ATL: FRED - Post-Tropical - Discussion

[tolakram]

Use shortwave or nighttime microphysics when looking for low level features. What's left of a center appears to be moving off the NW coast. Track the easterly moving clouds near the bottom of the apparent circulation. There was never any chance the old LLC was going to survive, but the overall mid-level motion will. Now we wait to see when convection starts firing north of the island.

https://weather.cod.edu/satrad/?parms=meso-meso1-truecolor-24-0-100-1&checked=map&colorbar=undefined

[ScottNAtlanta]

Ok, who wants to bite on that convective blow up south of Haiti? Anyone?

[Jr0d]

https://weather.cod.edu/satrad/?parms=m ... =undefined

This is good to see low levels at night...looks like what's left of the LLC is emerging off the Northern coast of Haiti.

[skyline385]

The MLC is still hanging behind the island though. With the LLC almost gone, what the chance that the new LLC could form SW of DR/Haiti?

[Dean4Storms]

Going to be nearly impossible for the LLC to survive those mountains but there is still a good amount of vorticity left and with that and the MIMIC TPW2 showing a still organized spin it just needs some time over warm water and it feeds back and the LLC redevelops. I just don't see this going poof with dry air no longer an issue once it gets back over warm SST's and even the westerly shear lighter with the forward speed slowed. Seen this song and dance too many times in the past as many of you guys have.

[Dean4Storms]

https://weather.cod.edu/satrad/?parms=meso-meso1-ntmicro-200-1-10-1&checked=map&colorbar=undefined

This is good to see low levels at night...looks like what's left of the LLC is emerging off the Northern coast of Haiti.

I noticed that spin as well, just lacking any convection for the time being.

[Blown Away]

The MLC is still hanging behind the island though. With the LLC almost gone, what the chance that the new LLC could form SW of DR/Haiti?

Who knows, there are weak vortices spinning all over the place...

IMO, I’m still thinking there is general reforming occurring @DR/Haiti border on N coast.

[AtlanticWind]

The MLC is still hanging behind the island though. With the LLC almost gone, what the chance that the new LLC could form SW of DR/Haiti?

Very unlikely , the envelope is moving clearly wnw

[Sciencerocks]

[ConvergenceZone]

should be classified as an open wave some time in the morning...Still has a ways to go to get off land completely, so only going to weaken further... Shifting my eyes to 95L now...

[skyline385]

The MLC is still hanging behind the island though. With the LLC almost gone, what the chance that the new LLC could form SW of DR/Haiti?

Very unlikely , the envelope is moving clearly wnw

Hmm it looks like its mostly moving west right now..

[AutoPenalti]

The MLC is still hanging behind the island though. With the LLC almost gone, what the chance that the new LLC could form SW of DR/Haiti?

Very unlikely , the envelope is moving clearly wnw

Hmm it looks like its mostly moving west right now..

That’s just the overall convection.

[Blown Away]

I think we are going to get a doozy of a Disco at 11pm!

[Woofde]

I think we are going to get a doozy of a Disco at 11pm!

It just came out.

"The center of Fred is estimated to be located over extreme eastern Haiti. This position is based on continuity with the previous forecast and a small low-level cyclonic circulation noted in cloud-drift wind vectors that were based on the last few GOES-16 high-resolution visible satellite images."

[eastcoastFL]

NHC 11pm Disco

Tropical Depression Fred Discussion Number 10
NWS National Hurricane Center Miami FL AL062021
1100 PM EDT Wed Aug 11 2021

The center of Fred is estimated to be located over extreme eastern
Haiti. This position is based on continuity with the previous
forecast and a small low-level cyclonic circulation noted in
cloud-drift wind vectors that were based on the last few GOES-16
high-resolution visible satellite images. A NOAA reconnaissance
aircraft performed a quasi-synoptic surveillance mission this
evening and released dropsondes while circumnavigating Hispaniola.
Some of the dropsondes measured surface winds of 24-27 kt about 150
nmi north and northwest (in the Windward Passage) of the center, and
these data support maintaining an intensity of 30 kt for this
advisory. The main convective cloud mass has been displaced to the
southeast of the low-level center due to the west-northwesterly
vertical wind shear of about 20 kt.

