SEPTEMBER 2018 - Very Wet Month Wrap Up

[Andrew]

If the wave can slow down enough like the ECMWF is showing and allow the TUTT over the gulf to eject and shear to the northeast it could have a small period for slight development. Otherwise expect just increased rain chances for later this week.

[unome]

The 12Z ECMWF suggests a weak surface low attempts to organize just off the Middle Texas Coast next Friday morning

I was just browsing the NDBC for a cam by the Yucatan/Cuba, but that one is no longer shown on the map: https://www.ndbc.noaa.gov/buoycams.shtml

However, we do now have 3 buoycams along the TX coast, near the following ports

• Corpus Christie
  station page: https://www.ndbc.noaa.gov/station_page. ... tion=42020
  updating image link: https://www.ndbc.noaa.gov/buoycam.php?station=42020
  
  Freeport
  station page: https://www.ndbc.noaa.gov/station_page. ... tion=42019
  updating image link: https://www.ndbc.noaa.gov/buoycam.php?station=42019
  
  Galveston
  station page: https://www.ndbc.noaa.gov/station_page. ... tion=42035
  updating image link: https://www.ndbc.noaa.gov/buoycam.php?station=42035

[srainhoutx]

No real changes from the WPC afternoon Updated 7 Day QPF Chart. Rainfall is likely, some possible very heavy over the next 7 Days. But nothing near the magnitude of what our neighbors in the Carolinas and the Mid Atlantic States could see.

[srainhoutx]

We will need to monitor NE Mexico/S Texas surface obs and satellite data suggest another MCV and surface low are beginning to develop. That feature will likely be the next heavy rainfall maker overnight into Monday for our Region. Keep an eye on radar to our SW for further development during the evening hours.

[srainhoutx]

Regarding the NW Caribbean disturbance, the ECMWF EPS are getting a bit more bullish with its TC Genesis probabilities later this week. Just something to monitor for now, but check back throughout the coming work week for any changes/updates.

[txsnowmaker]

Just now on The Weather Channel regarding Houston: "tomorrow could be a significant day in terms of heavy rain and flooding," then after talking about the potential Gulf disturbance again adding that "Tommorow could be a very bad day in terms of flooding there." (Houston)

[sambucol]

Just now on The Weather Channel regarding Houston: "tomorrow could be a significant day in terms of heavy rain and flooding," then after talking about the potential Gulf disturbance again adding that "Tommorow could be a very bad day in terms of flooding there." (Houston)

Been out of pocket. What is supposed to happen tomorrow formour area???

[DoctorMu]

Area Forecast Discussion
National Weather Service Houston/Galveston TX
407 PM CDT Sun Sep 9 2018

.DISCUSSION...
Clustering showers and thunderstorms now moving out of Houston
and weakening across Liberty County. New development is forming
across coastal Matagorda County at this hour. A weak surface
boundary draped across the coast with a inverted surface trough
over the nearshore waters will likely be the impetus to continued
unsettled weather through the early Monday morning hours. Satellite
showing what appears to be the early formation of a south central
Texas MCV with recent surface observations over the Rio Grande
Valley depicting confluence about a surface low in north(east)ern
Mexico. A jet max coming out off the Desert Southwest and digging
into western Texas should sharper the mid to upper tough enough
to promote more upper diffulence across eastern Texas through
tomorrow. Couple high moisture (gt 2.0 inch pwats) and the lower
level convergence provided by either/both coastal troughing or the
northeastward movement of a weak MCV off off to the southwest
will promote the regeneration of precipitation. Analysis of the
flash flooding threat is Marginal. Reasoning is that many
counties can take a quick 1 to 2 inches, maybe up to 3 to 4 inches
per hour rates, before there are problems. Also, there will be
periods of rain-cooled, stabilized air left in the wake of the
stronger clusters (as evidenced now) that will allow any water to
permeate or simply runoff. Third, storm motion may be faster than
previously thought so that any efficient rain-producing storm
moving at 20 to 25 mph may put down some decent gusts (to 35
knots) but not the rainfall needed to cause any significant
flooding problems. Another factor may be where overnight
convection decides to set up. Confidence is moderate that there
will be highly efficient rain-producing storm cells through
Tuesday but the question of whether they will form and stay
offshore or development across the southern third of the CWA still
remains very nebulous.

