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TROPICAL STORM CRISTINA DISCUSSION NUMBER  13
NATIONAL WEATHER SERVICE MIAMI FL
8 AM PDT FRI JUL 12 2002

THE BEST WAY TO DESCRIBE CHRISTINA THIS MORNING IS MESSY.  ALTHOUGH
THE STORM CONTINUES TO GENERATE VERY COLD CONVECTIVE TOPS...THE
CLOUD PATTERN REMAINS RATHER RAGGED.  A TRMM OVERPASS AT 1003Z
SHOWED AN EXPOSED CENTER JUST NORTHWEST OF THE PRIMARY CONVECTION...
AND IR IMAGERY SUGGESTS LITTLE CHANGE IN STRUCTURE SINCE THAT TIME.
THE INITIAL INTENSITY WILL REMAIN 35 KT...ALTHOUGH SINCE SATELLITE
INTENSITY ESTIMATES FROM TAFB...SAB...AND AFWA ARE 55 KT...45
KT...AND 45 KT RESPECTIVELY THIS MIGHT BE A LITTLE LOW.

THE INITIAL MOTION REMAINS 270/10.  THE FORECAST SCENARIO IS ALSO
MESSY.  THE AVN...UKMET...NOGAPS...GFDL...AND GFDN ALL CALL FOR
A NORTHWARD TURN DURING THE NEXT 24 HR.  THE BAM MODELS AND LBAR
CALL FOR A WEST-NORTHWESTWARD MOTION FOR 72 HR...WHILE THE NHC91
WANTS TO TAKE CHRISTINA SOUTHWESTWARD.  WATER VAPOR IMAGERY SHOWS
AN UPPER-LEVEL LOW NEAR SOUTHERN BAJA CALIFORNIA AND RIDGING
COVERING THE AREA SOUTH OF 30N BETWEEN 120W-140W...WITH UPPER-LEVEL
CONVERGENCE AND SUBSIDENCE OCCURRING NEAR 25N120W.  THIS SUGGESTS
THE LOWER-LEVEL RIDGE SHOULD BE STRENGTHENING...WHICH ALONG WITH
THE CURRENT MOTION WOULD ARGUE AGAINST AN IMMEDIATE TURN TO THE
NORTH.  HOWEVER...THE AGREEMENT OF THE LARGE-SCALE MODELS IS HARD
TO ARGUE WITH.  THE FORECAST TRACK IS THUS A COMPROMISE...CALLING
FOR A WESTWARD TO WEST-NORTHWESTWARD MOTION FROM 12-24 HR FOLLOWED
BY A NORTHERLY TURN IN RESPONSE TO A DEVELOPING UPPER-LEVEL TROUGH.
IT IS SIMILAR TO...BUT A LITTLE WEST OF THE PREVIOUS TRACK.
 
SHEAR HAS DECREASED OVER CHRISTINA...AND FAIR OUTFLOW HAS DEVELOPED
EXCEPT TO THE NORTH WHERE IT IS STILL POOR.  CONDITIONS ARE THUS
FAVORABLE FOR STRENGTHENING IF THE STORM CAN GET ITS ACT TOGETHER
INTERNALLY.  THE INTENSITY FORECAST ASSUMES THIS WILL HAPPEN AND
CALLS FOR CHRISTINA TO STRENGTHEN FOR 48 HR.  BEYOND THAT TIME...
THE STORM SHOULD MOVE OVER COLDER WATER AND BECOME ENTANGLED IN THE
UPPER-LEVEL TROUGH...WHICH SHOULD CAUSE SIGNIFICANT WEAKENING.  ONE
LAST BIT OF MESSINESS IS THAT IF CHRISTINA DOES NOT TURN NORTHWARD
AS SHARPLY AS FORECAST...IT WILL STAY OVER WARMER WATER FURTHER
AWAY FROM THE TROUGH...AND LIKELY BE STRONGER THAN CURRENTLY
FORECAST.
 

FORECASTER BEVEN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     12/1500Z 14.1N 115.2W    35 KTS
12HR VT     13/0000Z 14.3N 116.4W    45 KTS
24HR VT     13/1200Z 15.0N 117.5W    55 KTS
36HR VT     14/0000Z 16.2N 118.3W    60 KTS
48HR VT     14/1200Z 17.6N 118.7W    65 KTS
72HR VT     15/1200Z 20.0N 120.0W    50 KTS
 
 
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