WDPN31 PGTW 280300
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 25W (JEBI) WARNING NR 
04//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TROPICAL STORM (TS) 25W (JEBI), LOCATED APPROXIMATELY 648 NM EAST
OF SAIPAN, CNMI, HAS TRACKED NORTHWESTWARD AT 14 KNOTS OVER THE PAST
SIX HOURS. ANIMATED MSI SHOWS THE SYSTEM HAS CONSOLIDATED AS
CONVECTIVE BANDS, ESPECIALLY FROM THE SOUTHERN PERIPHERY, HAVE BECOME
MORE SOLID AND WRAPPED TIGHTER INTO AN OBSCURED LLC. THE INITIAL
POSITION IS EXTRAPOLATED FROM THE MSI LOOP AND LINED UP WITH A
DEFINED LLC FEATURE IN THE 272137Z AMSU MICROWAVE PASS. THE INITIAL
INTENSITY OF 35 KNOTS IS BASED ON CONGRUENT DVORAK ESTIMATES OF
T2.5/35 KNOTS FROM PGTW AND KNES AND REFLECTS THE IMPROVED STATUS OF
THE SYSTEM. UPPER LEVEL ANALYSIS INDICATES THE SYSTEM IS JUST SOUTH
OF THE STR AXIS IN AN AREA OF LOW VWS AND GOOD RADIAL DIFFLUENCE WITH
A RECENT SURGE IN THE POLEWARD OUTFLOW. THE CYCLONE IS TRACKING ALONG
THE SOUTHWEST PERIPHERY OF A DEEP-LAYERED STR TO THE NORTHEAST. 
3. FORECAST REASONING.
   A. THERE IS NO CHANGE TO THE FORECAST PHILOSOPHY FROM THE PREVIOUS
WARNING.  
   B. TS 25W WILL GRADUALLY TURN TO A WEST-NORTHWEST TRAJECTORY AFTER
TAU 12 AS THE STR BUILDS. THE FAVORABLE ENVIRONMENTAL CONDITIONS
DESCRIBED ABOVE WILL PREVAIL, TEMPERED ONLY BY THE SUBSIDING EFFECT
OF A TUTT CELL TO THE NORTHWEST, AND PROMOTE STEADY INTENSIFICATION
UP TO 100 KNOTS BY TAU 72. THE AVAILABLE NUMERICAL MODEL FORECAST
MEMBERS ARE IN TIGHT AGREEMENT, LENDING HIGH CONFIDENCE IN THIS
PORTION OF THE JTWC TRACK FORECAST.
   C. BEYOND TAU 72, TS JEBI IS EXPECTED TO TRACK ON A MORE POLEWARD
TRAJECTORY TOWARD A BREAK IN THE STR, INDUCED BY A DEVELOPING
MID-LATITUDE TROUGH. THE MORE POLEWARD TRACK WILL EXPOSE THE SYSTEM
TO INCREASING VWS; HOWEVER, A SUSTAINED ROBUST POLEWARD OUTFLOW WILL
PARTLY OFFSET THE VWS AND PROMOTE A SLOWER INTENSIFICATION RATE TO
120 KNOTS BY TAU 120.  MODEL TRACK FORECASTS ARE IN OVERALL GOOD
AGREEMENT BUT ARE STILL SPREAD BY OVER 260 NM IN THE EXTENDED TAUS.
ALSO, THE ECMWF SUITE (ECM2 AND EMX2) CONTINUE TO BE THE LEFT
OUTLIERS, DEPICTING A WIDER TURN TO THE WEST. GIVEN THE MODEL SPREAD,
THERE IS LOW CONFIDENCE IN THE EXTENDED RANGE JTWC TRACK FORECAST.//
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