780
FXUS64 KMOB 221051
AFDMOB

Area Forecast Discussion
National Weather Service Mobile AL
551 AM CDT Sun Sep 22 2024

...New AVIATION...

.AVIATION...
(12Z TAFS)
Issued at 551 AM CDT Sun Sep 22 2024

VFR conditions are expected through the period with the exceptions
of some early morning and late night patchy fog. Light and
variable winds become easterly around 5 knots over interior areas
today, with a southerly flow at 5 to 10 knots developing near the
coast in the afternoon. Light and variable winds are expected for
tonight. /29

&&

.PREV DISCUSSION... /issued 454 AM CDT Sun Sep 22 2024/

..New NEAR TERM, SHORT TERM, LONG TERM, MARINE...

NEAR TERM...
(Now through Monday)
Issued at 454 AM CDT Sun Sep 22 2024

An upper ridge over the region is slowly deflected mostly into the
Gulf through the period in response to a large upper trof which
evolves over the central CONUS. A surface ridge generally persists
over the southeast states with a light and mostly easterly flow
expected today except for a sea breeze circulation developing near
the coast. The surface flow looks to become southeasterly or
southerly over the entire area on Monday. Subsidence associated with
the upper ridge should preclude convective development, though can`t
rule out a stray shower or storm on Monday as the upper ridge begins
to be pushed out of the area. Highs today and Monday will be 90 to
95. Lows tonight and Monday night tend to range from around 70
inland to the lower 70s near the coast. A low risk of rip currents
is expected through Monday night. /29

SHORT and LONG TERM...
(Tuesday through Saturday)
Issued at 454 AM CDT Sun Sep 22 2024

We continue to monitor an area of low pressure that is slated to
develop over the southern Gulf by midweek. This eventual feature,
which is expected to form off of a developing Central American
Gyre (CAG), now has a 70 percent chance of developing into a
tropical cyclone over the next 7 days. Unfortunately, there still
remains a lot of uncertainty when it comes to the strength,
timing, and trajectory of this system. I will once again break
down the remainder of the discussion into a "what we know" section
and a "what we don`t know at this time" section.

What we know... Satellite imagery and model analysis suggests that
the CAG is continuing to mature over Central America this morning.
Although activity is still rather scattered and sprawled out,
pockets of deep convection are now developing around this feature,
with a decent blowup of clouds and storms forming just off the coast
of Nicaragua and Honduras.  Whether or not this new convection will
eventually become the trackable feature is yet to be seen, however,
latest guidance is beginning to pick up on a more concentrated area
of low pressure developing near this activity by around the
Monday night timeframe. This feature will likely be steered north-
northwestward around the larger-scale CAG feature, crossing over
the Yucatan Peninsula or through the Yucatan Pass and arriving in
the southern Gulf on Wednesday. At this point, the system will
start to break off from the CAG and will start feeling the
steering effects of the upper-level features to its north. The
known upper features at this point include: an upper ridge located
over the southeast US and a longwave trough digging into the
central US. Yesterday, an additional cutoff upper low over the
south central US was mentioned, however, model trends over the
past day are beginning to drop this feature in favor of a more
vigorous upper trough. More about this trend in the next section,
as this change will likely play a big role in the storm`s
eventual path. As the system enters the Gulf, strengthening is
likely due to the very warm Gulf waters and being located
underneath an upper-level anticyclone (giving way to low shear
values). Additionally, models are suggesting that this system will
be quite large, so even though the eventual track of this system
is rather murky, marine and coastal/surf impacts will likely be
felt across a majority of the Gulf Coast region, regardless of
track. We will begin honing into the details of these impacts as
we get closer in time.

What we don`t know at this time... The feature still has not
developed yet. Although we are starting to see the signs that a
trackable feature may soon be forming, as of right now models are
still unsure of what to latch onto. As mentioned yesterday, when
this lack of data gets inputted into the various models and then
we look out at the solutions 5-7 days out, this leads to a
plethora of inaccuracies within each model run that ultimately
affects the model run`s overall output. This is why there
continues to be so much run-to-run and model-vs-model variability
in the overall strength, trajectory, and timing of this storm.
Once the feature finally develops in the next day or so, this
issue should start to resolve itself and we should start to see
guidance begin to converge on a most probable solution. The other
big uncertainty is with regards to the upper-level steering
features at play. There were a few notable changes in the recent
model suite that are different then what the models were showing
1-2 days ago. Previously, much of the guidance suggested that as
the upper longwave trough digs into the central US, a weak cutoff
low would break off from the main trough and travel into the
Texas/Oklahoma/New Mexico region. This led to the tropical system
feeling its influence and caused it to take a path more in the
western/central Gulf. Today, instead of a lobe breaking off from
the main trough, most guidance now suggests that the actual
longwave trough will strengthen and dig far enough south to break
off from the northern jet stream. This now results in an
anomalously massive upper low parking itself over the Mississippi
River Valley. The strength and eastward extent of this upper low
helps to break the ridge down a bit quicker, ultimately resulting
in an eastward shift in a good majority of model guidance over the
past day for the tropical system. With that being said, these
sudden changes in model guidance tells me that the upper features
at play are extremely complex and fickle and, at this time, any
one model run should not be taken at face value, especially since
we still do not have a trackable feature. Expect models tracks to
continue to shift back and forth a bit longer until guidance has a
better handle of the system and the upper features at play, and
by that time, we can begin focusing on our local impacts. As
stated earlier, even if the center does not directly impact our
CWA, impacts will likely be felt far removed from the center of
the system due to its expected size. We will continue to monitor
trends closely and we urge residents and visitors across the
entire Gulf Coast to continue to monitor the forecast over the
coming days. /96

MARINE...
Issued at 454 AM CDT Sun Sep 22 2024

No impacts are expected through Wednesday, then winds become
moderate to strong Wednesday night with similar conditions expected
for Thursday. Seas build significantly Thursday in response to a
potential tropical system in the Gulf. Please see the National
Hurricane Center for more information on this possible system. Winds
and seas will be higher near storms beginning mainly by Tuesday
night. /29

&&

.PRELIMINARY POINT TEMPS/POPS...
Mobile      93  71  93  70  91  72  87  72 /   0   0   0   0  10  10  50  40
Pensacola   91  74  90  74  88  75  86  74 /   0   0   0   0  10  10  50  50
Destin      89  75  90  75  88  76  86  75 /   0   0   0   0  10  10  50  50
Evergreen   94  69  95  69  92  68  90  69 /   0   0   0   0  10  10  50  40
Waynesboro  93  70  93  69  92  69  88  68 /   0   0   0   0  10  10  50  30
Camden      92  70  93  70  92  68  89  69 /   0   0   0   0   0  10  50  40
Crestview   94  69  94  69  92  69  89  70 /   0   0   0   0  10  10  50  40

&&

.MOB WATCHES/WARNINGS/ADVISORIES...
AL...None.
FL...None.
MS...None.
GM...None.
&&

$$

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