ATL: IDA - Post Tropical - Discussion

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Re: ATL: IDA - Tropical Storm - Discussion

#121 Postby cycloneye » Mon Sep 21, 2015 3:38 pm

TROPICAL STORM IDA DISCUSSION NUMBER 14
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
500 PM AST MON SEP 21 2015

Satellite data indicate that the low- and mid-level centers of Ida
have become separated, with the low-level center exposed well to the
northwest of the deep convection. This appears to be the result
of some unanticipated mid-level shear that is occurring below the
typical 200 mb outflow layer. The latest TAFB Dvorak classification
and objective ADT estimates from UW/CIMSS support an initial
intensity of 40-45 kt, and based on the earlier ASCAT data the
advisory wind speed is held at 45 kt, although this could be
generous. The forecast upper-level wind pattern over the next
couple of days, which features continued mid-level shear along
with an increase in upper-level northwesterly winds, should prevent
strengthening. In fact, Ida could weaken during the next 2-3 days,
and perhaps not survive as a tropical cyclone. The NHC forecast
assumes that Ida will maintain tropical cyclone status, and that
upper-level winds will become a little more conducive for
strengthening by late in the period. The updated NHC intensity
forecast is lower than the previous one, but still shows some
increase in strength at 96 and 120 h.

Ida continues to move north-northwestward, but recent visible
satellite imagery suggest that the forward speed is decreasing.
The track forecast reasoning remains unchanged from the previous
advisory. The steering currents around the tropical storm are
expected to weaken very soon, and Ida is expected to meander
eastward or east-southeastward over the next couple of days. After
that time, Ida should begin a northwestward or north-northwestward
motion as a mid- to upper-level trough lifts out to the northeast.
The track guidance has become quite divergent this cycle with very
large spread between a faster and more eastward ECMWF solution, and
a slower and more westward GFS track. For now, the official
forecast is near the middle of the guidance envelope, closest to
the GFS ensemble mean and FSU Superensemble.

FORECAST POSITIONS AND MAX WINDS

INIT 21/2100Z 21.2N 48.8W 45 KT 50 MPH
12H 22/0600Z 21.6N 48.7W 45 KT 50 MPH
24H 22/1800Z 21.6N 48.1W 45 KT 50 MPH
36H 23/0600Z 21.1N 47.3W 45 KT 50 MPH
48H 23/1800Z 20.8N 46.7W 45 KT 50 MPH
72H 24/1800Z 21.5N 46.8W 45 KT 50 MPH
96H 25/1800Z 23.0N 47.8W 50 KT 60 MPH
120H 26/1800Z 25.0N 48.5W 55 KT 65 MPH

$$
Forecaster Brown
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#122 Postby TheStormExpert » Mon Sep 21, 2015 4:20 pm

:uarrow: No longer forecasting hurricane strength I see.
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#123 Postby Hammy » Mon Sep 21, 2015 4:43 pm

I think the GFS runs from several days ago likely got it right, it'll interact too much with ex-TD9 to do much beyond this point.
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#124 Postby weathernerdguy » Mon Sep 21, 2015 5:46 pm

is there any chance that a LLC will form under the convection that is SE of the current LLC>
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#125 Postby cycloneye » Mon Sep 21, 2015 9:50 pm

TROPICAL STORM IDA DISCUSSION NUMBER 15
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
1100 PM AST MON SEP 21 2015

Ida's cloud pattern has become increasingly disorganized. Satellite
data indicate that the large separation between the cyclone's low-
to mid-level centers persists as a result of a strong west-
northwesterly shear. The nearest deep convection, coincident with
the mid-level center, remains well removed to the southeast. The
initial wind speed is conservatively lowered to 40 kt and is above
the latest Dvorak intensity estimates.

The tail of a large mid- to upper-level trough over the eastern
Atlantic is forecast to sweep southward over Ida during the next 24
hours. Even stronger deep-layer northwesterly shear and confluence
aloft associated with this feature should adversely affect the storm
during the next few days, and cause weakening. One could envision
Ida not surviving such a greatly inhospitable environment. However,
global models depict Ida remaining a coherent feature and eventually
re-strengthening, though Ida's forecast intensification occurs in
different ways. The ECMWF has consistently shown Ida re-
strengthening, seemingly as a consequence of baroclinic forcing from
the trough interaction. Such an interaction could potentially
result in Ida's taking on the characteristics of a hybrid cyclone.
The GFS shows Ida becoming disentangled from the trough, and
re-intensifying after the trough lifts out. Regardless of which
scenario occurs, any re-strengthening of Ida as a tropical cyclone
would likely be tempered by substantially drier air on the backside
of the trough being entrained by the cyclone. The new intensity
forecast is lower than the previous one in the short term due to the
overall harsh environment affecting the storm. A modest increase in
strength is shown at the end of the forecast, similar to the
previous forecast.

