[Tropical] Tropical Cyclone Discussion

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WTNT45 KNHC 301720
TCDAT5
TROPICAL STORM ZETA SPECIAL DISCUSSION NUMBER   1
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
NOON EST FRI DEC 30 2005

AN ELONGATED AREA OF LOW PRESSURE...WHICH HAD ITS ORIGINS IN AN OLD
FRONTAL TROUGH...BEGAN DEVELOPING ORGANIZED CONVECTION OVERNIGHT.
WITH WELL-FORMED CONVECTIVE BANDS NEAR THE CENTER...WEAK
ANTICYCLONIC OUTFLOW ALOFT...AND TROPICAL DVORAK CLASSIFICATIONS...
ADVISORIES ARE INITIATED ON THE 27TH TROPICAL STORM OF 2005.  THE
INTIAL INTENSITY OF 45 KT IS A COMPROMISE BETWEEN THE RULE-
CONSTRAINED T2.5 CLASSIFICATIONS AND THE T3.5 DATA T NUMBERS.
WITHIN 24 HOURS...WESTERLY SHEAR IS EXPECTED TO INCREASE SHARPLY
OVER THE CYCLONE...SO ZETA PROBABLY HAS A SHORT LIFE AHEAD OF IT.

THE INITIAL MOTION IS 305/7...AS ZETA IS MOVING AROUND A MID-LEVEL
LOW TO ITS SOUTHWEST.  THE FORWARD SPEED IS EXPECTED TO SLOW AS THE
WESTERLIES BEGIN TO IMPINGE ON THE CYCLONE WITHIN 12-24 HOURS.
AFTER THAT...IF THE SYSTEM WEAKENS IN RESPONSE TO THE SHEAR...IT
SHOULD TURN WESTWARD WITH THE LOW-LEVEL FLOW.  THE OFFICIAL
FORECAST IS A BLEND OF THE MEDIUM AND SHALLOW BAM MODELS...AND IS
SOMEWHAT SLOWER TO THE WEST THAN THE GFS GUIDANCE.

FORECASTER FRANKLIN


FORECAST POSITIONS AND MAX WINDS

INITIAL      30/1700Z 25.0N  36.9W    45 KT
 12HR VT     31/0000Z 25.5N  37.6W    45 KT
 24HR VT     31/1200Z 26.0N  38.5W    35 KT
 36HR VT     01/0000Z 26.0N  40.0W    25 KT...DISSIPATING
 48HR VT     01/1200Z 26.0N  42.0W    25 KT...REMNANT LOW
 72HR VT     02/1200Z...DISSIPATED


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