September 2020:

General Weather Discussions and Analysis
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jasons2k
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000
WTNT64 KNHC 141602
TCUAT4

Hurricane Sally Tropical Cyclone Update
NWS National Hurricane Center Miami FL AL192020
1100 AM CDT Mon Sep 14 2020

...NOAA HURRICANE HUNTERS FIND THAT SALLY HAS RAPIDLY STRENGTHENED
TO A HURRICANE...

Data from a NOAA Hurricane Hunter aircraft investigating Sally
indicate the system has rapidly strengthened to a hurricane,
with maximum sustained winds of around 85 mph (140 km/h) with higher
gusts. The estimated minimum central pressure is 985 mb (29.09
inches).

A Special Advisory will be issued shortly to update the intensity
forecast for Sally.


SUMMARY OF 1100 AM CDT...1600 UTC...INFORMATION
-----------------------------------------------
LOCATION...28.6N 86.9W
ABOUT 135 MI...220 KM ESE OF THE MOUTH OF THE MISSISSIPPI RIVER
ABOUT 175 MI...280 KM SE OF BILOXI MISSISSIPPI
MAXIMUM SUSTAINED WINDS...85 MPH...140 KM/H
PRESENT MOVEMENT...WNW OR 285 DEGREES AT 6 MPH...9 KM/H
MINIMUM CENTRAL PRESSURE...985 MB...29.09 INCHES

$$
Forecaster Brown/Brennan
Cromagnum
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Dang. Mississippi is gonna get thumped pretty bad. Coming shore as a 90-100 mph cane and hanging around for 2-3 days.
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DoctorMu
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Cromagnum wrote: Mon Sep 14, 2020 12:46 pm Dang. Mississippi is gonna get thumped pretty bad. Coming shore as a 90-100 mph cane and hanging around for 2-3 days.
St. Bernard Parish and Biloxi are going to feel some pain. Mobile could get dumped on as Sally is a very right handed storm.
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tireman4
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000
FXUS64 KHGX 142030
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
330 PM CDT Mon Sep 14 2020

.SHORT TERM [Through Wednesday Night]...

A bit drier for the next couple of days as the disturbance to the
south moves further away to the south. To our east, Hurricane Sally
hugs the norther gulf coast and is expected to make landfall late
Tuesday. Being between the disturbance and hurricane we dont see too
much for active weather. For the rest of today, some showers and
thunderstorms are forming in the western counties, which will begin
to dissipate shortly after sunset. Most of the convection should stay
west, if not far west, of I-45. Tomorrow`s pattern will be similar
with the air mass storms forming in the western counties and moving
southwest. Wednesday evening we see higher rain chances as Hurricane
Sally is weakening after making landfall. Rain bands will become more
broad, and is expected to have some of these waves of showers move
into the area.

With no change in air mass, high and low temperatures remain
about the same. Highs average in the low to mid 90s, and lows in the
mid to upper 70s. Winds will stay northerly to northeasterly at
around 10mph in the day with lighter winds at night. Humidity does
decrease a bit, but probably not too noticeable with only about a 5%
decrease in the RH. Long term is looking a bit more promising to
start seeing some relief from the heat! 35

.LONG TERM [Thursday Through Monday]...

A robust short wave will will be oriented from NE to SW across the
state. Initially, thoughts were that the s/wv would be strong enough
to generate widespread showers and thunderstorms Thu/Fri but
lackluster jet dynamics and a wedge of drier air filtering into the
are from the NE have reduced confidence in widespread precipitation.
Looks like the best rain chances Thu/Fri will be over the SW zones
and toward the coast as a weak upper low forms over South Texas and
drier air continues to move into the area from the NE on Friday.
Fcst soundings show convective temperatures between 85-88 degrees
both days so diurnally driven shra/tsra should still be possible
both days.

High pressure over the northern Great lakes on Friday night will
ridge into the area and drier air will gently ooze into the region
from the north. A weak coastal trough will also try to develop off
the Middle and Deep South Texas coast. At this time, it looks like
the drier air will dominate on Saturday but by Sunday a well defined
coastal trough will begin to focus moisture along the coast. East
winds over the Gulf will converge with N-NE winds over land and this
boundary will serve as a focus for shra/tsra Sun Nite and Monday.
Highest rain chances will again focus near the coast and offshore.
Some model differences noted in the long term as the Canadian and
ICON hold the dry air in place while the GFS is very aggressive with
the moisture return and PW values reach 2.35 inches. Will lean
toward the conservative NBM for PoPs. 43

&&

.AVIATION [21Z TAF Update]...

