[Tropical] Tropical Cyclone Discussion

[Nashville EMWIN]

WTNT45 KNHC 160844
TCDAT5
TROPICAL STORM EARL DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 AM EDT MON AUG 16 2004

THE INITIAL POSITION IS HIGHLY UNCERTAIN AND IS BASED...TO A LARGE
DEGREE...ON EXTRAPOLATION AND ASSUMING THAT THE CENTER IS SOMEWHERE
CLOSE TO THE EASTERNMOST BURST OF DEEP CONVECTION. THIS POSITION IS
AT LEAST 30 NMI AHEAD OF THE CONVENTIONAL SATELLITE POSITION
ESTIMATES. THE DVORAK INTENSITY ESTIMATES HAVE DROPPED TO 30 KT.
HOWEVER...GIVEN THE RECENT DEVELOPMENT OF COLD TOPPED CONVECTION
NEAR THE ALLEGED CENTER...THE INTENSITY WILL BE HELD AT 40 KT UNTIL
RECON GETS OUT THERE LATER THIS MORNING TO INVESTIGATE THE CYCLONE.

THE INITIAL MOTION ESTIMATE IS AN UNCERTAIN 285/18. SOME EARLIER
SSMI AND AMSU DATA SUGGEST THAT EARL HAS SLOWED SOME...BUT I AM
RELUCTANT TO BRING DOWN THE FORWARD SPEED TOO MUCH AT THIS TIME.
THE NHC MODEL GUIDANCE IS MORE TIGHTLY CLUSTERED NOW ON A GENERAL
TRACK ACROSS THE YUCATAN PENINSULA IN 84-96 HOURS. HOWEVER...THE
GFDL HAS MADE A MAJOR SHIFT TO THE RIGHT ON THIS FORECAST CYCLE. IT
IS NOW THE RIGHTMOST OF ALL THE MODEL GUIDANCE...EXCEPT FOR THE GFS
10-MEMBER ENSEMBLE MODEL. THE GFS ENSEMBLE MODEL BRINGS EARL TO
NEAR THE YUCATAN CHANNEL IN 120 HOURS. THE SUBTROPICAL RIDGE TO THE
NORTH IS EXPECTED TO REMAIN INTACT THROUGH AT LEAST 72 HOURS...
AFTER WHICH ALL OF THE MODELS AGREE ON BRINGING A SHORTWAVE INTO
THE SOUTHERN PLAINS AND NORTHERN MEXICO...WHICH HELPS TO ERODE THE
RIDGE OVER THE WESTERN GULF OF MEXICO. ONLY THE UKMET AND CANADIAN
MODELS MAINTAIN A STRONG RIDGE ACROSS THE GULF. THE REST OF THE
MODELS HAVE ONLY 5-10 KT OF WIND AT 500 MB IN THE WESTERN GULF IN
4-5 DAYS...WHICH COULD ALLOW FOR EARL TO SLOW AND MOVE MORE
POLEWARD. THE OFFICIAL TRACK IS TO THE RIGHT OF THE PREVIOUS TRACK
AND IS CLOSE TO THE SPEED OF THE NHC MODEL CONSENSUS.

ALL OF THE GLOBAL AND REGIONAL MODELS AGREE ON KEEPING THE
UPPER-LEVEL WINDS UNDER 15 KT AND GENERALLY OUT OF THE EAST ACROSS
THE ENTIRE CARIBBEAN SEA AHEAD OF EARL. THEREFORE...AT LEAST STEADY
INTENSIFICATION IS CALLED FOR. THE INTENSITY FORECAST IS CLOSE TO
THE SHIPS MODEL...AND ACCOUNTS FOR LAND INTERACTION WITH THE
YUCATAN PENINSULA BY 96 HOURS...BUT IS NOT NEARLY AS STRONG AS THE
GFDL MODEL WHICH BRINGS EARL UP TO 91 KT IN ABOUT 72 HOURS.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      16/0900Z 13.2N  67.2W    40 KT
 12HR VT     16/1800Z 14.1N  70.4W    45 KT
 24HR VT     17/0600Z 15.0N  74.6W    50 KT
 36HR VT     17/1800Z 15.7N  78.1W    55 KT
 48HR VT     18/0600Z 16.3N  81.2W    65 KT
 72HR VT     19/0600Z 18.0N  86.0W    75 KT
 96HR VT     20/0600Z 20.5N  90.5W    60 KT...INLAND
120HR VT     21/0600Z 22.5N  94.5W    70 KT...OVER WATER


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