Tropical Cyclone 31P (31P)

WTXS31 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/TROPICAL CYCLONE 31P (THIRTYONE) WARNING NR 018A AMENDED//
RMKS/
1. TROPICAL CYCLONE 31P (THIRTYONE) WARNING NR 018A AMENDED
   01 ACTIVE TROPICAL CYCLONE IN SOUTHIO
   MAX SUSTAINED WINDS BASED ON ONE-MINUTE AVERAGE
   WIND RADII VALID OVER OPEN WATER ONLY
    ---
   WARNING POSITION:
   221200Z --- NEAR 10.0S 133.2E
     MOVEMENT PAST SIX HOURS - 290 DEGREES AT 08 KTS
     POSITION ACCURATE TO WITHIN 060 NM
     POSITION BASED ON CENTER LOCATED BY SATELLITE
   PRESENT WIND DISTRIBUTION:
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
   REPEAT POSIT: 10.0S 133.2E
    ---
   FORECASTS:
   12 HRS, VALID AT:
   230000Z --- 9.3S 131.9E
   MAX SUSTAINED WINDS - 030 KT, GUSTS 040 KT
   WIND RADII VALID OVER OPEN WATER ONLY
   DISSIPATED AS A SIGNIFICANT TROPICAL CYCLONE OVER WATER
    ---
REMARKS:
221500Z POSITION NEAR 9.8S 132.9E.
22APR25. TROPICAL CYCLONE 31P (THIRTYONE), LOCATED APPROXIMATELY
202 NM NORTHEAST OF DARWIN, AUSTRALIA, HAS TRACKED WEST-
NORTHWESTWARD AT 08 KNOTS OVER THE PAST SIX HOURS. AFTER RELEASE OF
THE ORIGINAL WARNING NUMBER EIGHTEEN (WR 018), FURTHER SATELLITE
ANALYSIS REVEALED SIGNIFICANTLY DECAYED CONVECTIVE STRUCTURE OF THE
SYSTEM, WITH SURFACE WINDS BELOW WARNING THRESHOLD. THE PGTW DVORAK
ESTIMATE IS NOW 1.5 AND MAJORITY OF THE DETERMINISTIC AND ENSEMBLE
GUIDANCE AGREES ON FURTHER DECAY OF TC 31P. THIS IS THE FINAL
WARNING ON THIS SYSTEM BY THE JOINT TYPHOON WRNCEN PEARL HARBOR HI.
THE SYSTEM WILL BE CLOSELY MONITORED FOR SIGNS OF REGENERATION.
MINIMUM CENTRAL PRESSURE AT 221200Z IS 1007 MB. MAXIMUM SIGNIFICANT
WAVE HEIGHT AT 221200Z IS 18 FEET.
2. JUSTIFICATION FOR AMENDMENT: FORECAST TRUNCATED TO 12 HOURS AND
SYSTEM FINAL WARNED BASED ON 221230Z METOP-B ASCAT PASS AND THE
ANIMATED SHORTWAVE INFRARED IMAGERY.//
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WDXS31 PGTW 220900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 31P (THIRTYONE) 
WARNING NR 017//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.3S 134.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 225 NM NORTHEAST OF DARWIN, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A POORLY
ORGANIZED LOW-LEVEL CIRCULATION CENTER (LLCC) NEARLY COMPLETELY
OBSCURED BY PERSISTENT CONVECTION. STRONG UPPER LEVEL DIFFLUENCE IS
VISIBLE THROUGH MODERATE EQUATORWARD AND POLEWARD OUTFLOW CHANNELS.
ADDITIONALLY, ENVIRONMENTAL ANALYSIS REVEALS MARGINALLY FAVORABLE
CONDITIONS WITH WARM SEA SURFACE TEMPERATURES (29-30 C), DEEP-LAYER
TROPICAL MOISTURE, OFFSET BY MODERATE (15-20 KTS) VERTICAL WIND
SHEAR. THE INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED
ON ANIMATED VISIBLE IMAGERY SHOWING AN EXPOSED NORTHEASTERN
QUADRANT OF THE LLCC, IN CONJUNCTION WITH AN EXTRAPOLATION FROM AN
EARLIER (220102Z) METOP-C ASCAT PASS SHOWING CURVATURE AND WRAPPING
WITHIN THE WESTERN SEMICIRCLE OF THE CIRCULATION. THE INITIAL
INTENSITY OF 30 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AFOREMENTIONED ASCAT PASS, AS WELL AS AGENCY DVORAK AND AUTOMATED
FIXES LISTED BELOW.

