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 621 
 WTPZ43 KNHC 242113
 TCDEP3
  
 HURRICANE MIRIAM DISCUSSION NUMBER  12...CORRECTED
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132012
 200 PM PDT MON SEP 24 2012
  
 CORRECTED STATUS AT DAY 5
 
 THE INTENSIFICATION PHASE THAT MIRIAM HAS BEEN UNDERGOING HAS COME
 TO AN END...AS THERE HAS BEEN A DEGRADATION IN THE SATELLITE
 APPEARANCE OF THE CYCLONE IN THE LAST FEW HOURS. CLOUD TOP
 TEMPERATURES HAVE GRADUALLY BEEN WARMING AND THE EYE HAS BECOME
 LESS DISTINCT.  A 1640 UTC TRMM IMAGE INDICATED THAT AN EYEWALL
 REPLACEMENT COULD BE UNDERWAY...WITH A SMALL INNER EYEWALL EVIDENT
 AND AN OUTER EYEWALL HAVING CONTRACTED SLIGHTLY TO A RADIUS OF 50 N
 MI. DVORAK T-NUMBERS HAVE LEVELED OFF AT 5.5 FROM BOTH SATELLITE
 AGENCIES...AND UW-CIMSS ADT CI VALUES HAVE DECREASED TO 5.6. THE
 INITIAL INTENSITY ESTIMATE IS HELD AT 105 KT...IN AGREEMENT WITH
 THESE DATA.
  
 THE EYE OF MIRIAM HAS WOBBLED A BIT TO THE LEFT DURING THE LAST FEW
 HOURS...AND HAS SLOWED IN FORWARD SPEED.  A LONGER-TERM AVERAGE OF
 CENTER FIXES GIVES AN INITIAL MOTION ESTIMATE OF 305/08.  MIRIAM
 SHOULD CONTINUE ON A SLOWER NORTHWESTWARD COURSE FOR THE NEXT DAY
 OR SO AS IT ROUNDS THE SOUTHWESTERN SIDE OF A MID-LEVEL RIDGE OVER
 NORTHERN MEXICO.  AFTER THAT TIME...MIRIAM SHOULD MOVE INTO A
 WEAKNESS ALONG 115W AND TURN NORTHWARD FOR A COUPLE OF DAYS.  THE
 INFLUENCE OF A MID- TO UPPER-LEVEL LOW FORMING OFFSHORE OF THE
 SOUTHERN CALIFORNIA COAST FROM DAYS 3-5 SHOULD PUSH THE TRACK OF
 MIRIAM NORTH-NORTHEASTWARD...OR EVEN NORTHEASTWARD...DURING THAT
 TIME.  NO SUBSTANTIVE CHANGES WERE MADE TO THE PREVIOUS
 FORECAST...WHICH IS WEIGHTED HEAVILY ON A BLEND OF THE ECMWF AND
 GFS MODELS.  AS IN PREVIOUS OFFICIAL FORECASTS...THIS IS NEAR THE
 RIGHT SIDE OF THE GUIDANCE ENVELOPE.
  
 IT IS UNCLEAR AS TO WHETHER THE CURRENT EYEWALL REPLACEMENT WILL
 CONTINUE.  IN ANY EVENT...A COMPLETION OF THE EYEWALL REPLACEMENT
 CYCLE IS NOT LIKELY TO OCCUR BEFORE MIRIAM REACHES MARGINALLY WARM
 WATERS AND SOME INCREASE IN WESTERLY SHEAR IN ABOUT 24 HOURS.
 WEAKENING IS EXPECTED DURING THE INTERIM AND AFTERWARDS AS THE
 CYCLONE MOVES CLOSE TO A STRONG GRADIENT OF SSTS AND EXPERIENCES
 MODERATE WESTERLY SHEAR.  A FURTHER INCREASE IN WESTERLY SHEAR
 ASSOCIATED THE ABOVEMENTIONED CLOSED MID- TO UPPER-LEVEL CYCLONE TO
 THE WEST OF MIRIAM WILL LIKELY OCCUR LATE IN THE PERIOD.  THERE IS
 NOW A GENERAL AGREEMENT OF BOTH THE ECWMF AND GFS GUIDANCE THAT
 THIS WILL RESULT IN A DECOUPLING OF THE CYCLONE AND A RAPID
 WEAKENING.  THE NHC INTENSITY FORECAST HAS BEEN REDUCED RELATIVE TO
 THE PREVIOUS ONE...REPRESENTING AN AVERAGE OF THE SHIPS/LGEM AND
 THE LATEST INTENSITY CONSENSUS AIDS.  REMNANT LOW STATUS IN
 INDICATED ON DAY 5.
  
  
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  24/2100Z 18.1N 113.5W  105 KT 120 MPH
  12H  25/0600Z 18.5N 114.2W  100 KT 115 MPH
  24H  25/1800Z 19.3N 114.8W   90 KT 105 MPH
  36H  26/0600Z 20.1N 115.0W   80 KT  90 MPH
  48H  26/1800Z 21.1N 115.1W   70 KT  80 MPH
  72H  27/1800Z 23.4N 115.2W   55 KT  65 MPH
  96H  28/1800Z 25.5N 114.4W   40 KT  45 MPH
 120H  29/1800Z 27.5N 113.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
  
 $$
 FORECASTER KIMBERLAIN
  
 
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