WDXS33 PGTW 172100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 14S (TALIAH) WARNING NR 
034//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 30.0S 77.0E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 1202 NM EAST-SOUTHEAST OF PORT LOUIS,
MAURITIUS
   MOVEMENT PAST 6 HOURS: SOUTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 21 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
INCREASINGLY ASYMMETRIC SYSTEM WITH A DECOUPLED VORTEX. THE
UPPER-LEVEL ROTATION REMAINS QUITE STRONG BUT IS DISPLACED A FAIR
DISTANCE EAST OF THE LOW LEVEL CIRCULATION CENTER (LLCC) DUE TO
PERSISTENT WEST-NORTHWESTERLY SHEAR. A 171633Z GMI 37GHZ MICROWAVE
IMAGE REVEALS A WELL-DEFINED LLCC WITH DEEP CONVECTIVE BANDS
DISPLACED TO THE EAST. A 171719Z ASCAT-C BULLSEYE PASS SHOWED A
COMPACT LLCC WITH 15-20KT WINDS ACROSS THE WESTERN HALF OF THE
CIRCULATION AND 35-40 KNOT WINDS IN THE SOUTHEASTERN PORTION OF THE
ROTATION. THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE
BASED ON THE GMI 37GHZ IMAGE NOTED ABOVE. THE INITIAL INTENSITY IS
INCREASED TO 40 KNOTS WITH HIGH CONFIDENCE BASED ON THE ASCAT-C
PASS AND HEDGED SLIGHTLY HIGHER THAN THE MOST AGGRESSIVE CIMSS AIDT
ESTIMATE. THE ENVIRONMENT IS MARGINAL, WITH COOL SSTS, MODERATE TO
HIGH VWS AND SIGNIFICANT DRY AIR TO THE WEST, OFFSET BY ROBUST
POLEWARD OUTFLOW INTO THE BASE OF A DEVELOPING JET MAX TO THE
SOUTH.

INITIAL WIND RADII BASIS: SCATTEROMETER DATA 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE EAST-NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   KNES: T1.5 - 25 KTS
   DEMS: T2.0 - 30 KTS
   FMEE: T2.0 - 30 KTS
   CIMSS ADT: 32 KTS AT 171800Z
   CIMSS AIDT: 37 KTS AT 171800Z
   CIMSS D-MINT: 33 KTS AT 171633Z
   CIMSS D-PRINT: 33 KTS AT 171800Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 23-24 CELSIUS
   OUTFLOW: STRONG POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR ALONG THE WESTERN PERIPHERY OF
THE SYSTEM. 

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   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 14S WILL CONTINUE TRACKING
SOUTH-SOUTHWESTWARD ALONG THE WESTERN SIDE OF THE STR FOR THE NEXT
12 TO 24 HOURS. THE STR WEAKENS AND PULLS NORTHWARD, WHILE A TROF
PASSES BY THE TO THE SOUTH OVER THE NEXT DAY, WEAKENING THE
STEERING GRADIENT. TC 14S WILL CONTINUE TO SLOW DOWN IN RESPONSE TO
THE STEADILY WEAKENING STEERING INFLUENCES. THE SYSTEM TURNS
SHARPLY WEST, THEN WEST-NORTHWEST AFTER TAU 24, AS A TRANSIENT LOW-
TO MID-LEVEL RIDGE PASSES BY TO THE SOUTH. THIS RIDGE IS FAST
MOVING AND WILL PASS TO THE EAST OF TC 14S BY TAU 60. THE SYSTEM
TURNS SHARPLY POLEWARD BY TAU 72, AS THE RIDGE TO THE EAST BECOMES
ORIENTED ALONG A NORTHWEST-SOUTHEAST AXIS. EVEN THOUGH THE SYSTEM
IS SITUATED OVER VERY COOL WATERS, MULTI-MODEL PHASE SPACE DIAGRAMS
AND PHASE CLASSIFICATIONS INDICATE IT REMAINS A DEEP, WARM-CORE
TROPICAL CYCLONE. HIGH-RESOLUTION MODELS SUGGEST THAT THE
ENVIRONMENT WILL MOISTEN SOMEWHAT OVER THE NEXT 24 HOURS, AND
COMBINED WITH THE ROBUST POLEWARD OUTFLOW, SUPPORT A BRIEF PERIOD
OF INTENSIFICATION. THE FORECAST CALLS FOR A PEAK OF 45 KNOTS AT
TAU 12, FOLLOWED BY STEADY WEAKENING THROUGH THE REMAINDER OF THE
FORECAST DUE TO THE INFLUENCE OF INCREASING DRY AIR INTRUSION, AND
DECREASED OUTFLOW, PARTICULARLY AFTER TAU 48. THE SYSTEM IS NOT
EXPECTED TO TRANSITION TO EITHER SUBTROPICAL OR EXTRATROPICAL LOW
DURING THE FORECAST PERIOD BUT WILL INSTEAD DISSIPATE AS A TROPICAL
CYCLONE NO LATER THAN TAU 72.  

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE IS IN GOOD AGREEMENT
ON THE TRACK SCENARIO, WITH MINIMAL CROSS-TRACK SPREAD THROUGH TAU
48, THOUGH IT INCREASES TO ABOUT 150NM BY THE END OF THE FORECAST
AS THE SYSTEM TURNS POLEWARD. THE ECMWF SHOWS THE SHARPEST TURN AND
MARKS THE EASTERN SIDE OF THE GUIDANCE ENVELOPE WHILE THE GALWEM
DEPICTS A MUCH LATER TURN AND MARKS THE WESTERN EDGE OF THE
GUIDANCE PACKAGE. THE JTWC FORECAST STICKS CLOSE TO THE GFS
SOLUTION, WITH MEDIUM CONFIDENCE. INTENSITY GUIDANCE IS IN GOOD
AGREEMENT THROUGH THE JTWC FORECAST DEVIATES FROM THE GUIDANCE IN
DEPICTING AN INTENSIFICATION THROUGH TAU 12, AS ALL MEMBERS OF THE
PACKAGE SHOW A STEADY INTENSITY THROUGH TAU 24. FOR THE REMAINDER
OF THE FORECAST, THE JTWC FORECAST IS CONSISTENT WITH THE CONSENSUS
MEAN. 

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