Eric Berger

Simply put, all heck is breaking loose across the city as a slow-moving band of heavy rainfall slogs through Houston today. Unfortunately, while we knew heavy rainfall was likely in parts of the city today, we did not anticipate an event as significant in scope as this for Thursday. So far we have seen rainfall rates of 4 and 5 inches per hour in parts of the metro area, and it has caused widespread problems for much of Houston. Here’s three separate systems as of noon CT that bear watching.

It is hard to have too much confidence moving forward, but very generally we can expect these storms to sag slowly to the south during the rest of the afternoon. We think rainfall rates have probably peaked as cloud tops associated with the system have started to warm a little bit, indicating less potential to produce the very heaviest rainfall rate. But in a slow-moving storm, 3 inches per hour can flood is more than enough to very quickly cause flooding.

The key message right now is that if you are in a dry location and it is raining heavily at your outside, you should not leave. If you have to drive through heavy rains, or heavily hit areas to get to your destination, stay where you are. Above all, do not drive into high water. A lot of people die that way. This storm will pass. We still have a general expectation that the overall system will weaken during the afternoon hours, and begin to dissipate after sunset.

We’re continuing to track a very intense band of rainfall just north and east of Houston, which has been producing rainfall rates of 2 to 4 inches per hour. The National Weather Service has declared a Flash Flood Emergency until 11:15 am for Southeast Montgomery County, Northeast Harris County, and Liberty County. This is enough to quickly flood streets and back water up into yards (and over a long enough period of time, homes). This band is now slowly sagging into the Houston metro area, as seen on the radar image below.

We do not have a ton of confidence in the forecast other than this band should progress through most if not all of Harris County today, potentially bringing 2 to 8 inches of rainfall later this morning and afternoon. We do not know if it will strengthen further (unlikely), remain the same, or (hopefully) weaken as it progresses throughout the day. Needless to say it has the potential to disrupt any activities today, and we are likely to see flash flooding in the metro area as it moves through.

Meanwhile, the greater Beaumont region continues to experience a massive flooding situation as overnight rains devastated the area, and to some extent, are continuing this morning. The city has conducted hundreds of high-water rescues.

Good morning. Before jumping in to today’s post, I wanted to apologize for site outage problems during the overnight hours. This is very unfortunate timing and we will correct the problem going forward.

On Wednesday night, as anticipated, much of the Houston region passed a relatively quiet night. However, the same cannot unfortunately be said for regions to the east and northeast of Harris County. An extreme rainfall event has unfolded over Jefferson and Orange counties. This morning, the National Weather Service took the rare step of issuing a “Flash Flood Emergency” for the region, warning residents that, “This is an extremely dangerous and life-threatening situation. Do not attempt to travel unless you are fleeing an area subject to flooding or under an evacuation order.”

This is really a terrible situation for Beaumont, Winnie, and surrounding areas. There are major issues on Interstate 10 through the area. Some areas have seen 10 to 15 inches of rainfall during the overnight hours, and a thick band of rainfall due to Imelda continues to saturate the area. It is showing no signs of movement for the next couple of hours.

With respect to Houston, we have some concerns later today. A related band of storms near Conroe and Cleveland will likely eventually sag southward today. Accordingly, parts of Montgomery County will likely see 2 to 8 inches of rainfall today, and some northern and central parts of Harris County may see 2 to 6 inches of additional rainfall. These areas of the Houston region have, until now, been somewhat unaffected by Imelda’s heaviest rains so they can probably handle most of this rain. That doesn’t mean there won’t be any street flooding, however.

We probably will see some additional storm development later today, but most of the activity should wind down this evening as the sun sets. By Friday morning we should return to more normal, business-as-usual pop-up thunderstorms. So we’ve all got to get through one more day of Imeda-misery. We will update accordingly.

As of midday Wednesday, we’re starting to feel pretty good about the chance of Houston avoiding significant flooding from the remnants of Tropical Storm Imelda. We’re not entirely in the clear, to be sure, but the threat is shifting east away from the metro area. First of all, let’s take a big picture look at the radar at Noon.

As you can see, Imelda’s remains are producing a very broad circulation, with several distinct banding features from along the Texas coast to well into Louisiana and northeast Texas. Houston residents will also take note that these strongest bands are generally moving away from the metro area.

Based upon the latest modeling trends, we expect this trend to continue today. While the Houston metro area may see an additional 1 to 4 inches of rainfall over the rest of Wednesday and through Thursday (especially to the east of Interstate 45), the threat of sustained, heavy, and flooding rainfall is diminishing. We can see this based upon the HREF model output, which is an ensemble of several models that attempt to predict smaller-scale convection during rainfall events. Of all the models we’ve looked at so far during this event, the HREF has arguably done the best. Here is its output for now through Thursday.

The bottom line is that right now we expect the Houston region, including hard hit areas in Brazoria and Galveston counties, to generally see improving conditions from here on forward. Intermittent storms may well pop up, but right now, we anticipate that most areas can safely return to business-as-usual activities. For areas east of Houston through Beaumont, however, we definitely have concerns about ongoing heavy rainfall, and will continue to monitor that situation.