The mid week period seems to settle down a touch, either from a
worked over atmosphere from Monday and Tuesday`s rainfall or from
the gradual eastward advancement of the best upper lift and/or
shear out of the near coastal low level trough. Late week rain
chances will again be up`ed by the approach of a tropical wave
that is currently blowing up convection off the Yucatan Peninsula.
Its northern travels into a highly sheared environment over the
southern Gulf may do enough damage to not make this an item of
discussion by Wednesday. But, there is a slight chance that the
remnants of this wave could meander over toward us and provide an
extra boost of moisture-rich air to once again regenerate periods
of showers and thunderstorms Thursday and Friday. This forecast
assumes all of the above and keeps (many daytime) POPs high through
next weekend. A break from these return rounds of rain and thunder
looks to happen sometime over next weekend.

The temperature forecast is for below normal daytime temperature
readings per the rain and overcast and slightly above normal minimum
temperatures through 5 days. By this time next week, we can expect
afternoons to once again be back up to around 90F with maybe (very)
slightly cooler overnight minimums in the average lower to middle
70s.

&&

.PRELIMINARY POINT TEMPS/POPS...
College Station (CLL) 71 83 71 86 72 / 70 90 50 60 40
Houston (IAH) 74 83 73 84 73 / 70 90 60 80 50
Galveston (GLS) 78 83 77 83 78 / 70 90 70 80 60

[srainhoutx]

TROPICAL WEATHER OUTLOOK
NWS NATIONAL HURRICANE CENTER MIAMI FL
800 PM EDT SUN SEP 9 2018

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO:

THE NATIONAL HURRICANE CENTER IS ISSUING ADVISORIES ON HURRICANE
FLORENCE, LOCATED OVER THE WEST-CENTRAL ATLANTIC OCEAN, ON RECENTLY
UPGRADED HURRICANE HELENE, LOCATED SOUTHWEST OF THE CABO VERDE
ISLANDS, AND ON TROPICAL STORM ISAAC, LOCATED OVER THE CENTRAL
TROPICAL ATLANTIC.

THE COMBINATION OF AN UPPER-LEVEL TROUGH AND A TROPICAL WAVE OVER
THE NORTHWESTERN CARIBBEAN SEA IS PRODUCING A LARGE AREA OF
DISORGANIZED SHOWERS AND THUNDERSTORMS BETWEEN CUBA AND HONDURAS.
THE DISTURBANCE IS FORECAST TO MOVE SLOWLY WEST-NORTHWESTWARD TO
NORTHWESTWARD ACROSS THE NORTHWESTERN CARIBBEAN SEA AND THE
YUCATAN PENINSULA DURING THE NEXT COUPLE OF DAYS, WITH LITTLE OR NO
DEVELOPMENT EXPECTED DUE TO UNFAVORABLE UPPER-LEVEL WINDS AND LAND
INTERACTION. HOWEVER, UPPER-LEVEL WINDS ARE FORECAST TO BECOME A
LITTLE MORE CONDUCIVE FOR DEVELOPMENT WHEN THE SYSTEM MOVES ACROSS
THE WESTERN GULF OF MEXICO WEDNESDAY THROUGH FRIDAY.
* FORMATION CHANCE THROUGH 48 HOURS...LOW...NEAR 0 PERCENT.
* FORMATION CHANCE THROUGH 5 DAYS...LOW...30 PERCENT.

A NON-TROPICAL AREA OF LOW PRESSURE IS FORECAST TO FORM IN THE
NORTHEASTERN ATLANTIC OCEAN SEVERAL HUNDRED MILES WEST-SOUTHWEST OF
THE AZORES IN TWO OR THREE DAYS. SOME SLOW TROPICAL OR SUBTROPICAL
DEVELOPMENT IS POSSIBLE BY THE END OF THE WEEK WHILE THE LOW
MOVES SOUTHWESTWARD.
* FORMATION CHANCE THROUGH 48 HOURS...LOW...NEAR 0 PERCENT.
* FORMATION CHANCE THROUGH 5 DAYS...MEDIUM...40 PERCENT.

$$
FORECASTER STEWART

[Cpv17]

We will need to monitor NE Mexico/S Texas surface obs and satellite data suggest another MCV and surface low are beginning to develop. That feature will likely be the next heavy rainfall maker overnight into Monday for our Region. Keep an eye on radar to our SW for further development during the evening hours.

