239 
 WTNT41 KNHC 182037
 TCDAT1
 
 TROPICAL STORM FIONA DISCUSSION NUMBER   8
 NWS NATIONAL HURRICANE CENTER MIAMI FL       AL062016
 500 PM AST THU AUG 18 2016
 
 After a brief convective hiatus, deep convection with cloud tops of
 -70C to -75C has redeveloped into a small CDO feature directly
 over the previously exposed low-level circulation center. Satellite
 classifications are T3.0/45 kt and T2.5/35 kt from TAFB and SAB,
 respectively, and UW-CIMSS ADT values have decreased to T3.0/45 kt.
 A blend of these values support an initial intensity of 40 kt.
 
 Fiona is moving a little faster toward the northwest, or 300/09 kt.
 Other than minor fluctuations in the forward speed of the cyclone
 due to intermittent periods of convective re-organization like the
 most recent episode, the latest model guidance continues to be in
 strong agreement on Fiona moving west-northwestward to northwestward
 toward a break in the Bermuda-Azores High for the next 120 hours.
 Given the tightly packed model guidance about the previous few
 forecast tracks, the new NHC track forecast is just an extension of
 the previous advisory, and lies close to but a little slower than
 the consensus model, TVCN.
 
 There is no significant change to the previous intensity forecast or
 rationale. Despite the earlier sharp decrease in deep convection,
 the inner-core wind field of the compact cyclone has remained quite
 robust based on the lack of no arc cloud lines or outflow boundaries
 seen emanating outward from the center in visible satellite today.
 As result, Fiona should be able to generate additional convection in
 the short term and strengthen some during the next 12-24 hours.
 After that time, the global and regional models remain in good
 agreement on the cyclone moving through a band of strong
 southwesterly vertical wind shear of 20-25 kt from 36-72 hours,
 which is expected to induce weakening. However, the amount of
 weakening remains uncertain due to continued mixed dynamic and
 thermodynamic conditions. Although Fiona will be propagating through
 significant shear and into a drier airmass, the small cyclone will
 also be moving over warmer SSTs of 28C-29C and into a region of much
 cooler upper-tropospheric temperatures, which will produce greater
 instability and generate fairly strong convection that could help
 offset the unfavorable shear conditions. Given these mixed signals,
 the official intensity forecast remains an average of the various
 intensity models, which at 72 hours still ranges from hurricane
 strength in the GFDL model to a 25-kt remnant low in the ECMWF and
 Navy-CTCI models.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  18/2100Z 17.0N  41.3W   40 KT  45 MPH
  12H  19/0600Z 17.7N  42.5W   45 KT  50 MPH
  24H  19/1800Z 18.5N  44.3W   45 KT  50 MPH
  36H  20/0600Z 19.6N  46.1W   35 KT  40 MPH
  48H  20/1800Z 20.8N  48.0W   35 KT  40 MPH
  72H  21/1800Z 23.0N  51.7W   35 KT  40 MPH
  96H  22/1800Z 25.0N  55.0W   35 KT  40 MPH
 120H  23/1800Z 27.2N  56.6W   35 KT  40 MPH
 
 $$
 Forecaster Stewart