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 313 
 WTPZ43 KNHC 090841
 TCDEP3
  
 HURRICANE CALVIN DISCUSSION NUMBER   8
 NWS NATIONAL HURRICANE CENTER MIAMI FL       EP032011
 200 AM PDT SAT JUL 09 2011
  
 INFRARED SATELLITE IMAGERY INDICATES THAT CALVIN HAS MAINTAINED A
 RAGGED AND IRREGULARLY SHAPED CENTRAL DENSE OVERCAST DURING THE
 PAST SEVERAL HOURS. HOWEVER...THE COVERAGE AND INTENSITY OF THE
 ASSOCIATED DEEP CONVECTION HAS BEEN DECREASING.  UW-CIMSS AND SHIPS
 MODEL ANALYSES ALSO INDICATE MODEST EASTERLY SHEAR CONTINUING TO
 AFFECT CALVIN...AND THE WESTWARD DISPLACEMENT OF THE MAIN
 CONVECTIVE MASS RELATIVE TO THE CENTER IN CONVENTIONAL AND
 MICROWAVE IMAGERY SEEMS TO CONFIRM THIS.  BASED UPON THE SLIGHTLY
 DEGRADED SATELLITE PRESENTATION AND A BLEND OF DVORAK T- AND
 CI-NUMBERS FROM TAFB/SAB...THE INITIAL INTENSITY IS LOWERED TO 65
 KT.  CALVIN HAS ALREADY REACHED A STRONG GRADIENT OF SEA SURFACE
 TEMPERATURES AND WILL BE MOVING OVER SSTS LESS THAN 25C AFTER 24
 HOURS. THIS...IN COMBINATION WITH A MORE STABLE LOWER TROPOSPHERE
 AND A CONTINUATION OF THE EASTERLY SHEAR...SHOULD RESULT IN STEADY
 WEAKENING TO A REMNANT LOW IN ABOUT 48 HOURS AND DISSIPATION WITHIN
 96 HOURS. THIS REASONING IS REFLECTED IN THE NHC OFFICIAL FORECAST
 WHICH IS ADJUSTED DOWNWARD IN AGREEMENT WITH A BLEND OF DYNAMICAL
 AND STATISTICAL MODEL OUTPUT.
 
 LATEST CENTER FIXES SUGGEST THAT CALVIN HAS BEEN SLOWING DOWN....AND
 THE INITIAL MOTION ESTIMATE IS 285/09. A MID-TROPOSPHERIC RIDGE
 EXTENDING FROM THE SOUTHERN PLAINS TO THE SUBTROPICAL EASTERN
 PACIFIC IS EXPECTED TO STEER CALVIN ON A GENERALLY WEST-
 NORTHWESTWARD TRACK DURING THE NEXT DAY OR TWO.  AS CALVIN BECOMES
 AN INCREASINGLY SHALLOW SYSTEM AFTER THAT...IT WILL DECOUPLE FROM
 THE DEEP-LAYER FLOW AND DECELERATE FURTHER AS IT ENCOUNTERS WEAKER
 LOW-LEVEL WINDS. THE NEW FORECAST IS BASICALLY AN UPDATE OF
 THE PREVIOUS ONE AND IS VERY NEAR THE MULTI-MODEL TVCN CONSENSUS.
 
 THE WIND RADII IN ALL QUADRANTS WERE MODIFIED BASED ON A 0505 UTC
 ASCAT PASS.
 
  
 FORECAST POSITIONS AND MAX WINDS
  
 INIT  09/0900Z 16.9N 110.1W   65 KT  75 MPH
  12H  09/1800Z 17.3N 111.6W   55 KT  65 MPH
  24H  10/0600Z 17.7N 113.2W   45 KT  50 MPH
  36H  10/1800Z 18.2N 114.5W   35 KT  40 MPH
  48H  11/0600Z 18.7N 115.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
  72H  12/0600Z 19.5N 117.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
  96H  13/0600Z...DISSIPATED
  
 $$
 FORECASTER KIMBERLAIN
  
 
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