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| #376005 (Received by flhurricane at: 10:46 AM 14.Sep.2010) TCDAT2 HURRICANE JULIA DISCUSSION NUMBER 9 NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL122010 1100 AM AST TUE SEP 14 2010 SATELLITE IMAGES INDICATE THAT JULIA IS STILL STRENGTHENING. A 0920 UTC SSM/IS OVERPASS SHOWED A WELL-DEFINED EYEWALL SURROUNDED BY TWO PROMINENT BANDS...WHILE CONVENTIONAL IMAGERY SHOWS THE APPEARANCE OF A WELL-DEVELOPED CENTRAL DENSE OVERCAST AND A BANDING-TYPE EYE. SUBJECTIVE DVORAK T-NUMBERS AT 1200 UTC ARE 4.0 AND 5.0 FROM TAFB AND SAB...RESPECTIVELY. THE INITIAL INTENSITY IS RAISED TO 75 KT...BASED UPON A BLEND OF THESE ESTIMATES. WHILE SOME ADDITIONAL INTENSIFICATION IS POSSIBLE DURING THE NEXT 12 TO 24 HOURS...WATER VAPOR IMAGERY SHOWS A MID- TO UPPER-LEVEL TROUGH...PARTIALLY RELATED TO THE OUTFLOW OF HURRICANE IGOR... LOCATED A FEW HUNDRED MILES NORTHWEST OF JULIA. GLOBAL MODELS SUGGEST THAT THIS FEATURE SHOULD BEGIN TO IMPART WESTERLY SHEAR OVER THE CYCLONE AFTER ABOUT 24 HOURS...AT ABOUT THE TIME JULIA BEGINS TO PASS OVER MARGINAL SEA SURFACE TEMPERATURES. WATERS SHOULD BEGIN TO WARM AGAIN ALONG THE FORECAST TRACK IN A FEW DAYS...BUT MODEL GUIDANCE SHOWS A STRONG SURGE OF NORTHERLY FLOW ASSOCIATED THE OUTFLOW OF IGOR THAT COULD NEGATIVELY IMPACT JULIA AFTER 72 HOURS. IN FACT...SHIPS MODEL OUTPUT INDICATES THE POTENTIAL FOR 30-40 KT OF NORTHERLY SHEAR. ALTHOUGH NO SIGNIFICANT CHANGES WERE MADE TO THE OFFICIAL INTENSITY FORECAST...JULIA COULD BE WEAKER THAN FORECAST IF THE PREDICTED SHEAR MATERIALIZES. THE INITIAL MOTION ESTIMATE IS 295/09...INDICATING THAT JULIA HAS RECENTLY SLOWED A BIT. THERE IS AN UNUSUAL AMOUNT OF SPREAD IN THE SHORT-TERM TRACK FORECAST. THE GFS/HWRF/GFDL SHOW JULIA TURNING TOWARD THE NORTHWEST DURING THE NEXT DAY OR SO AS IT INTERACTS WITH AN EXTENSION OF A MID- TO UPPER-LEVEL CYCLONE LOCATED OVER THE NORTHEAST ATLANTIC. THE UKMET/ECMWF FAVOR A WEST-NORTHWEST COURSE AS A RESULT OF MORE SUBTROPICAL RIDGING. FROM ABOUT 36-72 HR... THERE IS BETTER AGREEMENT IN THE MODEL GUIDANCE OF SUBTROPICAL RIDGING BUILDING NORTH OF JULIA AND HENCE A MORE WEST-NORTHWESTERLY COURSE WITH AN INCREASE IN FORWARD SPEED. AFTER 72 HR...GLOBAL MODELS SHOW JULIA TURNING NORTH-NORTHWESTWARD AS IT APPROACHES THE WESTERN END OF THE SUBTROPICAL RIDGE AND THE LARGE HURRICANE IGOR OVER THE CENTRAL ATLANTIC. THE OFFICIAL NHC FORECAST TRACK IS NUDGED A BIT TO THE RIGHT...LYING NEAR A CONSENSUS THAT EXCLUDES THE UKMET. FORECAST POSITIONS AND MAX WINDS INITIAL 14/1500Z 16.2N 29.5W 75 KT 12HR VT 15/0000Z 17.2N 30.8W 85 KT 24HR VT 15/1200Z 18.7N 32.4W 80 KT 36HR VT 16/0000Z 20.3N 34.5W 75 KT 48HR VT 16/1200Z 22.2N 37.7W 70 KT 72HR VT 17/1200Z 24.7N 44.3W 70 KT 96HR VT 18/1200Z 28.0N 49.0W 60 KT 120HR VT 19/1200Z 32.5N 50.5W 50 KT $$ FORECASTER KIMBERLAIN |
