WDPN31 PGTW 140900
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SIXTEEN) WARNING 
NR 016//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3N 161.7E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 56 NM WEST-NORTHWEST OF ENEWETAK
   MOVEMENT PAST 6 HOURS: WESTWARD AT 15 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) INDICATES A FLARE UP
OF DEEP CONVECTION OBSCURING THE LOW LEVEL CIRCULATION CENTER
(LLCC). PREVIOUS ANIMATED IMAGERY SHOWED VERY DISORGANIZED AREAS OF
CONVECTION SCATTERED AROUND THE PERIPHERY OF THE LLCC, BUT THE MORE
RECENT CONVECTION IS MORE ORGANIZED AND MORE PERSISTENT. AGENCY FIX
POSITIONS AND EXTRAPOLATION OF A WELL-DEFINED LLCC IN A 140259Z
AMSR2 37 GHZ MICROWAVE IMAGE SUPPORTS THE INITIAL POSITION WITH
MEDIUM CONFIDENCE. THE INITIAL INTENSITY OF 35 KNOTS IS ASSESSED
WITH HIGH CONFIDENCE BASED ON AN OVERALL AVERAGE OF MULTI-AGENCY
SUBJECTIVE AND OBJECTIVE DVORAK INTENSITY ESTIMATES. CIMSS AMV
ANALYSIS AND ANIMATED WATER VAPOR IMAGERY INDICATES THE PRESENCE OF
A SMALL-SCALE UPPER-LEVEL POINT SOURCE OR ANTICYCLONE JUST WEST OF
TS 16W, WHICH IS HELPING THE SYSTEM TO FIGHT OFF PERSISTENT
NORTHEASTERLY FLOW AND ENABLING THE RECENT INTENSIFICATION.
ANIMATED WATER VAPOR IMAGERY ALSO DEPICTS THE PRESENCE OF A TUTT
CELL ABOUT 750 NM TO THE NORTHWEST, JUST CLOSE ENOUGH TO SUPPORT A
WEAK POLEWARD OUTFLOW CHANNEL.

INITIAL WIND RADII BASIS: OBJECTIVE BEST TRACK. 

CURRENT STEERING MECHANISM: SOUTHERN PERIPHERY OF THE DEEP-LAYER
SUBTROPICAL RIDGE (STR) TO THE NORTH. 

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   RJTD: T1.0 - 25 KTS
   KNES: T2.5 - 35 KTS
   CIMSS SATCON: 41 KTS AT 140209Z
   CIMSS ADT: 57 KTS AT 140550Z

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

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TROPICAL STORM 16W IS CURRENTLY TRACKING
GENERALLY WESTWARD ALONG THE SOUTHERN PERIPHERY OF THE STR
ENTRENCHED TO THE NORTH. RECENT MOTION HAS BEEN SLIGHTLY SOUTH OF
DUE WEST, BUT OVERALL CONFIDENCE IN THIS VECTOR IS LOW IN LIGHT OF
THE MEDIUM CONFIDENCE IN THE INITIAL POSITION. THE STEERING PATTERN
IS NOT EXPECTED TO CHANGE, AND WHILE SOME MINOR DEVIATIONS NORTH
AND SOUTH OF DUE WEST CAN BE EXPECTED, THE OVERALL WESTWARD MOTION
IS FORECAST TO CONTINUE THROUGH TAU 72. AFTER THE SYSTEM PASSES TO
THE SOUTH OF GUAM NEAR TAU 72, IT IS EXPECTED TO TURN ONTO A MORE
NORTHWESTWARD TRACK AFTER TAU 72 AS THE STR CENTER MOVES WEST AND
REORIENTS TO A MORE NORTHWEST TO SOUTHEAST LINE. WHILE THE SYSTEM
APPEARS TO HAVE DEVELOPED A POINT SOURCE ALOFT OVER THE PAST TWELVE
HOURS, THIS IS NOT EXPECTED TO BE A LONG-LIVED FEATURE, WITH
MODERATE TO STRONG NORTHERLY FLOW MOVING IN BY TAU 24. IN LIGHT OF
THE SMALL SIZE OF TS 16W, IT SHOULD EXPERIENCE SOME DIFFICULTY IN
FIGHTING OFF THIS NORTHEASTERLY SHEAR, AND HENCE WILL BE CHALLENGED
TO INTENSIFY SIGNIFICANTLY THROUGH TAU 72. THEREAFTER, DECREASED
SHEAR, IMPROVED OUTFLOW AND A GENERALLY MOISTENING OF THE
ENVIRONMENT, WILL ENABLE MORE RAPID INTENSIFICATION THROUGH THE END
OF THE FORECAST. 

MODEL DISCUSSION: ALTHOUGH THE CONFIDENCE IN THE RECENT TRACK
MOTION LENDS SOME UNCERTAINTY TO THE OVERALL TRACK FORECAST,
NUMERICAL TRACK GUIDANCE IS IN VERY GOOD AGREEMENT WITH A 110 NM
SPREAD AT TAU 48 AND 160 NM AT TAU 72 AS THE SYSTEM PASSES SOUTH OF
GUAM. OF NOTE, THE ECMWF AND HWRF SOLUTIONS LIE APPROXIMATELY 80 NM
SOUTH OF THE TIGHTEST GROUPING OF GUIDANCE BETWEEN TAUS 48 AND 72
AS THE SYSTEM PASSES GUAM, AS BOTH HAVE A MUCH WEAKER SYSTEM AT
THIS TIME THAN THE REMAINDER OF THE GUIDANCE. AFTER TAU 72, ALL
TRACK GUIDANCE COMES INTO BETTER AGREEMENT WITH A 186 NM SPREAD AT
TAU 120. OVERALL, THE JTWC FORECAST TRACK LIES ON THE SOUTHERN EDGE
OF THE TIGHTEST GROUPING OF GUIDANCE, AND SOUTH OF THE CONSENSUS
THROUGH THE FORECAST PERIOD WITH MEDIUM CONFIDENCE. INTENSITY
GUIDANCE SHOWS A MASSIVE DISCONTINUITY, LENDING VERY LOW CONFIDENCE
TO THE JTWC FORECAST. THE RAPID INTENSITY PREDICTION AID (RIPA) HAS
BEEN TRIGGERED, AND INDICATES A 100 KNOT SYSTEM BY TAU 72, WHILE
THE COAMPS-TC INDICATES A 25 KNOT DEPRESSION AT THE SAME TIME. 
HWRF FAVORS A STEADY STATE THROUGH TAU 60, THEN A RAPID
INTENSIFICATION THEREAFTER, PEAKING AT 125 KNOTS BY TAU 120 AND THE
SHIPS GUIDANCE PACKAGE ALSO SUPPORTS A STEADY INTENSIFICATION TO A
PEAK AROUND 85 KNOTS BY TAU 120. THE JTWC FORECAST LIES ABOVE THE
BULK OF THE GUIDANCE, WITH THE EXCEPTION OF SHIPS AND RIPA, AND
SHOWS STAIR-STEP INTENSIFICATION THROUGH TAU 72, AND MORE RAPID
INTENSIFICATION THEREAFTER, CLOSER TO THE CONSENSUS MEAN. THIS
FORECAST REMAINS CONSISTENT WITH THE PREVIOUS FORECAST AND IS
SOMEWHAT CONSERVATIVE. DUE TO THE VERY LARGE UNCERTAINTY IN THE
GUIDANCE THERE IS OVERALL LOW CONFIDENCE IN THE INTENSITY FORECAST.


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