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Tropical Storm HUMBERTO


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TROPICAL STORM HUMBERTO DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092013
500 AM AST SAT SEP 14 2013
 
HUMBERTO IS IN THE PROCESS OF TRANSITIONING TO A POST-TROPICAL
CYCLONE. THE SYSTEM HAS BEEN DEVOID OF DEEP CONVECTION FOR A
CONSIDERABLE AMOUNT OF TIME...AND IF CONVECTION DOES NOT RETURN
SOON IT WILL LIKELY BE DECLARED A POST-TROPICAL CYCLONE LATER
TODAY. EVEN THOUGH HUMBERTO LACKS THUNDERSTORM ACTIVITY...IT
CONTINUES TO HAVE A LARGE AND WELL-DEFINED LOW-LEVEL CIRCULATION
AND IT IS LIKELY STILL PRODUCING WINDS OF TROPICAL STORM FORCE. THE
INITIAL WIND SPEED IS SET AT 35 KT...ASSUMING A SPIN DOWN FROM THE
EARLIER ASCAT DATA.
 
STRONG SOUTHWESTERLY VERTICAL WIND SHEAR AND DRY STABLE AIR ARE
EXPECTED TO CONTINUE AFFECTING HUMBERTO FOR THE NEXT COUPLE OF
DAYS...SO THE SYSTEM WILL LIKELY REMAIN A POST-TROPICAL CYCLONE
DURING THAT TIME. THE ENVIRONMENTAL CONDITIONS BECOME MORE
FAVORABLE BY MONDAY...AND ALL OF THE INTENSITY MODELS SHOW
HUMBERTO GAINING STRENGTH IN THE 3 TO 5 DAY TIME FRAME. THE NHC
INTENSITY FORECAST FOLLOWS THE TREND OF THE GUIDANCE AND IS IN GOOD
AGREEMENT WITH THE PREVIOUS ADVISORY. SOME OF THE EXPECTED
INTENSIFICATION APPEARS TO BE ASSOCIATED WITH A FAVORABLE TROUGH
INTERACTION.
 
THE STORM IS ON A WESTWARD PATH...AND THE LATEST INITIAL MOTION
ESTIMATE IS 275/8. A CONTINUED WESTWARD MOTION IS EXPECTED
THROUGHOUT THE DAY WHILE THE SYSTEM REMAINS ON THE SOUTH SIDE OF A
DEEP-LAYER RIDGE. AFTER THAT TIME...A GRADUAL TURN TO THE RIGHT IS
FORECAST WHEN THE CYCLONE NEARS THE WESTERN EDGE OF THE RIDGE.
HUMBERTO...OR ITS REMNANT LOW...IS EXPECTED TO RECURVE IN ABOUT 4
DAYS WHEN IT BECOMES EMBEDDED IN SOUTHERLY STEERING FLOW BETWEEN
THE RIDGE AN APPROACHING TROUGH. ALTHOUGH THE MODELS AGREE ON THIS
OVERALL SCENARIO...THERE ARE SIGNIFICANT DIFFERENCES IN FORWARD
SPEED DURING THE RECURVATURE STAGE...WITH THE GFS BEING THE FASTEST
AND THE ECMWF THE SLOWEST. THE OFFICIAL TRACK FORECAST IS BETWEEN
THOSE MODELS AND LIES VERY NEAR THE CONSENSUS AIDS...TVCA AND TV15.
  
FORECAST POSITIONS AND MAX WINDS
 
INIT  14/0900Z 25.0N  34.0W   35 KT  40 MPH
 12H  14/1800Z 25.3N  35.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 24H  15/0600Z 26.2N  38.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  15/1800Z 27.2N  40.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  16/0600Z 28.1N  41.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  17/0600Z 30.5N  44.0W   40 KT  45 MPH
 96H  18/0600Z 33.0N  44.5W   50 KT  60 MPH
120H  19/0600Z 37.0N  42.0W   65 KT  75 MPH
 
$$
FORECASTER CANGIALOSI
 
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