May 2023

General Weather Discussions and Analysis
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Ptarmigan
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It seems like late May is wetter. I ran a statistical analysis of May rainfall from 1970 to 2022 at Bush Intercontinental Airport

May 1-14
Mean: 0.17
95% Confidence Interval
Lower: 0.13
Upper: 0.20
Standard Deviation: 0.51
Wettest: 5.10 (5/3/1981)

May 15-31
Mean: 0.18
95% Confidence Interval
Lower: 0.14
Upper: 0.22
Standard Deviation: 0.61
Wettest: 6.87 (5/19/2000)

It turns out mid to late May is wetter on average than early May.
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don
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DoctorMu wrote: Wed May 10, 2023 9:15 pm
Cpv17 wrote: Wed May 10, 2023 4:02 pm
Stratton20 wrote: Wed May 10, 2023 3:34 pm Cpv17 No i like tornadoes and floods, i just hate it when those events occur in heavily populated areas, hate seeing all the damage reports come in, but if i had to choose a kind of weather that can be fun without causing serious problems is snow, who doesn’t like seeing flakes fly in the sky here?
Oh ok, I gotcha! I knew for sure that you liked some wintry weather because that’s how me and you first met to begin with lol. I’m not sure if I like tropical weather or wintry weather more. I might give the slight edge to wintry weather just cuz it’s more rare to see a big snowstorm down here compared to a tc. But I love basically any weather extreme. I even love record breaking heat just cuz I think it’s fascinating.

Anyway…..

The CPC now has this:

Image

Uh oh ;)
That's almost a safe bet though based upon climo and the target area centers over Louisiana. Late May and June (7.07 in) are the rainiest time of year in Lafayette, LA. :lol:
June is the wettest month on average in Houston also.
Stratton20
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Yeah i still dont see what the CPC is seeing during the 18-21st timeframe bit of a head scratcher to be honest
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jasons2k
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Update from Jeff:
Additional chances for showers and thunderstorms this weekend into next week.

Pesky mid level low responsible for the recent rainfall is now over Arkansas with the local air mass having dried some over the last 12 hours. With heating today a few showers and thunderstorms will be possible. Next developing storm system over the SW US will move into W TX this weekend and place portions of the state under a very favorable pattern for heavy rainfall and flooding…this looks to occur mainly to the west of our region.

Today and Friday will feature lower rain chances as the area falls between weather systems, rain chances increase from west to east over the weekend as the next slow moving system approaches. Guidance continues to suggest the greatest rainfall and flood potential will focus across SW TX into SC TX Friday-Sunday, but portions of the western sections of SE TX may be near the heavy rainfall axis at times. There will likely be a sharp gradient in rainfall from west to east with areas east of I-45 likely seeing less than .50 of an inch this weekend and areas from Columbus to College Station possible 2-3 inches. Will need to see how thunderstorm complexes evolve over SW and C TX through the period.

Overall pattern remains unsettled into next week with a front trying to approach and move into the area early in the week which will likely result in scattered showers and thunderstorms.
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don
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Stratton20 wrote: Thu May 11, 2023 12:12 am Yeah i still dont see what the CPC is seeing during the 18-21st timeframe bit of a head scratcher to be honest
They're seeing a stalled or slow moving frontal boundary with an active subtropical jet.Doesn't make sense to put too much stock in qpf amounts in this range.They're looking at the overall 500mb pattern and probably analogs to determine if there's a chance of heavy precip.Think of it as a early warning system just letting you know the pattern is there for heavy rain but they're not saying its gonna happen just a possibility based on the 500mb pattern.(Remember these are experimental maps and they only have a 20% chance of excessive rainfall for a reason).
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don
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Like Jeff mentioned we need to keep an eye on Saturday (especially areas west of I-45). Some models are showing the potential for a slow moving MCS to maintain it's strength longer than currently anticipated.Not expecting anything "crazy" at the moment but something to watch since grounds are saturated.
fv3-hires_ref_frzn_scus_57.png
rgem_mslp_pcpn_frzn_scus_62.png
Cpv17
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don wrote: Thu May 11, 2023 1:23 pm Like Jeff mentioned we need to keep an eye on Saturday (especially areas west of I-45). Some models are showing the potential for a slow moving MCS to maintain it's strength longer than currently anticipated.Not expecting anything "crazy" at the moment but something to watch since grounds are saturated.

