EPAC: NORMA - Troipical Storm

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Re: EPAC: NORMA - Tropical Storm

#21 Postby Extratropical94 » Thu Sep 14, 2017 9:55 am

Tropical Storm Norma Discussion Number 1
NWS National Hurricane Center Miami FL EP172017
900 AM MDT Thu Sep 14 2017

The convective structure of the area of disturbed weather well to
the south of the Baja California peninsula has continued to
increase in organization, with an elongated band wrapping around
the southern and eastern sides of the circulation. Dvorak intensity
estimates have increased to T3.0/45 kt from TAFB and T2.0/30 kt
from SAB, so the system is now classified as a 35-kt tropical storm.

Since Norma has just recently consolidated, its motion is a little
uncertain, but the best estimate is slowly northward, or 360/4 kt.
Norma is located to the northwest of a mid-level ridge that extends
westward from Central America, but it is also due south of a
blocking high centered over northwestern Mexico. As a result, the
storm is expected to only drift slowly northward for the next 48
hours or so. After 48 hours, a more pronounced northward motion is
forecast, but there is a lot of spread among the track models
regarding exactly how fast Norma moves north and if it moves east or
west at all. On the eastern side of the guidance envelope, the GFS
has a weaker ridge over Mexico and a deeper trough off the
California coast, which would cause Norma to turn northeastward
near the southern part of the Baja California peninsula. On the
western side of the guidance, the ECMWF maintains a stronger ridge,
forcing Norma to turn northwestward to the west of the Baja
California peninsula. Until the evolving pattern becomes clearer,
the NHC track forecast is between these two extremes and lies
closest to the HFIP Corrected Consensus Approach (HCCA).

Norma is over very warm waters and should remain in a low-shear
environment for at least the next 48-72 hours. As a result,
steady strengthening is anticipated, and Norma could reach
hurricane strength within about 36 hours. Strengthening should
continue through 48-72 hours until vertical shear begins to
increase, and a weakening trend is likely to occur on days 4 and 5.
The NHC intensity forecast closely follows the SHIPS guidance and
the ICON intensity consensus, and it is slightly below the HCCA
output.

FORECAST POSITIONS AND MAX WINDS

INIT 14/1500Z 17.2N 109.5W 35 KT 40 MPH
12H 15/0000Z 17.7N 109.5W 45 KT 50 MPH
24H 15/1200Z 18.1N 109.5W 55 KT 65 MPH
36H 16/0000Z 18.4N 109.4W 65 KT 75 MPH
48H 16/1200Z 18.9N 109.4W 75 KT 85 MPH
72H 17/1200Z 21.0N 110.1W 75 KT 85 MPH
96H 18/1200Z 23.5N 111.0W 65 KT 75 MPH
120H 19/1200Z 25.5N 110.5W 55 KT 65 MPH

$$
Forecaster Berg
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Re: EPAC: NORMA - Tropical Storm

#22 Postby CrazyC83 » Thu Sep 14, 2017 10:36 am

I wouldn't be surprised if this became a big problem down the road. The GFS goes nuts with this, right?
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Re: EPAC: NORMA - Tropical Storm

#23 Postby Yellow Evan » Thu Sep 14, 2017 10:46 am

CrazyC83 wrote:I wouldn't be surprised if this became a big problem down the road. The GFS goes nuts with this, right?


Yes, although the ECMWF keeps it offshore.
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Re: EPAC: NORMA - Tropical Storm

#24 Postby Yellow Evan » Thu Sep 14, 2017 10:29 pm

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Tropical Storm Norma Discussion Number 3
NWS National Hurricane Center Miami FL EP172017
900 PM MDT Thu Sep 14 2017

The large circulation of Norma was well-defined in late afternoon
visible satellite images, however, the colder convective cloud tops
remain fragmented in infrared satellite imagery. Since the
convective banding has not significantly improved this evening, the
Dvorak data T-numbers have remained about the same as this
afternoon, and the initial intensity of 40 kt is maintained for
this advisory.

