EPAC: MARIE - Post-Tropical

[cycloneye]

94E INVEST 200927 1800 12.5N 103.7W EPAC 25 1009

[aspen]

I will be very, very surprised if this Marie even makes it to hurricane status. There’s no way it’ll be able to get close to the intensity of the 2014 version.

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 PM PDT Sun Sep 27 2020

For the eastern North Pacific...east of 140 degrees west longitude:

1. A well-defined low pressure system located a few hundred miles south
of the southwestern coast of Mexico is producing a large area of
disorganized cloudiness and thunderstorms. The disturbance is
forecast to move generally westward for the next several days, and
environmental conditions are expected to gradually become more
conducive for a tropical depression to form around midweek.
* Formation chance through 48 hours...medium...40 percent.
* Formation chance through 5 days...high...90 percent.

Forecaster Stewart

[ElectricStorm]

This one seems further south than many of the recent storms in the EPAC. Maybe that will give it a chance to become something more than yet another boring TS to track

[Yellow Evan]

I will be very, very surprised if this Marie even makes it to hurricane status. There’s no way it’ll be able to get close to the intensity of the 2014 version.

Not sure I agree. Background state is favorable though this needs to not gain latitude as it tracks west.

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 AM PDT Mon Sep 28 2020

For the eastern North Pacific...east of 140 degrees west longitude:

1. A broad area of disturbed weather is located a few hundred miles
south of the southwestern coast of Mexico. Shower and thunderstorm
activity associated with a small low embedded within this area has
decreased since yesterday. However, environmental conditions are
expected to gradually become more conducive for development and a
tropical depression will likely form within the next two or three
days. The disturbance is forecast to move generally westward for the
next several days and then turn west-northwestward by the weekend.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...90 percent.

Forecaster Zelinsky

[Yellow Evan]

28/1730 UTC 13.7N 105.4W T1.0/1.0 94E -- East Pacific

[Yellow Evan]

000
ABPZ20 KNHC 281739
TWOEP

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
1100 AM PDT Mon Sep 28 2020

For the eastern North Pacific...east of 140 degrees west longitude:

Showers and thunderstorms associated with an area of low pressure
located a few hundred miles south of the southwestern coast of
Mexico have increased during the past few hours and have recently
begun to show signs of organization. Additional development is
expected and a tropical depression will likely form during the next
couple of days. The disturbance is forecast to move generally
westward for the next several days and then turn west-northwestward
by the weekend.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...90 percent.

$$
Forecaster Zelinsky

[cycloneye]

Tropical Weather Outlook
NWS National Hurricane Center Miami FL
500 PM PDT Mon Sep 28 2020

For the eastern North Pacific...east of 140 degrees west longitude:

1. Showers and thunderstorms continue to become better organized in
association with a low pressure system located a few hundred miles
south-southwest of the southwestern coast of Mexico. Environmental
conditions are forecast to steadily become more conducive, and a
tropical depression will likely form later tonight or on Tuesday.
The low is expected to move generally westward for the next several
days, and then turn west-northwestward by the weekend.
* Formation chance through 48 hours...high...90 percent.
* Formation chance through 5 days...high...90 percent.

Forecaster Stewart

[aspen]

We might have TD18-E tonight, or at 5am at the latest.

[Yellow Evan]

28/2330 UTC 13.8N 105.8W T1.5/1.5 94E -- East Pacific

[Nancy Smar]

EP, 18, 2020092906, , BEST, 0, 131N, 1072W, 30, 1005, TD, 34, NEQ, 0, 0, 0, 0, 1009, 160, 60, 0, 0, E, 0, , 0, 0, EIGHTEEN, M, 0, , 0, 0, 0, 0, genesis-num, 033, TRANSITIONED, epC42020 to ep182020,

[cycloneye]

Tropical Depression Eighteen-E Discussion Number 1
NWS National Hurricane Center Miami FL EP182020
300 AM MDT Tue Sep 29 2020

A burst of deep convection that developed near the center of the
area of low pressure well southwest of the southwestern coast of
Mexico during the evening has persisted overnight. Microwave
imagery and a 0444 UTC ASCAT-C overpass indicated that the center
of the low re-formed within the area of deep convection and with
the overall increase in the organization of the system, advisories
are being initiated on the eighteen tropical depression of the 2020
eastern Pacific hurricane season. The scatterometer data revealed
peak winds of around 30 kt, and that is used as the advisory
intensity.

