ATL: SALLY - Post-Tropical - Discussion

[Chemmers]

Looks like the very cold clouds tops are trying to wrap round the centre again

[bella_may]

Looks like the very cold clouds tops are trying to wrap round the centre again

Appears to be trying to build something on the southern side too. We’ll see if it holds

[NXStumpy_Robothing]

Note: For anyone trying to use the Mobile (KMOB) radar, it has not reported data in the last hour. It should be fixed relatively soon, but until then, opt for the further away Eglin AFB (KEVX) or New Orleans (KLIX) radars.

Speaking of radar, there's been a pretty decent improvement in structure of the core as others have mentioned. Will be interesting to see if Sally can manage to fully wrap around its primitive eyewall and close off that eye that has been open for the past 24 hours.

[GCANE]

Feeder band is more intense than last night.
Saw it was being fed by 3000 CAPE. Now its 3500.
Eye seems to be drying out as well and trying to close.
Last night it was at 95% RH. Last drop was at 63%.
Rain rate 50 mm/hr. Enough to keep her going for a while.

[tropicwatch]

Very circular convection expansion occurring.

[GCANE]

Still bursting.

30 knots of shear.

A classical, symmetrical warm-core has developed with the cold-pool warming as well.

She is transitioning from the shear-driven cold-pool-driven TC to the traditional warm-core TC.

With the increase in shear however, will likely limit intensification, could even start to knock her down a bit.

It'll take time and need to see how this plays out.

[bella_may]

Getting some big wind gusts here now. Over 40 mph if I had to guess

[GCANE]

Can't beat that outflow.
Sitting right in the middle of the PV ring.

[tropicwatch]

The outflow could be diminishing the shear over Sally somewhat.

[Stormgodess]

Pressure drop to 983? With her looking so raggedy?

[GCANE]

Big jump in the feeder band.
CAPE at 4500, close in.

[GCANE]

Wind profile around the core looking much more symmetrical like a classical cane.
Solid evidence this has transitioned to the classic warm-core TC.
Circulating towers also show this. Seems like a solid eyewall could develop over the next few hours.

[GCANE]

Eye drop at 983mb.
Couldn't get a humidity reading.

[Dean4Storms]

She’s drifting north right now.

[GCANE]

VDM
Eye: Circular, 34 nm wide, open SW
28.93N 88.03W
983 mb

[Dean4Storms]

FDMOB

Area Forecast Discussion
National Weather Service Mobile AL
447 AM CDT Tue Sep 15 2020

.NEAR TERM UPDATE /Now Through Wednesday/...Hurricane Sally was
located about 90 miles south of the east end of Dauphin Island and
is crawling west northwest at ~ 2 mph. Bursts of deep
convection/cold cloud tops to between -80C/-85C continue at the core
of the hurricane, but comes in cycles and has not persisted for any
substantial length of time. The lack of persistence is due to
upwelling of cooler oceanic water to the surface due to Sally`s slow
forward speed and entrainment of drier air at mid-levels. Northeast
of Sally`s center, radar data indicates a strong convective band
with embedded supercells rotating westward over the coastal waters.
With these supercells, doppler radar storm relative velocities have
shown rotating couplets which is an indication of an increased
tornado threat as the band pivots up near the coast this morning.
This is supported by 0-1 KM storm relative helicity values aligned
along the outer band which range from 250 to 500 M2/S2; these values
are intersecting the coast. Sally`s center though was ragged
since Monday evening but seems to have achieved a better
representation early this morning. Even so, latest discussions
from the National Hurricane Center indicate that Sally is coming
into an area of moderate to high mid to upper level shear.
Considering this the forecast intensity has been lowered. Little
change has occurred in the track approach to the coast, but what
has changed is at a slower forward speed per the 15.09Z advisory.
The official forecast now has Sally crossing coastal Mobile county
late Wednesday morning at category one strength but gusts could
still achieve category two strength. Considering this, Hurricane
force winds remain likely Tuesday night and Wednesday for Mobile
and Baldwin counties. But Sally`s wind field is forecast to
weaken/shrink rapidly soon after landfall.

Conditions are expected to deteriorate today as more organized
outer rainbands lash the Gulf coast with tropical storm force
winds and very heavy rainfall. These bands will spread further
northwest and northward through the course of the day bringing
tropical storm force wind gusts to portions of the interior. Sally
begins re-curvature into the day Wednesday with the core moving
up across the Mobile/Tensaw River Valleys late in the day,
progressing northeast into the interior of southwest AL by
evening. In addition to evolving life threatening storm surge,
dangerously high breaking waves/high surf will likely result in
coastal erosion. Other impacts will be deadly rip currents and
dangerous torrential rainfall which will likely result in life
threatening flash flooding. The tornado threat will also be on the
increase.

It is extremely important to stay vigilant and have an action plan
in place as short term adjustments to track and intensity can still
occur. Therefore, please make sure to continue to check our web-page
(weather.gov/mob) as well as the National Hurricane Center
(www.hurricanes.gov) for the latest updates and information on
Hurricane Sally. /10

&&

[Nimbus]

She is actually doing a loop if you look at recon reports.

Sally seems to be a morning girl with another bloom of convection and lower pressures for the 5 AM update.
Recon is reporting a loop in her track centered near 88 W which is a slight jog west from yesterday.

From the NHC advisory steering will be provided by "a weak mid level trough" approaching by Wednesday.
Looks like the upper level ridge still goes all the way to western Texas this morning on the west side and we still have the Atlantic TUTT on the east side.

Sally is just east of center in the 200 mb flow so the weakening last night that allowed the westward jog may be followed by some slight southern jog as she strengthens this morning. Once the dome builds further east the steering at 200 mb is more and more north until the mid level trough arrives.

So we wobble watch.

She needs to start going due north pretty quickly if she’s gonna make landfall east of Mobile. Just my opinion

Stall forecasts are difficult, sometimes the turn is delayed and the storms head off 180 degrees from their previous motion.

[smw1981]

In (west) Mobile, we just started with the “good” rain and some pretty decent gusts of wind, but nothing too crazy. I will try to post video once the sun is up..

[wxman57]

She is actually doing a loop if you look at recon reports.

Sally seems to be a morning girl with another bloom of convection and lower pressures for the 5 AM update.
Recon is reporting a loop in her track centered near 88 W which is a slight jog west from yesterday.

From the NHC advisory steering will be provided by "a weak mid level trough" approaching by Wednesday.
Looks like the upper level ridge still goes all the way to western Texas this morning on the west side and we still have the Atlantic TUTT on the east side.

Sally is just east of center in the 200 mb flow so the weakening last night that allowed the westward jog may be followed by some slight southern jog as she strengthens this morning. Once the dome builds further east the steering at 200 mb is more and more north until the mid level trough arrives.

So we wobble watch.

She needs to start going due north pretty quickly if she’s gonna make landfall east of Mobile. Just my opinion

No, it should turn NNE-NE prior to landfall. It is on track.

[wxman57]

Looking at a 3-hr radar loop with lat/lon lines plotted, it does appear as if Sally has wobbled a little northward. This does not imply it is moving or has turned north.