September 2020:

General Weather Discussions and Analysis
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jasons2k
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This is a tough one, y'all. The LLC on base velocity looks decent, but in the last few frames it may not be as tightly defined as it was before. And at the same time you can see the MLC to its SE churning down there. The radar frames, combined with infrared, makes me think this still has a long way to go before it organizes. There was just another blowup of convection on the SW side as well. It may still be a mess but once a "center" does stack and gets established, it could strengthen very quickly going forward. I do think small changes now in the formative stages will have great implications on the eventual track, since this thing may stall and/or run parallel to the coast.
Cromagnum
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To be fair, I can't remember the last landfalling gulf storm that was more or less easy to track.
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Rip76
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19 appears a bit south of where they are currently thinking.
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tireman4
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000
FXUS64 KHGX 120134
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
834 PM CDT Fri Sep 11 2020

.SHORT TERM [Tonight Through Sunday]...
Still have a couple of storms/showers dissipating left on
radar...and plenty of bats/bugs blasting off. Band of elevated
moisture and the departing entrance region of the upper jet out
into the Gulf should spell the end of the lift and showers.
Overnight expect skies to clear and temperatures to fall into the
mid to upper 60s north and still remain balmy in the upper 70s to
around 80 on the coast. Tomorrow still looking like moisture
rotates into the area from the east in the afternoon and rain
chances to increase in the afternoon over the southeastern half of
the area.
45
&&

.AVIATION [00Z TAF Issuance]...
VFR. Light north and northeaster flow to persist. Will be
expecting some showers to develop around 18z to the east of the
terminals and spread west and southwestward with daytime heating
20-23z. For now will carry VCSH starting around 20z IAH/HOU and
then for GLS/LBX transitioning to VCTS around 21-22z.
45

&&
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tireman4
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000
FXUS64 KHGX 121146
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
646 AM CDT Sat Sep 12 2020

.AVIATION [12Z TAF Issuance]...

VFR conditions have persisted overnight and should continue to do
so through the duration of the TAF period. Latest satellite
imagery shows clear skies across a majority of the area, while a
few showers and storms are lingering offshore. As a weak system
approaches from the east today, low-level moisture will be on the
rise and precipitation chances will increase as a result. Expect
scattered showers and storms to begin to impact the coastal and
metro terminals around 20Z and last until the loss of daytime
heating around 02-03Z. Have included VCTS wording in TAFs once
again given the expected scattered nature of storms.

&&

.PREV DISCUSSION... /ISSUED 409 AM CDT Sat Sep 12 2020/

DISCUSSION...

While the early half of our weekend continues yesterday`s fair
post-frontal weather, we will soon turn our focus to any potential
impacts from a low pressure area currently over the Gulf, as well
as Tropical Depression 19, currently over South Florida.

Though there is still considerable uncertainty given these
features` organization (or lack thereof), there is probably some
more confidence that direct impacts to our area will be limited to
marine areas, and for rip currents on Gulf-facing beaches.
Indirectly, however, we should still look for these two to bulk up
our moisture levels and fuel enhanced chances for showers and
thunderstorms, particularly closer to the coast.

Of course, given that there is still considerable uncertainty, we
must urge everyone to ensure their hurricane plans and kits are in
good shape, and to continue to monitor forecasts from our office
and the National Hurricane Center. Our area is still near the
"Cone of Uncertainty", and since tropical cyclones affect wide
swaths, we cannot guarantee a safe miss yet.

SHORT TERM [Through Monday Night]...

Rainfall chances will be on the rise this weekend as the first of
two systems that we are monitoring in the Gulf approaches SE Texas.
An initial surge of low-level moisture will come as an inverted
upper trough and associated weak surface low pushes into the Western
Gulf. While the system remains disorganized and its chances of
becoming a depression remain low (20 percent over the next 48h
per the latest NHC advisory), its approach will bring more
widespread precipitation coverage to the area through the
remainder of the weekend. The increase in near-surface moisture as
this feature approaches will be quite robust. While the 12Z suite
of deterministic runs has backed off slightly on surface PW
values, they nonetheless remain in agreement in showing numbers
reaching 2.25 to 2.5 inches by Sunday afternoon. Forecast
soundings continue to show convective temps in the 88-90F range
through Sunday evening, which should be easily reachable. Given
this, have maintained the increasing PoP trend for the morning
forecast package, with likely PoPs for the bulk of the CWA by
Sunday.

