OCTOBER 2018 - Stormy Halloween

[DoctorMu]

The "real" cold air (low 40's 30's) doesn't usually start until the middle to end of November.

Like December 9th! haha


Last year we went from a DP of 70° to 4 inches of snow in less than 48 hours!

[don]

We really need to be weather aware tomorrow, the HRRR shows what looks to be discrete supercells tomorrow afternoon ahead of the main line of storms.

[Cpv17]

We really need to be weather aware tomorrow, the HRRR shows what looks to be discrete supercells tomorrow afternoon ahead of the main line of storms.

Those are the ones you have to watch out for rotation on the southwestern flank of the storm. Hopefully we won’t see any hooks forming.

[Katdaddy]

An active Halloween weather day and night is on the way. The SPC has most of SE TX and LA under an enhanced risk for severe thunderstorms this afternoon through tonight. Strong to severe storms are possible this afternoon ahead of the cold front and then along the cold front this evening and tonight. Remain weather aware today and tonight.

[Cromagnum]

We really need to be weather aware tomorrow, the HRRR shows what looks to be discrete supercells tomorrow afternoon ahead of the main line of storms.

Great. Just in time for my flight home from Kentucky.

[unome]

our current forecast gives 100% chance of severe thunderstorms this evening, don't see that often, thankfully

1st Mesoscale Discussion of the day for TX: https://www.spc.noaa.gov/products/md/

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Mesoscale Discussion 1599
   NWS Storm Prediction Center Norman OK
   0720 AM CDT Wed Oct 31 2018

   Areas affected...Portions of western into central TX

   Concerning...Severe potential...Watch possible 

   Valid 311220Z - 311445Z

   Probability of Watch Issuance...40 percent

   SUMMARY...Isolated hail will be possible as storms continue to
   develop and increase in coverage from west to east across western
   into central Texas this morning.  While watch issuance is not
   warranted for these elevated storms, areas downstream across central
   Texas will be monitored for potential watch issuance later this
   morning or early afternoon.

   DISCUSSION...Deep forcing for ascent is evident and emerging from NM
   into west TX this morning, given the presence of ongoing nocturnal
   thunderstorms continuing to develop and spread eastward ahead of a
   progressive shortwave trough.  The combination of this ascent and
   cooling 500-mb temperatures/steepening midlevel lapse rates
   spreading east atop low-level warm advection/moistening, given
   southerly low-level winds, suggests storms will continue to form
   east this morning across western into central TX.

   The western extent of a cold front has moved very little the last
   several hours, and at 12Z extended from near KDAL to between KMWL
   and KACT to just south of KSJT and KFST, and west-northwest to KGDP.
   Short-term trends and guidance suggest most of the storms this
   morning should remain elevated north of this front, where forcing
   for ascent will be maximized within the nose of the southerly
   low-level jet.  The presence of steepening midlevel lapse rates,
   effective bulk shear around 40 kt and MUCAPE of 1000-1500 J/kg
   should support a few strong to severe storms with isolated large
   hail being the primary severe threat this morning. 

   Meanwhile, objective analyses indicated the likelihood for
   convection that forms near the cold front from north of KACT into
   Hamilton to San Saba Counties would be surface based, given the lack
   of inhibition, currently.  Given stronger forcing for ascent with
   the southwest trough and a transient northeastward-moving impulse
   from Mexico is expected to arrive across central TX later this
   morning or early afternoon, in concert with stronger
   destabilization, a watch issuance is not warranted in the short
   term.  However, convective trends will be monitored for an increase
   in storm development/intensities that would result in watch
   issuance.

   ..Peters/Edwards.. 10/31/2018

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...FWD...EWX...SJT...LUB...MAF...

[srainhoutx]

Wednesday morning briefing from Jeff:

Severe thunderstorms with damaging winds, large hail, and tornadoes possible this afternoon and overnight. A couple of strong tornadoes (EF2+) will be possible this afternoon and evening.

Have a way to get weather warning today and tonight.

