EPAC: VANCE - Remnants

[Extratropical94]

It has finally been designated Tropical Depression 21-E.

[cycloneye]

TROPICAL DEPRESSION TWENTY-ONE-E DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL EP212014
200 AM PDT THU OCT 30 2014

Deep convection associated with the low pressure area south of
Acapulco, Mexico, has become more concentrated overnight, and recent
microwave and conventional satellite imagery suggest that the
low-level center has become better defined. Therefore, the system
is being designated as a tropical depression. The satellite data
indicate that the center is located near the southern edge of the
main convective mass. Subjective Dvorak T-numbers from TAFB and
SAB are 2.5 and 1.5, respectively. A blend of these estimates
support an initial wind speed of 30 kt.

The depression is over warm water and expected to remain in a low
shear environment during the next several days. The main limiting
factor will be some drier air in the low to mid-levels. As a
result, gradual strengthening is predicted during much of the
forecast period. The NHC forecast is a little above the intensity
guidance through the first couple of days. After 72 hours, the
NHC forecast is in good agreement with the HWRF which brings the
cyclone to hurricane strength in about 4 days. Increasing
south-southwesterly shear could halt any additional strengthening
after that time.

The depression is moving west-northwestward at about 5 kt. The
depression is forecast to turn west-southwestward later today as a
mid-level ridge builds to the north and northwest of the cyclone.
The ridge is forecast to shift eastward during the next few days,
which should cause the cyclone to turn west-northwestward, then
northwestward in 48 to 72 hours. After that time, the tropical
cyclone is forecast to turn northward while a mid-latitude trough
approaches the Baja California peninsula. The track guidance is in
good agreement on this scenario and the NHC track is near the middle
of the guidance envelope.


FORECAST POSITIONS AND MAX WINDS

INIT 30/0900Z 11.0N 100.2W 30 KT 35 MPH
12H 30/1800Z 11.1N 100.8W 35 KT 40 MPH
24H 31/0600Z 10.8N 101.8W 40 KT 45 MPH
36H 31/1800Z 10.3N 102.9W 45 KT 50 MPH
48H 01/0600Z 10.1N 104.2W 50 KT 60 MPH
72H 02/0600Z 10.9N 107.7W 60 KT 70 MPH
96H 03/0600Z 14.0N 110.0W 70 KT 80 MPH
120H 04/0600Z 18.0N 109.0W 70 KT 80 MPH

$$
Forecaster Brown

[Yellow Evan]

EP, 21, 2014103012, , BEST, 0, 112N, 1010W, 30, 1007, TD, 34, NEQ, 0, 0, 0, 0, 1010, 150, 80, 0, 0, E, 0, , 0, 0, TWENTY-ONE, M,

[cycloneye]

TROPICAL DEPRESSION TWENTY-ONE-E DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL EP212014
800 AM PDT THU OCT 30 2014

The depression has become a little better organized with a more
prominent central dense overcast feature forming overnight. However,
recent microwave images show that the center remains on the
southwestern edge of the deep convection, suggesting that
southwesterly shear continues to affect the depression. Although
the overall satellite presentation has improved, Dvorak intensity
estimates are unchanged, so the initial wind speed will
conservatively remain 30 kt.

Although the depression is over warm water, southwesterly shear and
dry air in the low- to mid-levels are expected to continue for
the next day or two. As a result, the latest model guidance does
not show a lot of strengthening, and the NHC forecast continues the
trend of showing only slow intensification. After that time, the
global models forecast a reduction in the shear, along with an
increase in moisture. These conditions should promote more
significant strengthening at longer ranges. The NHC forecast is
closest to the SHIPS models at days 3-4, and remains above the model
consensus after considering the favorable large-scale environment.
Increasing south-southwesterly shear could halt any additional
strengthening after that time.

