September 2019 - Warm End of September

General Weather Discussions and Analysis
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don
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Flood Watch
National Weather Service Houston/Galveston TX
414 AM CDT Tue Sep 17 2019

...FLASH FLOOD WATCH IN EFFECT FROM 1 PM CDT THIS AFTERNOON
THROUGH WEDNESDAY AFTERNOON...

The National Weather Service in Houston/Galveston has issued a

* Flash Flood Watch for a portion of southeast Texas...including
the following counties...Brazoria Islands...Chambers...Coastal
Brazoria...Coastal Galveston...Coastal Harris...Coastal
Matagorda...Fort Bend...Galveston Island and Bolivar
Peninsula...Inland Brazoria...Inland Galveston...Inland
Harris...Inland Matagorda...Matagorda Islands...Northern
Liberty...Southern Liberty and Wharton.

* From 1 PM CDT this afternoon through Wednesday afternoon

* A weak coastal trough coupled with an upper level low and deep
tropical moisture will will produce periods of showers and
thunderstorms today. Some of the rain will be locally heavy
especially along and south of a Wharton to Houston to Cleveland
line. Widespread rainfall by Wednesday morning will average
between 1 and 3 inches with isolated totals between 4 and 6
inches possible in areas where training of storms develop.

* The Flash Flood Watch will probably need to be extended through
Wednesday night over parts of Southeast Texas and may also need
to be expanded further north.

* Do not drive your vehicle into areas where the water covers the
roadway. The water depth may be too great to allow your car to
cross safely. Vehicles caught in rising water should be
abandoned quickly. If your vehicle stalls...abandon it and seek
higher ground immediately. Rapidly rising water may engulf your
vehicle and its occupants and sweep them away. Move to higher
ground.
unome
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I don't remember the last time we were forecast to stay below 90 for a full 5 days
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djmike
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lOOking at radar this morning, we are about to get pummeled here in Beaumont with a pretty hefty band. Already had a good band about 30 min ago. 80-90% chance for the next 3 days for Beaumont and I believe Hou too who is already in a FFWat. FFWat possible for Jefferson county later today. Possible flooding begins today. Stay safe everyone. Turn around dont drown!
Mike
Beaumont, TX
(IH-10 & College Street)
unome
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from https://www.wpc.ncep.noaa.gov/metwatch/metwatch_mpd.php
Mesoscale Precipitation Discussion 0858
NWS Weather Prediction Center College Park MD
557 AM EDT Tue Sep 17 2019

Areas affected...Southeast TX & Southwest LA

Concerning...Heavy rainfall...Flash flooding possible

Valid 170957Z - 171557Z

Summary...A northward-moving tropical disturbance is expected to
bring heavy rains into southeast TX and southwest LA this morning.
Hourly rain totals to 3" with local amounts to 6" are possible.

Discussion...A tropical disturbance with a surface low offshore
the Middle TX coast has led to an increase of shower and
thunderstorm activity with cooling cloud tops over the northwest
Gulf of Mexico during the past few hours, with some of the
activity beginning to move inland across southeast TX. Radar
indicates hourly rain totals of 0.5-1" onshore as of late with
occasional 2" an hour totals well offshore. Precipitable water
values of 2.0-2.4" exist per recent GPS data. Inflow at 850 hPa
is southeast, up to 25 kts, northeast of Matagorda Bay, which
along with a similar magnitude of effective bulk shear appears to
be leading to some degree of organization on recent satellite and
radar imagery. ML CAPE values of 1000-2500 J/kg exist across the
region, with the highest values near and just offshore. Winds up
through 500 hPa are unidirectional and cyclonic with height.

