WDPN31 PGTW 290900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 26W (NALGAE) WARNING 
NR 010//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.9N 121.4E
   INITIAL INTENSITY: 55 KTS
   GEOGRAPHIC REFERENCE: 48 NM SOUTH-SOUTHEAST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 08 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
TROPICAL STORM 26W IS CURRENTLY LOCATED TO THE SOUTHEAST OF MANILA
AND HAS SLOWED DOWN CONSIDERABLY WHILE TRACKING WEST-NORTHWESTWARD
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
(MSI) DEPICTS PERSISTENT DEEP CONVECTION THAT CONTINUES TO FLARE UP 
AND OBSCURE THE LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL
POSITION IS ASSESSED WITH HIGH CONFIDENCE BASED ON THE MULTI-AGENCY
FIX POSITIONS AS WELL AS THE MSI IMAGERY. THE INITIAL INTENSITY IS
ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE A COMBINATION OF THE
PGTW AND KNES INTENSITY ESTIMATES. ENVIRONMENTAL CONDITIONS HAVE
REMAINED FAVORABLE, WITH LOW (10-15 KNOTS) VERTICAL WIND SHEAR
(VWS), WARM (28-29C) SEA SURFACE TEMPERATURES (SSTS), AND GOOD
WESTWARD AND EQUATORWARD OUTFLOW. HOWEVER, THE ONLY INHIBITING
FACTOR IS THE RUGGED TERRAIN OF THE CENTRAL PHILIPPINES, WHICH IS
DISRUPTING THE LOW-LEVEL FLOW INTO THE CORE OF THE SYSTEM.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF A
DEEP-LAYERED SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.5 - 55 KTS
   RJTD: T3.0 - 45 KTS

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 26W HAS TRACKED WEST-NORTHWEST
OVER THE PAST SIX HOUR ALONG THE SOUTHERN PERIPHERY OF A DEEP-LAYER
SUBTROPICAL RIDGE (STR) POSITIONED TO THE NORTHEAST. THE SYSTEM
WILL CONTINUE TO TRACK OVER THE CENTRAL PHILIPPINE ISLAND OF LUZON
JUST SOUTH OF MANILA, AND REEMERGE INTO THE SOUTH CHINA SEA BY
TAU 12. ALL GUIDANCE INDICATES A GENERAL WEST-NORTHWEST TRACK
THROUGH TAU 36. HOWEVER, BY TAU 48, MODEL GUIDANCE INDICATES THE
WESTERN SIDE OF THE STR WILL ERODE AND WEAKEN AHEAD OF AN
APPROACHING MID-LATITUDE TROUGH, WHICH WILL ALLOW THE SYSTEM TO
BEGIN TO TURN AND TRACK NORTHWARD. THE SYSTEM WILL CONTINUE
NORTHWARD THROUGH TAU 96, BEFORE TURNING NORTHWESTWARD AS THE
LOW-LEVEL WIND FLOW TAKES OVER AS THE MAIN STEERING FEATURE BY TAU
120. TS 26W IS FORECAST TO MAINTAIN INTENSITY OVER THE NEXT 12
HOURS, BEFORE STRENGTHENING UP TO 70 KNOTS BY TAU 36 AS THE SYSTEM
EMERGES INTO THE SCS. BETWEEN TAU 36 AND TAU 48 AN UPPER-LEVEL
POINT SOURCE ALOFT IS ANTICIPATED TO DEVELOP ALONG WITH WARM SSTS,
WHICH WILL ENABLE A PERIOD OF INTENSIFICATION UP TO 75 KNOTS,
POSSIBLY HIGHER. HOWEVER, COOLING SSTS, INCREASING VERTICAL WIND
SHEAR, ALONG WITH DRY AIR ENTRAINMENT WILL LEAD TO STEADY WEAKENING
TO TROPICAL DEPRESSION STRENGTH BETWEEN TAU 96 AND TAU 120.    

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 48. BY TAU 72 TRACK GUIDANCE BEGINS TO
INCREASE IN CROSS TRACK SPREAD, HOWEVER, GUIDANCE NOW SHOWS LESS OF
A BIFURCATION WITH MOST OF THE GUIDANCE SHOWING A GENERAL TURN
TOWARD THE NORTHWEST THROUGH TAU 120. THE AVNI (GFS) TRACKER
SPECIFICALLY NOW SHOWS A TRACK NORTHWESTWARD BY THE END OF THE
FORECAST AS OPPOSED TO A RECURVE SCENARIO. THE ENSEMBLE MEMBERS IN
BOTH OF GEFS AND ECENS SHOW A WIDE CROSS-TRACK SPREAD, HOWEVER,
BOTH THE ENSEMBLE MEAN'S GENERALLY AGREE ON A SIMILAR OVERALL TRACK
THROUGH TAU 120. THEREFORE, THE JTWC TRACK FORECAST IS PLACED WITH
MEDIUM CONFIDENCE. THE RELIABLE INTENSITY GUIDANCE REMAINS MIXED,
WITH AHNI (GFS), AND DECAY SHIPS (NAVGEM AND GFS) REPRESENTING THE
HIGH END OF INTENSITY GUIDANCE, WHILE CTCI, COTI REPRESENTS THE LOW
END OF INTENSITY GUIDANCE. ADDITIONALLY, GEFS CONTINUES TO SHOW
MODEST PROBABILITIES OF MODERATE INTENSIFICATION OVER THE NEXT 48
HOURS. THE JTWC INTENSITY FORECAST IS PLACED WITH MEDIUM CONFIDENCE
AND LIES CLOSE TO THE AVHI (GFS) SOLUTION AND ABOVE THE CONSENSUS
MEAN.    

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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