WDPN31 PGTW 030900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 12W (YAGI) WARNING NR 
008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.5N 119.1E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 258 NM NORTH-NORTHWEST OF MANILA,
PHILIPPINES
   MOVEMENT PAST 6 HOURS: WESTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 17 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS BUILDING
DEEP CONVECTIVE BANDS WRAPPING INTO AN OBSCURED LOW-LEVEL
CIRCULATION CENTER (LLCC). DRY AIR WRAPS INTO THE LLCC FROM THE
NORTHEAST SOURCED FROM LUZON. WATER VAPOR IMAGERY REVEALS STRONG
POLEWARD OUTFLOW INTO AN UPPER-LEVEL CYCLONE POSITIONED TO THE
EAST-NORTHEAST AND STRONG EQUATORWARD OUTFLOW INTO NORTHEASTERLY
UPPER-LEVEL FLOW TO THE SOUTH. 030502Z GCOM W1 AMSR2 IMAGERY
SUPPORTS POSITIONING BY ENHANCING THE LLCC ON THE 37GHZ IMAGE AND
DEPICTING THE UPPER-LEVEL BANDING AND DRY AIR ENTRAINMENT ON THE
89GHZ IMAGE. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE
BASED ON THE AFOREMENTIONED MICROWAVE IMAGERY AND ANIMATED MSI. THE
INITIAL INTENSITY OF 40 KTS IS ASSESSED WITH HIGH CONFIDENCE BASED
ON A 030502Z GCOM W1 AMSR2 REVEALING 40-45KT WINDS TO THE
SOUTHEAST, EXCLUDING WHAT APPEARS TO BE RAIN CONTAMINATION DIRECTLY
TO THE SOUTH.

INITIAL WIND RADII BASIS: AMSR2 DATA

CURRENT STEERING MECHANISM: A SUBTROPICAL RIDGE (STR) TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T3.0 - 45 KTS
   RJTD: T3.0 - 45 KTS
   RCTP: T3.5 - 55 KTS
   KNES: T3.0 - 45 KTS
   CIMSS SATCON: 46 KTS AT 030531Z
   CIMSS ADT: 39 KTS AT 030530Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: HIGHLY FAVORABLE
   VWS: 0-5 KTS
   SST: 31-32 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TS 12W WILL CONTINUE TO BE DRIVEN IN A
GENERALLY WESTWARD DIRECTION BY AN ELONGATED AND ASYMMETRIC STR
POSITIONED TO THE NORTH THROUGH TAU 48. BETWEEN TAU 48-72, TS 12W
WILL BEGIN TO CURVE AROUND RIDGE, TAKING THE TRACK
WEST-NORTHWESTWARD THROUGH THE END OF THE FORECAST PERIOD. THE
ENVIRONMENT WILL REMAIN HIGHLY FAVORABLE FOR RAPID INTENSIFICATION
WITH LOW VERTICAL WIND SHEAR, STRONG UPPER-LEVEL DIVERGENCE, HIGH
SEA SURFACE TEMPERATURES (31-32C), AND HIGH OCEAN HEAT CONTENT
THROUGH TAU 60, WHEN THE SYSTEM WILL REACH AN ANTICIPATED PEAK OF
105 KTS. AT TAU 72, VERTICAL WIND SHEAR WILL INCREASE TO 15-20KTS
AS IT APPROACHES LAND, INITIATING WEAKENING THAT WILL CONTINUE AS
THE SYSTEM PASSES BRIEFLY OVER HAINAN AND ULTIMATELY MAKES LANDFALL
IN MAINLAND CHINA BETWEEN TAU 96-120.

MODEL DISCUSSION: DETERMINISTIC MODEL GUIDANCE IS IN TIGHT
AGREEMENT THROUGH TAU 48 BUT BEGINS TO SPREAD AS TS 12W BEGINS TO
ROUND THE RIDGE AND TRACK WEST-NORTHWESTWARD. THE JTWC MULTI-MODEL
CONSENSUS SOLUTIONS AGREE CLOSELY IN TERMS OF TRACK SPEED, BUT THE
MAGNITUDE OF THE CURVE NORTHWARD VARIES AND OPENS THE TRACK SPREAD
TO 340NM BY TAU 120, WITH GSM TO THE NORTH AND ECMWF TO THE SOUTH.
THE JTWC INTENSITY GUIDANCE IS IN GOOD AGREEMENT THAT THE SYSTEM
WILL HAVE A PEAK INTENSITY OF 85-105KTS AT TAU 60. THE INDICATIONS
OF RAPID INTENSIFICATION TO A PEAK OF 105KTS BY TAU 72 ARE
HIGHLIGHTED BY FRIA AND RICN, WHICH PICKED UP ON THE HIGHLY
FAVORABLE ENVIRONMENT MENTIONED IN THE FORECAST DISCUSSION.

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