WDPN31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 01W (ONE) WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.8N 123.0E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 159 NM SOUTHEAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 10 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A SLOWLY
CONSOLIDATING SYSTEM WITH CONVECTIVE BANDING WRAPPING FROM THE
NORTHWEST INTO A LOW-LEVEL CIRCULATION CENTER (LLCC) OBSCURED BY
PERSISTENT CONVECTION AND STRONG POLEWARD OUTFLOW FROM THE NORTHERN
PERIPHERY. A 250445Z AMSR-2 MICROWAVE IMAGE DEPICTS LOW-LEVEL
BANDING TO THE SOUTHWEST AND MORE SIGNIFICANT CONVECTIVE BANDING
WITHIN THE NORTHWESTERN QUADRANT WRAPPING INTO THE CENTER OF THE
SYSTEM. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED
ON THE PREVIOUS MICROWAVE IMAGE, MSI, AND ANIMATED RADAR IMAGERY
DEPICTING THE CIRCULATION TO THE NORTHWEST OF MASBATE, PHILIPPINES.
OVER THE LAST SIX HOURS, THE SYSTEM HAS MAINTAINED INTENSITY WHILE
PASSING OVER BOTH WARM WATER AND LAND AMIDST THE CENTRAL PHILIPPINE
ISLANDS. THE INITIAL INTENSITY OF 30 KTS IS ASSESSED WITH HIGH
CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: SUBTROPICAL RIDGE (STR)

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: NO CURRENT ESTIMATE
   RJTD: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 33 KTS AT 250730Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   INITIAL WIND RADII: NOT APPLICABLE

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: FORECAST TRACK SPEEDS HAVE SLOWED
SIGNFICANTLY FROM THE PREVIOUS WARNING BASED ON SLOWER ANTIPATED
NEAR TERM MOTION AS THE SYSTEM TURNS POLEWARD AROUND AN EXTENSION
OF THE STEERING RIDGE.

FORECAST DISCUSSION: TC 01W IS FORECAST TO CONTINUE TO BE STEERED
BY THE STR TO THE EAST THROUGH THE REMAINDER OF THE FORECAST. FLOW
ASSOCIATED WITH THE RIDGE IS EXPECTED TO TRANSITION TO A
NORTHEAST-SOUTHWEST ORIENTATION BETWEEN TAU 12-24, AND THE SYSTEM
WILL TURNOVER NORTHEASTWARD THEREAFTER AFTER ROUNDING THE RIDGE
AXIS. IN THE LATE-TERM FORECAST, THE SYSTEM IS EXPECTED TO BEGIN
MERGING WITH A MID-LATITUDE TROUGH BETWEEN TAU 96-120 AND COMMENCE
EXTRATROPICAL TRANSITION. TC 01W SHOULD SLOWLY INTENSIFY THROUGH
THE NEXT 36 HOURS AS IT CONTINUES TO INTERACT WITH LAND. ONCE FULLY
OVER WATER, THE SYSTEM WILL COUNTINUOUSLY INTENSIFY IN A FAVORABLE
ENVIRONMENT OF LOW TO MODERATE SHEAR, GOOD OUTFLOW, AND WARM SSTS.
ALTHOUGH THE INTENSIFICATION TREND IS EXPECTED TO CONTINUE THROUGH
TAU 72, INTERACTION WITH AN UPPER-LEVEL TROUGH AFTER TAU 48 IS
EXPECTED TO LIMIT THE INTENIFICATION TREND. WEAKENING WILL COMMENCE
ONCE THE SYSTEM BEGINS TO INTERACT WITH THE MID-LATITUDE TROUGH AND
MOVE OVER COOLER SSTS NORTH OF APPROXIMATELY 26N.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE DIFFERS IN HOW
SIGNIFICANTLY TC 01W WILL SPEED UP AFTER ROUNDING THE STR TO THE
EAST. THE ALONG-TRACK DISTANCE BETWEEN ECMWF AND GFS FOR THE 06Z
RUN IS 700NM BY TAU 120, MOSTLY DUE TO DIFFERENCES IN HOW STRONGLY
THE TWO MODELS FORECAST INTERACTION WITH THE MID-LATITUDE TROUGH
THAT APPROACHES FROM THE NORTHWEST AS WELL AS THE SPEED WITH WHICH
THE SYSTEM ROUNDS THE STEERING RIDGE AXIS IN THE NEAR-TERM. ECMWF
IS MUCH SLOWER, REFLECTING SLOWER NEAR-TERM MOTION AND MINIMAL
INTERACTION WITH THE MID-LATITUDE TROUGH BETWEEN TAU 96-120, WHILE
THE SYSTEM TURNS MORE QUICKLY IN THE NEAR-TERM AND BECOMES QUICKLY
EMBEDDED IN THE MID-LATITUDE TROUGH BY TAU 120 IN GFS. ENSEMBLE
GUIDANCE REVEALS A BROAD ALONG-TRACK SPREAD OF MEMBERS IN BOTH GFS
AND ECMWF, HIGHLIGHTING THE UNCERTAINTY OF TRACK SPEEDS WITHIN THE
MODEL GUIDANCE. THE INTENSITY GUIDANCE CONSISTENTLY FORECASTS
INTENSIFICATION THROUGH TAU 72, WHILE INTERACTION WITH AN
UPPER-LEVEL TROUGH BY TAU 48 AND LATER INTERACTION WITH THE
MID-LATITUDE TROUGH IN THE EXTENDED PERIOD CONTRIBUTE UNCERTAINTY
TO THE INTENSITY FORECAST. 

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