ATL: GERT - Post-Tropical - Discussion

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Re: ATL: EIGHT - Tropical Depression - Discussion

#1321 Postby cycloneye » Sat Aug 12, 2017 9:45 pm

BULLETIN
Tropical Depression Eight Advisory Number 1
NWS National Hurricane Center Miami FL AL082017
1100 PM EDT Sat Aug 12 2017

...DEPRESSION FORMS OVER THE WESTERN ATLANTIC...
...FORECAST TO REMAIN EAST OF THE UNITED STATES...


SUMMARY OF 1100 PM EDT...0300 UTC...INFORMATION
-----------------------------------------------
LOCATION...25.3N 70.3W
ABOUT 260 MI...415 KM NE OF THE SOUTHEASTERN BAHAMAS
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...NNW OR 330 DEGREES AT 13 MPH...20 KM/H
MINIMUM CENTRAL PRESSURE...1011 MB...29.86 INCHES

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


DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
At 1100 PM EDT (0300 UTC), the center of Tropical Depression Eight
was located near latitude 25.3 North, longitude 70.3 West. The
depression is moving toward the north-northwest near 13 mph (20
km/h) and this general motion is expected to continue through
Sunday. A turn toward the north is forecast on Sunday night,
followed by a turn toward the north-northeast on Monday.

Maximum sustained winds are near 35 mph (55 km/h) with higher gusts.
Gradual strengthening is forecast during the next 48 hours, and the
depression is expected to become a tropical storm later tonight or
on Sunday.

The estimated minimum central pressure is 1011 mb (29.86 inches).


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


NEXT ADVISORY
-------------
Next complete advisory at 500 AM EDT.

$$
Forecaster Brown


DDHHMM

Tropical Depression Eight Discussion Number 1
NWS National Hurricane Center Miami FL AL082017
1100 PM EDT Sat Aug 12 2017

Late afternoon GOES-16 visible satellite images showed that the
circulation associated with the low pressure located northeast of
the Bahamas had become better defined. Since that time, the
night-time microphysics RGB product and other infrared satellite
pictures have continued to show an improvement in the circulation,
and recent ASCAT data show that the system has acquired a well-
defined center. Deep convection is organized in a large curved band,
however the center is located near the western edge of the band.
NOAA buoy 41046 located southeast of the center reported 25 to 30 kt
winds earlier this evening, and the scatterometer data support an
initial wind speed of 30 kt.

The depression is moving north-northwestward or 330/11 kt.
The depression should move north-northwestward to northward
around the western side of a deep-layer ridge over the central
Atlantic through Sunday night. It is expected to reach the
mid-latitude westerlies by late Monday and begin to accelerate
northeastward ahead of a short-wave trough that will be approaching
the northeastern United States. The steering currents are well
established over the western Atlantic and the track guidance is in
good agreement on the forecast scenario. The NHC track forecast lies
near the various consensus aids.

The intensity forecast is more problematic. The system is expected
to traverse warm water and remain in a low-shear environment during
the next day or so, but intrusions of dry mid-level air are likely
to limit strengthening. The statistical guidance and the HWRF favor
more significant intensification than the global models, which
generally do not show much deepening. In deference to the global
models, the NHC forecast is below the consensus, especially later in
the period. The system is likely to become extratropical in 3 to 4
days, and the extratropical portion of the forecast is based on
guidance provided by the NOAA Ocean Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT 13/0300Z 25.3N 70.3W 30 KT 35 MPH
12H 13/1200Z 27.0N 71.2W 35 KT 40 MPH
24H 14/0000Z 29.0N 71.9W 40 KT 45 MPH
36H 14/1200Z 30.7N 72.0W 45 KT 50 MPH
48H 15/0000Z 32.2N 71.4W 50 KT 60 MPH
72H 16/0000Z 36.2N 66.9W 55 KT 65 MPH
96H 17/0000Z 41.5N 54.5W 50 KT 60 MPH...POST-TROP/EXTRATROP
120H 18/0000Z 45.5N 39.0W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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Re: ATL: 08L - Tropical Depression - Discussion

