MAY 2020

General Weather Discussions and Analysis
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Katdaddy
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Re: MAY 2020

Post by Katdaddy » Fri May 22, 2020 3:48 pm

Flood Advisory
National Weather Service Houston/Galveston TX
429 PM CDT Fri May 22 2020

TXC407-471-222230-
/O.NEW.KHGX.FA.Y.0031.200522T2129Z-200522T2230Z/
/00000.N.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
San Jacinto TX-Walker TX-
429 PM CDT Fri May 22 2020

The National Weather Service in League City has issued a

* Flood Advisory for...
Northwestern San Jacinto County in southeastern Texas...
Southeastern Walker County in southeastern Texas...

* Until 530 PM CDT.

* At 429 PM CDT, Doppler radar indicated heavy rain due to
thunderstorms. Minor flooding is ongoing or expected to begin
shortly in the advisory area. Between 1 and 3 inches of rain have
fallen. Rainfall rates above 2 inches per hour are possible.

Some locations that will experience flooding include...
Huntsville, Huntsville State Park and Crabbs Prairie.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flood Advisory means river or stream flows are elevated, or
ponding of water in urban or other areas is occurring or is imminent.

Turn around, don`t drown when encountering flooded roads. Most flood
deaths occur in vehicles.

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DoctorMu
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Re: MAY 2020

Post by DoctorMu » Fri May 22, 2020 6:47 pm

jasons2k wrote:
Fri May 22, 2020 7:00 am
Latest QPF maps show basically a wall just to our NW.
Another feast or famine.
I'm being squashed by a wall of humidity. No rain, though.

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DoctorMu
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Re: MAY 2020

Post by DoctorMu » Fri May 22, 2020 7:56 pm

Ensemble and Euro are pretty enthusiastic about rainfall during next week, predicting about 2X GFS and Candian models

I waited for the temp to sink below 90°F and heat index below 100°F before mowing the front. Now to water OR not to water...that is the question!

The action doesn't start here until late Sunday night/Monday.

Hedging my bets and set phasers on stun. 1/2 power on the sprinklers.
Attachments
June1.2020.jpg

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DoctorMu
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Re: MAY 2020

Post by DoctorMu » Fri May 22, 2020 8:01 pm

Area Forecast Discussion
National Weather Service Houston/Galveston TX
633 PM CDT Fri May 22 2020

.AVIATION...
Storms near UTS that produce dime size hail around 430pm have
tapered off with the loss of heating. VFR conditions this evening
will eventually fall into MVFR (possibly localized IFR) territory
overnight as stratus fills back in. Similar to today, look for
these to lift and scatter out in the mid and late morning hours.
Cannot rule out some iso/sct afternoon tstms, but confidence in
regards to any impacting an individual TAF site are low whereas
did not include the mention in the 00z TAFs. 47

&&

.PREV DISCUSSION... /ISSUED 402 PM CDT Fri May 22 2020/
SHORT TERM [Tonight through Tomorrow]...
Activity picking up over the northern half of the CWA this after-
noon (likely via colliding boundaries from the seabreeze). To the
N/NE...we are kind of seeing the remnants of the outflow from the
storms that originated over the Southern Plains. Per extrapolated
tracking of these lines...the location(s) of the best lift should
be over our NE counties and points further north the rest of this
afternoon/early evening. Later tonight, near-term progs are still
hinting at the possibility of another MCS over North TX which may
have some isolated activity skirt northern portions of our region
by morning. And once again, confidence remains low with this even
panning out. Tomorrow should be very similar to that of today. It
should be another very warm day, with rain chances very dependent
on more meso features (e.g. seabreeze, outflow boundaries).
41

LONG TERM [Tomorrow night through Friday]...
The early part of next week...or from the second half of the
Memorial Day weekend...is still forecast to be overcast and wet.
There will be a threat for subsequent day flooding through at
least mid-week.

On Sunday, the synoptic set up over the state will be one of a weak
shortwave disturbance swinging through the area along the eastern
side of a western trough whose axis will parallel the Rocky Mountain
spine. Southeastern Texas will be on the eastern side of this
deepening upper level trough.
The shortwave passage from Central
Texas into northeast Texas places us in an even more favorable
position to receive periods of potentially locally heavy rainfall.
From a moisture perspective, early Sunday precipitable water values
increase from about 1.50 inches to around 1.90 to 2.00 inches over
the far northwestern CWA by late afternoon.
The upper levels will
also become more conducive for strong to severe weather Sunday as
jet level flow becomes more diffulent. This has currently placed the
highest PoPs over the (north)western forecast area Sunday. A second
shortwave disturbance rounding the base of the nearly-stationary
western upper trough Monday will likely introduce another round of
showers and thunderstorms from as early as late Sunday night through
early Monday. A low shear and saturated background environment
suggest that slow storm movement within a near saturated column will
increase the risk for locally heavy rain both days. This pattern
will continue on through Monday.


