August 2021: Major Hurricane Ida/SE Louisiana Landfall

[Stratton20]

Jasons2k probably haha but it is something to watch, since thus is within a 10 day period on the model it definitely bear’s watching

[DoctorMu]

While a stronger storm could erode the ridge a little it wouldn't be enough for Grace to be a threat to us, the ridge is just too strong. The farthest north Grace could get would be northern Mexico, and even that doesn't seem likely.

BTW be safe Srain, i see several tornado and flash flood warnings in your area.It looks rough up there right now.

Very tough day across the Smoky Mountains where some locations in Western NC have surpassed 13 inches of Very heavy tropical rainfall with constant Flash Flood Warnings being issued as well as Tornado Warnings across the Region. Fortunately Haywood County has escaped any Tornado risks, but flash flooding and landslides are common throughout our Area. I've measured 7 inches of rain since 7 AM this morning and that sort of rainfall in the Mountains spell big time trouble. The circulation of Fred is just to my W now and that should bring an end to the heavy rainfall for my part of the Smokies.

My goodness...I'm glad you're safe.

Rivers turn into flood quickly in the mountains with mega rain....and when the carry mud, cars, streets and parts of towns can be removed rapidly.

[jasons2k]

A few hours late, but this was in the inbox this morning from Jeff:

Heavy Rainfall Threat

Deep tropical moisture is in place this morning with onshore flow of 10-15kts and this combined with the approach of an upper level trough and favorable jet stream dynamics point toward an active day of showers and thunderstorms. Given PWS of 2.2-2.3 inches over the region, excessive short term rainfall rates will be possible in the stronger storms that may lead to rapid onset street flooding. Storm motions along the coast this morning have been in the 5-10kt range, but outflow boundary collisions or cell training may support slower motions and the threat for intense rainfall over certain areas.

Ridge of high pressure will be building westward starting on Thursday and expect rain chances to begin to subside, but still some scattered chances around on Thursday. Heat arrives over the weekend into early next week with temperatures into the upper 90’s and heat index values nearing advisory levels of 108.

TS Grace:
Awaiting incoming USAF mission data this morning, but surface observation from the Cayman Islands indicate Grace is intensifying with gusts over 70mph reported on the islands. The overall convective pattern with Grace is now well developed, although the center may be near the western edge of the large mass of thunderstorms. Upper level outflow has continued to improve and Grace is likely well on the way to becoming a hurricane.

There have been no changes to the forecast track and Grace will move almost due west and into the Yucatan later today/early Thursday and then across the Bay of Campeche and a second landfall in eastern MX early this weekend. Strong ridge of high pressure building west along the US Gulf coast will keep Grace well south of the TX coast.

There are some questions on the intensity forecast, as Grace looks poised to have a period of intensification while crossing the NW Caribbean Sea today. Sea surface conditions in the NW Caribbean area very warm and strongly support intensification, while the atmospheric conditions are generally marginal with some westerly shear still impacting Grace. Grace will likely become a hurricane this morning and continue to intensify up until landfall over the eastern Yucatan later today/early Thursday. Once over the Bay of Campeche, conditions look ideal for more rapid intensification and Grace could be stronger than the current 85mph forecast when it reaches the coast early this weekend.

Indirect impacts are expected along the TX coast from Grace which include the arrival of long period swells as early as late Thursday, but more likely on Friday and into the weekend. Current WW3 guidance has 6-9 ft across the Gulf waters by Saturday and this will combine at times of high tide to produce wave run-up along the beaches and possibly minor coastal flooding. ETSS is showing water levels of 3.0-3.5 MLLW (barnacle level) this weekend which is near the threshold that can cause some minor issues along the coast. Rip currents along the beaches will be significant Friday-Sunday.

[Texaspirate11]

LOVE that rain with no name - I'm good.

[Cromagnum]

Yeah, for those somehow disappointed in Grace staying away from us, that language about being stronger than forecast should raise your eyebrows. Nobody benefits from a strengthening hurricane bearing down.

