989
FXUS64 KLIX 011728
AFDLIX

Area Forecast Discussion
National Weather Service New Orleans LA
1228 PM CDT Tue Oct 1 2024

...New AVIATION...

.SHORT TERM...
(Today through Wednesday)
Issued at 228 AM CDT Tue Oct 1 2024

Synoptically, there are two jets over the North American Continent
this morning. The first is extremely evident over the northern tier
of states and southern Canada. The second, not so evident, but it
can be seen best in a secondary H3 jet max from the Pacific into
Mexico and through the southern states. This second jet(subtropical
jet) normally starts to become more evident during this time of year
getting stronger as we move into the winter months for the northern
hemisphere. These two jets are not coupled here but are in phase.
Drawing a line down the center of the polar trough at H3 and
extending this line southeast, one can easily see the core of the
polar jet at the base of the trough 100-125kt winds that drop to as
little as 5kt over SW Missouri then rise again in the base of the
subtropical upper trough to 60kt over our area. This is all from the
00z(Monday 7pm) soundings. These two jets will not couple here but
will do so down stream over the Atlantic. We need to run through
this part to show what will force the smaller scales, and vice
versa, which will eventually dictate our fcast. The upper
subtropical jet trough over our area will quickly move east today
and Wed. This troughing can easily be seen in WV imagery this
morning. As this moves east, upper ridging will begin to take
place as the upstream portion of this jet moves through. This
simply spells very nice dry conditions, typical of October, around
the area through at least Wed. This subtropical jet feature will
get mentioned again in the extended as it will play a part in some
other features.

&&

.LONG TERM...
(Wednesday night through Monday)
Issued at 228 AM CDT Tue Oct 1 2024

We will move from the westerlies to the tropics for a minute. two
very vivid features catch the eye this morning. One over the gulf
stretching from Tampa to the Yucatan. The other over the northern
Caribbean. The first is associated with an inverted trough(easterly
wave/tropical wave). The second is an upper low just leaving Jamaica
this morning. The tropical wave will continue slowly moving west
while the northern end of this will eventually move to our shoreline
late Thu into Fri, and this is when we expect the best chances of
rain. This is very typical of October. Most rainfall associated with
this month normally comes from tropical sh/ts. This is par for the
course, as even fronts that move through this time of year are
relatively dry most of the time.

Chances of something developing with this tropical wave is not very
good as the area is highly sheared and is actually doing all it can
to move the strong deep dry air to its west out of the picture.
Basically, this is bringing the deep tropical moisture into the gulf
priming the area. All real estate to the west and NW of the upper
low would also have a very difficult time getting started further
adding to the development issues. But, as with all upper lows, the
area to the south and east of this feature produces an area that is
normally quite hospitable for development of disturbances due to the
downstream diffluent nature of the upper flow. This is normally
where upper maritime highs are located or developed. As the TUTT low
moves west, we should see the current very weak disturbance over the
SW Caribbean begin to flare and this is where the hurricane center
shows their hatched area for tropical development. But they have
likely kept this at around 40-50%(7 days) due to the not so
hospitable environment it will have to eventually conquer. This
feature will eventually get to move in a general NWward motion on
the east side of the upper low. We should see this really begin
Wed. The upper low will have moved well west and start dissipating
by Thu and should be gone by the weekend. This will have set the
southern gulf in the outside southern sector of the upper low as
well. The upper maritime high that is produced downstream will be
located from the Bahamas to the FL Straits by late Wed and this is
where it will stall as it will interact with the upper
subtropical trough near the western gulf coast. The sfc low that
is expected to eventually develop over the gulf would have a much
better chance of development if this maritime high was able to
move farther west. But this sfc low will be located between these
two upper level features with some shear profiles(around 20kt),
although not enough to keep something from developing if it can
overcome this environment, but also not the most primo conditions
either. The subtropical jet that had developed a high over the
area today and Wed will now move east allowing an upper trough to
begin developing and moving into the western gulf coast by Thu
and take up real estate over TX through the weekend. The jet core
for this is still over the Pacific and won`t be sampled by the
terrestrial upper air network until Wed either 12z or Thu 00z.
This is when we should see most guidance begin to improve as far
as resolving the subtrop jet better. At the moment, satellite
soundings are doing a very good job with this as there is very
little cloud cover and deep dry air where this weak jet is
currently located. By Monday, we should see a fairly strong cold
front moving quickly southward with a good bit of dry air. This
will definitely cause a very strong precip gradient where it sets
up along the gulf coast. This is where things diverge with model
solutions as well. The subtropical upper trough is shown in all
model sets but the Euro wants to kick this mess to the east as
this trough becomes progressive allowing the front to move into
the picture with the polar jet digging. The GFS just stalls
everything over the gulf while this upper trough kicks out and
allows the front to move in. The scenario that makes the most
sense is the Euro as the polar jet becomes more dominant. But this
is way out at the end of this fcast, so your guess is as good as
mine about that occurance.

&&

.AVIATION...
(18Z TAFS)
Issued at 1227 PM CDT Tue Oct 1 2024

Scattered CU field has been expanding across the local area over the
last few hours. Although ceiling heights in some locations are below
VFR, in the MVFR category, shouldn`t be too much longer until all
decks will be VFR. Clear skies and light winds will then persist the
remainder of the forecast period.

&&

.MARINE...
Issued at 228 AM CDT Tue Oct 1 2024

A general light NE wind will slowly become easterly and rise to
around 10kt today and Wed. This will then become E to SE by Thu
finally becoming E again Fri and remaining through the weekend. By
the end of the week, east winds of 15-25kt could be produced by a
sfc low over the gulf. Showers and numerous thunderstorms could also
be possible starting Wed through the weekend. This sfc low feature
is what the hurricane center has hatched over the Caribbean and
southern gulf with a 50% chance of developing a tropical cyclone
over the next 7 days.

&&

.PRELIMINARY POINT TEMPS/POPS...
MCB  65  86  63  87 /   0   0   0  10
BTR  70  91  68  91 /   0   0   0  10
ASD  68  89  68  87 /   0   0   0  20
MSY  73  88  72  86 /   0   0   0  30
GPT  70  88  70  85 /   0   0   0  30
PQL  69  92  69  89 /   0   0   0  30

&&

.LIX WATCHES/WARNINGS/ADVISORIES...
LA...None.
GM...None.
MS...None.
GM...None.
&&

$$

SHORT TERM...TE
LONG TERM....TE
AVIATION...ME
MARINE...TE