ZCZC MIATCDAT5 ALL TTAA00 KNHC DDHHMM TROPICAL STORM JUAN DISCUSSION NUMBER 4 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL 5 AM EDT FRI SEP 26 2003 AFTER COMING OUT OF THE GOES-12 SATELLITE ECLIPSE PERIOD...NEW IMAGERY INDICATES THAT JUAN HAS BECOME BETTER ORGANIZED AND HAS ALSO STARTED MOVING NORTHWARD AGAIN. AN EYE-LIKE FEATURE WAS APPARENT IN THE MID-CLOUDS OF THE PRE-ECLIPSE IMAGERY...BUT NO DEEP CONVECTION WAS WITHIN 100 NMI OF THE CENTER. HOWEVER...THE EYE FEATURE IS NOW OBSCURED BY DEEP CONVECTION...TOPS COLDER THAN -70C...THAT HAVE SURROUNDED MORE THAN 50 PERCENT OF THE INNER CORE CIRCULATION. ALTHOUGH SATELLITE INTENSITY ESTIMATES ARE A CONSENSUS T2.5...OR 35 KT...I HAVE OPTED TO INCREASE THE INTENSITY SLIGHTLY BASED ON THIS NEW INNER-CORE CONVECTIVE BANDING AND RECENT AMSU INTENSITY ESTIMATES OF 990-992 MB. THE INITIAL MOTION ESTIMATE IS 350/08. THERE IS NO SIGNIFICANT CHANGE TO THE PREVIOUS TRACK OR INTENSITY FORECAST. THE NHC MODEL GUIDANCE SHOWS GOOD CONVERGENCE ABOUT THE PREVIOUS FORECAST TRACK AND IS ALSO IN GOOD AGREEMENT ON TAKING JUAN NORTH TO NORTH-NORTHWESTWARD AND GRADUALLY ACCELERATE THE CYCLONE THROUGH 72 HOURS AS A SERIES OF NEGATIVELY TILTED SHORTWAVE TROUGHS UNDERCUT THE SYSTEM FROM THE WEST AND SOUTH. BY 96 HOURS OR SO...JUAN IS EXPECTED TO BE OVER THE CANADIAN MARITIMES REGION AND STARTING TO BECOME EXTRATROPICAL AS THE CYCLONE BEGINS TO INTERACT WITH AND EVENTUALLY BECOME ABSORBED BY A LARGER EXTRATROPICAL LOW PRESSURE SYSTEM. THERE IS A LARGE SPREAD IN THE MODEL GUIDANCE BY 96 HOURS WITH NOGAPS TAKING JUAN THE FARTHEST TO THE NORTHEAST OVER NORTHERN NEWFOUNDLAND...WHILE THE REST OF THE NHC MODEL GUIDANCE TAKES THE CYCLONE OVER THE ENTIRE LENGTH OF NOVA SCOTIA. THE OFFICIAL FORECAST TRACK IS ONLY SLIGHTLY TO THE LEFT OF THE PREVIOUS TRACK...AND IS CLOSE TO THE GFS AND GFDL MODELS. IT WOULD NOT TAKE MUCH CONVECTION TO WRAP ALL THE AROUND THE INNER-CORE OF JUAN AND PRODUCE AN EYE. WITH THIS IN MIND...THE INTENSITY WAS INCREASED SLIGHTLY...BUT NIT AS HIGH AS THE SHIPS AND GFDL INTENSITY MODELS WHICH BRING JUAN UP TO 75 KT AND 83 KT... RESPECTIVELY...IN 36 HOURS. UPPER-LEVEL SHEAR WILL GRADUALLY INCREASE TO MORE THAN 20 KT BY 24 HOURS...AND THIS IS THE PRIMARY REASON FOR REMAINING BELOW THE MODEL GUIDANCE AT THIS TIME. FORECASTER STEWART FORECAST POSITIONS AND MAX WINDS INITIAL 26/0900Z 31.5N 61.9W 55 KT 12HR VT 26/1800Z 32.5N 62.2W 60 KT 24HR VT 27/0600Z 34.3N 62.6W 65 KT 36HR VT 27/1800Z 36.3N 63.3W 65 KT 48HR VT 28/0600Z 38.4N 63.8W 60 KT 72HR VT 29/0600Z 46.0N 63.0W 55 KT...EXTRATROPICAL INLAND 96HR VT 30/0600Z 50.5N 60.5W 50 KT...EXTRATROPICAL INLAND 120HR VT 01/0600Z...ABSORBED BY LARGER EXTRATROPICAL LOW NNNN
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Page last modified: Monday, 07-Feb-2005 16:49:59 UTC