[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 060843
TCDAT1

Tropical Storm Nate Discussion Number   8
NWS National Hurricane Center Miami FL       AL162017
400 AM CDT Fri Oct 06 2017

An Air Force plane fixed the center of Nate as it was moving back
over the waters of the Gulf of Honduras a few hours ago. The minimum
central pressure was estimated at 999 mb, and a combination of
flight-level and the SFMR winds yield an intensity of 40 kt. The
surface circulation is broad, and the strongest winds are within a
cyclonically curved band in the eastern semicircle. Radar from
Honduras also helped to track the center when the cyclone was over
Honduras.  Nate is moving toward the very warm waters of the
northwestern Caribbean Sea and within an environment of light shear.
On this basis, the NHC forecast calls for some strengthening through
the next 48 hours, and Nate is expected to be a Category one
hurricane by the time it is close to the U.S. coast. The interaction
with the Yucatan peninsula, however, could halt the strengthening
temporarily in the 12 to 24 hour period.  Once Nate moves inland
over the U.S., weakening is anticipated and the cyclone most likely
will dissipate by the end of the forecast period.

Nate is moving toward the north-northwest or 340 degrees at 12 kt.
The cyclone is sandwiched between a large cyclonic gyre over
Central America and a developing subtropical ridge over the
western Atlantic. This flow pattern should steer Nate on the same
general north-northwest track with a marked increase in forward
speed for the next 2 days. After that time,  Nate should be on the
northern edge of the subtropical high and become steered toward the
northeast by the mid-latitude westerly flow. The confidence in the
track forecast is high since most of the reliable guidance have come
to a very good agreement, and models are tightly clustered at least
for the next 2 to 3 days.  The NHC forecast is in the middle of the
envelope.

KEY MESSAGES:

1. Heavy rainfall is the main threat from Nate in portions of
Central America, with life-threatening flash flooding and mud slides
possible in portions of Nicaragua, Honduras, Costa Rica, Panama, and
Belize through tonight.

2. There is a possibility that Nate could be near hurricane
intensity when it approaches the Yucatan Peninsula later today
bringing direct impacts from wind, storm surge, and heavy rainfall.
A tropical storm warning and a hurricane watch are in effect for a
portion of this area, and life-threatening flash flooding is also
possible.

3. Nate is forecast to reach the northern Gulf Coast late Saturday
or Sunday morning as a hurricane, and the threat of direct impacts
from wind, storm surge, and heavy rainfall is increasing from
Louisiana through the western Florida Panhandle.  Hurricane and
tropical storm watches, as well as a storm surge watch, are in
effect for a portion of the northern Gulf Coast, and residents in
these areas should monitor the progress of Nate, heeding any advice
given by local officials.


FORECAST POSITIONS AND MAX WINDS

INIT  06/0900Z 16.9N  85.1W   40 KT  45 MPH
 12H  06/1800Z 19.2N  85.9W   50 KT  60 MPH
 24H  07/0600Z 22.7N  87.8W   50 KT  60 MPH
 36H  07/1800Z 26.4N  89.5W   60 KT  70 MPH
 48H  08/0600Z 29.3N  89.6W   70 KT  80 MPH
 72H  09/0600Z 36.0N  84.0W   30 KT  35 MPH...INLAND
 96H  10/0600Z 40.5N  74.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  11/0600Z...DISSIPATED

$$
Forecaster Avila

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