EPAC: LOWELL - Post-Tropical

[Kingarabian]

As I was saying we typically see strong troughs late in the season. Very unusual.

And this could be bad for California because those deep troughs are usually meaningless since waters begin to cool later in the season.

A storm being picked up NE this early could live long (like Julio) and reach California.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[Yellow Evan]

As I was saying we typically see strong troughs late in the season. Very unusual.

And this could be bad for California because those deep troughs are usually meaningless since waters begin to cool later in the season.

A storm being picked up NE this early could live long (like Julio) and reach California.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

Statistically, we are in the latter half of the season. And I believe this low is a cut-of

It could be bad depending on how far east the cutoff ULL comes, which can draw up moisture from the trough. However, there is little agreement between the Euro and GFS here. Hence why the Euro favors a more northerly track.

SST's are crazy cold despite +PDO signal. Around 20-22C. Julio became a hurricane over 25-26C waters.

The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or storm2k.org. For official information, please refer to the NHC and NWS products.

[cycloneye]

TROPICAL DEPRESSION TWELVE-E DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122014
200 AM PDT MON AUG 18 2014

The cloud pattern of the depression has not changed significantly
during the last several hours. The cyclone has a large
circulation, with its associated wind field extending several
hundred miles across. Curved banding is mainly confined to the
western half of the system due to about 15 kt of east-northeasterly
shear. The latest Dvorak classifications continue to support an
initial wind speed estimate of 30 kt. Some strengthening is
likely during the next few days while the cyclone remains over warm
water, within a moist air mass, and in an environment of moderate
shear. The system is expected to move over cooler water and into a
more stable atmosphere by the end of the week, and that should
cause the cyclone to lose strength. The weakening process over
cold water could be slower than normal as large cyclones like this
one typically take longer to spin down.

The depression is moving westward at about 8 kt on the south side
of a subtropical ridge. This ridge is expected to shift eastward
and weaken while a trough deepens over California. This pattern
change should cause the tropical cyclone to make a gradual turn
toward the north during the next 2 to 3 days. Beyond that time, a
slight left turn is predicted as the trough lifts out. The NHC
track forecast is a little to the left and slower than the previous
one to come into better agreement with the latest guidance.

It is worth noting that while the official forecast is well
offshore of the southwestern United States, model guidance does
show a surge of moisture partly associated with this system
extending into that region late Wednesday and Thursday. Please
monitor products issued by your local National Weather Service
office for more details on a possible heavy rain threat.

FORECAST POSITIONS AND MAX WINDS

INIT 18/0900Z 16.0N 117.5W 30 KT 35 MPH
12H 18/1800Z 16.4N 118.6W 35 KT 40 MPH
24H 19/0600Z 17.0N 119.6W 45 KT 50 MPH
36H 19/1800Z 17.7N 120.2W 50 KT 60 MPH
48H 20/0600Z 18.4N 120.6W 50 KT 60 MPH
72H 21/0600Z 19.7N 120.9W 50 KT 60 MPH
96H 22/0600Z 22.2N 122.1W 45 KT 50 MPH
120H 23/0600Z 25.5N 124.5W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Cangialosi

[Yellow Evan]

EP, 12, 2014081812, , BEST, 0, 165N, 1174W, 30, 1005, TD, 34, NEQ, 0, 0, 0, 0, 1010, 210, 90, 0, 0, E, 0, , 0, 0, TWELVE, M,

[cycloneye]

TROPICAL DEPRESSION TWELVE-E DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122014
800 AM PDT MON AUG 18 2014

The unusually large depression, at least 800 nmi in diameter, has
changed little since the previous advisory. A 1047 UTC SSMI
microwave overpass indicated that the depression has a well-defined
but fully exposed low-level circulation center, with a smaller
secondary circulation located about 120 nmi east of the main center.
Deep convection has been unable to develop and persist near the main
low-level center, possibly due to the aforementioned secondary swirl
and modest east-northeasterly mid- to upper-level shear undercutting
the otherwise favorable outflow pattern. A blend of the TAFB, SAB,
and ADT satellite intensity estimates supports maintaining the
initial intensity at 30 kt.

Recent passive microwave fix data suggest that the depression has
turned toward the west-northwest and is now moving 290/07 kt. The
cyclone is expected to turn northwestward later today as the
depression moves around the southwestern periphery of a deep-layer
ridge located over the southwestern U.S. and northwestern Mexico. A
mid-latitude trough/low currently digging south-southeastward along
the U.S. west coast is expected to erode the ridge on Tuesday and
Wednesday, allowing the cyclone to move more northward. However, the
trough is forecast to shift eastward by late Wednesday, which will
allow the ridge to build back in to the north of the cyclone and
forcing it back on a northwesterly track toward colder water through
Days 4 and 5. The new forecast track is similar to the previous
advisory track, and lies in the middle of the NHC guidance envelope
and close to the consensus model TVCE.

