Tropical Storm IN-FA Advisory 7月16日

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 09W (NINE) WARNING
NR 001//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
SUMMARY:
   INITIAL POSITION: 17.5N 134.6E
   INITIAL INTENSITY: 20 KTS
   GEOGRAPHIC REFERENCE: 659 NM SOUTHEAST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 8 FEET
SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS WEAK CENTRAL
CONVECTION EMBEDDED IN A BROAD, ELONGATED AREA OF DENSE CONVECTION
AND AN UPPER LEVEL POLEWARD OUTFLOW CHANNEL TO THE NORTH OF THE
SYSTEM CENTER. THE WINDFIELD DEPICTED IN 160130Z ASCAT-B DATA
FURTHER DEPICTS A BROAD (LESS THAN 60 NM) AREA OF CYCLONIC WINDS
WHICH ALONG WITH WEAK LOW LEVEL CLOUD LINE TRACING FROM THE MSI
LOOP LENDS ONLY OVERALL LOW CONFIDENCE IN THE INITIAL POSITION. THE
INITIAL INTENSITY OF 20 KTS IS ASSESSED WITH MEDIUM CONFIDENCE
BASED ON THE WINDS DEPICTED IN THE ASCAT-B DATA, WHICH INCLUDES
5-10 KTS WINDS OVER THE NORTHWEST SEMICIRCLE AND ISOLATED 30-40 KTS
WINDS DISPLACED 30-60 NM FROM THE STORM CENTER OVER THE SOUTHEAST
SEMICIRCLE. THIS INTENSITY ESTIMATE IS HEDGED SLIGHTLY LOWER THAN A
T1.5 (25 KTS) DVORAK CURRENT INTENSITY FROM KNES BASED ON ANALYSIS
OF THE OVERALL LACK OF ROBUST CONVECTIVE STRUCTURE.
INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).
CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF THE DEEP STR TO
THE EAST.
AGENCY DVORAK AND AUTOMATED FIXES:
   PGTW: NO CURRENT ESTIMATE
   KNES: T1.5 - 25 KTS
FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE POLEWARD
ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE
3. FORECAST REASONING.
SIGNIFICANT FORECAST CHANGES: THIS INITIAL PROGNOSTIC REASONING
MESSAGE ESTABLISHES THE FORECAST PHILOSOPHY.
FORECAST DISCUSSION: TD 09W IS TRACKING THROUGH A COMPLEX STEERING
AND OUTFLOW ENVIRONMENT AND APPEARS TO BE NESTED ALONG THE
SOUTHEASTERN PERIPHERY OF A BROAD, ROUGHLY 600 NM DIAMETER MONSOON
DEPRESSION. IN THE NEAR TERM, THE SYSTEM IS FORECAST TO TRACK
GENERALLY POLEWARD ALONG THE WESTERN PERIPHERY OF THE STEERING
RIDGE. DURING THIS TIME, THE UPPER LEVEL CYCLONE POSITIONED TO THE
NORTH OF THE SYSTEM CENTER IS FORECAST TO TRAVEL SLOWLY WESTWARD.
AS A RESULT, THE SOUTHEASTERLY FLOW ASSOCIATED WITH THE EASTERN
PORTION OF THIS CYCLONE IS EXPECTED TO ENHANCE THE OUTFLOW OF TD
09W AND LEAD TO INTENSIFICATION. AFTER TAU 48, TD 09W WILL BEGIN A
GENERALLY NORTHWESTWARD TRACK UNDER THE STEERING INFLUENCE OF AN
EXTENSION OF THE STR THAT IS POSITIONED TO THE NORTHEAST. AS
ENVIRONMENTAL CONDITIONS AND OUTFLOW ARE FORECAST TO REMAIN
FAVORABLE DURING THIS TIME, TD 09W WILL FURTHER INTENSIFY AS IT
TRACKS TOWARDS OKINAWA, JAPAN AND REACH TYPHOON STRENGTH BY TAU 72.
THEREAFTER THE SYSTEM WILL FURTHER INTENSIFY THROUGH TAU 120. THERE
IS A HIGH DEGREE OF UNCERTAINTY IN THE TRACK AND INTENSITY FORECAST
DUE TO THE COMPLEX NATURE OF THE STEERING ENVIRONMENT AND UPPER
LEVEL FLOW.
MODEL DISCUSSION: NUMERICAL MODEL SOLUTIONS DIVERGE SIGNIFICANTLY
FROM ONE ANOTHER IN BOTH TRACK AND INTENSITY. THIS DIVERGENCE IS
LARGELY DUE TO UNCERTAINTY IN THE TIMING AND MAGNITUDE OF A STR
REORIENTATION AND REPOSITIONING OF THE UPPER LEVEL CYCLONE LOCATED
TO THE NORTH OF TD 09W. THE GFS (DETERMINISTIC AND ENSEMBLE) AND
NAVGEM SOLUTIONS DEPICT A POLEWARD TRACK WITH GRADUAL
INTENSIFICATION THROUGH TAU 120. BOTH OF THESE MODELS BRING THE
FORECAST TRACK NORTH OF OKINAWA BETWEEN TAU 72 AND 96. THE UKMET
AND ECMWF ENSEMBLE MEAN TRACK GUIDANCE PROVIDE MUCH SLOWER TRACK
SPEEDS AND FORECAST THE SYSTEM TO PASS SOUTH OF OKINAWA AT TAU 120.
THE JTWC FORECAST TRACK IS PLACED JUST BEHIND AND SLIGHTLY SOUTH OF
THE MULTI-MODEL CONSENSUS TRACK GUIDANCE AND IS THUS HEDGED TOWARDS
THE ECMWF AND UKMET ENSEMBLE MEAN SOLUTIONS. DUE TO THE LARGE
SPREAD IN MODEL SOLUTIONS, THERE IS OVERALL LOW CONFIDENCE IN THE
JTWC FORECAST TRACK.
FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: LOW
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: MEDIUM//
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