WDPS31 PGTW 012100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 15P (JUDY) 
WARNING NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.1S 171.5E
   INITIAL INTENSITY: 100 KTS
   GEOGRAPHIC REFERENCE: 273 NM SOUTHEAST OF PORT VILA, VANUATU
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 42 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
OVER THE PAST HOUR, AS THE TERMINATOR LINE SWEEPS ACROSS THE CORAL
SEA, ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TIGHTLY
WRAPPING AND EXPANSIVE CONVECTIVE CLOUD COVER FULLY OBSCURING THE
LOW LEVEL CIRCULATION CENTER (LLCC). A 011756Z SSMIS 89GHZ
MICROWAVE IMAGE SHOWS DEEP CONVECTIVE BANDING FEATURES DOMINATING
THE EASTERN SEMICIRCLE WHILE THE WESTERN PORTION OF THE SYSTEM IS
DEVOID OF SUCH FEATURES. THE INITIAL POSITION IS PLACED WITH MEDIUM
CONFIDENCE BASED ON MSI AND SSMIS IMAGERY. THE INITIAL INTENSITY OF
100 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON AGENCY DVORAK
INTENSITY ESTIMATES INDICATING T5.5-T6.0 THOUGH DATA T NUMBERS
INDICATE T5.0 WHICH IS STILL HIGHER THAN AUTOMATED INTENSITY
ESTIMATES WHICH ARE WEAKENING THE SYSTEM TOO RAPIDLY.

INITIAL WIND RADII BASIS: PERSISTENCE 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T5.5 - 102 KTS
   KNES: T6.0 - 115 KTS
   PHFO: T5.5 - 102 KTS
   CIMSS SATCON: 83 KTS AT 011425Z
   CIMSS ADT: 79 KTS AT 011730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 20-25 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: LOW

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 15P (JUDY) IS FORECAST TO CONTINUE ON ITS
SOUTHEASTWARD TRACK AS IT CONTINUES ALONG THE OUTER PERIPHERY OF
STR TO THE EAST-NORTHEAST. AS 15P TRANSITS POLEWARD, IT WILL BE IN
AN INCREASINGLY HOSTILE ENVIRONMENT CHARACTERIZED BY STRONGER VWS,
AND INCREASING DRY AIR ENTRAINMENT, THESE FACTORS WILL CONSPIRE TO
WEAKEN THE SYSTEM TO AROUND 80 KTS BY TAU 24. AFTER TAU 24, THE
SYSTEM WILL BEGIN ITS SUBTROPICAL TRANSITION (STT) AND A FURTHER
DECREASE IN INTENSITY TO 65 KTS IS ANTICIPATED AS THE SYSTEM
CROSSES THE 26 C ISOTHERM. BY TAU 36, 15P WILL CONTINUE ITS STT
AND WILL CONTINUE TO FEEL THE EFFECTS OF DRY AIR ENTRAINMENT FROM
THE NORTHWEST BEING WRAPPED INTO THE CENTER. BY TAU 48, 15P
WILL HAVE WEAKENED TO AROUND 55 KTS AND BECOME FULLY SUBTROPICAL.

MODEL DISCUSSION: WITH THE EXCEPTION OF NVGM AND THE ECMWF-ENSEMBLE
NUMERICAL MODELS ARE IN GOOD AGREEMENT THAT 15P WILL CONTINUE
POLEWARD OF THE STR AND GRADUALLY GUIDE EAST-SOUTHEASTWARD AS IT
COMPLETES STT. FOR THIS REASON THE JTWC TRACK FORECAST IS PLACED
WITH HIGH CONFIDENCE. WITH THE EXCEPTION OF DECAY-SHIPS, RELIABLE
MODEL INTENSITY GUIDANCE IS IN GOOD AGREEMENT WITH ALL REMAINING
MEMBERS WEAKENING THE SYSTEM THROUGH STT BY TAU 48 AND BEYOND THE
FORECAST PERIOD. FOR THIS REASON THE JTWC INTENSITY FORECAST IS
ALSO PLACED WITH HIGH CONFIDENCE.  

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