Tropical Storm CRISTOBAL

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TROPICAL STORM CRISTOBAL DISCUSSION NUMBER   6
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL032008
500 AM EDT SUN JUL 20 2008
 
THE SATELLITE PRESENTATION OF CRISTOBAL REMAINED UNIMPRESSIVE-
LOOKING OVERNIGHT.  THERE HAS BEEN VERY LITTLE DEEP CONVECTION NEAR
THE CENTER WITH THE PRIMARY BANDS OF THUNDERSTORMS WELL DISPLACED
TO THE SOUTH AND SOUTHEAST.  FLIGHT-LEVEL WINDS FROM AIR FORCE
HURRICANE HUNTER DATA INDICATE THAT THE MAXIMUM WINDS REMAIN NEAR
40 KT.  SOME SFMR READINGS FROM THE AIRCRAFT GAVE HIGHER SURFACE
WINDS BUT THESE APPEAR TO BE ERRONEOUS DUE TO INTERFERENCE.
ALTHOUGH SURFACE OBSERVATIONS SHOW LITTLE EVIDENCE OF DRY
AIR...WATER VAPOR IMAGERY SHOWS SOME EVIDENCE OF MID-LEVEL
SUBSIDENCE OVER THE NORTHEASTERN PORTION OF THE CIRCULATION AND
UPPER-LEVEL OUTFLOW IS BEING SHUNTED OVER THE NORTHERN SEMICIRCLE.   
200 MB WIND FORECASTS FROM THE GFS SUGGEST A MORE FAVORABLE
UPPER-LEVEL ENVIRONMENT WITHIN THE NEXT DAY OR SO...AND SOME
INTENSIFICATION IS FORECAST AS IN THE PREVIOUS ADVISORIES.  THE
OFFICIAL WIND SPEED FORECAST IS A LITTLE HIGHER THAN THE INTENSITY
FORECAST MODEL CONSENSUS.  WITHIN 2-3 DAYS THE SYSTEM IS EXPECTED
TO LOSE STRENGTH DUE TO RAPIDLY INCREASING SOUTHWESTERLY
SHEAR...AND LOSE TROPICAL CHARACTERISTICS.

THE INITIAL MOTION IS SLOWLY NORTHEASTWARD...040/5.  CRISTOBAL IS
EXPECTED TO GRADUALLY INCREASE ITS FORWARD SPEED AS IT BECOMES
PICKED UP IN THE FLOW AHEAD OF A BROAD MID-TROPOSPHERIC TROUGH.  BY
72-96 HOURS OR SOONER THE SYSTEM IS EXPECTED TO MERGE WITH A LARGER
EXTRATROPICAL CYCLONE NEAR THE CANADIAN MARITIMES.  THE OFFICIAL
TRACK FORECAST IS ABOUT IN THE MIDDLE OF THE MODEL GUIDANCE AND
SIMILAR TO THE PREVIOUS NHC TRACK.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      20/0900Z 33.9N  77.2W    40 KT
 12HR VT     20/1800Z 34.7N  76.0W    45 KT
 24HR VT     21/0600Z 35.8N  74.4W    50 KT
 36HR VT     21/1800Z 37.5N  72.0W    55 KT
 48HR VT     22/0600Z 40.2N  69.0W    45 KT
 72HR VT     23/0600Z 47.0N  61.0W    35 KT...EXTRATROPICAL
 96HR VT     24/0600Z...ABSORBED
 
$$
FORECASTER PASCH
 
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