The definition of Ida's center has been deteriorating, and it has
thus become harder to track. It appears though the the cyclone's
forward speed has been decreasing, and the initial motion estimate
is an uncertain 340/04. The deep layer west-northwesterly to
northwesterly flow, associated with the trough overtaking Ida, could
impart a slow eastward or east-southeastward motion for a couple of
days. After that, the bulk of the track guidance shows Ida caught
between two mid-level ridges, which should induce a north-
northwestward and then northward motion at a gradually increasing
forward speed. Only the GFS shows Ida encountering a blocking ridge
with a track much farther to the west, a solution very different
than its ensemble mean. The new track has been adjusted somewhat to
the east overall through 72 hours and is a little faster than the
previous one, in good agreement with a model consensus without the
GFS.


FORECAST POSITIONS AND MAX WINDS

INIT 22/0300Z 21.7N 49.5W 40 KT 45 MPH
12H 22/1200Z 21.9N 49.3W 40 KT 45 MPH
24H 23/0000Z 21.5N 48.4W 35 KT 40 MPH
36H 23/1200Z 20.9N 47.5W 35 KT 40 MPH
48H 24/0000Z 20.9N 46.9W 35 KT 40 MPH
72H 25/0000Z 22.3N 47.1W 40 KT 45 MPH
96H 26/0000Z 24.4N 48.2W 45 KT 50 MPH
120H 27/0000Z 26.2N 48.9W 50 KT 60 MPH

$$
Forecaster Kimberlain
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Re: ATL: IDA - Tropical Storm - Discussion

#126 Postby NDG » Mon Sep 21, 2015 10:44 pm

Yet another storm that the Euro was being too bullish forecasting it to become a major hurricane by the end of the week.
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#127 Postby cycloneye » Tue Sep 22, 2015 4:43 am

TROPICAL STORM IDA DISCUSSION NUMBER 16
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
500 AM AST TUE SEP 22 2015

Shortwave infrared satellite imagery indicates that Ida's low-level
circulation center is now moving or developing east-southeastward
closer to the large mass of deep convection that has been persisting
in the southeastern portion of the larger circulation. The initial
intensity is being maintained at 40 kt, especially now that the
low-level center has moved closer to the mid- and upper-level
circulations as seen in microwave and conventional satellite images.
This intensity is supported by a Dvorak current intensity estimate
of T3.0/45 kt from TAFB.

The initial motion estimate is now 105/04 kt. The recent and much
anticipated turn to the east-southeast appears to have occurred
either due to actual storm motion or due to redevelopment of the
low-level center closer to the strong convection. Regardless of the
cause in the Ida's recent motion change, the global and regional
models are in very good agreement on a continued general slow motion
toward the east for the next 48 hours or so as the southern portion
of a large mid- to upper-level trough moves across and captures the
cyclone. By 72 hours, the trough lifts out to the northeast and
releases Ida, allowing the cyclone to move slowly toward the
northwest by day 4 and toward the north on day 5. As would be
expected in such a weak flow regime, the model guidance is widely
divergent after 72 hours with the UKMET, HWRF, and NAVGEM models
taking Ida more toward the west-northwest, whereas the GFS, ECMWF,
GFDL, and Canadian models take Ida more toward the northwest and
north. The one thing that the all of the models do agree on,
however, is that Ida is not expected move very quickly during the
next 5 days. The NHC track forecast is similar to but slower than
the previous advisory track, and lies close to a blend of the
consensus models TCVA and GFEX.

Given the uncertainty in exactly when and where the low-level center
of Ida will move underneath the mid/upper-level circulation due to
fluctuations in the deep-layer vertical shear profiles during the
next 3 days, the intensity forecast calls for no significant
changes in the strength of the cyclone during that time. By days 4
and 5, however, some gradual strengthening is expected as the
vertical shear abates somewhat while Ida is moving over 29C
sea-surface temperatures. The official intensity forecast is similar
to the previous advisory, and closely follows the IVCN intensity
consensus model.