#1322 Postby 1900hurricane » Sat Aug 12, 2017 9:47 pm

Yep, looks like ASCAT confirms a 30 kt tropical depression, now designated as 08L.
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1323 Postby weathaguyry » Sat Aug 12, 2017 9:49 pm

WooHoo! TD8!
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1324 Postby Hammy » Sat Aug 12, 2017 9:56 pm

Question to the mets here: is it more likely this strengthens more quickly or slowly than forecast based on the current conditions, since the models aren't particularly helpful at the moment?
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1325 Postby abajan » Sat Aug 12, 2017 10:11 pm

Did this set a record as the longest time as an invest before being upgraded? Sure seems that way.
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1326 Postby galaxy401 » Sat Aug 12, 2017 10:13 pm

abajan wrote:Did this set a record as the longest time as an invest before being upgraded? Sure seems that way.


Hermine last year took 10 days from Invest to being classified.
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ATL: EIGHT - Tropical Depression - Discussion

#1327 Postby NDG » Sat Aug 12, 2017 10:23 pm

Euro once again beats the GFS, though a couple of days ago it dropped development of it for a run or two.
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1328 Postby Hammy » Sat Aug 12, 2017 10:36 pm

NDG wrote:Euro once again beats the GFS, though a couple of days ago it dropped development of it for a run or two.


I remember during 2013-14 (as well as Bill in 2015) the Euro would show something in the medium or long range and then drop it, and it not show up again in the models until a day or two before it developed--quite an odd thing but something the model has a history of at times.
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Re: ATL: EIGHT - Models

#1329 Postby AxaltaRacing24 » Sat Aug 12, 2017 10:37 pm

The GFS still will not develop this TROPICAL DEPRESSION. :na:
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Re: ATL: EIGHT - Models

#1330 Postby caneman » Sun Aug 13, 2017 3:42 am

Obviously the GFS has been having some problems this year. I'm not sure the Euro is performing up to par this year either. Models really seem to be struggling this year or perhaps we've come to expect too much by model watching every hour and every run.
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1331 Postby GCANE » Sun Aug 13, 2017 4:38 am

I know there is some debate as to how accurate GFS is forecasting UL conditions.
I think there is something more going on.
Looking at the latest 200mb vort, there is a rather large PV streamer / anomaly area directly around 08L to its north and west.
This usually inhibits spin up and convection due to sinking air and UL vorts disrupting and tilting LL vorts.
Yet, 08L continues to develop.
Towers have been firing all night.

Image

Image
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1332 Postby GCANE » Sun Aug 13, 2017 4:48 am

Buoy 41047, just northwest of the CoC.
27.520 N 71.530 W (27°31'12" N 71°31'48" W)

Pressure taking a nose dive.

Image

Image
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1333 Postby GCANE » Sun Aug 13, 2017 4:54 am

Mid-level moisture conditions not all that good to develop a warm core.
Will be very interesting to see if it really does.

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Re: ATL: EIGHT - Tropical Depression - Discussion

#1334 Postby NDG » Sun Aug 13, 2017 8:11 am

TD 8 is being affected by northerly shear this morning.


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Re: ATL: EIGHT - Models

#1335 Postby NDG » Sun Aug 13, 2017 8:16 am

caneman wrote:Obviously the GFS has been having some problems this year. I'm not sure the Euro is performing up to par this year either. Models really seem to be struggling this year or perhaps we've come to expect too much by model watching every hour and every run.


