WDXS31 PGTW 120900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHIDO) WARNING NR 
006//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.6S 54.5E
   INITIAL INTENSITY: 135 KTS
   GEOGRAPHIC REFERENCE: 593 NM NORTH-NORTHWEST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 57 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 04S (CHIDO) HAS BEEN OBSERVED TO UNDERGO
EXTREME RAPID INTENSIFICATION OVER THE PREVIOUS 24 HOURS,
INCREASING FROM AN INTENSITY OF 75 KTS TO 135 KTS OVER THE LAST
DAY. ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
IMPRESSIVE CYCLONE, WITH A 12 NM WIDE EYE-FEATURE, SURROUNDED BY
CONTINUOUS DEEP CONVECTION WRAPPING VERY TIGHTLY AROUND THE
LOW-LEVEL CIRCULATION CENTER (LLCC). EIR IMAGERY HAS CONTINUED TO
SHOW A VERY SYMMETRIC AND MODERATELY SIZED TC, WITH MINIMAL
CONVECTIVE BANDS OUTSIDE OF THE TIGHTLY WRAPPED STRUCTURE. ON
ANIMATED WATER VAPOR (WV) IMAGERY, STRONG RADIAL OUTFLOW ALOFT HAS 
BEEN OBSERVED OVER THE LAST 12 HOURS, CHARACTERIZED BY VISIBLE 
CIRRIFORM STRIATIONS BURSTING OUTWARD FROM THE IMMEDIATE CENTER. WITH 
REGARD TO THE ENVIRONMENT, VERTICAL WIND SHEAR (VWS) HAS REMAINED LOW 
(10-15 KTS) OVER THE PREVIOUS SIX HOURS, WHILE SEA SURFACE 
TEMPERATURES (SST) MAINTAIN A SUPPORTIVE 27-28 C. THE INITIAL 
POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON THE WELL-DEFINED AND 
OBSERVABLE EYE-FEATURE ON ANIMATED EIR IMAGERY. THE INITIAL INTENSITY 
IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON SUBJECTIVE AGENCY 
ESTIMATES RANGING BETWEEN 127 KTS AND 140 KTS, WHILE CIMSS OBJECTIVE 
ESTIMATES HAVE SHOWN A CEILING OF 136 KTS AT 120600Z.

INITIAL WIND RADII BASIS: SAR DATA 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   KNES: T6.5 - 127 KTS
   DEMS: T6.5 - 127 KTS
   FIMP: T6.5 - 127 KTS
   CIMSS SATCON: 131 KTS AT 120530Z
   CIMSS ADT: 127 KTS AT 120600Z
   CIMSS AIDT: 136 KTS AT 120600Z
   CIMSS D-MINT: 112 KTS AT 120316Z
   CIMSS D-PRINT: 110 KTS AT 120600Z

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

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: CURRENT INTENSITY EXCEEDS PREVIOUSLY
EXPECTED INTENSITY BY 10 KTS. THERE ARE NO OTHER SIGNIFICANT
CHANGES FROM THE PREVIOUS FORECAST.

FORECAST DISCUSSION: TC 04S IS FORECASTED TO CONTINUE TRACKING
GENERALLY WEST-SOUTHWESTWARD ALONG THE NORTHWESTERN PERIPHERY OF A
SUBTROPICAL RIDGE LOCATED DIRECTLY TO THE SOUTH. BETWEEN TAU 24 AND
TAU 36, CHIDO IS EXPECTED TO MOVE JUST NORTH OF THE NORTHERN MOST
TIP OF MADAGASCAR. FOLLOWING TAU 36, THE TC WILL CONTINUE
WEST-SOUTHWESTWARD, ALONG THE WESTWARD EXTENT OF THE AFOREMENTIONED
RIDGE BUILDING INTO SOUTHERN MOZAMBIQUE. AFTER TAU 48, TC CHIDO
WILL MOVE ANTICYCLONICALLY TOWARD THE SUBTROPICAL RIDGE AXIS,
MAKING LANDFALL JUST AFTER TAU 72 AND NORTH OF NACALA, MOZAMBIQUE.
BETWEEN TAU 72 AND TAU 96, TC 04S IS EXPECTED TO DISSIPATE AS THE
SYSTEM MOVES INLAND. WITH REGARD TO INTENSITY, THE SYSTEM IS
EXPECTED TO HAVE REACHED MAXIMUM INTENSITY OVER THE LAST FEW HOURS,
WITH ITS INITIAL WEAKENING PHASE BEGINNING IMMINENTLY. WITH THAT
BEING SAID, THE TC 04S IS FORECASTED TO ENCOUNTER AN INCREASE IN
VWS INTO TAU 48 (20-25 KTS FROM THE EAST), ERODING THE SYSTEM TO 95
KTS DURING ITS WEST-SOUTHWESTWARD TRACK WEST OF NORTHERN
MADAGASCAR. ALTHOUGH VWS WILL INITIALLY WEAKEN THE SYSTEM, TC CHIDO
IS EXPECTED TO MAINTAIN A RELATIVELY HIGH INTENSITY OF 60 KTS JUST
BEFORE MAKING LANDFALL AFTER TAU 72. AFTER LANDFALL, THE OVERALL
INTENSITY WILL WEAKEN TO 30 KTS BY TAU 96 DUE TO INTERACTION WITH
THE LOCAL TERRAIN.

MODEL DISCUSSION: NUMERICAL MODEL GUIDANCE REMAINS IN RELATIVELY
GOOD AGREEMENT FOR THE TRACK OF TC 04S, WITH A CROSS-TRACK SPREAD
OF 167 NM BY TAU 72. FOLLOWING TAU 72, TRACK SOLUTIONS BEGIN TO
DIVERGE AFTER LANDFALL AND AROUND THE SUBTROPICAL RIDGE AXIS
THROUGH DISSIPATION. THE JTWC FORECAST TRACK HAS REMAINED STEADY
AND ALIGNED VERY CLOSELY WITH THE MULTI-MODEL CONSENSUS, LENDING
HIGH TRACK CONFIDENCE OVER THE NEXT 72 HOURS. FOLLOWING LANDFALL,
CONFIDENCE DECREASES DUE TO DISSIPATION OVER THE RUGGED TERRAIN OF
MOZAMBIQUE. IN REGARD TO INTENSITY, THE MULTI-MODEL INTENSITY
CONSENSUS IS IN AGREEMENT THAT STEADY WEAKENING IS EXPECTED FROM
THE MOST RECENT ANALYSIS (120600Z) THROUGH THE END OF THE FORECAST
PERIOD, WITH GFS INDICATING A MUCH QUICKER DROP-OFF IN SURFACE
INTENSITIES AND BEING THE MOST SIGNIFICANT OUTLIER. OVERALL, THE
JTWC INTENSITY FORECAST REMAINS CLOSE TO THE NUMERICAL MODEL 
INTENSITY CONSENSUS, LENDING MEDIUM CONFIDENCE TO THE INTENSITY 
FORECAST.

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