The expectation is for curved rain bands to develop over the next
few hours which could yield hourly rain totals to 3" within this
environment where they train, with some gradual outward expansion
of the banding expected through the morning. The system as a
whole should move/propagate northward around a low- to mid-level
high pressure system over the central Gulf of Mexico. Rain moving
ashore should cause the instability gradient to retreat back
towards the coast, making it an effective front/convergence zone.
The mesoscale guidance shows reasonable consistency, with a strong
signal for local amounts of 5-6". Parts of these region are dry
or have descended into drought, so flash flood guidance values are
quite high and soils are generally desiccated. However, the high
rain rates possible in this moist and unstable air mass would
quickly saturate soils and cause significant problems in urban
environments. Since the signal in the guidance is localized and
the rain is just beginning to fall, chose the possible category.

Roth

ATTN...WFO...HGX...LCH...

ATTN...RFC...LMRFC...WGRFC...
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srainhoutx
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Tuesday morning weather briefing from Jeff:

Heavy rainfall event and flash flood threat this evening through Thursday for SE TX.

Flash Flood Watch will go into effect at 100pm today along and SE of a line from Wharton to Houston to Cleveland

Mid level low pressure system clearly noted in radar data from Houston and Corpus Christi continues to spin over the NW Gulf of Mexico about 150 miles south of Palacios. Numerous rainbands have formed in the last few hours across the NW Gulf of Mexico from Galveston Bay to over 200 miles off the upper TX coast and are rotating inland as far as Downtown Houston this morning. Brief heavy rainfall is likely with these bands this morning. Overall expect an increase in the frequency of these bands today and some potential for cell training in the Flash Flood Watch area which could produce a quick 1-2 inches of rainfall through this afternoon.

Mid level low pressure system and weak surface low/trough will begin to slowly lift northward into SE TX tonight through Wednesday night with numerous showers and thunderstorms expected. Best estimate track for this feature is inland over Matagorda/Brazoria Counties and then slowly NNE into Fort Bend and Harris Counties Wednesday and NNE toward Montgomery and San Jacinto Counties on Thursday. Global guidance has shifted ever so slightly eastward overnight with the track of this feature. Heavy rainfall both near the core or center of the low pressure area and within bands on the eastern and southern flank of the system will be likely. This becomes especially true late tonight into Wednesday as the 850mb moisture transport increases along with good low level inflow off the Gulf of Mexico. Moisture values will be extremely high during the period with PWS ranging from 2.35-2.65 inches which will support intense rainfall rates in any deep and sustained convective developments.

Rainfall Amounts:
Widespread rainfall amounts of 5-7 inches are expected over much of the area with isolated totals of 10-12 inches. Deep tropical moisture in place will support excessive hourly rainfall rates in deeper convection with rates of 1-3 inches possible. While grounds are dry, rainfall today will start to result in gradual saturation of the soil conditions and as rainfall totals increase over the next 24-36 hours run-off will also increase. Flash flooding will be possible under any areas of sustained training or cell clustering. Some of the higher resolution guidance is showing some indications of banding and potential for cell training late tonight into much of Wednesday over the region.

Hydro:
While watersheds are currently running below base flow, expected rainfall amounts will almost certainly lead to significant run-off once grounds become saturated. Rises on creeks and bayous to bankfull or above will be possible leading to more significant flooding. High short duration rainfall rates will lead to street flooding at times. Think most of Harris County can currently handle 5-6 inches of rainfall before significant bayou and creeks flooding would be a concern. However this greatly depends on the intensity of the rainfall rates and any breaks between the intense rainfall cells. Given the complexities in where any sort of training bands may become established yields little confidence on where any higher totals and larger flood threat would be.

WPC has placed portions of SE TX in a moderate risk for flash flooding today, Wednesday, and Thursday.

