Month: June 2019

Over the last couple of hours, the radar has shown the heaviest rainfall congealing offshore, and this seems to be in response to falling pressures as the tropical disturbance moves north across the Gulf of Mexico. The net effect of this is that the offshore storms are robbing inland storms of moisture, and thus sapping their ability to produce really high rainfall rates like we saw earlier this morning near Wharton. This is good news for the rest of today, although we’re still going to see some scattered storms, and areas immediately along the coast, such as Galveston, may see intermittent heavy rainfall this afternoon.

Most of the region has seen manageable rains today, and rainfall rates below 2 inches per hour. But we definitely saw the bullseyes we feared develop in Wharton, Fort Bend, and Matagorda counties this morning. One gauge north of Palacios recorded 14+ inches of rain, and a pretty large region saw 6+ inches since midnight. These totals are shown below.

The forecast for Wednesday evening through Friday remains tricky. Our best guess is that storms begin to redevelop onshore tonight, but the favored area is probably just east of Houston through the Beaumont area, and into southwestern Louisiana. In Houston, on Thursday, we will probably see less coverage than Wednesday—perhaps quite a bit less. We still have some concerns about later Thursday night and Friday, and we’ll address those in posts to come. My sense, however, is that the worst of this system, in terms of organized activity, is now slowly moving away from the metro area.

A large mass of storms continues to work through the Houston metro area this morning, but the rains have been manageable for the most part, with accumulations of 1-2 inches. However, we do have some significant concerns about areas to the southwest of Houston.

A particularly strong band of showers has established itself in Wharton and Fort Bend counties this morning. One location on the Colorado River, south of Wharton, briefly recorded rainfall rates in excess of 4 inches per hour, and has measured nearly 10 inches of rainfall since shortly before sunrise. A flash flood warning is in effect for this area through 9:45 a.m., and we anticipate these storms will slowly move east, toward Brazoria, southern Harris, and Galveston counties this morning. So if you live in the southern half of the metro area, pay close attention to the radar for the next several hours.

Most of the high-resolution modeling suggests this very moist air mass will shift mostly offshore by this afternoon, perhaps by around 2pm to 4pm. This should then lead to a reprieve in widespread storms at least through this evening.

The forecast for Thursday and Friday is not particularly clear, but we do not expect quite the organized storms that we are seeing across much of the Houston metro area this morning to persist. Nevertheless, heavy rain will remain a threat heading into the weekend. We will try to firm up this forecast in a new post later today.

We got through most of last night without any issues in Houston. Storms lined up well southwest of Houston near Matagorda Bay after midnight and have arrived across most of the metro area early this morning.

Radar as of 5:40 AM shows moderate to heavy rainfall across most of the area (with the exception of Freeport and north of The Woodlands). But everyone should see at least some rain through the morning.

As the day progresses, this rain will taper off or become more scattered in nature generally north and west of US-59/I-69. But heavy rain should continue into this afternoon generally south and east of there. A Flash Flood Watch remains hoisted for most of the area. We also have most areas south and east of US-59 in a “high risk” for flash flooding from the Weather Prediction Center today.

The WPC doesn’t hand out high risks easily, so that speaks to this system’s potential. A quick reminder from us: Please use caution when out and about today. It would be good to limit travel when you can on days like this, but if you are commuting or have to be heading out somewhere, be very careful and never drive through flooded roadways.

Total rainfall through this evening is expected to be on the order of 1 to 3 inches north and west of US-59. Some folks, particularly up in far northern regions (Conroe, Navasota, Cleveland to suggest a few) may see a bit less. The trouble spots are expected south and east of US-59. We expect 3 to 6 inches on average south and east of there, but some places will see higher amounts on the order of 6 to 10 inches or even a bit more.

There are still some uncertainties with how this will exactly play out, but in general this will work for today as a forecast. This outcome would likely cause a good deal of street flooding in parts of southeast Harris, Galveston, Brazoria, and Chambers Counties. Bayou or creek flooding is also possible, especially along Clear Creek or perhaps some of the bayous in southeast Harris County.

The bottom line today: Flash flooding, particularly street flooding is likely in areas south and east of downtown Houston at times today, especially through early afternoon. Some more serious street or even creek and bayou flooding is also possible in a few places, depending on exactly how much rain falls and how quickly it does. Rain should taper off a bit, or at least become more infrequent toward mid-afternoon.

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Storms that fired up on Tuesday afternoon have died down this evening, in part due to the loss of daytime heating. Unfortunately, this is just a lull, as the tropical disturbance that will make for wet conditions through Thursday morning remains in the Gulf, roughly centered near the border between Texas and Mexico. This pre-sunset satellite image captures the size of the tropical system, and amount of moisture it can potentially bring into Texas and Louisiana as it moves north-northeast. Fortunately, it appears the heaviest rains will probably remain offshore, but we’re still definitely in watch-and-wait mode.

Our best tools to forecast rain totals over the next 24 to 36 hours, high-resolution models, have not done a tremendously good job so far today, and they’re not initializing well. This means that even 1 or 2 hours into an individual model’s run, it already is pretty far off what is actually happening on radar. So, to some extent, we’re flying blind in terms of forecasting.

Still, with high atmospheric moisture levels (precipitable water values will rise above 2.2 inches over the next day or so, which is a prerequisite for high hourly rainfall rates) and low pressure at the surface we’re all but guaranteed heavy rainfall for at least part the metro area. After the present lull, it appears as though rain showers will build back up sometime after midnight offshore, and begin to migrate inland again. It’s quite possible that Wednesday morning’s commute will be a soggy one, and with the potential for flooded streets please check road conditions before heading out. We’ll have an update before sunrise.

NOAA rainfall total estimates for now through Friday evening. (Pivotal Weather)In terms of storm totals, as mentioned, the forecast models are all over the place, but areas around Galveston Bay, including southeast Harris County, probably are at the most risk for heavy rainfall that will quickly flood streets. We’re still looking at likely rainfall totals of 2 to 4 inches for most areas, with higher localized amounts of 6 inches or greater. The region’s bayous are in pretty good shape and should be able to handle most of that. It still appears as though the heaviest rains will clear out of the area by or before noon on Thursday.