The depression is located over warm water and within an area of
light to moderate northeasterly shear, and these conditions are
expected to allow for steady strengthening over the next few days.
Although the SHIPS model guidance only shows a peak intensity
of 65-70 kt in 72-84 hours, the SHIPS rapid intensification index
indicates a 50 percent chance of a 65 kt increase in intensity over
the next 72 hours. In addition, the global models significantly
deepen the system over the next few days. On the basis of the
SHIP RI information and the global models, the NHC intensity
forecast is above the IVCN intensity consensus close to the more
aggressive HWRF and HCCA models. Late in the period, decreasing
SSTs and increasing vertical wind shear should result in weakening.

Given the recent re-formation of the center, the initial motion
estimate is a highly uncertain 275/9 kt. A deep-layer ridge
centered over the southwestern United States is expected to steer
the cyclone westward to west-northwestward during the next several
days. By the end of the forecast period, the cyclone will be
approaching the southwestern portion of the ridge allowing it to
turn northwesterly. Although there some model differences in
the predicted forward speed of the depression, the models are in
good agreement on the overall track forecast scenario. To account
for these forward speed differences, the NHC forecast is near the
middle of the guidance envelope close to the various consensus
aids.


FORECAST POSITIONS AND MAX WINDS

INIT 29/0900Z 13.2N 107.6W 30 KT 35 MPH
12H 29/1800Z 13.5N 109.0W 35 KT 40 MPH
24H 30/0600Z 14.2N 111.2W 45 KT 50 MPH
36H 30/1800Z 14.6N 114.3W 55 KT 65 MPH
48H 01/0600Z 14.8N 117.3W 65 KT 75 MPH
60H 01/1800Z 15.3N 119.9W 75 KT 85 MPH
72H 02/0600Z 16.2N 122.3W 85 KT 100 MPH
96H 03/0600Z 18.3N 126.2W 80 KT 90 MPH
120H 04/0600Z 20.5N 129.2W 60 KT 70 MPH

$$
Forecaster Brown

[aspen]

Surprisingly, the 12z best track has stayed at 30 kt, even though ADT and the experimental satellite estimate supports 35 kt TS Marie.

[ElectricStorm]

Looks like we may finally have something significant to track in the EPAC.

[cycloneye]

Tropical Depression Eighteen-E Discussion Number 2
NWS National Hurricane Center Miami FL EP182020
900 AM MDT Tue Sep 29 2020

The tropical cyclone is gradually becoming better organized, with a
Central Dense Overcast feature developing near/over the estimated
center. The system is experiencing moderate east-northeasterly
shear which is currently restricting upper-level outflow over the
eastern semicircle of the system. Dvorak classifications from TAFB
and SAB indicate that the cyclone's maximum winds are near 30 kt.
The dynamical guidance indicates that the shear will soon diminish,
and the atmospheric and oceanic environment is expected to be quite
conducive for strengthening during the next few days. The
official forecast shows steady intensification with the system
becoming a tropical storm by tonight and a hurricane within 72
hours. This is a little below the latest intensity model
consensus, which suggests that that the cyclone could be near major
hurricane status in about 72 hours.

The center is not easy to locate at this time, so the initial motion
estimate of 280/9 kt is more uncertain than usual. A strengthening
subtropical ridge to the north of the tropical cyclone should
maintain a westward or west-northwestward motion at an increased
forward speed for the next 72 hours or so. In 4-5 days, a weakness
in the ridge in the vicinity of 130W longitude should cause the
system to turn toward the northwest. The official track forecast
is a little north and northeast of the latest model consensus.

The dynamical guidance shows an expanding wind field with the
tropical cyclone, and the official wind radii forecasts, especially
beyond 2 days, are in close agreement with the consensus wind radii
forecast technique, RVCN.


