WDPN33 PGTW 141500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (NANMADOL) 
WARNING NR 008//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.9N 140.5E
   INITIAL INTENSITY: 45 KTS
   GEOGRAPHIC REFERENCE: 122 NM SOUTH-SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: WESTWARD AT 01 KTS
   SIGNIFICANT WAVE HEIGHT: 18 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A
CONSOLIDATING SYSTEM WITH DEFINED FEEDER BANDS WRAPPING INTO AN
ASSESSED LOW LEVEL CIRCULATION CENTER (LLCC) WITH PLUMES OF
CONVECTIVE ACTIVITY THROUGHOUT THE SYSTEM. FURTHER SATELLITE
ANALYSIS REVEALS THAT TS 16W IS MAKING THE SLOW WESTWARD TURN IN
ITS TRACK. ANOTHER INDICATION OF THIS TURN IS THE RISE OF STATION
PRESSURE FROM 999MB TO 1000MB ON THE ISLAND OF IWO TO WHICH IS
122NM TO THE NORTH-NORTHEAST OF THE SYSTEM. IN ADDITION, RECENT
SSMIS AND GMI PASSES WERE DIRECT HITS AND SHOW THAT TS 16W STALLED
BEFORE MAKING THE EVER SO SLIGHT JOG TO THE WEST. THE 140858Z SSMIS
91GHZ PASS SHOWS THE AFOREMENTIONED FEEDER BANDS AND STEADY
CONVECTIVE ACTIVITY IN THOSE BANDS, MAINLY IN THE EASTERN AND
SOUTHERN PERIPHERIES. THE ENVIRONMENT IS MARGINALLY FAVORABLE FOR
FURTHER DEVELOPMENT WITH LOW (05-10 KTS) VERTICAL WIND SHEAR (VWS),
AND WARM (29-30C) SEA SURFACE TEMPERATURES (SSTS), OFFSET BY WEAK
RADIAL OUTFLOW ALOFT. HOWEVER, THE OUTFLOW DOES SHOW SIGNS OF
IMPROVEMENT.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: THE SUBTROPICAL RIDGE TO THE NORTH

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T3.0 - 45 KTS
   KNES: T4.0 - 65 KTS
   CIMSS SATCON: 42 KTS AT 140859Z
   CIMSS ADT: 37 KTS AT 141140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK RADIAL
   OTHER FACTORS: DEEP TROPICAL MOISTURE INFLOW

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   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: THE SUBTROPICAL RIDGE (STR) TO THE NORTH IS
NOW THE DOMINANT STEERING MECHANISM. AS A RESULT, TS NANMADOL WILL
CONTINUE TO RIDE THE SOUTHWEST PORTION OF THE STR. BY TAU 12, TS
16W WILL INCREASE IN INTENSITY TO 55 KTS AND LATER INCREASE TO 70
KTS BY TAU 24. BY TAU 36, THE SYSTEM WILL BEGIN TO TAKE A MORE
NORTHWESTWARD HEADING AS THE STR WILL WEAKEN DUE TO AN APPROACHING
MAJOR SHORT WAVE TROUGH FROM THE WEST. AT THIS TIME, THE INTENSITY
WILL INCREASE TO 85 KTS. BY TAU 48, TS 16W WILL CONTINUE MAKING A
NORTHWESTWARD TURN AND INCREASE IN INTENSITY TO 95 KTS. THE PEAK
INTENSITY OF 105 KTS WILL BE REACHED AT TAU 72 AS TS NANMADOL
ROUNDS THE RIDGE AXIS AND HEADS NORTH-NORTHWESTWARD. BY TAU 96, THE
SYSTEM WILL BEGIN TO DECREASE IN INTENSITY TO 80 KTS AS IT WILL
BEGIN TO FEEL THE AFFECTS OF LAND INTERACTION WITH KYUSHU. BY TAU
120, THERE WILL BE ANOTHER DECREASE IN INTENSITY TO 55 KTS DUE TO
THE FURTHER LAND INTERACTION.

MODEL DISCUSSION: THE TRACK MODEL CONSENSUS MEMBERS REMAIN IN TIGHT
AGREEMENT THROUGH TAU 72, GRADUALLY INCREASING TO A 68 NM SPREAD.
BY TAU 96 THE CONSENSUS SPREAD INCREASES GREATLY TO A 220 NM
SPREAD. TAU 120 DISPLAYS A BIFURCATION IN TRACK SPEED WHERE MEMBERS
SUCH AS GFS AND ECMWF SLOW THE SYSTEM DOWN OVER SOUTHWEST JAPAN,
AND OTHER MEMBERS SUCH AS NAVGEM AND UKMET SPEED THE SYSTEM UP OVER
NORTHERN HONSHU. DUE TO THIS BIFURCATION, THE CONFIDENCE IN THE
TRACK FORECAST PAST TAU 72 REMAINS LOW. THE INTENSITY GUIDANCE
REVEALS RAPID INTENSIFICATION IS POSSIBLE OVER THE NEXT 36 HOURS AS
TS 16W MOVES INTO A MORE FAVORABLE ENVIRONMENT. WITH THAT, THE JTWC
FORECAST INTENSITY WAS PLACED HIGHER THAN CONSENSUS THROUGH TAU 72,
AND THEN MORE ALIGNED WITH CONSENSUS AFTER TAU 72. DUE TO THE
UNCERTAINTY RELATED TO THE AFOREMENTIONED BIFURCATION, THERE IS LOW
CONFIDENCE IN THE FORECAST INTENSITY PAST TAU 72.

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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