Tropical Storm JOHN

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TROPICAL STORM JOHN DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP112006
200 AM PDT TUE AUG 29 2006
 
THE SATELLITE APPEARANCE OF JOHN CONTINUES TO IMPROVE WITH AN
EXPANDING CDO OVER THE CENTER.  IN FACT...A 0207 UTC SSMIS MICROWAVE 
OVERPASS DETECTED A SMALL EYE FEATURE.  DVORAK INTENSITY ESTIMATES
CONTINUE TO INCREASE AND ARE NOW 55 KT FROM TAFB AND SAB...AND 45
KT FROM AFWA.  THE INITIAL INTENSITY IS SET AT 60 KT...A LITTLE
HIGHER THAN THE DVORAK ESTIMATES DUE TO THE EYE FEATURE SEEN IN THE
MICROWAVE IMAGERY.  JOHN APPEARS TO BE GOING THROUGH A PERIOD OF
RAPID INTENSIFICATION AND THE FUTURE ENVIRONMENT LOOKS VERY
FAVORABLE FOR FURTHER STRENGTHENING. ALL AVAILABLE INTENSITY
GUIDANCE SHOWS JOHN BECOMING A MAJOR HURRICANE IN ABOUT 48-60
HOURS.  THE INTENSITY FORECAST FOLLOWS THE GUIDANCE CLOSELY AND 
WAS ADJUSTED SLIGHTLY UPWARD FROM THE PREVIOUS ADVISORY. LATE IN 
THE FORECAST...AS JOHN APPROACHES COOLER WATERS...WEAKENING IS
INDICATED BUT AT A SLOWER RATE THAN THE PREVIOUS OFFICIAL FORECAST. 
 
THE INITIAL MOTION IS ESTIMATED TO BE 290/06. JOHN IS FORECAST
CONTINUE ON A GENERAL WEST-NORTHWESTWARD HEADING AROUND THE
SOUTHWESTERN PERIPHERY OF A MID-TROPOSPHERIC RIDGE EXPECTED TO
BUILD OVER NORTHERN MEXICO.  THERE IS A LITTLE LESS SPREAD IN THE
TRACK GUIDANCE FOR THIS CYCLE.  THE LATEST RUN OF THE GFDL MODEL
SHIFTED WESTWARD...BUT IT REMAINS ON THE RIGHT SIDE OF THE
DYNAMICAL MODEL ENVELOPE...WHILE THE GFS REMAINS ON THE LEFT.  THE
FORECAST TRACK IS SIMILAR TO THE PREVIOUS ADVISORY AND IT CONTINUES
TO SHOW JOHN PARALLELING THE COAST OF MEXICO FOR THE NEXT SEVERAL
DAYS.  THE OFFICIAL TRACK REMAINS JUST TO THE RIGHT OF THE MODEL
CONSENSUS AND CLOSE TO THE GFDL AND FLORIDA STATE SUPERENSEMBLE.  

THERE HAS BEEN NO CHANGE TO THE TROPICAL STORM WATCH ALONG THE
SOUTHERN COAST OF MEXICO.  AS JOHN STRENGTHENS THE TROPICAL STORM
FORCE WIND RADII ARE EXPECTED TO INCREASE.  THE WATCH AREA MAY NEED
TO BE EXPANDED WESTWARD LATER TODAY AND INTERESTS ALONG THE COAST
OF MEXICO SHOULD CONTINUE TO MONITOR THE PROGRESS OF JOHN.
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      29/0900Z 13.9N  97.8W    60 KT
 12HR VT     29/1800Z 14.2N  98.9W    75 KT
 24HR VT     30/0600Z 14.8N 100.5W    85 KT
 36HR VT     30/1800Z 15.7N 102.4W    95 KT
 48HR VT     31/0600Z 16.9N 104.4W   105 KT
 72HR VT     01/0600Z 19.5N 108.3W   100 KT
 96HR VT     02/0600Z 21.0N 111.5W    85 KT
120HR VT     03/0600Z 21.5N 115.0W    65 KT
 
$$
FORECASTER BROWN/STEWART
 
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