August 2020:

General Weather Discussions and Analysis
weatherguy425
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srainhoutx wrote: Tue Aug 25, 2020 6:05 am Too close for comfort with the 06Z HMON.
And another shift west.
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srainhoutx
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First center pass of NOAA RECON suggests Laura continues to strengthen. Estimated Extrapolated 992mb.
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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srainhoutx
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06Z HWRF suggests TX/LA border which is a little W of 00Z solution. I have noticed the Hurricane models are showing a bit more organization on the Western peripherals of the cyclone. Perhaps the inverted trough over Central Texas may be trending weaker? Time will tell.
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srainhoutx
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Mandatory evacuation order issued for Galveston Island effective now per Jeff
Carla/Alicia/Jerry(In The Eye)/Michelle/Charley/Ivan/Dennis/Katrina/Rita/Wilma/Humberto/Ike/Harvey

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tireman4
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Meanwhile, back home...


000
FXUS64 KHGX 251020
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
520 AM CDT Tue Aug 25 2020

.SHORT TERM[Today through Thursday Night]...

Cut to the chase. The NHC track has shifted about 30-50 miles west
of the previous track. This has necessitated expanding the Hurricane
Watch westward to include Galveston Island/Coastal mainland
Galveston/Coastal Harris/All Chambers/Southern Liberty in the
Hurricane Watch.

The 00z model runs appear to be picking up on the slightly further
west and southwest initial condition (previous runs appeared to be
getting the initial 12 hours incorrect with the center too far to
the northeast) so the track is getting shifted west. This will lead
to conditions deteriorating Wednesday as it starts it northward turn
and clips the area with strong winds as a major hurricane is
wrapping up over the Gulf south of Sabine pass and bringing tropical
storm force winds and hurricane force winds to the eastern areas.
Tide levels will be increasing quickly Wednesday as the long period
swells arrive leading to 4-6 feet for portions of Bolivar
peninsula/High Island...7+ feet east of High Island. If the track
shifts further west in subsequent forecasts those numbers will
increase substantially in and around Galveston Bay. This is solidly
a stay tuned forecast - small track changes at this point can make a
huge difference! A category 3 hurricane means business so don`t get
complacent.

Given the track the threat for heavy rainfall will ramp up Wednesday
afternoon through Thursday morning. 1-4" with isolated amounts 6
then in the eastern most areas of Liberty/Chambers county greater
amounts likely 4-8" isolated 12". Again the track is going to
dictate the amounts.

The threat for tornadoes looks fairly low at this time but this too
is highly dependent on the track and where that more
tornado favorable right front quadrant strikes.

As the system moves inland some drier air from Central Texas may get
absorbed and could start to shut down the heavier rain threat
Thursday by noon. Laura should continue to move north into Arkansas
late Thursday afternoon/early evening. As it moves into AR Thursday
night do anticipate that a band of deep tropical moisture will be
pulled into SETX and another round of storms will be possible.

As for the very short term expect that today will be hot with heat
indices of 102-106 and light winds with abundant sunshine until we
reach the convective temperature around 94 with rain chances mainly
east of Huntsville to Angleton line. With the dewpoints on the
increase expect that Wednesday is going to feel hotter and may flirt
with 105-109 heat indices in the central and western areas. Rain
chances toward sunrise Wednesday increasing over area especially in
the Galveston Bay area southward into the Gulf. 45/11

&&

.LONG TERM [Friday through Tuesday]...

Even in the post tropical weather landscape, long-range models are
continuing with a rather wet forecast for SE TX. A broad upper lvl
shear axis (in the wake of Laura) is progged to linger across E/SE
TX by Fri on through the weekend. This along with daytime heating,
leftover moisture and boundaries should support scattered showers/
thunderstorms during the afternoons...despite the upper ridge from
the west trying to build in this direction.

However, by the start of next week, shortwaves moving in from the
SW along with more upper level disturbances moving in from the NW
and W will help to carve out a more distinct longwave trof across
the Central Plains. This will then allow for a cold front to move
down into the Southern Plains (and perhaps into the state) by the
middle of next week. FROPA down to the Upper TX coast will be un-
likely (as its upper support seems to trek off to the NE quickly)
but could act as a focus for slightly better POPs across northern
portions of the CWA for this time frame. 41

&&

.AVIATION [12Z TAF Issuance]...

Still VFR this morning and should remain so until this afternoon
with a small threat for SHRA/TSRA over the terminals from mainly UTS
southward. Expect a lull in storms after 00z then becoming more
scattered again after 09z Wednesday. Tropical storm/Hurricane
Watches are in effect and strong winds with showers and
thunderstorms will impact area terminals from UTS to IAH/HOU/GLS
mainly Wednesday starting near GLS around 18z and expanding inland
through 12z Thursday.
45

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 97 76 95 76 96 / 20 20 50 40 30
Houston (IAH) 97 78 93 78 94 / 30 30 70 80 50
Galveston (GLS) 92 82 88 81 89 / 30 70 70 90 60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Storm Surge Watch for the following zones: Brazoria Islands...
Chambers...Coastal Galveston...Coastal Harris...Galveston
Island and Bolivar Peninsula.

Tropical Storm Watch for the following zones: Brazoria Islands...
Coastal Brazoria...Inland Brazoria...Inland Galveston...
Inland Harris...Montgomery...Northern Liberty...Polk...San
Jacinto...Trinity...Walker.

Hurricane Watch for the following zones: Chambers...Coastal
Galveston...Coastal Harris...Galveston Island and Bolivar
Peninsula...Southern Liberty.

GM...Hurricane Watch for the following zones: Coastal waters from
High Island to Freeport TX out 20 NM...Galveston Bay...
Waters from High Island to Freeport TX from 20 to 60 NM.

&&
weatherguy425
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06Z ECMWF. Curious to see if ensemble envelope continues to consolidate.
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cperk
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06Z Euro 949mb slightly south of Galveston.
Last edited by cperk on Tue Aug 25, 2020 7:23 am, edited 1 time in total.
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cperk wrote: Tue Aug 25, 2020 7:20 am 6OZ Euro 949mb slightly south of Galveston.
Waiting for the North turn will be excruciating.
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Looks like the NHC track didn't shift much (yet) at 4AM

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tireman4
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As they stated in the 4 am package discussion...( and Weatherguy posted it..thank you so much for all you are doing here)

The new NHC prediction is at the eastern edge of the new guidance envelope since
I don't want to bite off on such a large change on just one set of
model runs. But since the storm has been tracking west of forecast
expectations for quite some time, future westward track adjustments
could be required later today.

So I have a feeling you will see a more west track at the 10 am package.
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