JTWC Forecast: Cat4 Luzon
Posted by JAC on 10/16/2009, 7:43 am













REMARKS:
160900Z POSITION NEAR 14.1N 135.5E.
TYPHOON (TY) 22W (LUPIT), LOCATED APPROXIMATELY 290 NM NORTH-
NORTHWEST OF YAP, HAS TRACKED WEST-NORTHWEST AT 15 KNOTS OVER THE
PAST SIX HOURS. ANIMATED MULTISPECTRAL IMAGERY SHOWS A TIGHTLY
WRAPPED SYSTEM WITH A BANDING EYE AND ANIMATED WATER VAPOR IMAGERY
ILLUSTRATES EXCELLENT POLEWARD OUTFLOW INTO THE MID-LATITUDE
WESTERLIES AS THE SYSTEM IS TRACKING SOUTH OF THE VERY NARROW (ONLY
ABOUT FIVE DEGREES, NORTH TO SOUTH) SUBTROPICAL RIDGE. THE CURRENT
INTENSITY IS AN AVERAGE OF DVORAK ESTIMATES FROM PGTW (T4.5), KNES
(T4.0) AND RJTD (T3.5). THE CURRENT POSITION IS BASED ON THE PGTW
POSITION FIX AND IS SUPPORTED BY THE 160444Z AMSRE MICROWAVE IMAGE
WHICH CAPTURES THE WRAPPING CONVECTION AND DEPICTS A MICROWAVE EYE.
TY LUPIT IS STILL EXPECTED TO SLOW IN FORWARD TRACK SPEED IN THE
NEXT DAY OR TWO AS THE APPROACHING MID-LATITUDE TROUGH WEAKENS THE
STEERING INFLUENCE. THOUGH THE NUMERICAL MODELS STILL DIFFER ON THE
DEGREE TO WHICH THE TROUGH WILL AFFECT THE SPEED AND POLEWARD TURN
OF LUPIT, THEY HAVE COME INTO VERY GOOD AGREEMENT ON AN EXTENDED
TRACK TOWARDS NORTHERN LUZON. MAXIMUM SIGNIFICANT WAVE HEIGHT AT
160600Z IS 17 FEET. NEXT WARNINGS AT 161500Z, 162100Z, 170300Z AND
170900Z.//
NNNN


1. FOR METEOROLOGISTS.
2. 12 HOUR SUMMARY AND ANALYSIS.
   A. TROPICAL STORM (TS) 22W (TWENTYTWO) IS LOCATED APPROXIMATELY
275 NM WEST-SOUTHWEST OF GUAM AND HAS TRACKED WESTWARD ALONG THE
SOUTHERN PERIPHERY OF THE SUBTROPICAL RIDGE AT 17 KNOTS OVER THE
PAST SIX HOURS. ANIMATED INFRARED IMAGERY SHOWS MULTIPLE BANDS
OF DEEP CONVECTION STARTING TO WRAP INTO THE LOW LEVEL CIRCULATION
CENTER. ANIMATED WATER VAPOR IMAGERY ALSO DEPICTS VERY GOOD POLEWARD
OUTFLOW INTO A TROPICAL UPPER TROPOSPHERIC TROUGH (TUTT) CELL LOCATED
TO THE NORTHEAST OF THE SYSTEM. AS SUCH, THE SYSTEM HAS STEADILY
INTENSIFIED OVER THE LAST 12 HOURS AND IS NOW AT 45 KNOTS. THE
CURRENT INTENSITY IS BASED ON DVORAK ESTIMATES FROM PGTW AND
KNES (T3.0) AS WELL AS A 150800Z SATCON ESTIMATE WHICH INCLUDED AN
AUTOMATED DVORAK VALUE OF T3.1. DUE TO DEEP, CENTRAL CONVECTION, THE
CURRENT POSITION IS PLACED WITH RELATIVELY LOW CONFIDENCE WEST OF THE
PGTW POSITION FIX, EAST OF THE RJTD POSITION FIX, AND SUPPORTED BY
THE 150956Z SSMIS MICROWAVE IMAGE (WHICH ALSO REVEALS THE CONVECTIVE
ORGANIZATION AND DEVELOPED LOW LEVEL SIGNATURE).  
3. FORECAST REASONING.
   A. THE FORECAST REASONING HAS NOT CHANGED SINCE THE PREVIOUS
PROGNOSTIC REASONING BULLETIN.
   B. TS 22W IS EXPECTED TO TRACK GENERALLY WEST-NORTHWESTWARD ALONG
THE SUBTROPICAL STEERING RIDGE OVER THE NEXT TWO DAYS. BY TAU 36, THE
SYSTEM IS EXPECTED TO SLOW IN FORWARD TRACK SPEED AND TAKE A MORE
POLEWARD TRACK AS A MID-LATITUDE TROUGH TEMPORARILY WEAKENS THE
SUBTROPICAL STEERING RIDGE. WHILE TRACKING WESTWARD, TS 22W WILL
REMAIN IN A FAVORABLE ENVIRONMENT CHARACTERIZED BY MINIMAL VERTICAL
WIND SHEAR, GOOD POLEWARD OUTFLOW INTO THE TUTT AND EXCELLENT OCEAN
HEAT CONTENT VALUES IN EXCESS OF 100 J/KG/CM^2.
   C. BY TAU 72, TS 22W SHOULD RESUME ITS WESTWARD TRACK UNDER THE
INFLUENCE OF A REBUILT SUBTROPICAL RIDGE. AS TS 22W MAKES ITS WAY
THROUGH THE PHILIPPINE SEA, THE SYSTEM SHOULD CONTINUE TO STEADILY
INTENSIFY AS THE ENVIRONMENT IS FORECAST TO REMAIN FAVORABLE. THE
NUMERICAL MODEL AIDS ARE IN VERY GOOD AGREEMENT WITH A JOG TO THE
NORTHWEST DUE TO THE MID-LATITUDE TROUGH AS WELL AS A RETURN TO A
MORE WESTWARD TRACK IN THE EXTENDED TAUS. HOWEVER, THE AIDS DO VARY
ON THE TIMING OF INTERACTION AND THE DEGREE TO WHICH THE TROUGH WILL
AFFECT THE TRACK OF 22W. THE NOGAPS MODEL, FOR EXAMPLE, DEPICTS A
DEEPER TROUGH THAT WILL ENABLE THE SYSTEM TO GAIN MORE LATITUDE
BEFORE TURNING WESTWARD WHILE THE UKMO MODEL INDICATES A SHALLOW
TROUGH AND TRACK ON THE SOUTHERN EDGE OF THE AIDS ENVELOPE. THIS
FORECAST LEANS TOWARD THE JTWC CONSENSUS AND ECMWF SOLUTIONS WHICH
CALL FOR THE TROUGH TO WEAKEN THE STEERING INFLUENCE OF THE SUB-
TROPICAL RIDGE (BUT NOT DIG TO THE EXTENT OF THE NOGAPS MODELS AND
THEREFORE DO NOT PULL THE SYSTEM AS FAR NORTH) AND SLOW THE SYSTEM'S
TRACK SPEED BETWEEN TAUS 36 AND 72.//
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22W - Philippines could get hammered again - JAC, 10/15/2009, 7:21 am
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