WDPN31 PGTW 240300
MSGID/GENADMIN/NAVMARFCSTCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 14W (NANMADOL) WARNING 
NR 06//
RMKS/
1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 14W (NANMADOL), LOCATED APPROXIMATELY 600 
NM SOUTH OF KADENA AB, OKINAWA, HAS TRACKED NORTHWARD AT 03 KNOTS 
OVER THE PAST SIX HOURS. ANIMATED MULTISPECTRAL SATELLITE IMAGERY 
INDICATES THAT CONVECTION IS STEADILY DEEPENING AND CONSOLIDATING 
AROUND THE LOW LEVEL CIRCULATION CENTER (LLCC). DESPITE THE 
AVAILABILITY OF VISUAL IMAGERY, POSITION CONFIDENCE IS LOWER THAN 
NORMAL DUE TO A DISPARITY BETWEEN MICROWAVE AND SATELLITE IMAGERY. A 
RECENT AMSUB TEMPERATURE SCAN ALSO SHOWS INTENSIFICATION OF THE MID-
LEVEL WARM ANOMALY OVER THE LLCC. TS 14W EXISTS WITHIN A VIGOROUS 
MONSOON TROUGH, WHICH EXTENDS OVER THE PHILIPPINE SEA AND ONWARDS TO 
THE NORTHERN MARIANAS. THE 231200Z PGTW UPPER LEVEL STREAMLINE 
ANALYSIS REVEALS AN UPPER LEVEL ANTICYCLONE CENTERED NEAR 17N 128E, 
PLACING TS NANMADOL UNDER A REGION OF HIGHLY DIFFLUENT FLOW AND LOW 
VERTICAL WIND SHEAR. WATER VAPOR ANIMATION SHOWS IMPROVING OUTFLOW, 
ESPECIALLY OVER THE WESTERN SEMICIRCLE. A WEAK POLAR OUTFLOW CHANNEL 
INTO A STATIONARY TUTT CELL TO THE EAST OF THE RYUKYUS PERSISTS, 
ALTHOUGH THE CHANNEL HAS NARROWED SIGNIFICANTLY IN THE LAST 24 
HOURS. THE CURRENT INTENSITY ASSESSMENT IS BASED ON THE OBSERVED 
INTENSIFICATION FACTORED WITH DVORAK ESTIMATES OF 45 KNOTS FROM 
RJTD, PGTW AND RJTD. TS 14W CONTINUES A SLOW POLEWARD DRIFT IN A 
VERY WEAK STEERING ENVIRONMENT. THE PREVAILING SYNOPTIC PATTERN OVER 
THE WESTERN PACIFIC IS THE EARLY STAGE OF A MONSOON GYRE. TYPICAL OF 
A MONSOON GYRE ARE MULTIPLE VORTICES WITHIN THE BROAD CIRCULATION, 
AND THERE ARE CURRENTLY TWO VORTICES TO THE EAST AND NORTHEAST OF TS 
14W. THE PRIMARY CIRCULATION OF INTEREST IS THE SUBJECT OF A 
TROPICAL CYCLONE FORMATION ALERT WEST-NORTHWEST OF GUAM. THERE IS 
CURRENTLY 900 NM OF SEPARATION BETWEEN THE TWO SYSTEMS AND THEY ARE 
NOT INFLUENCING EACH OTHER YET, HOWEVER THE TWO SYSTEMS ARE CLOSING 
ON EACH OTHER AT APPROXIMATELY 05 KNOTS. THE TRADITIONAL SEPARATION 
AT WHICH TWO DEVELOPED CYCLONES BEGIN TO INTERACT IS APPROXIMATELY 
700 NM. 
3. FORECAST REASONING
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY. 
   B. TS 14W WILL CONTINUE ALONG AN ERRATIC BUT ROUGHLY NORTHWARD 
DRIFT THROUGH TAU 48, AS THE GYRE PATTERN WILL SUSTAIN THE WEAK 
STEERING ENVIRONMENT. A SUBSIDENT ENVIRONMENT NORTH OF THE SYSTEM 
WILL MAKE FOR SLOWER THAN NORMAL INTENSIFICATION, BUT TS 14W WILL 
REACH TYPHOON STRENGTH NEAR TAU 24. ONE EFFECT OF THE INHERENT 
COMPLEXITY OF MONSOON GYRES IS THAT MODEL GUIDANCE HAS BEEN IN NOT 
ONLY IN POOR AGREEMENT, BUT INCONSISTENT FROM RUN TO RUN. THE ECMWF 
MODEL HAS BEEN GENERATING THE MOST CONSISTENT SCENARIO SINCE THE 
FORMATIVE STAGES, AND ITS SOLUTION IS KEEPING WITH TRACKS TYPICAL 
IN A MONSOON GYRE SCENARIO. AFTER TAU 48, TS 14W WILL BEND TO THE 
NORTHEAST AND BEGIN A PHASE OF DIRECT CYCLONE INTERACTION (DCI) WITH 
THE SYSTEM THAT IS NOW WEST-NORTHWEST OF GUAM. AS THIS OCCURS, THE 
INTENSITY OF THE SYSTEM WILL PLATEAU. 
   C. THERE EXISTS SUBSTANTIAL UNCERTAINTY IN THE EXTENDED RANGES 
DUE TO THE WIDE RANGE OF POSSIBLE EFFECTS ASSOCIATED WITH THE DCI. 
TS 14W IS EXPECTED TO CONTINUE A CYCLONIC ROTATION AROUND ITS 
COUNTERPART SYSTEM, AND THERE IS A SIGNIFICANT POSSIBILITY OF 
FUJIWARA INTERACTION BETWEEN THE TWO SYSTEMS. AT THIS POINT IT IS 
UNCLEAR AS TO WHICH OF THE TWO SYSTEMS, IF EITHER, WILL BECOME 
DOMINANT, THUS THE INTENSITY FORECAST REMAINS FLAT IN THE EXTENDED 
OUTLOOK.//
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