Tropical Storm JULIA

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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
 
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