WDXS31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (HORACIO) WARNING 
NR 012//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 27.8S 66.3E
   INITIAL INTENSITY: 70 KTS
   GEOGRAPHIC REFERENCE: 676 NM SOUTHEAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 30 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
CYCLONE (TC) 22S (HORACIO) IN A STATE OF ACCELERATED CYCLOLYSIS AS
IT TRANSITS SOUTHEASTWARD ALONG THE SOUTHWESTERN PERIPHERY OF A STR
CENTERED TO THE EAST. VERY HIGH (35-40 KTS) VERTICAL WIND SHEAR
(VWS) IS ADVECTING NEARLY ALL OF THE REMAINING DEEP CONVECTION
POLEWARD AND EASTWARD, WITH THE PROCESS BEING ASSISTED BY STRONG 
POLEWARD OUTFLOW. THE INITIAL INTENSITY OF 70 KTS IS ASSESSED WITH 
MEDIUM CONFIDENCE BASED ON OBJECTIVE INTENSITY AIDS AND AGENCY DVORAK 
ESTIMATES RAPIDLY DECREASING. ADDITIONAL ENVIRONMENTAL ANALYSIS 
REVEALS MARGINALLY WARM (26-27 C) SEA SURFACE TEMPERATURES (SSTS) 
OFFSET BY INGESTION OF A SUBSTANTIAL MID-LEVEL DRY AIR. A HIGH-
CONFIDENCE INITIAL POSITION IS DETERMINED FROM A PARTIAL 250402Z 
METOP-B ASCAT PASS AND EXTRAPOLATION FROM A 250144Z WSFM MWI COLOR 37 
GHZ MICROWAVE IMAGE.

INITIAL WIND RADII BASIS: 250402Z METOP-B ASCAT PASS AND OBJECTIVE
BEST TRACK 

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   DEMS: T4.0 - 65 KTS
   FMEE: T4.5 - 77 KTS
   FIMP: T4.5 - 77 KTS
   CIMSS SATCON: 61 KTS AT 250430Z
   CIMSS ADT: 65 KTS AT 250600Z
   CIMSS AIDT: 60 KTS AT 250600Z
   CIMSS D-MINT: 56 KTS AT 250147Z
   CIMSS D-PRINT: 46 KTS AT 250630Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 30+ KTS
   SST: 26-27 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT FROM THE NORTH

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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 CONTINUE TRANSITING
POLEWARD AND EASTWARD UNDER THE STEERING INFLUENCE OF THE EASTERN
STR THROUGHOUT THE CURRENT FORECAST PERIOD. THIS STEERING PATTERN
IS EXPECTED TO BE BRIEFLY DISRUPTED BY AN EASTWARD PROPAGATING
UPPER-LEVEL TROUGH, RESULTING IN THE VORTEX DRIFTING SOUTHWESTWARD
BETWEEN TAUS 24 AND 48. VWS IS EXPECTED TO INCREASE TO EXTREME
VALUES (45-55 KTS) OVER THE NEXT 24-36 HOURS RESULTING IN COMPLETE
DECAPITATION OF THE DEEP-LAYER CONVECTION, RESULTING IN DEGRADATION
OF THE VERTICAL COHERENCE OF THE VORTEX AND A RAPID WEAKENING TREND
IN RETURN. THE SYSTEM IS EXPECTED TO BEGIN SUBTROPICAL TRANSITION
(STT) BETWEEN TAUS 36 AND 48, WHILE INTERACTING WITH A PASSING
LONG-WAVE TROUGH. CONTINUOUSLY HOSTILE ENVIRONMENT WILL RESULT IN 
FURTHER WEAKENING AND THE SYSTEM IS EXPECTED TO DISSIPATE SHORTLY 
AFTER IT COMPLETES STT AROUND TAU 72.

MODEL DISCUSSION: THE NUMERICAL TRACK GUIDANCE IS IN STRONG
AGREEMENT THROUGHOUT THE FORECAST, WITH A MINOR INCREASE IN THE CROSS-
TRACK ENVELOPE (70-80 NM) EVIDENT AT TAU 24. A HIGH DEGREE OF 
CONSENSUS EXISTS REGARDING A TRANSIENT DECELERATION AND SOUTHWESTWARD 
DRIFT, FOLLOWED BY A RESUMPTION OF A SOUTH-SOUTHEASTWARD TRAJECTORY 
AROUND TAU 48. CONSEQUENTLY, THE OFFICIAL JTWC TRACK FORECAST IS 
RENDERED WITH HIGH CONFIDENCE. WITH RESPECT TO INTENSITY, ALL 
AVAILABLE GUIDANCE INDICATES A RAPID WEAKENING PHASE, WITH A MAJORITY 
OF SOLUTIONS EXPECTING INTENSITIES DROPPING BELOW 35 KTS AROUND OR 
SHORTLY AFTER TAU 72. IN SHORT TERM, STATISTICAL-DYNAMICAL MODELS ARE 
PROJECTING THE MOST AGGRESSIVE WEAKENING FOLLOWED BY A FULL 
DISSIPATION BETWEEN TAUS 24 AND 36. ON THE OTHER END OF THE GUIDANCE 
SPECTRUM DETERMINISTIC GFS KEEPS THE PEAK WIND SPEEDS AT AROUND 50 KTS 
AT TAU 24. OFFICIAL JTWC INTENSITY FORECAST IS LAID WITH MEDIUM 
CONFIDENCE AND SLIGHTLY ABOVE THE CONSENSUS MEAN, OFFSETTING THE 
OUTLYING STATISTICAL-DYNAMICAL GUIDANCE.

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