ATL: IAN - Post-Tropical - Discussion

[cycloneye]

 https://twitter.com/philklotzbach/status/775313445247778817

[AutoPenalti]

Lol naked swirl alert. And a westward projection too.

[abajan]

Can anyone explain this 94LINVEST.25kts-1010mb-132N-450W.100pc.jpg
Has the tropical wave designated invest 94L been re positioned

What's the full URL of that image? It's not loading in my browser. It should start with http or ftp or something like that.

[colbroe]

http://www.nrlmry.navy.mil/tcdat/tc16/A ... .100pc.jpg

[abajan]

http://www.nrlmry.navy.mil/tcdat/tc16/ATL/94L.INVEST/vis/geo/1km_zoom/20160912.1215.msg3.x.vis1km_high.94LINVEST.25kts-1010mb-132N-450W.100pc.jpg

Good question. I have no idea why the image is of that area.

[abajan]

...
We're definitely feeling the effects of its location. It's dead calm here in the southwest of the island and we just had a fairly heavy shower. I'm guessing parts of the island will get afternoon thunderstorms. The same would apply to the other islands in the Lesser Antilles.

It's actually intermittently calm. Currently, the winds are normal.

[wxman57]

Model data now say "Ian".

TROPICAL CYCLONE GUIDANCE MESSAGE
NWS NATIONAL HURRICANE CENTER MIAMI FL
1336 UTC MON SEP 12 2016

DISCLAIMER...NUMERICAL MODELS ARE SUBJECT TO LARGE ERRORS.
PLEASE REFER TO NHC OFFICIAL FORECASTS FOR TROPICAL CYCLONE
AND SUBTROPICAL CYCLONE INFORMATION.

ATLANTIC OBJECTIVE AIDS FOR

TROPICAL CYCLONE IAN (AL102016) 20160912 1200 UTC

...00 HRS... ...12 HRS... ...24 HRS... ...36 HRS...
160912 1200 160913 0000 160913 1200 160914 0000

LAT LON LAT LON LAT LON LAT LON
BAMS 21.4N 50.0W 22.7N 51.6W 23.7N 52.7W 24.7N 53.5W
BAMD 21.4N 50.0W 24.2N 50.7W 27.2N 51.1W 30.1N 51.8W
BAMM 21.4N 50.0W 23.4N 51.0W 25.2N 51.7W 27.2N 52.5W
LBAR 21.4N 50.0W 23.4N 51.0W 25.4N 51.8W 27.1N 52.8W
SHIP 35KTS 35KTS 35KTS 36KTS
DSHP 35KTS 35KTS 35KTS 36KTS

[cycloneye]

BULLETIN
TROPICAL STORM IAN ADVISORY NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016
1100 AM AST MON SEP 12 2016

...NINTH TROPICAL STORM OF THE SEASON FORMS OVER THE ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...21.8N 50.4W
ABOUT 1140 MI...1840 KM SE OF BERMUDA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES


WATCHES AND WARNINGS
--------------------
There are no coastal watches or warnings in effect.


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 1100 AM AST (1500 UTC), the center of Tropical Storm Ian was
located near latitude 21.8 North, longitude 50.4 West. Ian is
moving toward the northwest near 13 mph (20 km/h) and a turn toward
the north-northwest is expected over the next day or so. On the
forecast track, the center will continue to move over the Central
Atlantic through Tuesday.

Maximum sustained winds are near 40 mph (65 km/h) with higher gusts.
Little change in strength is expected during the next day or so.
Some slight strengthening is possible beginning Tuesday night.

Tropical-storm-force winds extend outward up to 140 miles (220 km)
from the center.

The estimated minimum central pressure is 1007 mb (29.74 inches).
is 1007 mb (29.74 inches).


HAZARDS AFFECTING LAND
----------------------
None.


NEXT ADVISORY
-------------
Next complete advisory at 500 PM AST.

$$
Forecaster Pasch



TROPICAL STORM IAN DISCUSSION NUMBER 1
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016
1100 AM AST MON SEP 12 2016

Visible satellite images and a recent ASCAT overpass show
that the low pressure system over the central Atlantic has now
acquired a well-defined low-level circulation. The scatterometer
data showed tropical-storm-force winds over the northern semicircle
of the circulation, and the advisory intensity is set to 35 kt.
Ian is not a well organized storm, with the low-level center
exposed and displaced about 70 n mi to the southwest of the main
area of deep convection. This is due to the effect of about 20 kt
of vertical shear over the system, and this strong shear is
predicted to persist for at least the next day or so. In 36 to 48
hours, the shear is forecast to relax somewhat, so some slow
intensification could begin by tomorrow night. The official
intensity forecast is a little above the model consensus. In 120
hours, or sooner, the system should become embedded within a
frontal zone over north Atlantic and lose tropical characteristics.

