Expected heavy rains

Lakes Being Lowered in Advance of Expected Heavy Rains

6/14/24, 10:00 AM – The San Jacinto River Authority (SJRA) is lowering Lake Conroe and the Coastal Water Authority (CWA) is lowering Lake Houston in advance of expected heavy rainfall associated with a tropical disturbance in the Gulf of Mexico.

At this hour, forecasters predict storms could drop 3-6 inches of rain on the Houston area with the highest totals near the coast. But rain should drop off fairly sharply inland. However, uncertainty remains about how sharp the drop off will be.

Timing of Rain

Most of the rain should fall Monday through Wednesday, but could start as early as Sunday night. However, some models are beginning to forecast the heaviest rains from Tuesday into early Thursday.

Either way, dam operators should have time to lower their respective lakes and create extra storage capacity for stormwater.

Location of Disturbance

At 7:44 AM EDT, the center of the area of concern had not moved since yesterday. Moisture continues to build in the Bay of Campeche. But forecasters have increased the chances of any disturbance turning into a named storm from 40% yesterday to 50% today.

The National Hurricane Center has this to say: “A broad area of low pressure is forecast to form over the southwestern Gulf of Mexico late this weekend or early next week. Environmental conditions appear conducive for gradual development of this system, and a tropical depression could form during the early or middle part of next week while it moves slowly westward or west-northwestward.”

Houston Will Not Likely Take Direct Hit, But…

Jeff Lindner, Harris County’s meteorologist says, “The Houston area will not likely take a direct hit from the system. While any tropical depression/storm is likely to remain south of the upper Texas coast, the deep ESE/SE fetch of moisture on the northeastern side of the feature will begin to arrive along the Texas coast as early as late Sunday and more likely into Monday and Tuesday.”

He continued, “It should be noted that the broad nature of this system and potentially ill-defined surface circulation will likely result in impacts spread well away from the actual low itself. Also, until any actual surface low forms, uncertainty will remain with the forecasts and impacts.”

Some models are predicting “outer banding features” in the Houston area. Despite a fair amount of uncertainty, the incoming tropical air mass could drop high amounts of rainfall in a short period of time.

That said, the National Weather Service has released this map showing predicted rainfall amounts for the next seven days.

Lakes Conroe and Houston Both Pre-Releasing

In preparation, Lake Conroe began releasing 660 cubic feet per second (CFS) after a City of Houston request early Friday morning. That is the maximum amount the SJRA can release before a storm under its permit. As the lake starts filling, that amount increases.

Mark Micheletti, an SJRA board member, said that SJRA hopes to lower the lake by six inches before the rains arrive.

Simultaneously, the CWA has opened the gates on the Lake Houston Dam. CWA is currently releasing 1335 CFS.

So, Lake Houston is releasing water twice as fast. And Lake Houston is half the size of Lake Conroe. Therefore, areas downstream should see lower lake levels faster. As it should be. Remember that Lake Houston is 30 miles closer to the coast, where forecasters expect the highest rainfall.

All gates on Lake Houston have been fixed and are fully operational.

Wind and Tide Impacts

For many people, rain isn’t the only concern. According to Lindner, “Winds will also start to increase early next week as the pressure gradient tightens between the deepening area of low pressure to the southwest and building high pressure over the SE US. Winds of 20-30mph can be expected across the Gulf/nearshore/and inland bays with 20-25mph across the coastal counties,” according to Lindner.

For boaters and all those who work offshore, nearshore seas will build into the 4-6 ft range by Monday morning and 5-8 ft by Tuesday morning with offshore heights approaching 8-10 ft.

The current tide forecast indicates values of 1-2 ft above normal. But when coupled with the building seas at times of high tide water levels may get close to coastal flooding thresholds. That should happen Tuesday and Wednesday.

Some beach front locations will begin to experience minor coastal flooding around 3-4 ft above normal tide levels.

Given the potential prolonged nature of the ESE winds across the Gulf, we have the potential for tidal trapping. That’s when incoming seas won’t let the previous high tide drain away. This can, over time, build water levels in the bays. 

Posted by Bob Rehak on 6/14/24

2481 Days since Hurricane Harvey