fv3-hires_ref_frzn_scus_57.pngrgem_mslp_pcpn_frzn_scus_62.png
It looks like the 12 GFS shifted slightly east with some of the heavier totals, did it not? I haven’t had a chance to fully look at it yet.
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jasons2k
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Emptied another 1.38” from yesterday
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DoctorMu
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Ptarmigan wrote: Wed May 10, 2023 10:31 pm It seems like late May is wetter. I ran a statistical analysis of May rainfall from 1970 to 2022 at Bush Intercontinental Airport

May 1-14
Mean: 0.17
95% Confidence Interval
Lower: 0.13
Upper: 0.20
Standard Deviation: 0.51
Wettest: 5.10 (5/3/1981)

May 15-31
Mean: 0.18
95% Confidence Interval
Lower: 0.14
Upper: 0.22
Standard Deviation: 0.61
Wettest: 6.87 (5/19/2000)

It turns out mid to late May is wetter on average than early May.
Exactly. The same is true in CLL. Daytime heating, No cap. Seabreeze, Meandering FROPAs, s/w's still possible. ULL bowls through occasionally.
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DoctorMu
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don wrote: Thu May 11, 2023 1:12 pm
Stratton20 wrote: Thu May 11, 2023 12:12 am Yeah i still dont see what the CPC is seeing during the 18-21st timeframe bit of a head scratcher to be honest
They're seeing a stalled or slow moving frontal boundary with an active subtropical jet.Doesn't make sense to put too much stock in qpf amounts in this range.They're looking at the overall 500mb pattern and probably analogs to determine if there's a chance of heavy precip.Think of it as a early warning system just letting you know the pattern is there for heavy rain but they're not saying its gonna happen just a possibility based on the 500mb pattern.(Remember these are experimental maps and they only have a 20% chance of excessive rainfall for a reason).
NWS has a 60% shot at rain both Saturday and Sunday. We have the ingredients. We have the heat. We have the stirring spoon.
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DoctorMu
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Climo doing its thing unimpeded this weekend?

Area Forecast Discussion
National Weather Service Houston/Galveston TX
616 PM CDT Thu May 11 2023

...New AVIATION...

.SHORT TERM...
(This evening through Friday Night)
Issued at 350 PM CDT Thu May 11 2023

Shower and thunderstorm activity has been generally limited today,
as an initial round of thunderstorms that formed earlier this
afternoon as weak shortwave energy traversed the area struggled to
materialize further with activity nearly fully diminished as of 330
PM CDT. Given the low precipitation coverage and diurnal breaks in
the prevailing cloud cover, we`ve been able to warm up into the
mid/upper 80s at most locations. Combined with dew points in the
70s, this has produced heat index values in the 90s, a trend that we
will expect to see continue for the next several days.

Cloud cover will fill back in overnight, which will inhibit
nocturnal radiative cooling and thereby keep most locations in the
low to mid 70s. While dew point depressions will once again be quite
low, fog will continue to be inhibited by persistent 10mph SE winds.
That being said, local areas of patchy fog cannot fully be ruled out
through the early morning hours, much like we saw last night.

Friday should generally be similar to today, with broken skies
developing with daytime heating and highs rising into the mid to
upper 80s. Diurnal heating, along with persistent deep moisture (PWs
remain around 1.5-1.7in) and the passage of a weak disturbance in
the midlevels will allow for the development of isolated showers and
storms during the afternoon, mainly north of I-10. Much like today,
any storms that do develop are unlikely to produce any significant
rainfall amounts. Overnight, we once again see a return to overcast
skies and low temperatures in the low to mid 70s.

&&

.LONG TERM...
(Saturday through next Wednesday)
Issued at 350 PM CDT Thu May 11 2023

On more of a statewide scale, this weekend looks to have a pretty
impactful rain event coming up. However, the focus for this event
continues to look like it will be west of our area. Upper ridging
over the Northern Gulf will look to do a pretty decent job of
holding off an upper trough digging into West Texas this weekend.
Of course, this sets up a pretty impressive channel of Gulf
moisture flow that even over our area is pushing precipitable
water values to around or above the 90th percentile in the
ensemble means for both NAEFS and the Euro.