Ian is moving northwestward, with initial motion estimated to be
about 320/11 kt. The storm is currently moving through a break in
the subtropical ridge. In the next few days, a 500 mb trough
approaching from the west should cause Ian to turn northward and
then north-northeastward while accelerating. The official forecast
track leans toward the ECMWF solution, but is also not far from the
latest dynamical model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 12/1500Z 21.8N 50.4W 35 KT 40 MPH
12H 13/0000Z 23.4N 51.2W 35 KT 40 MPH
24H 13/1200Z 25.4N 52.4W 35 KT 40 MPH
36H 14/0000Z 27.3N 53.6W 40 KT 45 MPH
48H 14/1200Z 29.7N 54.8W 45 KT 50 MPH
72H 15/1200Z 34.5N 53.8W 50 KT 60 MPH
96H 16/1200Z 42.5N 45.5W 50 KT 60 MPH
120H 17/1200Z 53.0N 32.0W 50 KT 60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch

[cycloneye]

We have IAN.

...NINTH TROPICAL STORM OF THE SEASON FORMS OVER THE ATLANTIC...


SUMMARY OF 1100 AM AST...1500 UTC...INFORMATION
-----------------------------------------------
LOCATION...21.8N 50.4W
ABOUT 1140 MI...1840 KM SE OF BERMUDA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NW OR 320 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES

[HurricaneRyan]

So it's not expected to become a hurricane at all?

[znel52]

Surprised they pulled the trigger on this. Looks horrible.

[Ntxw]

So it's not expected to become a hurricane at all?

Currently a naked swirl with convection sheared to the north and east side. Conditions don't get much better meanwhile.

[tarheelprogrammer]

Actually looks pretty good for a storm in the Atlantic in recent years....

[Kazmit]

Expected to peak at 60mph. Not bad for these conditions.

[Nimbus]

Ian can use up as much of that warm water as it wants, next wave looks like a fish as well.
May not be that bad a season after all.

[cycloneye]

BULLETIN
TROPICAL STORM IAN ADVISORY NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016
500 PM AST MON SEP 12 2016

...IAN MOVING OVER THE OPEN WATERS OF THE ATLANTIC WITH NO CHANGE
IN STRENGTH...


SUMMARY OF 500 PM AST...2100 UTC...INFORMATION
----------------------------------------------
LOCATION...22.9N 50.7W
ABOUT 1080 MI...1735 KM ESE OF BERMUDA
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1007 MB...29.74 INCHES


TROPICAL STORM IAN DISCUSSION NUMBER 2
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016
500 PM AST MON SEP 12 2016

Ian remains poorly organized, with the bulk of the deep convection
displaced well to the northeast of the low-level center due to
strong vertical shear. The advisory intensity estimate remains at
35 kt in agreement with a Dvorak estimate from TAFB. The global
models suggest that some decrease in shear will occur in 36 to 48
hours, when the system moves on the northeast side of a partially
cut off upper-level cyclone. This could permit a little
strengthening to commence around that time, as reflected in the
official forecast. This is slightly above the latest numerical model
intensity consensus. By the end of the forecast period, or sooner,
Ian should become embedded in a frontal zone over the north Atlantic
and be transformed into an extratropical cyclone.

Ian has turned to the right, and the initial motion estimate is now
about 330/11 kt. The storm continues to move through a break in
the subtropical ridge, and in a few days the flow ahead of a
mid-tropospheric trough should cause Ian to accelerate
north-northeastward to northeastward. The official forecast lies
between the latest GFS and ECMWF predictions, and is also close to
the dynamical model consensus.

FORECAST POSITIONS AND MAX WINDS

INIT 12/2100Z 22.9N 50.7W 35 KT 40 MPH
12H 13/0600Z 24.3N 51.7W 35 KT 40 MPH
24H 13/1800Z 26.2N 52.9W 35 KT 40 MPH
36H 14/0600Z 28.5N 54.0W 40 KT 45 MPH
48H 14/1800Z 30.7N 54.5W 45 KT 50 MPH
72H 15/1800Z 35.7N 52.4W 50 KT 60 MPH
96H 16/1800Z 45.0N 42.0W 50 KT 60 MPH
120H 17/1800Z 54.5N 29.0W 50 KT 60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Pasch

[cycloneye]

TROPICAL STORM IAN DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016
1100 PM AST MON SEP 12 2016

Ian remains a sheared tropical cyclone, with the strongest
convection displaced to the northeast and east of the center.
However, moderate convection has recently developed over and just
north of the center due to the vertical wind shear's backing
from a southwesterly to southerly direction. Data from a recent
partial ASCAT-B overpass indicate that the 34-kt wind field has
expanded to at least 200 nmi in the northeastern quadrant, and that
peak winds have also increased to more than 35 kt. Dvorak satellite
intensity estimates are T3.0/45 kt from TAFB and T2.5/35 kt from
SAB, and an average of these values yields an advisory intensity of
40 kt.

