Tropical Storm ERNESTO

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TROPICAL STORM ERNESTO DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL052012
1100 PM EDT SAT AUG 04 2012
 
DESPITE AN IMPRESSIVE APPEARANCE IN INFRARED IMAGERY...MICROWAVE
IMAGERY AND REPORTS FROM AN AIR FORCE RESERVE HURRICANE HUNTER
AIRCRAFT INDICATE THAT ERNESTO HAS LOST SOME ORGANIZATION DURING
THE PAST SEVERAL HOURS.  THE MICROWAVE DATA SUGGESTS THAT THE
LOW-LEVEL CENTER HAS BECOME PARTLY EXPOSED TO THE NORTHWEST OF THE
STRONG CONVECTION...AND THE AIRCRAFT REPORTS THAT THE CENTRAL
PRESSURE HAS RISEN TO 1007 MB.  SINCE THE PLANE HAS NOT YET FULLY
SAMPLED THE NORTHEASTERN QUADRANT WHERE THE STRONGEST WINDS WERE
FOUND EARLIER...THE INITIAL INTENSITY IS HELD AT 50 KT.  HOWEVER...
IT IS POSSIBLE THAT THIS ESTIMATE IS GENEROUS.
 
THE LOW-LEVEL CENTER HAS ACCELERATED WEST-NORTHWESTWARD SINCE THE
LAST ADVISORY...WITH A SHORT-TERM FORWARD SPEED OF OVER 20 KT.  A
LONGER-TERM MOTION IS 285/19...WHICH IS THE INITIAL MOTION FOR THE
ADVISORY.  THE REASON FOR THIS TRACK CHANGE IS UNCLEAR.  HOWEVER...
THE GUIDANCE IS IN GOOD AGREEMENT THAT ERNESTO SHOULD RESUME A
WESTWARD MOTION DURING THE NEXT 12 HR OR SO ON THE SOUTH SIDE OF
THE SUBTROPICAL RIDGE.  AFTER 24-36 HR...THE RIDGE SHOULD GRADUALLY
WEAKEN AS A MID/UPPER-LEVEL TROUGH DEVELOPS OVER THE EASTERN UNITED
STATES.  WHILE SOME SPREAD REMAINS...THE GUIDANCE HAS COME INTO
BETTER AGREEMENT THAT ERNESTO WILL TURN WEST-NORTHWESTWARD AT A
REDUCED FORWARD SPEED AFTER 36 HR...MOVING OVER THE YUCATAN
PENINSULA OF MEXICO BETWEEN 72-96 HR AND REACHING THE SOUTHERN OR
SOUTHWESTERN GULF OF MEXICO BY THE END OF THE FORECAST PERIOD.  THE
NEW FORECAST TRACK IS SHIFTED A LITTLE NORTH OF THE PREVIOUS TRACK
THROUGH 24 HR DUE TO THE INITIAL MOTION.  HOWEVER...IT HAS BEEN
SHIFTED SOUTHWARD AFTER THAT TIME TO LIE NEAR THE VARIOUS CONSENSUS
MODELS.  OVERALL...THE NEW FORECAST TRACK IS FASTER THAN THE
PREVIOUS TRACK.
 
IT IS ALSO UNCLEAR WHY ERNESTO HAS LOST ORGANIZATION SINCE THE
OUTFLOW IS GOOD IN ALL DIRECTIONS...THE VERTICAL WIND SHEAR IS
LIGHT...AND THE SEA SURFACE TEMPERATURES ARE WARM.  ONE POSSIBLE
CAUSE MIGHT BE DRY AIR SEEN IN WATER VAPOR IMAGERY WEST OF THE
CYCLONE.  THE DYNAMICAL GUIDANCE CONTINUES TO SUGGEST THAT ERNESTO
WILL NOT STRENGTHEN MUCH BEFORE REACHING THE NORTHWESTERN
CARIBBEAN...WHILE THE STATISTICAL-DYNAMICAL MODELS CONTINUE TO
FORECAST STEADY STRENGTHENING THROUGH THE FORECAST PERIOD.  GIVEN
THE TRENDS DURING THE PAST 24 HR...THE NEW INTENSITY FORECAST CALLS
FOR A LOWER INTENSIFICATION RATE THAN THE PREVIOUS ADVISORY...WITH
ERNESTO BECOMING A HURRICANE IN 48 HR.  GIVE THE DIVERGENT
GUIDANCE...THE INTENSITY FORECAST REMAINS OF LOW CONFIDENCE.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  05/0300Z 15.4N  72.7W   50 KT  60 MPH
 12H  05/1200Z 15.8N  75.5W   50 KT  60 MPH
 24H  06/0000Z 16.1N  78.7W   50 KT  60 MPH
 36H  06/1200Z 16.3N  81.0W   60 KT  70 MPH
 48H  07/0000Z 17.0N  82.9W   65 KT  75 MPH
 72H  08/0000Z 18.5N  86.5W   75 KT  85 MPH
 96H  09/0000Z 20.5N  89.5W   70 KT  80 MPH...INLAND
120H  10/0000Z 22.0N  92.5W   65 KT  75 MPH...OVER WATER
 
$$
FORECASTER BEVEN
 
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