September 2020:

General Weather Discussions and Analysis
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DoctorMu
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The fly in the ointment per Jeff Linder about fronts reaching the GoM. Could accentuate tropical development next week.

Euro and Canadian have a discrete low near Corpus next week. GFS is sticking to lemonade. GEFS-Para Ensemble has a low lurking off the coast.

So, eyes back to the Gulf.
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tireman4
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000
FXUS64 KHGX 152010
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
310 PM CDT Tue Sep 15 2020

.SHORT TERM [Through Wednesday Night]...
Scattered showers and isolated thunderstorms should taper off
with the loss of heating this evening. Look for a quiet overnight
period followed by a somewhat similar setup on Wed with isolated
precip development in the afternoon. PW`s will be a touch lower
and subsidence a bit higher so would anticipate less overall
coverage. 47

&&

.LONG TERM [Thursday Through Tuesday]...
Thursday is looking to be the wettest day of the long term period as
SE Texas gets into a favorable spot for precipitation with a mid-
level trough moving across Texas and being located in the vicinity
of the right entry region of upper-level jetstreak. These factors
combined with PWATs around 2 inches and daytime heating will lead to
scattered showers and thunderstorms across most of the area by the
afternoon lingering into Thursday evening. Showers and thunderstorms
will remain a possibility on Friday as PWATs remain near 2 inches,
but coverage will be more isolated without the upper-level support.

Beginning late Friday into Saturday morning, Houston will get its
second opportunity of the fall season for a weak cold front/dry line
to reach the area. This time, the drier air may be able to penetrate
the region all the way to the coast allowing for some more fall-like
conditions over the weekend. Like the boundary from the other week,
this one will be very shallow, so will not have too high confidence
in the evolution of this front until some of the high resolution
guidance gets into play.

How far south this boundary makes it will really determine the
weather next week. Not much precipitation is expected in this period
as drier air (PWATs down to near 1 inch) settles in behind the
front. However, there this is not set in stone and could drastically
change if that boundary does not push as far south as expected. A
low pressure system may develop in the southern Gulf off the coast
of southern Texas over the weekend. This system will bring heavy
rain and gusty winds over the Gulf waters. If this boundary doesn`t
make it as far south as currently depicted, or if it retreats north
faster, then those heavy rains may creep further north as well. So
something to keep an eye on in the coming days.

Temperatures will remain fairly consistent through the period with
highs in the upper 80s to low 90s and minimum temperatures in the
mid 60s up north to low 70s south of I-10. The real change in the
long term will be with the heat index. Heat indices will drop from
near triple digits on Thursday/Friday to near 90 (so very close to
the actual temperature) over the weekend thanks to the drier air.

Fowler

&&

.MARINE...
At high tide, observed water levels along the coast/bays are
generally 3.0-3.4ft MLLW. Lack of significant surf & wind has kept
coastal flood/rip concerns on the low side...and we`ll be going
into low tide this evening. Likewise, the 3-6ft swell from Sally
has peaked and seas will be on a gradual downward trend tonight-
Thurs with light (to occasional moderate) n/ne flow prevailing.

Meanwhile, the disturbance/elongated low situated across the
western Gulf will meander about the area as we head into the
weekend. The tail end of a frontal boundary should approach the
coast on Friday and linger near and just off the coast thru the
weekend as well. The combination/proximity of both will leave a
tight pressure gradient producing a long fetch of moderate to
strong ne/ene winds into early next week. This setup, assuming
things pan out as models currently depict, would be one that would
also produce large seas and potential for coastal flooding. Just
something to keep an eye on as we head into later parts of the
week... 47

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 72 90 72 88 69 / 10 20 20 50 20
Houston (IAH) 75 95 76 91 73 / 0 20 10 40 20
Galveston (GLS) 81 93 81 90 78 / 10 10 20 40 30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...None.
GM...None.

&&

$$
Cpv17
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DoctorMu wrote: Tue Sep 15, 2020 2:51 pm The fly in the ointment per Jeff Linder about fronts reaching the GoM. Could accentuate tropical development next week.

Euro and Canadian have a discrete low near Corpus next week. GFS is sticking to lemonade. GEFS-Para Ensemble has a low lurking off the coast.

