WDXS31 PGTW 200300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 18S (EIGHTEEN) WARNING 
NR 030//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 17.8S 110.4E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 341 NM NORTHWEST OF LEARMONTH, AUSTRALIA
   MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS
REDEVELOPMENT OF WELL DEFINED SPIRAL BANDING WRAPPING INTO A
CONSOLIDATING MASS OF DEEP CONVECTION, WITH HOT TOWERS CONCENTRATING 
OVER THE SUSPECTED AREA OF THE LOW LEVEL CIRCULATION CENTER (LLCC). 
THE BYU HIGH RESOLUTION ENHANCEMENT OF THE 191426Z ASCAT-C PASS 
INDICATED 30 KT MAXIMUM WINDS, HOWEVER, THE WESTERN PERIPHERY WAS NOT 
COMPLETELY IN THE FOOTPRINT. A 191814Z AMSR2 37V PASS REVEALED A WELL 
DEFINED LOW LEVEL CENTER FEATURE, WITH GENERALLY SYMMETRIC BANDING. 
COMPARISON WITH THE 89 GHZ CHANNEL INDICATES THERE IS A NORTH-SOUTH 
TILT IN THE VORTEX, HOWEVER, THE DEGREE OF TILT HAS BEEN GRADUALLY 
DECREASING. COMBINED WITH THE IMPROVED CONVECTIVE CORE IN THE MSI, 
VERTICAL WIND SHEAR (VWS) IS ASSESSED TO BE DECREASING, OR TC 18S IS 
BEGINNING TO SUCCESSFULLY PUSH BACK AGAINST THE ENVIRONMENTAL SHEAR. A 
RARE SUBSEQUENT STRING OF GOOD-COVERAGE SSMIS AND COWVR PASSES 
PROVIDES A TIME SERIES OF DEVELOPMENT AND LENDS GOOD CONFIDENCE TO THE 
INITIAL POSITION. THE INITIAL INTENSITY WAS ASSESSED AT 35 KTS, BASED 
ON DVORAK T2.5 FINAL-T ESTIMATES FROM ALL REPORTING AGENCIES, AND IS
SUPPORTED BY CIMSS ADT, AIDT, AND DPRINT. POLEWARD OUTFLOW IS BEING
MODERATELY ENHANCED BY A JET TO THE SOUTHEAST, AND SSTS ARE A
FAVORABLE 27 TO 28 DEGREES CELSIUS. THE PRIMARY LIMITING FACTOR AT
THIS TIME IS THE LACK OF A SOURCE OF MID-LEVEL MOISTURE. GFS AND
ECMWF ANALYSES INDICATES TC 18S IS NEARLY SURROUNDED BY DRY AIR,
HOWEVER, A POCKET OF DEEP CENTRAL MOISTURE IS PREVENTING DRIER AIR
FROM PENETRATING THE CORE.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: MID-LEVEL SUB-TROPICAL RIDGE TO THE
SOUTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   APRF: T2.5 - 35 KTS
   CIMSS ADT: 35 KTS AT 200100Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: RESUMING JTWC WARNINGS BASED ON
ANALYSIS OF ALL AVAILABLE DATA INDICATING TC 18S HAS REACHED 35
KNOT WARNING CRITERIA.


FORECAST DISCUSSION: TC 18S IS FORECAST TO TRACK WESTWARD THROUGH
TAU 48 UNDER THE INFLUENCE OF THE STEERING RIDGE TO THE SOUTH.
INTENSIFICATION IS EXPECTED TO BE GRADUAL OVER THE FIRST 24 HOURS
AS THE VORTEX ALIGNMENT CONTINUES TO IMPROVE, AND PERSISTENT
CONVECTION ENHANCES THE MOISTURE IN THE IMMEDIATE VICINITY OF THE
LLCC, ALTHOUGH DRY AIR IS EXPECTED TO REMAIN ENTRENCHED AROUND THE
PERIPHERY. AFTER 24 HOURS, MODELS ARE INDICATING A PERIOD OF STRONG
DEEPENING, NEARING RAPID INTENSIFICATION PACE, AS VWS SHOULD REMAIN
FAVORABLE. PEAK INTENSITY WAS SET AT 75 KNOTS, WHICH HELD BELOW THE
AGGRESSIVE MESOSCALE MODELS, GIVEN THAT AVAILABLE MOISTURE SHOULD
REMAIN A LIMITING FACTOR. BEYOND TAU 48, THE TRACK WILL TRANSITION
TO SOUTHWESTWARD, AS A WEAKNESS DEVELOPS IN THE STR. AFTER TAU 72,
THE SYSTEM WILL BEGIN FEELING THE EFFECTS OF INCREASED VWS DUE TO
AN APPROACHING UPPER LEVEL JET. ADDITIONALLY, SSTS WILL DROP BELOW
26 DEGREES CELSIUS. VWS WILL CONTINUE TO INCREASE THROUGHOUT THE
REMAINDER OF THE FORECAST PERIOD. THE FIVE DAY FORECAST INTENSITY
IS SET AT 35 KTS, HOWEVER, DISSIPATION MAY OCCUR SOONER DUE TO THE
HIGHLY UNFAVORABLE ENVIRONMENT ANTICIPATED BY THAT TIME. 

MODEL DISCUSSION: MODEL GUIDANCE IS SOMEWHAT LIMITED FOR THIS FIRST
ROUND OF REGENERATED WARNINGS. HOWEVER, GFS, GEFS, AND HAFS ARE IN
TIGHT AGREEMENT, AND ALTHOUGH FASTER THAN THE ECWMF AND ITS
ENSEMBLE, THE TRACK PATTERNS ARE GENERALLY THE SAME. GIVEN THE
LIMITED MODELS, 0-72 HOUR TRACK CONFIDENCE IS ASSESSED AS MEDIUM,
AND THE EXTENDED TRACK CONFIDENCE IS SET TO LOW. THESE ASSESSMENTS 
SHOULD IMPROVE IF MODEL AGREEMENT CONTINUES TO BE OBSERVED. INTENSITY 
CONFIDENCE IS SET TO LOW, WHILE ASSESSING IF THIS CURRENT ROUND OF 
IMPROVEMENT CAN SUSTAIN ITSELF FOR MORE THAN 6 HOURS. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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