[tireman4]

00
FXUS64 KHGX 181050
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
550 AM CDT Wed Aug 18 2021

.AVIATION...

Deep tropical moisture coupled with a weak trough of low pressure
and daytime heating will provide area TAF sites with a good chance
of showers and thunderstorms. Will probably need some TEMPOs later
this morning into the afternoon. Showers will wane after sunset
but may not completely end as PW values remain very high. The
upper level trough moves east on Thursday and rain chances will be
lower. Mainly VFR conds expected today and tonight with brief
windows of MVFR in shra/tsra. 43

&&

.PREV DISCUSSION... /ISSUED 328 AM CDT Wed Aug 18 2021/

SHORT TERM [Through Thursday Night]...

A weakening upper level trough of low pressure extends from the
western Great Lakes into SE TX. Satellite derived PW imagery shows
PWATs between 2.20 and 2.30 inches. Models seem to have a good
handle on moisture and both the GFS and NAM fcst soundings show PW
values near the satellite values. Soundings also show low convective
temperatures today (mid 80`s) and no capping. Toss in some weak jet
dynamics with the aforementioned parameters and it looks like there
will be a good chance of showers and thunderstorms areawide. The
relatively low convective temperatures and the best jet dynamics
look to be this morning into the early afternoon so would expect an
earlier start to convection today. There will be pockets of locally
heavy rain, but when and where will be determined by meso-scale
influences. Parts of SE TX have been outlooked by the Weather
Prediction Center in a Marginal Risk for excessive rainfall today.
Unlike the past couple of nights, not sure convection will end with
the loss of heating and there could be some scattered showers over
the far NW zones and additional shra/tsra moving inland along the
coast. Cloud cover and slightly stronger winds will allow MinT
values to remain warmer than normal tonight and locations near the
coast/bays will probably stay in the lower 80`s with mid/upper 70`s
elsewhere.

Thursday will start out warmer and the upper level trough will have
shifted east while upper level ridging begins to develop over the
Deep South. Short term guidance remains aggressive with rain chances
but there should be more subsidence associated with the ridge so
will compromise between the aggressive CAMs and the drier global
models. PW values will be between 2.20 and 2.30 inches so where it
does rain, some of the totals could be locally heavy. 850 mb temps
warm so will raise MaxT values back into the mid 90`s. With the loss
of heating and the building ridge, any residual showers should end
during the evening. MinT values will again remain warm with lows in
the mid 70`s inland and lower 80`s along the coast. 43

LONG TERM [Friday Through Wednesday]...

Friday will have the highest chances of some diurnally driven
showers and thunderstorms. Some isolated afternoon precipitation
will be possible along the coast through the weekend, but building
high pressure will keep the coverage limited. This high pressure
will not only keep minimal rain chances over the weekend and into
next week, but also help bring the heat to SE Texas. High
temperatures will be in the mid to upper 90s Friday and Saturday,
but climb into the upper 90s and into the triple digits Sunday
through Wednesday. The ridge of high pressure will keep Tropical
Storm Grace on its westward trek across the Bay of Campeche and
into eastern Mexico over the weekend. Limited direct impacts are
expected from Grace to SE Texas, though will bring increase rip
current risk through Sunday. So if you are planning on taking a
trip down to the beach to escape the heat, make sure to use safe
beach practices. Additional marine impacts are expected from
Grace, but more on that in the Marine section below.

Fowler

MARINE...

Light to moderate onshore flow of 10 to 15 knots is expected through
today with a slight increase to 15 to 20 knots overnight tonight
through Saturday. Wave heights of 3 to 4 feet are expected through
Thursday evening, but will increase to 6 to 9 feet Friday afternoon
through Saturday morning. Small Craft Advisories will likely be
needed during this timeframe. This increase in wave heights is due
to Grace moving through the southern Gulf. Tropical Storm Grace
continues its trek through the western Caribbean and is expected to
strengthen into a Hurricane later today before making landfall in
the Yucatan Peninsula early Thursday morning. It will continue
westward through the Bay of Campeche on Friday and then make a
second landfall in eastern Mexico. Some of the outer rainbands may
make it to our offshore waters Friday afternoon, but the main
impacts from Grace will be the increased seas, increased rip current
risk through the weekend, and a possibility of some minor coastal
flooding. Wave run-up combined with high tides around 3.5ft above
MLLW could lead to some minor coastal flooding Friday and
Saturday.