I was checking the HRRR model and noticed that it keeps most of the rain south of our region and along the coastline. What do you make of that?

[srainhoutx]

Frankly the HRRR as well as other mesoscale models are giving NWS and other Forecasters fits because they've not been helpful recently with those short term computer guidance. Check the radars to our S and W throughout the night and that will provide ground truth to the expected conditions tomorrow.

[unome]

from Bob Henson's pm update in Category 6 blog: https://www.wunderground.com/cat6/More- ... l-Mangkhut

A Western Caribbean/Gulf of Mexico disturbance to watch

An area of disturbed weather has formed in the Western Caribbean between Cuba and Honduras, due to the interaction of a tropical wave with an upper-level trough of low pressure. This system was moving west-northwest to northwest at about 5 – 10 mph, and will enter the Gulf of Mexico by Tuesday. The upper-level trough was creating high wind shear of 30 – 40 knots, preventing development. This trough is forecast to weaken and move northward over the next few days, creating a lower shear environment in the Gulf of Mexico that may allow development to occur, before the system moves inland over Texas on Thursday or Friday. The southeast half of Texas is already facing several days of heavy rain and localized flash flood threats this week, thanks to a midlatitude disturbance that will swing over the region and slow to a halt.

None of the 12Z Sunday runs of our reliable models of predicting tropical cyclone genesis forecasted that the Caribbean system would develop, but about 30% of the 50 members of the European model ensemble predicted development. In their 8 pm EDT Sunday Tropical Weather Outlook, NHC gave the system 2-day and 5-day odds of development of 0% and 30%, respectively.

[Andrew]

ECMWF and CMC want to develop a weak low. Still would like to see more support from the GFS before buying in. Either way rain chances across the Texas coastline will likely increase from it.

[srainhoutx]

The attachment ecmwf_uv850_vort_watl_6 (1).png is no longer available

[Cpv17]

The GFS does nothing with it, the ICON is into the mid TX coast as a tropical storm or weak cane, the CMC has what’s probably a weak tropical storm into Northern Mexico, and the Euro has a depression or weak tropical storm into the mid TX coast.

[Katdaddy]

Busy weather week ahead.

Flood Watch
National Weather Service Houston/Galveston TX
350 AM CDT Mon Sep 10 2018

TXZ200-213-214-226-227-235>238-300-313-335>338-436>438-102200-
/O.NEW.KHGX.FF.A.0008.180910T1800Z-180911T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Brazoria Islands-Chambers-Coastal Brazoria-Coastal Galveston-
Coastal Harris-Coastal Jackson-Coastal Matagorda-Fort Bend-
Galveston Island and Bolivar Peninsula-Inland Brazoria-
Inland Galveston-Inland Harris-Inland Jackson-Inland Matagorda-
Matagorda Islands-Northern Liberty-Southern Liberty-Wharton-
Including the cities of Alvin, Anahuac, Angleton, Bay City,
Baytown, Cleveland, Clute, Dayton, Devers, Dickinson, Edna,
El Campo, First Colony, Freeport, Friendswood, Galveston, Ganado,
Houston, La Marque, Lake Jackson, League City, Liberty,
Mission Bend, Missouri City, Mont Belvieu, Old River-Winfree,
Palacios, Pasadena, Pearland, Pecan Grove, Rosenberg, Stowell,
Sugar Land, Surfside Beach, Texas City, Wharton, and Winnie
350 AM CDT Mon Sep 10 2018

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

The National Weather Service in Houston/Galveston has issued a

* Flash Flood Watch for portions of south central Texas and
southeast Texas...including the following counties...in south
central Texas...Coastal Jackson and Inland Jackson. In
southeast Texas...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 Tuesday morning

* Thunderstorm activity may develop along the coast or just off
the coast this morning. Additional activity may begin to develop
this afternoon farther inland between the coast and Interstate
10. There may be a second round of thunderstorm activity to
develop overnight into Tuesday morning. The main concern with
these storms will be the rainfall rates and not so much the
total rainfall amounts for the event. Storms yesterday produced
rainfall rates of 2 inches an hour. Atmospheric conditions are
more favorable today into Tuesday to support these kinds of
rainfall rates if not more. This means that flash flooding could
occur if these rainrates persist for more than 1 to 2 hours
over the same area.

