EPAC: MAX - Remnants - Discussion

[Yellow Evan]

No idea why the NHC is saying it isn’t organized enough.

[Sciencerocks]

 https://twitter.com/VortixWx/status/1710853158044357004

[cycloneye]

BULLETIN
Potential Tropical Cyclone Sixteen-E Advisory Number 2
NWS National Hurricane Center Miami FL EP162023
400 AM CDT Sun Oct 08 2023

...DISTURBANCE LIKELY TO BECOME A TROPICAL STORM LATE TODAY...


SUMMARY OF 400 AM CDT...0900 UTC...INFORMATION
----------------------------------------------
LOCATION...14.5N 100.7W
ABOUT 230 MI...370 KM SSE OF ZIHUATANEJO MEXICO
MAXIMUM SUSTAINED WINDS...30 MPH...45 KM/H
PRESENT MOVEMENT...NW OR 315 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY:

None

SUMMARY OF WATCHES AND WARNINGS IN EFFECT:

A Tropical Storm Watch is in effect for...
* Acapulco to Punta San Telmo




Potential Tropical Cyclone Sixteen-E Discussion Number 2
NWS National Hurricane Center Miami FL EP162023
400 AM CDT Sun Oct 08 2023

This system has become a bit better organized since the last
advisory with increased convection near the cloud system center.
Still, there's not much curvature to the thunderstorm activity and
no clear signs that the system has become a tropical cyclone,
although it is closer than yesterday. So the system will remain
a potential tropical cyclone, and the initial wind speed is held at
25 kt, consistent with earlier ship data.

Much of this forecast is based on the previous NHC prediction since
there hasn't been a lot of in situ or microwave data overnight.
The initial motion estimate remains northwest at 6 kt. The system
is forecast to turn north-northwestward late today between a
mid-level ridge to its east and Tropical Storm Lidia to its west.
This motion should bring the center of the system near the southern
coast of Mexico in about 36-48 hours. The GFS seems
unrealistically fast with landfall in less than 24 hours given the
flow regime. Only a small adjustment to the left was made to the
previous forecast, near but slower than the consensus aids.

The disturbance has some chance to intensify over very warm waters
in moderate shear conditions. Model guidance has generally come
down, however, but this appears to be due to the GFS-based
guidance having too fast of a forward speed, which limits the
system's time over water, rather than a change in the near-term
environment. Little change was made to the previous forecast, though
this prediction is now on the higher side of the guidance envelope.

Key Messages:

1. The disturbance is expected to become a tropical storm before it
approaches the coast of southern Mexico on Monday. A tropical storm
watch remains in effect, and tropical storm warnings could be
required later today for a portion of the coast of southern Mexico.

2. Heavy rains from this system will likely produce flash and urban
flooding, along with possible mudslides in areas of higher terrain
across the states of Guerrero and Michoacan.


FORECAST POSITIONS AND MAX WINDS

INIT 08/0900Z 14.5N 100.7W 25 KT 30 MPH...POTENTIAL TROP CYCLONE
12H 08/1800Z 15.3N 101.2W 30 KT 35 MPH...TROPICAL CYCLONE
24H 09/0600Z 16.1N 101.5W 35 KT 40 MPH
36H 09/1800Z 16.9N 101.6W 45 KT 50 MPH
48H 10/0600Z 17.9N 101.6W 40 KT 45 MPH...INLAND
60H 10/1800Z 19.0N 101.5W 25 KT 30 MPH...POST-TROP/INLAND
72H 11/0600Z...DISSIPATED

[Sciencerocks]

[Sciencerocks]

[cycloneye]

Potential Tropical Cyclone Sixteen-E Discussion Number 3
NWS National Hurricane Center Miami FL EP162023
1000 AM CDT Sun Oct 08 2023

The system appears to be getting slowly better organized this
morning, though it remains unclear if a well-defined center has
formed. An SSMIS pass at 1110 UTC revealed a decent curved
convective band to the northwest of the best low-level turning, but
there is a lack of clear evidence of a tighter low-level circulation
on the low-level 37 GHz channel. First-light visible images on the
1-minute GOES-18 meso-sector also remain unclear on the circulation
definition. Thus, the system remains a potential tropical cyclone,
but given the improvement in banding the initial intensity was
raised to 30 kt, a bit higher than the TAFB and SAB Dvorak
estimates.

