WDXS31 PGTW 112100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 04S (CHIDO) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.4S 56.7E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 583 NM NORTH OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: WESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 48 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL CYCLONE (TC) 04S (CHIDO) HAS UNDERGONE EXTREMELY RAPID
INTENSIFICATION OVER THE PAST DAY, INCREASING FROM 60 KNOTS TO 120
KNOTS IN JUST 24 HOURS. ANIMATED ENHANCED INFRARED (EIR) SATELLITE
IMAGERY DEPICTS A COMPACT SYSTEM, WITH A 6NM WIDE EYE, SURROUNDED
BY DEEP CONVECTION, PASSING OVER THE ISLAND OF VINGT CINQ AT 1800Z.
BETWEEN 1800Z-1900Z, EIR IMAGERY SUGGESTED AN EROSION OF THE EASTERN
EYEWALL, HOWEVER THE EIR UP TO 2000Z SHOWS THE CONVECTION REFORMING
UPSHEAR TO THE EAST AND REESTABLISHING THE EYEWALL ON THE
NORTHEASTERN SIDE. CLOUD TOP TEMPERATURES REMAIN RELATIVELY WARM AT
JUST -68C, AND THE EYE TEMPERATURE HAS RETURNED TO NEGATIVE
TERRITORY AFTER REACHING A MAXIMUM OF 15C AT 1600Z. A 111402Z SSMIS
91GHZ MICROWAVE IMAGE REVEALED A VERY COMPACT INNER CORE OF DEEP
CONVECTION FORMING A CONTINUOUS EYEWALL SURROUNDING A TINY,
VERTICALLY ALIGNED EYE FEATURE. HOWEVER, THE EYEWALL WAS THINNEST ON
THE EASTERN SIDE, CONSISTENT WITH THE MODERATE EASTERLY SHEAR STILL
IMPACTING THE SYSTEM. THE INITIAL POSITION WAS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE 6NM EYE FEATURE IN THE EIR NOTED ABOVE. THE
INITIAL INTENSITY WAS ASSESSED WITH MEDIUM CONFIDENCE, HEDGED
HIGHER THAN SUBJECTIVE AND OBJECTIVE INTENSITY ESTIMATES NOTED
ABOVE, IN LIGHT OF THE FACT THAT THE DVORAK-BASED TECHNIQUES ARE
LIKELY BIASED LOW DUE TO THE EXTREMELY SMALL EYE AND COMPACT NATURE
OF THE STORM AS A WHOLE. IN THE AGGREGATE, THE ENVIRONMENT REMAINS
FAVORABLE, WITH STRONG RADIAL OUTFLOW BEING HELPED BY A WEAK
OUTFLOW CHANNEL TO POLEWARD AND WARM SSTS. THE MAIN QUESTIONABLE
FACTOR IS THE EASTERLY SHEAR, WHICH IS STILL RUNNING IN THE
MODERATE RANGE, BUT SO FAR HAS NOT BEEN A HINDRANCE TO THE RAPID
INTENSIFICATION OF TC 04S.
INITIAL WIND RADII BASIS: PERSISTENCE
CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTH.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: T5.5 - 102 KTS
   KNES: T5.5 - 102 KTS
   DEMS: T5.5 - 102 KTS
   FMEE: T5.5 - 102 KTS
   FIMP: T6.0 - 115 KTS
   CIMSS SATCON: 102 KTS AT 111729Z
   CIMSS ADT: 97 KTS AT 111800Z
   CIMSS AIDT: 111 KTS AT 111700Z
   CIMSS D-MINT: 103 KTS AT 111405Z
   CIMSS D-PRINT: 108 KTS AT 111800Z
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: STRONG RADIAL
ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: WITH THE EXCEPTION OF THE CURRENT
INTENSITY EXCEEDING THE PREVIOUSLY EXPECTED INTENSITY BY 10 KNOTS,
THERE ARE NO SIGNIFICANT CHANGES TO THE FORECAST FROM THE PREVIOUS
WARNING.