Very little change in the weather pattern is expected through the
end of the month.
An upper level low pressure system is currently
modeled to develop in the base of the aforementioned western trough
and slowly meander over Central Texas.
The low positioning will
favor diverging upper level winds within a more unstable (less
capped) and continued moist environment. Clouds and precipitation
will keep high temperatures near or slightly below seasonal norms. 31

MARINE...
Far interior lower pressure with relation to eastern high pressure
will guarantee a continued onshore wind through early next week. The
only deviation from this regional onshore wind will come in the
event of local shower and/or thunderstorm downdraft air behavior.
The onshore pressure gradient will tighten in the coming days to
periodically have Small Craft Exercise Cautions in effect (primarily
due to sustained 15 to 20 kt winds). This persistent onshore fetch
will also increase sea or swell height going into and through the
holiday weekend. This wind scenario will ultimately strengthen the
rip current as more water is pushed towards the Upper Texas
coastline. Swimmers or those with marine interests need to be highly
mindful of these enhanced rip currents and follow beach hazard
safety guidelines. 31

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 74 90 74 86 70 / 20 20 20 80 70
Houston (IAH) 77 89 76 87 73 / 20 20 20 50 50
Galveston (GLS) 78 86 78 84 76 / 20 20 20 50 40

Pas_Bon
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Re: MAY 2020

Post by Pas_Bon » Fri May 22, 2020 8:18 pm

It is so damn humid in League City. Ugh. Watered the trees/plants for 45mins and I am drenched. Gross. I’m calling the waaaaaambulance on myself.

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don
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Re: MAY 2020

Post by don » Fri May 22, 2020 11:58 pm

Ive noticed that models are starting to trend the heaviest rains more into southeast Texas, and the WPC has also nudge qpf totals up. But who gets the heaviest rains will likely be driven by mesoscale features which cannot be forecast with great accuracy this far out, stay tuned next week may be a busy week.

unome
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Re: MAY 2020

Post by unome » Sat May 23, 2020 5:43 am

"Luchs Like Rain"- I enjoy reading his discussions

Area Forecast Discussion
National Weather Service Houston/Galveston TX
608 AM CDT Sat May 23 2020

.AVIATION [12Z TAF Issuance]...

Generally MVFR across the area to open, but with some variability
down to high IFR at UTS and even some intermittent VFR at the
Houston terminals. Within a few hours, should be VFR area-wide.
Showers N of UTS should miss to the NE before fading off. Onshore
winds continue today, to around 10 kts sustained and some gusts
just below 20 kts.

Tonight, look for gusts to fall off this evening and MVFR to
return overnight. Streamer showers expected to be more numerous in
the pre-dawn hours at the coast, and have put in VCSH from HOU
coastward. Beyond the scope of this TAF cycle, even at IAH, but
more numerous afternoon showers and storms are also expected
tomorrow.

&&

.PREV DISCUSSION /Issued 350 AM CDT Sat May 23 2020/...

.DISCUSSION...

Though many can expect to see another hot, dry day, there will
again be a chance for showers and storms to crop up today - the
harbingers of a more significant change to unsettled weather for
much, if not all, of the coming week.

Since a drifting, cutoff low is likely to be a significant player
for the next several days, forecasting specifics carries more
uncertainty than usual. At the very least, we are looking at
several days with an environment that should be supportive of
showers, thunderstorms, and potentially heavy rainfall. There is
much less confidence in precisely where, when, and even if that
potential will be realized. Ultimately, this may be a situation we
will have to take day to day - evaluate just how supportive the
environment is, and what local and mesoscale factors may combine
with the synoptic environment to determine the threat.

In other words...be ready to check the forecast frequently, and
be ready to adapt quickly. These setups could escalate (it is a
holiday weekend in Houston, after all) or de-escalate (hoping for
this one!) quickly.




.SHORT TERM [Through Sunday Night]...

A look at radar and satellite at this early morning hour does not
look terribly different from 24 hours ago. We are eyeing the
diminishing remnants of a mesoscale convective system coming down
from North Texas for potential impacts on weather in Southeast
Texas. No expectations for thunderstorms, much less severe
weather, as the watch has come to an end and IR imagery shows
cloud tops warming markedly.