FORECAST POSITIONS AND MAX WINDS

INIT 22/0900Z 21.3N 48.6W 40 KT 45 MPH
12H 22/1800Z 21.3N 48.1W 40 KT 45 MPH
24H 23/0600Z 20.9N 47.3W 40 KT 45 MPH
36H 23/1800Z 20.6N 46.7W 40 KT 45 MPH
48H 24/0600Z 20.8N 46.4W 40 KT 45 MPH
72H 25/0600Z 22.0N 46.7W 40 KT 45 MPH
96H 26/0600Z 23.0N 48.0W 45 KT 50 MPH
120H 27/0600Z 25.2N 48.5W 50 KT 60 MPH

$$
Forecaster Stewart
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Re: ATL: IDA - Tropical Storm - Discussion

#128 Postby EquusStorm » Tue Sep 22, 2015 7:21 am

Aaaaand the ENFDISTSS* continues to crush my hopes for a hurricane-intensity fish-tickler for the month of September. Looked so impressive then decapitated itself. This year's ACE is going to be pretty pitiful I think, but hey, it's always amusing to see a tropical storm drifting freakin' southeast in the deep tropics. Still holding out a little hope that by Day 5 and beyond it finds a little window of opportunity to intensify, but really, given this season, I'm not entirely confident it will even survive that long.

That said... the latest advisory seems to indicate that the centers are trying to realign a bit, so maybe we'll see this thing survive for a good little while after all.

*El Nino fueled deluxe industrial strength tropical storm-shredder.
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...but still, though, a lot more interesting than the 2013 season.

Not a meteorologist, in fact more of an idiot than anything. You should probably check with the NHC or a local NWS office for official information.

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Re: ATL: IDA - Tropical Storm - Discussion

#129 Postby Sanibel » Tue Sep 22, 2015 11:05 am

When is the last time you saw a system stall and spin in the middle of the formation zone?
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Re: ATL: IDA - Tropical Storm - Discussion

#130 Postby supercane » Tue Sep 22, 2015 11:14 am

000
WTNT45 KNHC 221433
TCDAT5

TROPICAL STORM IDA DISCUSSION NUMBER 17
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
1100 AM AST TUE SEP 22 2015

Ida continues to be a sheared cyclone with the low-level center
located to the northwest of an area of very deep convection. The
upper-level outflow in the southern half of the cyclone has become
better defined since yesterday, but it is not existent elsewhere.
Dvorak numbers are decreasing and do not support 40 kt at this
time. However, I would wait for scatterometer or any other data, if
available, to reduce the winds, if necessary.

The cyclone is embedded within an uncommon flow pattern. It is
located at the southern end of a mid-level trough, which is forcing
the cyclone to move east-southeastward at about 7 kt, and also
causing shear. The evolution of this trough will be crucial for the
future of Ida. Unanimously, global models keep the cyclone drifting
generally eastward for the next 2 days or so, while embedded within
the trough. After that time, all models forecast the trough to lift
out, leaving Ida south of an amplifying ridge. This forecast pattern
should result in a decrease of the shear with favorable conditions
for strengthening, and a slow motion of the cyclone toward the
north-northwest. It is interesting to note the current agreement of
all global models with this scenario, and at long range, the GFS and
ECMWF primarily forecast a significant strengthening of Ida. Given
the uncommon pattern and the currently hostile environment, the NHC
forecast keeps the cyclone with the same intensity for the next day
or two, and allows for some intensification once Ida becomes
detached from the trough. The NHC track forecast is in the middle of
the guidance envelope, and follows the trend of the ECMWF and GFS
consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 22/1500Z 20.5N 47.5W 40 KT 45 MPH
12H 23/0000Z 20.5N 47.0W 40 KT 45 MPH
24H 23/1200Z 20.5N 46.3W 40 KT 45 MPH
36H 24/0000Z 20.0N 45.5W 40 KT 45 MPH
48H 24/1200Z 20.5N 45.0W 40 KT 45 MPH
72H 25/1200Z 22.0N 45.5W 45 KT 50 MPH
96H 26/1200Z 23.5N 46.5W 50 KT 60 MPH
120H 27/1200Z 25.5N 47.0W 55 KT 65 MPH

$$
Forecaster Avila
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#131 Postby cycloneye » Tue Sep 22, 2015 3:36 pm

TROPICAL STORM IDA DISCUSSION NUMBER 18
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
500 PM AST TUE SEP 22 2015

The low-level center of Ida has been placed in the middle of a gyre
defined by several small vortices. The cyclone is still sheared with
the strongest convection located within a cyclonically- curved band
to the south of the center. Given the lack of scatterometer data,
and little change in the satellite presentation, the initial
intensity is kept at 40 kt.

