ATL: IDA - Post Tropical - Discussion

[Steve]

4th or 5th classified this month - but all weak so far. I'm with Hammy in that I didn't see that part of the basin as particularly conducive this year and figured a season centered much more around/near Florida. We have had a lot of surges of energy and tropical moisture but not very much in the way of classified or named action. I wouldn't give up on the Western Caribbean or Gulf yet. Despite shear and occasional convection, those areas are mostly untouched and could still harbor notable activity. I think once we get into Mid October, the season is more likely than not to shut down for the year if it follows some of the seemingly similar El Ninos.

[wxman57]

I think it will become Ida. Can't rule out hurricane intensity. Looks like it's completely a fish storm, though.

[Extratropical94]

10L TEN 150918 1800 13.2N 37.0W ATL 30 1007

Not a storm yet.

[Sanibel]

Good bulky convection but lack of strong organization.

[weathernerdguy]

best track at ts now?

[cycloneye]

best track at ts now?

Not yet.


AL, 10, 2015091900, , BEST, 0, 136N, 373W, 30, 1007, TD

[hurricanehunter69]

This thing looks fairly good and healthy. I'd bet at least tropical storm and add another one of those to the list. Although I feel it has a shot at becoming a hurricane, I'd be hesitant to say so. Considering what happened to depression 9.

[gatorcane]

Yes it is looking good and I think it becomes a TS at least, maybe a hurricane too.

[weathernerdguy]

finally a storm that isn't racing the Atlantic and hitting into a shear wall.

[cycloneye]

We have IDA!

BULLETIN
TROPICAL STORM IDA ADVISORY NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
1100 PM AST FRI SEP 18 2015

...TROPICAL STORM IDA FORMS IN THE TROPICAL ATLANTIC...


SUMMARY OF 1100 PM AST...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...13.7N 37.5W
ABOUT 915 MI...1470 KM W OF THE CAPE VERDE ISLANDS
MAXIMUM SUSTAINED WINDS...40 MPH...65 KM/H
PRESENT MOVEMENT...NW OR 305 DEGREES AT 7 MPH...11 KM/H
MINIMUM CENTRAL PRESSURE...1006 MB...29.71 INCHES


TROPICAL STORM IDA DISCUSSION NUMBER 3
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
1100 PM AST FRI SEP 18 2015

The depression's cloud pattern has been increasing in organization.
A primarily convective band over the eastern half of the circulation
has been increasing in curvature and the cloud tops are cooling
significantly. The initial wind speed is increased to 35 kt in
agreement with the latest CI numbers from TAFB and SAB and UW-CIMSS
ADT value.

Westerly shear associated with an upper-level trough, extending
from the eastern subtropical Atlantic into the eastern Caribbean,
could increase over Ida during the next day or so and slow the
cyclone's rate of intensification. Global models agree that a
relative reduction in the shear should occur in 2 to 3 days when a
piece of the upper-level trough cuts off near the Greater Antilles,
which could allow Ida to strengthen, perhaps even more than
forecast. Late in the forecast period, the uncertainty in the
intensity forecast increases considerably, with the ECMWF calling
for more northwesterly shear and less favorable thermodynamic
variables in the storm's environment than in the GFS. The new
intensity forecast is only slightly higher than the previous one
through 72 hours. The forecast after that time is of low confidence
and essentially levels Ida's intensity off in agreement with the
SHIPS model output.

Recent fixes suggest that the cyclone's motion has been more
northwesterly (or 305/06) since earlier today. Ida is being steered
by east-southeasterly to southeasterly flow underneath a subtropical
ridge migrating westward with the cyclone, and some increase in
forward speed is predicted by the models during the next day or so.
In about 48 hours, a deep-layer trough amplifying southwestward
across the eastern Atlantic will cause steering currents surrounding
Ida to collapse, which should result in the cyclone's forward motion
coming to a halt. With increasing northerly or northwesterly flow
aloft, Ida should begin to meander in about 4 days and even
drift southward or southeastward by day 5. The new track forecast
is adjusted to the right some throughout the period, primarily due
to the more northwesterly initial motion but also in the direction
of the multi-model consensus.


FORECAST POSITIONS AND MAX WINDS

INIT 19/0300Z 13.7N 37.5W 35 KT 40 MPH
12H 19/1200Z 14.7N 38.9W 40 KT 45 MPH
24H 20/0000Z 15.8N 40.9W 45 KT 50 MPH
36H 20/1200Z 16.9N 43.2W 50 KT 60 MPH
48H 21/0000Z 18.1N 45.0W 50 KT 60 MPH
72H 22/0000Z 20.1N 47.4W 60 KT 70 MPH
96H 23/0000Z 20.7N 48.0W 55 KT 65 MPH
120H 24/0000Z 20.3N 47.8W 55 KT 65 MPH

$$
Forecaster Kimberlain

NNNN

[Hurricaneman]

This could become a hurricane, something to track that may possibly not be a sheared mess

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[Hammy]

This could become a hurricane, something to track that may possibly not be a sheared mess

There's a tiny glimmer of hope, 0z GFS is showing nearly identical solution to 12z Euro.