FORECAST DISCUSSION: TC 04S WILL CONTINUE TO TRACK WESTWARD FOR THE
NEXT 12 TO 18 HOURS, ALONG THE NORTHERN SIDE OF THE LARGE STR TO
THE SOUTH. THE RIDGE CENTER IS FORECAST TO SLIDE EASTWARD DURING
THE SAME TIMEFRAME, SUCH THAT BY TAU 24, TC 04S WILL LIE ALONG THE
NORTHWESTERN SIDE OF THE STEERING RIDGE AND BEGIN TO TURN ONTO A
SOUTHWESTWARD TRACK. BY TAU 36, TC 04S WILL BE FIRMLY ENTRENCHED ON
A DIRECTLY SOUTHWESTWARD TRACK, AND IS EXPECTED TO CONTINUE ON
THIS TRAJECTORY THROUGH THE REMAINDER OF THE FORECAST PERIOD. THE
SYSTEM IS FORECASTED TO CLIP THE NORTHERN TIP OF MADAGASCAR AROUND
TAU 48 BEFORE MOVING CLOSE TO, OR DIRECTLY OVER, MAYOTTE IN THE
NORTHERN MOZAMBIQUE CHANNEL AROUND TAU 72. LANDFALL ALONG THE
NORTHEASTERN COAST OF MOZAMBIQUE IS ANTICIPATED AROUND TAU 96, MOST
LIKELY JUST NORTH OF NACALA. IN TERMS OF INTENSITY, THE SYSTEM
LIKELY PEAKED AROUND 111600Z BASED OFF THE RAW ADT VALUES EXCEEDING
T6.2 AND THE EYE REACHING ITS WARMEST POINT. HOWEVER, AS DISCUSSED
ABOVE, THE LATEST EIR IMAGERY SUGGESTS THE REFORMATION OF THE EYEWALL
AS DEEP CONVECTION IS DEVELOPING ON THE UPSHEAR SIDE OF THE EYE. SO
ANOTHER ROUND OF INTENSIFICATION MAY BE IN THE OFFING IN THE NEAR
TERM, WITH THE FORECAST CALLING FOR A PEAK OF 125 KNOTS WITHIN THE
NEXT 12 HOURS. THE SYSTEM WILL MAINTAIN PEAK INTENSITY FOR A PERIOD OF
TIME, THEN BEGIN TO SLOWLY WEAKEN AS IT APPROACHES THE NORTHERN TIP OF
MADAGASCAR AS IT WILL BE ENTERING RELATIVELY COOLER WATERS AND COULD
FACE AN EYEWALL REPLACEMENT CYCLE (EWRC). CLOSE PASSAGE TO MADAGASCAR
WILL INDUCE SOME DISRUPTION OF THE LOW-LEVEL INFLOW AND, ACCOMPANIED
BY AN EXPECTED INCREASE IN SHEAR VALUES, WILL RESULT IN A MORE RAPID
WEAKENING PHASE AFTER TAU 48. HOWEVER, THE SYSTEM IS EXPECTED TO
REMAIN A STRONG TROPICAL CYCLONE AS IT PASSES MAYOTTE. BY THE TIME
THE SYSTEM APPROACHES MOZAMBIQUE, IT WILL LIKELY STILL BE A
RELATIVELY STRONG TC, WITH AN INTENSITY BETWEEN 70-80 KNOTS. AFTER
LANDFALL, THE SYSTEM WILL RAPIDLY WEAKEN AND DISSIPATE BY TAU 120.
MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD AGREEMENT
THROUGH THE FORECAST PERIOD, WITH NAVGEM BEING THE ONLY OUTLIER
DEVIATING FROM THE TIGHT TRACK ENVELOPE AND TAKING THE SYSTEM
POLEWARD INTO THE MOZAMBIQUE CHANNEL. THE REMAINDER OF THE
CONSENSUS MEMBERS ARE CONFINED TO AN ENVELOPE OF 75NM AT TAU 48
(CPA TO MADAGASCAR), 95NM AT TAU 72 (CPA TO MAYOTTE) AND 155NM AT
TAU 96 (LANDFALL IN MOZAMBIQUE). THE ECMWF LIES ON THE NORTHERN
EDGE OF THE GUIDANCE ENVELOPE THROUGH THE ENTIRE FORECAST PERIOD,
WHILE THE GALWEM IS SITUATED ON THE SOUTHERN SIDE THROUGH THE
FORECAST. THE JTWC FORECAST TRACK IS CLOSE TO, BUT JUST NORTH OF,
THE MULTI-MODEL CONSENSUS WITH HIGH CONFIDENCE. LIMITED INTENSITY
GUIDANCE IS STRONGLY MIXED, WITH THE HAFS-A INDICATING NEAR-TERM
INTENSIFICATION TO 130 KNOTS, WHERE IT SITS UNTIL TAU 36, BEFORE
STEADY TO RAPID WEAKENING THROUGH THE REMAINDER OF THE FORECAST.
HWRF SHOWS THE OPPOSITE TREND, WEAKENING THE SYSTEM FROM THE
BEGINNING OF THE FORECAST ALL THE WAY TO THE END. THIS LEADS TO A
MAXIMUM SPREAD OF OVER 80 KNOTS AT TAU 72, THOUGH THE CONSENSUS
LIES AT THE HIGHER END OF THE GUIDANCE PACKAGE. THE JTWC FORECAST
IN GENERAL FOLLOWS THE CONSENSUS MEAN THROUGH THE FORECAST PERIOD,
BUT CONFIDENCE REMAINS LOW DUE TO THE EXTREMELY LARGE SPREAD IN THE
AVAILABLE GUIDANCE.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 0 - 72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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