* The main impacts from these higher rain rates will be street
flooding in low lying and poor drainage areas. Rapid rises in
area creeks and bayous can be expected. Water levels should
remain within banks of bayous except if high rain rates persist
for longer than 2 to 3 hours.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

A Flash Flood Watch means that conditions may develop that lead
to flash flooding. Flash flooding is a very dangerous situation.

You should monitor later forecasts and be prepared to take action
should Flash Flood Warnings be issued.

[mcheer23]

Disorganized showers and thunderstorms over the northwestern
Caribbean Sea and western Cuba are associated with a weak surface
trough. The disturbance is forecast to move slowly northwestward
across the northwestern Caribbean Sea and the Yucatan Peninsula over
the next couple of days with only slow development expected during
that time. However, upper-level winds are forecast to become more
conducive, and a tropical depression could form late this week when
the system moves across the western Gulf of Mexico.
* Formation chance through 48 hours...low...10 percent.
* Formation chance through 5 days...medium...40 percent

[srainhoutx]

Monday morning briefing from Jeff:

Flash Flood Watch has been issued for areas along and SE of US 59 from 100pm today until 700am Tuesday.

A surface coastal trough has developed near the coast and will remain stationary for the next 36-48 hours while an area of convectively enhanced low pressure that has formed near Laredo moved ENE toward the area this afternoon and tonight.

Expect numerous showers and thunderstorms today especially along the coast and some of this activity will move inland, but become more scattered.

This evening short range models show the development of numerous showers and thunderstorms along the coastal trough and some of this activity may spread inland to US 59 Tuesday morning. It is very possible that the majority of the heavy rainfall remains right along the coast like we saw on Labor Day.

Rainfall amounts of 2-4 inches appear likely especially in the coastal counties with isolated totals of 5-6 inches. Across Harris County amounts of 1-2 inches look most likely with isolated totals of 3-4 inches. Given the high moisture levels in place hourly rainfall rates of 2-3 inches will be possible similar to rates seen on Sunday which did cause some minor street ponding issues.

Grounds are starting to become increasingly wet across the region and additional rainfall will begin to lead to greater amounts of run-off.

Mid to late week forecast will hinge on potential tropical cyclone formation over the Gulf of Mexico.

Excessive Rainfall Outlook Through Tuesday Morning:

[redneckweather]

Yep, looks like a coastal event with north Harris County and northward see scattered stuff through the rest of the week.

[srainhoutx]

Monday morning briefing from Jeff regarding the NW Caribbean Disturbance:

Increasing chances for tropical cyclone development over the central and NW Gulf of Mexico mid to late week

Residents along the NW Gulf of Mexico coast from NE MX to SW LA should closely monitor the progress of this system.

A tropical wave axis over the NW Caribbean Sea is interacting with an upper level low over the central Gulf of Mexico producing numerous showers and thunderstorms. Surface observations in the Caribbean do not indicate that a surface low pressure system is forming and currently upper level SW/WSW winds from the upper level low over the Gulf of Mexico are not favorable for development. As the tropical wave moves NW into the central Gulf of Mexico the upper level shear is forecast to gradually weaken allowing the better upper level conditions.

The GFS and CMC models bring a weak surface reflection toward the lower TX coast late this week while the ECWMF develops a stronger surface low and has a track further northward along the TX coast. The ECWMF ensembles are increasingly showing higher development potential with over 50% of the members now indicating development.

An upper level trough will remain over TX with strong high pressure over the NE US and western Atlantic which will continue a general WNW/NE steering track of the feature toward the central and NW Gulf of Mexico late this week and this weekend.

For now will maintain high rain chances already in the forecast for Thursday onward into the weekend, but the threat for heavy rainfall appears to be increasing toward the end of the week regardless if the feature develops or not. With grounds becoming increasingly saturated the threat for flooding would be increasing should any sort of tropical system head for TX.