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 755 
 WTNT41 KNHC 042056
 TCDAT1
 
 HURRICANE ARTHUR DISCUSSION NUMBER  16
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL012014
 500 PM EDT FRI JUL 04 2014
 
 The cloud pattern of Arthur remains very symmetric with a hint of an
 eye remaining in visibile and infrared satellite imagery, although
 the cloud tops have continued to gradually warm during the day.
 Recent reconnaissance data show that the radius of maximum winds has
 increased, which is likely the first sign that the hurricane is
 beginning the transition to a post-tropical cyclone. The aircraft
 data also indicate that the winds aloft are not mixing down as
 efficiently as they were overnight and this morning. In fact, during
 the latest pass through the southeastern quadrant the aircraft
 measured a peak 700-mb flight level wind of 103 kt, but the surface
 winds underneath were only 63 kt. Based on these data, the initial
 intensity is lowered to 70 kt.  Arthur is now located over sea
 surface temperatures of around 24C. The hurricane will be moving
 over progressively colder waters and into an area of increasing
 southwesterly shear, which should result in continued weakening.
 Global model guidance indicates that Arthur should become
 post-tropical tomorrow morning.  After the extratropical transition,
 the cyclone is forecast to continue weakening as it moves over the
 North Atlantic.
 
 The initial motion estimate is 040/23 kt. The hurricane should
 continue to move northeastward during the next 24 to 36 hours in
 deep-layer southwesterly flow ahead of the approaching deep-layer
 trough. After that time, the post-tropical cyclone is forecast to
 slow down and eventually turn east-northeastward.  There is still
 a large amount of spread in the track guidance after 48 hours. The
 updated NHC forecast is between the ECWMF and GFS models, and leans
 toward guidance provided by the NOAA Ocean Prediction Center.
 
 Winds in excess of gale/tropical storm force are expected
 over portions of eastern Maine on Saturday.  Because Arthur is
 expected to be extratropical by Saturday morning, and because the
 strong winds in Maine will be post-frontal, this threat is being
 handled by high wind warnings issued by local NWS offices.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  04/2100Z 39.4N  71.1W   70 KT  80 MPH
  12H  05/0600Z 42.2N  68.2W   60 KT  70 MPH
  24H  05/1800Z 45.3N  65.3W   55 KT  65 MPH...POST-TROP/EXTRATROP
  36H  06/0600Z 47.0N  61.9W   50 KT  60 MPH...POST-TROP/EXTRATROP
  48H  06/1800Z 49.4N  57.2W   40 KT  45 MPH...POST-TROP/EXTRATROP
  72H  07/1800Z 56.0N  51.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
  96H  08/1800Z 60.0N  49.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
 120H  09/1800Z 61.0N  42.5W   25 KT  30 MPH...POST-TROP/EXTRATROP
 
 $$
 Forecaster Brown
 
 
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It was last modified on: , 17 2014 - 1841 UTC
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