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TROPICAL STORM CALVIN DISCUSSION NUMBER   4
NATIONAL WEATHER SERVICE MIAMI FL
2 AM PDT MON JUL 26 1999

...CORRECTION TO CHANGE TROPICAL DEPRESSION CALVIN TO TROPICAL 
STORM AND FOR INITIAL POSITION...
 
THE OVERALL ORGANIZATION OF TROPICAL DEPRESSION FIVE-E HAS NOT
IMPROVED MARKELY OVER THE LAST 6 HOURS OR SO.  THE SYSTEM REMAINS
IN A SHEARED STATE WITH THE CENTER LOCATED 0.5 TO 0.75 DEG FROM
THE EDGE OF THE DEEP CONVECTION.  DVORAK CLASSIFICATIONS FROM
BOTH TAFB AND SAB ARE 35 KT...AND TROPICAL DEPRESSION FIVE IS
UPGRADED TO TROPICAL STORM CALVIN.  THE 00Z AVN MODEL SUGGEST
THAT THE WESTERLY SHEAR WILL PERSIST THROUGH THE FORECAST PERIOD.
THIS COUPLED WITH THE PROGRESSIVELY COOLER SST/S...NEAR 23C BY
36 HOURS...SHOULD PRECLUDE ANY SIGNIFICANT STRENGTHENING.  THE
OFFICIAL FORECAST KEEPS CALVIN A MINIMUM TROPICAL STORM FOR 24
HOURS.
 
THE INITIAL MOTION ESTIMATE IS 295/12.  MOST OF THE DYNAMICAL MODEL
GUIDANCE SHOWS A WEST-NORTHWEST HEADING THROUGH 24 HOURS WITH A TURN
TO THE NORTHWEST...THEN NORTH-NORTHWEST BY 48 HOURS IN RESPONSE TO
THE MID-LEVEL TROUGH SEEN IN WATER VAPOR IMAGERY NEAR 30N 130W
DIGGING SOUTHWARD. THE OFFICIAL FORECAST TRACK CALLS FOR A CONTINUED
WEST-NORTHWEST MOTION WITH SOME DECELERATION BY THE END OF THE
PERIOD...AND REPRESENTS A SLIGHT RIGHTWARD ADJUSTED TO THE PREVIOUS
PACKAGE. HOWEVER...THIS TRACK IS STILL LEFT OF MOST OF THE DYNAMICAL
GUIDANCE SINCE THE CYCLONE SHOULD REMAIN WEAK...AND THUS BE STEERED
BY THE LOW-LEVEL ENVIRONMENTAL FLOW.
 
GUINEY
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     26/0900Z 16.8N 119.9W    35 KTS
12HR VT     26/1800Z 17.6N 121.5W    35 KTS
24HR VT     27/0600Z 18.4N 123.3W    35 KTS
36HR VT     27/1800Z 19.2N 125.2W    30 KTS
48HR VT     28/0600Z 20.0N 127.0W    30 KTS
72HR VT     29/0600Z 21.0N 130.0W    30 KTS
 
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