I'm leaning more towards another dry night as the MCS spent a
good chunk of the evening making more progress east than south,
and so is even further north than last night's remnant line was at
this hour. Still, there is a small chance some dying showers make
it to our northern reaches before fizzling out completely, and so
I hang onto some slight/low end chance PoPs way up north.

Beyond that, one more day in the diurnal grind. Coastal showers
should be cropping up on the moderate to strong onshore flow any
minute now, and can be expected to impact shore into the early
morning. Beyond that, we'll be on watch to see if the cap can be
defeated this afternoon. For most, I expect the answer is no, and
most should stay dry today. But, I'm also pretty confident that
some isolated updrafts should manage to make it, and give an
unlucky few a shower/thunderstorm this afternoon. HREF ensemble
MIN(!) SBCAPE is largely above 2000 J/Kg this afternoon, so for
the few storms that do manage to fire, we may be able to expect
some gusty winds or small hail, as was seen in Friday's strongest
storms.

More significant change comes to the area on Sunday. We begin with
only a bit of a deviation at first, where we look to see more
effective nocturnal streamer showers near the coast. But from
there, do not expect clouds to scatter out as we have been seeing
of late. Instead, we'll be looking to see what happens as a lobe
of vorticity shears off an upper trough in the northern stream and
drops into Texas. This creates an EXTREMELY difficult forecast for
Sunday. If it drops in too slow or too far west, we could end up
with a situation like the NAM or WRF-NMM, in which a new MCS
fires up well to our west. Or...we could end up like the WRF-ARW
and NSSL WRF, which puts the big rain right over our area.

But this is a setup that makes me somewhat uncomfortable. We have
a synoptic setup that traditionally results in flooding rains for
somewhere in the region. The broader environment should support
heavy rain. And the 00Z HREF probability-matched mean shows a 10
percent contour for exceeding 3 inches in three hours between 18
and 21Z on Sunday, and 50 percent for exceeding one inch. The PMM
QPF itself exceeds three inches in NW Houston, just outside the
loop. We certainly cannot take this model output literally,
especially 30+ hours out. But I do take it seriously, and it is a
plausible outcome. I would rather expect some heavy rain to fall
somewhere...it's more a question to me of exactly where.

Ultimately, we don't need to cancel a big Sunday at the grill
just yet. But it's probably a REAL good idea to have an indoor
alternative at the ready, just in case. We'll be refining the
forecast in the time ahead of us, trying to glean whatever
mesoscale details we can get at as long a range as we can spot
them. In the meantime, plan to check on the forecast more tomorrow
and Sunday morning. I personally vote for this vort lobe to drop
in way east and make the action happen offshore...but I will note
the atmosphere does not care what I want.


.LONG TERM [Monday Through Saturday]...

A deep upper level trough over the Central Plains will extend into
South Central Texas by Monday morning. An upper level low will
develop in the base of the trough and meander over the state for the
next seven days. A series of upper level disturbances will rotate
around the upper low and move across SE TX but timing these
disturbances and the actual placement of the upper low is tricky and
there will likely be other meso scale influences at work. If models
have a handle on things (and they probably don't), the first strong
short wave will rotate around the trough toward Matagorda Bay and
then move NE up the coast. Fcst soundings don't show capping with
convective temps around 82-83 degrees. PW values are near 1.90
inches so it looks like a good chance of showers and storms for the
first half of the day with some drying from the southwest by mid-
afternoon in the wake of the short wave. Another disturbance will
move into the area on Tuesday but fcst soundings show PW values
falling to around 1.70 with capping noted at 850 mb and convective
temps around 85-86 degrees. Rain chances on Tues look less than
Monday but the GFS mass fields show a 5 inch QPF bullseye over
Harris County on Tuesday but the met parameters just don't support
it. Will carry likely PoPS for now but confidence is low.

By Wednesday, the GFS has the upper low over southern OK while the
ECMWF has the low over South Central Texas. The placement of the low
as it will affect moisture transport into the region. If the GFS is
correct, PW values will drop to between 1.25 and 1.40 inches with
disturbances rotating around the upper circulation to the north of
the HGX CWA. Under this scenario, SE TX will only get scattered
showers but if the southern solution (EC) is correct, showers and
thunderstorms will be likely all week long as moisture transport
into the region will remain strong. Ensemble guidance seems to
support the the northern position but the EC and GEM deterministic
guidance remain bullish with the more southern location. Have leaned
toward the ensemble guidance and trended a bit drier mid week but
again confidence is low.

