WDPN31 PGTW 250900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (THIRTYTHREE) 
WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.0N 121.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 216 NM SOUTH OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 11 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS TROPICAL
STORM 33W WITH IMPROVING DEEP CONVECTION BUILDING OVER THE CENTER
OF THE OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC). A 250503Z
AMSR2 89 GHZ MICROWAVE IMAGE REVEALED TIGHTLY CURVED CONVECTIVE
BANDING BEGINNING TO FORM NEAR THE ASSESSED CENTER. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE AMSR2
MICROWAVE IMAGE AND THE ANIMATED MSI. THE INITIAL INTENSITY OF 35
KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE COMBINATION OF
THE AGENCY DVORAK FIXES AND CIMSS OBJECTIVE ESTIMATES LISTED BELOW.
ENVIRONMENTAL ANALYSIS INDICATES THAT 33W IS IN A FAVORABLE
ENVIRONMENT CHARACTERIZED BY STRONG POLEWARD AND EQUATORWARD
OUTFLOW ALOFT, LOW (10-15 KTS) SOUTHEASTERLY VERTICAL WIND SHEAR,
AND WARM (28-29 C) SEA SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF AN ELONGATED
DEEP-LAYER SUBTROPICAL RIDGE POSITIONED TO THE NORTHEAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 38 KTS AT 250530Z
   CIMSS ADT: 34 KTS AT 250600Z
   CIMSS AIDT: 30 KTS AT 250600Z
   CIMSS D-MINT: 40 KTS AT 250530Z
   CIMSS D-PRINT: 34 KTS AT 250600Z

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

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   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: 33W IS FORECAST TO CONTINUE TRACKING
WEST-NORTHWESTWARD ALONG THE SOUTHWESTERN PERIPHERY OF THE
SUBTROPICAL RIDGE TO THE NORTHEAST THROUGH TAU 24. NEAR TAU 24, 33W
WILL ENTER AN AREA OF WEAK STEERING INFLUENCE, CAUSING TRACK SPEEDS
TO QUICKLY DECREASE. THE SYSTEM WILL BE PLACED BETWEEN RIDGING TO
BOTH THE EAST AND WEST AS A MAJOR SHORTWAVE TROUGH DIGS IN FROM THE
NORTH. AS A RESULT, SLOW WESTWARD MOVEMENT IS FORECAST FROM TAU
24-72. AFTER TAU 72, RIDGING IS EXPECTED TO BUILD BACK IN OVER THE
NORTHERN PHILIPPINES, CAUSING 33W TO DRIFT NORTHWESTWARD THROUGH
THE REMAINDER OF THE FORECAST PERIOD. REGARDING INTENSITY, 33W IS
FORECAST TO QUICKLY INTENSIFY THROUGH TAU 24 TO AROUND 55 KTS AS
SHEAR REMAINS LOW AND THE SYSTEM KEEPS A DISTANCE FROM THE
NORTHEASTERLY SURGE. FROM TAU 24 TO TAU 48, INTENSIFICATION IS
EXPECTED TO CONTINUE, BUT AT A SLOWER PACE AS SOUTHERLY SHEAR
INCREASES AND DRY AIR FROM THE SURGE BEGINS TO IMPACT THE VORTEX.
FROM TAU 48 TO 96, SLIGHT WEAKENING IS FORECAST TO OCCUR AS THE DRY
AIR CONTINUES TO PENETRATE THE VORTEX. AFTER TAU 96, SHEAR AND DRY
AIR ARE FORECAST TO LESSEN AS THE NORTHEASTERLY SURGE RETREATS.
REINTENSIFICATION IS POSSIBLE NEAR THE VERY END OF THE FORECAST
PERIOD AS THE ENVIRONMENT BECOMES MORE FAVORABLE. 

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 72 WITH A 90 NM CROSS-TRACK SPREAD AT THAT
TIME. THERE IS SOME INCREASED ALONG-TRACK SPREAD THOUGH (AROUND 100
NM) AS THE MODELS DIFFER ON INTERACTION WITH THE WEAK STEERING
ENVIRONMENT. AFTER TAU 72, MODELS DIVERGE WITH SOME MODELS (JGSM
AND THE ECMWF ENSEMBLE MEAN) DIPPING THE TRACK FURTHER TO THE
SOUTHWEST WHILE THE REST OF GUIDANCE KEEPS A MORE WESTWARD TRACK.
MODELS DO GENERALLY AGREE ON A NORTHWESTWARD TURN AFTER TAU 96, BUT
CROSS-TRACK SPREAD INCREASES TO AROUND 150 NM AT TAU 120. THE JTWC
TRACK FORECAST IS PLACED SLIGHTLY NORTH OF THE MULTI-MODEL
CONSENSUS WITH HIGH CONFIDENCE THROUGH TAU 72 AND MEDIUM CONFIDENCE
THEREAFTER. INTENSITY GUIDANCE IS SPLIT THROUGH TAU 48 BETWEEN RAPID
INTENSIFICATION (RI) AIDS AND NON-RI AIDS. THE RI AIDS SUGGEST A
CONSIDERABLY QUICKER RATE OF INTENSIFICATION THROUGH TAU 48 WITH
MULTIPLE MODELS SUGGESTING 85-95 KTS WHILE THE NON-RI AIDS ARE ALL
AROUND 55-65 KTS. THE JTWC INTENSITY FORECAST IS PLACED ON THE HIGH
END OF THE NON-RI AIDS WITH LOW CONFIDENCE THOUGH TAU 72. AFTER TAU
72 THERE IS ONE SIGNIFICANT OUTLIER, HAFS-A WHICH SUGGESTS RI AFTER
TAU 96 TO AN INTENSITY OF AROUND 90 KTS AT TAU 120. THE REMAINDER
OF GUIDANCE HAS EITHER STEADY WEAKENING OR A FLAT INTENSITY THROUGH
THE SAME TIME PERIOD. THE JTWC INTENSITY FORECAST IS PLACED CLOSER
TO THE BULK OF GUIDANCE AFTER TAU 72 WITH LOW CONFIDENCE DUE TO THE
POSSIBILITY OF RAPID DEVELOPMENT NEAR THE END OF THE FORECAST
PERIOD.

FORECAST CONFIDENCE:
   TRACK 00-72 HR: HIGH
   TRACK 72-120 HR: MEDIUM
   INTENSITY 00-72 HR: LOW
   INTENSITY 72-120 HR: LOW//
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