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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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