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TROPICAL DEPRESSION EIGHT DISCUSSION NUMBER   2
NATIONAL WEATHER SERVICE MIAMI FL
11 PM EDT THU SEP 17 1998
 
CENTER FIXES FROM THE HURRICANE HUNTERS SHOWED A SOUTHWEST MOVEMENT
OF ABOUT 5 KT THIS EVENING.  THIS MOTION AND THE TRACK OVER THE PAST
24-36 HOURS SUGGEST THAT THE TD IS SLOWLY ORBITING AROUND THE
BROADER CYCLONIC CIRCULATION THAT IS CENTERED TO THE SOUTHEAST AND
WHICH COVERS MUCH OF THE GULF OF MEXICO.  WATER VAPOR IMAGERY
CLEARLY DEPICTS THE MID TO UPPER-LEVEL PART OF THAT CIRCULATION
CENTERED NEAR 24N90W.
 
THE PRIMARY QUESTION FOR THE TRACK FORECAST IS...AT WHAT POINT AND
TIME WILL THE TD BE RELEASED FROM THE GRIP OF THE UPPER LOW?  THE
18Z AVN WEAKENS THE UPPER LOW AND MOVES IT TO SE LA BY ABOUT 36
HOURS.  THE 12Z NOGAPS OPENS THE LOW NEAR THE TX/LA COAST IN ABOUT
48 HOURS.  EITHER OF THESE DEVELOPMENTS WOULD IMPLY THAT A NORTHWARD
COMPONENT COULD BE UNDERWAY IN ANOTHER DAY OR SO.  HENCE...ALTHOUGH
THE TRACK OF THE TD COULD FOLLOW A CUSP OR SMALL CYCLONIC LOOP IN
THE INTERIM...THE OFFICIAL FORECAST DOESNT GET SO FANCY.  IT SHOWS
LITTLE MOVEMENT FOR 12 TO 24 HOURS FOLLOWED BY A GENERAL NORTHWARD
OR NORTHEASTWARD HEADING.

CONVECTION HAS INCREASED A LITTLE AND A 37 KT WIND WAS REPORTED AT
1500 FEET FROM THE RECON PLANE.  HENCE...THE SYSTEM IS APPROACHING
TROPICAL STORM STRENGTH AND SOME INTENSIFICATION IS AGAIN FORECAST.
 
RAPPAPORT
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     18/0300Z 26.4N  92.2W    30 KTS
12HR VT     18/1200Z 26.2N  92.3W    35 KTS
24HR VT     19/0000Z 26.6N  92.4W    40 KTS
36HR VT     19/1200Z 27.3N  92.5W    45 KTS
48HR VT     20/0000Z 28.7N  92.3W    50 KTS
72HR VT     21/0000Z 31.5N  90.5W    25 KTS...INLAND
 
 
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