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Tropical Storm GERT (Text)

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TROPICAL STORM GERT DISCUSSION NUMBER   7
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL072011
1100 AM AST MON AUG 15 2011
 
THE PRESENTATION OF GERT IN DOPPLER RADAR IMAGERY FROM BERMUDA 
HAS INDICATED BRIEF PERIODIC TIGHTENING OF THE INNER CORE
CIRCULATION...INCLUDING A SMALL 6-8 NMI DIAMETER EYE-LIKE
FEATURE...ONLY TO HAVE THE CONVECTION WEAKEN OR DISSIPATE 
DUE TO INTRUSIONS OF DRY AIR. AN AIR FORCE RESERVE RECON AIRCRAFT
INVESTIGATING THE CYCLONE HAS FOUND MAXIMUM 850 MB FLIGHT-LEVEL
WINDS OF 53 KT AND A FEW UNCONTAMINATED 49-51 KT SFMR WINDS IN 
THE EASTERN SEMICIRCLE...ACCOMPANIED BY A MINIMUM PRESSURE OF NEAR
1000 MB. BASED ON THIS INFORMATION...THE INTENSITY IS SET AT 50 KT
FOR THIS ADVISORY.

THE INITIAL MOTION ESTIMATE IS 010/10 KT. THERE IS NO CHANGE TO THE
PREVIOUS FORECAST REASONING. GERT HAS BEEN MOVING NORTHWARD THROUGH
A BREAK IN THE SUBTROPICAL RIDGE AND HAS NOW REACHED THE AXIS OF
THE EAST-WEST ORIENTED RIDGE THAT LIES ALONG 32N LATITUDE. AS THE
LARGE FULL LATITUDE TROUGH CURRENTLY MOVING OFF THE U.S. EAST COAST
CONTINUES ITS EASTWARD PROGRESS...GERT SHOULD GRADUALLY ACCELERATE
AND TURN TOWARD THE NORTH-NORTHEAST LATER TODAY AND TOWARD THE
NORTHEAST BY LATE TONIGHT OR TUESDAY. THE OFFICIAL TRACK FORECAST
IS A LITTLE TO THE RIGHT OF THE PREVIOUS TRACK AND IS A BLEND OF
THE ECMWF AND GFS MODEL SOLUTIONS.
 
SOME FURTHER INTENSIFICATION OF GERT IS POSSIBLE DURING THE NEXT 24
HOURS AS THE CYCLONE REMAINS OVER RELATIVELY WARM WATER AND BENEATH
AN UPPER-LEVEL ANTICYCLONE. HOWEVER...GERT IS A SMALLER THAN AVERAGE
SIZE TROPICAL CYCLONE...WHICH MEANS IT WILL BE SUSCEPTIBLE TO
INTRUSIONS OF DRY AIR AND SLIGHT INCREASES IN VERTICAL SHEAR. AS A
RESULT...THE INTENSITY FORECAST IS BEING HELD JUST BELOW HURRICANE
STRENGTH. BY 24 HOURS...GERT WILL BE MOVING OVER SEA-SURFACE
TEMPERATURES COOLER THAN 26C...AND OVER WATER COOLER THAN 20C BY 48
HOURS. AS A RESULT...GRADUAL WEAKENING IS EXPECTED AFTER 24 HOURS
AND EXTRATROPICAL TRANSITION IS EXPECTED TO OCCUR BY 48 HOURS WHEN
THE CYCLONE BEGINS TO MERGE WITH A FRONTAL SYSTEM AND ALSO BEGINS
TO FEEL THE EFFECTS OF STRONG SOUTHWESTERLY UPPER-LEVEL WIND SHEAR.
THE INTENSITY FORECAST IS SIMILAR TO THE PREVIOUS ADVISORY AND
CLOSELY FOLLOWS THE SHIPS AND LGEM MODEL SOLUTIONS. EXTRATROPICAL
INTENSITY FORECASTS WERE PROVIDED BY THE NOAA OCEAN PREDICTION
CENTER.
 
THE BERMUDA WEATHER SERVICE HAS DISCONTINUED THE TROPICAL STORM
WARNING FOR BERMUDA.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  15/1500Z 32.0N  63.2W   50 KT  60 MPH
 12H  16/0000Z 34.3N  62.0W   55 KT  65 MPH
 24H  16/1200Z 37.8N  59.0W   60 KT  70 MPH
 36H  17/0000Z 40.8N  54.6W   55 KT  65 MPH
 48H  17/1200Z 43.4N  48.5W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  18/1200Z 48.5N  33.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
 96H  19/1200Z...DISSIPATED
 
$$
FORECASTER STEWART
 
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