CPAC: FERNANDA - Post-Tropical

[Kingarabian]

6.0/6.5 from SAB.

Thinking the NHC will keep it at 125kts.

Thinking Fernanda will transition from a classic hurricane structure to a buzzsaw structure. Then based on the conditions, a Daniel 2006 type structure.

[cycloneye]

They went down.

EP, 06, 2017071512, , BEST, 0, 110N, 1224W, 120, 952, HU

[gfsperpendicular]

6.0/6.5 from SAB.

Thinking the NHC will keep it at 125kts.

Thinking Fernanda will transition from a classic hurricane structure to a buzzsaw structure. Then based on the conditions, a Daniel 2006 type structure.

What exactly is the buzz saw structure?

[cycloneye]

Hurricane Fernanda Discussion Number 15
NWS National Hurricane Center Miami FL EP062017
800 AM PDT Sat Jul 15 2017

An AMSR2 overpass around 0925 UTC shows that Fernanda is
undergoing an eyewall replacement cycle (ERC). Based on the 36 GHz
composite image from that pass, the inner core at that
time consisted of a very small, 10 nm-wide, inner eyewall surrounded
by a 30 nm-wide outer eyewall. An earlier WindSat pass at 0149 UTC
suggests that the ERC began about 12 hours ago. This is
consistent with a warming trend observed in the cloud top
temperatures that began a little before 0000 UTC yesterday. The
initial intensity has been decreased to 120 kt, based on a blend of
Dvorak estimates from TAFB, SAB, and the UW-CIMSS ADT.

Assuming a typical ERC weakening period of about 15 hours, the
hurricane could reintensify later today, once the outer eyewall
contracts. The environment should support intensification for
another 24 hours or so, and the forecast reflects this. Additional
ERCs could lead to fluctuations in intensity that aren't explicitly
shown in the forecast. After about 36 hours, the hurricane will
become embedded in a drier and more stable environment, so steady
weakening is anticipated. The new forecast is similar to the
previous one, despite the weaker initial intensity, and is above
most of the intensity guidance for the first 36 hours. It is close
to the intensity consensus by the end of the forecast period.

Fernanda is beginning to make a long-anticipated turn toward the
west-northwest and the initial motion is now just north of due
west, or 275/11. Almost no change has been made to the track
forecast, which remains on top of the various multi-model consensus
aids. A west-northwest to northwest motion is expected for the
next several days while the cyclone moves along the southwestern
periphery of a deep-layer ridge. The track guidance is still
tightly clustered, and confidence remains high in the track
forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 15/1500Z 11.0N 123.0W 120 KT 140 MPH
12H 16/0000Z 11.5N 124.8W 130 KT 150 MPH
24H 16/1200Z 12.3N 127.3W 130 KT 150 MPH
36H 17/0000Z 13.0N 129.7W 125 KT 145 MPH
48H 17/1200Z 13.8N 131.9W 120 KT 140 MPH
72H 18/1200Z 15.3N 135.3W 95 KT 110 MPH
96H 19/1200Z 16.5N 138.0W 70 KT 80 MPH
120H 20/1200Z 17.0N 141.0W 50 KT 60 MPH

$$
Forecaster Zelinsky

[Ntxw]

She's held pretty steady overnight after weakening a little bit yesterday evening. 120kts seems justifiable

[RL3AO]

[gatorcane]

Textbook major hurricane...saved loop. What a beautiful storm:

[Kingarabian]

15/1800 UTC 11.3N 123.4W T5.5/6.0 FERNANDA -- East Pacific

[cycloneye]

I tought it was to get a little stronger by now but it looks that has peaked last night.

EP, 06, 2017071518, , BEST, 0, 112N, 1234W, 115, 955, HU

[Kingarabian]

6.0/6.5 from SAB.

Thinking the NHC will keep it at 125kts.

Thinking Fernanda will transition from a classic hurricane structure to a buzzsaw structure. Then based on the conditions, a Daniel 2006 type structure.