Recent satellite fixes show that Norma is moving slowly northward
or 360/5 kt. A large high pressure area over northern Mexico and
an associated ridge that extends southwestward across the Baja
California peninsula should keep Norma on a slow northward track
during the next couple of days. After that time, the model spread
significantly increases with the ECMWF and UKMET models turning
Norma west-northwestward, taking it west or southwest of Baja
California. The GFS and HWRF weaken the ridge and move Norma
northward across Baja California Sur ahead of a mid-latitude trough
that deepens southwest of southern California. The NHC forecast
continues to follow the latter scenario since it is favored by the
HFIP corrected consensus model and is also fairly close to the
TVCN consensus aid. The updated track forecast is similar to the
previous advisory, but the confidence in the track forecast remains
quite low due to the usually large model disagreement.

Norma is forecast to remain within a favorable environment of low
vertical wind shear and over warm water, however, the large and
sprawling structure of the tropical cyclone may temper the
intensification rate in the short-term. As a result, the updated
NHC intensity forecast is slightly lower than the previous advisory
through 72 hours, and it is between the ICON intensity consensus
and the slightly more aggressive HCCA consensus. Land interaction
and increasing southwesterly shear is likely to lead to weakening
later in the period.


FORECAST POSITIONS AND MAX WINDS

INIT 15/0300Z 18.3N 109.3W 40 KT 45 MPH
12H 15/1200Z 18.7N 109.3W 50 KT 60 MPH
24H 16/0000Z 19.2N 109.3W 60 KT 70 MPH
36H 16/1200Z 19.7N 109.4W 70 KT 80 MPH
48H 17/0000Z 20.6N 109.6W 75 KT 85 MPH
72H 18/0000Z 22.7N 110.3W 70 KT 80 MPH
96H 19/0000Z 25.1N 110.6W 55 KT 65 MPH
120H 20/0000Z 27.5N 109.0W 35 KT 40 MPH...INLAND

$$
Forecaster Brown

NNNN
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Re: EPAC: NORMA - Tropical Storm

#25 Postby Yellow Evan » Fri Sep 15, 2017 8:35 am

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Tropical Storm Norma Discussion Number 4
NWS National Hurricane Center Miami FL EP172017
300 AM MDT Fri Sep 15 2017

The cloud pattern continues to be well organized and convection has
been gradually increasing, primarily in a band to the east of the
center. Dvorak T-numbers and an ASCAT pass over the cyclone indicate
that the initial intensity is 45 kt. With low shear prevailing and
Norma moving over warm waters, gradual strengthening is forecast.
Norma is expected to become a hurricane before it approaches the
Baja California peninsula.

Norma appears to be moving very slowly toward the north at about 2
kt. Steering currents are weak and are provided by a weak ridge of
high pressure over Mexico. This flow is not expected to change
much, so Norma should continue to move very slowly. There was a
change in track guidance tonight, and most of the models shifted a
little bit westward, primarily beyond 3 days. On this basis, the
NHC forecast was also adjusted westward. The latter portion of the
forecast, however, is highly uncertain since the track models
diverge significantly. The NHC track forecast follows the HFIP
corrected consensus, HCCA, and the multi-model simple consensus as
well.

A Hurricane Watch will likely be necessary for portions of the
southern Baja California peninsula later today.


FORECAST POSITIONS AND MAX WINDS

INIT 15/0900Z 18.6N 109.7W 45 KT 50 MPH
12H 15/1800Z 19.0N 109.8W 50 KT 60 MPH
24H 16/0600Z 19.4N 110.0W 60 KT 70 MPH
36H 16/1800Z 20.0N 110.1W 70 KT 80 MPH
48H 17/0600Z 20.6N 110.3W 70 KT 80 MPH
72H 18/0600Z 22.8N 111.4W 70 KT 80 MPH
96H 19/0600Z 24.5N 112.0W 50 KT 60 MPH
120H 20/0600Z 26.3N 110.7W 35 KT 40 MPH

$$
Forecaster Avila

NNNN
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Re: EPAC: NORMA - Tropical Storm