Ida is embedded within the southern end of a mid-level trough, which
is forcing the cyclone to drift east-southeastward at about 4 kt,
and is also causing shear over the cyclone. The evolution of this
trough will be crucial for the future of Ida. Global models indicate
that Ida will drift generally eastward embedded in the trough for
the next 48 hours. After that time, most of the models lift the
trough out, leaving Ida south of an amplifying ridge. This long
range forecast pattern should result in the cyclone turning toward
the north-northwest as indicated in the NHC forecast, and also a
decrease of the shear with favorable conditions for strengthening.
Since the environment is currently quite hostile, no important
change in intensity is indicated during the next 3 days. By the end
of the forecast period, when the cyclone becomes detached from the
trough, some slight increase in strength is forecast.

The NHC track forecast continues to be in the middle of the guidance
envelope, and is very close to the ECMWF and GFS consensus. If the
global models are correct, Ida will be meandering over the Atlantic
for several more days.

FORECAST POSITIONS AND MAX WINDS

INIT 22/2100Z 20.5N 47.8W 40 KT 45 MPH
12H 23/0600Z 20.2N 47.2W 40 KT 45 MPH
24H 23/1800Z 20.0N 46.5W 40 KT 45 MPH
36H 24/0600Z 20.0N 46.0W 40 KT 45 MPH
48H 24/1800Z 20.5N 45.5W 40 KT 45 MPH
72H 25/1800Z 22.5N 45.7W 40 KT 45 MPH
96H 26/1800Z 24.5N 47.0W 50 KT 60 MPH
120H 27/1800Z 26.5N 46.5W 55 KT 65 MPH

$$
Forecaster Avila
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Re: ATL: IDA - Tropical Storm - Discussion

#132 Postby 404UserNotFound » Tue Sep 22, 2015 5:58 pm

Sanibel wrote:When is the last time you saw a system stall and spin in the middle of the formation zone?

Lisa 2010, and that even went east near Cape Verde.
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Re: ATL: IDA - Tropical Storm - Discussion

#133 Postby hurricanehunter69 » Tue Sep 22, 2015 9:02 pm

That ULL is moving away. Ida may finally have a chance to generate some ACE? http://www.ssd.noaa.gov/goes/east/tatl/flash-wv.html
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Re: ATL: IDA - Tropical Storm - Discussion

#134 Postby cycloneye » Tue Sep 22, 2015 9:52 pm

TROPICAL STORM IDA DISCUSSION NUMBER 19
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
1100 PM AST TUE SEP 22 2015

Last-light visible imagery, microwave imagery, and a timely ASCAT
pass around 00Z showed that the center of Ida is located on the
northeastern side of the larger gyre seen earlier today, just west
of a new burst of deep convection. This structure is consistent with
the 30 kt of westerly shear seen in UW-CIMSS satellite analyses. The
initial intensity is set to 35 kt based on data from the ASCAT pass
and in agreement with the latest Dvorak classification from TAFB.
Little change in intensity is expected during the next 48 hours,
with moderate to strong shear forecast to continue. By 72 hours the
shear decreases a bit, which should allow for a little
strengthening. The new NHC intensity forecast is close to a blend of
the latest SHIPS, LGEM, and HWRF models.

The initial position results in a relocation of the center to the
northeast of the previous advisory with a slow east-southeastward
drift as the initial motion. Ida is currently embedded in the base
of a mid-latitude trough which should result in a continued slow
east-southeastward motion during the next day or so followed by a
gradual turn toward the northeast and then the north by 48 hours as
the trough moves away. A slightly faster north-northwestward motion
is forecast at days 3 through 5 as a mid-level ridge builds to the
north of the tropical cyclone. During the latter portion of the
forecast period much of the guidance has shifted westward, now
showing a weaker Ida remaining south of the mid-latitude westerlies
through day 5. The NHC track during this time has been nudged to
the left of the previous one adjusted for the initial position.
However, out of respect for continuity the NHC forecast remains
close to the ECMWF on the eastern side of the guidance envelope and
is well right of the consensus aids. Given the large shift in the
guidance this cycle, confidence is quite low in the track forecast
late in the period.