The center appears to have reformed a little northeast of the
previous estimates closer to the stronger thunderstorm activity,
leading to an uncertain initial motion estimate of west at 5 kt.
The depression is forecast to turn west-southwestward and
southwestward during the next 36 hours while a mid-level ridge
builds to the north and northwest of the cyclone. The ridge is
forecast to shift eastward during the next few days, which should
cause the cyclone to turn west-northwestward and then northwestward
in 48 to 72 hours. After that time, the tropical cyclone is
forecast to turn northward while a mid-latitude trough approaches
the Baja California peninsula. The official NHC forecast is a
little faster than the consensus after accounting for the
unrealistically slow HWRF solution, and is very close to the
previous forecast.

FORECAST POSITIONS AND MAX WINDS

INIT 30/1500Z 11.5N 100.9W 30 KT 35 MPH
12H 31/0000Z 11.4N 101.5W 35 KT 40 MPH
24H 31/1200Z 10.7N 102.4W 40 KT 45 MPH
36H 01/0000Z 10.4N 103.7W 45 KT 50 MPH
48H 01/1200Z 10.4N 105.3W 50 KT 60 MPH
72H 02/1200Z 11.9N 108.7W 65 KT 75 MPH
96H 03/1200Z 15.5N 110.0W 75 KT 85 MPH
120H 04/1200Z 20.0N 108.0W 70 KT 80 MPH

$$
Forecaster Blake

[somethingfunny]

Interesting that the forecast is calling for 21E/Vance to become a hurricane despite these early struggles, and even more interesting that the forecast maintains it as a hurricane after it makes the northeast turn and heads for the Mexican coastline.

I'm not sure I buy it entirely, but the NHC (who are actual professionals unlike me) sure thinks it's likely enough to make it an official forecast.

[cycloneye]

18z Best Track.Here comes Vance.

EP, 21, 2014103018, , BEST, 0, 111N, 1008W, 35, 1005, TS, 34, NEQ, 0, 0, 0, 40, 1010, 150, 40, 0, 0, E, 0, , 0, 0, VANCE, M,

[cycloneye]

TROPICAL STORM VANCE DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL EP212014
200 PM PDT THU OCT 30 2014

Visible satellite images show that the center of the cyclone
remains near the southwestern edge of the deep convection. Still,
the convective organization has improved from a few hours ago, with
a distinct band on the northeast side of the system. Dvorak
estimates and scatterometer data support an initial wind speed of 35
kt for this advisory. Vance is the 20th named storm of the eastern
North Pacific hurricane season, the most number of named storms in
the basin since 1992.

The scatterometer data suggests that Vance is now moving about
260/4. A southwestward motion is expected tomorrow as a ridge
builds to the north of the cyclone. The storm should turn westward
and west-northwestward by 72 hours while it moves across the
southwestern periphery of the ridge. Vance will likely turn
northward or north-northeastward at long range ahead of a
mid-latitude trough diving over Baja California into the eastern
Pacific. While there is broad agreement on the general synoptic
pattern, the models have a stronger ridge than the last cycle,
leading to the storm moving farther to the west and south. This
shift in the steering has led to a slower solution at long range
by almost every reliable model. The official NHC prediction is
shifted westward and southward throughout the forecast period, and
further adjustments could be required on the next advisory if model
trends continue.

Although Vance is expected to remain over warm water for the next
several days, it is currently struggling with dry air entrainment
and southwesterly shear. Most of the models respond to this
environment by showing little significant intensity change during
the next 24 hours, so the official forecast will follow suit.
After that time, the global models continue to show reduced shear,
with an increase in low- to mid-level moisture. These conditions
should allow for Vance to become a hurricane in a few days,
although guidance is not in particularly good agreement on this
scenario. At long range, there is high uncertainty in the
intensity forecast, with the models generally showing more shear
than the last cycle. Thus the intensity prediction is lowered some
from the previous NHC forecast, although it remains on the higher
side of the guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 30/2100Z 11.0N 101.0W 35 KT 40 MPH
12H 31/0600Z 10.6N 101.6W 40 KT 45 MPH
24H 31/1800Z 10.1N 102.5W 40 KT 45 MPH
36H 01/0600Z 9.9N 104.0W 45 KT 50 MPH
48H 01/1800Z 10.1N 105.9W 50 KT 60 MPH
72H 02/1800Z 12.0N 109.6W 65 KT 75 MPH
96H 03/1800Z 16.0N 110.5W 70 KT 80 MPH
120H 04/1800Z 20.0N 108.5W 60 KT 70 MPH

$$
Forecaster Blake

[Macrocane]

First "V" storm by the NHC since 2005 Vince in the Atlantic.

