WDXS31 PGTW 190900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 05S (DARIAN) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3S 93.4E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 205 NM WEST OF THE COCOS ISLANDS
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 03 KTS
   SIGNIFICANT WAVE HEIGHT: 19 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS INCREASINGLY
ORGANIZED DEEP CONVECTION WRAPPING AROUND A DISTINCT BUT STILL
RELATIVELY BROAD LOW-LEVEL CIRCULATION CENTER. THE INITIAL POSITION
IS PLACED WITH MEDIUM CONFIDENCE BASED ON RECENT SATELLITE FIXES
FROM PGTW, KNES AND APRF. THE INITIAL INTENSITY OF 55 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON A SUBJECTIVE DVORAK
ESTIMATE OF T3.5 FROM PGTW AND SUPPORTIVE AUTOMATED ADT AND AIDT
DATA FROM CIMSS. TC 05S HAS STEADILY DEVELOPED OVER THE PAST TWELVE
HOURS IN THE PRESENCE OF A FAVORABLE UPPER-LEVEL FLOW PATTERN BUT
MARGINAL SEA SURFACE TEMPERATURES WITH SOME COOL WATER UPWELLING.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK AND A 190323Z
METOP-B PARTIAL ASCAT PASS

CURRENT STEERING MECHANISM: NEAR EQUATORIAL RIDGE TO THE NORTHEAST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   KNES: T4.0 - 65 KTS
   APRF: T4.0 - 65 KTS
   CIMSS ADT: 53 KTS AT 190540Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 26-27 CELSIUS
   OUTFLOW: MODERATE POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECAST TRACK SPEEDS FOR THE TAU 72
TO TAU 120 PERIOD HAVE SLOWED FROM THE PREVIOUS WARNING CONSISTENT
WITH CONSENSUS MODEL GUIDANCE. HOWEVER, THE OVERALL FORECAST
PHILOSOPHY REMAINS THE SAME.

FORECAST DISCUSSION: TC 05S WILL CONTINUE TO TRACK SLOWLY
SOUTHEASTWARD TO POLEWARD OVER THE NEXT 24 HOURS UNDER THE
CONTINUED STEERING INFLUENCE OF THE NEAR EQUATORIAL RIDGE TO THE
NORTHEAST. AFTER TAU 24, A BUILDING SUBTROPICAL RIDGE TO THE SOUTH
IS EXPECTED TO TAKE OVER AS THE DOMINANT STEERING MECHANISM AND
PUSH TC 05S ON A GENERALLY WESTWARD TRAJECTORY THROUGH THE
REMAINDER OF THE FORECAST PERIOD. CONTINUED, STEADY INTENSIFICATION
THROUGH TAU 24 IS LIKELY GIVEN FAVORABLY LOW VERTICAL WIND SHEAR
AND A SUPPORTIVE POLEWARD OUTFLOW PATTERN. HOWEVER, THE MAGNITUDE
OF ADDITIONAL INTENSIFICATION WILL BE LIMITED AS THE SLOW-MOVING
SYSTEM PASSES OVER A SHALLOW LAYER OF 26-27C WATER AND CONTENDS
WITH INDUCED UPWELLING OF COOLER WATER. AFTER TAU 24, THE SYSTEM IS
EXPECTED TO WEAKEN SLIGHTLY PRIMARILY DUE TO MORE RESTRICTED
UPPER-LEVEL OUTFLOW AND CONTINUED PASSAGE OVER MARGINAL SEA SURFACE
TEMPERATURES. A SLIGHT UPTICK IN THE INTENSITY LATE IN THE FORECAST
PERIOD IS POSSIBLE AS THE SYSTEM DIPS A BIT POLEWARD AROUND THE
STEERING RIDGE AND OUTFLOW AGAIN IMPROVES.

MODEL DISCUSSION: NUMERICAL MODELS REMAIN IN AGREEMENT REGARDING
THE OVERALL FORECAST SCENARIO OF INITIALLY POLEWARD MOTION THROUGH
TAU 24 TO 36, FOLLOWED BY A TURN TOWARD THE WEST. MODEL SPREAD IS
FAIRLY LIMITED THROUGH TAU 72, BUT INCREASES THEREAFTER AS DEPICTED
EVOLUTION OF THE SUBTROPICAL STEERING RIDGE VARY. IT IS TOO EARLY
TO TELL WHETHER THE RIDGE WILL REMAIN SOLIDLY IN PLACE TO THE SOUTH
OF TC 05S OR A BREAK WILL DEVELOP ALLOWING THE SYSTEM TO DIP
FARTHER POLEWARD AFTER TAU 72 THAN CURRENTLY ANTICIPATED. THE
CURRENT FORECAST TRACK LIES NEAR THE MIDDLE OF THE GUIDANCE
ENVELOPE, NEAR THE MULTIPLE MODEL CONSENSUS AND ECMWF MODEL
SOLUTIONS. INTENSITY FORECAST GUIDANCE IS ALSO IN FAIR AGREEMENT
FOR THE FIRST 72 HOURS OF THE FORECAST GIVEN THE FAIRLY
STRAIGHTFORWARD SET OF ENVIRONMENTAL INFLUENCES. AS EXPECTED,
HOWEVER, DEPICTIONS OF INTENSITY IN THE LATER TAUS VARY
SIGNIFICANTLY DEPENDING ON THE MODEL-PREDICTED SYNOPTIC
ENVIRONMENTS.

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: MEDIUM
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
NNNN