000
WTPZ44 KNHC 071445
TCDEP4
 
TROPICAL STORM NARDA DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP142013
800 AM PDT MON OCT 07 2013
 
NARDA HAS BEEN INTENSIFYING...WITH A LONG CURVED CONVECTIVE BAND
WRAPPING AROUND MOST OF THE CIRCULATION.  MICROWAVE IMAGERY SHOWS A
POSSIBLE PARTIAL EYEWALL BUT WITH SOME SEPARATION BETWEEN THE LOW-
AND MID-LEVEL CENTERS. DVORAK INTENSITY ESTIMATES AT 1200 UTC ARE
45 AND 55 KT FROM SAB AND TAFB...RESPECTIVELY. BASED ON SOME
FURTHER INCREASE IN ORGANIZATION SINCE THAT TIME...THE HIGHER OF
THE TWO DVORAK ESTIMATES IS SELECTED FOR THIS ADVISORY.
 
RECENT FIXES SUGGEST THAT THE CENTER WAS FARTHER NORTH THAN
PREVIOUSLY INDICATED...AND A LONG-TERM MOTION ESTIMATE IS 285/13.
NARDA SHOULD BE STEERED WEST-NORTHWESTWARD UNDER THE WESTERN SIDE
OF A MID-LEVEL RIDGE OVER NORTHERN MEXICO. AS AN AMPLIFIED MID- TO
UPPER-LEVEL TROUGH DIGS NEAR THE U.S. WEST COAST IN A FEW
DAYS...THE CYCLONE SHOULD SLOW DOWN AND TURN NORTHWESTWARD. THE
ECMWF SHOWS A WEAKER SYSTEM SUCCUMBING TO SHEAR AND TURNING
WESTWARD SOONER THAN THE REST OF THE GUIDANCE...WHEREAS THE GFS
PREDICTS A DEEPER SYSTEM GAINING MORE LATITUDE BEFORE WEAKENING AND
TURNING WESTWARD. THE NHC OFFICIAL TRACK IS ADJUSTED TO THE RIGHT
TO ACCOUNT FOR THE INITIAL NORTHWARD RELOCATION AND TO BE CLOSER TO
THE MULTI-MODEL CONSENSUS...WHICH ASSUMES A DEEPER CYCLONE THAN
FORECAST BY THE ECMWF.
 
NARDA SHOULD BE MOVING OVER WARM BUT GRADUALLY DECREASING SEA
SURFACE TEMPERATURES AND PASSING UNDERNEATH AN UPPER-LEVEL RIDGE
AXIS DURING THE NEXT 24-36 HOURS.  THIS ENVIRONMENT SHOULD ALLOW
NARDA TO STRENGTHEN INTO A HURRICANE SOON.  IN ABOUT TWO
DAYS...WESTERLY VERTICAL SHEAR WILL INCREASE AND SHOULD BECOME EVEN
STRONGER BY THE END OF THE FORECAST PERIOD WHILE NARDA TRAVERSES
COOLER WATERS.  THIS SHOULD LEAD TO RAPID WEAKENING BY DAY 4...AND
NARDA IS FORECAST TO BECOME POST-TROPICAL BY DAY 5.  THE NHC
INTENSITY FORECAST IS RAISED OVER THE PREVIOUS ONE BASED ON CURRENT
TRENDS AND IS A LITTLE ABOVE THE GUIDANCE IN THE SHORT TERM.  WHILE
THE INTENSITY PREDICTION IS UNCHANGED AT LONG RANGE...IT IS VERY
SENSITIVE TO THE TRACK FORECAST...WITH A DEEPER/STRONGER CYCLONE
LIKELY MOVING FARTHER NORTH AND EXPERIENCING THE EFFECTS OF SHEAR
SOONER.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  07/1500Z 14.0N 122.5W   55 KT  65 MPH
 12H  08/0000Z 14.4N 124.2W   60 KT  70 MPH
 24H  08/1200Z 15.1N 126.4W   70 KT  80 MPH
 36H  09/0000Z 15.6N 127.9W   75 KT  85 MPH
 48H  09/1200Z 16.1N 128.9W   70 KT  80 MPH
 72H  10/1200Z 16.5N 129.5W   60 KT  70 MPH
 96H  11/1200Z 16.7N 130.4W   45 KT  50 MPH
120H  12/1200Z 16.7N 132.0W   30 KT  35 MPH...POST-TROPICAL
 
$$
FORECASTER KIMBERLAIN