000 WTNT42 KNHC 170847 TCDAT2 HURRICANE JULIA DISCUSSION NUMBER 21 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010 500 AM AST FRI SEP 17 2010 UP UNTIL THE LAST HOUR...JULIA HAD EXHIBITED A SMALL BUT WELL- DEFINED EYE WITH A SOLID EYEWALL. SUBJECTIVE DVORAK CLASSIFICATIONS ARE 77 KT...WITH ADT VALUES USING AN EYE PATTERN SUPPORTING ANYWHERE FROM 75-85 KT. GIVEN THAT THE EYE HAS BECOME OBSCURED... THE INITIAL WINDS ARE ONLY INCREASED TO THE LOWER END OF THOSE ESTIMATES...75 KT. THE HURRICANE IS IN A SMALL LOW SHEAR ENVIRONMENT TO THE NORTH OF AN UPPER LOW. HOWEVER...JULIA IS ABOUT TO ENCOUNTER AN UPPER-LEVEL JET...PART OF THE OUTFLOW FROM IGOR...WHICH SHOULD INDUCE SIGNIFICANT SHEAR AND A FAIR AMOUNT OF WEAKENING. JULIA SHOULD MOVE AWAY FROM THE MAIN JET CORE IN TWO TO THREE DAYS... CAUSING THE SHEAR TO MODERATE SOMEWHAT...BUT SLOW WEAKENING IS STILL EXPECTED. BY THE END OF THE FORECAST PERIOD...VERY STRONG SHEAR IS FORECAST TO OCCUR...WHICH SHOULD CAUSE RAPID DISSIPATION. THE NEW NHC INTENSITY FORECAST IS CLOSE TO THE PREVIOUS ONE AND THE SHIPS MODEL...BUT BELOW MOST OF THE REST OF THE GUIDANCE. JULIA CONTINUES TO MOVE 290/21. THE HURRICANE APPEARS TO BE LEAVING THE INFLUENCE OF A MID- TO UPPER-LEVEL LOW TO THE SOUTHEAST ...AND BECOMING MOSTLY STEERED BY A RIDGE OVER THE EASTERN ATLANTIC OCEAN. JULIA SHOULD GRADUALLY GAIN LATITUDE AND EVENTUALLY TURN TO THE NORTH AND NORTHEAST AROUND THE WESTERN PORTION OF THE RIDGE. THE TRACK GUIDANCE CONTINUES TO SHIFT WESTWARD...PERHAPS DUE TO THE FAST WEST-NORTHWESTWARD MOTION AND UNFORESEEN IMPACTS OF THE MID- TO UPPER-LEVEL LOW. THE NHC FORECAST IS SHIFTED WESTWARD AGAIN ...AND LIES BETWEEN THE GFS ENSEMBLE AND THE MULTI-MODEL CONSENSUS. FORECAST POSITIONS AND MAX WINDS INITIAL 17/0900Z 23.8N 45.1W 75 KT 12HR VT 17/1800Z 25.0N 47.6W 65 KT 24HR VT 18/0600Z 27.2N 50.2W 55 KT 36HR VT 18/1800Z 29.7N 51.9W 50 KT 48HR VT 19/0600Z 32.4N 52.4W 45 KT 72HR VT 20/0600Z 36.0N 49.5W 40 KT 96HR VT 21/0600Z 40.0N 44.5W 35 KT 120HR VT 22/0600Z...DISSIPATED $$ FORECASTER BLAKE