000 WTNT42 KNHC 172042 TCDAT2 TROPICAL DEPRESSION TWO DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022011 500 PM EDT SUN JUL 17 2011 AN AIR FORCE HURRICANE HUNTER PLANE INVESTIGATING THE LOW PRESSURE AREA JUST NORTH OF THE NORTHWEST BAHAMAS FOUND A WELL-DEFINED LOW-LEVEL CENTER OF CIRCULATION...AND THE SYSTEM IS BEING DESIGNATED AS A TROPICAL CYCLONE AT THIS TIME. ALTHOUGH WINDS OF TROPICAL STORM FORCE WERE MEASURED BY THE SFMR INSTRUMENT ON BOARD THE PLANE...THESE OBSERVATIONS WERE FLAGGED AS QUESTIONABLE. PEAK FLIGHT-LEVEL WINDS REPORTED BY THE AIRCRAFT WERE 44 KT WHICH WOULD NORMALLY INDICATE A SYSTEM OF TROPICAL STORM STRENGTH. HOWEVER... THE CONVECTION NEAR THE CENTER IS RELATIVELY WEAK...AND IN THIS CASE THE STRONGEST WINDS ARE LIKELY NOT MIXING DOWN TO THE SURFACE AS MUCH AS TYPICALLY OCCURS. THE CURRENT INTENSITY ESTIMATE IS 30 KT. THE ATMOSPHERIC ENVIRONMENT IS NOT IDEAL FOR STRENGTHENING WITH SOME DRIER AIR JUST TO THE NORTH AND NORTHWEST OF THE CYCLONE. THE OFFICIAL INTENSITY FORECAST CLOSELY FOLLOWS THE LGEM AND INTENSITY CONSENSUS GUIDANCE. NONE OF THE CURRENT MODEL RUNS SHOW THE SYSTEM STRENGTHENING INTO A HURRICANE. INITIAL MOTION IS A SOUTHWARD DRIFT. STEERING CURRENTS ARE LIKELY TO REMAIN QUITE WEAK OVER THE NEXT DAY OR SO...AS THE SYSTEM IS SITUATED IN A WEAKNESS IN THE SUBTROPICAL RIDGE. IN A COUPLE OF DAYS...THE MID-LEVEL RIDGE TO THE SOUTHEAST OF THE TROPICAL CYCLONE IS FORECAST TO STRENGTHEN SLIGHTLY AND THIS...ALONG WITH A WEAK TROUGH PASSING NORTH OF THE CYCLONE...SHOULD INDUCE A GENERAL NORTHEASTWARD MOTION. LATER IN THE FORECAST PERIOD...THE TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON AN EAST-NORTHEASTWARD MOTION AT AN INCREASING FORWARD SPEED. THE OFFICIAL FORECAST IS RATHER CLOSE TO THE MODEL CONSENSUS AND TO THE LATEST ECMWF TRACK. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 27.5N 78.2W 30 KT 35 MPH 12H 18/0600Z 27.4N 78.2W 40 KT 45 MPH 24H 18/1800Z 28.2N 77.8W 45 KT 50 MPH 36H 19/0600Z 29.0N 77.3W 50 KT 60 MPH 48H 19/1800Z 30.4N 76.5W 50 KT 60 MPH 72H 20/1800Z 32.0N 73.5W 50 KT 60 MPH 96H 21/1800Z 34.0N 67.0W 45 KT 50 MPH 120H 22/1800Z 36.0N 60.0W 40 KT 45 MPH $$ FORECASTER PASCH/STEWART 000 WTNT42 KNHC 172042 TCDAT2 TROPICAL DEPRESSION TWO DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL AL022011 500 PM EDT SUN JUL 17 2011 AN AIR FORCE HURRICANE HUNTER PLANE INVESTIGATING THE LOW PRESSURE AREA JUST NORTH OF THE NORTHWEST BAHAMAS FOUND A WELL-DEFINED LOW-LEVEL CENTER OF CIRCULATION...AND THE SYSTEM IS BEING DESIGNATED AS A TROPICAL CYCLONE AT THIS TIME. ALTHOUGH WINDS OF TROPICAL STORM FORCE WERE MEASURED BY THE SFMR INSTRUMENT ON BOARD THE PLANE...THESE OBSERVATIONS WERE FLAGGED AS QUESTIONABLE. PEAK FLIGHT-LEVEL WINDS REPORTED BY THE AIRCRAFT WERE 44 KT WHICH WOULD NORMALLY INDICATE A SYSTEM OF TROPICAL STORM STRENGTH. HOWEVER... THE CONVECTION NEAR THE CENTER IS RELATIVELY WEAK...AND IN THIS CASE THE STRONGEST WINDS ARE LIKELY NOT MIXING DOWN TO THE SURFACE AS MUCH AS TYPICALLY OCCURS. THE CURRENT INTENSITY ESTIMATE IS 30 KT. THE ATMOSPHERIC ENVIRONMENT IS NOT IDEAL FOR STRENGTHENING WITH SOME DRIER AIR JUST TO THE NORTH AND NORTHWEST OF THE CYCLONE. THE OFFICIAL INTENSITY FORECAST CLOSELY FOLLOWS THE LGEM AND INTENSITY CONSENSUS GUIDANCE. NONE OF THE CURRENT MODEL RUNS SHOW THE SYSTEM STRENGTHENING INTO A HURRICANE. INITIAL MOTION IS A SOUTHWARD DRIFT. STEERING CURRENTS ARE LIKELY TO REMAIN QUITE WEAK OVER THE NEXT DAY OR SO...AS THE SYSTEM IS SITUATED IN A WEAKNESS IN THE SUBTROPICAL RIDGE. IN A COUPLE OF DAYS...THE MID-LEVEL RIDGE TO THE SOUTHEAST OF THE TROPICAL CYCLONE IS FORECAST TO STRENGTHEN SLIGHTLY AND THIS...ALONG WITH A WEAK TROUGH PASSING NORTH OF THE CYCLONE...SHOULD INDUCE A GENERAL NORTHEASTWARD MOTION. LATER IN THE FORECAST PERIOD...THE TRACK GUIDANCE IS IN FAIRLY GOOD AGREEMENT ON AN EAST-NORTHEASTWARD MOTION AT AN INCREASING FORWARD SPEED. THE OFFICIAL FORECAST IS RATHER CLOSE TO THE MODEL CONSENSUS AND TO THE LATEST ECMWF TRACK. FORECAST POSITIONS AND MAX WINDS INIT 17/2100Z 27.5N 78.2W 30 KT 35 MPH 12H 18/0600Z 27.4N 78.2W 40 KT 45 MPH 24H 18/1800Z 28.2N 77.8W 45 KT 50 MPH 36H 19/0600Z 29.0N 77.3W 50 KT 60 MPH 48H 19/1800Z 30.4N 76.5W 50 KT 60 MPH 72H 20/1800Z 32.0N 73.5W 50 KT 60 MPH 96H 21/1800Z 34.0N 67.0W 45 KT 50 MPH 120H 22/1800Z 36.0N 60.0W 40 KT 45 MPH $$ FORECASTER PASCH/STEWART