[NCEP Logo] HOME ARCHIVES FORECASTS IMAGERY ABOUT TPC RECONNAISSANCE

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TROPICAL STORM CRISTOBAL DISCUSSION NUMBER  12
NATIONAL WEATHER SERVICE MIAMI FL
5 AM EDT THU AUG 08 2002
 
DEEP CONVECTION WITH CRISTOBAL IS BECOMING INTERMITTENT...AS IT 
APPEARS THAT WESTERLY SHEAR AND DRIER AIR ARE TAKING THEIR TOLL.  
ATTEMPTS TO WRAP AROUND THE NORTH SIDE OF THE CENTER ARE BEING 
SLAPPED AWAY.  THE INITIAL INTENSITY IS HELD AT 40 KT BASED LARGELY 
ON A QUIKSCAT PASS.

THE MODELS CRISTO BALL WAS CLEARLY CLOUDY WITH THIS SYSTEM...AND 
TIME HAS ABOUT RUN OUT ON THEIR PLANS FOR A QUICK GETAWAY.  WITH 
JUST A HINT OF DISCORD AMONGST THE MEMBERS OF THE GUIDANCE 
SUITE...IT IS PERHAPS TIME FOR A NEW STRATEGY.  WATER VAPOR IMAGERY 
SHOWS A SECOND PUSH OF DRIER AIR WITHIN THE MID- TO UPPER-LEVEL 
TROUGH...BUT THIS PUSH IS ALREADY AT THE LONGITUDE OF THE CYCLONE.  
WHILE THE MOST RECENT RUN OF THE AVN AGAIN TAKES CRISTOBAL SMARTLY 
NORTHEASTWARD...THERE IS A TRAILING TROUGH THAT ADVANCES ONLY SLOWLY 
TO THE EAST.  THE OFFICIAL FORECAST...WHICH IS MUCH SLOWER AND 
FARTHER SOUTH THAN THE PREVIOUS ONE...ASSUMES THAT CRISTOBAL WILL BE 
LEFT BEHIND WITHIN THIS TROUGH IN A RELATIVELY WEAK STEERING FLOW.  
THIS THINKING IS IN BEST AGREEMENT WITH THE MEDIUM BAM MODEL.  
PERHAPS NEEDLESS TO SAY...CONFIDENCE IN THIS FORECAST TRACK IS NOT 
HIGH.

ON THE PRESUMED SLOW EASTERLY TRACK...IT IS NOT EXPECTED THAT THERE 
WILL BE ANY SIGNIFICANT LESSENING OF THE SHEAR UNTIL LATE IN THE 
FORECAST PERIOD...WHEN ANOTHER OPPORTUNITY FOR NORTHEASTWARD 
ACCELERATION ARISES.  AS A RESULT...A STEADY INTENSITY OR SOME 
WEAKENING IS MORE LIKELY THROUGH 48 HOURS.   
 
FORECASTER FRANKLIN
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL     08/0900Z 29.5N  74.7W    40 KTS
12HR VT     08/1800Z 29.6N  74.0W    40 KTS
24HR VT     09/0600Z 30.0N  72.5W    40 KTS
36HR VT     09/1800Z 30.5N  70.8W    35 KTS
48HR VT     10/0600Z 31.0N  69.0W    35 KTS
72HR VT     11/0600Z 32.0N  66.0W    40 KTS
 
 
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