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Tropical Depression BONNIE (Text)

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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
 
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