WDPN33 PGTW 221500
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 27W (TWENTYSEVEN) 
WARNING NR 12//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
TROPICAL DEPRESSION 27W (TWENTYSEVEN), LOCATED APPROXIMATELY 351
NM SOUTHEAST OF ANDERSEN AFB, HAS TRACKED EAST-NORTHEASTWARD AT
04 KNOTS OVER THE PAST SIX HOURS. ANIMATED ENHANCED INFRARED 
SATELLITE IMAGERY DEPICTS WELL DEFINED AND FULLY EXPOSED LOW 
LEVELCIRCULATION CENTER (LLCC), WITH FLARING CENTRAL CONVECTION 
BEING SHEARED TO THE WEST THAT HAS NOT CHANGED MUCH IN THE LAST SIX 
HOURS. THE INITIAL POSITION IS PLACED WITH HIGH CONFIDENCE BASED ON 
THE EXPOSED LLCC, AND WITH THE TRACK MOTION OVER THE LAST SIX HOURS 
SUGGESTS THE SOUTHEASTWARD DRIFT HAS STABILIZED. THE INITIAL 
INTENSITY IS ASSESSED AT 30 KNOTS WHICH IS BASED ON A 221054Z OSCAT 
IMAGE SHOWING A BROAD REGION OF 30 KNOT WINDS ON THE SOUTHWESTERN 
PERIPHERY. UPPER-LEVEL ANALYSIS SHOWS STRONG EASTERLIES FROM THE 
NORTHEAST RIDGE INDUCING A VERY UNFAVORABLE SHEAR ENVIRONMENT, BEING 
OFFSET BY MODERATE DIFFLUENCE. SSTS IN THE REGION ARE ALSO VERY 
FAVORABLE NEAR 30 CELSIUS, HOWEVER DUE TO THE HOSTILE UPPER-LEVEL 
CONDITIONS TD 27W HAS NOT SHOWN SIGNS OF FURTHER CONSOLIDATION. 
CURRENTLY TD 27W IS TRACKING ERRATICALLY WITHIN A COMPETING STEERING 
ENVIRONMENT POSITIONED BETWEEN A NEAR-EQUATORIAL RIDGE (NER) TO THE 
SOUTHWEST AND A SUBTROPICAL RIDGE (STR) TO THE NORTHEAST.
3. FORECAST REASONING.
   A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE.
   B. THE COMPETING STEERING ENVIRONMENT IS FORECAST TO PERSIST OVER 
THE NEXT 12 TO 24 HOURS AS THE NER WEAKENS RETREATING TO THE 
SOUTHWEST AND THE STR STRENGTHENS DRIVING TD 27W TO THE NORTHWEST. 
RECENT UPPER AIR SOUNDINGS FROM GUAM SHOW THE MID-TO LOW LEVEL WINDS 
SHIFTING TO A EASTERLY PATTERN. THIS COMBINED WITH A SLOWING TRACK 
MOTION SUGGEST THE SUBTROPICAL RIDGE IS STRENGTHENING AND BEGINNING 
TO TAKE HOLD. HOWEVER, AS THE STR STRENGTHENS, EASTERLY FLOW ALOFT 
WILL REMAIN FAIRLY STRONG WITH HIGH VERTICAL WIND SHEAR OVER THE 
NEXT 36 HOURS. THE SYSTEM WILL REMAIN A TROPICAL DEPRESSION TO WEAK 
TROPICAL STORM BEFORE UPPER-LEVEL CONDITIONS BEGIN TO IMPROVE 
SHORTLY AFTER TAU 36.
   C. IN THE EXTENDED PERIOD, TD 27W IS FORECAST TO CONTINUE 
NORTHWESTWARD SHIFTING TO A POLEWARD TRACK AROUND TAU 96. AS OUTFLOW 
IMPROVES TD 27W WILL GRADUALLY INTENSIFY REACHING A PEAK INTENSITY 
OF 70 KNOTS BY TAU 120. DYNAMIC MODEL GUIDANCE SHOWS GENERAL 
AGREEMENT ON THE SYSTEM ACCELERATING TO THE NORTHWEST SOMETIME IN 
THE NEXT 24 TO 36 HOURS, HOWEVER THERE IS A LARGE DEGREE OF 
UNCERTAINTY IN THE EXACT POSITION AND TIMING OF THE TURN. 
FURTHERMORE, THERE IS ALSO UNCERTAINTY IN THE EXTENDED TRACK LARGELY 
DEPENDENT ON THE SCALE OF INTENSIFICATION WHICH MODELS ARE MIXED. 
DUE TO THESE UNCERTAINTIES, THERE IS LOW CONFIDENCE IN THE FORECAST 
TRACK.//
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