EPAC: LOWELL - Post-Tropical

[Extratropical94]

93E INVEST 200919 1800 15.0N 105.0W EPAC 25 1010

Lowell in the making?

A broad area of low pressure has formed in association with an area
of disturbed weather located a few hundred miles southwest of the
coast of southwestern Mexico. The showers and thunderstorms have
also increased and become more concentrated today. Environmental
conditions appear conducive for development, and a tropical
depression is likely to form early next week while the system moves
west-northwestward at around 10 mph, away from the coast of Mexico.
* Formation chance through 48 hours...low...30 percent.
* Formation chance through 5 days...high...70 percent.

[AnnularCane]

That's weird, I just checked there not long ago for the heck of it and there was nothing.

[Extratropical94]

Showers and thunderstorms associated with a broad area of low
pressure located a couple of hundred miles south-southwest of
Manzanillo, Mexico, are showing signs of organization.
Environmental conditions are forecast to be conducive for additional
development, and a tropical depression is expected to form early
next week while the system moves west-northwestward at about 10 mph,
away from the coast of Mexico.
* Formation chance through 48 hours...high...70 percent.
* Formation chance through 5 days...high...90 percent.

[Extratropical94]

Showers and thunderstorms associated with a broad area of low
pressure located a couple of hundred miles south-southwest of
Manzanillo, Mexico, continue to show signs of organization.
Environmental conditions are forecast to be conducive for additional
development, and a tropical depression is expected to form
during the next day or so while the system moves west-northwestward
at about 10 mph, away from the coast of Mexico.
* Formation chance through 48 hours...high...80 percent.
* Formation chance through 5 days...high...90 percent.

[aspen]

Up to 100/100! This put itself together really quickly.

[hurricanes1234]

Lol I'm pretty sure this'll just struggle or fall apart as quickly as it went up to a 100% chance.

[Yellow Evan]

Satellite images indicate that the circulation associated with the
low pressure system centered about 350 miles southwest of
Manzanillo, Mexico, has become better defined today, with
thunderstorm activity still showing signs of organization. If this
trend continues, advisories could be initiated on a tropical
depression later today or tonight, and environmental conditions are
forecast to be conducive for additional development while the system
moves west-northwestward at about 10 mph.
* Formation chance through 48 hours...high...near 100 percent.
* Formation chance through 5 days...high...near 100 percent.

[Yellow Evan]

20/1730 UTC 14.9N 108.7W T2.0/2.0 93E -- East Pacific

[Extratropical94]

Tropical Depression Seventeen-E Discussion Number 1
NWS National Hurricane Center Miami FL EP172020
300 PM MDT Sun Sep 20 2020

The area of disturbed weather several hundred miles south of the
southern tip of Baja California has developed enough organized deep
convection and a well-enough defined center to declare it a tropical
cyclone. This is supported by subjective Dvorak classifications
from both SAB and TAFB with an initial intensity of 25 kt. The
initial motion is an uncertain 275 degrees at 9 kt.

As the system should be moving over warm 29C SSTs, encountering
moist mid-level humidities, and experiencing low to moderate amounts
of tropospheric vertical shear, steady intensification is expected
through the next three days. Around days four and five, the tropical
cyclone should encounter both drier air and cooler SSTs, likely
curtailing any further development and leading toward slow
weakening. The intensity forecast is between the bullish dynamical
models calling for a peak at a Category 1 hurricane in about three
days, and the bearish statistical guidance suggesting a moderate to
high-end tropical storm at the system's peak.

The track models are in much better agreement with all suggesting a
turn toward the west-northwest at a slightly faster forward speed
for the next three days, under the steering influence of a narrow
deep-layer ridge north of the system. By day four, an amplifying
ridge north of the tropical cyclone should turn it back toward the
west again. The track forecast is based upon the HCCA corrected
consensus technique.