FORECAST POSITIONS AND MAX WINDS

INIT 29/1500Z 13.3N 108.5W 30 KT 35 MPH
12H 30/0000Z 13.8N 110.4W 35 KT 40 MPH
24H 30/1200Z 14.4N 113.2W 45 KT 50 MPH
36H 01/0000Z 14.6N 116.2W 60 KT 70 MPH
48H 01/1200Z 14.7N 119.0W 70 KT 80 MPH
60H 02/0000Z 15.4N 121.7W 80 KT 90 MPH
72H 02/1200Z 16.4N 124.0W 90 KT 105 MPH
96H 03/1200Z 18.9N 127.6W 85 KT 100 MPH
120H 04/1200Z 21.0N 130.5W 65 KT 75 MPH

$$
Forecaster Pasch

[aspen]

18z best track upgrades this to TS Marie.

[cycloneye]

18E MARIE 200929 1800 13.6N 108.8W EPAC 35 1005

[cycloneye]

Tropical Storm Marie Discussion Number 3
NWS National Hurricane Center Miami FL EP182020
300 PM MDT Tue Sep 29 2020

A WindSat microwave image from earlier this morning indicated that
the tropical cyclone's low-level circulation was becoming better
defined, with perhaps the formative stage of a cyan ring seen in the
37-GHz channel. Visible images also show the center tucked just
beneath recent bursts of deep convection, and Dvorak estimates have
risen to T2.0 and T2.5 from TAFB and SAB, respectively. These data,
along with ambiguity analyses of recent ASCAT-B and -C scatterometer
passes, indicate the depression has strengthened to Tropical Storm
Marie with maximum winds of 35 kt.

Marie's future track is probably the most straightforward part of
the forecast. A mid-tropospheric high anchored over the
southwestern United States is steering Marie westward with an
initial motion of 275/10 kt. This high will remain the main driver,
forcing the cyclone westward or west-northwestward for the next 3
days. By days 4 and 5, Marie is likely to reach a break in the
ridge and should slow down a bit and turn toward the northwest.
There are no notable outliers among the track guidance, and the
small spread among the models yields higher-than-normal confidence
in the track forecast. The new NHC forecast is very similar to the
previous prediction, and is close to the TVCE and HCCA consensus
aids.

The intensity forecast is a little more challenging, but mostly
because a good proportion of the guidance suggests that Marie will
intensify significantly during the next few days. Relatively low
deep-layer shear, warm ocean waters, and favorable upper-level
divergence all favor strengthening, and several of the various
SHIPS Rapid Intensification thresholds are several times higher
than their climatological means. In addition, all of the dynamical
models, the consensus aids, and the GFS-based SHIPS model bring
Marie to hurricane strength within 24 hours. Given these signals,
the NHC intensity forecast has been raised from the previous one
and lies near or just below the intensity consensus in order to
maintain some continuity. But given what is shown by some of the
better-performing intensity models, I would not be surprised if
subsequent forecasts show a faster rate of intensification or
a higher peak intensity. Weakening is expected by days 4 and 5 due
to cooler waters and increasing southwesterly shear.

Marie's 12-ft sea radii are larger than would be expected for a
small, just-developing tropical storm due to a large fetch of
southerly swell originating from the Southern Hemisphere.


FORECAST POSITIONS AND MAX WINDS

INIT 29/2100Z 13.6N 109.5W 35 KT 40 MPH
12H 30/0600Z 13.9N 111.6W 45 KT 50 MPH
24H 30/1800Z 14.6N 114.5W 60 KT 70 MPH
36H 01/0600Z 14.9N 117.5W 75 KT 85 MPH
48H 01/1800Z 15.3N 120.3W 90 KT 105 MPH
60H 02/0600Z 16.0N 122.7W 100 KT 115 MPH
72H 02/1800Z 17.2N 124.9W 100 KT 115 MPH
96H 03/1800Z 19.6N 128.5W 85 KT 100 MPH
120H 04/1800Z 21.4N 131.6W 60 KT 70 MPH

$$
Forecaster Berg

[aspen]

Now forecast to become a major! However, knowing how badly the EPac has performed this year, there’s a decent chance Marie barely makes it to hurricane status.