The large circulation and associated radius of maximum winds, plus
modest easterly shear, are expected to hinder the intensification
process for the next 72 hours or so despite the favorable outflow
regime. After that, the system is forecast to move over sub-26C and
progressively cooler waters, which should induce slow weakening.
The intensity forecast closely follows the ICON consensus model
through 72 hours, but is a little above ICON after that due to the
large cyclone requiring more time than normal to spin down.

Although the cyclone is forecast to remain well offshore of the
southwestern United States, a northward surge of moisture partly
associated with this system could move into that region by late
Wednesday and Thursday. Please monitor products issued by your
local National Weather Service office for more details on a possible
heavy rainfall threat.

FORECAST POSITIONS AND MAX WINDS

INIT 18/1500Z 16.7N 117.7W 30 KT 35 MPH
12H 19/0000Z 17.1N 118.7W 35 KT 40 MPH
24H 19/1200Z 17.7N 119.8W 40 KT 45 MPH
36H 20/0000Z 18.3N 120.3W 45 KT 50 MPH
48H 20/1200Z 18.9N 120.5W 50 KT 60 MPH
72H 21/1200Z 20.4N 121.0W 50 KT 60 MPH
96H 22/1200Z 22.8N 122.6W 45 KT 50 MPH
120H 23/1200Z 25.5N 125.0W 35 KT 40 MPH...POST-TROPICAL

$$
Forecaster Stewart

[Yellow Evan]

EP, 12, 2014081818, , BEST, 0, 165N, 1177W, 30, 1005, TD, 34, NEQ, 0, 0, 0, 0, 1010, 210, 90, 0, 0, E, 0, , 0, 0, TWELVE, M,

[cycloneye]

TROPICAL DEPRESSION TWELVE-E DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122014
200 PM PDT MON AUG 18 2014

The sprawling depression has been moving slowly west-northwestward
or 285/05 kt over the past 12 hours. The large cyclone is expected
to move slowly northwestward and then northward around the
southwestern periphery of a strong subtropical ridge during the next
72 hours or so. An unseasonably strong mid- to upper-level
trough dropping south-southeastward along the U.S. west coast,
which is expected to induce the northward motion by weakening the
ridge, is forecast by most of the NHC models to shift eastward into
the southwestern U.S. by Thursday. This will allow the ridge to
build back in to the north of the system, turning the cyclone back
to a northwesterly and west-northwesterly track after day 4. The new
forecast track is similar to the previous advisory track through 72
hours, but was shifted westward after that time closer to the
consensus model TVCE.

Subjective satellite intensity estimates from TAFB and SAB are a
consensus T2.0/30 kt. Some of the objective satellite analyses,
however, suggest that the cyclone could be a little higher. The
sprawling nature of the depression and moderate easterly shear of
15-18 kt are expected to result in only slow strengthening for the
next 72 hours. After that time, the cyclone is forecast to move over
sub-26C SSTs, which should induce a slow weakening trend. The
intensity forecast is just an update of the previous advisory and
closely follows the ICON consensus model.

A northward surge of moisture into the southwestern United States,
partly caused by the eastern portion of the depression's large
circulation, is still forecast by most of the global models to occur
by late Wednesday and Thursday. Please monitor products issued by
your local National Weather Service office for more details on a
possible heavy rainfall threat.

FORECAST POSITIONS AND MAX WINDS

INIT 18/2100Z 16.6N 117.9W 30 KT 35 MPH
12H 19/0600Z 17.0N 118.8W 35 KT 40 MPH
24H 19/1800Z 17.6N 119.7W 40 KT 45 MPH
36H 20/0600Z 18.2N 120.1W 45 KT 50 MPH
48H 20/1800Z 18.9N 120.4W 50 KT 60 MPH
72H 21/1800Z 20.6N 121.3W 50 KT 60 MPH
96H 22/1800Z 23.0N 123.3W 40 KT 45 MPH
120H 23/1800Z 25.3N 125.8W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart

[Steve820]

Looks like an upcoming flood threat for SoCal, hopefully it won't cause floods because first of all, I live there. Hopefully it just brings beneficial rain since we're currently in a big drought. I think the depression will peak around 65 mph.

[supercane4867]

It will be interesting to see the close interaction between Lowell and Karina, will the latter even get absorbed?

