WDXS31 PGTW 041500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 25S (TWENTYFIVE) 
WARNING NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.3S 110.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 697 NM NORTH-NORTHWEST OF LEARMONTH,
AUSTRALIA
   MOVEMENT PAST 6 HOURS: EAST-NORTHEASTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 25S WITH A FULLY EXPOSED, YET WELL-DEFINED LOW-LEVEL
CIRCULATION CENTER (LLCC). DEEP CONVECTION CONTINUES TO BE HEAVILY
SHEARED TO THE WEST. A 041035Z F17 SSMIS 91 GHZ MICROWAVE IMAGE
REVEALED THE COMPACT CORE WITH LOW-LEVEL CLOUDS TIGHTLY WRAPPING
INTO THE CENTER. THE INITIAL POSITION IS PLACED WITH HIGH
CONFIDENCE BASED ON THE EXPOSED LLCC IN ANIMATED EIR IMAGERY. THE
INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE AGENCY DVORAK FIXES AND CIMSS OBJECTIVE INTENSITY
ESTIMATES LISTED BELOW. A 041105Z RCM-2 SAR IMAGE SHOWED A VMAX OF
OVER 60 KTS WITHIN THE NORTHERN SEMICIRCLE, WHICH IS ANALYZED TO BE
ERRONEOUS BASED ON THE CURRENT STRUCTURE OF THE SYSTEM.
ENVIRONMENTAL ANALYSIS INDICATES THAT 25S IS IN A MARGINAL 
ENVIRONMENT CHARACTERIZED BY MODERATE POLEWARD OUTFLOW ALOFT, VERY 
HIGH (30-35 KTS) EASTERLY VERTICAL WIND SHEAR, AND WARM SEA SURFACE 
TEMPERATURES (29-30 C).

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: A NEAR-EQUATORIAL RIDGE (NER)
POSITIONED TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   APRF: T2.0 - 30 KTS
   CIMSS ADT: 35 KTS AT 041200Z
   CIMSS AIDT: 37 KTS AT 041200Z
   CIMSS D-MINT: 29 KTS AT 041035Z
   CIMSS D-PRINT: 31 KTS AT 041200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 30-35 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 25S IS FORECAST TO TRACK EASTWARD, ALONG
THE SOUTHERN PERIPHERY OF THE NER TO THE NORTH, THROUGH TAU 24.
NEAR TAU 24, INTERACTION WITH THE WIND FIELD OF A SEPARATE
DEVELOPING LOW PRESSURE AREA (93S) TO THE SOUTH WILL CAUSE 25S TO
TURN SOUTHEASTWARD. REGARDING INTENSITY, 25S IS FORECAST TO
MARGINALLY INTENSIFY OVER THE NEXT 24 HOURS AS STRONG EASTERLY
SHEAR CONTINUES TO IMPACT THE VORTEX, DISALLOWING FURTHER
INTENSIFICATION. AFTER TAU 24, THE SYSTEM WILL BEGIN WEAKENING AS
THE VORTEX SHALLOWS OUT WITH INCREASING DRY AIR ENTRAINMENT FROM
THE WEST AND EASTERLY SHEAR OF OVER 40 KTS. 25S IS EXPECTED TO
DISSIPATE AROUND TAU 48, NORTHWEST OF BROOME.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN MODERATE
AGREEMENT WITH A 180 NM CROSS-TRACK SPREAD AT TAU 48. THE JTWC
TRACK FORECAST IS PLACED CLOSE TO THE MULTI-MODEL CONSENSUS AND
ECMWF TRACKERS THROUGHOUT THE FORECAST PERIOD WITH MEDIUM
CONFIDENCE. INTENSITY GUIDANCE GENERALLY AGREES ON MARGINAL
INTENSIFICATION THROUGH TAU 12-24 FOLLOWED BY WEAKENING WITH NO
NOTABLE OUTLIERS. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE
CONSENSUS WITH MEDIUM CONFIDENCE. 


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