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Tropical Storm HUMBERTO


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TROPICAL STORM HUMBERTO DISCUSSION NUMBER  28
NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092013
500 AM AST TUE SEP 17 2013
 
HUMBERTO CONTINUES TO GO THROUGH CYCLES OF HAVING DEEP CONVECTION
NEAR ITS CENTER TO BEING SHEARED WITH ALL THE CONVECTION DISPLACED
WELL TO THE NORTHEAST OF THE CENTER.  AS OF RIGHT NOW...CONVECTION
HAS RE-DEVELOPED NEAR THE CENTER...AND THERE ARE SIGNS THAT THE
SHEAR MAY BE RELAXING.  THE INITIAL INTENSITY IS HELD AT 35 KT FOR
THIS ADVISORY BASED ON A CURRENT INTENSITY ESTIMATE OF 2.5 FROM
TAFB AND EARLIER ASCAT DATA.  THE LOWEST PRESSURE MEASURED BY A
DROPSONDE FROM A RECENT NASA GLOBAL HAWK MISSION WAS 1009 MB WITH A
SURFACE WIND OF 15 KT...INDICATING THAT THE MINIMUM PRESSURE IS
PROBABLY A LITTLE HIGHER THAN PREVIOUSLY ESTIMATED.
 
THE WAXING AND WANING OF CONVECTION HAS CAUSED THE SURFACE CENTER TO
JUMP AND MEANDER FOR THE PAST 12 TO 24 HOURS.  HOWEVER...IT APPEARS
THAT HUMBERTO IS NOW MOVING AGAIN...AND A LONGER-TERM AVERAGE
YIELDS AN ESTIMATED MOTION OF 020/4 KT.  THE STORM IS LOCATED TO
THE SOUTHWEST OF A MID-LEVEL ANTICYCLONE CENTERED NEAR THE AZORES
AND TO THE SOUTHEAST OF A HIGH-AMPLITUDE MID-LATITUDE TROUGH MOVING
OFF THE EAST COAST OF NORTH AMERICA.  THE RESULTANT STEERING FLOW
IS FORECAST TO PUSH HUMBERTO GENERALLY TO THE NORTH DURING THE NEXT
48 HOURS OR SO...AND THEN THE CYCLONE WILL ACCELERATE TOWARD THE
NORTHEAST BEGINNING ON DAY 3 AS THE TROUGH GETS CLOSER.  THE HWRF
IS THE MAIN OUTLIER IN THE GUIDANCE SUITE...SHOWING A MUCH SLOWER
MOTION AND A TRACK TO THE EAST BY DAY 5.  THE REST OF THE TRACK
MODELS ARE IN REASONABLE AGREEMENT...AND THE OFFICIAL TRACK
FORECAST IS FASTER THAN THE MULTI-MODEL CONSENSUS TVCA TO DOWNPLAY
THE INFLUENCE OF THE HWRF SOLUTION.
 
THE CIRCULATIONS OF HUMBERTO AND A NEARBY MID-/UPPER-LEVEL LOW
ARE BECOMING COLLOCATED...WHICH SHOULD ALLOW THE VERTICAL SHEAR NEAR
THE CYCLONE TO DECREASE DURING THE NEXT DAY OR SO.  THEREFORE...
GRADUAL STRENGTHENING IS INDICATED IN THE OFFICIAL FORECAST DURING
THE NEXT SEVERAL DAYS...MORE OR LESS IN LINE WITH THE INTENSITY
CONSENSUS.  HUMBERTO IS NOW FORECAST TO BECOME AN EXTRATROPICAL
CYCLONE BY DAY 4...AND EVEN THOUGH THE CYCLONE WILL BE MOVING OVER
MUCH COLDER WATER BY THAT TIME...BAROCLINIC INFLUENCES COULD ALLOW
STRENGTHENING TO CONTINUE A BIT LONGER.  A 5-DAY POSITION IS STILL
SHOWN FOR CONTINUITY...BUT IT IS POSSIBLE THAT HUMBERTO COULD BE
ABSORBED BY ANOTHER LARGER EXTRATROPICAL CYCLONE BY THAT TIME.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  17/0900Z 27.8N  42.7W   35 KT  40 MPH
 12H  17/1800Z 28.9N  43.5W   35 KT  40 MPH
 24H  18/0600Z 29.8N  44.0W   35 KT  40 MPH
 36H  18/1800Z 30.7N  43.9W   40 KT  45 MPH
 48H  19/0600Z 31.9N  43.5W   40 KT  45 MPH
 72H  20/0600Z 35.5N  40.5W   45 KT  50 MPH
 96H  21/0600Z 45.0N  33.0W   55 KT  65 MPH...POST-TROP/EXTRATROP
120H  22/0600Z 54.0N  26.5W   50 KT  60 MPH...POST-TROP/EXTRATROP
 
$$
FORECASTER BERG
 
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