WDXS31 PGTW 120900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 17S (FILIPO)
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.5S 34.9E
   INITIAL INTENSITY: 50 KTS
   GEOGRAPHIC REFERENCE: 298 NM WEST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 17S (FILIPO) MAKING LANDFALL APPROXIMATELY 50NM SOUTH OF 
BEIRA, MOZAMBIQUE BETWEEN 120000Z AND 120600Z. TC 17S HAS AN OBSCURED 
LOW-LEVEL CIRCULATION WITH PERSISTENT CONVECTION OVER THE CENTER AND 
WELL-DEFINED CONVECTIVE BANDING, ESPECIALLY IN THE SOUTHERN 
PERIPHERY. UPPER-LEVEL ANALYSIS INDICATES THAT 17S IS IN A FAVORABLE 
ENVIRONMENT WITH ROBUST POLEWARD OUTFLOW ALOFT, DUE TO THE MID-
LATITUDE JET MAX SOUTH OF THE LLCC, LOW TO MODERATE (10-15 KTS) 
VERTICAL WIND SHEAR, AND HIGH (70-90 PCT) RELATIVE HUMIDITY VALUES. 
THE INITIAL POSITION IS PLACED WITH LOW CONFIDENCE BASED ON
ANIMATED MSI AND A METEOSAT-9 VISIBLE IMAGE OF 120600Z. THE INITIAL
INTENSITY OF 50 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON
PERSISTENCE OF THE SUBJECTIVE INTENSITY ESTIMATES PRIOR TO
LANDFALL AND THE OBJECTIVE ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE SOUTH
AND EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   DEMS: T3.5 - 55 KTS
   CIMSS DPRINT: 47 KTS AT 120600Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 17S IS CURRENTLY TRACKING SOUTHWESTWARD
ALONG THE WESTERN AND NORTHERN PERIPHERY OF A SUBTROPICAL RIDGE. TC
17S IS FORECAST TO CONTINUE A SOUTHWARD TRACK THROUGH TAU 24
WHEN IT BEGINS TO TRACK SOUTHEASTWARD DUE TO THE PROPAGATION OF
THE STR TO THE EAST. AFTER TAU 24 THE SYSTEM WILL INCREASE TRACK
SPEED AS IT STARTS ITS TRANSITION INTO THE BAROCLINIC ZONE AND
INTERACTS WITH THE UPPER-LEVEL JET TO ITS SOUTH. TC 17S IS
FORECASTED TO WEAKEN TO 45 KTS DUE TO LAND INTERACTION OVER THE
NEXT 12-24 HOURS. AFTER TAU 24, THE SYSTEM IS ANTICIPATED TO 
EXPERIENCE A SIGNIFICANT INCREASE IN DIVERGENCE ALOFT AS IT TRACKS 
TOWARD A JET MAXIMA TO THE SOUTH, ALLOWING FOR A SHORT PERIOD OF 
INTENSIFICATION TO OCCUR TO TAU 48. AFTER TAU 48, TC 17S IS 
FORECASTED TO BEGIN A WEAKENING TREND AS VERTICAL WIND SHEAR 
INCREASES TO HIGH (ABOVE 30 KTS) LEVELS AND THE SST BEGINS TO COOL. 
DUE TO INTERACTION WITH THE JET MAXIMA TO THE SOUTH AND A SHORTWAVE 
MID-LATITUDE TROUGH, SUBTROPICAL TRANSITION IS EXPECTED TO BEGIN NEAR 
140000Z. THE SYSTEM IS FORECAST TO BEGIN EXTRATROPICAL TRANSITION 
NEAR 150600Z, COMPLETING EXTRATROPICAL TRANSITION BY 160600Z.

MODEL DISCUSSION: GLOBAL NUMERICAL MODEL GUIDANCE IS IN EXCEPTIONAL
AGREEMENT THROUGHOUT THE FORECAST PERIOD WITH A CROSS-TRACK SPREAD
OF 155 NM AT TAU 72 AND DIVERGING ONLY SLIGHTLY AFTERWARDS. ALONG-
TRACK SPREAD IS SLIGHTLY HIGHER AT 250 NM AT TAU 72. INTENSITY 
GUIDANCE IS IN FAIR AGREEMENT AS INDICATED BY A RISE OF INTENSITY 
FROM TAU 12 TO TAU 48 WITH AN INTENSITY SPREAD OF 25 KTS BETWEEN GFS 
ON THE LOW END AND COAMPS-TC (NAVGEM BASED) ON THE HIGH END NEAR TAU 
48, TIGHTENING THEREAFTER TO TAU 96. 

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72 - 96 HR: MEDIUM
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72 - 96 HR: MEDIUM//
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