WDPN31 PGTW 110300
MSGID/GENADMIN/NAVPACMETOCCEN PEARL HARBOR HI/JTWC//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL STORM 31W
/WARNING NR 05//
RMKS/
1. FOR METEOROLOGISTS.
2. PROGNOSTIC REASONING FOR 110000Z2 TO 160000Z7 DEC 2004.
   A. TROPICAL STORM (TS) 31W, LOCATED APPROXIMATELY 375 NM EAST-
NORTHEAST OF POHNPEI, HAS TRACKED WESTWARD AT 17 KNOTS OVER THE PAST
06 HOURS. THE WARNING POSITION IS BASED ON 102330Z9 MULTISPECTRAL
SATELLITE IMAGERY. THE WARNING INTENSITY IS BASED ON SATELLITE
CURRENT INTENSITY ESTIMATES OF 35 AND 45 KNOTS. RECENT ANIMATED
ENHANCED INFRARED AND MICROWAVE IMAGERY REVEALS AN INCREASE IN DEEP
CONVECTION, HOWEVER RADIAL OUTFLOW REMAINS SOMEWHAT DISORGANIZED ON
THE NORTHERN PERIPHERY.
   B. DURING THE NEXT 36 TO 48 HOURS, TS 31W IS FORECAST TO RAPIDLY
TRACK WEST-NORTHWEST AROUND THE SOUTHERN PERIPHERY OF THE SUBTROPICAL
RIDGE ANCHORED TO THE NORTH. THE SYSTEM IS EXPECTED TO MAINTAIN THIS
SPEED AS THE STEERING FLOW FROM THE RIDGE IS ENHANCED BY A TRANSIENT
MAJOR SHORTWAVE TROUGH (MSWT) IN THE MIDLATITUDES. AFTER TAU 48, TS
31W SHOULD BEGIN TO TRACK MORE NORTHWESTWARD, AND IT IS EXPECTED TO RE-
MAIN SOUTH OF THE MARIANAS ISLANDS. THE AVAILABLE DYNAMIC AIDS
CONSISTING OF GFDN, NOGAPS, AVN, WBAR, AND UKMO ARE IN GOOD AGREEMENT.
UKMO DEPICTS A SLIGHTLY MORE POLEWARD SOLUTION WHILE GFDN DEPICTS A
SLIGHTLY MORE EQUATORWARD SOLUTION. THIS FORECAST IS BASED ON A
CONSENSUS OF ALL AVAILABLE DYNAMIC AIDS WITH LESS EMPHASIS ON UKMO
AND GFDN.
   C. THE INTENSITY OF TS 31W IS EXPECTED TO INCREASE AT LESS THAN
A CLIMATOLOGICAL RATE DUE TO A SURPRESSED OUTFLOW AND RAPID SPEED OF
ADVANCE. THE SYSTEM IS FORECAST TO TRACK POLEWARD OF A REGION OF
ENHANCED VERTICAL WIND SHEAR WHICH MAY HAVE AN IMPACT ON THE EQUATOR-
WARD OUTFLOW.
   D. CURRENT WIND RADII ARE BASED ON A 102158Z7 SSMI MICROWAVE AND
101905Z6 QUIKSCAT PASS. FORECAST WIND RADII ARE BASED ON CLIMATOLOGY
FOR AN AVERAGE SIZED SYSTEM.
   E. AFTER TAU 72, TS 31W SHOULD BEGIN A POLEWARD TURN AROUND THE
WESTERN PERIPHERY OF THE SUBTROPICAL RIDGE. THE SYSTEM SHOULD MOVE INTO
A WEAKER STEERING ENVIRONMENT AS THE RIDGE RESPONDS TO A TRANSIENT
MSWT. ADDITIONALLY, VERTICAL WIND SHEAR IS FORECAST TO DECREASE WHICH
SHOULD ALLOW FOR IMPROVED OUTFLOW.
3.FORECAST TEAM: LEFFLER/RONSSE/LEWIN//