FORECAST POSITIONS AND MAX WINDS

INIT 20/2100Z 15.8N 109.1W 25 KT 30 MPH
12H 21/0600Z 16.2N 110.5W 30 KT 35 MPH
24H 21/1800Z 17.3N 112.3W 35 KT 40 MPH
36H 22/0600Z 18.5N 114.5W 40 KT 45 MPH
48H 22/1800Z 19.3N 117.0W 45 KT 50 MPH
60H 23/0600Z 19.7N 119.0W 55 KT 65 MPH
72H 23/1800Z 20.1N 120.7W 60 KT 70 MPH
96H 24/1800Z 20.5N 124.0W 55 KT 65 MPH
120H 25/1800Z 20.5N 127.0W 50 KT 60 MPH

[ElectricStorm]

This one actually has a shot to become a hurricane.

[Kingarabian]

Too troughy over the NE Pacific this season. So systems are forming further north. With the La Nina in place there's just very little room for advanced TC development.

[Astromanía]

Sad that this is the most interesting cyclone since Genevieve in EPAC...

[Yellow Evan]

CZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Tropical Depression Seventeen-E Discussion Number 2
NWS National Hurricane Center Miami FL EP172020
900 PM MDT Sun Sep 20 2020

Last few visible images showed that the depression's surface
circulation remains poorly organized with a small swirl of clouds
displaced just to the north of the deep convective mass. The
initial intensity is held at 25 kt based on the unchanged
subjective intensity estimates from TAFB and SAB.

The statistical-dynamical intensity guidance and the skilled
consensus models all point to steady intensification through day 3.
Toward the end of the period, the tropical cyclone should encounter
an inhibiting dry stable air mass and cooler oceanic surface
temperatures, which should lead to a gradual weakening trend. The
NHC intensity forecast shows a peak intensity just under hurricane
strength on Wednesday and is just below the HCCA intensity
consensus and close to the Decay SHIPS.

The initial motion is estimated to be west-northwestward at 6 kt,
and this motion is predicted to continue through Wednesday. The
subtropical ridge currently steering the cyclone is forecast to
build farther westward over the tropical eastern Pacific which
should induce a westward turn toward the end of the week. The NHC
forecast is basically an update of the previous one and based on
the various consensus aids.


FORECAST POSITIONS AND MAX WINDS

INIT 21/0300Z 16.1N 109.3W 25 KT 30 MPH
12H 21/1200Z 16.7N 110.8W 30 KT 35 MPH
24H 22/0000Z 17.9N 112.8W 35 KT 40 MPH
36H 22/1200Z 18.9N 115.2W 40 KT 45 MPH
48H 23/0000Z 19.6N 117.4W 50 KT 60 MPH
60H 23/1200Z 20.0N 119.2W 60 KT 70 MPH
72H 24/0000Z 20.3N 120.8W 60 KT 70 MPH
96H 25/0000Z 20.4N 123.7W 55 KT 65 MPH
120H 26/0000Z 20.7N 126.5W 50 KT 60 MPH

$$
Forecaster Roberts

NNNN

[Yellow Evan]

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Tropical Depression Seventeen-E Discussion Number 3
NWS National Hurricane Center Miami FL EP172020
300 AM MDT Mon Sep 21 2020

The depression has really gone downhill overnight. While a small
well-defined center probably still exists, a pair of ASCAT passes
between 4 and 5 UTC showed that the surface circulation of the
depression is generally elongated, with a large area of light and
variable winds where you would expect north and northwest winds.
Deep convection is displaced well to the west of the estimated
center position due to persistent easterly shear. The highest winds
in either ASCAT pass were just below 25 kt, so that remains the
intensity for this advisory.

The depression has apparently accelerated west-northwestward, with
an extremely uncertain motion estimate of 285/11 kt. A turn toward
the west is anticipated by Wednesday and extensive ridging to the
north will likely keep the cyclone heading generally westward
thereafter through the end of the forecast period. This track will
take the cyclone parallel to an SST gradient that will have
implications on the intensity forecast.

The poor organization of the depression suggests that any
strengthening will be slow to occur during the next day or two.
Moderate easterly shear will likely continue for at least another
couple days, but the cyclone could find itself in a quite favorable
upper-air environment in a few days. If it is located on the warm
side of the SST gradient, some strengthening is likely, though
surrounding dry air will likely be a limiting factor for rapid any
intensification. One model with a southern track, the HWRF, even
suggests it could become a hurricane later this week. If the system
moves a little farther north that currently forecast, little
strengthening will be likely and it could even become a remnant low
at some point during the next 5 days. The NHC intensity forecast is
similar to the previous one, but shows a slightly slower rate of
strengthening for the first three days.


