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Hurricane JULIA


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HURRICANE JULIA DISCUSSION NUMBER  18
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL122010
1100 AM AST THU SEP 16 2010
 
SATELLITE IMAGERY CONTINUES TO INDICATE WARMING OF THE CLOUD TOPS IN
THE RATHER RAGGED LOOKING CENTRAL DENSE OVERCAST. A 1001Z AMSU
MICROWAVE OVERPASS INDICATED A 25-30 NMI DIAMETER EYE THAT WAS OPEN
IN THE SOUTHEAST QUADRANT. WATER VAPOR IMAGERY ALSO SHOWS A LARGE
SLUG OF DRY AIR BEING ENTRAINED INTO THE EASTERN SEMICIRCLE...WHICH
LIKELY EXPLAINS THE EROSION OF THE EASTERN EYEWALL NOTED IN THE
AMSU IMAGERY. DESPITE THE AFOREMENTIONED NEGATIVE FACTORS...JULIA
HAS MAINTAINED GOOD OUTFLOW TO THE WEST AND NORTH OF THE CYCLONE.

THE INITIAL MOTION ESTIMATE HAS INCREASED SHARPLY TO 300/22. JULIA
IS EXPECTED TO MOVE TO THE WEST-NORTHWEST AND THEN NORTHWEST
FOR THE NEXT 36-48 HOURS AS THE HURRICANE ROUNDS THE SOUTHERN
PERIPHERY OF A LARGE SUBTROPICAL RIDGE SITUATED TO ITS NORTH AND
NORTHEAST. AFTER THAT...SIGNIFICANT VERTICAL WIND SHEAR MAY WEAKEN
THE CYCLONE AND CAUSE IT TO BECOME MORE SHALLOW...AND THEN BE
STEERED MORE NORTHWARD SIMILAR TO THE ECMWF AND GFDL MODELS...BUT
NOT AS FAR NORTH AND WEST AS THE SHALLOW BAM MODEL. THE OFFICIAL
TRACK FORECAST HAS BEEN NUDGED TO THE LEFT OF THE PREVIOUS ADVISORY
THROUGH 72 HOURS...AND IS SIMILAR TO THE MULTI-MODEL CONSENSUS.

DRY AIR AND COOLER SSTS SHOULD CONTINUE THE RECENT WEAKENING
TREND...ESPECIALLY AFTER 24 HOURS. BY 36-48 HOURS...ALL OF THE
GLOBAL MODELS INDICATE THAT JULIA WILL BE MOVING INTO A REGION OF
STRONG UPPER-LEVEL SHEAR CAUSED BY THE PRONOUNCED NORTHERLY OUTFLOW
EMANATING FROM THE MAJOR HURRICANE IGOR LOCATED TO ITS WEST. WITH
JULIA MOVING INTO 50-70 KT OF 200 MB WINDS...IT WILL BE HARD FOR
JULIA TO SURVIVE AS A TROPICAL CYCLONE AS INDICATED BY THE GLOBAL
MODELS AND GFDL/HWRF MODELS. THE OFFICIAL INTENSITY FORECAST SHOWS
A FASTER WEAKENING TREND THAN THE PREVIOUS ADVISORY...BUT NOT AS
FAST AS THE SHIPS MODEL...WHICH DISSIPATES JULIA BY 120 HOURS.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      16/1500Z 22.4N  38.6W    85 KT
 12HR VT     17/0000Z 23.7N  41.2W    75 KT
 24HR VT     17/1200Z 25.5N  44.6W    65 KT
 36HR VT     18/0000Z 27.3N  47.3W    55 KT
 48HR VT     18/1200Z 29.3N  49.1W    45 KT
 72HR VT     19/1200Z 33.2N  49.6W    35 KT
 96HR VT     20/1200Z 35.8N  46.3W    35 KT
120HR VT     21/1200Z 38.0N  42.0W    35 KT
 
$$
FORECASTER STEWART
 
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