[Yellow Evan]

EP, 12, 2014081900, , BEST, 0, 168N, 1183W, 35, 1000, TS, 34, NEQ, 0, 120, 0, 0, 1008, 260, 90, 0, 0, E, 0, , 0, 0, TWELVE, D,

[cycloneye]

TROPICAL STORM LOWELL DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122014
800 PM PDT MON AUG 18 2014

The cyclone has become slightly better organized over the past
several hours, although the center remains on the northeastern side
of a large area of deep convection. Dvorak estimates have risen to
35 kt from both TAFB and SAB, so the initial wind speed is raised
to that value. Lowell has a couple of days to intensify further
while it remains over warm waters with moderate easterly shear.
Only gradual strengthening is anticipated due to the large size of
the system and its large radius of maximum winds. In a few days,
the storm should traverse cooler waters and begin to slowly weaken.
Model guidance is tightly clustered, and the new NHC intensity
forecast is close to a blend of the previous interpolated forecast
and the latest model consensus.

The storm has turned a little more to the right and is now moving
295/6. Lowell is expected to move slowly northwestward and then
northward over the next couple of days as it moves into a weakness
in the subtropical ridge caused by an unseasonably strong deep-layer
trough across the U.S. west coast. Little change was made to the
previous NHC forecast in the first 48 hours with model guidance in
excellent agreement. The trough should pass the storm by late
Wednesday and then the subtropical ridge is expected to
restrengthen, forcing Lowell to turn to the northwest at an
increasing forward speed after day 3. Similar to the last forecast
cycle, the guidance has shifted westward at longer range, and the
NHC track prediction is moved in that direction.

A northward surge of moisture into the southwestern United States,
partly caused by the eastern portion of the cyclone's large
circulation, is still forecast by most of the global models to occur
by late Wednesday and Thursday. Please monitor products issued by
your local National Weather Service office for more details on a
possible heavy rainfall threat.

FORECAST POSITIONS AND MAX WINDS

INIT 19/0300Z 17.0N 118.6W 35 KT 40 MPH
12H 19/1200Z 17.4N 119.4W 40 KT 45 MPH
24H 20/0000Z 18.0N 120.0W 45 KT 50 MPH
36H 20/1200Z 18.6N 120.4W 50 KT 60 MPH
48H 21/0000Z 19.3N 120.8W 50 KT 60 MPH
72H 22/0000Z 21.0N 121.9W 45 KT 50 MPH
96H 23/0000Z 23.4N 124.5W 35 KT 40 MPH
120H 24/0000Z 25.5N 127.5W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Blake

[Yellow Evan]

Looks good atm, with some very cold cloud tops. Likely still some wind shear though.

[cycloneye]

TROPICAL STORM LOWELL DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122014
200 AM PDT TUE AUG 19 2014

Lowell is on a strengthening trend. The cloud pattern of the storm
has become better organized during the last several hours with the
associated banding features now beginning to wrap around the
center. ASCAT overpasses around 0500 UTC showed maximum reliable
winds in the 40-45 kt range and a large radius of maximum winds of
about 80 n mi. The initial wind speed is set at 45 kt, which is a
little higher than the latest Dvorak classifications. Lowell is
expected to remain in an environment of moderate shear, high
moisture, and over relatively warm water for another couple of
days. These conditions should allow for some additional
strengthening. Beyond that time, Lowell will be moving over cooler
water and into a stable air mass, which should cause the system to
weaken. The NHC intensity forecast is a little higher than the
previous one and in good agreement with the model consensus, IVCN.

The tropical storm is moving west-northwestward, 295 degrees, at 6
kt steered by a ridge to its northeast. A gradual turn toward the
north-northwest is expected by tonight when a trough deepens over
the southwestern United States. This trough is expected to lift out
on Thursday, allowing for some ridging to become re-established to
the north of Lowell. This pattern change should cause the system to
bend to the left at days 4 and 5. The NHC track forecast is fairly
close to the previous one and near the middle of the guidance
envelope.

A northward surge of moisture over the northern Baja California
peninsula and the southwestern United States, partly associated with
the eastern portion of the cyclone's large circulation, is still
forecast by most of the global models to occur late Wednesday and
Thursday. Please monitor products issued by your local National
Weather Service office for more details on a possible heavy rainfall
threat.

FORECAST POSITIONS AND MAX WINDS

INIT 19/0900Z 17.3N 119.0W 45 KT 50 MPH
12H 19/1800Z 17.7N 119.8W 50 KT 60 MPH
24H 20/0600Z 18.3N 120.5W 55 KT 65 MPH
36H 20/1800Z 18.9N 120.9W 55 KT 65 MPH
48H 21/0600Z 19.5N 121.3W 55 KT 65 MPH
72H 22/0600Z 21.6N 123.0W 50 KT 60 MPH
96H 23/0600Z 24.0N 125.5W 40 KT 45 MPH
120H 24/0600Z 26.2N 128.8W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Cangialosi

[Yellow Evan]

EP, 12, 2014081912, , BEST, 0, 175N, 1195W, 45, 996, TS, 34, NEQ, 70, 120, 0, 0, 1008, 260, 80, 0, 0, E, 0, , 0, 0, LOWELL, D,

Still 45 knts.