The upper low does eventually sink south toward the end of the week
and showers and thunderstorms should increase in coverage. PW values
increase to around 1.80 inches Fri/Sat and fcst soundings show no
capping and convective temperatures in the lower and middle 80's.
43


.MARINE...

Onshore winds will continue through the holiday weekend. Though
wind speeds are not always expected to be at least 15 knots today,
the long, persistent fetch from southeast winds have seas elevated
to levels that would be more expected of winds above the SCEC
threshold, and so there are caution flags in effect today. These
may need to be extended even further, depending on how much, if at
all, seas diminish. Unsettled weather can be expected Sunday and
well into next week with multiple periods of showers and storms
through the week. Expect winds to become more variable towards the
middle of next week, finally breaking the long stretch of onshore
flow...at least for short stretches.


.CLIMATE...

Galveston set a new record high minimum temperature yesterday. Its
low of 80 degrees bested the old record of 78. The old record had
a long, venerable life span of one year - last set May 22, 2019.
The 80 degree low also comes in just one degree shy of the monthly
record high minimum temperature. An 81 degree low is the record
for every day from the 27th to the 31st of May. The oldest of
these 81 degree marks is from 1996 (28, 29) and was last seen two
years ago in 2018 (30, 31). Nine days in the month remain to match
or best that mark.

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL) 91 74 88 70 83 / 20 20 60 50 70
Houston (IAH) 91 76 89 73 84 / 20 30 70 50 70
Galveston (GLS) 85 78 85 75 82 / 20 40 50 50 60

&&

.HGX WATCHES/WARNINGS/ADVISORIES...

TX...High Rip Current Risk through this evening for the following
zones: Brazoria Islands...Galveston Island and Bolivar
Peninsula...Matagorda Islands.

GM...SMALL CRAFT SHOULD EXERCISE CAUTION through 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.


&&

$$

DISCUSSION...Luchs
SHORT TERM...Luchs
LONG TERM...43
AVIATION...Luchs
MARINE...Luchs
CLIMATE...Luchs/43

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jasons2k
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Re: MAY 2020

Post by jasons2k » Sat May 23, 2020 8:04 am

Fantastic discussion from the NWS. Stay safe everyone.

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Re: MAY 2020

Post by srainhoutx » Sat May 23, 2020 8:21 am

Saturday morning weather briefing from Jeff:

Stormy weather pattern will begin over the weekend and last into much of next week.

Complexes of thunderstorms that form over north and west TX each afternoon have moved toward SE TX each night, but fallen apart before reaching the area. Seabreeze front and outflow boundaries from the north were able to overcome the cap across the northern portions of the area yesterday afternoon and resulted in the formation of a couple of strong thunderstorms. Today will be similar to yesterday with the chance of a few strong thunderstorms mainly in the College Station to Lake Livingston region.

An upper level trough will advance into TX on Sunday and this will likely result in some sort of complex of weather moving into the area Sunday afternoon and evening. Not sure exactly how this will play out, but parameters will be in place on Sunday afternoon and evening for a complex of storms to approach from the W or WNW and move slowly across the region. There will be some severe threat and a heavy rainfall threat with this complex. Short range models are really hitting the US 59 corridor from Wharton to Houston for some heavy rainfall, but I don’t have much faith in any of the solutions at the moment.

Upper level trough cuts off into an upper level low over TX on Monday and this feature meanders around the state for much of the week. Rain chances will remain high each day, although it will likely not be significant impacts each day. Each days forecast will be driven somewhat by the activity from the day before. So Monday will depend and where and how significant the activity is Sunday afternoon and evening. Parameters will continue to be in place for heavy rainfall and over time grounds will begin to saturate leading to increasing run-off and rises on area watersheds, especially rivers due to the widespread nature of the rainfall.

Rainfall amounts of 1-3 inches can be expected through early next week with isolated totals of 4-5 inches. Totals could be higher should storms slow or train over any area for an extended period of time. This is certainly the type of pattern where significant rains can occur.
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davidiowx
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Re: MAY 2020

Post by davidiowx » Sat May 23, 2020 10:10 am

Wow some of those hail pics from Burkbunett are insane! I don’t think I’ve ever seen hail that big and to go through roofs is just scary. Hope we get some nice good rains over the next few days. Please no floods like we’ve been getting accustomed too!

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