[Tropical] Tropical Cyclone Discussion

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WTNT43 KNHC 200852
TCDAT3

Potential Tropical Cyclone Three Discussion Number   3
NWS National Hurricane Center Miami FL       AL032017
400 AM CDT Tue Jun 20 2017

Nighttime infrared satellite imagery suggests that the circulation
associated with the low pressure area in the Gulf of Mexico is
gradually becoming better defined.  However, the system is
struggling to maintain organized convection near the center, and
the radius of maximum winds remains large.  Based on this, the
system is still maintained as a potential tropical cyclone.

The low is moving erratically northwestward around the southwestern
portion of a deep-layer ridge located over the western Atlantic and
Florida.  The large-scale models suggest this ridge will strengthen
some during the next 36 hours or so and cause the low to turn a
little more westward.  This would be followed by a northward turn
around the western end of the ridge and eventual recurvature into
the westerlies.  Overall, there has been a left shift of the track
guidance models since the previous advisory.  The new forecast
track is also shifted left, but it is to the right of the model
consensus, especially at 36-48 h.  Given the nature of the
circulation, though, and the fact that the wind and rain hazards
extend well north and east of the center, users are encouraged to
not focus on the details of the track forecast.

The initial intensity remains 35 kt based on partial scatterometer
overpasses and continuity from the previous advisory.  Significant
strengthening is unlikely due to strong vertical shear caused by an
upper-level trough over the northwestern Gulf of Mexico and
entrainment of dry air into the system.  However, the large-scale
models suggest slight strengthening before landfall, and thus the
intensity forecast is unchanged from the previous advisory.  One
change from the previous advisory is that it now appears more
likely that the system would become a subtropical cyclone than a
tropical cyclone due to the current structure of the low and
interaction with the aforementioned trough.  That being said,
development into a tropical cyclone remains possible.

The primary hazard from this disturbance is expected to be heavy
rainfall over portions of the central and eastern Gulf Coast.


FORECAST POSITIONS AND MAX WINDS

INIT  20/0900Z 24.8N  90.1W   35 KT  40 MPH...POTENTIAL TROP CYCLONE
 12H  20/1800Z 25.7N  91.0W   35 KT  40 MPH...SUBTROPICAL CYCLONE
 24H  21/0600Z 26.6N  92.1W   40 KT  45 MPH
 36H  21/1800Z 27.5N  93.0W   40 KT  45 MPH
 48H  22/0600Z 28.9N  93.5W   40 KT  45 MPH
 72H  23/0600Z 32.5N  93.5W   25 KT  30 MPH...INLAND
 96H  24/0600Z 36.5N  88.0W   20 KT  25 MPH...POST-TROP/INLAND
120H  25/0600Z...DISSIPATED

$$
Forecaster Beven
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