WDPN31 PGTW 251500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 33W (KOTO) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 11.4N 120.1E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 199 NM SOUTH-SOUTHWEST 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 ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM 33W (KOTO) WITH A COMPACT CORE OF DEEP CONVECTION THAT IS
TRACKING NEAR NORTHERN PALAWAN. CLOUD TOPS NEAR THE CENTER HAVE
CONTINUED TO COOL AND ARE NOW EXTREMELY COLD, MEASURING COLDER THAN
-95 C IN SOME AREAS. A 250948Z WSFM 37 GHZ MICROWAVE IMAGE REVEALED
A VERY SMALL FORMATIVE MICROWAVE EYE FEATURE WHILE THE 89 GHZ
VERSION OF THE SAME IMAGE SHOWED THE DEEP CONVECTION SLIGHTLY
OFFSET TO THE WEST OF THE LOW-LEVEL CIRCULATION CENTER (LLCC). THE
INITIAL POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON
EXTRAPOLATION FROM THE 37 GHZ WSFM MICROWAVE IMAGE. THE INITIAL
INTENSITY OF 40 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE
AGENCY DVORAK FIXES AND CIMSS OBJECTIVE INTENSITY 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) VERTICAL WIND SHEAR, AND WARM (28-29C) 
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: T2.5 - 35 KTS
   RJTD: T2.5 - 35 KTS
   KNES: T3.0 - 45 KTS
   DEMS: T2.5 - 35 KTS
   CIMSS ADT: 47 KTS AT 251200Z
   CIMSS AIDT: 40 KTS AT 251200Z
   CIMSS D-MINT: 30 KTS AT 250950Z
   CIMSS D-PRINT: 38 KTS AT 251200Z

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 CONTINUE INTENSIFYING THROUGH TAU 24 TO AROUND 55 KTS
AS SHEAR REMAINS LOW. FROM TAU 24 TO TAU 48, INTENSIFICATION IS
EXPECTED TO CONTINUE, BUT AT A MUCH SLOWER RATE 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 DRY AIR
ENTRAINS INTO THE CORE OF THE VORTEX. AFTER TAU 96, SHEAR AND DRY
AIR ARE EXPECTED 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 SOUTH
WHILE GFS STALLS THE SYSTEM. OTHER THAN GFS, 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 NEAR THE MULTI-MODEL CONSENSUS THROUGH TAU 72 WITH HIGH 
CONFIDENCE AND CLOSER TO THE GDM ENSEMBLE MEAN THROUGH TAU 120 AND 
MEDIUM CONFIDENCE. 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. AFTER TAU 72 THERE IS ONE SIGNIFICANT OUTLIER, 
HAFS-A, WHICH SUGGESTS INTENSIFICATION AFTER TAU 96 TO AN INTENSITY 
OF AROUND 70 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 NEAR THE HIGH END OF NON-RI 
AIDS THROUGH TAU 48 AND THEN SLIGHTLY HIGHER THAN THE CONSENSUS MEAN 
AFTERWARD WITH OVERALL LOW CONFIDENCE.

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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