WDPN31 PGTW 260900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (EWINIAR) WARNING NR 
007//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 14.5N 121.8E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 795 NM SOUTH-SOUTHWEST OF KADENA AB
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 06 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 01W (EWINAR) DEVELOPING AN EYE FEATURE AS IT HAS TRACKED OVER
WARM TROPICAL WATERS OF LAYMON BAY, PHILIPPINES, WHICH IS ALSO
DEPICTED IN A 260527Z AMSR-2 89GHZ MICROWAVE IMAGE. WATER VAPOR
IMAGERY DEPICTS RADIAL OUTFLOW THAT IS PARTICULARLY STRONG TO THE
NORTH TOWARDS A JET MAXIMUM. THE INITIAL POSITION IS PLACED WITH
HIGH CONFIDENCE BASED ON THE PREVIOUSLY MENTIONED EYE FEATURE
EVIDENT IN MSI AND MICROWAVE IMAGERY AS WELL AS RECENT RADAR
IMAGERY FROM THE PHILIPPINES. THE INITIAL INTENSITY OF 55 KTS IS
ASSESSED WITH MEDIUM CONFIDENCE GIVEN PRESENTATION OF THE
DEVELOPING EYE FEATURE AND SUPPORTIVE SYNOPTIC SEA LEVEL PRESSURE
OBSERVATIONS FROM REPORTING STATIONS IN SOUTHERN LUZON.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR) TO THE WEST

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T2.5 - 35 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD

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: TS 01W WILL CONTINUE TO ROUND A WESTERN
EXTENSION OF THE STR OVER THE NEXT 12 HOURS AND FOLLOW A
NORTHWESTWARD TRACK ALONG THE WESTERN PERIPHERY OF THE STR FOR THE
REMAINDER OF THE FORECAST PERIOD. INFLUENCE FROM A MID-LATITUDE
TROUGH BETWEEN TAU 72-96 MAY SWAY THE SYSTEM ON A SLIGHTLY MORE
NORTH-NORTHWESTERLY TRACK, POTENTIALLY BRINGING THE SYSTEM
MARGINALLY CLOSER TO OKINAWA THAN REFLECTED IN THE CURRENT FORECAST
BETWEEN TAU 96-120. RAPID INTENSIFICATION IS EXPECTED TO OCCUR
THROUGH THE FIRST 24-36 HOURS FUELED BY LOW SEA SURFACE
TEMPERATURES (SSTS), LOW VERTICAL WIND SHEAR, AND FAVORABLE
UPPER-LEVEL DIVERGENCE. THE PEAK OF 100KTS IS SLIGHTLY HIGHER THAN
THE PREVIOUS FORECAST DUE TO THE UNEXPECTED INTENSIFICATION OVER
LAND THAT OCCURRED OVER THE PREVIOUS TWELVE HOURS. BETWEEN TAU
72-96, AN MID-LATITUDE TROUGH WILL ENCROACH ON THE SYSTEM AND
INITIATE EXTRATROPICAL TRANSITION THROUGH THE FINAL 96-120 HOURS OF
THE FORECAST, INCREASING VWS EXPONENTIALLY. SSTS ARE COOL AND
UNFAVORABLE NORTH OF 26N, SO THE SYSTEM WILL CONTINUE TO WEAKEN AS
EXTRATROPICAL TRANSITION BEGINS. 

MODEL DISCUSSION: DETERMINISTIC TRACK GUIDANCE INDICATES MINIMAL
UNCERTAINTY IN TRACK DIRECTION AS THE TS 01W ROUNDS THE WESTERN
PORTION OF THE STR AND CONTINUES NORTHEAST. THE HIGH TRACK
CONFIDENCE IS SUPPORTED BY THE ALONG-TRACK SPREAD WHICH IS NOW ONLY
75NM BY TAU 120. CONFIDENCE DECREASES AFTER TAU 72 DUE TO
VARIATIONS IN THE INFLUENCE OF INTERACTION WITH THE MID-LATITUDE
TROUGH AND POTENTIAL ASSOCIATED NORTHWESTWARD DEVIATION FROM THE
CONSENSUS TRACK. ABOUT TWENTY PERCENT OF EC-EPS MEMBERS INDICATE A
TROUGH-ALTERED TRACK CLOSER TO OKINAWA, WHILE GEFS MEMBERS DO NOT
INDICATE DEVIATION FROM THE PRIMARY MODEL GROUPING LYING NEAR THE
MULTI-MODEL CONSENSUS. THERE IS SOME SPREAD IN THE CURRENT
INTENSITY FORECAST GUIDANCE, WITH MESOSCALE MODEL AND SHIPS
GUIDANCE INDICATING STEADY INTENSIFICATION RATES BUT SEVERAL RAPID
INTENSIFICATION AIDS TRIGGERING WITH HIGH ASSOCIATED PROBABILITIES
STARTING IMMEDIATELY. THE CURRENT FORECAST FAVORS THE RAPID
INTENSIFICATION GUIDANCE EARLY ON GIVEN THE CURRENT STRUCTURE AND
ENVIRONMENT AND MATCHES THE CONSENSUS GUIDANCE IN LATER TAUS.

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