Tropical Storm SONIA

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TROPICAL STORM SONIA DISCUSSION NUMBER  10
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182013
700 AM PST SUN NOV 03 2013

THE AREA OF DEEP CONVECTION THAT DEVELOPED OVERNIGHT IN ASSOCIATION
WITH SONIA HAS EXPANDED THIS MORNING.  EARLY MORNING VISIBLE
SATELLITE IMAGES SUGGEST THAT THE CENTER IS LOCATED JUST BENEATH 
THE SOUTHEAST PORTION OF THE LARGE CONVECTIVE MASS.  BASED ON THE
SLIGHTLY IMPROVED ORGANIZATION AND DVORAK T-NUMBERS OF 2.5 AND 3.0
FROM SAB AND TAFB...RESPECTIVELY...THE INITIAL WIND SPEED IS
INCREASED TO 40 KT.  THE RECENT STRENGTHENING APPEARS TO BE THE
RESULT OF DECREASING SHEAR AS SONIA MOVED BENEATH AN UPPER-LEVEL
RIDGE AXIS OVERNIGHT.  THIS RELAXATION IN SHEAR IS EXPECTED TO BE
SHORT-LIVED AS SOUTHWESTERLY UPPER-LEVEL WINDS AHEAD OF A MID- TO
UPPER-LEVEL TROUGH WILL CAUSE A SUBSTANTIAL INCREASE IN SHEAR
TONIGHT....AND NO SIGNIFICANT ADDITIONAL STRENGTHENING IS EXPECTED.   
SOME WEAKENING IS POSSIBLE AROUND THE TIME SONIA REACHES THE COAST
AS THE SHEAR IS EXPECTED TO CAUSE THE LOW- AND MID-LEVEL CENTERS TO
DECOUPLE.  SONIA IS FORECAST TO DISSIPATE SHORTLY AFTER LANDFALL
OVER THE MOUNTAINS OF WESTERN MEXICO. 

THE INITIAL MOTION IS STILL NORTHWARD OR 005 DEGREES AT 7 KT.  SONIA
SHOULD TURN NORTH-NORTHEASTWARD VERY SOON AS DEEP LAYER
SOUTHWESTERLY FLOW STRENGTHENS AHEAD OF A MID-LATITUDE TROUGH MOVING
INTO THE SOUTHWESTERN UNITED STATES AND NORTHERN MEXICO.  SONIA
SHOULD BEGIN TO ACCELERATE LATER TODAY AND MAKE LANDFALL ALONG THE
COAST OF MAINLAND MEXICO MONDAY MORNING.  THE TRACK GUIDANCE IS IN
GOOD AGREEMENT ON THIS SCENARIO AND NO SIGNIFICANT CHANGES WERE 
REQUIRED FROM THE PREVIOUS NHC ADVISORY. 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  03/1500Z 19.9N 109.8W   40 KT  45 MPH
 12H  04/0000Z 21.6N 109.1W   40 KT  45 MPH
 24H  04/1200Z 23.7N 107.6W   35 KT  40 MPH
 36H  05/0000Z 25.9N 106.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  05/1200Z...DISSIPATED
 
$$
FORECASTER BROWN
 
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