Fortunately for us, and not so fortunately for our western
neighbors, it continues to look as if the balance between trough
to our west and ridge to our east will provide the best overlap of
moisture and forcing outside of our area, and the PoPs reflect
that. It is a fairly sharp gradient in rain chances though, and
the far western portions of our forecast area may get clipped by
the more organized event. But for most of Southeast Texas, expect
something more akin to an amped up version of the usual diurnal
pattern. We may see higher than typical chances of rain in the
night and morning hours, but we`ll still be focused on the
afternoon for the greatest coverage and intensity of showers and
storms. With available moisture so high, we will still want to be
on the lookout for localized, briefly intense rain...though this
is also not too far out of the ordinary for our area this time of
year.


Ridging asserts itself more strongly early next week
, and we dial
that amped up pattern back down to a more typical tone Monday
while the potential for heavier rain to our west also starts to
wane. Look for a weak front late Monday night into Tuesday morning
as a decently strong center of high pressure drops into the Great
Plains from the Canadian Prairies. Don`t expect a whole lot from
this front other than more variable winds for the middle week, but
that may at least give us a temporary disruption from the
persistent onshore flow that will dominate the period leading up
to it. Put a bit of emphasis on the "may" part, though. Guidance
is already starting to back off a bit on this whole front idea.
And though it still brings it through, we see less of a period of
established offshore flow, and more a period of variable winds,
especially closer to the coast.

&&

.AVIATION...
(00Z TAF Issuance)
Issued at 616 PM CDT Thu May 11 2023

Mostly MVFR and possible IFR ceilings developing this evening and persisting
overnight. S to SE winds should stay elevated enough to prevent fog
formation. Lingering fog/haze is expected for GLS. Area conditions improve
in the morning with ceilings lifting/breaking and anticipate VFR for
the afternoon with S to SE winds around 10-15 knots. Look for more evening
and overnight clouds heading into the Friday night through Saturday
morning time period with weaker S to SE winds.

42

&&

.MARINE...
Issued at 350 PM CDT Thu May 11 2023

Isolated to scattered showers and storms are possible each day
into early next week. The best potential for storms will be over
the weekend. A long southeasterly fetch will also persist during
this time, resulting in periods of elevated seas. These winds
will periodically reach the threshold for small craft to exercise
caution or a small craft advisory, especially during the overnight
to early morning hours. Expect winds to become lighter and more
variable in the middle of next week as a weak front makes its way
offshore.

At the shore, rip currents look to be an issue as long as the
persistent onshore flow continues. Elevated water levels may also
be a continuing concern as well, though it appears the highest
tides will be during this afternoon`s cycle, peaking out around 3
feet above MLLW.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 74 88 72 84 / 10 20 20 60
Houston (IAH) 75 87 74 85 / 10 10 10 50
Galveston (GLS) 78 82 76 82 / 10 10 10 30
Cpv17
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Saturday and Sunday could be interesting in Wharton County. The WPC has me just a few miles away from the moderate risk area on Saturday.
Stratton20
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Some of the overnight mesocale runs do try to bring in a MCS to se texas from central texas fwiw
Cpv17
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Colorado, Wharton, Jackson, and Matagorda counties have been added to the flood watch.
Cpv17
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The 6z HRRR is much wetter for areas west of 45 compared to the 0z run. It looks more like the FV3 model.
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don
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imfdage1.png
imreage3.png
Cpv17
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don wrote: Fri May 12, 2023 10:19 am imfdage1.pngimreage3.png
Judging by some of the latest guidance, they might need to shift some of that east a lil bit.
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tireman4
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000
FXUS64 KHGX 121129
AFDHGX

Area Forecast Discussion
National Weather Service Houston/Galveston TX
629 AM CDT Fri May 12 2023

...New AVIATION...

.SHORT TERM...
(Today through Saturday Night)
Issued at 415 AM CDT Fri May 12 2023

Another warm and muggy day across Southeast TX today. Early this
morning, sfc obs reported temperatures in the upper 70s with
dewpoints in the mid to upper 70s, so it definitely feels muggy
out there. Widespread stratus/low clouds will stick around through
much of the morning hours, before scattering out in the
afternoon. Peak heating and abundant Gulf moisture may allow a few
showers and thunderstorms to develop north of I-10 through early
evening. Highs mainly in the 80s to near 90 can be expected.