First-light visible imagery suggests the best position of the system
right now is just a little north and west of overnight estimate,
resulting in a slow northwest motion at 320/4 kt. The overall track
reasoning remains unchanged, as the system is expected to move
north-northwestward or northward over the next 24-36 h, in between a
mid-level ridge centered to its east over the northwest Caribbean,
and Tropical Storm Lidia located to its west. This motion should
bring the system inland over Mexico just beyond 36 h from now.
However, notable differences in the timing of landfall between the
guidance remain. The GFS model, in addition to the
hurricane-regional models based on the GFS initial conditions
(HWRF, HMON, HAFS-A/B) continue to be much faster than other global
model guidance such as the ECMWF and CMC. This disagreement is
likely at least partially related to the fact the disturbance does
not yet have a well-defined center, and may potentially form further
north closer to land. For now, the NHC track forecast leans towards
the slower solutions, but has shifted a bit east compared to the
previous track, and is a little slower than the consensus aid TVCE.

Given the gradually improving structure, the system is expected to
become a tropical cyclone soon, and most of the intensity guidance
suggest continued intensification up till landfall. The NHC
intensity forecast continues to show a peak intensity of 45 kt near
landfall, which is on the high end of the intensity guidance that
appears biased by the GFS and its hurricane-regional models that
bring the system inland faster than shown here. It is notable that
the ECMWF and CMC show a stronger tropical cyclone than the NHC
forecast, mainly because they spend a longer period of time
offshore.

Based on the latest forecast showing the system near landfall in
36 h, the government of Mexico has upgraded the area previously
under a Tropical Storm Watch to a Warning.

Key Messages:

1. The disturbance is expected to become a tropical storm before it
approaches the coast of southern Mexico on Monday. A tropical storm
warning is now in effect for a portion of the coast of southern
Mexico.

2. Heavy rains from this system will likely produce flash and urban
flooding, along with possible mudslides in areas of higher terrain
across the states of Guerrero, Michoacan and coastal sections of
western Oaxaca.


FORECAST POSITIONS AND MAX WINDS

INIT 08/1500Z 15.0N 101.1W 30 KT 35 MPH...POTENTIAL TROP CYCLONE
12H 09/0000Z 15.5N 101.2W 35 KT 40 MPH...TROPICAL CYCLONE
24H 09/1200Z 16.2N 101.3W 40 KT 45 MPH
36H 10/0000Z 17.1N 101.4W 45 KT 50 MPH
48H 10/1200Z 18.0N 101.1W 30 KT 35 MPH...INLAND
60H 11/0000Z...DISSIPATED

[cycloneye]

TD.

EP, 16, 2023100818, , BEST, 0, 157N, 1016W, 30, 1005, TD

[Sciencerocks]

[cycloneye]

Tropical Depression Sixteen-E Discussion Number 4
NWS National Hurricane Center Miami FL EP162023
400 PM CDT Sun Oct 08 2023

Since the prior advisory, 1-minute visible images from the GOES-18
mesosector have been quite helpful in showing that the system we
have been monitoring just south of Zihuatanejo has developed a
well-defined circulation located a bit farther northwest of previous
estimations. This circulation was farther supported by a 1702 UTC
GMI pass which showed tightly curved bands wrapping most of the way
around this apparent center on the 37 GHz channel. Thus, the system
now can be considered a tropical depression, and the initial
intensity is 30 kt for this advisory, which is in between the
T1.5/25-kt estimates from TAFB and SAB versus 35-kt from the D-PRINT
estimate from UW-CIMSS.

Now that the center has become well-defined, it has formed farther
northwest than earlier estimated. This should not be considered an
acceleration in the short-term motion though, which still appears to
be slowly off to the north-northwest at 340/4 kt. This slow motion
is expected to continue with a gradual turn northward and then
north-northeastward as the system is steered around mid-level
ridging located east of it over the Caribbean Sea in addition to the
outer circulation of Tropical Storm Lidia to its west. Given the
farther northwestward initial position, the timing for landfall has
moved up a bit to between 24-36 h, by tomorrow evening. There
continues to be some spread in this landfall timing, with the GFS
remaining on the faster end versus the slower CMC and ECMWF
solutions. The latest NHC track forecast more or less splits the
difference, which is close to both the TVCE and HCCA consensus aids,
though most of the guidance now agrees the system should be inland
after 36 hours.

