TD Imelda marching north, heavy rain for many tonight

Tropical Storm Imelda has begun its transformation into a significant “blob” of rain over Southeast Texas this evening. Let us walk you through what we are expecting through Wednesday morning.

Now

Imelda is now classified as a tropical depression, and if I’m reading the radar correctly, the center as of 7:45 PM was located just west of Pearland and becoming more diffuse.

You can see from the radar loop above that Imelda has 2 or 3 areas of main concern, as it relates to rainfall. There is the main “core” of the storm over Brazoria County. This will be the primary rain producer this evening. As the center crawls north, that will come with it. This is what we are concerned about for the bulk of the Houston Metro.

The second area is a feeder band to the east of Baytown. That is aimed at parts of Galveston Island and north toward Chambers and Liberty Counties. That is not expected to move much, and within this region, expect heavy rain and potentially localized flooding overnight.

The third area is a band well to our east, aimed at the Beaumont/Port Arthur area or just west. That will be capable of some heavy rainfall tonight as well. But it may weaken a bit as this band near Baytown takes over.

So a lot happening here.

Overnight

I mentioned above that Imelda’s center is becoming more diffuse. That means that more erratic behavior of the storm track could occur. So expect that heavy rain currently located over Brazoria, Galveston, and southeast Harris Counties to lift north into the bulk of the Houston metro area. At nighttime, tropical systems can sometimes see rains intensify a bit. So I fully expect heavy rain at times in Houston and points south and east. At a minimum we would expect 2 to 5 inches of additional rain in these areas by sunrise on Wednesday. We could see some spots pick up as much as 5 to 8 inches or even more, however, and those would be the areas we’re most concerned with in terms of flooding. Again, that would be most likely from Downtown Houston south and east.

For those north and west of Downtown Houston, we expect periods of rain overnight, locally heavy. While we will monitor those areas for flooding risks, we do not think it is quite as serious as south and east. But given that there is still a degree of uncertainty with this system, the entire region should monitor the progress of the rain, both before bed and when you wake up. Do not assume tomorrow that you’ll be able to get to the airport or to work without issues, so make sure to check in on what has transpired overnight in the morning.

Wednesday daytime

We should see rains continue off and on through the day Wednesday. We could see a bit of a lull in the activity for a time during the afternoon hours before heavy rain sets back up late. Again, we have some uncertainty around exactly how tomorrow will unfold. Eric will have an update later this evening, and I will update you more on Wednesday’s outlook in the morning.

Wednesday evening and beyond

We expect another round of heavy rain tomorrow night, again in multiple areas. We’ll likely see the “core” of the storm reignite tomorrow night with heavy rain gradually lifting north of Houston. We aren’t entirely sure if that will be aligned over the center of the city or more to the east. We also will likely see another significant “feeder” type band east of Houston, though we’re not quite certain where that will be aimed. Check with us tomorrow for the latest on these aspects of the storm. We could see some very heavy rain from this, and with the grounds certainly saturated by then, we would expect a good amount of flooding risks, potentially significant to develop. We continue to expect event totals to be on the order of 5 to 10 inches on average, with isolated smaller areas seeing as much 20 inches or more.

Eric and I will continue with a Stage 3 flooding event expectation for Imelda’s rains tonight, tomorrow, and Thursday. This remains an evolving situation though, and it would be best to check back for the latest several times through the event. Eric will have an update around midnight.