000
WTNT42 KNHC 142036
TCDAT2
HURRICANE JULIA DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL122010
500 PM AST TUE SEP 14 2010
 
THE CLOUD PATTERN ASSOCIATED WITH JULIA HAS BECOME SOMEWHAT
ASYMMETRIC DURING THE PAST SEVERAL HOURS...WITH A LARGE MASS OF
DEEP CONVECTION HAVING FORMED SOUTHWEST OF THE CENTER. THE
EYE THAT WAS VISIBLE EARLIER IS ALSO NO LONGER AS EVIDENT. THE
OUTFLOW HAS BECOME A BIT RESTRICTED TO THE WEST...INDICATIVE OF
SOME UPPER-LEVEL WESTERLY FLOW ALREADY IMPINGING UPON THE CYCLONE.
DVORAK CI NUMBERS AT 1800 UTC ARE UNCHANGED FROM 1200 UTC...WHILE
THE 3-HOURLY AVERAGED ADT VALUE IS AT 4.6. THE INITIAL INTENSITY IS
HELD AT 75 KT FOR THIS ADVISORY IN AGREEMENT WITH SATELLITE
ESTIMATES.
 
RECENT FIXES INDICATE THAT JULIA HAS SLOWED A BIT FURTHER...AND THE
INITIAL MOTION ESTIMATE IS 295/08.  WITH THE EXCEPTION OF THE
UKMET...THE TRACK MODEL GUIDANCE IS IN BETTER AGREEMENT THIS CYCLE
CONCERNING THE SHORT-TERM TRACK FORECAST.  JULIA IS EXPECTED TO
MOVE ON A GENERAL NORTHWESTERLY COURSE DURING THE NEXT 24 HOURS AS
IT INTERACTS WITH A MID- TO UPPER-LEVEL TROUGH EXTENDING
SOUTHWESTWARD FROM A CYCLONE OVER THE NORTHEAST ATLANTIC.
FROM 24-72 HOURS...GLOBAL MODELS INDICATE THAT JULIA SHOULD TURN
WEST-NORTHWESTWARD WITH SOME INCREASE IN FORWARD SPEED UNDER THE
INFLUENCE OF A BUILDING SUBTROPICAL RIDGE TO THE NORTH.  BEYOND THAT
TIME...JULIA IS FORECAST TO TURN NORTH-NORTHWESTWARD AND THEN
NORTHWARD ONCE IT REACHES THE WESTERN PERIPHERY OF THE SUBTROPICAL
RIDGE. THE OFFICIAL NHC TRACK FORECAST IS NUDGED TO THE RIGHT AGAIN
USING A MODEL CONSENSUS THAT EXCLUDES THE UKMET BUT HAS SHIFTED A
BIT TO THE LEFT LATE IN THE PERIOD...FOLLOWING THE TREND IN THE
GUIDANCE.
 
WATER VAPOR IMAGERY SUGGESTS THAT WESTERLY SHEAR ASSOCIATED WITH A
MID- TO UPPER-LEVEL TROUGH...PARTIALLY RELATED TO THE OUTFLOW OF
HURRICANE IGOR...MAY ALREADY BE NEGATIVELY IMPACTING JULIA.  SHIPS
MODEL OUTPUT INDICATES SOME INCREASE IN THIS SHEAR DURING THE NEXT
COUPLE OF DAYS AT THE SAME TIME JULIA TRAVERSES MARGINAL SEA
SURFACE TEMPERATURES.  ALTHOUGH THE CYCLONE IS FORECAST TO MOVE
OVER WARMER WATERS AGAIN LATER IN THE FORECAST PERIOD...GLOBAL
MODELS SHOW A STRONG SURGE OF NORTHERLY FLOW ASSOCIATED WITH THE
OUTFLOW FROM HURRICANE IGOR ADVERSELY AFFECTING JULIA.  ALTHOUGH
FEW CHANGES WERE MADE TO THE OFFICIAL NHC INTENSITY FORECAST...
JULIA COULD BE WEAKER THAN FORECAST IF THE PREDICTED SHEAR
MATERIALIZES.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      14/2100Z 16.7N  30.2W    75 KT
 12HR VT     15/0600Z 17.8N  31.4W    80 KT
 24HR VT     15/1800Z 19.5N  33.1W    80 KT
 36HR VT     16/0600Z 21.3N  35.7W    75 KT
 48HR VT     16/1800Z 22.8N  39.1W    70 KT
 72HR VT     17/1800Z 25.0N  46.0W    70 KT
 96HR VT     18/1800Z 29.1N  50.5W    60 KT
120HR VT     19/1800Z 33.0N  51.0W    50 KT
 
$$
FORECASTER KIMBERLAIN