Radar already shows showers and thunderstorms developing from Matagorda Bay NNE toward Columbus this morning and moving NNE. This activity is developing along returning moist axis of low level jet and forcing approaching with a short wave from the SSW. Expect this activity to progress across the area this morning with a quick round of showers and thunderstorms. Will get a brief break post morning activity while the air mass begins to heat and destabilize and as surface temperatures warm into the mid 80’s expect the warm sector air mass to become unstable with CAPE values of 1500-2500 J/kg. Low level wind shear will be increasing today and as capping is removed by early to mid afternoon the potential for discrete cells to form in the warm sector is becoming more likely. These cells could pose a higher tornado threat and latest high resolution models are suggesting that a cluster of supercells will develop over the region early to mid afternoon and move NNE across the central and NE parts of the area.

Could see another brief break in the activity early this evening, before the onset of the main line of severe weather with the actual cold front. Linear forcing along the cold front will result in a developing line of thunderstorms from around 700-900pm in the College Station area to 800-1100pm in the Houston area and then 1000-100am along the coast. Severe weather parameters remain likely during this period with favorable low level shear and instability in place. Expect the linear forcing to result in a squall line over the area with damaging winds and hail, but cannot rule out isolated tornadoes along the leading edge of the line, or in any cells that develop ahead of the main line. High resolution models continue to indicate the potential for convergent low level plumes in the low level jet that may develop corridors of supercells this evening. Any discrete cells this evening could pose a strong tornado threat as low level wind fields increase ahead of the approaching upper level trough.

Rainfall:
Widespread rainfall amounts of 1-2 inches are likely with isolated totals of 3-5 inches under any sustained training bands. Air mass is fairly moist and nearly saturated by this evening, and convection will be fully capable of utilizing the moist environment and producing very heavy rainfall. Quick rainfall totals of 1-3 inches in less than an hour will be possible and lead to rapid street flooding. High resolution models also show some training of cells in the convergent bands especially across our eastern and NE counties this afternoon into the evening hours. Potential is certainly there under any training bands for 4-5 inches of rainfall in a few hours.

Strong cold front will sweep off the coast early Thursday and usher in a much colder air mass and clear skies with temperatures falling into the 40’s on Friday morning and highs in the 60’s on Thursday and Friday. A powerful early November storm system will approach TX from the NW Sunday into Monday and will need to bring rain chances back into the forecast on Sunday into Monday.

Severe Weather Outlook (Today):

[unome]

updated SPC Day 1 (looks much like previous) https://www.spc.noaa.gov/products/outlook/day1otlk.html

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Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0815 AM CDT Wed Oct 31 2018

   Valid 311300Z - 011200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM
   EAST-CENTRAL AND SOUTHEAST TEXAS TO SOUTHWESTERN MISSISSIPPI...

   ...SUMMARY...
   The greatest risk for severe thunderstorms, capable of producing
   damaging winds, hail, and a few tornadoes, exists from southeast
   Texas to the lower Mississippi Valley today through tonight.

   ...Synopsis...
   In mid/upper levels, a series of shortwave perturbations now located
   from northwestern BC to the Four Corners states will shape the
   eastward shift of synoptic troughing across the central CONUS today
   and tomorrow.  A strong, basal shortwave trough -- now evident in
   moisture-channel imagery from southwestern CO across eastern AZ --
   is forecast to move east-southeastward by 00Z to southeastern CO,
   south-central NM and northern Chihuahua.  By 12Z, this trough should
   pivot eastward and become less positively tilted, reaching
   west-central KS, northwest TX and northern Coahuila.  An initially
   separate, weaker, southern-stream perturbation -- currently crossing
   central Baja and adjoining Gulf of California -- will eject
   east-northeastward across northern MX today, its northeastern
   fringes reaching south-central TX this evening, before further
   deformation and weakening of its vorticity field occurs. 