[Tireman4]

The EPAC does have names past Z, correct?

Winnie (unused)
Xavier (unused)
Yolanda (unused)
Zeke (unused)

[Macrocane]

The EPAC does have names past Z, correct?

Winnie (unused)
Xavier (unused)
Yolanda (unused)
Zeke (unused)

I'm not sure but I think they would go with the Greek Alphabet too.

[Tireman4]

The EPAC does have names past Z, correct?

Winnie (unused)
Xavier (unused)
Yolanda (unused)
Zeke (unused)

I'm not sure but I think they would go with the Greek Alphabet too.

I would think so too Macro, but I was not sure. I have a feeling they might get past Z..

[Yellow Evan]

The EPAC does have names past Z, correct?

Winnie (unused)
Xavier (unused)
Yolanda (unused)
Zeke (unused)

I'm not sure but I think they would go with the Greek Alphabet too.

I would think so too Macro, but I was not sure. I have a feeling they might get past Z..

It's October 30, so the season is almost over. But yes, they use the Greeks after Z, though that's never happened before.

[cycloneye]

00z Best Track up to 40kts.

EP, 21, 2014103100, , BEST, 0, 109N, 1011W, 40, 1005, TS, 34, NEQ, 40, 0, 0, 40, 1010, 150, 40, 0, 0, E, 0, , 0, 0, VANCE, M,

[TropicalAnalystwx13]

It's no coincidence that Vance didn't form and begin to intensify until the brunt of the convectively-suppressed kelvin wave moved eastward into the Caribbean Sea.

[cycloneye]

TROPICAL STORM VANCE DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL EP212014
800 PM PDT THU OCT 30 2014

Vance has strengthened a little this evening. Infrared satellite
images indicate that deep convection has increased slightly to the
northeast of the center and in a band on the south and east sides of
the circulation. A blend of the latest Dvorak intensity estimates
from TAFB, SAB, and the University of Wisconsin-CIMSS supports
raising the initial wind speed to 40 kt. Southerly to southwesterly
shear and dry air in the low- to mid-levels of the atmosphere are
currently affecting Vance, and these conditions are expected to
persist for about another day. Therefore, only slow strengthening
is predicted during that time. Over the weekend, however, the
atmosphere is expected to moisten near the storm while the shear
lessens, providing a better opportunity for more significant
strengthening. By the end of the forecast period, the global models
show a sharp increase in southwesterly shear, which should cause the
cyclone to begin weakening. The NHC intensity forecast lies
between the SHIPS model and the intensity model consensus.

The storm has been moving slowly west-southwestward during the past
6 to 12 hours. A mid-level ridge located to the north and northwest
of Vance is expected to steer the cyclone west-southwestward to
westward during the next day or two. After that time, a gradual
turn to the north and then northeast is forecast as the ridge
weakens and shifts eastward in response to an approaching large
trough. Although the models are in agreement in the large-scale
steering pattern, there is a fair amount of spread in where Vance
turns northward. The NHC track forecast has been adjusted a little
to the left of the previous one for the first 72 hours to be in
better agreement with the latest guidance.

