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Tropical Depression FOUR


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TROPICAL DEPRESSION FOUR DISCUSSION NUMBER   1
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL042013
500 AM EDT WED JUL 24 2013
 
GEOSTATIONARY SATELLITE IMAGES SHOW THAT THE DEEP CONVECTION
ASSOCIATED WITH THE LOW PRESSURE SYSTEM OVER THE EASTERN ATLANTIC
HAS INCREASED IN COVERAGE AND BECOME MORE CONCENTRATED NEAR THE
CENTER OVERNIGHT AND EARLY THIS MORNING.  EARLIER SCATTEROMETER
DATA INDICATED THAT THE SYSTEM HAD A WELL-DEFINED CENTER AND
MAXIMUM WINDS OF AROUND 30 KT. BASED ON THESE DATA...THE SYSTEM IS
NOW BEING CLASSIFIED AS A TROPICAL DEPRESSION.  

THE DEPRESSION IS MOVING WEST-NORTHWESTWARD OR 285 DEGREES AT 
17 KT. THE CYCLONE IS EXPECTED TO BE STEERED WESTWARD OR WEST-
NORTHWESTWARD TO THE SOUTH OF A LARGE DEEP-LAYER RIDGE OVER 
THE CENTRAL AND EASTERN ATLANTIC.  THE DYNAMICAL MODEL GUIDANCE
IS IN VERY GOOD AGREEMENT ON THIS SCENARIO...ALTHOUGH THERE ARE 
SOME DIFFERENCES IN HOW FAST THE CYCLONE MOVES WESTWARD.  THE GFS
AND ECMWF SHOW A FASTER FORWARD MOTION THAN MOST OF THE OTHER 
TRACK MODELS.  AS A RESULT...THE NHC FORECAST LEANS TOWARD THESE
TYPICALLY RELIABLE MODELS AND SHOWS A FASTER WESTWARD MOTION THAN
THE MULTI-MODEL CONSENSUS.

THE INTENSITY FORECAST IS OF LOWER CONFIDENCE THAN THE TRACK
FORECAST.  ALTHOUGH THE SHEAR IS EXPECTED TO REMAIN LOW DURING THE
NEXT FEW DAYS...THE CYCLONE WILL BE MOVING OVER SLIGHTLY COOLER
WATERS AND INTO A LITTLE DRIER ENVIRONMENT OVER THE NEXT
DAY OR TWO.  THEREFORE...ONLY SLIGHT STRENGTHENING IS INDICATED
IN THE NHC FORECAST.  LATER IN THE FORECAST PERIOD...THE CYCLONE
IS EXPECTED TO APPROACH AN UPPER-LEVEL TROUGH OVER THE WEST-CENTRAL
ATLANTIC WHICH COULD CAUSE AN INCREASE IN SOUTHWESTERLY SHEAR. 
BECAUSE OF THIS...THE NHC FORECAST SHOWS LITTLE CHANGE IN STRENGTH
DURING THE 3 TO 5 DAY TIME PERIOD.

FORECAST POSITIONS AND MAX WINDS
 
INIT  24/0900Z 13.9N  28.1W   30 KT  35 MPH
 12H  24/1800Z 14.6N  30.8W   35 KT  40 MPH
 24H  25/0600Z 15.5N  34.4W   40 KT  45 MPH
 36H  25/1800Z 16.2N  37.8W   40 KT  45 MPH
 48H  26/0600Z 16.8N  41.2W   40 KT  45 MPH
 72H  27/0600Z 18.2N  49.0W   40 KT  45 MPH
 96H  28/0600Z 19.3N  56.5W   40 KT  45 MPH
120H  29/0600Z 20.0N  62.0W   40 KT  45 MPH
 
$$
FORECASTER BROWN
 
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