WDPN32 PGTW 130300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 13W (PEILOU) WARNING 
NR 025//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 31.1N 166.6E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 786 NM NORTHEAST OF MINAMI TORI SHIMA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS THE FULLY
EXPOSED, ELONGATED LOW LEVEL CIRCULATION CENTER OF TROPICAL
DEPRESSION (TD) 13W. FLARING CONVECTION REMAINS CONFINED TO THE
EASTERN SEMICIRCLE AND IS QUICKLY SHEARED FROM THE NORTHWEST, WHILE
DRY AIR ENTRAINMENT IS EVIDENT IN MSI BY THE FIELD OF STRATOCUMULUS
CLOUDS ON THE WESTERN FLANK. FURTHER ANALYSIS REVEALS A WHOLLY
UNFAVORABLE ENVIRONMENT CHARACTERIZED BY MODERATE TO HIGH (20-25
KTS) VERTICAL WIND SHEAR, MARGINAL (26-27 C) SEA SURFACE TEMPERATURES,
AND WEAK POLEWARD OUTFLOW ALOFT. A 122318Z METOP-C ASCAT FURTHER 
CONFIRMS THE ELONGATED LLCC AND ASYMMETRICAL WIND FIELD, WITH ALL 25-
30 KT WINDS BEING CONFINED TO THE SOUTHEAST QUADRANT. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON MSI AND ASCAT DATA. 
THE INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE BASED ON ASCAT 
DATA AS IT IS MORE REPRESENTATIVE THAN THE SPREAD OF AGENCY DVORAK 
FIXES AND CIMSS OBJECTIVE ESTIMATES LISTED BELOW WHICH STRUGGLE WITH 
SYSTEMS LACKING CONVECTION.

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

CURRENT STEERING MECHANISM: EASTERN EXTENSION OF A NEAR-EQUATORIAL
RIDGE (NER) CENTERED TO THE SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.0 - 25 KTS
   CIMSS SATCON: 36 KTS AT 122210Z
   CIMSS ADT: 26 KTS AT 122330Z
   CIMSS AIDT: 27 KTS AT 122330Z
   CIMSS D-MINT: 34 KTS AT 122252Z
   CIMSS D-PRINT: 28 KTS AT 122330Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: UNFAVORABLE
   VWS: 20-25 KTS
   SST: 26-27 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: THE FORECAST PHILOSOPHY HAS CHANGED
TO EXTRATROPICAL TRANSITION RATHER THAN DISSIPATION OVER WATER.

FORECAST DISCUSSION: TD 13W IS FORECAST TO CONTINUE TRACKING
NORTHEASTWARD WITH INCREASING TRACK SPEED FOR THE REMAINDER OF THE
FORECAST PERIOD UNDER THE STEERING INFLUENCE OF THE EASTERN
EXTENSION OF A NEAR-EQUATORIAL RIDGE CENTERED TO THE SOUTH. A
SIGNIFICANT CHANGE TO THE FORECAST HAS BEEN MADE, AS TD 13W IS
EXPECTED TO BEGIN EXTRATROPICAL TRANSITION (ETT) BY TAU 24 AS IT 
CROSSES THE 26 C ISOTHERM, APPROACHES THE UPPER LEVEL JET, INCREASED 
VWS, AND FURTHER DRY AIR ENTRAINMENT WILL CAUSE THE SYSTEM TO CONTINUE 
TO ELONGATE AND BECOME EMBEDDED WITHIN THE LARGER TROUGH CENTERED TO 
THE NORTHEAST, ULTIMATELY COMPLETING ETT BY TAU 36. REGARDING 
INTENSITY, TD 13W IS EXPECTED TO INTENSIFY DURING THIS TRANSITION AND 
BE FULLY EXTRATROPICAL WITH GALE STRENGTH WINDS.

MODEL DISCUSSION: TRACK MODEL GUIDANCE REMAINS IN GOOD AGREEMENT ON
THE NORTHEASTWARD TRACK OF TD 13W FOR THE REMAINDER OF THE FORECAST
PERIOD. THE OFFICIAL JTWC FORECAST TRACK IS PLACED WITH HIGH
CONFIDENCE, CLOSELY IN LINE WITH THE MULTI-MODEL CONSENSUS.
INTENSITY MODEL GUIDANCE IS IN GOOD AGREEMENT ON THE
INTENSIFICATION OUT TO TAU 36 AS TD 13W COMPLETES ETT. THE OFFICIAL
JTWC INTENSITY FORECAST IS ASSESSED WITH HIGH CONFIDENCE, SLIGHTLY
BELOW THE MULTI-MODEL CONSENSUS AND ENDING EARLIER AS THE BULK OF
THE GUIDANCE DOES NOT REPRESENT THE FORECAST ETT ACCURATELY.

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