EPAC: FERNANDA - Remnants - Discussion

[Ntxw]

Might have already peaked. I'm guessing Fernanda is ~10-15 ACE unit system.

[Yellow Evan]

Can't tell if its dry air or an ERC.

[cheezyWXguy]

Can't tell if its dry air or an ERC.

Looks like ERC to me. MW imagery from earlier didn’t seem to show much development of a secondary eyewall but I know that can change in the span of a couple of hours

[Yellow Evan]

Eye cooling and CDO looking ragged with the coldest cloud tops warming. Early signs of an ERC.

[cycloneye]

EP, 07, 2023081418, , BEST, 0, 158N, 1187W, 115, 955, HU

[aspen]

It’s actually looking better on visible now. The eye is more distinct and the CDO has become more compact. I think this is yet another underestimated EPac major and is/was around 120 kt or so.

[Ntxw]

Eye has recovered some and larger. This is pretty.

[cycloneye]

Hurricane Fernanda Discussion Number 9
NWS National Hurricane Center Miami FL EP072023
1100 AM HST Mon Aug 14 2023

Fernanda has been maintaining a well-defined eye some 10 n mi in
diameter with very cold surrounding convective cloud tops. The
upper-level outflow pattern remains well defined, particularly to
the north. Dvorak current intensity estimates from TAFB and SAB
remain at 115 kt and objective ADT estimates from UW-CIMSS are also
near that value. Thus the intensity estimate is held at 115 kt,
i.e. category 4 strength, for this advisory.

Although there have been some trochoidal wobbles in the motion,
which is fairly common in intense hurricanes, the overall motion
continues to be westward or slightly north of westward at a rather
slow pace, 6 kt. The mid-level ridge to the north of Fernanda is
still rather weak due to the influence of a cutoff low near the
California coast. Global model predictions show the ridge becoming
better established over the next several days, which should result
in some increase in forward speed. In 3-5 days, the shallower and
weaker cyclone is likely to be carried on a westward track
following the lower-level trade wind flow. The official forecast
track is basically an extension of the previous one and remains in
good agreement with the simple and corrected dynamical model
consensus solutions.

Although it is likely that Fernanda has reached its peak intensity,
the hurricane should remain in a favorable SST and atmospheric
thermodynamic environment until tonight so some additional
short-term strengthening is possible. After about 12 hours, the
influences of drier air and cooler waters should begin to take their
toll, so the official forecast shows a steady weakening trend in 1-4
days. This is in good agreement with the corrected consensus, HCCA,
prediction.


FORECAST POSITIONS AND MAX WINDS

INIT 14/2100Z 15.9N 119.0W 115 KT 130 MPH
12H 15/0600Z 16.5N 120.3W 120 KT 140 MPH
24H 15/1800Z 17.2N 122.4W 105 KT 120 MPH
36H 16/0600Z 17.5N 124.8W 85 KT 100 MPH
48H 16/1800Z 17.7N 127.5W 70 KT 80 MPH
60H 17/0600Z 17.9N 130.2W 55 KT 65 MPH
72H 17/1800Z 18.0N 133.0W 40 KT 45 MPH
96H 18/1800Z 18.0N 139.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 19/1800Z 18.0N 145.0W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Pasch

[Sciencerocks]

[Sciencerocks]

[cycloneye]

EP, 07, 2023081500, , BEST, 0, 163N, 1194W, 110, 958, HU

[aspen]

https://imagizer.imageshack.com/img923/8057/wDQOom.gif

Clearly weakening now but dang that’s a lot of eyewall lightning. Maybe a sign it got even stronger, like 125-130 kt. I think 120 kt is a good estimate but who knows for sure without recon.

[Ntxw]

What's left of her may bring some rain to Hawaii.

