WDXS31 PGTW 102100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 03S (THREE) WARNING NR 
005//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 10.2S 64.7E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 499 NM WEST-SOUTHWEST OF DIEGO GARCIA
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
COMPACT AND PARTIALLY EXPOSED LOW LEVEL CIRCULATION CENTER (LLCC),
DISPLACED TO THE NORTHEAST OF A REGION OF DEEP CONVECTION WHICH HAS
RECENTLY DEVELOPED ALONG A CONVERGENCE LINE SOUTHWEST OF THE LLCC.
THE INITIAL POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE
PARTIALLY EXPOSED LLCC IN THE EIR IMAGERY FROM EWS-G2. AN EARLIER
101342Z SMOS PASS REVEALED 33 KNOT 10MIN WINDS IN THE SOUTHWESTERN
QUADRANT OF THE CIRCULATION PRIOR TO THE ONSET OF SIGNIFICANT
CONVECTIVE DEVELOPMENT IN THAT REGION, SUPPORTING THE 35 KNOT
INITIAL INTENSITY ASSESSMENT WITH HIGH CONFIDENCE. ENVIRONMENTAL
CONDITIONS ARE MARGINAL, WITH HIGH NORTHEASTERLY SHEAR, A
RELATIVELY DRY ATMOSPHERE, MARGINAL SSTS (26-27C) AND MODERATE
POLEWARD OUTFLOW ALOFT.

INITIAL WIND RADII BASIS: SMOS DATA.

CURRENT STEERING MECHANISM: NORTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) CENTERED TO THE SOUTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   DEMS: T2.5 - 35 KTS
   FMEE: T2.5 - 35 KTS
   CIMSS ADT: 28 KTS AT 101800Z
   CIMSS AIDT: 33 KTS AT 101730Z
   CIMSS D-MINT: 29 KTS AT 101409Z
   CIMSS D-PRINT: 34 KTS AT 101730Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINAL
   VWS: 25-30 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD
   OTHER FACTORS: DRY MID-LEVEL AIR, PARTICULARLY IN THE NORTH AND
EASTERN PORTIONS OF THE CIRCULATION.  

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THE FORECAST HAS BEEN TRUNCATED TO 48
HOURS DUE TO A REASSESSMENT OF THE FORECASTED CONDITIONS AND
SIGNIFICANT CHANGE IN THE MODEL GUIDANCE. 

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 03S HAS SLOWED
OVERNIGHT, WHILE ALSO TURNING SHARPLY TOWARDS THE NORTHWEST,
ESPECIALLY OVER THE LAST SIX HOURS DUE TO A SLIGHT WEAKENING IN THE
STEERING GRADIENT INDUCED BY A BREAK IN THE STR TO THE SOUTH.
GLOBAL MODELS INDICATE THE BREAK IN THE RIDGE WILL QUICKLY MOVE OFF
TO EAST, REPLACED BY A BUILDING RIDGE MOVING IN FROM THE WEST. THIS
WILL REESTABLISH A STRONG STEERING GRADIENT, AND TC 03S IS FORECAST
TO TRACK OFF TO THE NORTHWEST THROUGH THE REMAINDER OF THE FORECAST
PERIOD. THE SYSTEM HAS BEEN ABLE TO MAINTAIN AT LEAST 35 KNOT
INTENSITY, EVEN IN THE FACE OF PERSISTENTLY HIGH NORTHEASTERLY
SHEAR DUE TO CYCLIC BURSTS OF CONVECTION, WHICH APPLY ENOUGH
IMPETUS TO SUSTAIN THE WIND FIELD. THE CURRENT CONVECTIVE BURST
SEEN IN THE EIR IS JUST THE LATEST ITERATION OF THIS CYCLE, AND
WILL LIKELY LAST ANOTHER FEW HOURS BEFORE THE CONVECTION DISSIPATES
ONCE MORE. THIS EVOLUTION IS DEPICTED WELL IN THE MESOSCALE MODELS
AS WELL, AND IS EXPECTED TO CONTINUE FOR ABOUT ANOTHER 24 TO 36
HOURS. AFTER THAT HOWEVER, THE ATMOSPHERE IS EXPECTED TO DRY EVEN
MORE, AND SHEAR IS EXPECTED TO INCREASE BEYOND ITS ALREADY HIGH
VALUES, WHICH WILL BOTH INHIBIT CONVECTIVE DEVELOPMENT AND SHEAR
ANY CONVECTION THAT MAY BE ABLE TO BRIEFLY FLARE UP. THE SYSTEM IS
FORECAST TO WEAKEN BELOW WARNING THRESHOLD BY TAU 48. 

MODEL DISCUSSION: DETERMINISTIC, ENSEMBLE AND ARTIFICIAL
INTELLIGENCE (AI) MODEL TRACKERS ARE ALL IN VERY STRONG AGREEMENT,
WITH MINIMAL CROSS-TRACK SPREAD THROUGH THE FORECAST PERIOD. SOME
MODEST ALONG-TRACK SPREAD BEGINS TO SHOW UP AROUND THE END OF THE
FORECAST, BUT IS NOT SIGNIFICANT. THE JTWC FORECAST IS PLACED NEAR
THE CONSENSUS MEAN WITH HIGH CONFIDENCE. INTENSITY GUIDANCE IS MORE
MIXED, WITH THE HWRF DEPICTING A NEAR-TERM INTENSIFICATION UP TO
ABOUT 45 KNOTS BEFORE RAPIDLY WEAKENING, WHILE COAMPS-TC AND HAFS-A
DEPICT A FLAT INTENSITY TREND FOR ABOUT 24 TO 36 HOURS BEFORE
DROPPING SHARPLY AND THE REMAINDER OF THE GUIDANCE WEAKENS THE
SYSTEM IMMEDIATELY FROM TAU 00. THE JTWC FORECAST IS POSITIONED
NEAR THE HAFS-A GUIDANCE WITH MEDIUM CONFIDENCE. 

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