[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 020235
TCDAT5
TROPICAL STORM ZETA DISCUSSION NUMBER  11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
10 PM EST SUN JAN 01 2006

THIS IS LIKE PREVIOUS TROPICAL CYCLONE EPSILON ALL OVER AGAIN. MOST
OF THE CONVENTIONAL GUIDANCE SUGGESTED THAT ZETA SHOULD HAVE BEEN
DISSIPATED BY NOW...WELL IT IS NOT INDEED...AND ZETA IS PRETTY MUCH
ALIVE AT THIS TIME. SATELLITE IMAGES STILL INDICATE A WELL-DEFINED
CIRCULATION AND ALTHOUGH THE CONVECTION IS NOT VERY DEEP...THE
CLOUD PATTERN REMAINS ORGANIZED WITH AN ESTABLISHED OUTFLOW IN THE
NORTHERN SEMICIRCLE. IN FACT...THE LATEST QUIKSCAT AND AMSU DATA
SUGGEST THAT ZETA COULD BE A LITTLE STRONGER THAN THE INITIAL
INTENSITY OF 45 KNOTS GIVEN IN THIS ADVISORY. THE INITIAL INTENSITY
IS BASED ON CONTINUITY AND SUBJECTIVE DVORAK ESTIMATES.  ACCORDING
TO THE SHIPS MODEL WHICH DISSIPATES ZETA BY 48 HOURS...THE COOLER
THAN NORMAL 200 MB TEMPERATURE IS THE ONLY PARAMETER CONTRIBUTING
TO THE MAINTENANCE OF THE CYCLONE. ON THE OTHER HAND...THE GFDL
INSISTS ON MAKING ZETA A HURRICANE IN A COUPLE OF DAYS AND IT IS
HARD TO GO AGAINST IT. HOWEVER...WITH STRONG WESTERLIES ALOFT AND
DRY AIR HEADING FOR ZETA...I HAVE NO CHOICE BUT TO FORECAST
WEAKENING AGAIN AND AGAIN.

ZETA APPEARS TO BE MOVING TOWARD THE SOUTHWEST AT 3 KNOTS AROUND THE
WESTERN CIRCULATION OF A MID-LEVEL TROUGH. AS THE CYCLONE WEAKENS
AND BECOME A SHALLOWER SYSTEM...IT SHOULD BE STEERED SLOWLY
WESTWARD BY THE TRADE WINDS UNTIL DISSIPATION.

MOST OF THE TROPICAL STORM FORCE WINDS ARE OCCURRING IN THE NORTHERN
SEMICIRCLE AS INDICATED BY QUIKSCAT. THE WIND RADII HAVE BEEN
ADJUSTED ACCORDINGLY.

FORECASTER AVILA


FORECAST POSITIONS AND MAX WINDS

INITIAL      02/0300Z 24.7N  38.7W    45 KT
 12HR VT     02/1200Z 24.6N  39.1W    35 KT
 24HR VT     03/0000Z 24.0N  40.0W    30 KT
 36HR VT     03/1200Z 24.0N  41.5W    25 KT
 48HR VT     04/0000Z 24.0N  43.0W    25 KT...REMNANT LOW
 72HR VT     05/0000Z...DISSIPATED


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