FORECAST POSITIONS AND MAX WINDS

INIT 23/0300Z 20.9N 46.8W 35 KT 40 MPH
12H 23/1200Z 20.7N 46.4W 35 KT 40 MPH
24H 24/0000Z 20.5N 45.8W 35 KT 40 MPH
36H 24/1200Z 21.0N 45.3W 35 KT 40 MPH
48H 25/0000Z 21.6N 45.1W 35 KT 40 MPH
72H 26/0000Z 23.0N 45.5W 40 KT 45 MPH
96H 27/0000Z 25.0N 46.5W 45 KT 50 MPH
120H 28/0000Z 26.0N 47.0W 50 KT 60 MPH

$$
Forecaster Brennan
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#135 Postby Hammy » Tue Sep 22, 2015 11:02 pm

Second ASCAT pass that likely came in after the advisory indicates it's still 40kts.
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Re: ATL: IDA - Tropical Storm - Discussion

#136 Postby Hurricaneman » Tue Sep 22, 2015 11:03 pm

Its still sheared something aweful
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#137 Postby Alyono » Tue Sep 22, 2015 11:34 pm

do not expect this to crank up significant ace. We may very well have a weakening system during the next several days that dissipates by the weekend. Globals are far less aggressive with this
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#138 Postby Hammy » Wed Sep 23, 2015 1:35 am

Euro continues to show intensification, GFS shows dissipation--I think this could be a good test to see which model does better since the two are showing significantly different solutions now.
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Re: ATL: IDA - Tropical Storm - Discussion

#139 Postby cycloneye » Wed Sep 23, 2015 4:45 am

TROPICAL STORM IDA DISCUSSION NUMBER 20
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
500 AM AST WED SEP 23 2015

Shortwave infrared satellite imagery and a 0413 UTC GCOM microwave
pass suggest that multiple low-level swirls are revolving around
Ida's center, which has been fixed to the west-northwest of an
ongoing burst of deep convection. This pattern is the consequence
of 30 kt of west-northwesterly shear, as analyzed by UW-CIMSS.
Maximum winds remain 35 kt based on earlier ASCAT data, and it
appears that Ida's intensity probably won't change much during the
next couple of days. Vertical shear is forecast to gradually
weaken, but it likely won't fall to less than 15 kt for at least
another 48 hours. Some strengthening is possible beginning on day
3 once the shear has decreased. With the exception of the GFDL,
the intensity models are in close agreement through day 4, with
some more spread by day 5. Based on this latest guidance, no
changes were made to the previous NHC intensity forecast for this
advisory.

Although Ida's exact center is difficult to locate, the entire
circulation has seemingly been drifting southward since the previous
advisory. This is probably for good reason, as Ida is embedded
within northerly flow near the base of a mid-tropospheric trough
which stretches across the eastern Atlantic. The estimated initial
motion is 180/2 kt, but Ida will likely gain an eastward component
soon while being tugged by the eastern Atlantic trough. The
subtropical ridge is expected build westward over the eastern
Atlantic by 48 hours, which should impart a slightly faster
northward motion through the end of the forecast period. The
spread in the 00 UTC track guidance decreased on this forecast
cycle compared to earlier runs, with the UKMET model being the only
obvious outlier. Given the tight clustering, the NHC official
track forecast was again adjusted westward, mainly on days 3-5,
and lies very close to the various multi-model consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT 23/0900Z 20.4N 47.2W 35 KT 40 MPH
12H 23/1800Z 20.4N 46.3W 35 KT 40 MPH
24H 24/0600Z 20.5N 45.8W 35 KT 40 MPH
36H 24/1800Z 21.0N 45.7W 35 KT 40 MPH
48H 25/0600Z 21.7N 45.9W 35 KT 40 MPH
72H 26/0600Z 23.0N 47.0W 40 KT 45 MPH
96H 27/0600Z 25.0N 47.5W 45 KT 50 MPH
120H 28/0600Z 26.0N 47.0W 50 KT 60 MPH

$$
Forecaster Berg
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#140 Postby Alyono » Wed Sep 23, 2015 6:35 am

looking at visible, this may be a remnant low now
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