Tropical Depression ELEVEN

ZCZC MIATCDAT1 ALL
TTAA00 KNHC DDHHMM
 
TROPICAL DEPRESSION ELEVEN DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL112013
500 AM AST SUN SEP 29 2013
 
NIGHTTIME VISIBLE IMAGERY INDICATES THE DEPRESSION HAS A ROBUST
LOW-LEVEL CIRCULATION...BUT THE ASSOCIATED DEEP CONVECTION IS
SHEARED WELL TO THE NORTH AND NORTHEAST OF THE CENTER. SOME WEAK
CURVED BAND FEATURES HAVE DEVELOPED RECENTLY IN THE EASTERN
SEMICIRCLE...SUGGESTING THAT THE SYSTEM IS TRYING TO GET BETTER
ORGANIZED. FOR NOW...HOWEVER...AN INTENSITY OF 30 KT IS BEING
MAINTAINED BASED ON A SATELLITE INTENSITY ESTIMATE OF 30 KT FROM
TAFB AND UW-CIMSS ADT.
 
THE INITIAL MOTION ESTIMATE IS 040/08 KT. THERE IS NO SIGNIFICANT
CHANGE TO THE PREVIOUS FORECAST TRACK OR REASONING. THE SMALL
DEPRESSION IS EXPECTED TO MOVE NORTHEASTWARD AND SLOW DOWN AS IT
MOVES AROUND THE NORTH SIDE OF A WEAKENING MID-LEVEL RIDGE WHILE A
SHORTWAVE TROUGH TO THE NORTH GRADUALLY LIFTS OUT. THIS SHOULD
RESULT IN VERY WEAK STEERING FLOW FOR THE NEXT COUPLE OF DAYS. A
NEW RIDGE IS THEN FORECAST BY THE MODELS TO BUILD IN AND BECOME
HIGHLY AMPLIFIED TO THE WEST AND NORTH OF THE CYCLONE BY 48
HOURS...WHICH SHOULD ACT TO TURN THE CYCLONE WESTWARD THROUGH 72
HOURS...COMPLETING A SMALL CLOCKWISE LOOP IN THE PROCESS. AFTER
THAT...A SECOND AND STRONGER MID-/UPPER-LEVEL TROUGH WILL MOVE
EASTWARD FROM THE UNITED STATES...AND ACT TO LIFT OUT THE CYCLONE
AND ACCELERATE IT TO THE NORTHEAST ON DAYS 4 AND 5. THE NEW NHC
FORECAST TRACK IS ALMOST IDENTICAL TO THE PREVIOUS TRACK...AND LIES
CLOSE TO A BLEND OF THE GFS AND ECMWF MODELS.
 
ALTHOUGH THE GFS-BASED SHIPS INTENSITY MODEL IS ONLY INDICATING 9 KT
OF SOUTH-SOUTHWESTERLY VERTICAL SHEAR ACROSS THE DEPRESSION...WHICH
IS SIGNIFICANTLY LOWER THAN IT WAS ON THE PREVIOUS ADVISORY...
SATELLITE IMAGERY AND THE ASSOCIATED CONVECTIVE CLOUD PATTERN OF
THE DEPRESSION SUGGESTS THAT THE SHEAR IS CONSIDERABLY STRONGER...
LIKELY DUE TO THE PRESENCE OF A MID-/UPPER-LEVEL LOW LOCATED ONLY
ABOUT 300 NMI TO THE NORTHWEST OF THE CYCLONE. THAT LOW IS FORECAST
BY MOST OF THE MODELS...ESPECIALLY THE GFS AND ECMWF...TO MOVE IN
TANDEM WITH THE CYCLONE OVER THE NEXT 72 HOURS OR SO AS IT MAKES A
CLOCKWISE LOOP. AS A RESULT...THIS SYSTEM WILL LIKELY BE PLAGUED BY
AT LEAST MODERATE SHEAR FOR THE NEXT 2 TO 3 DAYS...WHICH SHOULD
PREVENT ANY SIGNIFICANT STRENGTHENING FROM OCCURRING. THE NHC
INTENSITY FORECAST IS IDENTICAL TO THE PREVIOUS PACKAGE AND REMAINS
CLOSE TO THE INTENSITY CONSENSUS MODEL...ICON. HOWEVER...IF THE
AFOREMENTIONED UPPER-LEVEL SHOULD DISSIPATE OR MOVE AWAY FROM THE
CYCLONE SOONER THAN CURRENTLY EXPECTED...THEN THE SYSTEM COULD BE
SOMEWHAT STRONGER THAN CURRENTLY FORECAST ON DAYS 4 AND 5.  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/0900Z 25.6N  49.7W   30 KT  35 MPH
 12H  29/1800Z 26.4N  48.8W   35 KT  40 MPH
 24H  30/0600Z 27.0N  47.6W   40 KT  45 MPH
 36H  30/1800Z 26.8N  46.8W   40 KT  45 MPH
 48H  01/0600Z 26.4N  46.6W   40 KT  45 MPH
 72H  02/0600Z 26.3N  47.8W   35 KT  40 MPH
 96H  03/0600Z 27.7N  48.6W   35 KT  40 MPH
120H  04/0600Z 30.0N  47.0W   30 KT  35 MPH
 
$$
FORECASTER STEWART
 
NNNN