WDXS31 PGTW 240900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (HORACIO) WARNING 
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.5S 64.3E
   INITIAL INTENSITY: 120 KTS
   GEOGRAPHIC REFERENCE: 417 NM EAST-SOUTHEAST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 38 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 22S (HORACIO) RAPIDLY WEAKENING AS IT IS ROUNDING THE
AXIS OF A STR CENTERED TO THE EAST. ENVIRONMENTAL CONDITIONS HAVE
SWIFTLY SHIFTED TOWARDS UNFAVORABLE OVER THE LAST FEW HOURS, PRIMARILY 
DRIVEN BY SIGNIFICANT DRY MID-LEVEL AIR AND INCREASING VERTICAL WIND 
SHEAR (VWS), CURRENTLY ANALYZED AS LOW TO MODERATE (15-20 KTS). OTHER 
PARAMETERS ARE OPPOSING THE OTHERWISE HOSTILE ENVIRONMENT - SEA 
SURFACE TEMPERATURES (SST) REMAIN FAVORABLE AND WARM (27-28 C), WHILE 
THE POLEWARD OUTFLOW IS STRONG. THE INITIAL POSITION IS PLACED WITH 
HIGH CONFIDENCE BASED ON FILLING, BUT STILL EASILY IDENTIFIABLE, EYE 
FEATURE PRESENT IN THE VISIBLE SATELLITE IMAGERY. THE INITIAL 
INTENSITY OF 120 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON 
SIGNIFICANTLY REDUCED AREA OF DEEP CONVECTION, COOLING EYE 
TEMPERATURE, ANALYZED AT 7C, AND DVORAK FIXES AND OBJECTIVE ESTIMATES 
LISTED BELOW.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) CENTERED TO THE
EAST


AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T6.5 - 127 KTS
   DEMS: T6.5 - 127 KTS
   FMEE: T6.0 - 115 KTS
   FIMP: T5.5 - 102 KTS
   CIMSS ADT: 112 KTS AT 240600Z
   CIMSS AIDT: 117 KTS AT 240500Z
   CIMSS D-PRINT: 117 KTS AT 240600Z

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

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TC 22S IS FORECAST TO BEGIN TURNING AND 
TRANSITING POLEWARD AND EASTWARD UNDER THE INFLUENCE OF A STR TO THE 
EAST. INCREASING DRY AIR INTRUSION COMBINED WITH RAPIDLY AND 
DRASTICALLY INCREASING VWS ARE EXPECTED TO DEGRADE THE VERTICAL 
STRUCTURE OF THE VORTEX AND RESULT IN RAPID WEAKENING TREND OVER THE 
NEXT 48 HOURS, AS INDICATED BY ALL NUMERICAL MODELS. AT THAT TIME THE
SYSTEM WILL BECOME SHALLOW AND IS EXPECTED TO SLOW DOWN AND TURN
WEST-SOUTHWESTWARD IN RESPONSE TO A BUILDING LONG-WAVE RIDGE, WHILE
STILL WEAKENING. COOLING SSTS (EXPECTED TO DROP TO 24-25 C JUST PRIOR 
TO TAU 48) AND VWS APPROACHING 50 KTS WILL RESULT IN FURTHER 
WEAKENING. AT TAU 72, THE VORTEX WILL BEGIN TO INTERACT WITH A PASSING 
UPPER-LEVEL TROUGH, THE SSTS WILL DROP TO 22-23 C AND SUFFICIENT 
BAROCLINIC FORCING WILL RESULT IN THE SYSTEM BEGINNING ITS 
EXTRATROPICAL TRANSITION (ETT), WHICH IS EXPECTED TO BE COMPLETE BY 
TAU 96.

MODEL DISCUSSION: NUMERICAL TRACK MODEL GUIDANCE IS IN GOOD AGREEMENT 
THOUGH TAU 24, WITH SLIGHT INCREASE IN THE CROSS-TRACK ENVELOPE (120-
130 NM) SHORTLY THEREAFTER. NEARLY ALL MODELS INDICATE A BRIEF SLOW 
DOWN WHILE THE SYSTEM DRIFTS SOUTHWESTWARD, FOLLOWED BY A SOUTH-
SOUTHEASTWARD TURN AROUND TAU 72. THEREFORE, THE LONG-TERM TRACK 
CONFIDENCE IS ASSESSED WITH MEDIUM CONFIDENCE, WHILE THE PREDICTION IS 
OF HIGH CONFIDENCE IN THE SHORT TERM. IN REGARD TO INTENSITY, ALL 
AVAILABLE GUIDANCE IS SIGNALING RAPID WEAKENING, WITH MAJORITY OF THE 
MODELS DROPPING THE PEAK WIND SPEED VALUES TO 30-45 KTS BY TAU 72. 
LONG-TERM MEDIUM CONFIDENCE IN THE INTENSITY FORECAST IS A RESULT OF 
AN INCREASING SPREAD AMONG THE MODELS BETWEEN TAUS 72 AND 96. WHILE 
DETERMINISTIC GFS IS THE MOST AGGRESSIVE INITIALLY, IT BECOMES MORE 
SHALLOW IN ITS GUIDANCE AND ONLY REACHES 40 KTS AT THE LOWEST POINT. 
HAFS IS ON THE OTHER SIDE OF THE ENVELOPE, WITH SLIGHTLY MORE 
CONSERVATIVE INITIAL WEAKENING, FOLLOWED BY A LOWEST VALUE OF BELOW 30 
KTS AT TAU 72. OFFICIAL JTWC FORECAST IS LAID VERY CLOSE TO THE MULTI-
MODEL CONSENSUS IN THE EARLY STAGES OF THE WEAKENING, FOLLOWED BY 
APPROXIMATELY 5 KTS BELOW THE MEAN TOWARDS THE END OF THE FORECAST.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: HIGH
   INTENSITY 72-120 HR: MEDIUM//
NNNN