#26 Postby Ntxw » Fri Sep 15, 2017 9:07 am

Getting better organized

Image
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Re: EPAC: NORMA - Tropical Storm

#27 Postby zeehag » Fri Sep 15, 2017 12:33 pm

rats.
i' m-a gonna die again arent i.
current location: GPS Coordinates: 23° 16.0' N 106° 29.0' W .
shrimpers have been moved to culiacan area, into their safe place, ordered by capitania de puerto.
the center will be passing closer than mazatlan desires.
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Re: EPAC: NORMA - Tropical Storm

#28 Postby Yellow Evan » Fri Sep 15, 2017 1:06 pm

000
WTPZ42 KNHC 151434
TCDEP2

Tropical Storm Norma Discussion Number 5
NWS National Hurricane Center Miami FL EP172017
900 AM MDT Fri Sep 15 2017

Norma has an elongated convective band that curls about three
quarters of the way around the low-level center. A well-defined
low-level ring was visible in recent 37-GHz SSMIS imagery,
indicating that the cyclone's structure continues to improve. The
initial intensity is raised to 55 kt based on a blend of Dvorak
estimates which range from 50 kt (UW-CIMSS ADT) to 65 kt (TAFB).

Norma is essentially drifting toward the north-northwest with an
initial motion of 340/2 kt. There's not a whole lot more clarity
on Norma's eventual track compared to yesterday. The most that can
be said is that Norma will continue to drift northwestward or
northward for the next 24-36 hours. After that time, there remains
considerable spread in the track guidance. The ECMWF and UKMET
models, which maintain a stronger ridge over northwestern Mexico,
push Norma northwestward to the west of the Baja California
peninsula through day 5. The GFS and HWRF models, as well as the
consensus aids, remain closer to the Baja California peninsula and
show a northeastward turn by day 5. The NHC track forecast remains
close to the TVCN consensus and is a little slower than, but on top
of, the previous NHC forecast.

Low shear and warm ocean temperatures should foster continued
strengthening, with Norma forecast to become a hurricane by this
evening. Norma is then expected to continue strengthening through
36 or 48 hours. Some southwesterly shear could begin to affect the
cyclone by day 3 as it approaches stronger mid-latitude westerly
flow, and some weakening is forecast as Norma approaches the Baja
California peninsula. The new NHC intensity forecast mirrors the
trend shown in the previous advisory, and is just a little higher
due to the updated initial intensity. This forecast is generally
close to HCCA and the ICON intensity consensus.

A hurricane or tropical storm watch will likely be necessary for
portions of the southern Baja California peninsula later today.

FORECAST POSITIONS AND MAX WINDS

INIT 15/1500Z 18.7N 109.7W 55 KT 65 MPH
12H 16/0000Z 18.9N 109.9W 65 KT 75 MPH
24H 16/1200Z 19.2N 110.0W 70 KT 80 MPH
36H 17/0000Z 19.9N 110.1W 75 KT 85 MPH
48H 17/1200Z 20.8N 110.3W 75 KT 85 MPH
72H 18/1200Z 23.0N 111.5W 65 KT 75 MPH
96H 19/1200Z 24.5N 112.0W 50 KT 60 MPH
120H 20/1200Z 26.5N 110.5W 35 KT 40 MPH

$$
Forecaster Berg
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Re: EPAC: NORMA - Tropical Storm

#29 Postby Yellow Evan » Fri Sep 15, 2017 1:28 pm

15/1800 UTC 18.7N 110.1W T4.0/4.0 NORMA -- East Pacific
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Re: EPAC: NORMA - Tropical Storm

#30 Postby galaxy401 » Fri Sep 15, 2017 3:38 pm

Not yet a hurricane.

