Tropical Storm BONNIE

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TROPICAL STORM BONNIE DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032010
500 AM EDT FRI JUL 23 2010
 
THE AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT INVESTIGATING BONNIE
HAS FOUND LITTLE CHANGE IN STRENGTH.  THE AIRCRAFT HAS MEASURED A
PEAK 850 MB FLIGHT-LEVEL WIND OF 42 KT...BELIEVABLE SFMR WINDS OF
34 KT...AND A MINIMUM PRESSURE OF 1008 MB.  THESE DATA SUPPORT
MAINTAINING AN INITIAL INTENSITY OF 35 KT.  THE AIRCRAFT DATA
SUGGEST THAT THE CIRCULATION HAS BECOME LESS DEFINED AS FEW WEST
OR NORTHWEST WINDS WERE FOUND.  IF THIS TREND CONTINUES...IT IS
POSSIBLE FOR BONNIE TO DEGENERATE TO AN OPEN TROUGH.  FOR NOW...THE
OFFICIAL FORECAST ASSUMES THAT BONNIE WILL BE ABLE TO MAINTAIN A
CLOSED CIRCULATION AND REMAIN A TROPICAL CYCLONE.  AS BONNIE PASSED
THROUGH THE CENTRAL BAHAMAS...AN OBSERVING SITE ON STANIEL CAY
REPORTED A SUSTAINED WIND OF 37 KT.  
 
THE AIRCRAFT FIXES SHOW THAT BONNIE IS MOVING FASTER AND HAS TURNED
WEST-NORTHWESTWARD.  THE INITIAL MOTION ESTIMATE IS 295/16.  BONNIE
IS FORECAST TO MAINTAIN THIS GENERAL HEADING DURING THE NEXT DAY OR
SO AS IT MOVES AROUND THE SOUTHWESTERN SIDE OF A MID- TO UPPER-
LEVEL RIDGE CENTERED OVER THE CAROLINAS.  THE TRACK GUIDANCE IS
GOOD AGREEMENT DURING FIRST 48 HOURS...BUT THERE IS SOME SPREAD IN
THE GUIDANCE AFTER LANDFALL ALONG THE NORTHERN GULF COAST.  THE
GUIDANCE IS NOTICEABLY FASTER...WHICH MAY BE IN PART FROM THE MORE
WESTWARD INITIAL LOCATION.  THE NEW NHC TRACK IS SIMILAR TO THE
PREVIOUS TRACK BUT IS FASTER THAN THE PREVIOUS ADVISORY.  THIS
REQUIRES THE ISSUANCE OF TROPICAL STORM WATCHES FOR A PORTION OF
THE NORTHERN GULF COAST. 

THE UPPER-AIR ENVIRONMENT AHEAD OF BONNIE IS LESS THAN IDEAL FOR
STRENGTHENING.  BONNIE IS EXPECTED TO REMAIN UNDER THE INFLUENCE OF
MODERATE TO STRONG SOUTHEASTERLY SHEAR DUE TO THE FLOW BETWEEN AN
UPPER-LEVEL LOW OVER THE GULF OF MEXICO AND THE AFOREMENTIONED
RIDGE.  THE UPPER-LEVEL FLOW IS FORECAST BY THE GLOBAL MODELS TO
WEAKEN IN 36-48 HOURS...WHICH COULD ALLOW FOR SOME STRENGTHENING OF
BONNIE.  THE OFFICIAL FORECAST IS BETWEEN THE MORE AGGRESSIVE
SHIPS/LGEM GUIDANCE AND THE HWRF/GFDL MODELS WHICH SHOWS LITTLE...
IF ANY...INTENSIFICATION.
  

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      23/0900Z 24.1N  78.6W    35 KT
 12HR VT     23/1800Z 25.0N  81.0W    40 KT
 24HR VT     24/0600Z 26.2N  84.1W    40 KT
 36HR VT     24/1800Z 27.6N  86.9W    45 KT
 48HR VT     25/0600Z 28.8N  89.1W    45 KT
 72HR VT     26/0600Z 31.5N  92.0W    25 KT...INLAND
 96HR VT     27/0600Z 34.5N  93.0W    20 KT...POST-TROP/REMNT LOW
120HR VT     28/0600Z...DISSIPATED
 
$$
FORECASTER BROWN/LANDSEA
 
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