Intensification is still forecast up until the system moves inland
over Mexico. With landfall now between 24-36 h, there might not be
quite as much time for intensification as previously expected. With
that said, both the raw model output from the ECMWF and CMC suggest
significant intensification over the next 24 hours before the
depression makes landfall, and out of respect of these models, a
peak intensity of 45 kt continues to be shown just before landfall.
This is on the higher end of the intensity guidance envelope. The
system should quickly weaken after moving inland, ultimately
dissipating over the higher rugged terrain of south-central Mexico
by 48 hours. However, the significant up-slope flow that will result
is anticipated to continue producing very heavy rainfall into
Tuesday over coastal and inland Mexico as the cyclone and its
remnants move farther inland.


Key Messages:

1. The depression is expected to become a tropical storm before it
approaches the coast of southern Mexico on Monday. A Tropical Storm
Warning remains in effect for a portion of the coast of southern
Mexico.

2. Heavy rains from this system will likely produce flash and urban
flooding, along with possible mudslides in areas of higher terrain
across the states of Guerrero, Michoacan and coastal sections of
western Oaxaca.


FORECAST POSITIONS AND MAX WINDS

INIT 08/2100Z 15.9N 101.7W 30 KT 35 MPH
12H 09/0600Z 16.5N 101.8W 35 KT 40 MPH
24H 09/1800Z 17.2N 101.7W 45 KT 50 MPH
36H 10/0600Z 18.0N 101.4W 30 KT 35 MPH...INLAND
48H 10/1800Z...DISSIPATED

[Yellow Evan]

Not the right core structure for RI up into landfall probably especially in moderate shear.

[cycloneye]

Hello Max.

EP, 16, 2023100900, , BEST, 0, 161N, 1019W, 35, 1001, TS

[Sciencerocks]

[cycloneye]

Tropical Storm Max Discussion Number 5
NWS National Hurricane Center Miami FL EP162023
1000 PM CDT Sun Oct 08 2023

Tropical Depression Sixteen-E has strengthened into Tropical Storm
Max. Visible and infrared satellite imagery this evening indicates
that the system maintains a well-defined center, which was further
confirmed by recent AMSR-2 and SSMIS microwave passes.
Additionally, deep convection, which was only loosely organized
over a large area for most of the day, has increased in intensity
tonight in a concentrated area to the southwest of the center.
Subjective intensity estimates from TAFB and SAB have increased, and
objective estimates from UW-CIMSS also support an increase in
intensity since the prior advisory. Thus, the initial intensity for
this advisory is set at 35 kt.

Max is continuing to move north-northwestward at 340/5 kt. The
storm is expected to gradually turn northward and eventually
north-northeastward tonight and tomorrow. The primary steering
influences are a mid-level ridge over the Caribbean Sea to the
storm's east, and Tropical Storm Lidia to its west. Max is expected
to make landfall in the next 24 h or so, although some uncertainty
remains in the exact timing and location, with global models
differing in the forward speed. Regardless of the exact timing and
landfall location, tropical storm impacts are expected to occur far
from the landfall location. The current NHC forecast represents a
blend of the TVCN and HCCA consensus aids, and it is slightly west
of the prior forecast.

The current intensity forecast indicates intensification prior to
landfall in Mexico. Some of the dynamical models indicate
intensification in the next 12-24 h, but with limited time
before landfall and moderate easterly wind shear that will persist
through tomorrow, the system is expected to remain a tropical
storm at landfall. After landfall, Max is forecast to weaken rapidly
as it interacts with the mountainous terrain of southern Mexico.
However, this interaction of the storm's circulation with the
terrain is likely to result in heavy rainfall as the storm
dissipates and its remnants continue moving inland on Tuesday. The
NHC intensity forecast is similar to the prior forecast and is on
the high end of the guidance envelope.


Key Messages:

1. Max is forecast to bring tropical storm conditions to portions
of the southern coast of Mexico on Monday where a Tropical Storm
Warning remains in effect.

2. Heavy rains from this system will likely produce flash and urban
flooding, along with possible mudslides in areas of higher terrain
across the states of Guerrero, Michoacan and coastal sections of
western Oaxaca.


FORECAST POSITIONS AND MAX WINDS

INIT 09/0300Z 16.3N 101.9W 35 KT 40 MPH
12H 09/1200Z 17.0N 102.0W 45 KT 50 MPH
24H 10/0000Z 17.8N 101.9W 40 KT 45 MPH
36H 10/1200Z 18.6N 101.6W 20 KT 25 MPH...INLAND
48H 11/0000Z...DISSIPATED

[cycloneye]

Tropical Storm Max Discussion Number 6
NWS National Hurricane Center Miami FL EP162023
400 AM CDT Mon Oct 09 2023

Satellite images indicate that Max has become better organized,
with a large burst of convection near the center and a well-defined
banding feature in the southern semicircle of the storm. Recent
scatterometer data indicates maximum winds of 40-45 kt, so the
initial wind speed is set to 45 kt on this advisory. Further
strengthening is possible in a conducive environment before Max
makes landfall later today. Rapid weakening is then anticipated
this evening over the high terrain of Mexico. The new forecast is
similar to the previous one, but a bit higher due to the initial
intensity.

