WDXS31 PGTW 201500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (HORACIO) WARNING 
NR 002//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 15.4S 75.6E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 530 NM SOUTH-SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHWESTWARD AT 07 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) IMAGERY REVEALS TROPICAL CYCLONE
(TC) 22S (HORACIO) WITH ITS FULLY OBSCURED LOW-LEVEL CIRCULATION
CENTER (LLCC). OVER THE LAST SIX HOURS, SPIRAL BANDS OF DEEP
CONVECTION HAVE BEEN DEVELOPING AND WRAPPING INTO THE CORE OF THE
LLCC. DRY AIR IS SURROUNDING THE SYSTEM, WHICH IS PARTICULARLY
EVIDENT THROUGHOUT THE NORTHEASTERN QUADRANT, BUT TC 22S HAS SO FAR 
BEEN ABLE TO COCOON ITSELF WITHIN AN AREA OF MOIST AIR AVAILABLE 
THROUGHOUT THE ATMOSPHERIC COLUMN. AS SUCH, THE ENVIRONMENTAL 
CONDITIONS ARE PREDOMINANTLY FAVORABLE AND ARE ADDITIONALLY 
CHARACTERIZED BY WARM (28-29 C) SEA SURFACE TEMPERATURES (SST), STRONG 
POLEWARD OUTFLOW ALOFT, AND LOW (10-15 KTS) VERTICAL WIND SHEAR. THE 
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE 
EXTRAPOLATION FROM A 200818Z GCOMW1 AMSR2 PASS IN CONJUNCTION WITH THE 
AGENCY POSITION FIXES. THE INITIAL INTENSITY OF 45 KTS IS ALSO 
ASSESSED WITH MEDIUM CONFIDENCE BASED ON SIGNIFICANTLY IMPROVED 
CONVECTIVE STRUCTURE INDICATED BY THE AGENCY DVORAK AND OBJECTIVE 
ESTIMATES LISTED BELOW.

INITIAL WIND RADII BASIS: 200626Z OCEANSAT-3 OSCAT PASS

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   DEMS: T3.0 - 45 KTS
   FMEE: T3.0 - 45 KTS
   FIMP: T3.0 - 45 KTS
   CIMSS ADT: 55 KTS AT 201200Z
   CIMSS AIDT: 44 KTS AT 201200Z
   CIMSS D-MINT: 30 KTS AT 200820Z
   CIMSS D-PRINT: 42 KTS AT 201230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

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 MAINTAIN A GENERALLY
WEST-SOUTHWESTWARD TRAJECTORY, STEERED BY THE DEEP-LAYER FLOW 
THROUGHOUT THE NORTHWESTERN PERIPHERY OF A PROMINENT STR CENTERED TO 
THE SOUTHEAST. THE SYNOPTIC ENVIRONMENT IS EXPECTED TO REMAIN LARGELY
CONDUCIVE FOR DEVELOPMENT THROUGH THE NEXT 12 HOURS. BETWEEN TAU 12
AND TAU 48, AN AMPLIFICATION OF THE UPPER-LEVEL EASTERLY FLOW IS
PROJECTED TO INCREASE THE VWS TO 15-25 KTS, THEREBY POTENTIALLY 
INHIBITING A MORE RAPID RATE OF INTENSIFICATION. AS TC HORACIO 
APPROACHES THE AXIS OF THE STR, THE VERTICAL WIND SHEAR IS EXPECTED TO 
TEMPORARILY DECREASE ALLOWING FOR THE SYSTEM TO REACH PEAK INTENSITY 
OF 100-105 KTS AROUND TAU 96. AFTERWARDS, THE SYSTEM WILL BEGIN TO 
INTERACT WITH AN UPPER-LEVEL JET STREAK. AT THE SAME TIME 
EXTRATROPICAL TRANSITION (ETT) WILL BE INITIATED. ETT IS EXPECTED 
TO COMPLETE BEYOND THE CURRENT FORECAST PERIOD. ADDITIONALLY, 
SIGNIFICANT DRY AIR INTRUSION BEGINNING SHORTLY AFTER TAU 96 WILL 
RESULT IN RAPID WEAKENING OF THE SYSTEM.

MODEL DISCUSSION: CONSIDERABLE UNCERTAINTY ASSOCIATED WITH THE
INTER-MODEL DISCREPANCY EXISTS REGARDING THE MAGNITUDE AND DURATION
OF THE EASTERLY SHEAR EVENT, WITH THE ECMWF SOLUTION DEPICTING A
SIGNIFICANTLY MORE ROBUST SHEAR PROFILE THAN GFS-BASED GUIDANCE.
NUMERICAL MODEL INTENSITY PREDICTION GUIDANCE IS IN GENERAL AGREEMENT 
ON A STEADY DEVELOPMENT TREND, WITH SEVERAL MEMBERS SUGGESTING THE 
POTENTIAL FOR A RAPID INTENSIFICATION (RI) EVENT. HAFS-A REPRESENTS 
THE MOST AGGRESSIVE SOLUTION, FORECASTING A PEAK INTENSITY OF NEARLY 
120 KTS AROUND TAU 84. THE JTWC OFFICIAL FORECAST REFLECTS THE MULTI-
MODEL CONSENSUS IN REGARDS TO INTENSITY THROUGHOUT THE FORECAST WITH 
MEDIUM CONFIDENCE. SHORT-TERM TRACK PREDICTION IS ASSESSED WITH HIGH 
CONFIDENCE, AS REFLECTED BY A CROSS-TRACK SPREAD OF JUST 75 NM AT TAU 
72. THE GUIDANCE ENVELOPE OPENS UP AFTERWARDS, AS MODELS SLIGHTLY 
DISAGREE ON THE TRANSLATION SPEED OF THE SYSTEM AROUND THE AXIS OF THE 
RIDGE. AS SUCH, THE LONG-TERM TRACK FORECAST IS ASSESSED WITH MEDIUM 
CONFIDENCE, AS WITNESSED BY THE ALONG-TRACK SPREAD OF NEARLY 300 NM AT 
TAU 96.

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