So, eyes back to the Gulf.
How has the GFS handled genesis this year? Hell it didn’t even notice Hanna till was basically a hurricane lol
Scott747
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18z GFS has a much stronger vorticity that goes in around La Pesca. Matter of time before an invest is declared and odds are raised on the TWO.
Cpv17
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Scott747 wrote: Tue Sep 15, 2020 6:01 pm 18z GFS has a much stronger vorticity that goes in around La Pesca. Matter of time before an invest is declared and odds are raised on the TWO.
Don’t you think it’ll be at least a couple more days before we get an invest from this? I was thinking Thursday or Friday.
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sambucol
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Is there anything keeping the system tracking to the Galveston area if it forms?
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Ptarmigan
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Scott747 wrote: Tue Sep 15, 2020 6:01 pm 18z GFS has a much stronger vorticity that goes in around La Pesca. Matter of time before an invest is declared and odds are raised on the TWO.
It certainly bears watching.
Scott747
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Cpv17 wrote: Tue Sep 15, 2020 7:11 pm
Scott747 wrote: Tue Sep 15, 2020 6:01 pm 18z GFS has a much stronger vorticity that goes in around La Pesca. Matter of time before an invest is declared and odds are raised on the TWO.
Don’t you think it’ll be at least a couple more days before we get an invest from this? I was thinking Thursday or Friday.
Another couple of cycles with a building consensus of development and I'd guess they will pull the trigger tomorrow along with increasing the TWO odds.
Scott747
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As suspected they have increased the odds on the outlook to 20/40 with a slow drift in the BoC and sw gulf for the next few days.

0z guidance has been similar to the earlier runs with the Ukie, Icon and Canadian remaining to the s near Tampico or just s of the border.

0z GFS initially tried to spin up something down there similar to the others before switching to a weak reflection near the middle Texas coast.
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DoctorMu
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Cpv17 wrote: Tue Sep 15, 2020 5:47 pm
DoctorMu wrote: Tue Sep 15, 2020 2:51 pm The fly in the ointment per Jeff Linder about fronts reaching the GoM. Could accentuate tropical development next week.

Euro and Canadian have a discrete low near Corpus next week. GFS is sticking to lemonade. GEFS-Para Ensemble has a low lurking off the coast.

So, eyes back to the Gulf.
How has the GFS handled genesis this year? Hell it didn’t even notice Hanna till was basically a hurricane lol
I have "no comment" on 2020 models. ;)
Cpv17
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Up to 40/60 now.
cperk
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90L according to the NHC 5 day outlook will be still sitting in the sw GOM.
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sambucol
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Is there anything stopping it from heading to the Houston/Galveston area?
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tireman4
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000
FXUS64 KHGX 161128
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
628 AM CDT Wed Sep 16 2020

.AVIATION...

Expecting to see some SHRA/TSRA development mainly in the afternoon
to the w thru SW of the CXO-IAH area. N winds will be roughly in a 5
to 10 knot range. Any storms that do develop will dissipate after sunset,
and VFR can be expected for most TAF sites tonight. Some SHRA/TSRA development
is possible before sunrise tomorrow, but look for better chances as
the day progresses as a disturbance moves into the area. 42

&&

.PREV DISCUSSION... /ISSUED 440 AM CDT Wed Sep 16 2020/

SHORT TERM [Today through Thursday]...

Another very warm and mostly dry day can be expected today across Southeast
Texas. Isolated mainly afternoon through early evening showers and possible
thunderstorms are anticipated to develop during the peak heating hours.
High temperatures will reach the low to mid 90s across a majority of
the area. A disturbance moving across the state on Thursday will bring
better rain chances to the area, possibly beginning before sunrise then
increasing as the day progresses with a peak probably during the afternoon
through early evening hours. If this materializes, the clouds and rain
should keep afternoon high temperatures several degrees lower than
what has been recorded over the past couple of days. 42

LONG TERM [Thursday Night through Tuesday]...