[cycloneye]

Hurricane Fernanda Discussion Number 10
NWS National Hurricane Center Miami FL EP072023
500 PM HST Mon Aug 14 2023

This evening, Fernanda's inner-core structure is beginning to show
signs of decay, with its well-defined eye becoming cloud filled on
both visible and infrared satellite images. Earlier, a 2144 UTC
AMSR2 microwave pass suggested the hurricane might be undergoing an
eyewall replacement cycle, which could be partially responsible for
its recent structural degradation. 0000 UTC subjective Dvorak
intensity estimates from TAFB and SAB were 115 kt and 102 kt,
respectively. Objective intensity estimates from UW-CIMSS have
either leveled off or have begun to decline, with the most recent
D-MINT estimate at 107 kt associated with the aforementioned AMSR2
pass above. The initial intensity has been lowered to 105 kt this
advisory given the continued decline since that time.

Fernanda has been moving a bit more poleward over the last 6 to 12
hours, with the latest estimated motion at 290/8 kt. The mid-level
ridging has been taking its time building back in to the north over
the past 24 hours, but is still forecast to do so over the next few
days, leading to Fernanda gradually accelerating to the
west-northwest. Beyond 48 hours, a weakening Fernanda should quickly
become more vertically shallow, resulting in the cyclone turning
more westward as it comes under the influence of the more extensive
North Pacific low-level subtropical ridge. The official forecast
continues to be very close to the prior forecast, other than a
short-term nudge further north given the initial motion. This track
remains close to both the simple and corrected consensus model
guidance.

In addition to a possible eyewall replacement cycle, Fernanda might
also be feeling the effects of some higher (15-20 kt) mid-level
vertical wind shear out of the south. Very dry mid-level
environmental air could also be attempting to wrap around the
southwest quadrant of the cyclone. Given these factors, it now seems
more likely Fernanda will continue weakening in the short-term, with
the rate of weakening increasing after it crosses the 26-C isotherm
in about 24-36 hours. Both the global and regional-hurricane models
now show Fernanda losing its organized convection in about 3 days,
with the latest NHC intensity forecast showing the system becoming a
post-tropical remnant low at that time.


FORECAST POSITIONS AND MAX WINDS

INIT 15/0300Z 16.5N 119.8W 105 KT 120 MPH
12H 15/1200Z 17.0N 121.2W 100 KT 115 MPH
24H 16/0000Z 17.4N 123.5W 90 KT 105 MPH
36H 16/1200Z 17.6N 126.0W 70 KT 80 MPH
48H 17/0000Z 17.8N 128.7W 50 KT 60 MPH
60H 17/1200Z 18.0N 131.5W 40 KT 45 MPH
72H 18/0000Z 18.1N 134.6W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 19/0000Z 18.2N 141.0W 30 KT 35 MPH...POST-TROP/REMNT LOW
120H 20/0000Z 18.0N 147.0W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Papin

[Yellow Evan]

Likely some combination of dry air, shear, and an attempted ERC has disrupted the core.

[Yellow Evan]

TXPZ23 KNES 150624
TCSENP

A. 07E (FERNANDA)

B. 15/0600Z

C. 16.8N

D. 120.2W

E. THREE/GOES-W

F. T4.5/5.5

G. IR/EIR/SWIR

H. REMARKS...THE LLCC IS GREATER THAN 0.5 DEGREE INTO THE LG OVC WHICH
YIELDS A DT=4.5. MET=5.0. PT=5.0. THE FT IS BASED ON THE DT.

I. ADDL POSITIONS

NIL


...LEE

[cycloneye]

Hurricane Fernanda Discussion Number 11
NWS National Hurricane Center Miami FL EP072023
1100 PM HST Mon Aug 14 2023

Fernanda continues to show signs of weakening this evening, with the
once-visible and distinct eye from earlier today having vanished
and now cloud filled. Microwave passes from this evening depict that
the inner core of Fernanda has started to lose its well-defined
structure. This is reflected in the recent infrared satellite trends
showing the ring of cold cloud tops becoming less organized, and
not as tightly wrapped around the center. Subjective final-T Dvorak
numbers from TAFB and SAB for this advisory were T5.5/T4.5,
respectively. CIMMS ADT and AiDT estimates have started
to drop as well, and lie between the TAFB and SAB estimates. Given
the decline in satellite appearance, and using a blend of the
satellite estimates, the initial intensity for this advisory is
lowered to 95 kt.

