HOME	PRODUCTS	FORECASTS	IMAGERY	ABOUT TPC	RECONNAISSANCE

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM
TROPICAL STORM JOHN DISCUSSION NUMBER   3
NATIONAL WEATHER SERVICE MIAMI FL
8 PM PDT MON AUG 28 2000
 
TROPICAL STORM JOHN HAS BECOME BETTER ORGANIZED DURING THE PAST 6
HOURS AND THE INITIAL INTENSITY IS INCREASED TO 55 KT BASED ON A
SATELLITE INTENSITY ESTIMATE OF 55 KT FROM BOTH TAFB AND SAB. 
UPPER-LEVEL OUTFLOW IS GOOD IN THE EAST SEMICIRCLE AND FAIR...BUT
IMPROVING...TO THE WEST.

THE INITIAL MOTION IS 295/05.  THERE IS NO SIGNIFICANT CHANGE TO THE
PREVIOUS FORECAST TRACK OR REASONING.  SATELLITE FIXES HAVE BEEN
COMING IN ON TRACK...SO THIS FORECAST IS SIMPLY AN EXTENSION OF THE
PREVIOUS TRACK.  ALTHOUGH THE MID-LEVEL RIDGE TO THE NORTH IS
WEAK...THE LOW-LEVEL SUBTROPICAL RIDGE REMAINS QUITE STRONG AND JOHN
SHOULD BE STEERED ON A GENERAL WESTWARD TRACK BY THE EASTERLY FLOW
TO THE NORTH.  THIS IS CONSISTENT WITH THE SHALLOW AND MEDIUM BAM
MODELS...AND BETWEEN THE GFDN AND GFDL MODELS.

JOHN HAS BEEN UNDERGOING A PERIOD OF RAPID INTENSIFICATION FOR THE
PAST 12 HOURS...BUT IS NOW BEGINNING TO SHOW SIGNS OF SHIFTING TO A
MORE NORMAL RATE OF INTENSIFICATION.  A SMALL CDO FEATURE WITH
COLD...-80C OR COLDER...OVERSHOOTING TOPS HAS DEVELOPED NEAR THE
SYSTEM CENTER WHICH INDICATES JOHN IS STRENGTHENING.  ALSO...A
DISTURBANCE ABOUT 600 MILES TO THE WEST HAS BEEN RUNNING
INTERFERENCE AND DEFLECTING STRONG 200 MB SHEARING WINDS TO THE
NORTH OF JOHN.  THIS HAS ALLOWED THE OUTFLOW TO IMPROVE AND EXPAND
TO THE WEST...WHICH SHOULD FURTHER ALLOW JOHN TO REACH HURRICANE
INTENSITY IN THE NEXT 12 HOURS.  HOWEVER...THE WESTERN DISTURBANCE
HAS SHOWN SIGNS OF WEAKENING THE PAST FEW HOURS WHICH MAY ALLOW THE 
STRONG UPPER-LEVEL WESTERLIES TO IMPINGE ON THE WEST SIDE OF JOHN IN
ABOUT 24 HOURS.  THE OFFICIAL FORECAST IS CLOSE TO THE SHIPS MODEL
IN TAKING JOHN TO 70 KT...THEN HOLDING STEADY AFTERWARDS EVEN THOUGH
THE SHIPS MODEL INDICATES THE SHEAR WILL BE LESS THAN 10 KT.

NOTE...THE 12 FT SEAS RADII WERE INCREASED BASED ON A 00Z REPORT
FROM SHIP PJOX LOCATED ABOUT 140 NM SOUTHEAST OF JOHN.

FORECASTER STEWART
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     29/0300Z 15.8N 138.8W    55 KTS
12HR VT     29/1200Z 16.1N 139.5W    65 KTS
24HR VT     30/0000Z 16.3N 140.2W    70 KTS
36HR VT     30/1200Z 16.6N 141.0W    70 KTS
48HR VT     31/0000Z 16.8N 142.0W    65 KTS
72HR VT     01/0000Z 17.0N 143.5W    60 KTS
 
NNNN