While precipitation will be increasing in coverage, expected
temperatures should remain near climatological norms with highs
today and Sunday expected to reach the low 90s in most locations.
Expect a slight uptick in lows and dew points as the offshore flow
that has allowed for some cooler and drier air to reach the area
develops a more easterly component. The majority of the CWA will see
heat indicies in the vicinity of 100 degrees through the weekend and
well into next week...keeping summer with us for the time being.

LONG TERM [Tuesday Through Saturday]...

Tuesday morning should dawn with the aforementioned lead trough
down near the Mexican coast in the extreme southwest Gulf/Bay of
Campeche, while TD 19 (likely a tropical storm by then) should be
near the north central Gulf coast, and very near if not already
making landfall there. By far, the operative words in that
sentence are the `should`s. While I`m definitely more confident in
this scenario today than I was 24 hours ago, it`s always important
to guard against nasty surprises this time of year.

Regardless, since I must make a deterministic forecast, let`s roll
with this scenario. What does that mean for Southeast Texas? Well,
I`ve had to trim back rain chances a little. We should still have
ample moisture for scattered to numerous showers and storms, but
these two features may be a little more discrete than previously
thought. The lead trough looks to stay far enough offshore that
its lingering effects into Tuesday will be a little smaller than I
had yesterday, and the more organized appearance of TD 19 should
keep its moisture envelope a little more compact, and give us some
more breathing room for late in the week (If this most recent Euro
run is correct, which immediately yanks the storm to the east
after landfall, we may get a LOT of breathing room). That said,
we`re still looking at precipitable water values around to above
two inches for nigh on the entire week, so I`m not going to be
taking a meat cleaver to the rain chances here, either.

All in all, yesterday I had described the major impact to our
sensible weather as strongly juicing up the typical pattern of
showers and storms. Now, I`d still expect some enhancement to it,
but it may be more modest than 24 hours ago.

MARINE...

As the weekend progresses, the offshore winds present over the past
several days will develop a more easterly component as a weak
surface low approaches the coastal waters. The NHC continues to
monitor this system for potential tropical development, though
chances for it to become a depression within the next two days
remain low (20 percent). Nonetheless, the approach of this system
will provide a surge of low-level moisture that will drive more
widespread precipitation development through the remainder of the
weekend. Brief gusty winds and heavy downpours will be possible
within individual storms associated with this feature. A second
and potentially more potent system, now Tropical Depression
Nineteen, will emerge into the eastern Gulf of Mexico later in the
weekend. This will bring with it an additional chance of
widespread precipitation and gusty winds as is pushes westward,
although uncertainty in the forecast remains high. Mariners should
continue to monitor the latest tropical weather information. The
most recent forecast information for each of these systems can be
accessed at www.hurricanes.gov.

TROPICAL...

We continue to have several things to keep an eye on in the
tropical Atlantic basin, so here`s a roundup to keep everything
in order:

Gulf trough - This trough over the north central Gulf will pass by
our area in the short term, and still carries a low (20-30
percent) chance of development as it curves by us offshore. It is
expected to increase moisture to fuel daily showers and storms,
and is likely to increase seas and rip currents.

Tropical Depression 19 - Currently moving across South Florida,
this depression is forecast to emerge over the eastern Gulf and
gradually strengthen to at least a tropical storm as it heads
generally to the (west-)northwest. This storm should still be
monitored in the coming days, but it is more likely to take a
track to our east. We will also need to consider indirect impacts,
including continued increased swell/seas, strong rip currents on
Gulf-facing beaches, and enhanced shower/thunderstorm chances.

Tropical Storms Paulette and Rene - Neither storm over the open
Atlantic is anticipated to influence weather in Southeast Texas at
this time.

Invest 95L and a trailing African Easterly Wave - These waves,
near and west of the Cabo Verde islands, will need to be monitored
in the long term. These waves are closer to Africa than to even
the Lesser Antilles, and any predictions of their long term future
is mere speculation. There is no current indication that we have
any need to worry about either wave, but it would be foolish to
ignore them at this point, as well.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 90 73 91 72 88 / 10 10 30 10 40
Houston (IAH) 93 76 93 76 92 / 20 40 70 20 50
Galveston (GLS) 92 81 92 81 89 / 40 50 70 50 60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...NONE.
&&

$$

DISCUSSION...Luchs
SHORT TERM...Cady
LONG TERM...Luchs
AVIATION...Cady
MARINE...Cady
TROPICAL...Luchs
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jasons2k
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TD 19 is outside (south) of yesterday’s cone already.
Stormlover2020
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Looks like it’s going through the straits
BlueJay
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tireman4 wrote: Fri Sep 11, 2020 7:32 am If you are wondering why they use 90s for invests...