Ian has maintained a steady motion of 330/11 kt. The latest NHC
model guidance is in excellent agreement on the storm continuing to
move north-northwestward through a break in the Bermuda-Azores High
for the next 24 hours, followed by a turn to the north at 36-48
hours. After that, Ian is expected to gradually accelerate as the
cyclone gets captured by a strong mid-latitude shortwave trough. The
new official forecast track is essentially just an update of the
previous advisory track and lies close to the GFS-ECMWF model
consensus, and the multi-model consensus TVCN.

The vertical shear is forecast to decrease to 15-20 kt in 36 to 48
hours when an upper-level low, currently located about 400 nmi
northwest of the cyclone, is forecast by the GFS, UKMET, and ECMWF
models to move over and become colocated with Ian's low-level
center. The combination of decreasing vertical wind shear and some
infusion of baroclinic energy associated with this complex
interaction is expected to produce at least some slight
strengthening by days 2-3. Around 120 hours, Ian is forecast to
interact with a frontal zone over the north Atlantic and be
transformed into an extratropical cyclone.

FORECAST POSITIONS AND MAX WINDS

INIT 13/0300Z 23.5N 51.5W 40 KT 45 MPH
12H 13/1200Z 24.9N 52.4W 40 KT 45 MPH
24H 14/0000Z 26.9N 53.4W 40 KT 45 MPH
36H 14/1200Z 29.4N 54.1W 45 KT 50 MPH
48H 15/0000Z 31.8N 54.0W 50 KT 60 MPH
72H 16/0000Z 38.0N 49.7W 50 KT 60 MPH
96H 17/0000Z 48.0N 38.0W 50 KT 60 MPH
120H 18/0000Z 56.5N 25.2W 50 KT 60 MPH...POST-TROP/EXTRATROP

$$
Forecaster Stewart

[Ptarmigan]

With all these fish storms, we could rack up accumulated cyclone energy.

[Ntxw]

Ian isn't going to add much units. He's close to high shear and is still partially a naked swirl. I think this system will add less than 5 units, possibly less than 3.

[arlwx]

TROPICAL STORM IAN DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102016
500 AM AST TUE SEP 13 2016

Ian is a strongly sheared tropical storm. The low-level center of
the cyclone is completely exposed with the main area of deep
convection located about 120 n mi northeast of the center. This
asymmetric cloud pattern is the result of about 30 kt of
southwesterly vertical wind shear. The initial intensity is held
at 40 kt for this advisory, in agreement with the earlier ASCAT
data. This estimate is a little higher than the latest Dvorak
classifications.

Satellite fixes indicate that Ian has slowed down during the last
several hours. The initial motion estimate, using a 12-h average,
is 335/8 kt. The tropical cyclone is situated between a mid- to
upper-level low to its west and a mid-level high to its east. This
pattern is expected to persist for the next couple of days, and
should cause Ian to move north-northwestward to northward with a
slight increase in forward speed. After that time, a shortwave
trough is expected to approach the tropical storm, and it will
likely cause Ian to turn northeastward and accelerate as it becomes
embedded in the mid-latitude flow. The models are in fair agreement
in this overall scenario, and only small changes were made to the
previous NHC track forecast. This prediction is in best agreement
with the various consensus aids.

The strong shear currently affecting Ian is expected to persist for
another 24 hours, so little change in strength is predicted during
that time. The shear is forecast to lessen some in a couple of days
while Ian is still over warm water. These environmental conditions,
combined with some baroclinic forcing, could allow for slight
strengthening in the 36- to 72-h time period. After that time, Ian
is expected to move back into a strong shear environment and over
progressively colder water, which should lead to extratropical
transition in about 4 days. The NHC intensity forecast is largely
the same as the previous one, and is in best agreement with the
SHIPS guidance during its tropical phase and the global models
during the extratropical portion.

FORECAST POSITIONS AND MAX WINDS

INIT 13/0900Z 24.0N 51.7W 40 KT 45 MPH
12H 13/1800Z 25.4N 52.5W 40 KT 45 MPH
24H 14/0600Z 27.8N 53.4W 40 KT 45 MPH
36H 14/1800Z 30.4N 53.8W 45 KT 50 MPH
48H 15/0600Z 33.2N 53.1W 50 KT 60 MPH
72H 16/0600Z 40.7N 46.1W 50 KT 60 MPH
96H 17/0600Z 50.7N 32.0W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 18/0600Z 58.5N 18.5W 45 KT 50 MPH...POST-TROP/EXTRATROP