Tropical Storm Norma Discussion Number 6
NWS National Hurricane Center Miami FL EP172017
300 PM MDT Fri Sep 15 2017

Norma's primary convective band continues to elongate and curls
about one and a half times around the circulation. Objective and
subjective Dvorak estimates are wide ranging, going from 50 kt up
to 77 kt, but since the deep convective cloud tops are not very
cold, the initial intensity is raised conservatively to 60 kt.
This lower intensity is supported by recent ASCAT data, which only
showed maximum winds of 50 kt.

The environment appears conducive for continued gradual
strengthening. Norma's large size argues against rapid
intensification, but the cyclone should be able to at least
steadily strengthen during the next 36 hours or so. Vertical
shear begins to increase after that time, however, and Norma is
likely to weaken beginning in about 48 hours. The HCCA guidance and
the ICON intensity consensus were notably lower on this cycle, and
the updated NHC forecast has begun to follow that trend, especially
on days 3 through 5.

The center has wobbled northwestward during the day, and the
initial motion estimate is 325/2 kt. Norma should turn slowly
northward during the next day or so, steered along the western
periphery of the subtropical ridge. The track models continue to
play the same tune, with the ECMWF and UKMET models on the far
western side of the guidance envelope and the HWRF and GFS on the
eastern side. Since the overall trend in the guidance has been
westward, the new NHC track forecast leans left of the consensus
aids and is a little left of the previous forecast.

The 48-hour forecast track and wind radii are very close to the
southern tip of the Baja California peninsula. However, with the
persistent westward shifts in the guidance, a tropical storm watch
does not appear to be needed at this time. We will assess future
model trends for the possibility of a watch issuance later tonight
or tomorrow.

FORECAST POSITIONS AND MAX WINDS

INIT 15/2100Z 18.9N 110.1W 60 KT 70 MPH
12H 16/0600Z 19.2N 110.3W 65 KT 75 MPH
24H 16/1800Z 19.6N 110.4W 70 KT 80 MPH
36H 17/0600Z 20.6N 110.6W 75 KT 85 MPH
48H 17/1800Z 21.6N 111.0W 70 KT 80 MPH
72H 18/1800Z 23.5N 112.1W 60 KT 70 MPH
96H 19/1800Z 25.0N 112.0W 45 KT 50 MPH...INLAND
120H 20/1800Z 26.0N 111.0W 30 KT 35 MPH...OVER WATER

$$
Forecaster Berg
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Re: EPAC: NORMA - Hurricane

#31 Postby Yellow Evan » Fri Sep 15, 2017 11:57 pm

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Hurricane Norma Discussion Number 7
NWS National Hurricane Center Miami FL EP172017
900 PM MDT Fri Sep 15 2017

Infrared satellite imagery indicates that banding associated with
Norma has increased during the past few hours. The convective cloud
tops have cooled and the band surrounding the center has become a
little more solid with the formation of a ragged banding eye. Dvorak
data T-numbers from both TAFB and SAB are 4.0, and with the recent
increase in organization the initial wind speed is increased to 65
kt. Norma becomes the eighth hurricane in the eastern Pacific this
season.

Norma should remain over warm water and within a low shear
environment during the next 24 to 36 h. These conditions favor
strengthening, but the large size of Norma is likely to keep the
intensification rate in check. Increasing vertical shear and cooler
waters are expected to impart gradual weakening after 48 hours. The
latest NHC intensity forecast is similar to the previous advisory
and is close to the SHIPS guidance.

Norma has been moving slowly north-northwestward, with an initial
motion estimate of 335/2 kt. The hurricane is forecast to move
slowly northward during the next couple of days, while it remains
along the western side of a mid-level ridge. After that time, the
ECMWF develops a narrow ridge to the north of Norma which causes the
hurricane to turn northwestward. Meanwhile, the GFS keeps Norma on
a north track over the Baja California peninsula. The trend of the
track guidance has been westward during the past several cycles, so
the NHC forecast lies slightly west of the consensus, and closer to
the ECMWF that has been more consistent over the past few runs.
Given the large spread in the guidance later in the period, the
confidence in the track forecast after 48 hours remains low.