5-Day Forecasted Rainfall Totals:
09172019 Jeff 1 untitled.png
Today:
09172019 Jeff 2 untitled.png

Wednesday:
09172019 Jeff 3 untitled.png
Thursday:
09172019 Jeff 4 untitled.png



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srainhoutx
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NWS Houston‏Verified account @NWSHouston · 3m3 minutes ago

Thread: A system in the western Gulf will bring showers and thunderstorms over the region today through Thursday. Today's main areas of concern are mainly along the coastal counties as the storms make their way on shore. #TXwx #HOUwx #GLSwx #BCSwx

Attachments
09172019 HGX AM 1 EEqWTyoUwAIInnG.jpg
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unome
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CSU's RAMMB/CIRA Slider added MRMS products - really nice

----------MRMS PRODUCTS----------
MRMS Merged Base Reflectivity QC
MRMS Reflectivity At Lowest Altitude
MRMS Radar Precipitation Accumulation 1-hour
MRMS Lightning Probability 0-30 minutes - NLDN
MRMS CG Lightning Density 5-min - NLDN
MRMS Surface Precipitation Type/Flag
MRMS Radar Precipitation Rate
Pas_Bon
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Coming down in buckets here in League City/Kemah...thanks for the rain!
No thanks for the rain all at once! Lol
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djmike
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WOw. Heavy heavy band in beaumont. Over 2” in 30 min. Finally made it to work. Many roads are flooded already and coming down too fast for txdot to close these roads fast enough. Drive slow. College and MLK area is rhe area i drove. 2 underpasses filled up fast. Turn around dont drown.
Mike
Beaumont, TX
(IH-10 & College Street)
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snowman65
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djmike wrote: Tue Sep 17, 2019 7:25 am WOw. Heavy heavy band in beaumont. Over 2” in 30 min. Finally made it to work. Many roads are flooded already and coming down too fast for txdot to close these roads fast enough. Drive slow. College and MLK area is rhe area i drove. 2 underpasses filled up fast. Turn around dont drown.
Those overpasses can fill up quick. I havent noticed any heavy downpours yet downtown but I'm sure it's a hit and miss thing right now.
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djmike
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snowman65 wrote: Tue Sep 17, 2019 7:30 am
djmike wrote: Tue Sep 17, 2019 7:25 am WOw. Heavy heavy band in beaumont. Over 2” in 30 min. Finally made it to work. Many roads are flooded already and coming down too fast for txdot to close these roads fast enough. Drive slow. College and MLK area is rhe area i drove. 2 underpasses filled up fast. Turn around dont drown.
Those overpasses can fill up quick. I havent noticed any heavy downpours yet downtown but I'm sure it's a hit and miss thing right now.
Yeah its a band from PA towards Beaumont, but the entire band is still lifting N as it rotates. Just looked at radar again and it looks like we are in for another hefty training band in a few. You in Orange should be getting in on the action probably within the next 30min as it rotates northward.
Mike
Beaumont, TX
(IH-10 & College Street)
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djmike
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D9C9B0CD-D8BE-4111-B8CF-7C3EE4C8F34C.jpeg
Not good for Beaumont.. large training band setting up. Already over 2” this morning with flooding. Be safe everyone.
Mike
Beaumont, TX
(IH-10 & College Street)
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don
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Rain is coming down really heavy here near downtown.
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srainhoutx
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Surface low offshore S of Bay City looks to be attempting to tighten up a bit as it slowly drifts N
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Rip76
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srainhoutx wrote: Tue Sep 17, 2019 8:58 am Surface low offshore S of Bay City looks to be attempting to tighten up a bit as it slowly drifts N
Yep, seeing that too.
stormlover
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This is a depression don't understand why NHC won't pull the trigger!!!! Bastardi is going off right now on twitter about it.
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djmike
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Looks like the Low is further North and east than yesterdays projection. LOoks just south of hou when it was sw of houston yesterday
Mike
Beaumont, TX
(IH-10 & College Street)
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djmike
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Pretty gusty winds with these bands in bmt
Mike
Beaumont, TX
(IH-10 & College Street)
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tireman4
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My Moderator's PSA for this upcoming event ( well, I suppose ongoing). Our pro and amateur mets will be here, on and off all day ( and week). This will be an ever changing situation. Remember, they are forecasting and doing met stuff, so be patient with them if you have questions.
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