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 956 
 WTPZ43 KNHC 240847
 TCDEP3
  
 HURRICANE MIRIAM DISCUSSION NUMBER  10
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132012
 200 AM PDT MON SEP 24 2012
  
 MIRIAM HAS CONTINUED TO RAPIDLY STRENGTHEN. A SMALL 10 N MI DIAMETER
 COULD-FILLED EYE IS EMBEDDED IN THE NORTHWEST QUADRANT OF A COLD
 CENTRAL DENSE OVERCAST FEATURE THAT HAS BECOME MORE CIRCULAR OVER
 THE PAST FEW HOURS. SATELLITE INTENSITY ESTIMATES ARE A CONSENSUS
 T5.0/90 KT FROM TAFB AND SAB...AND THE LATEST UW-CIMSS ESTIMATE IS
 T5.6/105 KT. BASED ON THESE DATA...THE INITIAL INTENSITY HAS BEEN
 INCREASED TO 90 KT...WHICH COULD BE ON THE CONSERVATIVE SIDE.
 
 THE INITIAL MOTION ESTIMATE 305/11 KT. MIRIAM IS BASICALLY ON
 TRACK...SO THERE IS NO CHANGE TO THE PREVIOUS FORECAST TRACK
 THROUGH 36 HOURS. AFTER THAT...HOWEVER...THE TRACK HAS BEEN SHIFTED
 TO THE EAST OF AND A LITTLE FASTER THAN THE PREVIOUS ADVISORY DUE
 TO MIRIAM FORECAST TO BE A DEEPER AND MORE ROBUST CYCLONE SIMILAR
 TO WHAT THE GFS AND ECMWF MODELS ARE INDICATING. THE UKMET MODEL
 WAS COMPLETELY DISCOUNTED SINCE IT WAS WAS POORLY INITIALIZED AND
 IS ONLY FORECASTING A VERY WEAK AND SHALLOW CYCLONE THAT DISSIPATES
 AND MOVES SLOWLY NORTHWEST AND WESTWARD WITH TIME...WHICH HAS
 RESULTED IN A DEGRADATION OF THE CONSENSUS MODELS TV15 AND TVCE. A
 BROAD MID-LEVEL TROUGH CURRENTLY ALONG THE U.S. WEST COAST IS
 FORECAST TO SLOWLY AMPLIFY SOUTHWARD OFF THE COAST OF BAJA
 CALIFORNIA AND CREATE A LARGE BREAK IN THE SUBTROPICAL RIDGE TO THE
 NORTH OF THE CYCLONE BY 48 HOURS. THIS CHANGING FLOW PATTERN IS
 EXPECTED TO GRADUALLY TURN MIRIAM NORTHWARD BY 72 HOURS...AND THEN
 RECURVE THE SYSTEM SLOWLY TO THE NORTHEAST TOWARD BAJA CALIFORNIA
 ON DAYS 4 AND 5. GIVEN THE PERSISTENT WEST BIAS OF THE UKMET...
 GFDL...AND HWRF MODELS...THE OFFICIAL FORECAST IS SIMILAR TO BUT
 SLOWER THAN A BLEND OF THE GFS...GFS-ENSEMBLE MEAN...AND ECMWF
 FORECAST TRACKS.
 
 GIVEN THE SMALL-DIAMETER EYE AND LOW SHEAR EXPECTED FOR THE NEXT 12
 HOURS OR SO...ADDITIONAL RAPID STRENGTHENING INTO A MAJOR HURRICANE
 SEEMS HIGHLY PLAUSIBLE. IT IS POSSIBLE THAT MIRIAM COULD EVEN REACH
 CATEGORY 4 INTENSITY...BUT THE RATHER SMALL EYE COULD NEGATE THAT
 POSSIBILITY DUE TO A PROBABLE EYEWALL REPLACEMENT CYCLE SOMETIME
 DURING THE NEXT 24 HOURS. BY 36 HOURS AND BEYOND...MODERATE
 SOUTHWESTERLY SHEAR AHEAD OF THE AFOREMENTIONED MID-/UPPER-LEVEL
 TROUGH IS EXPECTED TO INDUCE GRADUAL WEAKENING. HOWEVER...THE
 WEAKENING TREND IS NOT EXPECTED TO BE AS FAST AS INDICATED IN
 PREVIOUS ADVISORIES NOW THAT MIRIAM IS FORECAST TO BE FARTHER EAST
 AND...THEREFORE...OVER WARMER SSTS. THE NHC INTENSITY FORECAST IS
 ABOVE ALL OF THE GUIDANCE FOR THE NEXT 24 HOURS...AND THEN FOLLOWS
 THE INTENSITY CONSENSUS MODELS TV15 AND IVCN.
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  24/0900Z 17.3N 112.2W   90 KT 105 MPH
  12H  24/1800Z 18.0N 113.2W  105 KT 120 MPH
  24H  25/0600Z 18.8N 114.3W  110 KT 125 MPH
  36H  25/1800Z 19.6N 114.8W  100 KT 115 MPH
  48H  26/0600Z 20.4N 115.2W   90 KT 105 MPH
  72H  27/0600Z 22.2N 115.5W   75 KT  85 MPH
  96H  28/0600Z 24.0N 115.5W   60 KT  70 MPH
 120H  29/0600Z 25.5N 114.5W   50 KT  60 MPH
  
 $$
 FORECASTER STEWART
  
 
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