000 WTNT42 KNHC 140255 TCDAT2 TROPICAL STORM JULIA DISCUSSION NUMBER 7 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010 1100 PM AST MON SEP 13 2010 A RECENT AMSU MICROWAVE PASS SHOWS IMPROVED BANDING OVER THE WESTERN SEMICIRCLE AND THAT THE DEEP CONVECTION IS NOW WRAPPING AROUND THE SOUTHERN PORTION OF THE CIRCULATION. DESPITE THE IMPROVED PRESENTATION...DVORAK ESTIMATES FROM SAB AND TAFB REMAIN 45 KT...SO THE INITIAL INTENSITY IS MAINTAINED FOR NOW. THIS IS ALSO SUPPORTED BY A 2324 UTC ASCAT PASS THAT SHOWED SEVERAL 35-40 KT WIND VECTORS OVER THE NORTHEAST QUADRANT. THE INITIAL MOTION ESTIMATE IS 295/11 KT. JULIA IS FORECAST TO TURN NORTHWESTWARD IN ABOUT 12-24 HOURS AS IT MOVES BETWEEN THE WESTERN PERIPHERY OF A MID-LEVEL RIDGE AND AN AMPLIFYING MID- TO UPPER-LEVEL TROUGH OVER THE EASTERN ATLANTIC. THEREAFTER JULIA IS EXPECTED TO MOVE IN A DIRECTION BETWEEN WEST-NORTHWEST AND NORTHWEST AS A MID-LEVEL RIDGE STRENGTHS TO THE NORTH AND NORTHEAST OF THE CYCLONE. THE TRACK GUIDANCE IS IN GENERAL AGREEMENT ON THIS SCENARIO...BUT THERE IS SOME SIGNIFICANT SPREAD ON WHEN THE NORTHWESTWARD TURN WILL OCCUR. THE GFS/GFDL ARE ALONG THE EASTERN EDGE OF THE GUIDANCE...WHILE THE UKMET AND NOGAPS ARE ALONG THE WESTERN SIDE. THE OFFICIAL FORECAST LIES BETWEEN THE TVCN CONSENSUS AND THE GFS/GFDL SOLUTIONS...AND IS CLOSE TO THE PREVIOUS NHC ADVISORY. JULIA WILL BE OVER WARM WATER AND IN A LOW SHEAR ENVIRONMENT DURING THE NEXT DAY OR SO. THE SHIPS/LGEM GUIDANCE BRING THE CYCLONE TO HURRICANE STRENGTH WITHIN THAT TIME AND SO DOES THE OFFICIAL FORECAST. THEREAFTER...INCREASING SOUTHWESTERLY SHEAR AND SLIGHTLY COOLER SEA SURFACE TEMPERATURES ARE LIKELY TO HALT ANY ADDITIONAL INTENSIFICATION. AFTER 72 HOURS...THE GLOBAL MODELS SUGGEST THAT STRONG UPPER-LEVEL NORTHEASTERLY WINDS ASSOCIATED WITH THE OUTFLOW FROM IGOR WILL BEGIN TO IMPINGE UPON JULIA. AS A RESULT... WEAKENING IS ANTICIPATED AT DAYS 4 AND 5. THE WIND RADII WERE ADJUSTED OUTWARD BASED ON THE ASCAT DATA. FORECAST POSITIONS AND MAX WINDS INITIAL 14/0300Z 15.6N 28.0W 45 KT 12HR VT 14/1200Z 16.3N 29.4W 55 KT 24HR VT 15/0000Z 17.5N 31.1W 65 KT 36HR VT 15/1200Z 19.1N 32.7W 70 KT 48HR VT 16/0000Z 21.1N 35.1W 70 KT 72HR VT 17/0000Z 24.3N 40.9W 65 KT 96HR VT 18/0000Z 27.5N 46.5W 55 KT 120HR VT 19/0000Z 31.5N 50.0W 50 KT $$ FORECASTER BROWN