September 2020:

General Weather Discussions and Analysis
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DoctorMu
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Re: September 2020

Post by DoctorMu » Tue Sep 15, 2020 1:51 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.

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tireman4
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Re: September 2020

Post by tireman4 » Tue Sep 15, 2020 2:33 pm

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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Re: September 2020

Post by Cpv17 » Tue Sep 15, 2020 4:47 pm

DoctorMu wrote:
Tue Sep 15, 2020 1:51 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

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Re: September 2020

Post by Scott747 » Tue Sep 15, 2020 5:01 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.

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Re: September 2020

Post by Cpv17 » Tue Sep 15, 2020 6:11 pm

Scott747 wrote:
Tue Sep 15, 2020 5:01 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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Re: September 2020

Post by sambucol » Tue Sep 15, 2020 6:46 pm

Is there anything keeping the system tracking to the Galveston area if it forms?

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Re: September 2020

Post by Ptarmigan » Tue Sep 15, 2020 6:53 pm

Scott747 wrote:
Tue Sep 15, 2020 5:01 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.

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Re: September 2020

Post by Scott747 » Tue Sep 15, 2020 7:39 pm

Cpv17 wrote:
Tue Sep 15, 2020 6:11 pm
Scott747 wrote:
Tue Sep 15, 2020 5:01 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.

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Re: September 2020

Post by Scott747 » Wed Sep 16, 2020 12:08 am

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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Re: September 2020

Post by DoctorMu » Wed Sep 16, 2020 1:46 am

Cpv17 wrote:
Tue Sep 15, 2020 4:47 pm
DoctorMu wrote:
Tue Sep 15, 2020 1:51 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. ;)

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