What exactly is the buzz saw structure?

Example:



That transition seems to be taking place now.

[RL3AO]

18z Best Track

Time Intensity Adv. ACE Storm ACE
----------- ----------- ---------- -----------
2017071518 115 1.3225 10.4125

[Kingarabian]

18z Best Track

Time Intensity Adv. ACE Storm ACE
----------- ----------- ---------- -----------
2017071518 115 1.3225 10.4125

There should be an interactive widget that utilizes your code and displays the ACE units.

[Kingarabian]

Shear continues to decrease ahead of it and looks virtually non existent until 140W. Don't understand why the models are weakening this considerably in such conditions.

[Sciencerocks]

I'd estimate maybe 115 knots

[Kingarabian]

Dry air eating away from the outflow. Still a major hurricane.

[cycloneye]

Hurricane Fernanda Discussion Number 16
NWS National Hurricane Center Miami FL EP062017
200 PM PDT Sat Jul 15 2017

A recent AMSU pass indicates that Fernanda continues to have a
double eyewall structure, with the inner eye about 20 n mi in
diameter and the outer eye about 60 n mi across. The appearance of
Fernanda in geostationary satellite images remains impressive with a
small distinct eye surrounding by a ring of cold cloud tops.
The cold cloud tops, however, are not quite as expansive as they
were earlier. Accordingly, the latest satellite intensity estimates
have decreased slightly and range from 105 to 125 kt, and based on
these data, the initial wind speed is lowered a little to 115 kt.
It should be noted that it is common for hurricanes that undergo
eyewall replacement cycles (ERC) to weaken during the beginning of
the process.

Assuming the ERC completes, Fernanda has an opportunity to
restrengthen during the next day or so while it remains in
favorable atmospheric conditions and over warm water. After that
time, steady, or even rapid, weakening is expected as the hurricane
moves over cooler water and into a drier and more stable air mass.
An increase in southwesterly shear should aid in the weakening
process toward the end of the forecast period. The NHC intensity
forecast is at the high end, or slightly above, the guidance in the
short term, but then falls in line with the intensity model
consensus after that. This forecast is a tad lower than the
previous one.

A mid-level ridge located over the western United States is steering
Fernanda westward, or 280 degrees, at 11 kt. A west-northwestward
motion is expected to begin tonight and continue for the next
several days while the hurricane moves toward a weakness at the
western periphery of the ridge. The track models remain in good
agreement, and the NHC track forecast lies near the middle of the
guidance envelope, in best agreement with the various consensus
models.

FORECAST POSITIONS AND MAX WINDS

INIT 15/2100Z 11.4N 124.0W 115 KT 130 MPH
12H 16/0600Z 11.9N 125.8W 125 KT 145 MPH
24H 16/1800Z 12.7N 128.2W 125 KT 145 MPH
36H 17/0600Z 13.4N 130.4W 120 KT 140 MPH
48H 17/1800Z 14.1N 132.3W 105 KT 120 MPH
72H 18/1800Z 15.7N 135.5W 80 KT 90 MPH
96H 19/1800Z 16.8N 138.3W 60 KT 70 MPH
120H 20/1800Z 17.3N 141.6W 50 KT 60 MPH

$$
Forecaster Cangialosi

[Kingarabian]

Looks a lot better. We should see strengthening soon if it continues.

[Kingarabian]

16/0000 UTC 11.6N 124.8W T5.5/6.0 FERNANDA -- East Pacific

Strengthening again.

[Sciencerocks]

16/0000 UTC 11.6N 124.8W T5.5/6.0 FERNANDA -- East Pacific

Strengthening again.

yep

[RL3AO]

0z Best Track

Accumulated Cyclone Energy for Fernanda (06E)
Time Intensity Adv. ACE Storm ACE
----------- ----------- ---------- -----------
2017071600 110 1.21 11.6225