Advisories

WDPN31 PGTW 250300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 30W (IN-FA) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.5N 165.3E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 224 NM NORTHWEST OF KWAJALEIN
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 30W AS A GRADUALLY CONSOLIDATING SYSTEM. THE UPPER LEVEL
CONVECTION NEAR THE CENTER IS BEGINNING TO WRAP AROUND THE CENTER
AXIS, SIGNALLING 30W IS VERTICALLY STACKED AND PRIMED TO INTENSIFY.
THE 242015Z SSMIS REVEALS A SYMMETRICAL, BUT FAINT, MICROWAVE EYE
FEATURE IN THE LOWER LEVELS AND A LARGE, RAGGED MICROWAVE EYE
FEATURE IN THE UPPER LEVELS. THE MICROWAVE ALSO REVEALS THE BULK OF
THE DEEP CONVECTION LIES WEST OF THE CENTER. ENVIRONMENTAL ANALYSIS
REVEALS A FAVORABLE ENVIRONMENT, CHARACTERIZED BY LOW (10-15 KTS)
VERTICAL WIND SHEAR (VWS), WARM (28-29 C) SEA SURFACE TEMPERATURES
(SST), MODERATE (75-100 KJ PER CM SQUARED) OCEAN HEAT CONTENT
(OHC), AND A STRENGTHENING POLEWARD OUTFLOW CHANNEL.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK STEERING ENVIRONMENT PREDOMINANTLY
CONTROLLED BY A NEAR EQUATORIAL RIDGE (NER) CENTERED TO THE
SOUTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.5 - 55 KTS
   RCTP: T3.0 - 45 KTS
   PHFO: T3.5 - 55 KTS
   CIMSS ADT: 51 KTS AT 242340Z
   CIMSS AIDT: 39 KTS AT 242340Z
   CIMSS D-MINT: 56 KTS AT 242014Z
   CIMSS D-PRINT: 53 KTS AT 242340Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 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: TS 30W (IN-FA) IS FORECAST TO CONTINUE
TRACKING NORTHWESTWARD WHILE IT REMAINS ON THE FRINGES OF A
BUILDING NER CENTERED TO ITS SOUTHEAST. THE SYSTEM REMAINS IN A
WEAK STEERING ENVIRONMENT, BUT IS EXPECTED TO CONTINUOUSLY
ACCELERATE TO THE NORTHWEST AS THE NER BUILDS AND GUIDES THE STORM
THROUGH TAU 24. BY AROUND TAU 24, A SUBTROPICAL RIDGE (STR) TO THE
NORTHWEST IS EXPECTED TO STRETCH TO THE EAST, CAUSING A COMPETING
STEERING ENVIRONMENT BETWEEN TAU 36-60. THE STR IS EXPECTED TO GAIN
STEERING AUTHORITY BY TAU 48, AND CAUSE 30W TO ACCELERATE
WEST-NORTHWESTWARD THROUGH THE REMAINDER OF THE FORECAST PERIOD.
REGARDING INTENSITY, 30W IS FORECAST TO BEGIN A PERIOD OF RAPID
INTENSIFICATION (RI) IMMEDIATELY. 30W IS EXPECTED TO RI THROUGH TAU
24, WHEN THE COMPETING STEERING ENVIRONMENT TEMPORARILY HALTS
INTENSIFICATION. 30W MAY ALSO BRIEFLY WEAKEN AROUND TAU 36-60. ONCE
30W TRANSITIONS STEERING ENVIRONMENTS AND BEGINS TRACKING
WEST-NORTHWESTWARD, IT WILL ENTER A REGION OF ELEVATED (100-125 KJ
PER CM SQUARED) OHC VALUES, SUPPORTING A SECOND ROUND OF
INTENSIFICATION. 30W IS EXPECTED TO PEAK AT TAU 120, THOUGH
ADDITIONAL INTENSIFICATION MAY OCCUR OUTSIDE THE FORECAST PERIOD. 

MODEL DISCUSSION: DETERMINISTIC MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT THROUGH TAU 120, THOUGH THERE ARE A FEW OUTLIERS (GFS,
GEFS, HAFS-A, COAMPS-TC) THAT DEPICT 30W TRACKING NORTHEASTWARD
THROUGH TAU 48-60 BEFORE LOOPING BACK TO THE WEST-NORTHWEST.
DISREGARDING THOSE MEMBERS, THE JTWC TRACK FORECAST LIES WITH THE
BULK OF PHYSICS-BASED MODEL GUIDANCE AND ALL EXPERIMENTAL AI
MEMBERS WITH OVERALL MEDIUM CONFIDENCE. RELIABLE INTENSITY AIDS ARE
ALSO, IN MODERATE AGREEMENT THROUGH TAU 120. SEVERAL JTWC RI AIDS
MEET CRITERIA, HEAVILY SIGNALING THE POSSIBILITY OF RI FOR THE NEXT
24 HOURS. UNCERTAINTY EMERGES REGARDING THE INTENSITY FOLLOWING RI
AND THE INTENSITY AS 30W CHANGES STEERING INFLUENCES, WITH A FEW
MODELS DEPICTING A SLIGHT WEAKENING AROUND TAU 60. FOLLOWING TAU
60, ALL MODELS GENERALLY AGREE ON A PERIOD OF STEADY
INTENSIFICATION THROUGH TAU 120. THE JTWC INTENSITY FORECAST IS
ASSESSED WITH OVERALL MEDIUM CONFIDENCE AND IS IN GOOD AGREEMENT
WITH HAFS-A, HWRF, COAMPS-TC, AND GOOGLE DEEPMIND.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: MEDIUM
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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