WTNT44 KNHC 231442                                              2004267 1442
TCDAT4
TROPICAL STORM IVAN DISCUSSION NUMBER  70
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
11 AM EDT THU SEP 23 2004

A BURST OF DEEP CONVECTION FIRED OFF NEAR THE LOW-LEVEL CENTER
EARLIER THIS MORNING AND AIR FORCE RESERVE RECON FOUND 70 KT 1500
FT FLIGHT-LEVEL WINDS...OR EQUAL TO ABOUT 56 KT SURFACE WINDS...
AND A PRESSURE OF 998 MB. HOWEVER...SINCE THEN THE CONVECTION HAS
WEAKENED AND A SUBSEQUENT PASS THROUGH THE CENTER INDICATED A
CENTRAL PRESSURE OF 1000 MB. THE INITIAL INTENSITY OF 50 KT IS A
BLEND OF A 45 KT SURFACE WIND SUPPORTED BY THE 1000 MB PRESSURE...
AND THE 56 KT SURFACE WIND CONVERSION.

THE INITIAL MOTION ESTIMATE IS 310/13. IVAN IS EXPECTED TO MOVE
NORTHWESTWARD TO WEST-NORTHWESTWARD AND BE INLAND WITHIN THE NEXT
12 HOURS OVER SOUTHWESTERN LOUISIANA OR THE UPPER-TEXAS COAST.
AFTERWARDS...RAPID WEAKENING SHOULD ALLOW THE LOW-LEVEL CIRCULATION
TO DECOUPLE FROM THE MID- AND UPPER-LEVEL CIRCULATIONS. THIS WILL
ALLOW THE LOW-LEVEL CIRCULATION TO BE STEERED SLOWLY WEST AND
SOUTHWESTWARD BY A LARGE RIDGE FORECAST TO BUILD EASTWARD OVER THE
CENTRAL AND SOUTHERN PLAINS STATES IN 36-48 HOURS. THIS TRACK
SCENARIO IS CONSISTENT WITH THE SHALLOW BAM MODEL...AND THE MOST OF
THE GLOBAL MODELS.
WHILE IVAN IS NOT EXPECTED TO BE A PROLIFIC WIND PRODUCER...ITS SLOW
FORWARD SPEED FOR THE NEXT SEVERAL DAYS MAY BRING UP LARGE AMOUNTS
OF GULF MOISTURE THAT COULD RESULT IN LOCALLY HEAVY RAINFALL.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      23/1500Z 29.2N  92.7W    50 KT
 12HR VT     24/0000Z 30.0N  94.0W    45 KT...INLAND
 24HR VT     24/1200Z 30.5N  95.3W    30 KT...INLAND
 36HR VT     25/0000Z 30.6N  96.3W    25 KT...INLAND
 48HR VT     25/1200Z 30.4N  97.0W    20 KT...DISSIPATING INLAND
 72HR VT     26/1200Z 29.5N  97.8W    20 KT...REMNANT LOW INLAND
 96HR VT     27/1200Z...DISSIPATED INLAND


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