FORECAST POSITIONS AND MAX WINDS

INIT 21/0900Z 16.6N 110.8W 25 KT 30 MPH
12H 21/1800Z 17.4N 112.5W 30 KT 35 MPH
24H 22/0600Z 18.5N 114.8W 35 KT 40 MPH
36H 22/1800Z 19.3N 116.9W 40 KT 45 MPH
48H 23/0600Z 19.9N 118.9W 50 KT 60 MPH
60H 23/1800Z 20.2N 120.6W 55 KT 65 MPH
72H 24/0600Z 20.4N 122.4W 60 KT 70 MPH
96H 25/0600Z 20.5N 125.5W 60 KT 70 MPH
120H 26/0600Z 20.5N 129.0W 55 KT 65 MPH

$$
Forecaster Zelinsky

[Yellow Evan]

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Tropical Depression Seventeen-E Discussion Number 4
NWS National Hurricane Center Miami FL EP172020
900 AM MDT Mon Sep 21 2020

Although the circulation still appears to be elongated, the
depression has become a little better organized during the past
several hours, with the low-level center closer to the large mass
of convection in the southwestern semicircle. Satellite intensity
estimates from TAFB and SAB are 30 kt, so the initial intensity is
nudged upward to 30 kt.

The initial motion is now 290/12. The depression is being steered
by a large low- to mid-level ridge to the north and northwest, and
this ridge is forecast to persist through the forecast period. The
track guidance shows that the system should continue west-
northwestward for about 36 h, followed by a westward motion through
120 h. The track guidance is very tightly clustered, and the new
forecast track is near the various consensus models.

Current indications are that the current easterly shear should
subside a little during the next 24-36 h, and this should allow the
system to become a tropical storm. As noted in the previous
advisory, the intensity after 36 h will be strongly dependent on
where the center is in relation to the strong sea surface
temperature gradient. The new intensity forecast is similar to the
previous forecast based on the forecast track keeping the
system over 25-26C water temperatures through 120 h. However, any
motion north of the forecast track would bring the center over
colder water and lead to a system weaker than forecast, while any
motion south of the track would keep it over warmer water and
possibly allow the cyclone to become a hurricane. As might have
guessed, this is a low confidence intensity forecast.


FORECAST POSITIONS AND MAX WINDS

INIT 21/1500Z 17.0N 112.0W 30 KT 35 MPH
12H 22/0000Z 17.8N 113.7W 35 KT 40 MPH
24H 22/1200Z 18.8N 115.9W 40 KT 45 MPH
36H 23/0000Z 19.5N 118.0W 45 KT 50 MPH
48H 23/1200Z 20.0N 119.9W 50 KT 60 MPH
60H 24/0000Z 20.3N 121.7W 55 KT 65 MPH
72H 24/1200Z 20.5N 123.4W 60 KT 70 MPH
96H 25/1200Z 20.5N 126.5W 60 KT 70 MPH
120H 26/1200Z 20.5N 130.5W 50 KT 60 MPH

$$
Forecaster Beven

[cycloneye]

17E LOWELL 200921 1800 17.3N 112.9W EPAC 40 1001

[cycloneye]

Tropical Storm Lowell Discussion Number 5
NWS National Hurricane Center Miami FL EP172020
300 PM MDT Mon Sep 21 2020

Tropical Depression Seventeen-E has continued to have a ragged
appearance in satellite imagery during the day. The circulation is
elongated, with the main center just northeast of a poorly organized
convective mass and a secondary vorticity maximum well to the
north-northeast near Socorro Island. However, recent scatterometer
data showed an area of 35-40 kt winds to the south and southeast of
the main center. Based on this, the depression is upgraded to
Tropical Storm Lowell with an initial intensity of 40 kt.

The initial motion is now 290/14 kt. There are no significant
changes in the track forecast philosophy, the track forecast
guidance, or the track forecast since the last advisory. Lowell is
being steered by a large low- to mid-level ridge to the north and
northwest, and this ridge is forecast to persist through the
forecast period. The track guidance shows that the system should
continue west-northwestward for about 36 h, followed by a westward
motion through 120 h. The track guidance is still very tightly
clustered, and the new forecast track is near the various consensus
models.

