[Tropical] Tropical Cyclone Discussion

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WTNT41 KNHC 060251
TCDAT1

Tropical Storm Nate Discussion Number   7
NWS National Hurricane Center Miami FL       AL162017
1100 PM EDT Thu Oct 05 2017

Nate's center has been moving northwestward across eastern
Honduras, but it is just about to reach the waters of the
northwestern Caribbean Sea.  Despite moving over land for the past
12-15 hours, the cyclone appears to have a relatively intact and
well-defined inner core.  Deep convection has actually been
increasing over the center, and recent 85-GHz microwave data showed
at least some form of a convective ring.  Given these signs, the
maximum winds are being held at 35 kt.  An Air Force Reserve
Hurricane Hunter aircraft will be investigating Nate during the next
several hours to get a better handle on the storm's intensity and
structure.

Nate has been moving northwestward while crossing Nicaragua and
Honduras, and the initial motion estimate is 325/10 kt.  The storm
is currently embedded within a broad Central American gyre, and it
should swing north-northwestward on the east side of this gyre
during the next 36 hours.  After 36 hours, Nate should turn
northward and then northeastward along the western periphery of a
mid-tropospheric high centered off the southeastern U.S. coastline.
Compared to yesterday at this time, the track models have come into
much better agreement, and all the reliable models take Nate's
center across the northeastern portion of the Yucatan peninsula in
24 hours and then across the U.S. central Gulf coast between 48 and
60 hours.  Because of this tight clustering, there are no notable
cross-track changes in the NHC forecast.  Speed-wise, however, the
updated official forecast is a bit faster than the previous one and
has caught up to the various consensus aids.

Due to low shear and very high oceanic heat content in the
northwestern Caribbean Sea, Nate should at least steadily
strengthen once it moves offshore, especially since it appears to
have a well-defined inner core.  Rapid intensification is still not
out of the question, and Nate could be near hurricane intensity by
the time it reaches the Yucatan coast in about 24 hours.  Land
interaction with the Yucatan peninsula could cause a brief hiatus in
the strengthening trend, but conditions should be conducive for
additional intensification while Nate is over the Gulf of Mexico.
Overall, the intensity models have not changed much on this cycle,
and the NHC forecast still calls for a 48-hour intensity of 70 kt,
which is at the upper end of the guidance between HWRF and HCCA.
As mentioned before, Nate could strengthen further in the time
between the 48-hour position and when it crosses the U.S. Gulf
coast.


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 Friday night.

2. Nate could be near hurricane intensity when it approaches the
Yucatan Peninsula late Friday, 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 this weekend 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, have been issued 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  06/0300Z 15.8N  84.7W   35 KT  40 MPH...INLAND
 12H  06/1200Z 17.8N  85.6W   40 KT  45 MPH...OVER WATER
 24H  07/0000Z 20.8N  87.1W   50 KT  60 MPH...INLAND
 36H  07/1200Z 24.3N  89.1W   60 KT  70 MPH...OVER WATER
 48H  08/0000Z 27.5N  90.2W   70 KT  80 MPH
 72H  09/0000Z 33.7N  87.9W   45 KT  50 MPH...INLAND
 96H  10/0000Z 40.0N  79.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  11/0000Z 43.0N  68.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg
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