Showers and thunderstorms associated with the approach of the
shortwave trough on Thursday will diminish in the evening hours with
the loss of daytime heating, though abundant low-level moisture and
favorable jet dynamics may support additional development over the
coastal waters. This will continue on Friday as the upper trough
axis and associated jet streak sags southeastward, placing the
offshore waters within the streak`s right front quadrant. Have
continued to carry chance PoPs for most areas south of I-10 as
daytime highs should reach convective temps in the upper 80s, but
most favorable chances remain offshore given the upper-level support.

Heading into the weekend, our attention turns to the approach of a
surface cold front which could not only bring the first taste of
autumn to SE TX but but also influence the eventual trajectory of a
potential tropical system being monitored in the southwestern Gulf.
00Z GFS & ECMWF both continue to bring a shallow frontal boundary to
the northern zones on Friday, though both solutions have sped up
slightly in the past 24hrs with its arrival now occurring on Friday
afternoon. The boundary should push through the area and eventually
stall offshore on Saturday morning, allowing for a hefty surge of
drier air in its wake that will drive 2-m dew points downward by
around 10-15 F across the board by Sunday. While daytime highs are
unlikely to waver much as 850mb temps look to hold around 17-18 C,
the drop off in humidity will result in max heat indicies around 85-
90 through the end of the weekend which should keep things
(relatively) pleasant outside. With inland PWs dropping off sharply
behind the boundary, should see precipitation confined to the
coastal waters with the slight chance of activity expanding to the
coast. Of course, confidence in this forecast will increase as the
NAM/other higher resolution models begin to depict this feature but
for the time being it`s shaping up to be a generally clear and dry
weekend across SE TX.

The NHC continues to monitor a disturbance in the southwestern Gulf
near the Bay of Campeche that has a 40% probability to develop into
a tropical depression over the next 5 days. While high pressure
behind the aforementioned cold front should generally work to
slow/stall the system as it pushes northward during the beginning of
the week, its approach could potentially bring significant rainfall
to the coastal waters. Much of this feature`s development remains
uncertain and will be tied to the strength of the surface boundary
and its eventual evolution as it reaches the coast, and global
models have shown large spread in its eventual track and
development. Nonetheless, we will continue to monitor this
disturbance closely over the next several days.

Cady

MARINE...

The downward trend in seas will continue through Thursday with light
to occasional moderate north and northeast winds. Heading into the
weekend, look for a cold front to move off the coast. This front in
combination with a lingering disturbance in the western Gulf will lead
to increasing northeast winds, building seas and rising water levels
into early next week. Periods of showers and thunderstorms can be expected
too, especially at the end of the weekend and into the start of next
week. Mariners should monitor the western Gulf system for possible
tropical depression formation later this week or over the weekend.

CLIMATE...

It has been a very warm fist half of September (1-15) for a large portion
of Southeast Texas. The City of Houston`s average temperature of 85.5
degrees is 3.8 degrees above normal. Only one day this month (the 8th)
has the average temperature been below normal. Houston Hobby`s average
temperature of 86.7 degrees is 4.8 degrees above normal. Every day this
month has seen average temperatures above normal. The City of Galveston`s
average temperature of 87.4 degrees is 4.3 degrees above normal. Only
one day this month (the 8th) has the average temperature been below
normal.

42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 90 72 86 68 86 / 20 20 50 40 20
Houston (IAH) 95 76 91 73 90 / 20 20 40 40 20
Galveston (GLS) 93 81 90 78 88 / 10 20 40 40 30

&&

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

$$
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Rip76
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sambucol wrote: Wed Sep 16, 2020 8:51 am Is there anything stopping it from heading to the Houston/Galveston area?
I believe there is a front coming down later this week. (I believe)
Scott747
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It's sad when you look at the ICON before the GFS....

12z ICON and Canadian are further n.
Scott747
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12z Ukie is also a bit further n. 100 mi or so offshore of La Pesca moving wnw at the end of the run.
Cpv17
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Probably wouldn’t get anything here if it goes into NMX. Corpus Christi yeah, south of there probably little to nothing.
Stormlover2020
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Models been so bad this year
Scott747
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Hurricane models are running this cycle.

12z HWRF is well off the coast of Brownsville as a strong tropical storm thru 66 hrs.
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