The main weather feature and concern for later tonight through
Sunday revolves around additional showers and thunderstorms,
resulting in heavy rainfall on already saturated grounds. Southeast
TX will be positioned between an upper lvl ridge to our east and a
mid level trough developing over northern MX/West TX today. This
scenario will continue to increase moisture advection across the
region with PWs around 1.7 to 1.9 inches. These values are near the
90th percentile of climatology. While most of the dynamic forcing
should remain to our west, latest guidance bring several mid-lvl
shortwaves in advance of the parent trough late tonight into
Saturday. Steep lapse rates, moderate LLJ and decent bulk shear (~30
knots) will be enough to develop and maintain any thunderstorms.
In fact, most guidance keeps suggesting a somewhat organized MCS
tracking eastward into our region through late Saturday night.
Though confidence still remains moderate as it will depend on the
evolution of these storms over west/central TX.

With that being said, increasing rain and storm chances can be
expected from west to east tonight into the rest of the short-term
period. Both, excessive rainfall and isolated to scattered severe
thunderstorms will be possible as the system tracks east with large
hail and damaging winds as the main risks. The greater potential for
heavy rainfall and strong to severe thunderstorms will be across our
western and southwestern counties. Rainfall totals of 1 to 2 inches
can be expected, with isolated localized higher amounts. While these
rainfall totals would normally not be a concern (flash flood
guidance shows values at or above 3 inches over most of the area),
trends will need to be monitored especially for our southwestern
Counties where impacts on creeks and rivers and street flooding can
be expected. A Flood Watch has been issued for Colorado, Wharton,
Jackson and Matagorda Counties from late tonight through Sunday
evening. More details in the Hydrology section below.

JM

&&

.LONG TERM...
(Sunday through Thursday)
Issued at 415 AM CDT Fri May 12 2023

Unfortunately, Mother`s Day will be a rainy one, so it`d probably be
for the best to make any celebration plans indoors. On the plus
side, it`ll be the perfect day for moms (and everyone else) to
sleep in! The upper level low and subsequent surface low will
still be over West TX on Sunday morning with a well established
moisture axis just off to our west. PW values over our area will
be near or above the 90th percentile (~1.74"), so locally heavy
rainfall is possible in Southeast TX. However, the best chances of
seeing this heavy rain will be west of the I-45 corridor. Still
expecting a rather tight QPF gradient between the 2"+ totals and
0.5"-1.0" totals, and the I-45 corridor serves as a decent
boundary although the higher totals (in our area) will likely be
about 30-50 miles to west of the interstate. Due to the expected
rainfall along with the recent rainfall from earlier this week,
there is a marginal risk (level 1 out of 4) for excessive rainfall
on both Sunday and Monday.

The upper level low gets dragged northward on Sunday by a
retrograding upper level low transitioning from the Four Corners
region back towards the Pacific Coast. The lingering moisture and
a steady influx of shortwaves wrapping around a building mid level
ridge early next week will lead to persistent rain chances
throughout the week. A weak cold front still looks to at least
approach us on late Monday/early Tuesday, but at best this will
just offer a shift in wind direction. This actually does impact
the temperature forecast...just not in the direction that you`re
hoping for. First, I wanna mention that on Monday afternoon, a
pocket of drier air (PW values ~1.3"-1.4") slides over the area.
With 500mb heights increasing as well, we`ll see quite a bit of
sun which will lead to high temperatures approaching the 90°F
mark. Surface winds on Tuesday will be a mixed bag due to the
front, but they are not expected to be predominantly onshore...at
least not for a long enough period of time to fully replace the
slightly drier air. The end result...another day of high
temperatures approaching the 90°F mark.