0-49 are TCs, STCs, or potential TCs. Basically these are the numbers we use starting with TDs in the Atlantic (TD01, TD02, TD03, etc.). In fact, the ATCF is hard coded to only go up to 49. If we were to ever get up to 49 systems in one year, we would actually start over at TD01 for number 50.

50-79 are for internal use only. NOAA will often use these before operational invests are designated to communicate among internal departments and NRL.

80-89 are for system tests. Rare, but if the NHC wants to test some new model updates/internal system changes they will use these.

90-99 are operational invests. These are further broken down by basin:

L is for Atlantic.
E is for East Pacific.
C is for Central Pacific.
W is for West Pacific.
B is for Indian Ocean (Bay of Bengal).
A is for Indian Ocean (Arabian Sea).
S is for Southwest Indian Ocean/Australia (west of 135E)
P is for Australia/South Pacific (east of 135E)
Q is for South Atlantic (generally only used by NRL).


Thanks tireman4!
Kingwood36
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I dont believe 19 will affect us here
cperk
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Kingwood36 wrote: Sat Sep 12, 2020 9:28 am I dont believe 19 will affect us here
I'm not ready to write it off just yet.
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DoctorMu
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cperk wrote: Sat Sep 12, 2020 10:17 am
Kingwood36 wrote: Sat Sep 12, 2020 9:28 am I dont believe 19 will affect us here
I'm not ready to write it off just yet.
Right. Because the models have been so accurate this year. Especially with a poorly defined storm.
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djmike
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19 wont affect us in TX. I feel comfortable saying that. Laura was different. Models would have to make a serious jump west for us to remotely see/feel anything and I dont see that happening. Some storms you just have that gut feeling of it coming our direction. Definitely not getting that from 19. *Totally my Personal opinion. Not an official forecast*
Mike
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(IH-10 & College Street)
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I see the GFS and Euro have now backed off on rainfall.. greeeaaat
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jasons2k
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Cpv17 wrote: Sat Sep 12, 2020 12:24 pm I see the GFS and Euro have now backed off on rainfall.. greeeaaat
Yep. Probably back to sprinklers again by mid-week. That didn't take long.
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Rip76
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jasons2k wrote: Sat Sep 12, 2020 2:14 pm
Cpv17 wrote: Sat Sep 12, 2020 12:24 pm I see the GFS and Euro have now backed off on rainfall.. greeeaaat
Yep. Probably back to sprinklers again by mid-week. That didn't take long.
Yep. Probably put mine out today.
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tireman4
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000
FXUS64 KHGX 121820
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
120 PM CDT Sat Sep 12 2020

.AVIATION [18Z TAF Issuance]...

VFR conditions are forecasted to persist through the day. This
evening, some evening showers and thunderstorms will develop and
move in the area as a weak disturbance moves in from the east. Not
many impacts from the system other than influx of moisture
increasing chances of showers and thunderstorm development for the
next couple of days. VCTS will be forecasted for most TAF sites
because of the scattered nature of the storms as they move into the
area or develop. 35

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL) 73 91 72 91 72 / 10 30 10 40 20
Houston (IAH) 76 93 76 93 76 / 40 70 20 50 30
Galveston (GLS) 81 92 81 91 80 / 50 70 50 60 50

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...None.

&&

$$
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tireman4
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000
FXUS64 KHGX 122008
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
308 PM CDT Sat Sep 12 2020


.SHORT TERM [Through Tomorrow Night]...

As Disturbance 1 moves along the gulf coast, rain chances increase
with low level moisture increasing in the area. Chances are low for
development over the next 48 hours but the wave does bring in wide
spread showers and thunderstorms through the weekend. PWATs for this
evening remain about 2.0 inches and by tomorrow afternoon will
increase 2.25 inches and peaking at 2.75 inches in some areas in the
CWA. Convective temperature remain in the upper 80s across the CWA
which will be easily attainable with highs in the low to mid 90s.
Precipitation for this evening is looking to be concentrated on the
eastern CWA roughly east of I-45 corridor. Tomorrow we can expect
the coverage to be more wide spread and effect the entire forecast
area. 35


.LONG TERM [Monday through Sunday]...