Max has turned northward or 010/5 kt this morning, and this general
motion is forecast until landfall later today. The biggest
change on this advisory is that the landfall of Max is expected to
be sooner and farther east than before, which is consistent with
recent trends and the latest model solutions. Max should dissipate
over southern Mexico early on Tuesday.

Key Messages:

1. Max is forecast to continue bringing tropical storm conditions
today to portions of the southern coast of Mexico where a Tropical
Storm Warning remains in effect.

2. Heavy rains from this system will likely produce flash and urban
flooding, along with possible mudslides in areas of higher terrain
across the states of Guerrero and Michoacan.


FORECAST POSITIONS AND MAX WINDS

INIT 09/0900Z 16.8N 101.5W 45 KT 50 MPH
12H 09/1800Z 17.5N 101.4W 50 KT 60 MPH...NEAR COAST
24H 10/0600Z 18.7N 101.2W 30 KT 35 MPH...INLAND
36H 10/1800Z...DISSIPATED

[Sciencerocks]

[Yellow Evan]

Good attempt at developing an inner core right before landfall - would be a formidable hurricane with another day.

[cycloneye]

Tropical Storm Max Discussion Number 7
NWS National Hurricane Center Miami FL EP162023
1000 AM CDT Mon Oct 09 2023

Max has continued to intensify this morning as it nears landfall in
Mexico. The overnight convection appears to have wrapped around the
center, with an earlier AMSR2 microwave pass showing a low-level
cyan ring on the 37 GHz channel, suggesting formative inner-core
features. Subjective Dvorak intensity estimates were T3.0/45 kt from
TAFB and T3.5/55 kt from SAB. The initial intensity was raised to 50
kt at 12 UTC, and that will remain the intensity for this advisory.
This value also is close to the latest UW CIMSS D-PRINT estimate.
While not shown in the forecast below, Max could intensify a little
more, and be near its max intensity at landfall, sometime in the
next 3-6 hours. However, rapid weakening should begin by this
evening as the surface circulation is quickly disrupted by the high
rugged terrain of Mexico, with dissipation likely by tomorrow.

Max appears to have started a north-northeastward motion this
morning, estimated at 030/4 kt. This motion is expected to continue
until the storm moves inland later this afternoon. As the storm
moves inland, the surface circulation will quickly become difficult
to track, though its mid-level remains and larger moisture plume
should push further inland into Mexico, even after the storm
dissipates by early on Tuesday.


Key Messages:

1. Max is forecast to continue bringing tropical storm conditions
today to portions of the southern coast of Mexico where a Tropical
Storm Warning remains in effect.

2. Heavy rains from this system will likely produce flash and urban
flooding, along with possible mudslides in areas of higher terrain
across the states of Guerrero and Michoacan.


FORECAST POSITIONS AND MAX WINDS

INIT 09/1500Z 17.1N 101.2W 50 KT 60 MPH
12H 10/0000Z 17.7N 100.9W 35 KT 40 MPH...INLAND
24H 10/1200Z...DISSIPATED

[ElectricStorm]

Looks like it's intensifying quickly right before landfall, just like 2017 Max. Might not have enough time to get to hurricane strength though.

[Sciencerocks]

I'd go 60 knts with the possibility of a hurricane at landfall

[cycloneye]

BULLETIN
Tropical Storm Max Intermediate Advisory Number 7A
NWS National Hurricane Center Miami FL EP162023
100 PM CDT Mon Oct 09 2023

...MAX MAKING LANDFALL IN MEXICO...
...TROPICAL STORM CONDITIONS AND HEAVY RAINFALL EXPECTED THIS
AFTERNOON...


SUMMARY OF 100 PM CDT...1800 UTC...INFORMATION
----------------------------------------------
LOCATION...17.4N 101.2W
ABOUT 30 MI...50 KM SE OF ZIHUATANEJO MEXICO
MAXIMUM SUSTAINED WINDS...60 MPH...95 KM/H
PRESENT MOVEMENT...NNE OR 30 DEGREES AT 5 MPH...7 KM/H
MINIMUM CENTRAL PRESSURE...996 MB...29.42 INCHES