Month: October 2017

2017 Sixteen is the new Nate - Data Dump 10/5

From NHC

Sorry Folks.  Looks like it's coming straight for us.

There is considerable disagreement on the speed of travel and the intensity, but not the track.

Current estimates have it hitting the Louisiana coast as a category 1 with wind speeds of about 80 mph.  However, there is disagreement in this forecast as well as the "when" it will make landfall.

I'm including NHC's discussion.

WTNT41 KNHC 051447

Tropical Storm Nate Discussion Number 5
NWS National Hurricane Center Miami FL AL162017
1100 AM EDT Thu Oct 05 2017

The cloud pattern associated with Tropical Depression Sixteen
increased in organization after the last advisory, with the
formation of a ragged central convective feature and outer banding
in the northeastern semicircle. In addition, data from the
Colombian radar at San Andres showed a partial eyewall, and surface
observations from Puerto Cabezas, Nicaragua, included a pressure of
1001 mb outside of the center. Based on these data, the initial
intensity has been increased to 35 kt, and the depression has been
upgraded to Tropical Storm Nate.

The center of Nate is now inland over northeastern Nicaragua, and
little change in strength is expected until the center moves over
the northwestern Caribbean Sea. After that, a combination of warm
sea surface temperatures and light shear should allow for at least
steady strengthening. However, the guidance is producing mixed
signals despite a favorable-looking environment. The Rapid
Intensification Index of the SHIPS model is showing high chances of
rapid intensification, with better than a 50 percent chance of 25
kt of strengthening in the next 24 h and nearly a 50 percent chance
of 65 kt of strengthening in 72 h. On the other side, the GFS and
Canadian models show only modest development and keep the cyclone
as a tropical storm until it reaches the northern Gulf coast.
Given the environment, the intensity forecast leans towards the high
end of the guidance envelope and calls for Nate to become a
hurricane in about 48 h and reach the northern Gulf Coast as a

The initial motion is 325/8. A combination of a large cyclonic gyre
over Central America, a trough of low pressure moving westward
across the Gulf of Mexico, and a building subtropical ridge over
the western Atlantic should steer Nate generally north-northwestward
with an increase in forward speed during the next 72 h. While the
guidance is in better agreement on the direction that Nate should
move, there remains disagreement on the speed despite an overall
trend toward a faster motion. The new forecast track is similar to
the direction of the previous track, but shows a faster forward
speed that has the center near the northeastern Yucatan Peninsula
in about 36 h and near the northern Gulf Coast in about 72 h.
After the Gulf Coast landfall, Nate or its remnants are expected to
recurve northeastward upon encountering the mid-latitude


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 is forecast to 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. However, it is too early
to specify the exact timing, location, or magnitude of these
impacts. Residents along the Gulf Coast from Louisiana through the
Florida Panhandle should monitor the progress of Nate and heed any
advice given by local officials.


INIT 05/1500Z 14.3N 83.7W 35 KT 40 MPH...INLAND
12H 06/0000Z 15.6N 84.3W 35 KT 40 MPH...INLAND
24H 06/1200Z 18.1N 85.4W 45 KT 50 MPH...OVER WATER
36H 07/0000Z 20.8N 86.8W 55 KT 65 MPH
48H 07/1200Z 23.7N 88.1W 65 KT 75 MPH
72H 08/1200Z 29.5N 89.5W 70 KT 80 MPH
96H 09/1200Z 36.0N 85.0W 30 KT 35 MPH...INLAND
120H 10/1200Z 41.5N 76.5W 20 KT 25 MPH...POST-TROP/INLAND

Forecaster Beven

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2017 Sixteen - 10/4 Data Dump

Click on map to see latest

As with all forecast, there are some limiting factors for accuracy. All I can do is tell you what I see in the data.

  • Rapid intensification in the next three days, approaching category 2, but disrupted by the storm passing over the two landmasses containing Honduras and the Yucatan. This track impedes accurate intensity forecast.
  • Steering currents should be predictable when it gets into the Gulf of Mexico.  (potentially within the next 24-48 hours, they should form). This will allow a track forecast to be produced with a decent amount of accuracy.
  • Currently looking like the re-curve will initially head for Terrebonne Parish but then turn towards the western-most part of the Florida Panhandle.

PLEASE NOTE: It is way to early to bet life and property on a forecast of this storm.  Unfortunately, a decent forecast is impossible until it passes over the Yucatan, which gives a minimum amount of time to prepare.  Please, maintain a level of awareness of this storm over the next few days.

