WDPN33 PGTW 220300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 27W (TWENTYSEVEN) 
WARNING NR 10//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL DEPRESSION (TD) 27W (TWENTYSEVEN), LOCATED APPROXIMATELY 
240 NM SOUTHEAST OF HAGATNA, GUAM, HAS TRACKED SOUTHWARD AT 10 KNOTS
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
DEPICTS AN EXPOSED, DEFINED LOW-LEVEL CIRCULATION CENTER (LLCC) WITH 
PERSISTENT DEEP CONVECTION OVER THE WESTERN SEMI-CIRCLE. THE INITIAL 
INTENSITY IS ASSESSED AT 30 KNOTS BASED ON DVORAK INTENSITY 
ESTIMATES OF T2.0 (30 KNOTS) FROM KNES AND PGTW, CONSISTENT WITH A 
RECENT ASCAT IMAGE SHOWING 25 TO 30 KNOT WINDS OVER THE SOUTHWEST 
QUADRANT. UPPER-LEVEL ANALYSIS INDICATES A MARGINAL ENVIRONMENT WITH 
MODERATE TO STRONG (25 TO 35 KNOTS) EASTERLY VERTICAL WIND SHEAR 
(VWS). TD 27W IS TRACKING ERRATICALLY WITHIN A COMPETING STEERING 
ENVIRONMENT.
3. FORECAST REASONING.
   A. NO CHANGE IN THE FORECAST PHILOSOPHY SINCE THE PREVIOUS 
PROGNOSTIC REASONING MESSAGE, HOWEVER, THE DEGRADING ENVIRONMENTAL 
CONDITIONS AND SOUTHWARD TRACK MAY LEAD TO DISSIPATION OVER THE NEXT 
24 TO 36 HOURS IF THE SYSTEM FAILS TO SURVIVE. 
   B. TD 27W IS POSITIONED WITHIN A COMPETING STEERING ENVIRONMENT 
WITH A LOW-LEVEL (700MB) SUBTROPICAL RIDGE (STR) TO THE NORTH AND 
NORTHEAST, AND A NEAR-EQUATORIAL RIDGE (NER) TO THE WEST AND 
SOUTHWEST. A RECENT GUAM UPPER-AIR SOUNDING SUPPORTS THE PRESENCE OF 
THE NER POSITIONED WEST OF GUAM WITH NORTH-NORTHWESTERLY WINDS AT 
850-700MB, WHICH WILL PRODUCE A SOUTHWARD TO SOUTHWESTWARD TRACK 
THROUGH TAU 12. HOWEVER, THIS SOUNDING SHOWS INCREASING EASTERLY 
FLOW ABOVE 700MB, WHICH SUGGESTS A WEAKENING NER AND BUILDING STR AS 
FORECAST BY THE MODELS. PERSISTENT VWS WILL LIMIT INTENSIFICATION 
THROUGH TAU 24 TO 36. AFTER TAU 36, ENVIRONMENTAL CONDITIONS ARE 
FORECAST TO IMPROVE LEADING TO A PERIOD OF SLOW INTENSIFICATION / 
CONSOLIDATION. DYNAMIC AIDS ARE IN FAIR AGREEMENT AFTER TAU 36 WITH 
SOLUTIONS ACCELERATING TD 27W WEST-NORTHWESTWARD TO NORTHWESTWARD AS 
THE STR ASSUMES STEERING CONTROL.     
   C. IN THE EXTENDED PERIOD, TD 27W IS FORECAST TO RE-CURVE 
POLEWARD TOWARD A WEAKNESS IN THE STR. IMPROVED POLEWARD VENTILATION 
WILL ALLOW TD 27W TO INTENSIFY TO A PEAK INTENSITY OF 65 KNOTS BY 
TAU 120. OVERALL, THERE IS LOW CONFIDENCE IN THE JTWC FORECAST DUE 
TO UNCERTAINTY IN THE TRACK IN THE EARLY PORTION OF THE FORECAST. 
AFTER TAU 120, STRONG ZONAL WESTERLIES ARE FORECAST TO PERSIST OVER 
JAPAN MAKING LANDFALL OVER MAINLAND JAPAN EXTREMELY UNLIKELY.//
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