Going into midweek, an upper level trough begins to dig down into
the northeast CONUS and squashes our ridge, so we do get a brief and
slight relief from the hot temperatures. This trough does amplify
another upper level ridge over the western CONUS, which places us in
westerly to northwesterly flow aloft. Numerous shortwaves will be
able to sweep through. So, with a fair amount of moisture remaining
in place, we`ll continue to see chances for diurnally driven
showers/storms through the rest of the long term period. I used
the word "brief" when I referenced relief from the hot
temperatures earlier because there are signs of a warming trend
at the end of the week. 500mb heights begin to increase again
along with southwesterly flow aloft becoming established at
850mb. We may be on the doorsteps of the 90°F mark once again
going into next weekend. Yay... :(

Batiste

&&

.AVIATION...
(12Z TAF Issuance)
Issued at 620 AM CDT Fri May 12 2023

Widespread MVFR to IFR conditions due to low clouds/stratus should
persist through late morning. Then, expect SCT to BKN ceilings
along with gusty south to southeast winds in the afternoon. The
exception will be around the coastal terminals where MVFR
ceilings look to remain through the day. Isolated thunderstorms
will be possible in the afternoon, mainly for terminals north of
IAH, including CLL. MVFR to IFR conditions return this evening
along with increasing rain and storm chances from west to east
towards the end of this TAF cycle.

JM

&&

.MARINE...
Issued at 415 AM CDT Fri May 12 2023

Light to occasionally moderate southeasterly flow continues to
prevail. There are currently caution flags up for the bays and Gulf
waters that extends into tonight, but will likely need to be
extended through the weekend for at least the offshore waters due to
elevated seas from the persistent onshore flow. This prolonged
period of onshore flow will also continue the trends of a moderate
to high risk of rip currents. Water levels during high tide today
are expected to remain below 3 ft MLLW. Rain chances increase over
the weekend, especially over the western waters, as an upper level
disturbance approaches. Onshore flow will continue until late
Monday/early Tuesday when a weak cold front attempts to move
offshore and could bring a brief period of light offshore flow.

Batiste

&&

.HYDROLOGY...
Issued at 415 AM CDT Fri May 12 2023

Due to the recent rainfall from earlier this week, there are
currently two gauges along the Lavaca/Navidad Rivers that have a
Flood Warnings. EDNT2 (Edna, TX) is currently in minor flood stage
and is expected to remain above flood stage through at least this
afternoon. LSNT2 (Strane Park, TX) is forecast to reach minor flood
stage this afternoon. Widespread heavy rainfall is expected this
weekend to our west in the Hill Country area, so we will have to
keep an eye on downstream impacts especially along the
Lavaca/Navidad River where multiple flood gauges are either in or
forecast to go into at least action stage.

This was part of the rationale for issuing the Flood Watch
that goes into effect for Colorado, Wharton, Matagorda, and
Jackson Counties late tonight through Sunday evening. These
locations received excessive rainfall earlier this week with some
observed totals of over 6" near Matagorda Bay. With additional
heavy rainfall expected over the weekend, there is an increased
risk for flooding in these areas.

Batiste

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 88 72 84 69 / 20 50 60 40
Houston (IAH) 87 73 84 71 / 20 30 50 30
Galveston (GLS) 82 76 82 75 / 10 30 40 30

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...Flood Watch from late tonight through Sunday evening for TXZ210-
226-235-236-335-336-436.

High Rip Current Risk through this evening for TXZ436>439.

GM...Small Craft Should Exercise Caution through late tonight for
GMZ330-335-350-355-370-375.

&&

$$

SHORT TERM...JM
LONG TERM....Batiste
AVIATION...JM
MARINE...Batiste
Stratton20
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Models are sniffing out another front in the medium range, but it wont make it here or it will stall out, next week looks like a return to big suck weather as high pressure looks to dominate our region, lovely🥵😑hope we can keep daily rain chances around!
weatherguy425
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Stratton20 wrote: Fri May 12, 2023 12:11 pm Models are sniffing out another front in the medium range, but it wont make it here or it will stall out, next week looks like a return to big suck weather as high pressure looks to dominate our region, lovely🥵😑hope we can keep daily rain chances around!
On the contrary, a continued chance of rain (though not as widespread) across portions of the state and average to cooler-than-average weather is expected. While it is getting to be the time of year when fronts struggle to make it this far south… the front you mentioned has some good model support and may actually clear the area - boosting the rain chance ahead of it, and allowing cooler and drier air to briefly works its way in.
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