WDXS32 PGTW 052100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 10S (CLIFF) WARNING 
NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 21.1S 82.8E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 1031 NM SOUTHEAST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: WEST-SOUTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 15 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC), WITH THE
NORTHERN HEMISPHERE EXPOSED AND THE SOUTHERN HEMISPHERE OBSCURED BY
AN AREA OF SYMMETRICAL FLARING CONVECTION. A 051620Z GMI COLOR
COMPOSITE MICROWAVE IMAGE SHOWS THE DISORGANIZED AND INCREASINGLY
ELONGATED LLCC, DEVOID OF SIGNIFICANT CONVECTIVE ACTIVITY AND AN
AREA OF ENHANCED CONVECTION SHEARED TO THE SOUTH. THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
AFOREMENTIONED EIR AND MICROWAVE IMAGERY. RECENT L-BAND RADIOMETER
BASED WIND ESTIMATES FROM BOTH SMAP AND SMOS INDICATE AN ASYMMETRIC
WIND FIELD, WITH 20-30 KNOT WINDS IN THE NORTHERN HEMISPHERE AND A
BROAD SWATH OF 35-40 KNOT WINDS TO THE SOUTH. THE INITIAL INTENSITY
IS THUS SET AT 35 KNOTS, SLIGHTLY ABOVE THE PGTW T2.0 DVORAK
ESTIMATE AND THE ADT OF T2.1. WHILE THE SYSTEM IS OBVIOUSLY
SHEARED, THE AMOUNT OF SHEAR IS IN QUESTION WITH THE CIMSS ANALYSIS
INDICATING 5-10 KNOTS, WHILE HWRF AND GFS AREA AVERAGE SKEW-T
ANALYSES REVEAL SHEAR MORE IN THE RANGE OF 15-20 KNOTS. BASED ON
THE SATELLITE DEPICTION, THE HIGHER SHEAR VALUES ARE LIKELY MORE
CORRECT.

INITIAL WIND RADII BASIS: SMAP DATA 

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF LOW TO MID-LEVEL
SUBTROPICAL RIDGE (STR) TO THE SOUTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   CIMSS ADT: 31 KTS AT 051515Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY
UNFAVORABLE
   VWS: 15-20 KTS
   SST: 27-28 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: LOW TO MID-LEVEL DRY AIR

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: AS TC 10S HAS WEAKENED, THE PRIMARY STEERING
MECHANISM HAS SHIFTED OVER TO THE LOW TO MID-LEVEL STR TO THE SOUTH
AND TC 10S HAS TURNED SHARPLY WESTWARD IN THE LAST 6-12 HOURS. NO
SIGNIFICANT CHANGE IS EXPECTED IN THIS TRACK THROUGH THE FORECAST
PERIOD. THE PRESENCE OF LOW TO MID-LEVEL STABLE, DRY AIR, AS
REVEALED BY THE LARGE STRATOCUMULUS FIELD TO THE SOUTH, IS BEING
WRAPPED INTO THE CORE OF THE SYSTEM. COMBINED WITH MODERATE AND
INCREASING NORTHERLY SHEAR, AND STEADILY DECREASING SSTS, TC 10S IS
FORECAST TO STEADILY, IF SOMEWHAT SLOWLY, WEAKEN OVER THE NEXT 36
HOURS, DIPPING BELOW WARNING THRESHOLD NO LATER THAN TAU 36. 

MODEL DISCUSSION: WITH THE CONTINUED EXCEPTION OF NAVGEM, WHICH
REMAINS AN UNREALISTIC POLEWARD SIDE OUTLIER, THE BULK OF THE TRACK
GUIDANCE IS IN GOOD AGREEMENT THROUGH THE FORECAST PERIOD,
SUPPORTING THE JTWC FORECAST WITH HIGH CONFIDENCE. SIMILARLY, ALL
OF THE INTENSITY GUIDANCE INDICATES SLOW BUT STEADY WEAKENING
THROUGH THE PERIOD, LENDING HIGH CONFIDENCE IN THE JTWC FORECAST
INTENSITY. 

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