Lake Houston Area Lucked Out With Beta

Beta is now off to the east. As of 10:30 am on 9/23/2020, the East and West Forks are well within their banks. So are the lesser tributaries with the exception of Cypress Creek. Lake Conroe is still below 200 feet. And Lake Houston, thanks to a pre-release, is only about a tenth of an inch above normal so far, though it is rising this morning.

4-Day Rainfall Total for Storm

The radar image below shows the total rainfall accumulations across the Houston Area for the duration of the storm, starting at 2:37p.m. on 9/19/2020. This was a story of selective drenching. The south and southwest sides of the city received four times as much rain as Kingwood, Crosby and Atascocita. And more than twice as much rain as Humble. They got caught under a training feeder band; we missed it.

Here are the totals associated with the different colors above:

• Light green = 2 inches
• Dark green = 3 inches
• Light purple = 4 inches
• Dark purple = 5 inches
• Light blue = 6 inches
• Dark blue = 7 inches
• Yellow = 8 inches
• Orange = 10 inches
• Red = 12 inches
• Brown = 15 inches

Harris County Flood Warning System Shows Slightly Higher Totals

The radar image may understate the totals. The four-day-rain totals from Harris County Flood Control District gages mirror the pattern above, but show slightly higher numbers. For instance, the radar image shows 3-4″ for Kingwood, but the gages show 4-5″. I live in Kingwood and my personal weather station recorded 4.92 inches for the same four-day period.

Regardless, those caught under training feeder bands on the south and southwest sides got drenched. The Lake Houston Area escaped the worst of the rains.

Sheer, Dry Air Result in Low-Side of Predictions

While these totals are within the ranges predicted at the start of the storm, they definitely fall on the low side. Why?

Space City Weather offered this. “We had two big allies over the last week; moderate wind shear to prevent Beta from strengthening, and dry air over the state from a weak front that disrupted its circulation and prevented the formation of several, thick bands of rainfall. Instead, if you watched the radar closely, there was only ever really one strong band that was perhaps 10 to 15 miles across. This just happened to set up over Houston on Monday and Monday night…”

The Lessons of Beta

Even the heaviest rains we received were about one fourth of what Harvey dropped (40-60 inches). Beta was not unusual. As Space City Weather offered, “A tropical storm that brings a range of 5 to 15 inches rain across Houston, with rainfall rates below 2 inches per hour, is a fairly common event.”

Yet some areas still flooded. In my opinion, this underscores the need for:

• HCFCD to continue and accelerate (if possible) its work.
• All governments in the region to adopt higher regulations for new developments that reflect Atlas-14 rainfall tables.
• People at all levels of government (Federal, State, Counties, Cities) to work together and make flood mitigation a top priority.
• Leaders throughout the region to realize that we are all in this together. Slowing floodwater down in one area while speeding it up in another is a losing battle that undermines the economic heart of the region.

Posted by Bob Rehak on 9/23/2020

1121 Days after Hurricane Harvey and 370 after Imelda