111 
 WTNT41 KNHC 062044
 TCDAT1
 
 Hurricane Florence Discussion Number  30
 NWS National Hurricane Center Miami FL       AL062018
 500 PM AST Thu Sep 06 2018
 
 Vertical shear has taken its toll on Florence today as evidenced by
 a continued degradation of the overall cloud pattern.  The
 circulation appears tilted, with the low-level center partially
 exposed to the southwest of the deep convection.  Subjective and
 objective Dvorak Current Intensity (CI) numbers have fallen, and a
 blend of the various estimates supports an initial intensity of 70
 kt.
 
 The intensity forecast is relatively straightforward in the
 short-term as shear is expected to remain strong, which should
 continue Florence's weakening trend, potentially taking the system
 below hurricane strength.  By 24 hours, vertical shear is forecast
 to decrease, and the SSTs gradually warm along the forecast track.
 Assuming the overall circulation remains intact, Florence shouldn't
 have any problems restrengthening beginning in a day or so. In
 fact, guidance suggests that Florence could once again become a
 major hurricane in 4 or 5 days.  The new NHC intensity forecast is
 essentially an update of the previous one, and is only adjusted to
 account for recent trends.  Largely, the official forecast is close
 to the various consensus aids.
 
 Owing to the degraded structure and tilted nature of the system,
 Florence has wobbled a bit to the west, but the longer-term motion
 estimate is 305/09.  Low- to mid-level ridging should cause
 Florence to turn toward the west-northwest and west between 12-48
 hours while the cyclone recovers from the strong shear.  Thereafter,
 Florence is anticipated to become a deep cyclone again, but an even
 stronger ridge should maintain the west-northwestward motion, at a
 faster speed, through day 5.  The ridge is forecast to be
 sufficiently strong such that some track models show a motion just
 south of due west during the next 12-36 hours.  Beyond day 3, the
 track forecast becomes increasingly uncertain due to differing
 evolutions of the steering pattern over the western Atlantic.  While
 all of the global models show a progressive trough eroding the
 ridge, they differ in the strength of the trough and the ridge to
 the north of Florida.  These differences result in a great deal of
 bifurcation in the track guidance, especially among global model
 ensemble members, at the end of the forecast period. In such
 situations, prudence suggests a reliance on continuity, and the the
 new official NHC track forecast is shifted only slightly south
 towards the TVCN multi-model consensus and HCCA.  It is important to
 note that deterministic track models in these types of situations
 often display considerable run-to-run changes, and the uncertainty
 in this forecast remains larger than normal.
 
 Key Messages:
 
 1. Regardless of Florence's eventual track, large swells will begin
 to affect Bermuda on Friday and portions of the U.S. East Coast this
 weekend, resulting in life-threatening surf and rip currents.
 
 2. There is still very large uncertainty in Florence's track
 beyond day 5, and it is too soon to determine what, if any, other
 impacts Florence could have on the U.S. East Coast next week.
 
 3. Since we are near the peak of hurricane season, this is a good
 time for everyone who lives in a hurricane-prone area to ensure they
 have their hurricane plan in place.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  06/2100Z 25.0N  49.6W   70 KT  80 MPH
  12H  07/0600Z 25.4N  50.7W   60 KT  70 MPH
  24H  07/1800Z 25.5N  52.1W   65 KT  75 MPH
  36H  08/0600Z 25.5N  53.4W   70 KT  80 MPH
  48H  08/1800Z 25.6N  54.6W   75 KT  85 MPH
  72H  09/1800Z 26.4N  57.1W   90 KT 105 MPH
  96H  10/1800Z 28.0N  61.0W  100 KT 115 MPH
 120H  11/1800Z 30.0N  67.0W  105 KT 120 MPH
 
 $$
 Forecaster Berg/Rhome