WDXS31 PGTW 122100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHIDO) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.9S 52.2E
   INITIAL INTENSITY: 125 KTS
   GEOGRAPHIC REFERENCE: 552 NM NORTH-NORTHEAST OF ANTANANARIVO,
MADAGASCAR
   MOVEMENT PAST 6 HOURS: WESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 51 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 04S (CHIDO) CONTINUES TO OUTPERFORM ALL
EXPECTATIONS, REACHING AT LEAST 135 KNOTS DURING THE OVERNIGHT
HOURS (ZULU). ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY
SHOWS THAT THE SYSTEM IS QUALITATIVELY LESS IMPRESSIVE THAN IT WAS
SIX HOURS AGO WHEN IT STILL HAD A 12NM STADIUM EYE AND EYE
TEMPERATURES OVER 22C. OVER THE PAST FEW HOURS, THE EYE HAS BECOME
CLOUD-FILLED AND IS INCREASINGLY RAGGED IN NATURE. THE CDO IS ALSO
LESS EXPANSIVE THAN IT WAS EARLIER, PARTICULARLY ON THE EASTERN
SIDE AS CONVECTION HAS WANED IN THAT PORTION OF THE SYSTEM,
ALLOWING THE PERSISTENT MODERATE EASTERLY SHEAR TO PENETRATE
FURTHER IN TOWARD THE CORE. OVERALL, THIS PATTERN IS EERILY
SIMILAR TO 24 HOURS AGO AT THIS TIME, AND SIMILAR TO 24 HOURS AGO,
DEEP CONVECTION IS STARTING TO FIRE UP ALONG THE NORTHERN SIDE OF
THE CIRCULATION AND WRAP UPSHEAR, WHICH COULD MEAN THE SYSTEM IS
ABOUT TO MAKE ANOTHER COMEBACK. A 121748Z AMSU-B 89GHZ IMAGE
REVEALS A VERY COMPACT SYSTEM WITH A SYMMETRICAL INNER CORE AND
LIMITED BANDING FEATURES, PRIMARILY IN THE NORTHERN PORTION OF THE
CIRCULATION. IN MANY WAYS THE SYSTEM HAS AN ANNULAR APPEARANCE,
PARTICULARLY OVER THE PREVIOUS SIX HOURS. THE INITIAL POSITION WAS
ASSESSED WITH HIGH CONFIDENCE BASED ON A 10NM EYE IN THE EIR AND
EXTRAPOLATION OF THE CENTER SEEN IN A 121458Z RCM-3 SAR PASS. THE
INITIAL INTENSITY IS ASSESSED WITH HIGH CONFIDENCE, DOWN ABOUT 10
KNOTS FROM THE OVERNIGHT PEAK, BASED ON THE GENERALLY FALLING DVORAK
FINAL-T NUMBERS FROM ALL AGENCIES (BETWEEN T5.5 TO T6.5), THE
OBJECTIVE ESTIMATES NOTED ABOVE, AND ANALYSIS OF THE SAR WIND SPEED
DATA FROM THE RCM-3 PASS, WHICH SHOWED A VMAX OF 125 KNOTS. THE
ENVIRONMENT REMAINS OVERALL FAVORABLE, WITH NO MAJOR CHANGES IN THE
LAST 24 HOURS. SHEAR REMAINS MODERATE FROM THE EAST BUT APPEARS TO
BE HAVING LITTLE EFFECT ON THE SYSTEM. SSTS REMAIN WARM, AND RADIAL
OUTFLOW, WHILE STRONG, IS CONSTRAINED TO A VERY LOCALIZED REGION
NEAR THE CENTER OF THE SYSTEM.

INITIAL WIND RADII BASIS: SAR DATA 

CURRENT STEERING MECHANISM: NORTHWESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTHEAST OF MAURITIUS. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T7.0 - 140 KTS 
   KNES: T6.5 - 127 KTS
   FMEE: T6.5 - 127 KTS
   CIMSS SATCON: 126 KTS AT 121532Z
   CIMSS ADT: 124 KTS AT 121800Z
   CIMSS AIDT: 127 KTS AT 121800Z
   CIMSS D-PRINT: 108 KTS AT 121800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG RADIAL

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST TRACK FROM THE PREVIOUS WARNING. HOWEVER, THE
INTENSITY OF THE SYSTEM WHEN IT IS IN THE MOZAMBIQUE CHANNEL HAS
BEEN INCREASED SIGNIFICANTLY. 

