Tropical Storm BETA

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TROPICAL STORM BETA DISCUSSION NUMBER   4
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
5 PM EDT THU OCT 27 2005
 
BETA REMAINS A SMALL AND WELL-ORGANIZED TROPICAL STORM THIS
AFTERNOON.  VISIBLE IMAGERY SHOWS THAT THE CENTRAL DENSE OVERCAST
PATTERN SEEN THIS MORNING HAS BECOME MORE OF A CURVED BAND
PATTERN...WITH INFRARED IMAGERY SHOWING TOPS OF -75C TO -80C.  AN
AMSU OVERPASS AT 1547Z SHOWED A BANDING EYE UNDERNEATH THE
CONVECTIVE TOPS.  SATELLITE INTENSITY ESTIMATES ARE 55 KT FROM
TAFB...45 KT FROM SAB...AND 30 KT FROM AFWA.  BASED ON THIS...THE
INITIAL INTENSITY IS INCREASED TO 50 KT.

THE INITIAL MOTION IS 350/3.  BETA IS DRIFTING TOWARD A WEAKNESS IN
THE SUBTROPICAL RIDGE CAUSED BY A LARGE DEEP-LAYER TROUGH OVER THE
EASTERN UNITED STATES.  LARGE-SCALE MODELS SUGGEST THAT AFTER A
SERIES OF SHORTWAVES PASS THROUGH THE SOUTHERN END OF THE TROUGH IN
THE NEXT 24-36 HR...THE TROUGH SHOULD LIFT A LITTLE NORTHWARD AND
ALLOW A WEAK RIDGE TO BUILD ACROSS THE NORTHWESTERN CARIBBEAN.
THIS EVOLUTION SHOULD CAUSE BETA TO DRIFT SLOWLY NORTHWARD OR
NORTH-NORTHWESTWARD FOR THE NEXT 24-36 HR...FOLLOWED BY A WESTWARD
MOTION.  THE DYNAMICAL MODELS GENERALLY AGREE ON THIS SCENARIO...
WITH THE GFS AND GFDL CALLING FOR A WESTWARD TO WEST-SOUTHWESTWARD
TURN...AND THE UKMET AND NOGAPS CALLING FOR A MORE GRADUAL WESTWARD
TURN.  THE OFFICIAL FORECAST IS BETWEEN THESE MODELS AND IS JUST
EAST AND NORTH OF THE MODEL CONSENSUS.  IT SHOULD BE NOTED THAT TWO
MODELS WHICH BRING BETA NORTHWARD TOWARD CUBA AND FLORIDA...LBAR
AND THE CANADIAN...HAVE SHOWN A NORTHWARD BIAS IN PREVIOUS SIMILAR
SITUATIONS.  THEREFORE...WHILE NOT BEING RULED OUT AS POSSIBILITIES
THEY ARE BEING GIVEN LITTLE WEIGHT AT THIS TIME.

CONDITIONS CONTINUE TO APPEAR FAVORABLE FOR RAPID INTENSIFICATION...
WITH THE RAPID INTENSIFICATION INDEX ATTACHED TO THE SHIPS MODEL
SHOWING A 55 PERCENT CHANCE OF 25 KT OR GREATER STRENGTHENING
DURING THE NEXT 24 HOURS.  THE NEW INTENSITY FORECAST CALLS FOR
THIS...MAKING BETA A HURRICANE IN JUST OVER 12 HR AND A 75 KT
SYSTEM IN 24 HR.  ONE POSSIBLE RESTRAINING FACTOR IS THAT THE WARM
WATER OF THE SOUTHWESTERN CARIBBEAN IS RELATIVELY SHALLOW...AND THE
SLOW MOTION OF BETA WILL LIKELY RESULT IN SOME UPWELLING OF COLD
WATER.  HOWEVER...THE EFFECTS OF THIS MAY NOT BE FELT FOR 24 HR OR
MORE.  THE INTENSITY FORECAST WILL CALL FOR A SLOWER DEVELOPMENT
RATE AFTER 24 HR BASED ON THIS POSSIBILITY...ALTHOUGH IT WOULD NOT
BE ANY SURPRISE IF BETA GOT STRONGER AND BECAME A MAJOR HURRICANE. 
AFTER LANDFALL...BETA SHOULD WEAKEN..ESPECIALLY WHEN IT REACHES THE
MOUNTAINS OF CENTRAL AMERICA.

MOST OF THE RAINFALL CURRENTLY ASSOCIATED WITH BETA IS OFFSHORE. 
ONCE THE STORM COMES CLOSE ENOUGH TO THE COAST TO BRING THE RAINS
ONSHORE...FLOODS AND MUDSLIDES WILL BECOME SERIOUS THREATS.
 
FORECASTER BEVEN
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      27/2100Z 11.7N  81.4W    50 KT
 12HR VT     28/0600Z 12.1N  81.5W    60 KT
 24HR VT     28/1800Z 12.6N  81.6W    75 KT
 36HR VT     29/0600Z 13.0N  82.0W    85 KT
 48HR VT     29/1800Z 13.3N  82.5W    90 KT
 72HR VT     30/1800Z 13.5N  83.5W    95 KT...NEAR COAST
 96HR VT     31/1800Z 13.5N  85.0W    40 KT...INLAND
120HR VT     01/1800Z 13.0N  87.0W    20 KT...INLAND DISSIPATING
 
 
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