000 WTPZ41 KNHC 290900 TCDEP1 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