Hurricane BERTHA

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HURRICANE BERTHA DISCUSSION NUMBER  39
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL   AL022008
500 PM EDT SAT JUL 12 2008
 
AN AIR FORCE PLANE HAS COMPLETED TWO PASSES THROUGH THE EYE OF
BERTHA AND THE MAXIMUM FLIGHT LEVEL WINDS WERE 79 AND 74 KT. THE
SFMR ON BOARD OF THE PLANE DID NOT REPORT ANY HURRICANE FORCE
WINDS...IN FACT...THE STRONGEST WINDS WERE 58 KNOTS IN THE
SOUTHEAST QUADRANT.  THE BEST ESTIMATE OF THE INITIAL INTENSITY IS
65 KNOTS...MAKING BERTHA BARELY A HURRICANE. ATMOSPHERIC CONDITIONS
ARE NOT HOSTILE FOR SOME STRENGTHENING BUT BERTHA HAS BEEN LOCATED 
TOO MANY HOURS IN THE SAME AREA PRODUCING UPWELLING. THE HURRICANE
HAS LOST A LOT OF THE DEEP CONVECTION BUT THE LOW-LEVEL CIRCULATION
IS LARGE AND VIGOROUS WHILE THE OUTFLOW IS WELL ESTABLISHED.
THEREFORE...BERTHA COULD GATHER SOME STRENGTH WHEN IT GETS OUT THAT
AREA OF COOL WATERS INDUCED BY THE HURRICANE ITSELF. FOR
NOW...BERTHA IS KEPT AS A 65 KNOT HURRICANE FOR A DAY OR TWO WITH A
GRADUAL WEAKENING THEREAFTER DUE TO INCREASING SHEAR. BERTHA IS
LIKELY TO BECOME LARGER AS IT GAINS LATITUDE AND BEGIN TO INTERACT
WITH THE MID-LATITUDE FLOW. 

BERTHA HAS BARELY MOVED DURING THE DAY. THE PATTERN OF WEAK STEERING
CURRENTS IS EXPECTED TO CONTINUE FOR THE NEXT DAY OR TWO....SO ONLY
A PAINFULLY SLOW NORTHWARD MOTION IS ANTICIPATED. BEYOND THREE
DAYS...BERTHA IS EXPECTED TO BE FULLY EMBEDDED WITHIN THE
MID-LATITUDE CIRCULATION AND LOCATED BETWEEN AN EASTWARD MOVING
TROUGH AND A LARGER CUT OFF LOW TO THE EAST. THIS PATTERN SHOULD
FORCE BERTHA ON A SLOW EASTWARD TRACK. THIS IS THE SOLUTION
PROVIDED MY MOST OF THE GLOBAL MODELS AS WELL AS THE DYNAMICAL TRACK
GUIDANCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INITIAL      12/2100Z 29.9N  62.6W    65 KT
 12HR VT     13/0600Z 30.4N  62.7W    65 KT
 24HR VT     13/1800Z 31.0N  62.7W    65 KT
 36HR VT     14/0600Z 32.0N  62.8W    65 KT
 48HR VT     14/1800Z 33.0N  62.8W    60 KT
 72HR VT     15/1800Z 34.5N  61.5W    55 KT
 96HR VT     16/1800Z 35.5N  59.0W    50 KT
120HR VT     17/1800Z 35.5N  56.0W    50 KT
 
$$
FORECASTER AVILA
 
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