   Surface analysis showed a cold front from eastern MO across western
   AR and north-central TX, becoming a wavy/quasistationary boundary
   over parts of the northern Hill Country and Edwards Plateau regions
   to the lower Pecos Valley.  As heights fall aloft with the approach
   of the strong southwestern CONUS trough, a weak frontal-wave low
   should develop over east-central TX mid-late this afternoon, with
   cold front southwestward across south-central TX into northern
   Coahuila.  The low should move northeastward over the Arklatex
   region this evening, across AR into the MO Bootheel/extreme western
   KY region by the end of the period.  By that time, the front should
   reach southeastern AR, south-central/southwestern LA and the shelf
   waters off the mid/upper TX coast. 

   ...TX to lower Mississippi Valley...
   Near the leading edge of the large-scale ascent plume preceding the
   mid/upper trough, a plume of convection is gradually strengthening 
   over west-central TX between ABI-MAF.  This activity may offer
   severe hail over the next few hours, and the potential for damaging
   wind will increase with proximity of its southern portions to the
   front and adjoining warm sector.  See SPC mesoscale discussion 1599
   for more details. 

   With persistence and eastward shift of the associated
   mid/upper-level vertical-motion plume, and as the surface frontal
   zone impinges on a diurnally destabilizing warm sector, the morning
   convection should persist eastward, expand, and intensify through
   the day.  With flow aloft largely parallel to the frontal zone,
   expect evolution into a broken to solid, quasi-linear configuration
   with embedded bow, LEWP and supercell features.  Additional
   thunderstorms are forecast to develop and grow with time from midday
   through afternoon over the weakly capped warm sector in east and
   southeast TX, along low-level convergence/confluence axes.  Both
   processes will occur amidst strengthening mid/upper winds and
   continued boundary-layer warming and moisture transport.

   Accordingly, a gradual ramp-up in severe potential is expected,
   amidst buoyancy/shear parameter spaces favoring the entire spectrum
   of severe hazards.  Where low- and middle-level lapse rates will be
   greatest, overlapping with the western rim of richest low-level
   moisture, a narrow plume of 2000-3000 J/kg prefrontal MLCAPE should
   develop this afternoon over central/south-central TX, decreasing
   gradually eastward and sharply along and behind the front.  MLCAPE
   500-1000 J/kg should prevail tonight over the LA/MS portion of the
   outlook area, weaker but still with sufficiently unstable
   surface-based parcels to support the outlined severe threat.  

   Though winds aloft won't be quite as strong across southeast TX and
   LA this afternoon/evening as farther north/west, more-backed surface
   winds should help to enlarge both hodographs and the storm-relative
   surface vector.  Effective SRH in the 150-300 J/kg range should
   become common, increasing this evening into overnight over LA and
   central/western MS near a 50-60-kt low-level jet.  This will boost
   the tornado risk for any relatively sustained/discrete supercells,
   and even for line-embedded storms.  Such an environment supports the
   somewhat conditional potential for strong tornadoes, with storm mode
   being a major influence on their number and longevity.

   A separate round of thunderstorms may develop late this afternoon
   and this evening over parts of southwest TX near the Rio Grande and
   lower Pecos River regions, and over the Serranias del Burro range of
   Coahuila.  Severe hail/gusts will be possible from this activity as
   it tracks eastward across parts of southeast and south-central TX,
   with wind more probable along and south of the front in
   more-unstable boundary-layer air.

   ..Edwards/Peters.. 10/31/2018

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
   CURRENT UTC TIME: 1340Z (8:40AM), RELOAD THIS PAGE TO UPDATE THE TIME

[tireman4]

HGX Forecast

[GBinGrimes]

This will be one of those days where the board will easily flip 15 - 20 pages with updates and alerts.

Praying for safety for all.

[tireman4]

HGX Forecast Halloween

[DoctorMu]

HGX Forecast Halloween

Really bad timing on Halloween night because a lot of people will be out and about. Let's be weather aware today and tonight!

