WDPN32 PGTW 271500
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL DEPRESSION 11W WARNING NR 09//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL DEPRESSION (TD) 11W (ELEVEN), LOCATED APPROXIMATELY
335 NM WEST-SOUTHWEST OF ANDERSEN AFB, GUAM, HAS TRACKED WEST-
NORTHWESTWARD AT 13 KNOTS OVER THE PAST SIX HOURS. ANIMATED INFRARED 
(IR) SATELLITE IMAGERY AND A 271153Z AMSU MICROWAVE IMAGE SHOW AN 
UNORGANIZED LOW LEVEL CIRCULATION CENTER (LLCC) WITH A LARGE BAND OF 
DEEP CONVECTION DISPLACED TO THE NORTHWEST. THE INITIAL POSITION WAS 
BASED ON THE IR IMAGERY WITH LOW CONFIDENCE. THE INITIAL INTENSITY 
WAS BASED ON DVORAK ESTIMATES FROM PGTW, KNES, AND RJTD RANGING FROM 
25 TO 30 KNOTS. UPPER LEVEL ANALYSIS INDICATES TD 11W IS LOCATED 
BENEATH THE SOUTHERN EXTENT OF A RIDGE AXIS IN AN AREA OF WEAK 
DIVERGENCE ALOFT AND MODERATE 20 TO 25 KNOTS OF VERTICAL WIND SHEAR 
(VWS). 
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY.
   B. TD 11W IS CURRENTLY TRACKING ALONG THE WESTERN PERIPHERY OF A 
LOW- TO MID-LEVEL STEERING RIDGE AND THE SYSTEM IS EXPECTED TO 
CONTINUE TRACKING GENERALLY NORTHWESTWARD OVER THE NEXT 24 TO 36 
HOURS. A STRONG SUBTROPICAL RIDGE (STR) TO THE NORTH SHOULD THEN 
BEGIN TO WEAKEN DUE TO A DIGGING MID-LATITUDE TROUGH AND ALLOW TD 
11W TO TURN POLEWARD. TD 11W IS FORECAST TO GRADUALLY INTENSIFY AS 
IT TRACKS UNDER A MORE FAVORABLE UPPER LEVEL ENVIRONMENT AND THEN 
INTENSIFY AT A FASTER RATE WHEN POLEWARD OUTFLOW IMPROVES INTO THE 
DIGGING UPPER LEVEL TROUGH. THE NUMERICAL MODEL GUIDANCE IS IN POOR 
AGREEMENT WITH THE TIMING OF THE TURN NORTHWARD, SO THERE IS SOME 
UNCERTAINTY IN THE FORECAST TRACK.
   C. AROUND TAU 72, TD 11W IS EXPECTED TO TURN NORTHEASTWARD UNDER 
THE STEERING INFLUENCE OF THE WEAKENING STR. IN THE EXTENDED TAUS 
BEGINNING AFTER TAU 96, THE SYSTEM SHOULD TURN NORTHWARD TO 
NORTHWESTWARD AS THE STR RE-BUILDS. BOTH NOGAPS AND GFS ARE NOW 
SHOWING THE TURN NORTHWESTWARD.//
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