000 WTNT43 KNHC 240235 TCDAT3 TROPICAL DEPRESSION BONNIE DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL032010 1100 PM EDT FRI JUL 23 2010 BONNIE IS CURRENTLY COMPRISED OF A CONVECTIONLESS SWIRL OF LOW CLOUDS EMBEDDED IN A LARGER-SCALE LOW-LEVEL TROUGH. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING THE SYSTEM HAS FOUND WINDS NEAR TROPICAL-STORM FORCE NORTH OF THE CENTER...BUT IS HAVING A HARD TIME FINDING WESTERLY WINDS ON THE SOUTH SIDE. THE AIRCRAFT DATA DOES SHOW A CLOSED LOW PRESSURE AREA WITH A CENTRAL PRESSURE OF 1010 MB. BASED ON THIS CONFLICTING INFORMATION... BONNIE REMAINS A 30 KT DEPRESSION AT THIS TIME. THE CYCLONE HAS TURNED A LITTLE TO THE LEFT DURING THE PAST SEVERAL HOURS...WITH THE INITIAL MOTION NOW 295/15. BONNIE REMAINS ON THE SOUTH SIDE OF A DEEP-LAYER RIDGE OVER THE SOUTHEASTERN UNITED STATES AND EAST OF A LARGE MID/UPPER-LEVEL LOW CENTERED OVER THE WEST CENTRAL GULF OF MEXICO. THIS COMBINATION IS FORECAST TO STEER THE STORM TO A LANDFALL ALONG THE NORTHERN GULF COAST. ALL THE TRACK GUIDANCE AGREES WITH THIS SCENARIO...WITH THE MODELS CLUSTERED OVER THE SOUTHEAST LOUISIANA AND SOUTHERN MISSISSIPPI COASTS. AFTER LANDFALL...BONNIE OR ITS REMNANT LOW SHOULD TURN NORTHWARD AT A SLOWER FORWARD SPEED AROUND THE WESTERN END OF THE RIDGE. THE NEW FORECAST TRACK IS SHIFTED TO THE LEFT BASED UPON THE CURRENT POSITION AND MOTION...AND LIES JUST TO THE RIGHT OF THE CENTER OF THE GUIDANCE ENVELOPE. BONNIE REMAINS IN A LESS THAN IDEAL ENVIRONMENT OF STRONG SOUTHEASTERLY VERTICAL WIND SHEAR...CONFLUENT UPPER-LEVEL FLOW... AND UPPER-LEVEL DRY AIR ENCROACHING ON THE CYCLONE. MOST OF THE INTENSITY GUIDANCE RESPONDS TO THIS BY SHOWING WEAKENING OR DISSIPATION BEFORE LANDFALL...WITH ONLY THE SHIPS AND LGEM SHOWING ANY INTENSIFICATION. THE INTENSITY FORECAST IS BASED ON THE PREMISE THAT ENOUGH CONVECTION WILL RE-DEVELOP TO CAUSE SLIGHT STRENGTHENING BEFORE BONNIE REACHES THE NORTHERN GULF COAST. AN INCREASINGLY LIKELY ALTERNATIVE SCENARIO IS THAT THE CYCLONE WILL DECAY TO A REMNANT LOW OR OPEN TROUGH SOMETIME ON SATURDAY DUE TO A LACK OF CONVECTION. FORECAST POSITIONS AND MAX WINDS INITIAL 24/0300Z 26.4N 83.4W 30 KT 12HR VT 24/1200Z 27.7N 85.7W 30 KT 24HR VT 25/0000Z 29.2N 88.5W 35 KT 36HR VT 25/1200Z 30.5N 90.5W 35 KT...INLAND 48HR VT 26/0000Z 31.4N 91.8W 25 KT...INLAND 72HR VT 27/0000Z 34.0N 93.0W 20 KT...POST-TROP/REMNT LOW 96HR VT 28/0000Z...DISSIPATED $$ FORECASTER BEVEN