Category: Tropical weather

Rain, rain (won’t quite) go away

Posted by Matt Lanza at 5:52 AM

After an on-again/off-again dry summer in the Houston area, the last 10 days have felt like we’ve been dodging a continuous faucet. We will continue to deal with this into later this week and weekend.

Quick situational awareness for you:

  • A Flash Flood Watch is in effect generally along and southeast of US-59, so primarily for the coastal counties in our area until later today. A watch means flooding, especially street flooding, is possible.
  • We’re expecting periods of rain, possibly heavy at times, through tomorrow, with a bit more possible Wednesday and Thursday.
  • Our Caribbean/Yucatan tropical disturbance (Invest 95L) remains disorganized this morning. The National Hurricane Center (NHC) gives it a 60% chance of development as it comes across the Gulf later this week. We think the ceiling on intensity is low, but this system does bring more locally heavy rain risk to parts of Texas.

Through Thursday

As I write this morning, heavy rain is south and east US-59, mainly impacting coastal Brazoria County and much of Galveston, and Chambers Counties.

This morning’s radar loop shows the heaviest rains south and east of Houston, a trend that should hopefully continue pushing offshore today. A Flash Flood Watch remains in effect south & east of the city through this afternoon. (College of DuPage)

A Flash Flood Warning is posted for the west shore of Galveston Bay through Texas City back into western Galveston County. That goes until 7 AM, as they’ve seen healthy amounts of rain in that area overnight.

Look for rain to continue this morning, though with perhaps a gradual focus more to the east or offshore. It’s possible areas north and west of Houston stay quiet much of this morning before some scattered downpours this afternoon. The most likely area to see rain continue at a healthy pace at times will be along the coastline or near Galveston Bay.

Additional rain of one to three inches is possible along the coast and just inland. If rain hugs the coast longer than expected this morning and afternoon, totals could be higher in Galveston through Freeport. Areas north and west of Houston will see more sporadic, scattered amounts of less than an inch in most cases.

An additional 1-3″ of rain will be possible through early Wednesday morning south and east of Houston, with lesser, more scattered amounts north and west. (NWS)

More rain will be possible tonight, once again along the coast, however we expect the heaviest rain tonight to stay south and east of Houston and mostly offshore. Flash Flood Watches are expected to expire as long as that remains the case We’ll re-evaluate that later today and probably have a brief update for you this evening and let you know if NWS extends the Flash Flood Watch through tonight for the coast.

From this vantage point, the forecast for Wednesday and Thursday is pretty straightforward: Scattered showers and thunderstorms are likely on both days. We still need to iron out specifics and details, but expect more pockets of locally heavy rain, though they aren’t expected to be widespread at this point. Just a generic, “It’s probably going to rain at a few points between both days” will have to suffice for now.

Clouds and rain are at least holding down temperatures. Look for temperatures to range from the upper-70s to around 80° if it stays cloudy and dreary all day to the mid-80s if we see some occasional sunshine.

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A solid round of showers and thunderstorms rolled through Houston on Monday during the daytime, dropping 0.5 to 2.0 inches of rain for most of the area. It now seems likely that the radar will quiet down for most of this evening, before heavier showers being to develop along the coast on Tuesday morning like on Monday morning. The National Weather Service has prudently kept a Flash Flood Watch in place for coastal counties, and the inland tier including Harris County, through noon Tuesday (Note: after this post was published Monday afternoon, the flood watch was extended until 6pm CT Tuesday. Our forecast remains unchanged.) The best hope is that the heaviest precipitation stays just offshore, rather than migrating on shore during the next 24 hours or so.

Area of flash flood watch. (National Weather Service)

Unfortunately, rain chances are not going to go away on Wednesday and Thursday. Although rain showers should be more scattered in nature, and perhaps less intense, we definitely can’t rule out locally heavy rainfall due to the tropical air mass and overall stagnant pattern. Given all of this, we expect accumulations of 1 to 3 inches for inland areas from now through Thursday, with 2 to 5 inches more likely for areas immediately along the coast (with higher isolated totals). The primary threat should be street flooding rather than significant stream and bayou flooding.

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Man, I hate this time of year. Invariably, the tropics reach their crescendo, and this year is no different. In fact, this is only the 11th time on record that three hurricanes have been active in the Atlantic simultaneously, Florence, Helene, and Isaac. This week, Hurricane Florence will rightly suck up a lot of the national oxygen—Matt did a commendable job of summarizing the risks to the Carolinas and beyond, and they are tremendous in terms of flooding, wind, and surge—but we have some homegrown threats to consider as well.

Tropics as of 7am CT on Monday. (National Hurricane Center)

For this post we are going to focus on the near-term threat of heavy rainfall on Monday and Tuesday, and then the late-week threat from a nascent tropical system. Did I mention that I hate this time of year?

Monday and Tuesday flood watch

The National Weather Service has issued a Flash Flood Watch for the coastal and inland tier of counties for 1pm Monday through Tuesday morning, and they admit they may have to extend it. Basically, we have a lot of low pressure hanging around and a super-moist atmosphere. I think at best we can hope for scattered, heavy rain showers; and at worst we probably will see some spots of 3 to 6 inches over the next two days. Most likely the hardest hit areas will be along the coast, and if we’re lucky the heaviest rains will fall offshore.

Area of flash flood warning in effect through Tuesday morning. (National Weather Service)

Both Monday, Monday night, and Tuesday will probably be similar in this regard. We’ll just have to watch radar trends and if you have to drive for more than a short errand, you should probably check road conditions at your destination. This shouldn’t be anything more than street flooding, but we can’t guarantee that.

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Sorry for a later update than I would have hoped. Cable/internet outage due to storms and daddy duty called!

Lots of rain in and around the Houston area today, so we want to provide you a quick refresh on what’s going on with this rain, the tropics, and what to expect to start your week.

Monday & Tuesday rain

Radar as of this evening shows rain winding down across the area. Total rainfall over the last two days has been variable, with some places seeing minimal amounts and others seeing 2-3″ or even a little more.

Total rainfall since Saturday has been on the order of a half inch or less to three inches or more depending on your location. As usual, Houston rains are quite variable. (Harris County Flood Warning System)

Expect a mostly quiet night tonight. But, as we go into tomorrow, a number of things may come together to produce another round of heavy rainfall in the area. Eric will have more on the timing and the where tomorrow morning, but I would have the umbrella by the door tonight at the ready before you head out for work or school.

Look for more showers and thunderstorms in the area Monday night or Tuesday. It’s tough at this timescale to narrow down specifics, but suffice to say, locally heavy rainfall will be possible. A Flood Watch isn’t posted for the area, but depending on how we do tomorrow, we may need one Tuesday. Street flooding is the main concern with this event.

Total rainfall from tonight through Tuesday evening is expected to average about 1-3″ across the area. Some may see more, others less, however. (NWS)

How much rain? On average, we expect most folks will see another 1-3″ on top of what’s fallen. Since “average” is just a combination of extremes, that means some folks may see less than an inch and others may see four or five inches of rainfall. Again, we don’t expect widespread problems and street flooding is the biggest concern right now.

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