ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM NARDA DISCUSSION NUMBER 3 NATIONAL WEATHER SERVICE MIAMI FL 8 PM PDT SAT OCT 20 2001 CONVECTION ASSOCIATED WITH NARDA IS CONSOLIDATING THIS EVENING... WITH A CENTRAL DENSE OVERCAST OF TOPS COLDER THAN -80C DEVELOPING OVER THE LOW LEVEL CENTER. SATELLITE INTENSITY ESTIMATES...WHICH INCLUDE DVORAK CONSTRAINTS...ARE 35 KT FROM TAFB...SAB...AND AFWA. THE INITIAL INTENSITY WILL BE INCREASED TO 40 KT BASED ON THE ESTIMATES AND THE INCREASE IN ORGANIZATION SINCE 00Z. THE INITIAL MOTION IS 295/13. SATELLITE IMAGERY INDICATES THAT NARDA IS ON THE SOUTH SIDE OF A DEEP LAYER RIDGE...AND THAT A LARGE MID/UPPER LEVEL TROUGH IS PRESENT TO THE EAST AND NORTHEAST OF THE HAWAIIAN ISLANDS. LARGE-SCALE MODELS INDICATE THAT THE MID-LEVEL PORTION OF THE TROUGH WILL WEAKEN AND ALLOW RIDGING TO BUILD WESTWARD. THIS PATTERN SHOULD MOVE NARDA ALONG A WEST-NORTHWEST TO POSSIBLY WEST TRACK. NHC HURRICANE GUIDANCE IS SOMEWHAT SPREAD... WITH THE GFDL...UKMET AND BAMS FAVORING A WEST-NORTHWEST MOTION AND BAMD...BAMM..AND LBAR FAVORING A SLOWER AND MORE NORTHWEST MOTION. GIVEN THE INITIAL MOTION...THE FORECAST TRACK WILL GO WITH THE GFDL...UKMET...BAMS SOLUTION AND WILL BE AN UPDATE OF THE PREVIOUS FORECAST. NARDA IS SHOWING GOOD ANTICYCLONIC OUTFLOW...ESPECIALLY TO THE WEST WHERE FOR THE MOMENT IT SEEMS TO BE REPELLING ONCOMING UPPER-LEVEL WESTERLIES. BASED ON THIS AND THE INCREASED CENTRAL CONVECTION... THE SHORT-TERM INTENSITY FORECAST WILL BE RAISED A LITTLE. IN THE LONG-TERM...LARGE-SCALE MODELS FORECAST THAT THE WEAKENING OF THE CENTRAL PACIFIC TROUGH SHOULD CREATE INCREASING UPPER-LEVEL WESTERLY FLOW ACROSS THE PATH OF NARDA AFTER 36 HR...WHICH SHOULD PRODUCE STRONG SHEAR. THUS...SIGNIFICANT WEAKENING IS FORECAST AFTER THE 36 HR POINT. IT IS POSSIBLE THAT DUE TO ITS SMALL SIZE THAT NARDA COULD BOTH STRENGTHEN AND WEAKEN FASTER THAN CURRENTLY FORECAST. FORECASTER BEVEN FORECAST POSITIONS AND MAX WINDS INITIAL 21/0300Z 12.5N 128.1W 40 KTS 12HR VT 21/1200Z 13.4N 129.9W 50 KTS 24HR VT 22/0000Z 14.5N 132.0W 55 KTS 36HR VT 22/1200Z 15.5N 134.3W 60 KTS 48HR VT 23/0000Z 16.2N 136.4W 55 KTS 72HR VT 24/0000Z 17.5N 141.0W 40 KTS NNNN