The hurricane is being steered by a weak mid-level ridge with a
generally west-northwest to westward motion expected throughout the
period. The hurricane will begin to gradually increase in forward
speed over the next several days, as the aforementioned mid-level
ridge strengthens and builds westward. The official track forecast
is similar to the previous forecast, and the track remains close to
both the simple and corrected consensus model guidance.

Fernanda is moving into a less favorable environment, which is
expected to cause fairly quick weakening. Southerly mid-level
vertical wind shear is starting to increase over the cyclone, and
will increase to 15 to 20 kt. The system is also moving into a
fairly stable, and much drier airmass, with mid-level relative
humidity values plummeting to below 40 percent in about 24 hours.
In addition, sea surface temperatures also begin to rapidly cool
in 24 to 36 hours. Given these conditions, simulated satellite
imagery from both the GFS and ECMWF show the system void of most of
its convection in about 60h. This is now reflected in the latest
NHC intensity forecast, which shows a little faster weakening
trend, and the system now becoming post-tropical at 60 hours.


FORECAST POSITIONS AND MAX WINDS

INIT 15/0900Z 16.9N 120.7W 95 KT 110 MPH
12H 15/1800Z 17.3N 122.3W 85 KT 100 MPH
24H 16/0600Z 17.7N 124.7W 65 KT 75 MPH
36H 16/1800Z 17.9N 127.3W 50 KT 60 MPH
48H 17/0600Z 18.0N 130.0W 40 KT 45 MPH
60H 17/1800Z 18.2N 132.8W 35 KT 40 MPH...POST-TROPICAL
72H 18/0600Z 18.3N 135.9W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 19/0600Z 18.5N 142.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 20/0600Z 18.4N 148.5W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Kelly/Berg

[cycloneye]

EP, 07, 2023081512, , BEST, 0, 169N, 1212W, 95, 967, HU

[cycloneye]

Hurricane Fernanda Discussion Number 12
NWS National Hurricane Center Miami FL EP072023
500 AM HST Tue Aug 15 2023

Recent satellite imagery shows that Fernanda has not changed much in
appearance and a possible ragged eye has appeared in the last few
hours. Earlier microwave passes indicate that the hurricane still
has a well-defined center with concentric eyewalls. Subjective
Dvorak estimates from SAB and TAFB range from 77 kt to 102 kt. CIMSS
ADT and AiDT estimates are 92 kt and 87 kt, respectively. Thus, the
initial intensity is held at 95 kt for this advisory.

Fernanda is moving west-northwestward at 10 kt. There has been
little change to the track forecast since the last advisory. The
hurricane is moving near the southeast periphery of a weak mid-level
ridge. A general west-northwest to westward motion is forecast over
the next several days with a slight increase in forward speed. The
official track forecast has been nudged slightly south compared to
the previous prediction, and the track remains close to the various
consensus model predictions.

The hurricane is heading into a drier airmass and expected to
cross the 26C isotherm in about 24 hours. Also, statistical models
indicate that Fernanda is experiencing moderate southeasterly wind
shear. Therefore, continued weakening is expected through the
forecast period. Simulated satellite imagery from global models
suggest that most of the convection will collapse in about 24 to 36
hours and the system will be devoid of convection in about 60
hours. Fernanda is still forecast to become a post-tropical cyclone
at 60 hours.


FORECAST POSITIONS AND MAX WINDS

INIT 15/1500Z 17.0N 121.8W 95 KT 110 MPH
12H 16/0000Z 17.3N 123.5W 80 KT 90 MPH
24H 16/1200Z 17.5N 126.0W 65 KT 75 MPH
36H 17/0000Z 17.6N 128.6W 50 KT 60 MPH
48H 17/1200Z 17.8N 131.4W 40 KT 45 MPH
60H 18/0000Z 18.0N 134.3W 35 KT 40 MPH...POST-TROPICAL
72H 18/1200Z 18.1N 137.4W 30 KT 35 MPH...POST-TROP/REMNT LOW
96H 19/1200Z 18.3N 143.8W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 20/1200Z 18.2N 149.5W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Delgado/Bucci

[Sciencerocks]