Hurricane JULIA

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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
 
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