MAY 2020

General Weather Discussions and Analysis
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djmike
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Re: MAY 2020

Post by djmike » Sat May 23, 2020 1:33 pm

don wrote:
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.
Probably me in Beaumont. Lol. It never fails...
Mike
Beaumont, TX
(IH-10 & College St. area)

Andrew
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Re: MAY 2020

Post by Andrew » Sun May 24, 2020 6:59 am

Looks like we should have a chance of rain most of this next work week. Models still have some differences on where the heaviest rain will setup but the synoptic setup is very similar to some of the previous heavy rain makers. The key here of course will be where does that heavy rain fall.
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unome
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Re: MAY 2020

Post by unome » Sun May 24, 2020 8:52 am

another great discussion by HGX this morning & you have to love SPC's hand drawn analysis

Area Forecast Discussion
National Weather Service Houston/Galveston TX
622 AM CDT Sun May 24 2020

.AVIATION [12Z TAF Issuance]...

Messy, messy forecast period ahead. Widespread MVFR CIGs with
isolated spots of IFR, as well as scattered SHRA and isolated TS
to start. Should see activity briefly come to an end later this
morning as we improve to VFR. TSRA to erupt this afternoon, fading
after sunset. MVFR CIGs return, as well as more potential for
rain later tonight. Specifics will be very hard to pin
down...multiple amendments seem virtually certain.

&&

.PREV DISCUSSION /Issued 356 AM CDT Sun May 24 2020/...

.DISCUSSION...

The much more pronounced appearance of streamer showers very
early this morning on radar shows we are finally transitioning
from last week`s persistent ridging and hot weather to a more
unsettled pattern. This new pattern will likely persist for a
while as well, bringing us several opportunities for periods of
showers and thunderstorms for much of the week.

We`ll continue to have to watch for the potential of heavy
rainfall creating flooding issues, as the large-scale environment
will remain supportive of efficient rain processes. Fortunately,
confidence is a little higher that rains today will not realize
high end potential, though the strongest storms will be able to
produce localized issues in spots with poor drainage with rain
rates of up to an inch per hour.

As the environment does not look to change significantly in the
coming days, we will have to evaluate mesoscale features day to
day to see if each day`s setup may be able to result in more
significant rainfall.


.SHORT TERM [Through Monday Night]...

The convective system from earlier on Saturday coming out of the
Rio Grande Valley has largely dissipated northwest of Corpus
Christi, well short of our area. Model guidance that produced real
significant rains in our area largely reinvigorated that line as
it moved into our area today, and now we have neither that line,
nor a strong outflow boundary from it that`s made it to our area.

Because of this, I`m more confident in the HREF trends to shave
off the really high end potential for rainfall today in Southeast
Texas. But, that`s not to say we`re getting off scot free by any
means. We`ve got much healthier nocturnal streamer showers setting
up well west of Houston in line with Matagorda Bay, indicating a
good channel of moisture up into the area. GOES-East`s TPW product
also shows a richer pool of moisture available. Combine this with
a shortwave trough rolling in from the Big Bend and a weaker cap
with easily achievable convective temps, and we should be pretty
good for scattered to numerous showers and storms as we see
daytime heating crank up the instability.

With CAPE over 1000 J/Kg pretty much a slam dunk, and even
exceeding 2000 J/Kg quite likely, storms that do get going should
pulse up in intensity easily, though I`d also expect them to
collapse without strong shear to promote storm organization. This
environment should allow for briefly heavy rain. Though backing
off the high end potential, HREF still shows a strong signal for
picking up an inch or two this afternoon on the coastal plain and
in the Houston metro. This should feel pretty familiar to
residents, with an intensity of rainfall that has been known to
cause spots of localized street flooding where the storms are
strongest.

In addition to the rainfall, forecast soundings show strong DCAPE
values for strong winds, though the temp/moisture structure is not
your textbook damaging winds structure, which may hamper bringing
the strongest winds to the surface. Similarly, there`s plenty of
CAPE, but with wet bulb zero heights fairly high, that probably
caps our hail potential somewhat as well. And, finally, though
shear and the vertical wind structure is pretty poor for
tornadoes, we are in the land of the super shower, and there`s
enough turning in the winds in the lowest kilometer that a brief
spinup is probably on the table, though the tornado threat is
clearly trailing far behind the other hazards.