The initial motion estimate is 300/13 kt. The global and regional
models remain in surprisingly good agreement on Fred maintaining a
steady west-northwestward motion through 48-60 hours as a strong
ridge remains entrenched over the western Atlantic during that time
period. Thereafter, however, the NHC model guidance diverges
significantly, with the now much weaker HWRF model taking Fred more
westward, while the GFS and ECMWF models move the cyclone
northwestward over the eastern Gulf of Mexico near or just offshore
the Florida west coast; the UKMET model lies between these two track
extremes. The weaker HWRF track has been discounted given the NHC
forecast that Fred will remain vertically coherent and restrengthen
after moving back over water. Thus, the new NHC track forecast is
essentially just an update of the previous advisory track, and lies
close to the NOAA-HCCA corrected-consensus model. NOTE: the
aforementioned NOAA WP-3D reconnaissance aircraft has been releasing
dropsondes from approximately the 450-mb level and has also been
collecting tail-Doppler radar data. These data should have been
assimilated into the 0000 UTC model runs, which hopefully will
provide better track and intensity model forecasts for the next
advisory package.

Fred is forecast remain within a moderate to strong westerly to
southwesterly vertical wind shear regime throughout the forecast
period by almost all of the global and regional models. As a result,
rapid strengthening is not expected after Fred moves back over
water. There is one caveat, however, and that is the ECMWF model
forecasting the shear to weaken to 5-10 kt during the 36-72 hour
period, which could allow for a little more strengthening than what
the official forecast is currently indicating. The new NHC intensity
prediction is identical to the previous one owing to the
expectation that some degree of westerly shear will be affecting
Fred throughout the entire forecast period. The official forecast
follows a blend of the IVCN and HCCA consensus intensity models.

KEY MESSAGES:

1. Through early Thursday morning, heavy rainfall could lead to
flash, urban, and small stream flooding, along with possible rapid
river rises and potential mudslides in the Dominican Republic.

2. Tropical storm conditions are possible in northern Haiti, the
Turks and Caicos, and the southeastern Bahamas tonight, and in
portions of Cuba Thursday.

3. Beginning Friday, heavy rainfall could lead to areal, urban, and
small stream flooding, and possible rapid river rises across
southern Florida. Heavy rainfall associated with Fred will impact
the remainder of Florida and parts of the Southeast this weekend
and into next week.

4. There is a risk of tropical storm conditions beginning
early Saturday in the Florida Keys and spreading northward along
portions of the Florida west coast and the Florida Panhandle through
Monday.

FORECAST POSITIONS AND MAX WINDS

INIT 12/0300Z 19.5N 72.2W 30 KT 35 MPH...INLAND HISPANIOLA
12H 12/1200Z 20.4N 73.9W 30 KT 35 MPH...OVER WATER
24H 13/0000Z 21.6N 76.1W 30 KT 35 MPH
36H 13/1200Z 22.5N 78.1W 35 KT 40 MPH
48H 14/0000Z 23.5N 79.8W 35 KT 40 MPH
60H 14/1200Z 24.7N 81.2W 40 KT 45 MPH
72H 15/0000Z 26.2N 82.4W 45 KT 50 MPH
96H 16/0000Z 29.2N 84.2W 50 KT 60 MPH
120H 17/0000Z 31.7N 84.7W 35 KT 40 MPH...INLAND

[Blown Away]

Most of us were seeing what the NHC is reporting up near DR/Haiti border on N coast.

[ElectricStorm]

Big difference I notice in this disco is they mention the shear will likely be an issue the entire time in the gulf now. Earlier they mentioned it wouldn't much of an issue past 60 hours. Now it's the whole time.

[SFLcane]

The initial motion estimate is 300/13 kt. The global and regional
models remain in surprisingly good agreement on Fred maintaining a
steady west-northwestward motion through 48-60 hours as a strong
ridge remains entrenched over the western Atlantic during that time
period. Thereafter, however, the NHC model guidance diverges
significantly, with the now much weaker HWRF model taking Fred more
westward, while the GFS and ECMWF models move the cyclone
northwestward over the eastern Gulf of Mexico near or just offshore
the Florida west coast;

Wait what? The ECMWF moves Fred into the east coast.

[Blown Away]

Big difference I notice in this disco is they mention the shear will likely be an issue the entire time in the gulf now. Earlier they mentioned it wouldn't much of an issue past 60 hours. Now it's the whole time.

Except for the EURO being all by itself with reducing shear and landfall in SFL...

[psyclone]

The big takeaway for me is wind probs trending lower from an already low baseline. Wxman's early call of a td up the west coast might end up looking great. time will tell