WDPN31 PGTW 180300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 24W (TWENTYFOUR) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 28.6N 158.2E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 347 NM NORTHEAST OF MINAMI TORI SHIMA,
JAPAN
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 11 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS A COMPACT SYSTEM 
ON THE POLEWARD SIDE OF THE STR THAT HAS RECENTLY REGAINED TROPICAL
CHARACTERISTICS. THE CYCLONE HAS FLARING DEEP CENTRAL CONVECTION
AND MINIMAL FEEDER BANDS. STRATOCUMULUS CLOUD LINES CAN BE SEEN
WRAPPING INTO AN OBSCURED LOW LEVEL CIRCULATION (LLC) FROM THE
NORTHWEST. ADDITIONALLY, A TUTT CELL TO THE SOUTH IS CAUSING 
SUBSIDENCE ALONG THE WESTERN AND SOUTHERN PERIPHERIES. THE INITIAL 
POSITION IS PLACED WITH MEDIUM CONFIDENCE
BASED ON A MICROWAVE LLC FEATURE IN THE 172047Z SSMIS IMAGE. THE
INITIAL INTENSITY IS BASED ON THE PGTW DVORAK ESTIMATE.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
EAST-SOUTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T1.0 - 25 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG EASTWARD
   OTHER FACTORS: COLD AIR INTRUSION FROM THE NORTHWEST AND 
SUBSIDENCE FROM THE TUTT CELL TO THE SOUTH.

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TD 24W IS EXPECTED TO ACCELERATE NORTHEASTWARD
UNDER THE STEERING INFLUENCE OF THE STR. THE MARGINALLY FAVORABLE
CONDITIONS WILL FUEL A WEAK INTENSIFICATION TO A PEAK OF 40KTS AT
TAUS 12-24. AFTERWARD, THE SYSTEM WILL GRADUALLY WEAKEN DUE TO
INCREASING VWS AND COOLING SST. CONCURRENTLY AROUND TAU 24, TD 24W
WILL BEGIN EXTRA-TROPICAL TRANSITION AS IT ENTERS THE COLD
BAROCLINIC ZONE AND BY TAU 48, VERY LIKELY SOONER, WILL TRANSFORM
INTO A GALE-FORCE COLD CORE LOW. 

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT; HOWEVER,
GIVEN THE UNCERTAINTY WITH THE EXTRA-TROPICAL TRANSITION THERE IS
ONLY MEDIUM CONFIDENCE IN THE JTWC TRACK AND INTENSITY FORECASTS.  

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