WDPN31 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 16W (SIXTEEN) WARNING 
NR 018//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 12.3N 159.0E
   INITIAL INTENSITY: 35 KTS
   GEOGRAPHIC REFERENCE: 828 NM EAST OF ANDERSEN AFB
   MOVEMENT PAST 6 HOURS: WESTWARD AT 13 KTS
   SIGNIFICANT WAVE HEIGHT: 14 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED MULTISPECTRAL SATELLITE IMAGERY (MSI) DEPICTS DEEP
CONVECTION FLARING OVER A BROAD, PARTIALLY-EXPOSED LOW-LEVEL
CIRCULATION (LLC). DUE TO THE LACK OF MICROWAVE IMAGERY AND THE
BROAD NATURE OF THE LLC, THERE IS LOW CONFIDENCE IN THE INITIAL
POSITION. ALTHOUGH VERTICAL WIND SHEAR VALUES ARE LOW, DIFFLUENT
UPPER-LEVEL EASTERLY FLOW OF 20-30 KNOTS OFFSET BY MODERATE
WESTWARD OUTFLOW, ENHANCED BY A TUTT CELL TO THE NORTHWEST, AND DRY
AIR ENTRAINMENT ARE HINDERING SUSTAINED CONVECTION AND LIMITING 
DEVELOPMENT. THE INITIAL INTENSITY OF 35 KTS IS ASSESSED WITH LOW 
CONFIDENCE BASED ON THE PGTW AND KNES DVORAK ESTIMATES.

INITIAL WIND RADII BASIS: PERSISTENCE 

CURRENT STEERING MECHANISM: DEEP-LAYERED SUBTROPICAL RIDGE (STR)
ENTRENCHED 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: 50 KTS AT 141442Z
   CIMSS ADT: 57 KTS AT 141740Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: MARGINALLY FAVORABLE
   VWS: 5-10 KTS
   SST: 29-30 CELSIUS
   OUTFLOW: MODERATE WESTWARD
   OTHER FACTORS: DRY AIR ENTRAINMENT

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

3. FORECAST REASONING.

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

FORECAST DISCUSSION: TD 16W IS EXPECTED TO TRACK WESTWARD ALONG THE
SOUTHERN PERIPHERY OF THE STR THROUGH TAU 72 THEN TURN WEST-
NORTHWESTWARD THROUGH TAU 120 AS IT TRACKS ALONG THE SOUTHWEST
PERIPHERY OF THE STR. TD 16W SHOULD EVENTUALLY BEGIN STRENGTHENING
AFTER 36 TO 48 HOURS AS INDICATED IN THE BULK OF THE INTENSITY
GUIDANCE WITH A STEADY INTENSIFICATION TREND AFTER TAU 72 WITH A
PEAK INTENSITY OF 75 KNOTS ANTICIPATED BY TAU 120. 


MODEL DISCUSSION: THERE IS SIGNIFICANT UNCERTAINTY (MEDIUM OVERALL)
IN THE EXACT TRACK WITH A SPREAD OF 120NM AT TAU 60 NEAR GUAM. DUE
TO THE BROAD NATURE OF THE LLC, THERE IS ADDITIONAL UNCERTAINTY IN
THE INITIAL POSITION OF THIS BROAD LLC, WHICH COULD LEAD TO MINOR
SHIFTS IN THE TRACK AS THE SYSTEM STRUGGLES TO CONSOLIDATE OVER THE
NEXT TWO DAYS. INTENSITY GUIDANCE IS IN FAIR AGREEMENT THROUGH TAU
36 BUT DIVERGES AFTER TAU 36 WITH HWRF INDICATING A PEAK INTENSITY
OF 110 KNOTS AT TAU 120 AND THE JTWC INTENSITY CONSENSUS INDICATING
A PEAK INTENSITY OF 80 KNOTS AT TAU 120. DUE TO THE MARGINALLY
FAVORABLE CONDITIONS AND BROAD NATURE OF THE SYSTEM, THIS FORECAST
IS SOMEWHAT CONSERVATIVE. OVERALL, THERE IS 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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