Fowler

PREV DISCUSSION /Issued 1141 PM CDT Tue Aug 17 2021/...

AVIATION...

Monitoring late evening areas of SHRA/TSRA to the N thru NW of the
UTS and CLL sites. For now, think this activity will stay out of
TAF areas, but will amend if needed. This activity and its associated
boundaries in combination with a persistent onshore flow and daytime
heating should result in increasing SHRA/TSRA coverage across SE TX
beginning as early as the overnight hours and continuing during the
day on Wednesday. VFR conditions can be expected outside of the rain
areas, and occasional MVFR/IFR ceilings and/or visibilities can be
expected in association with the storm activity. Expect things to begin
to quiet down late in the afternoon through the evening with VFR conditions
overnight Wednesday night through Thursday morning. 42

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 92 78 95 77 96 / 50 30 30 0 20
Houston (IAH) 92 80 95 79 96 / 70 40 40 10 30
Galveston (GLS) 90 83 91 84 91 / 60 50 40 30 30

&&

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

$$

Discussion...99
Aviation/Marine...99

[jasons2k]

Yeah, for those somehow disappointed in Grace staying away from us, that language about being stronger than forecast should raise your eyebrows. Nobody benefits from a strengthening hurricane bearing down.

Exactly. I’ll take today’s no-name rain to replenish the garden any day and will gladly wave Grace on as she passes by. Hopefully she avoids populated areas.

[captainbarbossa19]

Interestingly enough, there is a chance that Grace redevelops after it emerges into the EPAC. Also, Henri is getting closer and closer to a potential New England impact.

[tireman4]

Speaking of August Storms......

[DavidH]

LOVE that rain with no name - I'm good.

"Rain w/ no name" I'm gonna put that in my repertoire

[cperk]

Speaking of August Storms......

Boy do i remember Alicia.

[don]

Looks like the GFS isn't alone anymore with the gyre system next week.Now the Canadian is showing the same thing fwiw.
Btw theirs a lot of storms out there today,more people should see rain today than the last few days.

[Stratton20]

Don yup CMC and the GFS both sniffing a CAG storm now

[mcheer23]

Don yup CMC and the GFS both sniffing a CAG storm now

GFS ensembles are active as well.

[DoctorMu]

LOVE that rain with no name - I'm good.

"Rain w/ no name" I'm gonna put that in my repertoire

Out of the desert with the rain with no name
It felt good to be back in the rain
In the desert, you can't remember your name
'Cause there's so much sun to give your lawn major pain

La, la, la, la, la, la
La, la, la, la, la, la
La, la, la, la, la, la
La, la, la, la, la, la

[Cpv17]

Don yup CMC and the GFS both sniffing a CAG storm now

GFS ensembles are active as well.

I’m not so sure if it’ll all just slam into Mexico but that’s 10 days out or so, who knows what’ll happen.

[don]

Don yup CMC and the GFS both sniffing a CAG storm now

GFS ensembles are active as well.

Yep...

[jasons2k]

LOVE that rain with no name - I'm good.

"Rain w/ no name" I'm gonna put that in my repertoire

Out of the desert with the rain with no name
It felt good to be back in the rain
In the desert, you can't remember your name
'Cause there's so much sun to give your lawn major pain

La, la, la, la, la, la
La, la, la, la, la, la
La, la, la, la, la, la
La, la, la, la, la, la

Best post in awhile.

Thundering here.

[Cromagnum]

CAG = Central America Gyre ?

[tireman4]

Central American Gyre....

A Central American Gyre is a circular wind flow that develops near Central America. It forms when the winds flow cyclonically, or counter-clockwise, around a broad area of low pressure over the Central American isthmus