WDPN33 PGTW 131500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 16W (SIXTEEN) 
WARNING NR 004//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 22.5N 139.6E
   INITIAL INTENSITY: 30 KTS
   GEOGRAPHIC REFERENCE: 167 NM SOUTHWEST OF IWO TO
   MOVEMENT PAST 6 HOURS: NORTHEASTWARD AT 05 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A BROAD,
YET CONSOLIDATING, LOW LEVEL CIRCULATION (LLC) WHICH APPEARS TO BE
IMPROVING IN STRUCTURE WITH FLARING CONVECTION CONTINUING MAINLY IN
THE SOUTHERN SEMI-CIRCLE. UNFORTUNATELY THERE HAS BEEN A LACK OF
USABLE MICROWAVE DATA DURING THIS WARNING CYCLE FOR TD 16W. A
PARTIAL SCATTEROMETER PASS DOES INDICATE THE SYSTEM IS STARTING TO
SHOW A MORE DEFINED CORE, ALBEIT ONLY HALF OF THE LLCC IS VISIBLE.
THE ENVIRONMENT IS MARGINALLY FAVORABLE FOR FURTHER DEVELOPMENT
WITH LOW (10-15 KTS) VERTICAL WIND SHEAR (VWS), AND WARM (29-30)
SEA SURFACE TEMPERATURES (SSTS), OFFSET BY VERY WEAK RADIAL OUTFLOW
ALOFT. THE SYSTEM CONTINUES TO DRIFT NORTHEASTWARD UNDER A 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: T2.0 - 30 KTS
   RJTD: T2.0 - 30 KTS
   KNES: T2.0 - 30 KTS
   CIMSS SATCON: 31 KTS AT 130436Z
   CIMSS ADT: 35 KTS AT 131140Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 10-15 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: WEAK RADIAL

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: NOT APPLICABLE

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 35 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 45 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 50 KTS AS THE ENVIRONMENT WILL CONTINUE
TO IMPROVE. BY TAU 48, TD 16W WILL REACH AN INTENSITY OF 60 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 KYUSHU.


MODEL DISCUSSION: THERE IS MORE OF A DISAGREEMENT IN THE TRACK
FORECAST GUIDANCE THAN IN THE PREVIOUS MODEL RUNS. THE DISAGREEMENT
OCCURS MAINLY AFTER TAU 72 WHERE GFS AND ECM2 TAKE THE SYSTEM MORE
NORTHWESTWARD OVER THE EAST CHINA SEA AND NOT NORTHWARD AS
PREVIOUSLY INDICATED. ALL OF THE OTHER CONSENSUS MEMBERS HAVE TD
16W TURNING TOWARDS KYUSHU. BECAUSE OF THIS, THERE IS A 216NM
SPREAD IN THE CONSENSUS MEMBERS BY TAU 120. SINCE THIS IS THE FIRST
MODEL RUN TO SHOW THIS BIFURCATION, THE JTWC FORECAST TRACK IS SET
WITH LOW CONFIDENCE PAST TAU 72. 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: HIGH
   TRACK 72-120 HR: LOW
   INTENSITY 0 - 72 HR: MEDIUM
   INTENSITY 72-120 HR: LOW//
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