[Katdaddy]

Special Weather Statement
National Weather Service Houston/Galveston TX
902 AM CDT WED OCT 31 2018

TXZ236-237-336-337-436-311430-
Inland Brazoria TX-Coastal Matagorda TX-Inland Matagorda TX-
Matagorda Islands TX-Coastal Brazoria TX-
902 AM CDT WED OCT 31 2018

...SPECIAL WEATHER STATEMENT...

At 901 AM CDT, Doppler radar was tracking a strong thunderstorm near
South Texas Nuclear Plant, moving northeast at 25 mph.

Winds in excess of 30 mph will be possible with this storm.

Locations impacted include...
Matagorda, Bay City, South Texas Nuclear Plant, Van Vleck and
Wadsworth.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

[DoctorMu]

Lift and deep layer of shear predicted, harbingers of severe weather.

It looks nasty already.

Let's be careful out there.

[sau27]

I have to think the strength of the storms to the southwest of town right now may actually cut down the severe/discrete supercell potential for mid day. These storms look like they may be able to work over the atmosphere enough to delay the show until the front gets closer this evening. We shall see.

[don]

I think that these may actually be the midday storms the models were showing yesterday as we have a disturbance passing through now, they may just be early...

[tireman4]

I agree Don..here they come..

[unome]

https://twitter.com/iembot_hgx

Code: Select all

Area Forecast Discussion
National Weather Service Houston/Galveston TX
1018 AM CDT Wed Oct 31 2018

.UPDATE...
Radar imagery shows showers and thunderstorms mostly west of I-45
this morning, with the best convection currently located over 
Matagorda moving into Brazoria and Fort Bend counties. Winds 
associated with these storms have been hovering around 30-35 mph,
with the storm motion to the northeast near 25 mph. IR imagery 
shows cloud tops continuing to cool to near -67 dec C, as the 
storms tap into some mid to upper level instability. 

The 12Z upper level sounding out of College Station shows a 
small, breakable cap at 950 mb. With daytime heating, this cap
should erode by the early afternoon hours. Most of the short term
guidance continues to develop showers and thunderstorm this 
afternoon out ahead of the cold front. These storms could become 
severe with strong winds, hail and an isolated tornado possible. 
Have gone ahead and raised PoPs to account for current radar 
imagery and trends in the short term guidance. Considering this 
morning's model guidance, the timing of the cold front at this 
time appears to be about the same. Expecting storms to reach our 
northern tier of counties from Caldwell to Crockett late this 
afternoon into early this evening, moving into the Houston metro 
and along I-10 during the evening hours, and reaching the coast 
around midnight. Much of SE TX remains in an enhanced risk for 
severe storms today and through the evening hours, issued by SPC.

Additionally, localized heavy rainfall will be possible with this
precipitation. The HRRR appeared bullish with precip totals in 
the first few runs this morning, but has backed off with its 
extremes. At this time widespread amounts of 1-2 inches will be 
possible with isolated higher totals of 4-6 inches. Also worth 
mentioning, trends in the recent runs of both the HRRR and RAP13 
have also focused these higher amounts over the coastal counties 
such as Brazoria and Galveston. Though the severe threat remains 
the primary risk this afternoon and into the evening, we will also
need to monitor the potential for localized heavy rainfall especially
over our already fairly saturated soils.

Hathaway

&&

.PREV DISCUSSION... /ISSUED 525 AM CDT Wed Oct 31 2018/ 

DISCUSSION...
Bands of light rain developing over the coastal waters are moving
up into southern portions of the CWA this morning. To the west... 
a skinny line of showers are developing along the prefrontal trof
(and likely aided by a shortwave aloft). The activity moving from
the Gulf appears to associated with a stray upper low tracking up
the coast from BRO. All of this looks to be setting the stage for
a rather active day/evening...and probably to much dismay for all
the ghouls getting ready to haunt the streets tonight. 