MVFR ceilings to the north stuck around a lot longer than
anticipated. With that, expect ceilings tomorrow to do roughly the
same. 35

.AVIATION [18Z TAF Issuance]...

MVFR and IFR ceilings are scattering out and lifting at most of the
TAF sites. Within a couple of hours, VFR conditions will prevail.
While most of the higher 2.0+ PWATS are going to be in the western
TAF sites, chances for airmass storms are still possible for all
locations except GLS at this time. The biggest threat will be CLL
and SGR this afternoon but the orientation of the moisture axis
could shift slightly and provide the needed moisture to trigger the
convection at UTS/CXO/IAH/HOU. As the airmass storms dissipate shortly
after sunset, VFR conditions will remain for the night. Tomorrow
morning, MVFR to IFR ceilings are expected to return to the TAF
sites. Norther flying areas could see CIGs below 1000ft and
IAH/SGR/HOU/LBX at around 1500ft. Timing to dissipate tomorrow looks
to be about the same as today; close to 18z. 35

&&

.MARINE...

The main story will be increasing seas and large swells today into
Tuesday as Hurricane Sally moves into the LA and MS border. Early
this afternoon, surface observations from buoys reported winds
around 15 to 20 knots with seas from 3 to 5 feet. This trend will
continue tonight into Tuesday, with the greatest impact over the
offshore waters. A Small Craft Should Exercise Caution headline is
in effect for the entire marine zones.

Light northwest to northeast flow is expected Tuesday afternoon into
late Wednesday with seas from 1 to 3 feet. Gusty surface winds and
increasing seas return Friday into the weekend as a surface front
slides southward into our region. The passage of this frontal
boundary could bring northeast winds from 15 to 20 knots at times
and seas up to 5 feet. Caution flags or advisories may be required.

Precipitation-wise, different troughs will move through the region,
producing isolated to scattered showers and thunderstorms each
night. The best chance for thunderstorms will be Thursday and Friday
and then again on Sunday as another trough moves in. 05

&&

.TROPICAL...

The tropics remain quite active as we remain near the peak of an
abnormally active season as a whole. The main concern across the
Gulf continues to be TS Sally, which is expected to strengthen to
hurricane status before making landfall near the MS/LA border
tomorrow. Aside from increasing seas due to the system`s swells,
SE Texas is not expected to receive any direct impacts.

Elsewhere, the NHC continues to monitor Hurricane Paulette, TD
Renee, TD Twenty, and two tropical waves near the Cape Verde
Islands. At this time, current forecast guidance suggests that
none of these systems will pose a direct impact to SE Texas. The
most up-to-date forecast information can be found at
www.hurricanes.gov.

Cady

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL) 73 90 72 91 72 / 10 20 0 30 20
Houston (IAH) 77 95 76 94 76 / 10 20 0 30 20
Galveston (GLS) 81 93 81 92 80 / 20 20 20 20 30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...None.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 7 PM CDT this evening
for the following zones: Coastal waters from Freeport to
Matagorda Ship Channel TX out 20 NM...Coastal waters from
High Island to Freeport TX out 20 NM...Waters from Freeport
to Matagorda Ship Channel TX from 20 to 60 NM...Waters from
High Island to Freeport TX from 20 to 60 NM.


&&

$$

SHORT TERM...35
LONG TERM...43
AVIATION...35
MARINE...05
TROPICAL...Cady
Stormlover2020
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Need to watch the boc for development
Cpv17
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Stormlover2020 wrote: Mon Sep 14, 2020 4:45 pm Need to watch the boc for development
I agree. The Euro looks interesting.
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Rip76
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Stormlover2020 wrote: Mon Sep 14, 2020 4:45 pm Need to watch the boc for development
What timeframe?
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tireman4
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I saw that too. Always keep a wary eye to the sky...

