[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT42 KNHC 200842
TCDAT2
TROPICAL STORM JULIA DISCUSSION NUMBER  33
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL122010
500 AM AST MON SEP 20 2010

JULIA AGAIN PROVIDED A SURPRISE FOR A SECOND NIGHT IN A ROW WITH
STRONGER SURFACE WINDS MEASURED FROM THE ASCAT SCATTEROMETER THAN
WHAT WAS SUGGESTED FROM CONVENTIONAL SATELLITE IMAGERY USING THE
DVORAK TECHNIQUE.  THE 0046Z ASCAT PASS SHOWED MAXIMUM WINDS OF AT
LEAST 45 KT...DESPITE A FAIRLY DISHEVELED APPEARANCE TO THE DEEP
CONVECTION.  THE 0600Z TAFB AND SAB DATA-T DVORAK NUMBERS REMAIN AT
A 2.0...OR 30 KT.  THE INITIAL INTENSITY IS SET AT 40 KT...ASSUMING
SOME WEAKENING SINCE THE ASCAT PASS.

THE CENTER CONTINUES TO BE DISPLACED WEST OF THE LIMITED DEEP
CONVECTION DUE TO STRONG WESTERLY VERTICAL SHEAR INDUCED BY
EXTREMELY LARGE HURRICANE IGOR. THE INITIAL MOTION OF JULIA IS
ESTIMATED TO BE 65 DEGREES AT 8 KT...AND THE CYCLONE IS BEING
ADVECTED AROUND THE NORTHERN PERIPHERY OF THE DEEP LAYER
SUBTROPICAL RIDGE. THE CYCLONE SHOULD ACCELERATE SOME TOWARD THE
NORTH-NORTHEAST IN THE NEXT DAY OR SO. AROUND 36 HOURS...JULIA
SHOULD BECOME ABSORBED INTO THE CIRCULATION OF IGOR AS SHOWN BY
NEARLY ALL OF THE MODELS. HOWEVER...THE ECMWF MODEL KEEPS THE
CYCLONE FAR ENOUGH SOUTH OF IGOR TO PREVENT THE ABSORPTION.
INSTEAD...THE ECMWF MAINTAINS JULIA AS A SEPARATE CYCLONE FOR
SEVERAL MORE DAYS...THOUGH BECOMING EXTRATROPICAL ABOUT TWO DAYS
FROM NOW. THIS TRACK FORECAST GOES WITH THE CONSENSUS...MINUS THE
ECMWF...AND IS SLIGHTLY TO THE LEFT OF AND FASTER THAN THE PREVIOUS
ADVISORY.

AS JULIA SHOULD GRADUALLY ENCOUNTER SUB-26C WATER TEMPERATURES ALONG
WITH QUITE HOSTILE VERTICAL SHEAR...GRADUAL WEAKENING IS EXPECTED
FOR THE NEXT TWO DAYS UNTIL DISSIPATION.  THE INTENSITY FORECAST IS
BASED UPON THE MODEL CONSENSUS AND IS SLIGHTLY HIGHER THAN THE
PREVIOUS ADVISORY BECAUSE OF THE STRONGER INITIAL CYCLONE.

THE AFOREMENTIONED ASCAT PASS ALLOWED FOR AN ENLARGEMENT OF THE
TROPICAL STORM WIND RADII.

FORECAST POSITIONS AND MAX WINDS

INITIAL      20/0900Z 35.5N  47.9W    40 KT
 12HR VT     20/1800Z 36.1N  46.8W    35 KT
 24HR VT     21/0600Z 37.6N  45.3W    30 KT...POST-TROP/REMNT LOW
 36HR VT     21/1800Z 39.6N  43.5W    25 KT...POST-TROP/REMNT LOW
 48HR VT     22/0600Z...DISSIPATED

$$
FORECASTER LANDSEA/BRENNAN


This weather bulletin was brought to you by:
www.nashvilleweather.net