Oh, and Monday? Wash, rinse, repeat. We`ll have to see what
happens with an organized cluster of storms expected to develop
over the RGV, moving eastward tonight. The mesoscale details of
how that cluster evolves will play very strongly into potential
for rain on Monday. Like 24 hours ago, there is a weak signal in
the guidance for excessive rain rates, and a stronger signal for
a scenario much like I described above. For what it`s worth, the
look in the guidance concerns me less for Monday than it did for
today at the same range. But, given the inherent unpredictability
of important factors, we`ll have to stay on guard. This will
become a theme going forward.


.LONG TERM [Tuesday Through Sunday]...

An upper level trough over the western plains will extend into west
and central Texas. A strong short wave rotating around the base of
the trough and strong moisture transport will provide the region
with a good chance of showers and thunderstorms. A well defined
upper level low develops in the base of the trough and gets cut-off
from the main flow and generally just sits and waffles back and
forth across the state through the end of the week. Global models
are in better agreement with the general placement of the upper low
but there are enough differences that to pinpoint who will get rain,
when it`ll occur and how much will fall is still a bit of a folly at
this time. Certainly rain chances are in order since SE TX will lie
on the east side of the low and upper level winds remain broadly
divergent. The EC is further east with the low on it`s 00z run and
this shunts more of the precip eastward on Wed/Thu. The GFS also
looks a bit further east before it takes the low back to the central
part of the state. Although fcst soundings show some drier air working
into the moisture profile, convective temps look reachable day with
Tc around 84-85 degrees with PW values hanging around 1.65-1.75
inches. Will carry chance to likely PoPs every day as diurnally
driven showers and thunderstorms should develop. Any embedded s/wv
rotating around the low will enhance rainfall but timing on that is
uncertain at this time. An upper level ridge is expected to develop
next Sunday or Monday and things should begin to dry out during the
the first week of June. 43


.MARINE...

Moderate onshore winds will persist, keeping elevated seas through
the holiday weekend. Caution flags for the Gulf, and at times the
bays will likely continue to be needed. Thunderstorm chances will
increase today as a series of shortwave troughs aloft passes
through. This more active pattern of showers and thunderstorms
will continue well into the upcoming week as an upper low looks to
be cutoff over the region and move little over the next several
days. However, towards mid-week, we may see much more variable
winds, which should break the persistent onshore fetch, and allow
for diminished, but more confused seas to emerge.


.CLIMATE...

Both Houston and Galveston set new high minimum temperature records
yesterday and this was second day in a row Galveston achieved a high
minimum record. The low yesterday at Galveston was only 81 degrees.
This was the warmest overnight low temperature for so early in the
year and also tied for the warmest overnight low temperature for the
month of May. 43

&&

.PRELIMINARY POINT TEMPS/POPS...

College Station (CLL) 88 70 82 69 82 / 60 70 80 60 60
Houston (IAH) 89 73 83 72 84 / 40 60 80 50 60
Galveston (GLS) 85 76 83 76 83 / 20 50 70 40 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 late tonight 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...43


https://twitter.com/NWSSPC/status/1264556433841860611
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Rip76
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Re: MAY 2020

Post by Rip76 » Sun May 24, 2020 9:00 am

Nice!

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DoctorMu
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Re: MAY 2020

Post by DoctorMu » Sun May 24, 2020 11:00 am

Daytime heating popping up those streamer showers. Really juicy air firing on all cylinders.

Image

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jasons2k
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Re: MAY 2020

Post by jasons2k » Sun May 24, 2020 12:02 pm

So far, lots of thunder on-and-off here but not a drop yet.

BlueJay
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Re: MAY 2020

Post by BlueJay » Sun May 24, 2020 12:56 pm

Full fledged storm going on in The Woodlands!

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Re: MAY 2020

Post by BlueJay » Sun May 24, 2020 1:10 pm

Storm has subsided, skies are still cloudy, sun is out, thunder is rumbling.
That was quick.

Waiting for the next round?

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DoctorMu
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Re: MAY 2020

Post by DoctorMu » Sun May 24, 2020 1:27 pm

jasons2k wrote:
Sun May 24, 2020 12:02 pm
So far, lots of thunder on-and-off here but not a drop yet.
Sorry about the famine. PUlling for a downpour.

Without the Aggies in town, the Aggiedome appears weak.

So, it looks like a mini-entraining feast. Got that backyard mow in just in time.

unome
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Re: MAY 2020

Post by unome » Sun May 24, 2020 1:37 pm


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