WDPN33 PGTW 130900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN) 
WARNING NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.1N 139.2E
   INITIAL INTENSITY: 25 KTS
   GEOGRAPHIC REFERENCE: 199 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 13 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS A BROAD LOW
LEVEL CIRCULATION (LLC) WITH DISORGANIZED FLARING CONVECTION
PREDOMINATELY IN THE SOUTHERN SEMI-CIRCLE. A PARTIAL 130421Z AMSR2
37GHZ MICROWAVE PASS SHOWS RUGGED, CONVECTIVE BANDING WRAPPING INTO
A LOW LEVEL CIRCULATION CENTER (LLCC). THE INITIAL POSITION AND
INTENSITY ARE BOTH PLACED WITH HIGH CONFIDENCE BASED ON
MULTI-AGENCY FIXES AND A PARTIAL 130601Z SSMIS 37 GHZ MICROWAVE
PASS WHICH SHOWS THE LLCC ON THE EDGE OF THE PASS. THE ENVIRONMENT
IS MARGINALLY FAVORABLE FOR FURTHER DEVELOPMENT WITH LOW (05-10
KTS) VERTICAL WIND SHEAR (VWS), AND WARM (29-30) SEA SURFACE
TEMPERATURES (SSTS), OFFSET BY VERY WEAK RADIAL OUTFLOW ALOFT. THE
SYSTEM IS NOW DRIFTING NORTHEASTWARD UNDER THE AFOREMENTIONED WEAK
STEERING ENVIRONMENT.

INITIAL WIND RADII BASIS: NOT APPLICABLE (THERE ARE NO INITIAL WIND
RADII).

CURRENT STEERING MECHANISM: THE SUBTROPICAL RIDGE (STR) TO THE
NORTH AND THE NEAR EQUATORIAL RIDGE (NER) TO THE SOUTH.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T1.5 - 25 KTS
   RJTD: T1.5 - 25 KTS
   KNES: T1.5 - 25 KTS
   CIMSS SATCON: 30 KTS AT 130347Z
   CIMSS ADT: 31 KTS AT 130230Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 0-5 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: HIGH
   INITIAL INTENSITY: HIGH
   
3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 16W CONTINUES ITS DANCE BETWEEN TWO
COMPETING STEERING MECHANISMS. THERE IS THE SUBTROPICAL RIDGE (STR)
SITTING TO THE NORTH AND THE NEAR EQUATORIAL RIDGE (NER) LYING TO
THE SOUTH. AS IN THE PREVIOUS PROGNOSTIC REASONING, THE NER IS IN A
SLIGHTLY BETTER POSITION AND CURRENTLY CAUSING TD 16W TO PURSUE A
MORE NORTHEASTWARD TRACK. ON OR ABOUT TAU 12, TD 16W WILL TAKE A
TURN POLEWARD AND INCREASE IN INTENSITY TO 30 KTS. BY TAU 24, TD
16W WILL HEAD ON A MORE WEST-NORTHWESTWARD TRACK AS THE NER BEGINS
TO SUBSIDE AND THE STR TO THE NORTH BECOMES THE DOMINANT STEERING
MECHANISM. AT THIS TIME, THE SYSTEM WILL INCREASE TO 35 KTS IN
INTENSITY. BY TAU 36, THE SYSTEM WILL CONTINUE ITS
WEST-NORTHWESTWARD TRACK ALONG THE SOUTHWEST PERIPHERY OF THE STR
AND REACH AN INTENSITY OF 45 KTS AS THE ENVIRONMENT WILL CONTINUE
TO IMPROVE. BY TAU 48, TD 16W WILL REACH AN INTENSITY OF 55 KTS AND
WILL GRADUALLY PICK UP TRACK SPEED. BY TAU 72, TD 16W WILL REACH AN
INTENSITY OF 75 KTS, AT THE SAME TIME, A MAJOR SHORTWAVE TROUGH
WILL PASS TO THE NORTH AND WEAKEN THE STR. THIS IS CAUSE TD 16W TO
MAKE THE SHIFT MORE NORTHWESTWARD, THEN FINALLY MORE NORTHERLY
AFTER TAU 96 WHERE TD 16W IS FORECAST TO REACH ITS PEAK INTENSITY
OF 95 KTS AS IT HEADS FOR THE NORTHERN RYUKYU ISLANDS. BY TAU 120,
THERE WILL BE A SLIGHT DECREASE IN INTENSITY TO 90 KTS DUE TO LAND
INTERACTION WITH SOUTHERN JAPAN.


MODEL DISCUSSION: THERE CONTINUES TO BE A FAIRLY TIGHT AGREEMENT IN
BOTH TRACK FORECAST GUIDANCE AND INTENSITY GUIDANCE. FOR THE TRACK
FORECAST, NAVGEM WAS THE OUTLIER SHOWING A MORE SWEEPING MOTION
EASTWARD THAN THE OTHER CONSENSUS MEMBERS IN THE ENVELOPE. IT IS
FOR THIS REASON THE JTWC FORECAST TRACK WAS PLACED SLIGHTLY LEFT OF
CONSENSUS. THE INTENSITY GUIDANCE CONTINUES TO SHOW A GRADUAL
INCREASE AS TD 16W STRUGGLES TO FIND A GOOD OUTFLOW MECHANISM. THE
ENVIRONMENT WILL IMPROVE AS TD 16W BEGINS ITS WEST-NORTHWESTWARD
TRACK. HOWEVER, AS PREVIOUSLY FORECAST, THIS WILL BE A RELATIVELY
SLOW PROCESS. WITH THAT, THE JTWC FORECAST INTENSITY WAS PLACED
SLIGHTLY LOWER THAN CONSENSUS, AND THEN MORE ALIGNED WITH CONSENSUS
AFTER TAU 48. DUE TO THE UNCERTAINTY OF THE TIMING OF THE IMPROVING
ENVIRONMENT, THERE IS LOW CONFIDENCE IN THE FORECAST INTENSITY PAST
TAU 72.

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