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Tropical Storm Kristy Discussion Number   7
NWS National Hurricane Center Miami FL       EP132018
800 AM PDT Wed Aug 08 2018

Kristy has continues to have the structure of a strongly sheared
tropical cyclone. The low-level center has been difficult to
identify overnight, but recent microwave data indicates that it is
displaced to the northwest of the primary convective mass. The
initial intensity has been held at 40 kt based on a blend of Dvorak
Final-T numbers from TAFB and SAB.

Although the low-level center has been somewhat difficult to track,
it appears that Kristy has begun to turn west-northwestward, and the
initial motion estimate is 290/7 kt. Little change has been made to
the official track forecast, but confidence remains very low. A
break in the subtropical ridge created by Hurricane John should
allow Kristy to continue turning, resulting in a northward motion by
Thursday. Beyond that time, the model spread remains high, fueled by
a combination of uncertainty as to how much John and Kristy will
directly interact, and how much Kristy will respond to an
upper-level trough to the northwest. The GFS is a notable outlier on
the east side of the guidance envelope, and is the only model
showing Kristy wrapping around the circulation of John. For now, the
NHC forecast continues to downplay this possibility, and is a little
to the west of the multi-model consensus.

The intensity guidance spread is also high, ranging from the HWRF
which makes Kristy a hurricane, to the SHIPS and LGEM which forecast
only gradual weakening. Since the shear is forecast to decrease over
the next 12 to 24 hours, and Kristy will be moving away from the
cold wake of Hector and over warmer waters, at least some
strengthening seems likely. By the second half of the forecast
period, the cyclone will be passing over much colder SSTs and
through a drier environment, which should cause the cyclone to
steadily weaken and become a remnant low.  The NHC forecast is now
close to the model consensus IVCN, which is higher this cycle.


FORECAST POSITIONS AND MAX WINDS

INIT  08/1500Z 14.4N 129.3W   40 KT  45 MPH
 12H  09/0000Z 15.0N 130.0W   40 KT  45 MPH
 24H  09/1200Z 15.9N 130.5W   45 KT  50 MPH
 36H  10/0000Z 16.8N 130.6W   45 KT  50 MPH
 48H  10/1200Z 17.7N 130.4W   50 KT  60 MPH
 72H  11/1200Z 19.8N 130.2W   45 KT  50 MPH
 96H  12/1200Z 21.5N 131.5W   35 KT  40 MPH
120H  13/1200Z 22.0N 133.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Zelinsky

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