDED IN 
THE NORTHERLY FLOW TO THE WEST OF TD 13W. THE  INITIAL POSITION IS 
ASSESSED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN THE MSI. 
THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON A 
BLEND OF THE AVAILABLE OBJECTIVE AND SUBJECTIVE INTENSITY ESTIMATES 
NOTED BELOW AND IS CONSISTENT WITH EARLIER SCATTEROMETER DATA. UPPER-
LEVEL ANALYSIS SHOWS A 500MB TROUGH LOCATED JUST WEST OF TD 13W, AND 
STRONG WEST-NORTHWESTERLY FLOW AT 200MB. THE SYSTEM IS IN THE EARLY 
PHASES OF EXTRATROPICAL TRANSITION (ETT) AND IS LIKELY ALREADY 
SUBTROPICAL BASED ON BOTH MANUAL AND AUTOMATED PHASE CLASSIFICATION 
DIAGNOSTICS. OVERALL, THE ENVIRONMENT IS UNFAVORABLE, WITH BORDERLINE 
SSTS (25-26C), HIGH WESTERLY WIND SHEAR, AND WEAK OUTFLOW ALOFT, AS 
WELL AS SIGNIFICANT DRY AIR ENTRAINMENT ABOVE 700MB, CAPPING THE 
VORTEX.

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

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED FAR TO THE EAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   CIMSS SATCON: 38 KTS AT 130540Z
   CIMSS ADT: 28 KTS AT 130610Z
   CIMSS AIDT: 31 KTS AT 130610Z
   CIMSS D-MINT: 33 KTS AT 130529Z
   CIMSS D-PRINT: 28 KTS AT 130610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 25-30 KTS
   SST: 25-26 CELSIUS
   OUTFLOW: WEAK POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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) 13W WILL CONTINUE TO
ACCELERATE NORTHEASTWARD, ALONG THE WESTERN PERIPHERY OF AN EXPANSIVE  
STR CENTERED TO THE EAST, FOR THE DURATION OF THE FORECAST PERIOD. THE 
SYSTEM IS ALREADY BORDERLINE SUBTROPICAL AND IS IN THE MIDST OF ETT. 
THE SYSTEM IS MOVING NORTHEASTWARD IN PHASE WITH A 500MB TROUGH, 
LOCATED AT THE NOSE OF A 200MB JET MAX ASSOCIATED WITH THE SUBTROPICAL 
JET FINGER. OVER THE NEXT 24 HOURS, THE MID-LEVEL TROUGH DEEPENS AS IT 
IS REINFORCED BY THE APPROACH OF A RAPIDLY DEEPENING 200MB TROUGH AND 
ASSOCIATED JET MAX. TD 13W WILL MOVE INTO THE RIGHT REAR ENTRANCE 
REGION OF THIS JET MAX, WHILE REMAINING IN PHASE WITH THE 500MB 
TROUGH, RESULTING IN BOTH THE RAPID COMPLETION OF ETT AND A BURST OF 
BAROCLINIC CYCLOGENESIS AS IT COMPLETES TRANSITION. 

MODEL DISCUSSION: TRACK GUIDANCE IS IN STRONG AGREEMENT, WITH
MINIMAL CROSS- OR ALONG-TRACK SPREAD THROUGH THE DURATION OF THE
FORECAST, LENDING HIGH CONFIDENCE TO THE JTWC TRACK. INTENSITY
GUIDANCE IS ALSO IN GOOD AGREEMENT IN DEPICTING INTENSIFICATION
THROUGH TAU 24 AS THE SYSTEM COMPLETES ETT. 

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   INTENSITY 00-72 HR: HIGH//
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