384 
 WTPZ43 KNHC 260257
 TCDEP3
  
 HURRICANE MIRIAM DISCUSSION NUMBER  17
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132012
 800 PM PDT TUE SEP 25 2012
  
 MODERATE SOUTHWESTERLY VERTICAL SHEAR IS CONTINUING TO TAKE ITS TOLL
 ON MIRIAM THIS EVENING. THE CONVECTION IS LOSING ITS CENTRAL DENSE
 OVERCAST AND BEGINNING TO SHOW MORE OF A SHEAR PATTERN. DVORAK
 CURRENT INTENSITY ESTIMATES ARE AT 77 KT FROM TAFB AND 65 KT FROM
 SAB WHILE A 2214Z AMSU INTENSITY ESTIMATE FROM CIMSS WAS 72 KT. A
 BLEND OF THESE GIVES 70 KT AT THE ADVISORY TIME. 
 
 TWO FORTUITOUS AMSU AND SSMIS MICROWAVE PASSES PROVIDE A RELATIVELY
 CONFIDENT ESTIMATE THAT THE MOTION OF MIRIAM IS NEAR 310/4. THE
 CYCLONE IS CURRENTLY BEING STEERED PRIMARILY BY THE INFLUENCE OF A
 WEAK DEEP-LAYER RIDGE TO ITS EAST. A CONTINUED SLOW MOVEMENT TOWARD
 THE NORTH-NORTHWEST OR NORTH IS EXPECTED FOR THE NEXT TWO DAYS. AS
 THE SYSTEM TRANSFORMS INTO A REMNANT LOW...IT SHOULD TURN TOWARD
 THE NORTHWEST WHILE BEING ADVECTED ALONG IN THE LOW-LEVEL FLOW. THE
 TRACK PREDICTION IS SLIGHTLY SLOWER AND A BIT TO THE WEST OF THE
 PREVIOUS ADVISORY. THE NEW FORECAST IS ALSO CLOSE TO THE TRACK
 CONSENSUS EXCLUDING THE UKMET...AS THIS MODEL HAS AN
 UNREALISTICALLY SLOW SPEED IN COMPARISON TO ALL OF THE REMAINING
 GUIDANCE.
 
 MIRIAM SHOULD CONTINUE TO GRADUALLY WEAKEN UNDER THE COMBINED
 INFLUENCE OF MODERATE VERTICAL SHEAR...COOLING SSTS AND A MORE
 STABLE ATMOSPHERE.  THE CYCLONE SHOULD BECOME A REMNANT LOW AROUND
 THREE DAYS AS THE SSTS BY THAT TIME SHOULD BE AROUND 24C.  THE
 INTENSITY PREDICTION IS CLOSEST TO THE LGEM AND SHIPS STATISTICAL
 MODELS AND IS VERY SIMILAR TO THAT OF THE PREVIOUS ADVISORY.
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  26/0300Z 19.1N 115.2W   70 KT  80 MPH
  12H  26/1200Z 19.8N 115.6W   60 KT  70 MPH
  24H  27/0000Z 21.0N 115.7W   50 KT  60 MPH
  36H  27/1200Z 22.2N 116.2W   40 KT  45 MPH
  48H  28/0000Z 22.9N 116.5W   35 KT  40 MPH
  72H  29/0000Z 23.5N 117.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
  96H  30/0000Z 24.0N 117.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 120H  01/0000Z...DISSIPATED
  
 $$
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