000 WTNT44 KNHC 240841 TCDAT4 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