WDXS31 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 08S (EIGHT) WARNING NR 
001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.1S 58.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 362 NM NORTH OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 20 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS CURVED
BANDS OF DEEP CONVECTION WITH A MAJORITY OF THE VERTICAL HOT TOWERS
PERSISTING IN THE SOUTHERN SEMICIRCLE. A 171612Z AMSU-B 89GHZ
MICROWAVE IMAGE REVEALS PROMINENT LOW LEVEL CLOUD LINES WRAPPING
INTO A LOW LEVEL CIRCULATION TUCKED UNDER AND THEREFOR OBSCURED BY
THE PRIMARY DEEP CONVECTIVE TOWERS. A 171356Z SMAP MICROWAVE
RADIOMETER PASS REVEALED A REGION OF 35-37 KNOT WINDS, WHICH
ROUGHLY CORRELATE TO THE PRIMARY REGION OF DEEP CONVECTION. THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON EIR AND
AMSU-B IMAGERY. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH
MEDIUM CONFIDENCE BASED ON EARLIER RADIOMETER DATA INDICATING 35-37
KNOTS AND PGTW DVORAK INTENSITY ESTIMATES SLIGHTLY LAGGED BEHIND
SHOWING T2.0. THE AFOREMENTIONED CONVECTIVE FEATURE TO THE SOUTH,
IF PERSISTENT, COULD INDICATE A BANDING FEATURE THAT WOULD MOVE THE
PGTW DVORAK INTENSITY ESTIMATE NORTH OF T2.0.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE
SOUTH-SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   FMEE: T2.0 - 30 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: BINARY INTERACTION WITH INVEST 90S

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.

FORECAST DISCUSSION: TC 08S IS FORECAST TO CONTINUE TRACKING
GENERALLY WESTWARD UNDER THE STEERING INFLUENCE OF A STR TO THE
SOUTH-SOUTHEAST. CURRENTLY IN A HIGHLY FAVORABLE ENVIRONMENT
CHARACTERIZED BY WARM SEA SURFACE TEMPERATURES, LOW VERTICAL WIND
SHEAR AND SOLID POLEWARD OUTFLOW ALOFT PROVIDED BY AN UPPER-LEVEL
ANTICYCLONE TO THE EAST, THE PROBABILITY OF RAPID INTENSIFICATION
IN THE COMING HOURS IS HIGH. OVER THE NEXT 12 HOURS AS 08S
CONTINUES TO TRACK WESTWARD AND INTENSIFY, INVEST 90S WILL CLOSE
WITHIN 400NM AND BEGIN TO ORBIT AND EVENTUALLY FULLY MERGE WITH
08S. BY TAU 24, 08S IS FORECAST TO REACH A PEAK INTENSITY NEAR
60KTS THOUGH HIGHER VALUES ARE POSSIBLE IF HIGHLY FAVORABLE
CONDITIONS PERSIST. AFTER TAU 24, THE SYSTEM WILL TRACK
WEST-SOUTHWESTWARD AND EVENTUALLY SOUTHWESTWARD TOWARDS A COL
REGION AS THE STEERING RIDGE REORIENTS LONGITUDINALLY. NEAR TAU 36,
08S WILL MAKE LANDFALL OVER THE MOUNTAINOUS REGION OF NORTHERN
MADAGASCAR. BASED ON THE FORECAST STEERING PATTERN THE SYSTEM WILL
BE FORCED INLAND AND RIPPED APART UNTIL DISSIPATION NEAR TAU 72.
THERE IS A POTENTIAL HOWEVER, THAT THE STEERING RIDGE WILL BE
BROKEN DOWN AND REORIENTED SOONER THAN FORECAST WHICH WOULD ALLOW
FOR A POLEWARD TRACK ALONG THE EASTERN COAST OF MADAGASCAR OVER THE
WARM WATERS OF THE SOUTHERN IO ALLOWING FOR A LONGER LIFE CYCLE.

MODEL DISCUSSION: WITH THE EXCEPTION OF NAVGEM, NUMERICAL MODEL
GUIDANCE IS IN GOOD AGREEMENT THROUGH TAU 36 WITH ALL MEMBERS
TRACKING INLAND, CONSISTENT WITH THE JTWC FORECAST TRACK. AFTER
MAKING LANDFALL, INDIVIDUAL MEMBERS STRUGGLE TO RESOLVE THE
TOPOGRAPHICAL IMPACTS RESULTING IN A SPREADING OF SOLUTIONS THROUGH
THE FORECAST PERIOD. FOR THIS REASON THE JTWC TRACK FORECAST IS
PLACED WITH MEDIUM CONFIDENCE. RELIABLE MODEL INTENSITY GUIDANCE IS
IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD WITH ALL MEMBERS
INDICATING A SHARP INTENSIFICATION TREND THROUGH TAU 24, AFTER
WHICH AN EQUALLY SHARP WEAKENING TREND AS THE SYSTEM MAKES
LANDFALL, AFTER WHICH STEADY WEAKENING UNTIL DISSIPATION. THE JTWC
INTENSITY GUIDANCE IS THEREFOR PLACED WITH HIGH CONFIDENCE.

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