[cycloneye]

TROPICAL STORM LOWELL DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122014
800 AM PDT TUE AUG 19 2014

The structure of Lowell has not changed much over the past few
hours, with most of the deep convection located south and southeast
of the center. The initial intensity remains 45 kt based on the
earlier ASCAT pass, which is also in agreement with the latest
Dvorak classification from TAFB. Some strengthening is forecast in
the short term, as Lowell will be in an environment of moderate
vertical shear and over warm waters. After that time, Lowell will
be moving over cooler waters and into a drier and more stable
airmass, which should result in steady weakening to remnant low
status by the end of the forecast period. The NHC intensity
forecast is similar to the previous one and is close to the latest
IVCN intensity consensus.

There is a fair bit of spread in the satellite fixes, which is not
surprising given the sprawling structure of the circulation. The
initial motion estimate of 300/06 is based on a blend of the fixes
and continuity from the previous advisory. The track forecast
reasoning remains unchanged. The subtropical ridge currently
steering Lowell will weaken as a shortwave trough digs southward
along the California coast in the next 24 to 36 hours. After that
time, some ridging rebuilds to the north, which should turn a
weakening Lowell back toward the west-northwest by the end of the
period. The new NHC track forecast is similar to the previous one
and close to the TVCE consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 19/1500Z 17.7N 119.7W 45 KT 50 MPH
12H 20/0000Z 18.2N 120.5W 50 KT 60 MPH
24H 20/1200Z 18.8N 121.0W 55 KT 65 MPH
36H 21/0000Z 19.4N 121.3W 55 KT 65 MPH
48H 21/1200Z 20.1N 121.8W 55 KT 65 MPH
72H 22/1200Z 22.5N 124.0W 50 KT 60 MPH
96H 23/1200Z 25.0N 127.0W 40 KT 45 MPH
120H 24/1200Z 26.5N 130.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brennan

[Yellow Evan]

EP, 12, 2014081918, , BEST, 0, 181N, 1201W, 45, 996, TS, 34, NEQ, 70, 120, 0, 0, 1008, 260, 80, 0, 0, E, 0, , 0, 0, LOWELL, D,

[cycloneye]

TROPICAL STORM LOWELL DISCUSSION NUMBER 8
NWS NATIONAL HURRICANE CENTER MIAMI FL EP122014
200 PM PDT TUE AUG 19 2014

A recent ASCAT-B pass over Lowell around 1800 UTC confirmed that the
cyclone still has a large wind field, with 34-kt winds extended out
more than 100 nautical miles in all quadrants. ASCAT showed some 40
kt winds east of the center, and assuming a bit of a low bias, the
initial intensity remains 45 kt for this advisory. Lowell will
remain in a moderate shear environment for the next day or so while
still over SSTs above 27C, which could support a little
strengthening in short term, followed by little change through 48
hours. After that time, gradual weakening is expected as Lowell will
move over cooler waters and into a drier and more stable airmass,
and should become a remnant low by 5 days. In general the intensity
guidance has trended lower this cycle, and so has the official
forecast, which is close to the IVCN consensus.

The ASCAT pass and visible satellite imagery yield a little more
certainty with the center position and initial motion estimate of
310/07. Lowell is expected to move slowly northwestward to north-
northwestward over the next 48 hours while a shortwave trough
digs southward along the California coast and weakens the
subtropical ridge. As the trough moves eastward, some ridging will
rebuild to the north, which should result in the weakening cyclone
accelerating west-northwestward by the end of the period. The new
NHC track is once similar to the previous one and close to the TVCE
consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 19/2100Z 18.4N 120.3W 45 KT 50 MPH
12H 20/0600Z 18.8N 120.8W 50 KT 60 MPH
24H 20/1800Z 19.3N 121.3W 50 KT 60 MPH
36H 21/0600Z 20.0N 121.7W 50 KT 60 MPH
48H 21/1800Z 21.0N 122.5W 50 KT 60 MPH
72H 22/1800Z 23.5N 125.0W 45 KT 50 MPH
96H 23/1800Z 25.5N 128.0W 35 KT 40 MPH
120H 24/1800Z 27.5N 131.0W 30 KT 35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brennan

[Kingarabian]

Lowell seems to be ramping up.

[Yellow Evan]

If it ramps quickly enough, it may make a run at becoming our 8th hurricane

[Steve820]

Yeah, it's possible we could see a hurricane out of this. I predict a peak of around 75-80 mph for Lowell.