WDXS33 PGTW 252100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 23S (TWENTYTHREE) 
WARNING NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.7S 38.1E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 120 NM WEST-SOUTHWEST OF EUROPA ISLAND
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD
ROTATION SITUATED IN THE MOZAMBIQUE CHANNEL, WITH DEEP FLARING
CONVECTION POSITIONED IN AN ARC ACROSS THE NORTHERN SEMICIRLCE OF
THE CIRCULATION. A 251113Z GMI 37GHZ MICROWAVE IMAGE SHOWED
FRAGMENTED, FORMATIVE BANDING FEATURES WRAPPING INTO A WEAK LOW
LEVEL CIRCULATION CENTER (LLCC). THE PRIMARY BANDING FEATURES WERE
LOCATED APPROXIMATELY 65-110NM AWAY FROM THE CENTER, CONFIRMED THE
BROAD NATURE OF THE OVERALL CIRCULATION. THE INITIAL POSITION WAS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE MICROWAVE IMAGE NOTED
ABOVE. THE INITIAL INTENSITY IS ASSESSED WITH MEDIUM CONFIDENCE, ON
THE HIGHER END OF THE AVAILABLE AGENCY DVORAK CURRENT INTENSITY
ESTIMATES. THE ENVIRONMENT IS FAVORABLE FOR FURTHER DEVELOPMENT,
WITH WARM SSTS AND HIGH OHC, GOOD POLEWARD AND EQUATORWARD OUTFLOW
ALOFT AND LOW WIND SHEAR. THE ONLY HINDRANCE AT THE MOMENT IS THE
LARGE SIZE OF THE SYSTEM, WHICH WILL TAKE SOME TIME TO CONSOLIDATE.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: WEAK AND COMPETING STEERING ENVIRONMENT

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T1.0 - 25 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS D-PRINT: 37 KTS AT 251800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE POLEWARD AND EQUATORWARD
   OTHER FACTORS: LARGE SIZE OF THE ROTATION

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL CYCLONE 23S IS CURRENTLY ENSCONCED
IN A WEAK STEERING ENVIRONMENT WITH AN EXTENSION OF THE NEAR
EQUATORIAL RIDGE (NER) TO THE EAST AND ANOTHER WEAKER RIDGE OVER
THE AFRICAN CONTINENT. THE NERIS FORECAST TO BUILD SOUTHWARD OVER
MADAGASCAR AND SHIFT WESTWARD OVER THE NEXT 24 HOURS, WHICH WILL
KICK TC 23S OUT OF ITS WEAK STEERING PATTERN AND MOVE IT
SOUTHEASTWARD. THE SYSTEM WILL CONTINUE TRACK SOUTHEASTWARD THROUGH
ABOUT TAU 48, THEN SLAM ON THE BRAKES AS IT RUNS INTO THE WESTERN
SIDE OF A BUILDING SUBTROPICAL RIDGE (MASCARENE HIGH) FAR OUT IN
THE SOUTHERN INDIAN OCEAN (SIO). BETWEEN TAU 72 AND TAU 120, THE
SYSTEM IS EXPECTED TO MOVE VERY SLOWLY, GENERALLY TOWARDS THE
SOUTHEAST, TRAPPED IN ANOTHER WEAK STEERING PATTERN, WITH THE
STRONG RIDGE OVER THE SIO AND A BUILDING RIDGE OVER THE AFRICAN
CONTINENT. THE FORECAST TRACK IS HIGHLY UNCERTAIN DURING THIS TIME,
WITH BOTH THE DETERMINISTIC AND ENSEMBLE MODELS DEPICTING A WIDE
DISPERSAL OF POTENTIAL TRACK OUTCOMES INCLUDING THE POSSIBILITY OF
A TURN NORTHWARD INTO SOUTHERN MADAGASCAR. REGARDLESS THE SYSTEM
WILL NOT BE MOVING MUCH BY THIS POINT, UNTIL THE STR TO THE BEGINS
TO BUILD ONCE MORE BY THE END OF THE FORECAST PERIOD. IN TERMS OF
INTENSITY, THE SYSTEM WILL SLOWLY INTENSIFY OVER THE FIRST 24 HOURS
OF THE FORECAST AS IT CONTINUES TO CONSOLIDATE AND SHRINK IN SIZE.
MORE RAPID INTENSIFICATION IS EXPECTED AFTER TAU 24, WITH THE
SYSTEM REACHING PEAK INTENSITY OF 70 KNOTS BY TAU 48. THEREAFTER,
THE SYSTEM INTERACTS WITH THE SOUTHERN PORTION OF MADAGASCAR AND
FEELS THE EFFECTS OF INCREASING SHEAR, AND WILL WEAKEN STEADILY
THROUGH THE REMAINDER OF THE FORECAST

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD AGREEMENT
THROUGH ABOUT TAU 48, WITH LESS THAN 100NM SPREAD ACROSS THE
GUIDANCE PACKAGE. THEREAFTER, THE MODELS SPREAD OUT LIKE A
STAR-SHELL FIREWORK DISPLAY, RAPIDLY DIVERGING ACROSS ALL POINTS OF
THE COMPASS, WIDENING THE SPREAD TO OVER 400NM BY THE END OF THE
FORECAST PERIOD. THE JTWC FORECAST IS PLACED CLOSEST TO THE ECMWF
TRACK SOLUTION AND JUST SOUTH AND WEST OF THE CONSENSUS MEAN.
CONFIDENCE IS HIGH THROUGH TAU 48 BUT DRIVES SHARPLY LOWER
THEREAFTER. INTENSITY GUIDANCE IS ALSO IN GOOD AGREEMENT THAT THE
SYSTEM WILL STEADILY INTENSIFY TO ABOUT TAU 48 THOUGH THE BULK OF
THE AVAILABLE GUIDANCE PEAKS THE SYSTEM ABOUT 10-15 KNOTS LOWER
THAN THE JTWC FORECAST. 

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