WDPN33 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 19W (NINETEEN)
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.2N 135.4E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 543 NM WEST OF NAVSTA GUAM
   MOVEMENT PAST 6 HOURS: NORTH-NORTHWESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD
AND POORLY ORGANIZED TROPICAL DEPRESSION (TD) 19W, WITH THE MAJORITY
OF THE DEEP CONVECTION LOCATED IN THE NORTHWESTERN QUADRANT. OVER THE
LAST 6 HOURS, CENTRAL CONVECTION HAS PERSISTED AND THE OUTER BANDING
HAS STARTED TO WRAP TIGHTER INTO A NEARLY FULLY OBSCURED LOW-LEVEL
CIRCULATION CENTER (LLCC). ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY
FAVORABLE CONDITIONS FOR DEVELOPMENT, WITH WARM (29-30 C) SEA SURFACE
TEMPERATURES (SST), A GOOD EQUATORWARD OUTFLOW CHANNEL, AND LOW (10-15
KTS) VERTICAL WIND SHEAR (VWS). THE NORTHWESTERN QUADRANT CONTAINS
HIGH MOISTURE LEVELS THROUGHOUT THE ATMOSPHERIC COLUMN, HOWEVER, MUCH
DRIER AIR SURROUNDS THE SYSTEM TO THE EAST AND NORTHEAST. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON A 221130Z METOP-B
ASCAT PASS, SUPPORTED BY EXTRAPOLATION FROM A 221023Z F16 SSMIS
MICROWAVE SUITE. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE SAME ASCAT PASS, AS WELL AS 220908Z SMOS WIND
SPEED DATA, AND THE OBJECTIVE AND AUTOMATED FIXES LISTED BELOW.

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

CURRENT STEERING MECHANISM: NEAR-EQUATORIAL RIDGE (NER) TO THE
EAST-SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T2.0 - 30 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T2.0 - 30 KTS
   CIMSS D-MINT: 35 KTS AT 221024Z
   CIMSS D-PRINT: 29 KTS AT 221200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 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: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 19W IS FORECAST TO BEGIN TURNING NORTHWARD
AND NORTHEASTWARD UNDER THE STEERING INFLUENCE OF A NER CENTERED TO
THE EAST-SOUTHEAST OVER THE NEXT 6 TO 12 HOURS. AROUND TAU 48, A
SUBTROPICAL RIDGE TO THE NORTHEAST WILL TAKE OVER AS THE PRIMARY
STEERING MECHANISM, RESULTING IN TD 19W TURNING NORTHWARD AND
NORTHWESTWARD, TRANSITING IN THE WAKE OF TYPHOON 17W (SAUDEL).
INITIALLY MARGINALLY FAVORABLE ENVIRONMENTAL CONDITIONS WILL RESULT
IN SLIGHT INTENSIFICATION, WITH THE SYSTEM ATTAINING 35 KTS OVER
THE NEXT 12-24 HOURS. HOWEVER, AS TD 19W TRANSITS NORTHEASTWARD AND
TOWARD AN UPPER-LEVEL LOW, THE WIND SHEAR IS EXPECTED TO INCREASE
SIGNIFICANTLY, LIKELY TO 25-30 KTS AROUND TAU 36. AT THE SAME TIME,
THE SYSTEM WILL ENCOUNTER DRIER AIR, WHICH WILL ENTRAIN INTO THE CORE
OF THE VORTEX. AS A RESULT, THE INTENSITY IS EXPECTED TO DROP TO 20-25
KTS BY TAU 48. AFTERWARD, THE SYSTEM WILL FOLLOW THE TAIL END OF
THE WIND FIELD BELONGING TO TYPHOON 17W AND WILL STRUGGLE TO MAINTAIN
VERTICAL STRUCTURE. DISSIPATION OVER WATER IS EXPECTED NO LATER THAN
TAU 72, BUT IS POSSIBLE MUCH EARLIER IF THE VWS AND DRY AIR ERODE THE
STRUCTURE OF THE STORM SOONER.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN OVERALL FAIR
AGREEMENT, AS EVIDENCED BY A 90 NM CROSS-TRACK SPREAD AT TAU 48,
WITH ALL MODELS DEPICTING A SIMILAR RESPONSE TO THE CURRENT STEERING
ENVIRONMENT. AFTER TAU 48, THE GUIDANCE ENVELOPE INCREASES
SIGNIFICANTLY AS A RESULT OF SOME MODELS (GFS, HAFS) PREDICTING
DISSIPATION AS EARLY AS TAU 48, WHILE OTHERS (COAMPS-TC AND
STATISTICAL-DYNAMICAL GUIDANCE) PRESERVE BORDERLINE INTENSITY
THROUGHOUT THE CURRENT FORECAST PERIOD. AS SUCH, BOTH THE TRACK AND
INTENSITY FORECASTS ARE ASSESSED WITH MEDIUM CONFIDENCE. WHILE THE
SYSTEM IS NOT EXPECTED TO REACH WIND SPEEDS HIGHER THAN 35 KTS, THE
TIMING OF DISSIPATION IS THE MAIN UNCERTAINTY FACTOR.

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