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Tropical Storm JOYCE


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TROPICAL STORM JOYCE DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL102012
1100 AM AST THU AUG 23 2012
 
THE CLOUD PATTERN ASSOCIATED WITH THE DEPRESSION HAS INCREASED IN
ORGANIZATION THIS MORNING.  ANIMATION OF VISIBLE SATELLITE IMAGERY
SUGGESTS THAT THE LOW-LEVEL CENTER IS ON THE SOUTH SIDE OF A FAIRLY
CIRCULAR MASS OF COLD-TOPPED CONVECTION.  DVORAK T-NUMBERS FROM
TAFB AND SAB HAVE INCREASED TO A CONSENSUS 2.5...AND THE DEPRESSION
IS UPGRADED TO A TROPICAL STORM WITH 35 KT WINDS.
 
THE INITIAL MOTION ESTIMATE IS A STEADY 295/14.  GLOBAL MODELS SHOW
JOYCE CONTINUING ON A WEST-NORTHWESTWARD COURSE DURING THE NEXT
COUPLE OF DAYS...ON THE SOUTH SIDE OF A SUBTROPICAL RIDGE OVER THE
CENTRAL ATLANTIC.  IN 3-4 DAYS...JOYCE SHOULD REACH THE WESTERN
PERIPHERY OF THE RIDGE WHICH SHOULD CAUSE THE STORM TO TURN
NORTHWESTWARD AND NORTHWARD.  LATE IN THE FORECAST PERIOD...AN
AMPLIFYING SHORTWAVE TROUGH MOVING THROUGH THE GREAT LAKES SHOULD
ERODE THE WESTERN EXTENSION OF THE RIDGE OVER THE WESTERN
ATLANTIC...ALLOWING JOYCE TO RECURVE INTO THE WESTERLIES.  THE
TRACK GUIDANCE IS IN EXCELLENT AGREEMENT ON THIS SCENARIO...BUT
DIFFERENCES ARISE AS A RESULT OF THE FORECAST DEPTH OF THE CYCLONE.
THE OFFICIAL TRACK GUIDANCE CONTINUES TO RELY ON A BLEND OF THE
ECWMF AND GFS SOLUTIONS...WHICH FAVOR A STRONGER REPRESENTATION OF
JOYCE THAN THE GFDL/HWRF SOLUTIONS WHICH HAVE BEEN FORECASTING A
MUCH WEAKER SYSTEM.
 
THE INTENSITY FORECAST COULD BE CHALLENGING.  THE PROXIMITY OF JOYCE
TO A MID- TO UPPER-LEVEL LOW AND ASSOCIATED TROUGH TO THE WEST IS
IMPARTING SOUTHERLY SHEAR OVER THE CYCLONE.  A DRY SAHARAN AIR
LAYER WITHIN THE TROUGH IS ALSO WRAPPING AROUND THE SOUTHWESTERN
PART OF THE CIRCULATION.  WITH THE CYCLONE FORECAST TO GET CLOSER
TO THE TROUGH IN THE NEXT COUPLE OF DAYS...LITTLE ADDITIONAL
INTENSIFICATION IS EXPECTED IN THE SHORT TERM.  IN ABOUT 4
DAYS...GLOBAL MODELS SHOW THE POSSIBILITY OF A DECREASE IN SHEAR
OVER JOYCE IF IT IS FAR ENOUGH AWAY FROM THE UPPER-LEVEL OUTFLOW OF
ISAAC.  THE OFFICIAL NHC FORECAST IS SIMILAR TO BUT A LITTLE BELOW
THE LGEM/SHIPS OUTPUT...SHOWING LITTLE CHANGE IN STRENGTH IN
THE SHORT-TERM WITH SOME INTENSIFICATION LATER ON.
 
THIS TIES THE SECOND-EARLIEST FORMATION OF THE TENTH NAMED TROPICAL
STORM OF A SEASON.  IN 2005...TROPICAL STORM JOSE FORMED ON 22
AUGUST AND IN 1995 TROPICAL STORM JERRY FORMED ON THIS DATE.
 

FORECAST POSITIONS AND MAX WINDS
 
INIT  23/1500Z 15.2N  42.2W   35 KT  40 MPH
 12H  24/0000Z 16.0N  44.2W   40 KT  45 MPH
 24H  24/1200Z 17.1N  46.9W   40 KT  45 MPH
 36H  25/0000Z 18.4N  49.6W   40 KT  45 MPH
 48H  25/1200Z 19.9N  52.7W   40 KT  45 MPH
 72H  26/1200Z 23.9N  59.1W   40 KT  45 MPH
 96H  27/1200Z 28.5N  63.7W   45 KT  50 MPH
120H  28/1200Z 33.5N  62.4W   50 KT  60 MPH
 
$$
FORECASTER KIMBERLAIN
 
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