WDPN31 PGTW 191500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 07W (SEVEN) WARNING NR 
004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 13.7N 140.2E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 274 NM WEST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WEST-NORTHWESTWARD AT 16 KTS
   SIGNIFICANT WAVE HEIGHT: 16 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS TROPICAL
STORM (TS) 07W WITH A DEVELOPING CENTRAL DENSE OVERCAST (CDO)
FEATURE AND ASSOCIATED OVERSHOOTING CLOUD TOPS MEASURING COLDER
THAN -90 C. THE OVERALL STRUCTURE OF THE CONVECTIVE MASS HAS
MARKEDLY IMPROVED OVER THE PAST 6 HOURS AND IS LIKELY INDICATIVE OF
THE BEGINNING OF AN EXPECTED INTENSIFICATION PHASE. THE INITIAL
POSITION IS PLACED WITH MEDIUM CONFIDENCE BASED ON THE MOSTLY
OBSCURED LOW-LEVEL CIRCULATION CENTER (LLCC) IN ANIMATED EIR
IMAGERY. THE ASSESSED CENTER IS ANALYZED TO BE PLACED UNDER THE
SOUTHWESTERN PORTION OF THE DEEP CONVECTION. THE INITIAL INTENSITY
OF 35 KTS IS ASSESSED WITH MEDIUM CONFIDENCE BASED ON THE AGENCY
DVORAK FIXES AND CIMSS INTENSITY ESTIMATES LISTED BELOW.
ENVIRONMENTAL ANALYSIS INDICATES THAT 07W IS IN A FAVORABLE
ENVIRONMENT CHARACTERIZED BY MODERATE EQUATORWARD OUTFLOW ALOFT,
LOW (5-10 KTS) VERTICAL WIND SHEAR, AND VERY WARM (30-31 C) SEA
SURFACE TEMPERATURES.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK 

CURRENT STEERING MECHANISM: SOUTHWESTERN PERIPHERY OF AN ELONGATED
SUBTROPICAL RIDGE (STR) 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 ADT: 37 KTS AT 191200Z
   CIMSS AIDT: 34 KTS AT 191200Z
   CIMSS D-MINT: 24 KTS AT 191001Z
   CIMSS D-PRINT: 26 KTS AT 191200Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 5-10 KTS
   SST: 30-31 CELSIUS
   OUTFLOW: MODERATE 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: TS 07W IS FORECAST TO TRACK
WEST-NORTHWESTWARD, ALONG THE SOUTHWESTERN PERIPHERY OF THE STR,
THROUGH TAU 72. AFTER TAU 72, 07W IS EXPECTED TO BEGIN A POLEWARD
TURN AS IT ROUNDS THE WESTERN EXTENT OF THE STR. HOWEVER,
SIMULTANEOUSLY TO THE POLEWARD TURN, A SEPARATE STR IS EXPECTED TO
BUILD OVER THE NORTHERN SOUTH CHINA SEA. THIS WILL CREATE A
COMPETING STEERING ENVIRONMENT AND WILL CAUSE 07W TO SLOW DOWN
CONSIDERABLY AS IT TRACKS SOUTHEAST OF TAIWAN THROUGH TAU 120.
REGARDING INTENSITY, 07W IS FORECAST TO STEADILY INTENSIFY OVER THE
NEXT 24 HOURS AS THE VORTEX BECOMES MORE SYMMETRIC AND VERTICALLY
ALIGNED. AFTER TAU 24, A MORE RAPID RATE OF INTENSIFICATION IS
EXPECTED AS SHEAR REMAINS LOW AND SEA SURFACE TEMPERATURES REMAIN
VERY WARM. RAPID INTENSIFICATION (RI) IS EXPLICITLY FORECAST TO OCCUR 
FROM TAU 24 TO TAU 72 (55 KTS TO 120 KTS). THE PEAK INTENSITY IS 
FORECAST TO OCCUR NEAR TAU 72 AS NORTHEASTERLY SHEAR GREATLY INCREASES
AFTERWARD. ADDITIONALLY, THE SLOW MOVEMENT SPEED NEAR THE END OF THE 
FORECAST PERIOD MAY ALLOW FOR THE UPWELLING OF COOLER WATERS. AS A 
RESULT, A WEAKENING TREND IS EXPECTED TO OCCUR AFTER TAU 72 AS THE 
SYSTEM COMMENCES ITS POLEWARD TURN.

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD
AGREEMENT THROUGH TAU 72 WITH THE EXCEPTION OF GALWEM AND UKMET,
WHICH TRACK THE SYSTEM STRAIGHT WESTWARD THROUGH TAU 36 RATHER THAN
WEST-NORTHWESTWARD. DISREGARDING THE TWO OUTLIERS, THERE IS A
CROSS-TRACK SPREAD OF 190 NM AT TAU 72. AFTER TAU 72, MODELS
GENERALLY AGREE ON THE POLEWARD TURN, BUT FAN OUT TO A CROSS-TRACK
SPREAD OF 305 NM AT TAU 120. THE GEFS ENSEMBLE MEAN CONTINUES TO
MAKE UP THE EASTERNMOST MODEL WHILE THE EC-AIFS NOW MAKES UP THE
WESTERNMOST. THE JTWC TRACK FORECAST IS PLACED CLOSE TO THE
MODIFIED CONSENSUS (REMOVING GALWEM AND UKMET) THROUGH TAU 72 AND
THEN SLIGHTLY TO THE WEST OF THE CONSENSUS THROUGH TAU 120 WITH
OVERALL MEDIUM CONFIDENCE. NEARLY ALL AVAILABLE INTENSITY GUIDANCE
AGREES ON A RAPID OR NEAR-RAPID RATE OF INTENSIFICATION THROUGH TAU
72 WITH A MULTITUDE OF RI AIDS TRIGGERING THIS MODEL RUN. HWRF AND
HAFS-A DEPICT A PEAK INTENSITY OF 115 KTS AND 130 KTS RESPECTIVELY
AT TAU 72. THE JTWC INTENSITY FORECAST IS PLACED NEAR THE HAFS-A,
WHICH IS SLIGHTLY BELOW THE BULK OF THE RI AIDS, THROUGHOUT THE
FORECAST PERIOD. CONFIDENCE IN THE INTENSITY FORECAST IS PLACED
WITH LOW CONFIDENCE DUE TO THE INHERENT UNCERTAINTIES REGARDING RI.

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