WDPN31 PGTW 242100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 22W (TRAMI) WARNING NR 
018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 16.7N 119.0E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 171 NM NORTHWEST OF MANILA, PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 09 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS AN
EXPANDING CENTRAL DENSE OVERCAST (CDO) FULLY OBSCURING THE LLCC
BENEATH. THOUGH POLAR ORBITERS HAVE NOT BEEN COOPERATING, A PARTIAL
241406Z AMSUB 89GHZ MICROWAVE IMAGE DEPICTS STRONG BANDING TO THE
SOUTH OF THE LLCC WITH A LARGE FIELD OF LOW-LEVEL CLOUD LINES
THROUGHOUT THE SOUTH-CHINA SEA (SCS). A 241530Z SCATTEROMETERY PASS
SHOWS A DISCRETE LLCC JUST OFF THE WESTERN COAST OF LUZON WITH THE
STRONGEST WINDS INDICATED TO THE SOUTH OF THE CIRCULATION. BASED ON
THE QUALITY OR LACK THEREOF OF EIR, AMSUB AND SCATTEROMETERY
SATELLITE IMAGERY, THE INITIAL POSITION IS PLACED WITH LOW
CONFIDENCE. THE INITIAL INTENSITY OF 45 KTS IS ASSESSED WITH MEDIUM
CONFIDENCE BASED ON A RANGE OF INTENSITY ESTIMATES FROM AGENCY
DVORAKS SHOWING AS LOW AS 30KTS TO CIMSS DPRINT UP AT 50KTS.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: COMBINED STEERING INFLUENCE OF THE
NEAR-EQUITORIAL RIDGE (NER) TO THE SOUTHEAST AND A SUBTROPICAL
RIDGE (STR) TO THE NORTHEAST. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RCTP: T2.5 - 35 KTS
   DEMS: T2.0 - 30 KTS
   CIMSS SATCON: 46 KTS AT 241800Z
   CIMSS ADT: 37 KTS AT 241420Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: LOW
   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: TS 22W IS FORECASTED TO CONTINUE WESTWARD
UNDER THE COMBINED STEERING INFLUENCES OF A NER TO THE SOUTHEAST
AND A STR TO THE NORTHEAST. WHILE THE OVERALL ENVIRONMENT IS
CHARACTERIZED AS GENERALLY FAVORABLE, PERSISTENT MID-UPPER LEVEL
VERTICAL WIND SHEAR IS FORECASTED TO PREVENT 22W FROM SIGNIFICANTLY
INTENSIFYING. OVER THE NEXT 36 HOURS THE SYSTEM WILL STILL CLIMB TO
55KTS AND POSSIBLY HIGHER AS IT TRANSITS THE BASIN. NEAR TAU 48, A
PASSING MID-LATITUDE TROUGH BREAKS DOWN THE STR WHILE AT THE SAME
TIME THE NER RIDGE IS BUILDING. THE RESULT OF THESE ATMOSPHERIC 
FORCINGS IS THAT 22W IS FORECASTED TO MAKE AN ABOUT-FACE THROUGH TAU 
96 AND STEADY UP ON A RECIPROCAL COURSE, AND TRACK EASTWARD INTO THE 
SCS. THROUGH THE ENTIRE COURSE CHANGE, VERTICAL WIND SHEAR CONTINUES 
TO INCREASE, RESULTING IN A STEADY WEAKENING TREND THROUGH TAU 120.

MODEL DISCUSSION: NUMERICAL MODELS ARE IN NEAR TOTAL AGREEMENT THAT
22W WILL APPROACH VIETNAM BEFORE TURNING SOUTH AND EVENTUALLY
EASTWARD THROUGH TAU 120. THE TIMING AND NATURE OF THIS TURN IS NOT
AGREED UPON HOWEVER. FOR THIS REASON, THE INITIAL JTWC TRACK
FORECAST IS PLACED WITH HIGH CONFIDENCE AND WITH LOW CONFIDENCE
THEREAFTER. RELIABLE MODEL INTENSITY GUIDANCE INDICATES GRADUAL
INTENSIFICATION THROUGH TAU 36 AND STEADY WEAKENING THEREAFTER. THE
TRACK GUIDANCE HAS AN IMMENSE IMPACT ON THE INTENSITY FORECAST DUE
TO THE UNKNOWN EXTENT OF LAND INTERACTION, BECAUSE OF THIS, THE
JTWC FORECAST INTENSITY IS PLACED INITIALLY WITH MEDIUM CONFIDENCE
AND WITH LOW CONFIDENCE THEREAFTER.

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