Lowell is still experiencing some easterly shear, which the models
suggest should abate some in the next 12 h or so. However, the
poor organization of the storm suggests it may take a while to
respond to the more favorable environment. Thus, the new intensity
forecast continues the trend of the old forecast in showing slow
strengthening for the first 36-48 h. After that time, the intensity
will be strongly dependent on where the center is in relation to the
strong sea-surface temperature gradient. Since the forecast track
is basically unchanged, the new intensity forecast has only minor
tweaks from the previous forecast based on the forecast track
keeping the system over 25-26C water temperatures through 120 h.
However, any motion north of the forecast track would bring the
center over colder water and lead to a system weaker than forecast,
while any motion south of the track would keep it over warmer water
and possibly allow the cyclone to become a hurricane. The intensity
forecast remains low confidence.


FORECAST POSITIONS AND MAX WINDS

INIT 21/2100Z 17.4N 113.6W 40 KT 45 MPH
12H 22/0600Z 18.3N 115.2W 45 KT 50 MPH
24H 22/1800Z 19.2N 117.5W 50 KT 60 MPH
36H 23/0600Z 19.8N 119.4W 55 KT 65 MPH
48H 23/1800Z 20.2N 121.1W 60 KT 70 MPH
60H 24/0600Z 20.5N 122.8W 60 KT 70 MPH
72H 24/1800Z 20.5N 124.4W 60 KT 70 MPH
96H 25/1800Z 20.5N 128.0W 60 KT 70 MPH
120H 26/1800Z 20.5N 131.5W 50 KT 60 MPH

$$
Forecaster Beven

[Kingarabian]

NHC has it @ as a 70MPH TS for 36 hours is a bit odd. It will likely reach hurricane status.

[ClarCari]

NHC has it @ as a 70MPH TS for 36 hours is a bit odd. It will likely reach hurricane status.

Welllllll so was Cristina

[cycloneye]

Tropical Storm Lowell Discussion Number 6
NWS National Hurricane Center Miami FL EP172020
900 PM MDT Mon Sep 21 2020

Lowell's satellite presentation has changed little during the past
several hours. Lowell remains a sheared tropical cyclone with a
few new bursts of deep convection evident to the west of the rather
poorly defined and exposed surface circulation center. The initial
intensity is held at 40 kt for this advisory and is in best
agreement with the various subjective and objective satellite
intensity estimates.

Modest northeasterly shear is still impinging over the eastern half
of the cyclone and this inhibiting factor should relax within the
next 12 hours or so. As a result, Lowell should strengthen with
time through the 48 to 60 hour period as the cyclone traverses warm
water and continues moving within a moist surrounding environment.
Through the remaining portion of the forecast, Lowell is expected to
enter a more stable and drier marine layer which should cause the
cyclone to gradual weaken. The NHC intensity forecast is close to
the NOAA HCCA consensus and the Decay SHIPS, and above the LGEM
which indicates very little change in strength during the next 5
days.

The initial motion is estimated to be westward, or 280/11 kt.
Low- to mid tropospheric easterly flow produced by a subtropical
ridge anchored to the north of Lowell should steer it in a
generally west-northwestward motion through Wednesday night.
Around the 60 hour period, a turn back toward the west is expected
as the aforementioned ridge builds farther west. The official
forecast is basically an update of the previous advisory and is
close to the HFIP Corrected Consensus Approach model.


FORECAST POSITIONS AND MAX WINDS

INIT 22/0300Z 17.7N 114.5W 40 KT 45 MPH
12H 22/1200Z 18.4N 116.2W 45 KT 50 MPH
24H 23/0000Z 19.0N 118.3W 50 KT 60 MPH
36H 23/1200Z 19.5N 120.1W 55 KT 65 MPH
48H 24/0000Z 19.9N 121.8W 60 KT 70 MPH
60H 24/1200Z 20.0N 123.4W 60 KT 70 MPH
72H 25/0000Z 20.0N 125.0W 60 KT 70 MPH
96H 26/0000Z 20.0N 128.4W 55 KT 65 MPH
120H 27/0000Z 20.1N 131.8W 45 KT 50 MPH

$$
Forecaster Roberts