000
WTPZ44 KNHC 080840
TCDEP4
 
TROPICAL STORM NARDA DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP142013
200 AM PDT TUE OCT 08 2013
 
A SERIES OF RECENT MICROWAVE IMAGES INDICATE THAT THE LOW-LEVEL
CENTER OF NARDA IS LOCATED ON THE NORTHEASTERN EDGE OF A SMALL AREA
OF DEEP CONVECTION.  DVORAK CURRENT INTENSITY ESTIMATES ARE STILL
55 KT FROM TAFB AND SAB...ALTHOUGH THE FINAL T-NUMBER FROM SAB HAS
FALLEN TO 35 KT.  IN ADDITION...THE LATEST OBJECTIVE ADT AND SATCON
ESTIMATES FROM THE UNIVERSITY OF WISCONSIN ARE AROUND 45 KT.  BASED
ON THESE NUMBERS...THE INITIAL INTENSITY IS LOWERED TO 50 KT...BUT
THIS COULD STILL BE A LITTLE GENEROUS.

A SIGNIFICANT CHANGE TO THE INTENSITY FORECAST WAS REQUIRED IN THIS
ADVISORY.  ALTHOUGH DEEP-LAYER SHEAR IS EXPECTED TO BE LOW FOR
ANOTHER 36 HOURS...NARDA APPEARS TO BE STRUGGLING A BIT DUE TO A
MARGINAL THERMODYNAMIC ENVIRONMENT.  AS THE STORM CONTINUES
WESTWARD...IT WILL BE RUNNING INTO AN EVEN DRIER AND MORE STABLE
AIR MASS...AND THE PROSPECTS FOR FURTHER INTENSIFICATION HAVE
DECREASED SIGNIFICANTLY.  IN ADDITION...THE GLOBAL MODELS INDICATE
THAT A MID-LEVEL BLOCKING RIDGE WILL DEVELOP TO THE WEST OF NARDA
IN ABOUT 48 HOURS AND CAUSE THE LOW- AND MID-LEVEL CIRCULATIONS TO
DECOUPLE.  AS A RESULT...THE INTENSITY GUIDANCE NO LONGER SHOWS ANY
STRENGTHENING.  THE UPDATED NHC INTENSITY FORECAST MAINTAINS AN
INTENSITY OF 50 KT FOR THE NEXT 24 HOURS WHILE THE VERTICAL SHEAR
REMAINS LOW...BUT THEN SHOWS RELATIVELY FAST WEAKENING TO REMNANT
LOW STATUS BY DAY 4.

NARDA IS LOCATED TO THE SOUTH OF A WEAKENING MID-LEVEL RIDGE...AND
ITS CURRENT MOTION IS 290/11 KT.  A MID- TO UPPER-LEVEL TROUGH IS
FORECAST TO AMPLIFY ALONG THE U.S. WEST COAST OVER THE NEXT COUPLE
OF DAYS...LEAVING NARDA IN A COL REGION TO THE SOUTH OF THE TROUGH
AND BETWEEN TWO MID-LEVEL ANTICYCLONES TO ITS EAST AND WEST.  THE
LACK OF SIGNIFICANT STEERING FLOW WILL CAUSE THE CYCLONE TO SLOW
DOWN AND LIKELY DRIFT WESTWARD BY 48 AND 72 HOURS.  AFTER THAT
TIME...NARDA WILL BE WEAKENING...AND THE REMNANT LOW SHOULD
ACCELERATE WESTWARD WITHIN THE TRADES BY DAYS 4 AND 5. 

FORECAST POSITIONS AND MAX WINDS
 
INIT  08/0900Z 15.3N 125.4W   50 KT  60 MPH
 12H  08/1800Z 15.7N 126.9W   50 KT  60 MPH
 24H  09/0600Z 16.1N 128.3W   50 KT  60 MPH
 36H  09/1800Z 16.3N 129.2W   45 KT  50 MPH
 48H  10/0600Z 16.3N 129.7W   40 KT  45 MPH
 72H  11/0600Z 16.3N 130.6W   30 KT  35 MPH
 96H  12/0600Z 16.0N 132.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  13/0600Z 15.5N 135.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
FORECASTER BERG