[Hurricaneman]

Could be a big ace producer

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

[AutoPenalti]

Some models seem to have it picked up by a trough, and others have it with the ridge building back.

So 50/50 that this can be a threat to anyone in CONUS?

[bahamaswx]

Some models seem to have it picked up by a trough, and others have it with the ridge building back.

So 50/50 that this can be a threat to anyone in CONUS?

Much lower than 50/50 for any storm that far out.

[cycloneye]

TROPICAL STORM IDA DISCUSSION NUMBER 4
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102015
500 AM AST SAT SEP 19 2015

The overall organization of Ida's cloud pattern continues to
increase. Banding features are becoming more prominent in the
southern part of the circulation, with a new band forming on the
west side. In addition, a burst of convection has been ongoing
during the past few hours near the apparent center. Satellite
classifications still support an intensity of 35 kt, and this value
is used as the initial wind speed.

Satellite fixes suggest that the northwestward motion of Ida has
sped up to 9 kt this morning. A mid-level ridge is expected to
remain the dominant steering mechanism for the next couple of days,
causing the storm to move to the west-northwest or northwest during
that time. Models are in good agreement and only a slight
northward adjustment was made to the official forecast then. Beyond
2 days, there is considerable uncertainty on how an amplifying
trough over the east-central Atlantic will affect Ida. The cyclone
seems likely to slow down due to steering currents collapsing, but
there is poor agreement on whether the trough will pick up Ida,
sending the storm east-northeastward, or leave the storm behind. For
example, the normally reliable ECMWF and GFS models are going in
opposite directions at day 5, with the ECMWF favoring a stronger
trough solution while the GFS has Ida missing the trough and
drifting westward. With so much uncertainty, I have elected to show
a stationary Ida after day 3, preferring not to commit to
either solution at this time. This forecast blends the previous
forecast with the model consensus, although leans more heavily on
the former.

While the shear near Ida is low for now, most of the global models
show an increase during the next day or so. This is expected to
somewhat temper future strengthening, although since most of the
other environmental factors are still favorable, a gradual
intensification is forecast. The long-range intensity prediction,
however, is very complex due to the potential interaction of the
trough, which yields very different shear profiles, along with dry
air aloft and possible upwelling of cooler water as Ida moves
slowly. With the track more uncertain than average and these
challenging factors, it seems prudent to remain conservative with
the wind speed forecast. The official intensity forecast is close to
the previous one, which ends up on the low side of the guidance at
days 4/5. It almost goes without saying that these conditions are
leading me to have a rather low confidence in the intensity forecast
at 72 hours and beyond.



FORECAST POSITIONS AND MAX WINDS

INIT 19/0900Z 14.4N 38.5W 35 KT 40 MPH
12H 19/1800Z 15.3N 39.9W 40 KT 45 MPH
24H 20/0600Z 16.5N 42.2W 45 KT 50 MPH
36H 20/1800Z 17.6N 44.0W 50 KT 60 MPH
48H 21/0600Z 18.9N 45.6W 55 KT 65 MPH
72H 22/0600Z 20.5N 47.5W 60 KT 70 MPH
96H 23/0600Z 20.5N 47.5W 55 KT 65 MPH
120H 24/0600Z 20.5N 47.5W 55 KT 65 MPH

$$
Forecaster Blake

[abajan]

Some models seem to have it picked up by a trough, and others have it with the ridge building back.

So 50/50 that this can be a threat to anyone in CONUS?

Much lower than 50/50 for any storm that far out.

I think you mean definitely 50/50 for any storm that far out. In other words, since it's practically impossible to tell if it will be a threat to the CONUS from that distance, the percentage of probability for it to be a threat versus not being one is just about even.

[LarryWx]

Some models seem to have it picked up by a trough, and others have it with the ridge building back.

So 50/50 that this can be a threat to anyone in CONUS?

Much lower than 50/50 for any storm that far out.

I think you mean definitely 50/50 for any storm that far out. In other words, since it's practically impossible to tell if it will be a threat to the CONUS from that distance, the percentage of probability for it to be a threat versus not being one is just about even.

1) abajan,
Based on stats of decades of storms in that area, the chances of it hitting the conus are way under 50% as said by bahamaswx even if ignoring it is already Sep 19.

2) This makes an incredible five TS's E of 50W beating the old record of 3 for a strong Niño year (in 1899).

[gatorcane]

Latest GFS eventually brings this down to 937MB in the long-range.

Based on the latest NHC discussion, I have the feeling they may increase the intensity forecasts as their current weakening forecast is highly uncertain.

[Ntxw]

Ida actually imo doesn't look as good this morning as she did yesterday. Convection has moved off to the south and southeast. Looks like LLC may becoming exposed, usually a sign shear is working it's way in.