Short-range models are indicating the development of scattered TS
this afternoon for SE TX...out ahead of the main front. Depending
on how much heating we get, there may be enough instability/shear
to support strong to marginally severe storms later this morning/
early afternoon (with the aforementioned upper low). However, the
main threat of severe weather will be late this afternoon (start-
ing up north) through the evening hours (further to the south) as
the cold front moves into the region. Very favorable jet dynamics
aloft along with the progged deep-layer shear/lift from the front
itself should be supportive for severe weather for much of SE TX.
Primary threats will be damaging winds, hail and possible tornado
development. See SPC Day 1 Outlook for more details. 

Also of note for the event will be the possibility of brief/local-
ly heavy rainfall with the line of storms. While they will be mov-
ing at a decent rate (and not training), rainfall totals could av-
erage from 1 to 2 inches with isolated amounts from 4 to 6 inches.
This should be enough to produce some urban/small stream flooding.

All of this activity will be moving E/SE out of the area into the
coastal waters by early Thur morning (09-12Z). A cooler/drier air
mass should settle across the CWFA for Thur/Fri as the upper trof
axis shifts east. However, the ensuing NW upper flow is then exp-
ected to push a strong upper low/shortwave down into the state by
Sun. Elevated POPs to return for Sun/Mon. 41

MARINE...
South winds 10-20 knots bays and 15 to 25 knots over the Gulf waters 
with building seas. S/W moving up from the southwest will likely 
bring scattered showers and even a few thunderstorms this morning. 
Waterspout threat this morning with the stronger storms. Have issued 
an SCA for late afternoon over the 20-60nm waters then expanding 
into the nearshore waters this evening. Strong to severe 
thunderstorms with primary threat of severe from winds in excess of 
40 knots tonight. A cold front pushes off the coast overnight into 
early Thursday morning. Winds become northwest in the wake of the 
frontal boundary and steep waves/chaotic seas should form and could 
see some isolated 9-10 foot seas. SCA will need extending. The 
offshore flow persists well into Friday morning. Weak high pressure 
slides out into the Gulf early Saturday morning varying winds back 
to the southwest. Light to moderate south winds Saturday afternoon 
through Sunday evening. Another cold front slides through Monday 
morning. 
45 

AVIATION...
Patchy MVFR ceilings this morning beneath the expanding cirrus 
shield. S/W producing a few showers beneath the cap around 800mb. 
Cap should strengthen somewhat this morning with steepening lapse 
rates above. May need to add VCSH this morning in upcoming package. 
Cold front through FTW and nearing SJT and will continue to push 
southward today and should reach the CLL area around 21z with a few 
hours of showers and thunderstorms...gusty winds likely with these 
storms. Band of storms coalescing as it comes with more linear wind 
profile over IAH/HOU area 00-04z. If storms get more organized late 
this morning or more likely this afternoon ahead of the frontal 
boundary could see impacts at IAH/HOU hubs...latest HRRR has been 
pinging moreso on this likelihood. Northwest gusty winds in the wake 
of the frontal storms tonight. 
45

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL)      80  53  66  46  71 /  90  80  20   0   0 
Houston (IAH)              82  59  67  50  71 /  80 100  30   0   0 
Galveston (GLS)            80  64  69  57  69 /  70 100  60   0   0 

&&

.HGX WATCHES/WARNINGS/ADVISORIES...
TX...NONE.
GM...SMALL CRAFT SHOULD EXERCISE CAUTION until 7 PM CDT 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...Galveston Bay...
     Matagorda Bay.

     Small Craft Advisory from 7 PM this evening to 7 AM CDT Thursday 
     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.

     Small Craft Advisory from 4 PM this afternoon to 7 AM CDT 
     Thursday for the following zones: 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.

     SMALL CRAFT SHOULD EXERCISE CAUTION until 4 PM CDT this 
     afternoon for the following zones: 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.

&&

$$

Update...08

[Cromagnum]

Of course. Flight into Houston cancelled, so now I get to waste all day at the airport. What a bunch of pansy asses.

[don]

Starting to see peaks of sun here in the Heights..., we'll have to watch to see if the atmosphere destabilizes this afternoon, as more decreet storms could develop this afternoon before the squall line later tonight as the front moves closer if the atmosphere destabilizes again.