185 
 WTNT44 KNHC 050857
 TCDAT4
 
 POST-TROPICAL CYCLONE HERMINE DISCUSSION NUMBER  32
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL092016
 500 AM AST MON SEP 05 2016
 
 Hermine remains a post-tropical cyclone with a cloud pattern more
 reminiscent of an extratropical low. However, moderate convection
 has been developing just north of the surface center in the northern
 semicircle during the past few hours within a region of increasing
 upper-level diffluence. Data from an earlier reconnaissance mission
 along with recent scatterometer data suggest that the intensity
 remains unchanged at 60 kt.
 
 The initial motion is a slow northward drift 010/03 kt. Water vapor
 imagery indicates that an upper-level low has developed east of the
 DelMarVa peninsula and is dropping to the south of Hermine's surface
 center. The latest model guidance is forecasting the surface and
 mid- to upper-level lows to rotate counterclockwise around each
 other for the next 24-36 hours before becoming vertically stacked by
 36-48 hours. This cyclonic interaction has resulted in a significant
 westward shift in the global model tracks, especially by the UKMET
 and ECMWF models. As a result, the official forecast has been
 shifted a little to the west of the previous advisory track, but
 lies along the extreme eastern side of the guidance envelope in the
 event that the models shift back to the east since such complex
 interactions are difficult to forecast from cycle to cycle.
 
 The upper-level flow across Hermine is forecast by all of the global
 models to continue to become more difluent during the next 24 hours,
 which should aid in the development of deep convection near the
 low-level center. By 36-48 hours, the deep-layer vertical is
 expected to decrease from the current 45 kt to less than 10 kt, a
 pattern that is usually conducive for intensification. However,
 those favorable upper-level conditions will be negated by much
 cooler sea-surface temperatures of 23-25 deg C when Hermine will be
 north of the Gulf Stream at that time. The global models are in very
 agreement on both Hermine weakening and the 34-kt wind field
 steadily shrinking by 24 hours and beyond. Further weakening is
 expected through day 4, and both the ECMWF and GFS show Hermine
 dissipating by day 5 over the cold waters of the North Atlantic.
 
 The initial 50-kt wind radii have been adjusted based on data from
 the reconnaissance aircraft and an earlier ASCAT overpass.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  05/0900Z 37.7N  68.3W   60 KT  70 MPH...POST-TROPICAL
  12H  05/1800Z 38.0N  69.1W   60 KT  70 MPH...POST-TROPICAL
  24H  06/0600Z 38.6N  70.2W   55 KT  65 MPH...POST-TROPICAL
  36H  06/1800Z 39.0N  70.4W   45 KT  50 MPH...POST-TROPICAL
  48H  07/0600Z 39.7N  70.1W   40 KT  45 MPH...POST-TROPICAL
  72H  08/0600Z 40.7N  67.7W   35 KT  40 MPH...POST-TROPICAL
  96H  09/0600Z 43.0N  62.7W   30 KT  35 MPH...POST-TROPICAL
 120H  10/0600Z...DISSIPATED
 
 $$
 Forecaster Stewart