Tropical Storm AGATHA

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TROPICAL STORM AGATHA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
8 AM PDT SUN MAY 23 2004
 
AGATHA IS BEGINNING TO DECAY.  THE CENTRAL RING OF CONVECTION
PRESENT IN MICROWAVE IMAGERY 12 HOURS AGO HAS BROKEN UP.  
NOTWITHSTANDING THE RECENT FLARE-UP IN THE SOUTHWEST QUADRANT...
INFRARED IMAGERY INDICATES THAT THE AREAL EXTENT OF DEEP CONVECTION
IS DECREASING.  USING AN AVERAGE OF THE T AND CI NUMBERS...WHICH IS
USUALLY A MORE ACCURATE INDICATOR THAN THE CI NUMBER FOR WEAKENING
SYSTEMS...YIELDS AN INTENSITY ESTIMATE OF 40 KT. A QUIKSCAT PASS AT
01Z SUGGESTS THAT THE RADIUS OF 34 KT WINDS IS ALSO DECREASING. 
UNFORTUNATELY THE MOST RECENT PASS MISSED THE CYCLONE.
 
THE INITIAL MOTION ESTIMATE IS 335/5.  MODEL GUIDANCE CONTINUES TO
INDICATE A WEAKENING OF THE STEERING CURRENTS OVER THE NEXT 24-48
HOURS.  THE GFS SHOWS THE UPPER PORTION OF THE SYSTEM CONTINUING
NORTHWARD AHEAD OF THE LARGE-SCALE UPPER TROUGH TO THE WEST OF
AGATHA...WITH THE LOW LEVEL REMNANTS MOVING SLOWLY NORTHWESTWARD.
THE NOGAPS AND THE UKMET MAINTAIN A MORE VERTICALLY COHERENT SYSTEM
ON A TRACK TO THE RIGHT OF THE GFS.  SINCE THE CYCLONE ALREADY
APPEARS TO BE SHEARING OFF A BIT...THE OFFICIAL FORECAST IS
ADJUSTED SLIGHTLY TO THE LEFT OF THE PREVIOUS ADVISORY...IN THE
DIRECTION OF THE GFS AND THE SHALLOW BAM BUT WITH A SLOWER FORWARD
SPEED.
 
AGATHA IS OVER 26C SSTS AND HEADED...ALBEIT SLOWLY...FOR COOLER
WATERS AND A MORE STABLE AIR MASS.  A GRADUAL SPINDOWN IS THEREFORE
EXPECTED.  THE OFFICIAL INTENSITY FORECAST IS ADJUSTED DOWNWARD BUT
IS STILL ABOVE THE SHIPS AND GFDL GUIDANCE.  AGATHA IS EXPECTED TO
DEGENERATE TO A NON-CONVECTIVE REMNANT LOW WITHIN 48-72 HOURS.
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/1500Z 18.1N 110.4W    40 KT
 12HR VT     24/0000Z 18.9N 110.6W    35 KT
 24HR VT     24/1200Z 19.5N 110.8W    30 KT
 36HR VT     25/0000Z 19.8N 110.9W    30 KT
 48HR VT     25/1200Z 20.0N 111.0W    25 KT...DISSIPATING
 72HR VT     26/1200Z 20.0N 111.0W    25 KT...REMNANT LOW
 96HR VT     27/1200Z 20.5N 111.5W    25 KT...REMNANT LOW
120HR VT     28/1200Z 21.0N 112.0W    20 KT...REMNANT LOW
 
 
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