769 
 WTPZ42 KNHC 020254
 TCDEP2
 
 Tropical Storm Fabio Discussion Number   6
 NWS National Hurricane Center Miami FL       EP072018
 900 PM MDT Sun Jul 01 2018
 
 During the past 18 h, Fabio's satellite appearance has gone from a
 curved band, to a CDO, back to a curved band, and now back to a CDO
 appearance, probably due to significant dry-air intrusions into
 the inner-core region. However, passive microwave data over the past
 few hours, especially a 0044Z SSMI/S overpass, indicate that the
 low-level center has developed closer to a region of very cold
 overshooting cloud tops of -88C to -90C. A closed, 30-35-nmi
 diameter low-level eye was evident in the SSMI/S imagery, but no
 mid-level eye exists due to dry air having eroded the deep
 convection. Having said that, the low-level eye is now embedded well
 within the CDO feature. The 0000 UTC satellite intensity estimate
 was a consensus T3.5/55 kt from TAFB, SAB, and UW-CIMSS ADT.
 However, the advisory is set a little higher at 60 kt based on the
 improved satellite appearance since the 0000Z satellite fixes.
 
 The initial motion estimate is 285/11. After a brief westward jog
 due to the low-level center reforming closer to the deepest
 convection, Fabio appears to have turned back toward the
 west-northwest. The cyclone is expected to continue moving
 west-northwestward around the southwestern periphery of a strong
 deep-layer ridge. The latest NHC model guidance remains tightly
 packed around the previous advisory track, with only a 60-nmi
 cross-track spread. As a result, the new forecast track is just a
 tad south of the previous advisory track, mainly due to the more
 southerly initial position, and lies close to the HCCA and FSSE
 consensus track models.
 
 Now that Fabio has developed a well-defined low-level eye, rapid
 intensification has become more likely given the favorable low shear
 and warm SST environment. However, the main questions are how
 soon, how much, and how long will the rapid strengthening be due to
 the presence of a pronounced mid-level dry air intrusion and the
 lack of a mid-level eye feature. Most of the best-performing model
 intensity guidance shows the greatest amount of strengthening
 occuring during the next 24 h, and the official forecast follows
 suit. After that time, possible cold upwelling beneath the cyclone
 becomes a factor since the cyclone will be moving over shallow warm
 surface waters of around 26 deg C by 48 h. As a result, the peak
 intensity has been capped between 36-48 h. Rapid weakening is
 expected afterwards due to SSTs cooling to 22 deg C by 96 h and
 southwesterly shear also increasing to 15-20 kt by 120 h. The
 official intensity forecast closely follows the HCCA and FSSE
 consensus models.
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  02/0300Z 12.5N 109.5W   60 KT  70 MPH
  12H  02/1200Z 13.0N 111.2W   75 KT  85 MPH
  24H  03/0000Z 13.6N 113.4W   95 KT 110 MPH
  36H  03/1200Z 14.5N 115.8W  110 KT 125 MPH
  48H  04/0000Z 15.5N 118.3W  105 KT 120 MPH
  72H  05/0000Z 17.7N 123.3W   85 KT 100 MPH
  96H  06/0000Z 20.7N 128.2W   55 KT  65 MPH
 120H  07/0000Z 24.0N 132.7W   35 KT  40 MPH...POST-TROPICAL
 
 $$
 Forecaster Stewart
 
 

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