FORECAST POSITIONS AND MAX WINDS

INIT 31/0300Z 10.8N 101.3W 40 KT 45 MPH
12H 31/1200Z 10.4N 102.0W 45 KT 50 MPH
24H 01/0000Z 10.0N 103.3W 50 KT 60 MPH
36H 01/1200Z 9.9N 105.1W 50 KT 60 MPH
48H 02/0000Z 10.4N 107.0W 55 KT 65 MPH
72H 03/0000Z 12.9N 110.2W 70 KT 80 MPH
96H 04/0000Z 17.1N 110.4W 65 KT 75 MPH
120H 05/0000Z 20.5N 107.5W 45 KT 50 MPH

$$
Forecaster Cangialosi

[cycloneye]

TROPICAL STORM VANCE DISCUSSION NUMBER 5
NWS NATIONAL HURRICANE CENTER MIAMI FL EP212014
200 AM PDT FRI OCT 31 2014

Several overnight microwave images and ASCAT data indicate that the
center of Vance is located farther south and east than previously
estimated. The center is near the southern edge of the large mass
of deep convection due to moderate south-southwesterly shear. The
ASCAT data and Dvorak satellite intensity estimates support
maintaining an initial wind speed of 40 kt. The shear and some dry
low- to mid-level air are expected to continue to affect the
tropical cyclone during the next 12 to 24 hours, and only gradual
strengthening is expected during that time. Environmental conditions
are forecast to become more conducive for strengthening over the
weekend, and most of the intensity guidance shows Vance becoming a
hurricane in 2 to 3 days. By day 4, increasing southwesterly
upper-level flow ahead of a large mid-latitude trough is expected to
cause a significant increase in shear. This should cause weakening
late in the period. The NHC intensity forecast is similar to the
previous advisory and is near the model consensus.

Due to the center relocation, the initial motion is a highly
uncertain 245/3 kt. Vance is expected to move west-southwestward
today around the southeastern portion of a mid-level ridge near the
southern Baja California peninsula. The ridge is forecast to shift
eastward during the next several days while the aforementioned
trough approaches the west coast of California. This should cause
Vance to turn west-northwestward, then northwestward over the
weekend. After 72 hours, Vance is forecast to turn northward, then
northeastward ahead of the trough. The track guidance remains in
agreement on this scenario but there remains some spread in the
timing of the northward turn, and the forward speed of Vance later
in the period. The updated NHC forecast is similar to the previous
track through 72 hours, but is a little faster than the previous
advisory at days 4 and 5.


FORECAST POSITIONS AND MAX WINDS

INIT 31/0900Z 10.5N 101.0W 40 KT 45 MPH
12H 31/1800Z 10.1N 101.6W 45 KT 50 MPH
24H 01/0600Z 9.8N 103.1W 50 KT 60 MPH
36H 01/1800Z 10.0N 104.8W 55 KT 65 MPH
48H 02/0600Z 10.9N 106.8W 60 KT 70 MPH
72H 03/0600Z 14.0N 110.0W 70 KT 80 MPH
96H 04/0600Z 18.5N 109.0W 60 KT 70 MPH
120H 05/0600Z 22.5N 106.0W 40 KT 45 MPH

$$
Forecaster Brown

[cycloneye]

TROPICAL STORM VANCE DISCUSSION NUMBER 6
NWS NATIONAL HURRICANE CENTER MIAMI FL EP212014
800 AM PDT FRI OCT 31 2014

There hasn't been a lot of significant change with the structure of
Vance during the past several hours. While the central convection
has weakened some, the convection associated with a banding feature
on the east side has increased. Dvorak estimates are similar to 6
hours ago, so the initial wind speed will remain 40 kt. Vance
continues to struggle with southwesterly shear and dry air. Most
of the models, however, suggest that the shear should abate over the
weekend, with increasing moisture and upper-level divergence
expected as well. The latest model guidance generally shows a
higher peak intensity, and the NHC forecast is now a bit higher at
48-72 hours. After that time, a significant increase in
southwesterly shear is forecast, which will likely cause weakening
while the cyclone approaches Mexico.

