[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 212101
TCDAT3
TROPICAL STORM LISA DISCUSSION NUMBER  10
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT TUE SEP 21 2004

LISA REMAINS A VERY COMPACT TROPICAL CYCLONE AND...AS SUCH...IS
SUBJECT TO RAPID FLUCTUATIONS IN INTENSITY. THIS MAY HAVE BEEN THE
CASE EARLIER TODAY AS AN SSMI OVERPASS INDCIATED THE MID-LEVEL
CIRCULATION/EYE FEATURE BECAME DISPLACED A LITTLE TO THE SOUTHWEST
OF THE LOW-LEVEL CENTER. THIS HAS RESULTED IN SIGNIFICANT
DIFFERENCES IN THE SATELLITE POSITION ESTIMATES. THE INITIAL
POSITION IS BETWEEN THE TWO CIRCULATION CENTERS. HOWEVER...DURING
THE PAST FEW HOURS A BURST OF DEEP CONVECTION...TOPS COLDER THAN
-80C...HAS DEVELOPED INTO A CDO-LIKE FEATURE OVER THE OLDER
LOW-LEVEL CENTER LOCATED FARTHER TO THE EAST. THE INTENSITY REMAINS
UNCHANGED AT 60 KT...WHICH IS ONLY SLIGHTLY HIGHER THAN THE DVORAK
INTENSITY ESTIMATE OF T3.5...OR 55 KT...FROM TAFB.

THE INITIAL MOTION ESTIMATE IS NOW 285/07.  ONCE AGAIN...THERE
REMAINS NO SIGNIFICANT CHANGE TO THE PREVIOUS FORECAST TRACK OR
REASONING. MOST OF THE GLOBAL MODELS EITHER LOSE LISA WITHIN 24
HOURS...OR QUICKLY TURN THE CYCLONE NORTHWEST AND THEN NORTHWARD
LIKE THE NOGAPS AND UKMET MODELS ARE INDICATING. HOWEVER...THOSE
TWO MODELS HAVE HAD A PERSISTENT RIGHT-OF-TRACK BIAS THE PAST 24
HOURS SINCE THEY HAVE NOT HANDLED THE RIDGE BETWEEN KARL AND LISA
VERY WELL. WHILE THE AFOREMENTIONED RIDGE IS NARROW...IT IS STRONG
TO KEEP VERY SMALL LISA MOVING WEST TO WEST-NORTHWESTWARD. IN
ADDITION...A LARGE TROPICAL DISTURBANCE LOCATED A FEW HUNDRED MILES
SOUTHEAST OF LISA IS EXPECTED TO INDUCE SOME SOUTHWARD COMPONENT OF
MOTION AS THAT DISTURBANCE CONTINUES TO LIKELY GROW AND INTENSITY.
THE GFDL HAS BEEN THE ONLY MODEL TO CONSISTENTLY PICK UP ON THIS
INTERACTION AND IT FORCES LISA SHARPLY SOUTHWARD IN 48 HOURS. WHILE
THE SPECIFICS OF THE GFDL TRACK ARE LIKELY OVERDONE...ITS
CONSISTENT TREND IN MOVING LISA SOUTHWARD CAN NOT BE IGNORED. A
SLIGHT SOUTHWARD BEND IN THE TRACK IS INDICATED BY THE OFFICIAL
FORECAST. THIS IS ALSO CONSISTENT WITH ALL THE GLOBAL MODELS
FORECASTING A RIDGE TO BUILD OVER AND TO THE EAST OF THE LEEWARD
ISLANDS BY 96-120 HOURS.

DUE TO THE VERY SMALL SIZE OF LISA...NO SIGNIFICANT INTENSITY
INCREASES ARE FORECAST...EVEN THOUGH RAPID FLUCTUATIONS ARE
CERTAINLY POSSIBLE.

FORECASTER STEWART

FORECAST POSITIONS AND MAX WINDS

INITIAL      21/2100Z 14.4N  40.3W    60 KT
 12HR VT     22/0600Z 14.8N  41.5W    60 KT
 24HR VT     22/1800Z 15.2N  43.0W    60 KT
 36HR VT     23/0600Z 15.2N  44.5W    65 KT
 48HR VT     23/1800Z 15.0N  45.7W    65 KT
 72HR VT     24/1800Z 15.0N  47.0W    70 KT
 96HR VT     25/1800Z 15.5N  48.5W    75 KT
120HR VT     26/1800Z 17.5N  50.5W    75 KT


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