WDPN31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 01W (ONE) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.5N 122.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 96 NM SOUTHEAST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: NORTHWESTWARD AT 10 KTS
   SIGNIFICANT WAVE HEIGHT: 12 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS
PERSISTENT CONVECTION OBSCURING THE LOW-LEVEL CIRCULATION CENTER
(LLCC) WITH CONVECTIVE BANDS WRAPPING IN FROM BOTH THE NORTHWEST
AND SOUTHEAST. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON RADAR IMAGERY DEPICTING THE CIRCULATION IN THE VICINITY
OF BOHOL ISLAND, PHILIPPINES. THE INITIAL INTENSITY OF 35 KTS IS
ASSESSED WITH HIGH CONFIDENCE BASED ON THE AGENCY AND OBJECTIVE
FIXES LISTED BELOW.

INITIAL WIND RADII BASIS: PERSISTENCE AND OBJECTIVE BEST TRACK

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

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T3.0 - 45 KTS
   CIMSS ADT: 39 KTS AT 251130Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 0-5 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: STRONG POLEWARD

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

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL STORM 01W WILL CONTINUE TO ROUND THE
STR TO THE EAST OVER THE NEXT 24 HOURS, TRACKING NORTHWESTWARD
INITIALLY BEFORE CURVING NORTHEASTWARD. AS THE STR ACQUIRES A
NORTHEAST-SOUTHWEST ORIENTATION, THE SYSTEM WILL TRACK
NORTHEASTWARD THROUGH THE REMAINDER OF THE FORECAST. TS 01W WILL
BEGIN TO INTERACT WITH A MID-LATITUDE TROUGH BETWEEN TAU 96-120 AND
COMMENCE EXTRATROPICAL TRANSITION. FOR THE NEXT 24 HOURS THE SYSTEM
WILL GRADUALLY INTENSIFY WITH INTERMITTENT LAND INTERACTION WHILE
IN THE VICINITY OF THE PHILIPPINE ISLANDS. ONCE COMPLETELY OVER
WATER, THE SYSTEM WILL QUICKLY INTENSIFY IN AN ENVIRONMENT OF LOW
TO MODERATE SHEAR, GOOD POLEWARD OUTFLOW, AND WARM SEA SURFACE
TEMPERATURES. AS THE SYSTEM BEGINS TO INTERACT WITH THE UPPER-LEVEL
TROUGH BETWEEN TAU 48 AND TAU 72, AND LATER WITH THE AFOREMENTIONED 
MID-LATITUDE TROUGH, THE ENVIRONMENT WILL BECOME UNFAVORABLE
WITH SHEAR INCREASING SIGNIFICANTLY AND COOLER ALONG-TRACK SSTS 
POLEWARD OF 26N. 

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE DEPICTIONS OF TS 01W
INITIALLY ROUNDING THE STR TO THE EAST VARY. ECMWF DEPICTS A SLOWER
TRACK, INTERACTING MORE WITH LAND THAN DEPICTED IN THE GFS
SOLUTION, WHICH SPEEDS THE SYSTEM OUT OVER WATER QUICKLY. OVER TIME
DIFFERENCES IN NEAR-TERM STORM SPEED BETWEEN ECMWF AND GFS
SOLUTIONS, AS WELL AS DIFFERING DEPICTIONS OF THE INTERACTION
BETWEEN THE SYSTEM AND A MID-LATITUDE TROUGH BETWEEN TAU 96-120,
LEAD TO A VERY LARGE ALONG-TRACK SPREAD, ULTIMATELY 950NM BETWEEN
ECMWF AND GFS BY TAU 120. HOWEVER, ENSEMBLE GUIDANCE REVEALS A
BROAD ALONG-TRACK SPREAD WITH DISTINCT GROUPINGS OF FASTER AND
SLOWER TRACKS IN BOTH THE GEFS AND EC-EPS MEMBERS, HIGHLIGHTING THE
UNCERTAINTY OF TRACK SPEEDS WITHIN THE MODEL GUIDANCE. THE
INTENSITY GUIDANCE CONSISTENTLY FORECASTS INTENSIFICATION THROUGH
TAU 72 AND WEAKENING OCCURRING AFTER TAU 72 DUE TO INTERACTION WITH
AN UPPER-LEVEL TROUGH FOLLOWED BY THE MID-LATITUDE TROUGH AND
PASSAGE OVER COOLER SSTS.

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