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

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED OVER
NORTHWESTERN AUSTRALIA

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   ADRM: T2.0 - 30 KTS
   CIMSS SATCON: 42 KTS AT 220610Z
   CIMSS ADT: 35 KTS AT 220610Z
   CIMSS AIDT: 30 KTS AT 220610Z
   CIMSS D-MINT: 34 KTS AT 220504Z
   CIMSS D-PRINT: 30 KTS AT 220610Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 15-20 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   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: TC 31P IS FORECAST TO CONTINUE TRACKING
NORTHWESTWARD, FOLLOWING THE NORTHEASTERN PERIPHERY OF A STR TO THE
SOUTH. AS THE ENVIRONMENTAL CONDITIONS REMAIN MARGINALLY FAVORABLE,
THE SYSTEM IS FORECAST TO REACH 35 KTS WITHIN THE NEXT 6-12 HOURS,
FOLLOWED BY A PEAK OF 35-40 KTS BEFORE TAU 36. AFTER THAT, AS THE
SYSTEM APPROACHES THE INDONESIAN TANIMBAR ISLANDS, INCREASING VWS
WILL ONCE AGAIN HINDER DEVELOPMENT. AROUND THAT TIME, TC 31P WILL
FIND ITSELF WITHIN A COMPETING STEERING ENVIRONMENT, AS A
NEAR-EQUATORIAL RIDGE (NER) TO THE EAST WILL IMPACT THE TRACK. THE
SYSTEM IS FORECAST TO STALL AROUND TAU 48, WHILE SIMULTANEOUSLY
DISSIPATING OVER WATER. IF THE VORTEX MANAGES TO MAINTAIN ITS
INTEGRITY, THERE IS HOWEVER POTENTIAL FOR THE SYSTEM TO REGENERATE
AROUND TAU 60, BUT MAJORITY OF THE DETERMINISTIC GLOBAL AND
MESOSCALE GUIDANCE DOES NOT INDICATE THIS AT THIS TIME.

MODEL DISCUSSION: DETERMINISTIC TRACK MODEL GUIDANCE IS IN FAIR
AGREEMENT THROUGHOUT THE 48 HOUR FORECAST PERIOD, WITH ONLY NAVGEM
BEING AN OUTLIER AND SUGGESTING A MORE WESTWARD TRACK, WITH A TURN
TOWARD DARWIN, AUSTRALIA AROUND TAU 48. ALL OTHER AVAILABLE GUIDANCE 
PREDICTS A NORTHWESTWARD TRACK TOWARD THE TANIMBAR ISLANDS AND THE 
JTWC TRACK FORECAST IS ASSESSED WITH MEDIUM CONFIDENCE, WHILE BEING 
PLACED CLOSE TO THE MULTI-MODEL CONSENSUS. CROSS-TRACK SPREAD AT TAU 
48 IS 70 NM, EXCLUDING NAVGEM. ALONG-TRACK SPREAD IS 60 NM, 
INDICATING TRANSLATION SPEED REDUCTION TOWARD THE END OF THE CURRENT 
FORECAST PERIOD. IN TERMS OF INTENSITY, JTWC FORECAST IS ASSESSED 
WITH LOW CONFIDENCE, DUE TO LARGE SPREAD AND UNCERTAINTY. FRIA RAPID 
INTENSIFICATION (RI) GUIDANCE SUGGESTS 25-35 PERCENT RI PROBABILITY 
WITHIN THE NEXT 24 HOURS, WHILE COAMPS-TC IS ALSO ON THE AGGRESSIVE 
SIDE OF THE SPECTRUM, PREDICTING A PEAK INTENSITY OF OVER 45 KTS 
AROUND TAU 48, FOLLOWED BY ANOTHER PEAK OF 65 KTS BEYOND 120 HOURS. 
STATISTICAL-DYNAMICAL MODELS MIRROR THE GUIDANCE OF COAMPS-TC. ON THE 
OTHER END OF THE SPECTRUM, DETERMINISTIC GFS AND HAFS INDICATE LACK 
OF DEVELOPMENT AND EVENTUAL DISSIPATION WITHIN THE DURATION OF THE 
FORECAST PERIOD. JTWC INTENSITY FORECAST IS PLACED WITH LOW 
CONFIDENCE, WITHIN THE MULTI-MODEL CONSENSUS, LEANING CLOSER TOWARD 
THE GUIDANCE OF GFS AND HAFS, CONSIDERING THE CURRENT LACK OF 
ORGANIZATION, AS WELL AS INCREASING SHEAR, HINDERING ANY SIGNIFICANT 
DEVELOPMENT.

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