Water Vapor
From NHC 4 pm CST 10/4/2017

WTNT41 KNHC 042051

Tropical Depression Sixteen Discussion Number 2
NWS National Hurricane Center Miami FL AL162017
500 PM EDT Wed Oct 04 2017

Visible satellite images show that the depression has lots of
curved bands, although it is somewhat lacking any inner core
features. An Air Force Reserve Hurricane Hunter flew into the
depression this afternoon and found a well-defined circulation, with
maximum flight-level winds of 37 kt and SFMR values around 30 kt.
These data support keeping the intensity at 30 kt for this advisory.

Environmental conditions look quite favorable for strengthening over
the next few days, with low shear and very warm and deep water in
the path of the cyclone. The various rapid intensification indices
are all higher than the last cycle, suggesting an increasing chance
of rapid intensification occurring. The fly in the ointment,
however, is all of the potential land interaction, first over
Central America and then possibly over the Yucatan Peninsula. As
a compromise, the intensity forecast is raised considerably from the
previous one during the first 3 days, but is still below some
guidance, such as the HWRF.

The depression continues to move slowly northwestward, steered by a
distant ridge over the southwestern Atlantic. However the steering
pattern is forecast to change quickly tomorrow as a mid-tropospheric
trough over the Florida Straits moves across the northwestern
Caribbean into the southwestern Gulf of Mexico. Southerly flow on
the eastern side of that trough should cause the cyclone to move
much faster to the north-northwest by Friday and northward into the
Gulf of Mexico on Saturday. While there is some agreement on the
synoptic pattern, the model track agreement is rather poor, even in
the short term, with the GFS and ECMWF being 90 miles apart on the
forecast track as soon as 24 hours out. This has profound
differences down the road, with the GFS-based guidance moving
considerably faster and to the left of the ECMWF and UKMET across
the Gulf of Mexico. Overall, the guidance has generally shifted a
bit westward since the last cycle, so the latest points in the long
range have been adjusted in that direction. At this point, I
wouldn't focus too much attention on the details of the long-range
forecast until the guidance comes into better agreement. A G-IV
mission and Florida special soundings have been set up for tomorrow
to better determine the synoptic steering flow around the cyclone.


1. The depression is forecast to strengthen and bring tropical storm
conditions to portions of Nicaragua and Honduras tonight through
Friday. Heavy rainfall could produce life-threatening flash
flooding and mud slides in portions of Nicaragua, Honduras, Costa
Rica, and Panama through Friday night.

2. The system is expected to be near hurricane intensity when it
approaches the Yucatan Peninsula late Friday or Saturday, bringing
direct impacts from wind, storm surge, and heavy rainfall. A
hurricane watch could be issued for this area later this evening.

3. The system is forecast to continue strengthening over the Gulf of
Mexico and could affect portions of the northern Gulf Coast as a
hurricane this weekend, with direct impacts from wind, storm surge,
and heavy rainfall. However, it is too early to specify the timing,
location, or magnitude of these impacts. Residents along the Gulf
Coast from Louisiana to Florida should monitor the progress of this
system for the next several days and heed any advice given by local


INIT 04/2100Z 12.5N 82.5W 30 KT 35 MPH
12H 05/0600Z 13.2N 83.1W 40 KT 45 MPH
24H 05/1800Z 14.6N 83.8W 40 KT 45 MPH...INLAND
36H 06/0600Z 16.7N 84.6W 50 KT 60 MPH
48H 06/1800Z 19.5N 85.8W 60 KT 70 MPH
72H 07/1800Z 25.0N 88.0W 75 KT 85 MPH
96H 08/1800Z 30.5N 86.0W 65 KT 75 MPH...INLAND
120H 09/1800Z 35.5N 82.0W 30 KT 35 MPH...POST-TROP/INLAND

Forecaster Blake

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Oct. 4, 2017, Thoughts and Focus

Data is starting to congeal.  Initial projections are looking like it will be heading to Alabama.   The probability of development is now at 90% for the next 24-48 hours.

I'm interested in what the strength potential will be. The Gulf is 4°F above the average temp, there are gale-force winds and 12 ft. seas.  The GOM is angry.  This indicates a lot of energy is available for rapid development once the area crosses the Yucatan.

My intuition tells me that this could be a category 1 or 2 at landfall to the east of the mouth of the Mississippi River.   However, this prediction could radically change within the next 48 hours.

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