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Hurricane NORBERT (Text)

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HURRICANE NORBERT DISCUSSION NUMBER  24
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   EP152008
200 PM PDT THU OCT 09 2008
 
SOMETIMES APPEARANCES ARE NOT WHAT THEY SEEM.  ALTHOUGH SATELLITE
ESTIMATES YIELD A MAXIMUM INTENSITY OF 90-100 KT...THE AIR FORCE
HURRICANE HUNTER FLYING THROUGH NORBERT FOUND WINDS THAT WERE MUCH
LOWER.  THE MAXIMUM FLIGHT LEVEL WIND MEASURED WAS 83 KT WITHIN THE
OUTER EYEWALL IN THE NORTHEAST QUADRANT WHILE THE SFMR ONLY
INDICATED WINDS NEAR 65 KT.  THE INITIAL INTENSITY IS LOWERED TO 80
KT...BUT THIS IS LIKELY GENEROUS.  DROPSONDE DATA INDICATE THAT
THERE MIGHT BE A STABLE LAYER BETWEEN 700 AND 800 MB THAT IS
PREVENTING VERTICAL MIXING OF THE STRONG WINDS FROM FLIGHT LEVEL.
 
THE OFFICIAL INTENSITY FORECAST HAS BEEN ADJUSTED DOWNWARD TO
ACCOUNT FOR THE LOWER INITIAL WIND SPEED.  SINCE SEA SURFACE
TEMPERATURES WILL REMAIN WARM ALONG THE FORECAST TRACK UP UNTIL THE
BAJA COAST...ONLY SLOW WEAKENING IS EXPECTED DURING THE FIRST 24
HOURS BASED ON RECENT TRENDS.  THEREAFTER...VERTICAL SHEAR
INCREASES SUBSTANTIALLY...AND NORBERT WILL LIKELY WEAKEN A LITTLE
FASTER.  THE 48-HOUR FORECAST POINT JUST OFFSHORE THE BAJA
PENINSULA STILL INDICATES NORBERT AS A HURRICANE FOR CONTINUITY
ALTHOUGH IT IS POSSIBLE THAT THE CYCLONE COULD HAVE WEAKENED TO A
TROPICAL STORM BY THEN.  ONCE NORBERT REACHES MAINLAND MEXICO...THE
LOW-LEVEL CIRCULATION IS NOT EXPECTED TO SURVIVE THE RUGGED TERRAIN
OF THE SIERRA MADRES IN MEXICO SO NO FORECAST POINTS ARE GIVEN
BEYOND 72 HOURS.  STILL...THE MID-LEVEL REMNANTS AND ASSOCIATED
HEAVY RAINFALL ARE EXPECTED TO MOVE NORTHEASTWARD AND AFFECT
PORTIONS OF NORTHERN MEXICO AND THE SOUTHWESTERN AND SOUTH-CENTRAL
UNITED STATES THROUGH DAY 4 AND 5.
 
NORBERT CONTINUES TO WOBBLE AND HAS SLOWED DOWN TO A MOTION OF
320/4.  THE TRACK MODEL GUIDANCE HAS NOT CHANGED APPRECIABLY SINCE
THIS MORNING AND CONTINUES TO SHOW NORBERT MOVING NORTH THEN
NORTH-NORTHEAST TOWARDS THE BAJA PENINSULA IN RESPONSE TO A DEEP
MID-LATITUDE TROUGH OVER THE WESTERN UNITED STATES.  THE GFS
REMAINS THE ONLY MODEL TO SHEAR THE SYSTEM SO MUCH THAT THE
LOW-LEVEL CIRCULATION IS LEFT TO MEANDER OFFSHORE AND NOT MOVE INTO
MEXICO.
 
WATCHES ARE NOT YET NEEDED FOR THE BAJA COAST SINCE NORBERT HAS
SLOWED DOWN...BUT THEY MAY BE REQUIRED THIS EVENING.

FORECAST POSITIONS AND MAX WINDS
 
INITIAL      09/2100Z 18.3N 112.9W    80 KT
 12HR VT     10/0600Z 18.9N 113.5W    80 KT
 24HR VT     10/1800Z 20.5N 113.7W    75 KT
 36HR VT     11/0600Z 22.1N 113.3W    70 KT
 48HR VT     11/1800Z 24.1N 111.8W    65 KT
 72HR VT     12/1800Z 27.5N 109.0W    30 KT...INLAND
 96HR VT     13/1800Z...DISSIPATED INLAND
 
$$
FORECASTER BERG
 
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