1. A broad area of low pressure over the southwestern Gulf of Mexico is
currently producing little shower or thunderstorm activity. Any
development of this system should be slow to occur while the low
meanders over the southern Gulf of Mexico for the next several days.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...low...20 percent.
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Rip76
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Oh yes I saw the blowup down there, but I thought that was moving South.
Cpv17
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Rip76 wrote: Mon Sep 14, 2020 6:52 pm Oh yes I saw the blowup down there, but I thought that was moving South.
Yeah, but it’s expected to move back north early part of next week. I might add too that the BOC has been untouched too so you could definitely see something explode down there rather easily given the right setup and basically the whole basin has a favorable setup right now it seems. Everything is exploding. Reminds me of 2005.
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Rip76
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We could use some rain, but it’ll probably do its BOC dance to Louisiana.
Totally 2005.
TexasBreeze
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There seems to be no unorganized disturbances to bring us rain unless you count the one to the south that gave some areas a little rain Sat/Sun and south TX rain today. Everything spins up then goes north or east instead of west.
Cromagnum
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So...when is an actual cold front looking optimistic? October?
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DoctorMu
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Cromagnum wrote: Mon Sep 14, 2020 10:28 pm So...when is an actual cold front looking optimistic? October?
Saturday looks like a Chamber of Commerce day up here. Low to mid 80s, sunny; low of 62°F
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DoctorMu
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Sally has her eye on Mobile Bay now. She's weakened overnight, but since she's nearly stalled we're looking at rain measured in feet rather than inches on the AL/FL/MS coast.
gregco31
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I saw a little bit about it yesterday I think, but do we think there is anything worth paying attention to in the southern Gulf right now?
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jasons2k
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From Jeff:

Cool front to potentially move across SE TX this weekend.

Will need to monitor the southwest Gulf of Mexico late this weekend and next week

SE TX remains sandwiched between the western subsidence side of slow moving hurricane Sally over the northern Gulf of Mexico and an upper level trough of low pressure over the far western and southwestern Gulf of Mexico. This is generally producing a drier NE wind flow over the area with just an isolated scattering of heat of the day showers and thunderstorms. This pattern will hold into Wednesday, but begins to undergo change by Thursday and into the weekend.

As Sally moves slowly inland and then NE further away from SE TX, its subsidence on the west edge will end over SE TX by late Wednesday. A trough of low pressure will approach from the NW on Thursday and this feature coupled with increasing Gulf moisture will likely result in a fairly active day of showers and thunderstorms. This trough looks to linger over the area into Friday and potentially Saturday before a “cool” front moves into the area on Saturday. Latest guidance continues the theme of moving this front through the area and out into the Gulf of Mexico over the weekend and there may be some slightly better chances of this happening than with the last front as the northerly flow on the west side of Sally may help this pattern. Will go with a drier air mass moving into the region on Saturday and lingering into Sunday.

Western Gulf:
NHC has been monitoring a trough of low pressure that has been drifting SW and S over the Gulf of Mexico for several days. This feature is expected to remain over the southern Gulf and Bay of Campeche into early next week while a frontal boundary drifts into the northern Gulf. Global forecast models have shown a bit more potential for development with this feature in some of their more recent runs and indicate that a more defined area of low pressure may develop late this weekend or early next week over the southwest Gulf of Mexico. Position of forecast large scale high pressure behind the cool front should keep any feature that tries to develop slow moving over the southwest or southern Gulf and eventually a slow west motion. This is something to monitor in the coming days, but at this time any threat to TX looks unlikely.

Jeff Lindner
Director Hydrologic Operations Division/Meteorologist
Harris County Flood Control District
Scott747
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There has definitely been a building consensus on development in the sw gulf. 12z Ukie has a borderline cane around Tampico and the 12z Euro has a strong ts near Brownsville.

With the increase in modeling it should get an invest tag soon and the hurricane models will start running. Given their performance this season, the sooner the better.

For now I don't see anything to kick it this way but still plenty of time for changes.
TexasBreeze
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The Euro has been consistently showing 15+ inches of rain with even some 30" areas offshore TX and deep south TX. The GFS not so much. CMC is further south.
Stormlover2020
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Keep shifting north, steering currents weak, wouldn’t surprise to crawl up this way, but we are more than 7 days out so have time to watch
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