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| #375787 (Received by flhurricane at: 10:55 AM 13.Sep.2010) TCDAT2 TROPICAL STORM JULIA DISCUSSION NUMBER 5 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010 1100 AM AST MON SEP 13 2010 METEOSAT-9 IMAGERY AND A 0938 UTC SSMIS MICROWAVE OVERPASS INDICATE LITTLE CHANGE IN THE CLOUD PATTERN DURING THE PAST 6 HOURS. THE MAJORITY OF THE CONVECTIVE BANDING IS SITUATED OVER THE WESTERN PORTION OF THE CYCLONE...WHERE THE UPPER-LEVEL OUTFLOW IS THE MOST IMPRESSIVE. DVORAK TECHNIQUE INTENSITY ESTIMATES FROM BOTH TAFB AND SAB ARE T2.5...35 KT...AND THIS IS THE INITIAL INTENSITY. THE DYNAMICAL MODELS AND THE SHIPS MODEL SUGGEST THAT THE UPPER-LEVEL WIND PATTERN SHOULD REMAIN CONDUCIVE FOR STRENGTHENING DURING THE NEXT 48 HOURS. BEYOND THAT TIME...JULIA COULD BE IMPACTED BY A SUBSTANTIAL INCREASE IN WESTERLY SHEAR DUE TO AN AMPLIFYING UPPER-LEVEL TROUGH OVER THE EASTERN SUBTROPICAL ATLANTIC...WHICH SHOULD HINDER FURTHER INTENSIFICATION. THE NHC INTENSITY FORECAST REFLECTS THIS SCENARIO BY MAINTAINING JULIA AS A LOW-END HURRICANE THROUGH 96 HOURS. AFTERWARD...THE SHIPS... LGEM...AND THE LARGE-SCALE MODELS ALL SUGGEST THAT THE UPPER-LEVEL OUTFLOW ASSOCIATED WITH HURRICANE IGOR WILL CREATE MODERATE TO STRONG NORTHEASTERLY SHEAR OVER JULIA. THIS INCREASE IN SHEAR AROUND DAY 5 IS REFLECTED IN THE OFFICIAL FORECAST...WHICH SHOWS JULIA WEAKENING INTO A TROPICAL STORM. BASED ON A NUMBER OF MICROWAVE FIXES...THE INITIAL MOTION IS ESTIMATED TO BE WEST-NORTHWESTWARD...295/12...A LITTLE LEFT OF THE PREVIOUS ADVISORY. THE DYNAMICAL MODELS ARE IN GOOD AGREEMENT THROUGH DAY 5 WITH A NORTHWESTWARD TURN IN 36 HOURS IN RESPONSE TO A MID- TO UPPER-LEVEL CUT-OFF LOW LOCATED TO THE NORTHWEST OF JULIA. BEYOND THIS TIME...THE EASTERN EXTENT OF THE SUBTROPICAL RIDGE GRADUALLY BUILDS NORTHEAST OF THE CYCLONE AS THE CUT-OFF LOW WEAKENS AND DISSIPATES. THIS SHOULD ALLOW JULIA TO MAINTAIN A GENERAL NORTHWESTWARD MOTION THROUGH DAY 5. THE OFFICIAL FORECAST FAVORS THE TVCN MULTI-MODEL CONSENSUS AND LIES BETWEEN THE GFS AND ECMWF GLOBAL MODELS. FORECAST POSITIONS AND MAX WINDS INITIAL 13/1500Z 14.9N 26.1W 35 KT 12HR VT 14/0000Z 15.6N 27.6W 45 KT 24HR VT 14/1200Z 16.7N 29.6W 55 KT 36HR VT 15/0000Z 18.1N 31.4W 60 KT 48HR VT 15/1200Z 19.6N 33.2W 65 KT 72HR VT 16/1200Z 22.8N 37.7W 65 KT 96HR VT 17/1200Z 25.5N 43.0W 65 KT 120HR VT 18/1200Z 28.5N 47.5W 60 KT $$ FORECASTER ROBERTS/BRENNAN |
