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TROPICAL DEPRESSION SEVEN DISCUSSION NUMBER   6
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT MON SEP 10 2001
 
SATELLITE IMAGERY INDICATES THAT TROPICAL DEPRESSION SEVEN HAS 
RE-DEVELOPED OVER THE CENTRAL TROPICAL ATLANTIC.  DEEP CONVECTION 
HAS PERSISTED NEAR THE LOW-LEVEL CIRCULATION CENTER...WHILE OUTFLOW 
HAS BECOME MORE PRONOUNCED IN ALL QUADRANTS.  THE CURRENT INTENSITY 
OF 30 KT IS BASED ON A DVORAK SATELLITE INTENSITY ESTIMATE OF 
30KT... T2.0...FROM TAFB AND AN EARLIER QUIKSCAT OVERPASS SHOWING 
30 KT NON-CONTAMINATED WINDS ABOUT 100 NM NORTH OF THE CENTER.  
NEARBY BOUYS ALSO HAVE BEEN REPORTING SURFACE PRESSURES DOWN TO AS 
LOW AS 1008 MB.

THE INITIAL MOTION ESTIMATE IS 275/09.  HOWEVER...THE FORECAST TRACK 
AND FUTURE MOTION OF THE DEPRESSION IS RATHER TRICKY DUE TO THE 
UNCERTAINTY IN THE EXACT LOCATION OF THE CENTER RELATIVE TO THE DEEP 
CONVECTION. THE NHC MODEL GUIDANCE IS SPLIT INTO TWO CAMPS...THE 
CLIMATOLOGICAL AND STATISTICAL-DYNAMICAL MODELS TAKE THE DEPRESSION 
WEST OR WEST-NORTHWESTWARD THROUGHOUT THE PERIOD...WHILE THE GLOBAL 
MODELS TAKE THE CYCLONE NORTHWEST AND THEN TURN IT NORTHWARD EAST OF 
50W LONGITUDE. THE LONE EXCEPTION IS THE LBAR MODEL...WHICH IS IN 
BETWEEN AND APPEARS TO BE A NICE COMPROMISE AT THIS TIME.  THE 
GLOBAL MODELS MAY BE RECURVING THE DEPRESSION A LITTLE PREMATURE 
BASED ON THE FACT THAT (1) THEY ALL INITIALIZED THE CIRCULATION 
CENTER TOO FAR NORTH AND (2) THE UPPER-LEVEL TROUGH THAT IS FORECAST 
TO PICK UP THE CYCLONE IS ALREADY LOCATED NORTHEAST OF THE 
DEPRESSION.  THE UPPER-LEVEL TROUGH TO THE NORTH AND NORTHEAST MAY 
WEAKEN THE MID-LEVEL SUBTROPICAL RIDGE AXIS SOMEWHAT...BUT WATER 
VAPOR IMAGERY SUGGESTS THAT THE UPPER-LEVEL MASS OUTFLOW FROM 
HURRICANE ERIN IS BEING TRANSPORTED INTO THE BASE OF THE 
TROUGH...WHICH WOULD ACT TO MAINTAIN THE STRENGTH OF THE LOW-LEVEL 
RIDGE. THAT WOULD TEND TO KEEP THE DEPRESSION MOVING MORE TOWARD THE 
NORTHWEST THAN TO THE NORTH.

GRADUAL STRENGTHENING IS FOREACST BASED ON THE IMPROVING OUTFLOW 
PATTERN AND VERY WARM SSTS...28C PLUS...AHEAD OF THE DEPRESSION. IT 
IS POSSIBLE THAT TROPICAL DEPRESSION SEVEN MAY ALREADY BE A TROPICAL 
STORM. IF NOT...THEN IT SHOULD BECOME ONE LATER TODAY.

FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     10/0900Z 15.3N  44.5W    30 KTS
12HR VT     10/1800Z 15.6N  45.9W    40 KTS
24HR VT     11/0600Z 16.5N  47.6W    45 KTS
36HR VT     11/1800Z 17.5N  49.0W    55 KTS
48HR VT     12/0600Z 18.6N  50.2W    65 KTS
72HR VT     13/0600Z 20.5N  52.0W    75 KTS
 
 
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