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Tropical Storm JULIA (Text)

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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
 
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