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Tropical Storm Flossie Discussion Number   7
NWS National Hurricane Center Miami FL       EP072019
500 PM HST Mon Jul 29 2019

Flossie's satellite appearance in visible, infrared, and microwave
channels has steadily improved since the previous advisory,
including the development of a small CDO feature. However, nearly
identical to Hurricane Erick this time last night, Flossie's
low-level center has migrated southward toward the strongest
convection and is positioned just north of the coldest cloud tops.
Similarly, Flossie is being affected by occasional intrusions of dry
air and some northerly mid-level wind shear that is undercutting the
otherwise favorable upper-level outflow pattern. The initial
intensity of 55 kt is based on a blend of satellite estimates of
T3.5/55 kt from TAFB, T3.0/45 kt from SAB, and T3.9/63 kt and 60 kt
from UW-CIMMS ADT and SATCON, respectively.

The initial motion estimate is westward or 270/15 kt. Despite the
recent west-southwestward jog -- deja vu Erick last night -- the
models are in excellent agreement that Flossie will move westward
for the next 24 hours along the southern periphery of a deep-layer
subtropical ridge, followed by a turn toward the west-northwest on
Wednesday, with that motion continuing through the remainder of the
forecast period. The new official forecast track is south of and
slightly faster than the previous advisory track, mainly due to the
more southerly initial position, and lies between the tightly
clustered consensus models and the more southerly ECMWF model.

If not for dry air mid-level occasionally wrapping into the
hurricane's inner core, Flossie would be poised to rapidly intensify
as per the lastest SHIPS model Rapid Intensification Index (RII).
However, similar to Hurricane Erick, the best course of action is to
just show steady strengthening until a more persistent RI signal
becomes evident. Thus, Flossie is forecast to gradually intensify
into a category 3 hurricane by 72 hours, followed by a near-steady
state condition thereafter due to Flossie moving across cooler
water, which is bounded by the 26C and 26.5C SST isotherms. The
official intensity forecast is very similar to the previous
advisory, and is close to a blend of the NOAA HCCA and the Florida
State Superensemble consensus models.

FORECAST POSITIONS AND MAX WINDS

INIT  30/0300Z 12.3N 117.8W   55 KT  65 MPH
 12H  30/1200Z 12.4N 119.9W   65 KT  75 MPH
 24H  31/0000Z 12.8N 122.4W   75 KT  85 MPH
 36H  31/1200Z 13.3N 125.0W   85 KT 100 MPH
 48H  01/0000Z 14.1N 127.6W   95 KT 110 MPH
 72H  02/0000Z 15.9N 133.5W  100 KT 115 MPH
 96H  03/0000Z 17.4N 139.2W  100 KT 115 MPH
120H  04/0000Z 18.5N 144.4W   90 KT 105 MPH

$$
Forecaster Stewart

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