FORECAST DISCUSSION: TC 04S WILL CONTINUE TO TRACK JUST SLIGHTLY
SOUTH OF DUE WEST FOR THE NEXT 12 HOURS, ALONG THE NORTHWESTERN
SIDE OF THE STEERING RIDGE CENTERED SOUTH OF THE MASCARENE ISLANDS.
THE CENTER OF THE STR IS EXPECTED TO SHIFT A BIT WESTWARD OVER THE
NEXT 24 HOURS, BUT THIS WILL HAVE LITTLE EFFECT ON THE TRACK, OTHER
THAN TO SPEED UP THE TRACK SPEED SLIGHTLY AFTER THE SYSTEM PASSES
MADAGASCAR. OTHERWISE, THE FORECAST CALLS FOR A STRAIGHT
SOUTHWESTWARD TRACK FROM TAU 24 ONWARD. THE SYSTEM IS EXPECTED TO
SKIRT THE NORTHERN TIP OF MADAGASCAR IN THE NEXT 18 TO 24 HOURS BUT
THE INNER CORE SHOULD REMAIN FAR ENOUGH OFFSHORE TO LIMIT THE
IMPACTS TO JUST THE EXTREME NORTHERN TIP OF THE ISLAND. BETWEEN
TAU 36 AND TAU 48, THE SYSTEM WILL PASS CLOSE TO THE ISLANDS OF
MAYOTTE AND THE SOUTHERN ISLANDS OF THE COMOROS GROUP BEFORE
SETTING OUT ACROSS THE MOZAMBIQUE CHANNEL. LANDFALL IN NORTHEASTERN
MOZAMBIQUE, NORTH OF NACALA, IS EXPECTED AROUND TAU 60. THE LATEST
EIR IMAGERY SUGGESTS THE SYSTEM IS ALREADY STARTING ANOTHER ROUND
OF UPSHEAR CONVECTIVE DEVELOPMENT AND IS REESTABLISHING A PINHOLE
EYE. THUS, EVEN THOUGH SHEAR IS EXPECTED TO REMAIN ELEVATED, THE
SYSTEM WILL MAINTAIN ITS CURRENT INTENSITY, OR COULD EVEN INTENSIFY
A FEW KNOTS IN THE NEXT 12 HOURS OR SO. AS IT PASSES MADAGASCAR, IT
IS EXPECTED TO WEAKEN SLIGHTLY, PRIMARILY DUE TO A POSSIBLE EYEWALL
REPLACEMENT CYCLE (EWRC), AS DEPICTED IN THE HAFS-A RUN AND THE
CIMSS M-PERC PRODUCT, AND DISRUPTION OF THE LOW-LEVEL INFLOW BY THE
TERRAIN OF NORTHERN MADAGASCAR. AFTER MOVING FURTHER AWAY FROM
MADAGASCAR, THE SYSTEM WILL BASICALLY FLATLINE, OR ONLY VERY SLOWLY
WEAKEN AS IT RECOVERS FROM THE DISRUPTION OF THE EWRC AND LAND
INTERACTION. THERE IS ALSO THE POSSIBILITY, LOW AT THE MOMENT, OF
INTENSIFICATION IN THE CHANNEL, AS THE GFS DEPICTS DEVELOPMENT OF A
POLEWARD OUTFLOW CHANNEL AS THE SYSTEM PASSES BY MAYOTTE. IF THIS
DEVELOPS, THE SYSTEM COULD VERY WELL INTENSIFY ONCE MORE.
REGARDLESS, TC 04S IS EXPECTED TO REMAIN A VERY STRONG TC AS IT
APPROACHES LANDFALL IN MOZAMBIQUE. ONCE THE SYSTEM MAKES LANDFALL,
IT IS FORECAST TO RAPIDLY WEAKEN OVER LAND, DISSIPATING BY TAU 96. 

MODEL DISCUSSION: DETERMINISTIC AND ENSEMBLE TRACK GUIDANCE IS IN
VERY TIGHT AGREEMENT, AT LEAST THROUGH TAU 72. CROSS-TRACK SPREAD
AT TAU 48 IS JUST 60NM, OPENING TO 120NM AT THE LANDFALL TIME.
HOWEVER, BY LANDFALL, THE BULK OF THE GUIDANCE (EXCEPT NAVGEM AND
GALWEM) ACTUALLY LIES IN A VERY TIGHT ENVELOPE OF JUST 45NM. THE
JTWC FORECAST LIES ALONG THE CONSENSUS MEAN TO TAU 48, THEN RESIDES
IN THE CENTER OF THE TIGHTER GROUPING OF MODELS OUTLINED ABOVE
THROUGH THE REMAINDER OF THE FORECAST. INTENSITY GUIDANCE REMAINS
MIXED, WITH THE HAFS-A AND COAMPS-TC VERY CLOSELY FOLLOWING ONE
ANOTHER SHOWING A STEADY INTENSITY FOR 12 HOURS, THEN A SHARPER
DROP-OFF TO TAU 24, THEN SLOW WEAKENING TO LANDFALL. MEANWHILE THE
HWRF DROPS THE SYSTEM DOWN TO 65 KNOTS WITHIN 36 HOURS AND THEN
DISSIPATES IT WITHIN 72 HOURS. THE JTWC FORECAST DEVIATES ABOUT 10
KNOTS HIGHER THAN THE MODEL GUIDANCE AFTER LANDFALL, BUT OTHERWISE
SITS VERY CLOSE TO THE HAFS-A AND COAMPS-TC. 

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