Tropical Storm BARBARA

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TROPICAL STORM BARBARA DISCUSSION NUMBER   7
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP022007
200 AM PDT THU MAY 31 2007
 
BARBARA CONTINUES TO GENERATE A CLUSTER OF STRONG CONVECTION WITH
TOPS COLDER THAN -80C NEAR THE CENTER...ALTHOUGH THERE IS NO RECENT
MICROWAVE IMAGERY TO SHOW THE EXACT CONVECTIVE STRUCTURE. 
SATELLITE INTENSITY ESTIMATES ARE 45 KT FROM TAFB AND 35 KT FROM
SAB.  BASED ON THIS...THE INITIAL INTENSITY REMAINS 40 KT.

MICROWAVE IMAGES FROM 00Z-03Z SUGGEST THE CENTER WAS A LITTLE TO THE
NORTHEAST OF THE PREVIOUS ADVISORY POSITION...SO THE INITIAL
POSITION FOR THIS ADVISORY IS NUDGED THAT WAY.  THIS YIELDS A
HIGHLY UNCERTAIN INITIAL MOTION OF 130/2.  BARBARA IS EMBEDDED IN
THE INTERTROPICAL CONVERGENCE ZONE EXTENDING FROM A DISTURBANCE
OVER THE NORTHWESTERN CARIBBEAN SEA ACROSS CENTRAL AMERICA INTO THE
PACIFIC...AND A LARGE MID/UPPER-LEVEL TROUGH IS NORTH OF THE
CYCLONE OVER THE GULF OF MEXICO.  THE LARGE-SCALE MODELS FORECAST
THE GULF TROUGH TO AMPLIFY WITH A SURFACE LOW FORMING DURING THE
NEXT 48 HR...THEN MOVING NORTHEASTWARD AWAY FROM BARBARA AFTER THAT
TIME.  THE GFDL... UKMET...ECMWF...GFDN...AND CANADIAN MODELS ALL
BRING BARBARA TO THE COAST OF MEXICO OR GUATEMALA IN 72 HR OR
LESS...WHILE THE GFS CALLS FOR THE STORM TO PERFORM A LOOP AND MOVE
LITTLE DURING THE NEXT 5 DAYS.  BASED ON THE SLIGHTLY FASTER MOTION
IN MOST OF THE GUIDANCE AND THE ADJUSTED POSITION... THE NEW
FORECAST TRACK IS ADJUSTED NORTH OF THE PREVIOUS TRACK. 
HOWEVER...IT SLOWER THAN THE MAJORITY OF THE GUIDANCE AND BRINGS
THE CENTER NEAR THE COAST OF MEXICO IN 96 HR.  AS THE GULF SYSTEM
MOVED AWAY...PRESSURES SHOULD RISE NORTH OF BARBARA AND TURN THE
CYCLONE MORE WESTWARD...ASSUMING THAT IT HAS NOT MOVED ONSHORE BY
THAT TIME.  THIS TRACK FORECAST REMAINS LOW CONFIDENCE.

BARBARA IS IN A COMPLICATED UPPER-LEVEL WIND PATTERN...WITH
HIGH-LEVEL FLOW FROM THE SOUTHEAST BEING UNDERCUT BY NORTHERLY FLOW
AT A SOMEWHAT LOWER LEVEL.  OVERALL...THE STORM HAS POOR OUTFLOW
AND SEEMS TO BE LOSING INFLOW TO THE CARIBBEAN SYSTEM.  THESE
FACTORS HAVE LIKELY SLOWED THE INTENSIFICATION.  THE LARGE-SCALE
MODELS SUGGEST THAT THE UPPER-LEVEL WINDS WILL GRADUALLY BECOME
MORE FAVORABLE DURING THE NEXT 48 HR...WITH THE GFDL CALLING FOR
BARBARA TO BECOME A HURRICANE BY THAT TIME.  THE SHIPS MODEL
FORECAST SLOWER INTENSIFICATION...AND THE INTENSITY FORECAST IS A
COMPROMISE BETWEEN THE TWO CALLING FOR GRADUAL INTENSIFICATION. 
THE FORECAST NOW CALLS FOR SOME WEAKENING AFTER 96 HR DUE TO THE
EXPECTED CLOSE PROXIMITY OF THE CENTER TO THE COAST.

HEAVY RAINS NOW OCCURRING OVER PORTIONS OF CENTRAL AMERICA ARE NOT
DIRECTLY ASSOCIATED WITH BARBARA.  INSTEAD...THIS ACTIVITY IS DUE
TO THE DEVELOPING DISTURBANCE OVER THE NORTHWESTERN CARIBBEAN SEA
AND THE RESULTING NORTHWARD PERTURBATION OF THE ITCZ. 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      31/0900Z 13.2N  96.7W    40 KT
 12HR VT     31/1800Z 12.9N  96.6W    45 KT
 24HR VT     01/0600Z 12.8N  96.5W    50 KT
 36HR VT     01/1800Z 13.3N  96.3W    55 KT
 48HR VT     02/0600Z 13.8N  96.1W    60 KT
 72HR VT     03/0600Z 14.5N  96.0W    65 KT
 96HR VT     04/0600Z 15.5N  96.5W    70 KT
120HR VT     05/0600Z 16.0N  98.0W    65 KT
 
$$
FORECASTER BEVEN
 
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