ZCZC MIATCDAT3 ALL TTAA00 KNHC DDHHMM TROPICAL STORM MITCH DISCUSSION NUMBER 4 NATIONAL WEATHER SERVICE MIAMI FL 5 PM EDT THU OCT 22 1998 THE HURRICANE HUNTERS CONFIRMED THE PREVIOUS ESTIMATE FOR THE LOCATION OF THE CENTER OF CIRCULATION. THE CYCLONE IS APPARENTLY MOVING IN A SMALL CYCLONIC LOOP. FOR NOW...IT WILL BE CONSIDERED QUASI-STATIONARY. THE AIRCRAFT ENCOUNTERED 51 KT WINDS AT THE 1500 FT FLIGHT LEVEL. USING THIS...THE SYSTEM IS UPGRADED TO TROPICAL STORM MITCH WITH 40 KT SURFACE WINDS. THE CIRCULATION IS QUITE SMALL WITH RADIUS OF MAXIMUM WINDS REPORTED TO BE 8 NM AT FLIGHT LEVEL. THE 12Z AVN RESEMBLES THE PREDECESSORS. SECONDARY SHORT-WAVE TROUGHS MOVING OFFSHORE FROM THE U.S. SE COAST LEAVE A WEAKNESS IN THE HEIGHT FIELD IN THAT AREA AFTER THE INITIAL STRONG SYSTEM PASSES OFFSHORE. A MINOR RIDGE SETTLES IN OVER THE SE UNITED STATES. THIS ALLOWS FOR A SLOW NW TO NNW MOVEMENT DURING THE NEXT TWO DAYS...AS SHOWN BY ALL TRACK GUIDANCE AND THE OFFICIAL FORECAST. IN CONTRAST TO THE RUN AT 06Z...THE 12Z GFDL SHOWS THE PRIMARY FEATURES AT 200 MB LOCATED A LITTLE FARTHER TO THE EAST...WITH THE ANTICYCLONE CENTERED OVER THE YUCATAN PENINSULA AND THE DOWNSTREAM TROUGH AXIS A BIT TO THE EAST OF MITCH. THIS IS A LITTLE MORE FAVORABLE ENVIRONMENT FOR INTENSIFICATION THAN FORECAST BY THAT MODEL 6 HOURS AGO...AND COULD BE WHY IT IS SHOWING MORE STRENGTHENING. THE AVN HAS THIS COUPLET CENTERED EVEN FARTHER EAST WITH THE HIGH NEAR MITCH--A VERY FAVORABLE PATTERN. MITCH IS NOW FORECAST TO REACH HURRICANE STRENGTH WITHIN 36 HOURS. WHILE WATCHES AND WARNINGS ARE NOT YET NECESSARY...INTERESTS IN THE WESTERN CARIBBEAN SHOULD CONTINUE MONITORING THE PROGRESS OF MITCH. RAPPAPORT FORECAST POSITIONS AND MAX WINDS INITIAL 22/2100Z 11.5N 77.6W 40 KTS 12HR VT 23/0600Z 12.1N 78.1W 50 KTS 24HR VT 23/1800Z 13.1N 78.3W 60 KTS 36HR VT 24/0600Z 14.2N 78.7W 70 KTS 48HR VT 24/1800Z 15.3N 79.5W 75 KTS 72HR VT 25/1800Z 16.5N 80.5W 75 KTS NNNN