WDXS31 PGTW 011500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 09S (NINE) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.4S 66.3E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 520 NM EAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: NORTH-NORTHEASTWARD AT 04 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) SHOWS THE COLD DENSE
OVERCAST HAS SIGNIFICANTLY SHEARED FROM AND FULLY EXPOSED THE LOW
LEVEL CIRCULATION CENTER (LLCC) THAT CONTINUED TO TRACK
EQUATORWARD, EXACERBATING THE SEPARATION. THE INITIAL POSITION IS
PLACED WITH HIGH CONFIDENCE BASED ON THE EXPOSED LLCC IN THE MSI
LOOP AND THE 011136Z SSMIS IMAGE. THE INITIAL INTENSITY OF 35KTS IS 
PLACED WITH MEDIUM CONFIDENCE BASED ON A CLOSE RANGE OF AGENCY AND 
AUTOMATED DVORAK ESTIMATES. ANALYSIS INDICATES A MARGINAL ENVIRONMENT 
WITH WARM SST AND STRONG POLEWARD OUTFLOW OFFSET BY STRONG VERTICAL 
WIND SHEAR (VWS).

INITIAL WIND RADII BASIS: PERSISTENCE. 

CURRENT STEERING MECHANISM: COMPETING STEERING ENVIRONMENT WITH A
SUBTROPICAL RIDGE (STR) POSITIONED TO THE WEST AND A WEAK STEERING
RIDGE TO THE EAST.    

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.5 - 35 KTS
   CIMSS ADT: 29 KTS AT 011200Z
   CIMSS AIDT: 37 KTS AT 011200Z
   CIMSS DPRINT: 29 KTS AT 011300Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 25-30 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG 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 09S IS FORECAST TO RETURN TO A POLEWARD
TRAJECTORY AS THE STR TO THE EAST ASSUMES STEERING. THE MARGINALLY
FAVORABLE ENVIRONMENT WILL PROMOTE SLIGHT INTENSIFICATION TO 45KTS
BY TAU 36. CONCURRENTLY, THE SYSTEM WILL BEGIN SUBTROPICAL
TRANSITION AND BY TAU 48, WILL TRANSFORM INTO A SUBTROPICAL SYSTEM 
WITH AN EXPANDING WIND FIELD. THERE IS A DISTINCT POSSIBILITY THAT TC 
09S WILL DISSIPATE BEFORE SUBTROPICAL TRANSITION DUE TO INCREASING VWS 
AS IT TRACKS FURTHER POLEWARD AND DEEPER INTO THE PREVAILING STRONG 
WESTERLIES.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN TIGHT AGREEMENT WITH A
GRADUAL AND EVEN SPREAD TO A MERE 164NM BY TAU 48; HOWEVER, GIVEN
THE UNCERTAINTIES ASSOCIATED WITH SUBTROPICAL TRANSITION AND THE
POSSIBILITY OF AN EARLY DISSIPATION, THERE IS MEDIUM CONFIDENCE IN
THE TRACK FORECAST AND LOW CONFIDENCE IN THE INTENSITY FORECAST. 

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