On Monday, an inverted upper trough will be located over Deep South
Texas and a tropical system will be approaching the Mississippi
delta. Moisture on the north side of the upper trough will be
competing with subsidence on the western periphery of TS/Hurr Sally.
At this time, feel Sally will be far enough east to allow moisture
to remain over at least the SE half of the region. PW values in
both the GFS and NAM reach 2.20 inches with convective temperatures
around 90. Subsidence begins to kick in on Tuesday and Wednesday as
Sally slowly meanders across the northern Gulf coast. 850 mb temps
remain warm and with drying noted in area soundings, MaxT values
should still be capable of warming into the lower and possibly mid
90s. By late Wednesday, an upper level trough will develop over West
Texas. Some differences between the Canadian, GFS and ECMWF with
regard to how deep through trough gets and how quickly it will move
across the US. Preferred how the ECMWF initialized and it`s relative
consistency and have leaned toward the ECMWF for the end of the week
into next weekend. Based on the ECMWF, feel the trough will move
slowly across the state and will bring a good chance of showers and
thunderstorms both Thursday and Friday. Rain chances will diminish
Friday night as the upper level trough axis pushes east and a
surface cold front pushes through the area. Upper level ridging will
redevelop over the 4 corners region and expand into Texas next
weekend. A dry northerly upper and low level flow will develop
keeping skies generally clear for next weekend. Drier conditions
expected in the wake of the sfc front with sfc dew pts possibly
falling into the upper 50`s. 43

&&

.AVIATION [18Z TAF Issuance]...

VFR conditions are forecasted to persist through the day. This
evening, some evening showers and thunderstorms will develop and
move in the area as a weak disturbance moves in from the east. Not
many impacts from the system other than influx of moisture
increasing chances of showers and thunderstorm development for the
next couple of days. VCTS will be forecasted for most TAF sites
because of the scattered nature of the storms as they move into the
area or develop. 35

&&

.MARINE...

Offshore flow will become northeasterly tonight as ridge of high
pressure builds to the north. Tropical Storm Sally will track over
the warm waters of the Eastern Gulf next few days...likely
intensifying to a strong tropical storm...then a hurricane before
making landfall somewhere on the coast between SE LA and Wrn FL
Panhandle possibly on Tuesday. WNA wave model period fields suggest
swells from Sally should could arrive on the TX coast as early as
Monday night leading to some increase in surf at that time with
swell continuing for at least 24 to 36 hours coming out from this
slow moving tropical cyclone. The more direct wind and wave impacts
from Sally should remain well to the east of the forecast area as
the storm pushes inland mid week.

Longer term a good deal of uncertainty. ECMWF brings a fairly
impressive cold front from the north with moderate north...then
northeasterly flow behind it next Friday and Saturday. Canadian
actually brings a tropical system up the coast from the Bay of
Campeche at that time. GFS maybe a tad more like the Euro but with a
much weaker front. We are leaning slightly toward the ECMWF solution
here but again note the uncertainty for Days 6 and 7....next Friday
and Saturday. 18

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL) 72 91 72 91 72 / 0 40 20 30 10
Houston (IAH) 76 95 76 93 76 / 20 60 20 30 20
Galveston (GLS) 81 91 80 91 80 / 40 50 50 30 30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...None.

&&

$$


SHORT TERM...35
LONG TERM...43
AVIATION...35
MARINE...18
unome
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Josh might not have much chasing to do with Sally - may be a question of whether they close the bridge over St Louis Bay, which would make last minute position changes more difficult - still a few days away, I'm sure the track will change some before then though

https://www.nhc.noaa.gov/#Sally
https://www.nhc.noaa.gov/refresh/graphi ... k#contents
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djmike
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What is Sallys estimated winds at landfall now per the 4pm update? Last I saw was 70. Is it forecasted to be stronger than 70 now?
Mike
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(IH-10 & College Street)
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srainhoutx
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djmike wrote: Sat Sep 12, 2020 5:10 pm What is Sallys estimated winds at landfall now per the 4pm update? Last I saw was 70. Is it forecasted to be stronger than 70 now?
85MPH at landfall now
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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