At least the Euro has been performing better within 5-7 day range than the GFS, 2 storms in the western Atlantic Basin in a row that the GFS has failed to develop within its 5 day range. The Euro is still struggling a little bit in its 7-10 day range.
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1336 Postby cycloneye » Sun Aug 13, 2017 9:54 am

Tropical Depression Eight Discussion Number 3
NWS National Hurricane Center Miami FL AL082017
1100 AM EDT Sun Aug 13 2017

The overall organization of the depression has changed little this
morning. Visible satellite imagery and NOAA buoy data indicate
that center is located near the northwestern edge of the area of
convective banding. In fact, nearly all of the convective banding
is located over the eastern and southeastern portions of the
circulation. The initial intensity remains 30 kt, which is
supported by subjective Dvorak T-numbers of 2.0 from both TAFB and
SAB.

The depression is moving north-northwestward or 335/11 kt. The
track forecast reasoning remains unchanged. The depression is
forecast to move north-northwestward to northward around the western
portion of a deep-layer subtropical ridge during the next day or
so. After that time, the cyclone is expected to turn northeastward
ahead of a shortwave trough that will be approaching the
northeastern United States. As the southwesterly flow increases
over the western Atlantic ahead of the trough by 72 hours, the
cyclone should begin to accelerate northeastward. The track
guidance is once again in excellent agreement, and only a slight
westward adjustment from the previous forecast was required.

The depression is currently over warm water and within a low
shear environment, but the mid-level atmosphere is relatively dry.
These conditions should allow some modest strengthening during the
next day or so. Vertical shear is forecast to increase by late
Monday, and increase further in 2 to 3 days, which should put an
end to any additional intensification. The system is forecast to
become extratropical in 3 to 4 days, but if it does not strengthen
it could be absorbed by an approaching trough off the Mid-Atlantic
and northeastern U.S. in a few days. The latter portion of the
forecast continues to be based on guidance provided by the NOAA
Ocean Prediction Center.


FORECAST POSITIONS AND MAX WINDS

INIT 13/1500Z 27.4N 71.5W 30 KT 35 MPH
12H 14/0000Z 29.1N 72.2W 35 KT 40 MPH
24H 14/1200Z 30.7N 72.4W 40 KT 45 MPH
36H 15/0000Z 32.5N 71.9W 45 KT 50 MPH
48H 15/1200Z 34.6N 70.5W 50 KT 60 MPH
72H 16/1200Z 39.0N 62.0W 50 KT 60 MPH
96H 17/1200Z 42.5N 49.0W 45 KT 50 MPH...POST-TROP/EXTRATROP
120H 18/1200Z 47.0N 35.0W 45 KT 50 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown
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Re: ATL: EIGHT - Tropical Depression - Discussion

#1337 Postby Steve » Sun Aug 13, 2017 10:21 am

NDG wrote:Euro once again beats the GFS, though a couple of days ago it dropped development of it for a run or two.


CMC destroyed them both. Day after day after day for over a week. Complete destruction and burial.

It might be too far west in the 00z run, but it put it in the right general area and never waivered on development.
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Re: ATL: EIGHT - Models

#1338 Postby Steve » Sun Aug 13, 2017 10:35 am

CMC had it stronger and a bit farther east last Sunday 08/06/17 at 00z (so Saturday a week ago at 7pm Central). Show me a model that had anything close to this. For the Euro Huggers or the GFS defenders, your models were eliminated by the Canadian. Yeah, the Canadian. We knew last year there were some big tweaks, and there was a storm or two it handled well. But this says it all. European came in second of the 3 major globals. It did then didn't then did then didn't then did again show development. But when it did, it was close. GFS was the worst.
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Re: ATL: EIGHT - Models

#1339 Postby RL3AO » Sun Aug 13, 2017 10:38 am

Try to keep more about the model output and less about the model wars.
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Re: ATL: EIGHT - Models

#1340 Postby hurricanehunter69 » Sun Aug 13, 2017 12:43 pm

I am a biased, enthusiastic and aggressive tropical cyclone forecaster, and normally would have bit on forecasting TD8 to become a hurricane. It is because of the GFS that I have laid up on making this potential mistake. The GFS has seemingly forecasted the inhibiting factors well, while the EURO has seemingly forecasted the conducive factors well. A blend of the two is usually the best bet. With a blend of the other major models breaking ties.
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