The 48-hour forecast track and wind radii are very close to the
southern tip of the Baja California peninsula. However, with the
persistent westward shifts in the guidance, a tropical storm watch
does not appear to be needed at this time. We will assess future
model trends for the possibility of a watch issuance later tonight
or tomorrow.


FORECAST POSITIONS AND MAX WINDS

INIT 16/0300Z 19.0N 110.2W 65 KT 75 MPH
12H 16/1200Z 19.3N 110.4W 70 KT 80 MPH
24H 17/0000Z 20.0N 110.5W 75 KT 85 MPH
36H 17/1200Z 21.0N 110.9W 75 KT 85 MPH
48H 18/0000Z 22.0N 111.3W 70 KT 80 MPH
72H 19/0000Z 23.7N 112.3W 60 KT 70 MPH
96H 20/0000Z 24.6N 112.6W 45 KT 50 MPH
120H 21/0000Z 25.5N 111.5W 30 KT 35 MPH...INLAND

$$
Forecaster Brown

NNNN
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Re: EPAC: NORMA - Hurricane

#32 Postby Yellow Evan » Sat Sep 16, 2017 9:49 am

ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Hurricane Norma Discussion Number 9
NWS National Hurricane Center Miami FL EP172017
900 AM MDT Sat Sep 16 2017

Norma displayed a large convective band that wrapped most of the way
around the center overnight. This band appears to be fragmenting
this morning, though a new rainband has developed closer to the
center. The Dvorak Current Intensity numbers from both SAB and TAFB
remain 4.0 and thus the maximum winds are kept at 65 kt. However,
the ADT and AMSU estimates are below hurricane force, so my initial
intensity may be somewhat high. An Air Force reconnaissance mission
will be investigating Norma around 20Z, so we should have a more
accurate assessment of the intensity this afternoon.

While the vertical shear is currently low and should remain that way
for the next few days, the hurricane no longer has a well-defined
outflow channel to its south and the upper-level divergence appears
to be less conducive. Additionally, a prominent tongue of dry air
seen in the total precipitable water imagery has wrapped around the
southern semicircle about 200 nm from the center. Model guidance
suggests that the mid-level humidities should dry substantially
while Norma encounters increasingly cooler SSTs during the next few
days. The official intensity forecast shows some slight
intensification followed by a faster decay compared with the
previous advisory. This forecast is based a blend of the LGEM
statistical and HWRF/COAMPS dynamical guidance.

Norma continues to be nearly stationary, though a developing
deep-layer ridge over central Mexico/Gulf of Mexico should begin
moving the hurricane toward the north later today. A motion toward
the north-northwest or northwest should then continue for about
three days. By days 4 and 5, a substantially weaker Norma is
anticipated to meander while located just west of southern Baja
California. The official track forecast is based upon the HFIP
Corrected Consensus Approach and is slightly east of the previous
advisory for the next two days and then about the same thereafter.

FORECAST POSITIONS AND MAX WINDS

INIT 16/1500Z 19.3N 110.1W 65 KT 75 MPH
12H 17/0000Z 19.7N 110.0W 70 KT 80 MPH
24H 17/1200Z 20.8N 110.4W 70 KT 80 MPH
36H 18/0000Z 21.8N 110.8W 65 KT 75 MPH
48H 18/1200Z 22.6N 111.3W 60 KT 70 MPH
72H 19/1200Z 23.5N 112.5W 50 KT 60 MPH
96H 20/1200Z 24.0N 113.0W 35 KT 40 MPH
120H 21/1200Z 24.5N 112.7W 25 KT 30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Landsea

NNNN
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Re: EPAC: NORMA - Troipical Storm

#33 Postby bob rulz » Mon Sep 18, 2017 3:13 am

We went from a potential hurricane hitting Baja California to an insignificant swirl passing far to the west.
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