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Tropical Storm IVO (Text)

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TROPICAL STORM IVO DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092013
800 AM PDT FRI AUG 23 2013

CONVECTION HAS INCREASED NEAR THE CENTER OF THE CYCLONE DURING THE
PAST SEVERAL HOURS...WITH FIRST-LIGHT VISIBLE IMAGERY SHOWING THE
CENTER NOW EMBEDDED IN THE CONVECTIVE OVERCAST.  ASCAT DATA LAST
NIGHT SHOWED SOME 35 KT VECTORS WELL TO THE EAST OF THE CENTER. 
BASED ON THESE DATA AND THE INCREASED ORGANIZATION...THE INITIAL
INTENSITY IS INCREASED TO 35 KT.  THE SCATTEROMETER DATA SHOWED
THAT IVO HAS SOME CHARACTERISTICS OF MONSOON CYCLONES OF THE
EASTERN HEMISPHERE...INCLUDING A VERY LARGE AREA OF 20-30 KT WINDS
TO THE SOUTH AND EAST OF THE CENTER.  IT SHOULD ALSO BE NOTED THAT
THE CIRCULATION IS ELONGATED...WITH A TROUGH EXTENDING
NORTHEASTWARD FROM THE CENTER TO JUST NORTH OF SOCORRO ISLAND.
 
MICROWAVE IMAGERY SUGGESTS THE CENTER IS A LITTLE TO THE EAST OF THE
PREVIOUS ADVISORY POSITION...AND THE INITIAL MOTION IS A SOMEWHAT
UNCERTAIN 360/4.  IVO IS ON THE WESTERN SIDE OF A LOW/MID-LEVEL
RIDGE OVER MEXICO...AND IT IS EXPECTED TO MOVE TOWARD AN AREA OF
SOUTHERLY STEERING FLOW BETWEEN A DEEP-LAYER RIDGE OVER THE CENTRAL
UNITED STATES AND A DEEP-LAYER TROUGH WEST OF CALIFORNIA.  THIS
COMBINATION SHOULD CAUSE THE CYCLONE TO MOVE GENERALLY NORTH-
NORTHWESTWARD FOR THE NEXT 48 HOURS.  AFTER THAT... THERE IS
SIGNIFICANT DIVERGENCE IN THE GUIDANCE.  THE GFS...HWRF...NAVGEM...
AND CANADIAN MODELS FORECAST IVO TO MOVE NORTHWARD ACROSS NORTHERN
BAJA CALIFORNIA INTO THE SOUTHWESTERN UNITED STATES.  ON THE OTHER
HAND...THE UKMET AND ECMWF MODELS FORECAST THE SYSTEM TO SHEAR
APART...WITH THE LOW-LEVEL CENTER STALLING OVER THE PACIFIC WEST OF
BAJA CALIFORNIA.  THE TRACK FORECAST FOLLOWS THE LATTER SCENARIO
AND CALLS FOR A SLOW NORTH-NORTHWESTWARD MOTION AFTER 48 HR.  THE
NEW FORECAST TRACK IS SHIFTED TO THE EAST OF THE PREVIOUS TRACK
BASED ON THE CURRENT POSITION AND MOTION.
 
GRADUAL STRENGTHENING APPEARS LIKELY UNTIL IVO REACHES COLDER SEA
SURFACE TEMPERATURES IN ABOUT 36 HOURS.  AFTER THAT...THE CYCLONE
IS EXPECTED TO DEGENERATE TO A REMNANT LOW OVER THE COLD WATERS
WEST OF BAJA CALIFORNIA.  THE NEW INTENSITY FORECAST IS UNCHANGED
FROM THE PREVIOUS FORECAST.
 
MOISTURE ASSOCIATED WITH IVO IS EXPECTED TO SURGE NORTHWARD OVER THE
BAJA CALIFORNIA PENINSULA...NORTHWESTERN MEXICO AND THE
SOUTHWESTERN UNITED STATES DURING THE NEXT FEW DAYS...INCREASING
THE POSSIBILITY OF HEAVY RAINS AND FLASH FLOODING.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/1500Z 18.7N 112.4W   35 KT  40 MPH
 12H  24/0000Z 19.8N 112.6W   35 KT  40 MPH
 24H  24/1200Z 21.5N 113.0W   40 KT  45 MPH
 36H  25/0000Z 23.3N 113.6W   40 KT  45 MPH
 48H  25/1200Z 25.1N 114.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  26/1200Z 27.0N 115.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  27/1200Z 28.0N 116.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  28/1200Z...DISSIPATED
 
$$
FORECASTER BEVEN
 
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