WDXS31 PGTW 252100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 22S (HORACIO) WARNING 
NR 013//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.6S 67.8E
   INITIAL INTENSITY: 65 KTS
   GEOGRAPHIC REFERENCE: 848 NM SOUTHEAST OF PORT LOUIS, MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTH-SOUTHEASTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 28 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
CYCLONE 22S (HORACIO) WITH A FULLY EXPOSED, YET WELL-DEFINED
LOW-LEVEL CIRCULATION CENTER. DEEP CONVECTION IS NOW HEAVILY
SHEARED TO THE SOUTHEAST OF THE CENTER. A 251410Z SEN-1 SAR IMAGE
REVEALED THAT THE SURFACE CIRCULATION REMAINS STRONG WITH THE VMAX
MEASUREMENT OF 85 KTS. THE INITIAL INTENSITY OF 65 KTS IS ASSESSED
WITH MEDIUM CONFIDENCE BASED ON A CONTINUED WEAKENING TREND FROM
THE TIME OF THE SAR IMAGE AND IN LINE WITH AGENCY DVORAK CURRENT
INTENSITY (CI) ESTIMATES OF T4.0. CIMSS INTENSITY ESTIMATES ARE
ANALYZED TO BE UNDERESTIMATING THE INTENSITY DUE TO THE LACK OF
DEEP CONVECTION ASSOCIATED WITH THE SYSTEM. THE INITIAL POSITION
AND WIND RADII ARE BOTH PLACED WITH HIGH CONFIDENCE BASED ON A
TIMELY 251702Z METOP-C ASCAT PASS. ENVIRONMENTAL ANALYSIS INDICATES
THAT 22S IS IN A HIGHLY UNFAVORABLE ENVIRONMENT CHARACTERIZED BY
STRONG POLEWARD OUTFLOW GREATLY OFFSET BY VERY HIGH SHEAR, DRY AIR
ENTRAINMENT, AND COOL (24-25 C) SEA SURFACE TEMPERATURES (SST).

INITIAL WIND RADII BASIS: A COMBINATION OF 251702Z METOP-C ASCAT
AND 251410Z SEN-1 SAR DATA 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A
DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T4.0 - 65 KTS
   DEMS: T4.0 - 65 KTS
   CIMSS SATCON: 51 KTS AT 251700Z
   CIMSS ADT: 37 KTS AT 251800Z
   CIMSS AIDT: 46 KTS AT 251800Z
   CIMSS D-MINT: 40 KTS AT 251414Z
   CIMSS D-PRINT: 38 KTS AT 251800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY UNFAVORABLE
   VWS: 45-50 KTS
   SST: 24-25 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: SIGNIFICANT DRY AIR ENTRAINMENT FROM THE NORTH
AND WEST

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

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 TRACKING
SOUTHEASTWARD, ALONG THE SOUTHWESTERN PERIPHERY OF THE STR OVER THE
NEXT 12 HOURS BEFORE TRACK SPEEDS SLOW DOWN SIGNIFICANTLY. THE
BRIEF SLOW MOVEMENT IS ATTRIBUTED TO A TRANSIENT RIDGE THAT BUILDS
IN TO THE SOUTH OF THE SYSTEM AROUND TAU 24. THE RIDGE WILL DEFLECT
22S TO THE SOUTHWEST THROUGH TAU 36 WHERE IT WILL THEN BEGIN A TURN
BACK TO THE SOUTHEAST. SUBTROPICAL TRANSITION IS FORECAST TO BEGIN
AROUND TAU 36 WITH COMPLETION NO LATER THAN TAU 48 AS THE VORTEX
CONTINUES TO SHALLOW AND ENTERS SST BELOW 22 C. IN TERMS OF
INTENSITY, 22S IS FORECAST TO GRADUALLY WEAKEN THROUGHOUT THE
FORECAST PERIOD IN RESPONSE TO THE HIGH SHEAR, DRY AIR ENTRAINMENT,
AND COOLING SST. AN INTENSITY OF AROUND 40 KTS IS FORECAST FOR TAU
48, NEAR THE TIMING OF THE SYSTEM COMPLETING SUBTROPICAL
TRANSITION. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT, WITH THE EXCEPTION OF NAVGEM WHICH TRACKS THE VORTEX
MUCH FURTHER WEST THROUGH TAU 36 THAN THE REMAINDER OF GUIDANCE
DOES. DISCOUNTING NAVGEM, THERE IS A 70 NM CROSS-TRACK SPREAD AT
TAU 48, LENDING HIGH CONFIDENCE TO THE JTWC TRACK FORECAST.
INTENSITY GUIDANCE AGREES ON WEAKENING THROUGHOUT THE FORECAST
PERIOD. HOWEVER, STATISTICAL DYNAMICAL MODELS WEAKEN THE SYSTEM FAR
TOO QUICKLY, SUGGESTING AN INTENSITY OF BELOW 25 KTS AT TAU 24. THE
JTWC INTENSITY FORECAST IS PLACED CLOSE TO THE HAFS-A WITH MEDIUM
CONFIDENCE. 

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