020 
 WTNT43 KNHC 290252
 TCDAT3
 
 Subtropical Storm Leslie Discussion Number  11
 NWS National Hurricane Center Miami FL       AL132018
 1100 PM AST Fri Sep 28 2018
 
 Convective banding has been consolidating to the south of Leslie's
 center since the afternoon, but recent scatterometer data indicate
 that the maximum winds have decreased to 40 kt and the area of
 gale-force winds has decreased in size.  The convective structure
 suggests that Leslie may be taking on some tropical characteristics,
 but since wave vapor imagery still shows the cyclone embedded within
 a complex deep-layer low, Leslie is still being designated as
 subtropical.
 
 Leslie is moving west-southwestward, or 255 degrees at 10 kt.
 Leslie is entrenched between several mid-tropospheric highs located
 to its east and west, and these features are expected to push
 Leslie slowly southwestward for the next 3 days.  The track
 guidance is tightly clustered during this period, and the NHC
 forecast is very similar to the previous one.  After day 3, Leslie
 is likely to meander on days 4 and 5 in weak steering, and the
 updated official forecast has been adjusted southward and eastward
 at the end of the forecast period to account for the latest model
 solutions.
 
 Global model fields indicate that Leslie has migrated to the
 northwest of its parent upper-level low, which is putting it under
 a regime of moderate north-northeasterly shear.  For the next 48
 hours, this shear is expected to continue, and phase-space diagrams
 suggest that Leslie will be straddling the line between shallow and
 deep warm core.  As a result, only modest strengthening is
 anticipated during this period, and the official forecast maintains
 Leslie as a subtropical storm through 48 hours.  However, the
 transition to a tropical storm could occur any time during the next
 day or two.  After 48 hours, Leslie should definitely be deep warm
 core, and more significant strengthening is expected, with the
 cyclone forecast to reach hurricane intensity by day 4.  This
 scenario is shown by the various intensity models, and the NHC
 intensity forecast is very close to the HFIP Corrected Consensus
 aid and the Florida State Superensemble.  If the statistical-
 dynamical models are correct, Leslie could be stronger by the end of
 the forecast period than is indicated in the NHC forecast.
 
 Large swells generated by Leslie when it was a stronger
 extratropical low have already reached Bermuda, will soon reach the
 Lesser and Greater Antilles, and should reach portions of the east
 coast of the United States later this weekend.  These swells could
 cause life-threatening surf and rip currents.
 
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  29/0300Z 35.7N  49.4W   40 KT  45 MPH
  12H  29/1200Z 34.9N  50.8W   45 KT  50 MPH
  24H  30/0000Z 34.0N  52.0W   45 KT  50 MPH
  36H  30/1200Z 33.5N  53.0W   50 KT  60 MPH
  48H  01/0000Z 33.1N  53.9W   50 KT  60 MPH
  72H  02/0000Z 32.2N  55.4W   60 KT  70 MPH...TROPICAL CYCLONE
  96H  03/0000Z 30.5N  56.0W   65 KT  75 MPH
 120H  04/0000Z 31.5N  56.5W   70 KT  80 MPH
 
 $$
 Forecaster Berg