The center has not been easy to track with this cyclone, but the
latest microwave and visible satellite data suggest it has been
creeping toward the south-southwest. A ridge over the eastern
Pacific is expected to move eastward over the next few days,
steering the cyclone more steadily west-southwestward by late today,
westward tomorrow, and to the northwest by late this weekend. Vance
is then forecast to turn northward and then northeastward ahead of a
trough moving over Baja California. While the models are in good
agreement on the overall track, there remains some spread in the
timing of the turn toward Mexico. The guidance is generally faster
than the last cycle, so the updated NHC forecast follows that trend.
Overall the forecast is also little east of the previous one, mostly
because of the initial motion and position.

FORECAST POSITIONS AND MAX WINDS

INIT 31/1500Z 10.1N 100.8W 40 KT 45 MPH
12H 01/0000Z 9.7N 101.7W 45 KT 50 MPH
24H 01/1200Z 9.6N 103.2W 50 KT 60 MPH
36H 02/0000Z 10.2N 105.2W 55 KT 65 MPH
48H 02/1200Z 11.4N 107.0W 65 KT 75 MPH
72H 03/1200Z 15.0N 109.3W 75 KT 85 MPH
96H 04/1200Z 19.3N 107.9W 55 KT 65 MPH
120H 05/1200Z 23.5N 105.0W 30 KT 35 MPH...INLAND

$$
Forecaster Blake

[cycloneye]

TROPICAL STORM VANCE DISCUSSION NUMBER 7
NWS NATIONAL HURRICANE CENTER MIAMI FL EP212014
200 PM PDT FRI OCT 31 2014

Vance has a peculiar structure this afternoon. The central
convection has become somewhat skeletal with the center exposed at
times, although there are still plenty of curved banding features in
the outer portion of the circulation. The culprit for this decrease
in convection appears to be an influx of dry air moving into the
central region of the tropical cyclone around the west and south
sides. Dvorak estimates still support an intensity of about 40 kt.

Since the dry air is close to the center now, it will probably take
some time for this air to mix out. Thus little change is shown in
the short term. Afterward, models insist that the large-scale
environment will become favorable for strengthening over the next
three days or so. Strong southwesterly shear is anticipated for the
beginning of next week, which will probably cause Vance to weaken
significantly at long range. There has not been much change to the
guidance suite, with the majority of the guidance still showing
Vance as a hurricane in a few days. The NHC forecast is therefore
very close to the previous one, and generally lies between the
intensity consensus and the SHIPS model.

It seems that finally the motion of Vance has become more clear, now
moving west-southwestward at about 6 kt. This general motion is
expected through tonight due to a ridge over the eastern Pacific.
This ridge should move eastward over the next few days, steering the
cyclone more westward tomorrow, and to the northwest by late this
weekend. Vance is then forecast to turn northward and then north-
northeastward ahead of a trough moving over Baja California. Subtle
differences in the speed of the trough are leading to increased
model spread at long range, with the faster ECMWF preferring a more
north-northeast track, compared to the slower GFS solution of a
sharper northeastward turn. The NHC forecast is adjusted westward
at day 3 and beyond, and is close to a dynamical model consensus
excluding the UKMET model, which has an improbable forecast due to a
seemingly spurious interaction with a weak ITCZ disturbance.


FORECAST POSITIONS AND MAX WINDS

INIT 31/2100Z 9.5N 101.4W 40 KT 45 MPH
12H 01/0600Z 9.3N 102.4W 40 KT 45 MPH
24H 01/1800Z 9.6N 104.1W 45 KT 50 MPH
36H 02/0600Z 10.5N 106.2W 55 KT 65 MPH
48H 02/1800Z 11.7N 108.4W 65 KT 75 MPH
72H 03/1800Z 16.0N 110.5W 70 KT 80 MPH
96H 04/1800Z 19.8N 108.5W 50 KT 60 MPH
120H 05/1800Z 23.5N 106.0W 30 KT 35 MPH...INLAND

$$
Forecaster Blake

[somethingfunny]

I don't think Vance is gonna make it to hurricane.

[CrazyC83]

Neither do I...but we shall see.