Potential Tropical Cyclone 1

NHC Issues Advisory on Potential Tropical Cyclone One

6/17/24 – At 4PM CDT, the National Hurricane Center (NHC) issued an advisory on Potential Tropical Cyclone One. The disturbance in the Gulf has a 70 percent chance of tropical formation during the next two days.

NHC also issued a tropical storm watch for Port O’Connor southward to the mouth of the Rio Grande and onward to Boca de Catan in Mexico.

If a tropical storm forms, they will call it Alberto.

A satellite photo taken this morning of Potential Tropical Cyclone One shows storm clouds already starting to wind around a broad area of low pressure centered over the Yucatan. It has been spinning rain north into Texas and Louisiana. But the main event starts tomorrow.

National Hurricane Center Atlantic-Wide Geocolor View, taken 6/17/24, early AM.

Moving NNW at 7 MPH with 40MPH Winds

Potential Tropical Cyclone One is moving toward the north-northwest near 7 mph and this general motion is expected to continue through Tuesday.  

NHC expects a turn toward the west-northwest Tuesday night or Wednesday. The system will likely approach the western Gulf coast late Wednesday.

Current maximum sustained winds are near 40 mph with higher gusts.

National Hurricane Center

Some slow strengthening is possible, The disturbance is forecast to become a tropical storm by Wednesday. Formation chance through:

  • 48 hours…high…70 percent.
  • 7 days…high…70 percent.

Potential Tropical Cyclone One is quite large with tropical-storm-force winds extending outward up to 290 miles (465 km) to the northeast of the center.

The estimated minimum central pressure is 1001 mb (29.56 inches).

Life-Threatening Flooding Likely in Mexico and Central America

“Regardless of development, several more days of heavy rainfall are expected across portions of southern Mexico and Central America. These rains are likely to cause life-threatening flooding and flash flooding.” 

The graphic below shows accumulations expected over the next five days.

Total expected rainfall from Tuesday through Sunday. Source: National Weather Service.

According to NHC, “Potential Tropical Cyclone One will produce “rainfall totals of 5 to 10 inches across northeast Mexico into South Texas, with maximum totals of 15 inches possible. This rainfall will likely produce flash and urban flooding along with new and renewed river flooding.”

Lake Houston Area Will See Far Less Rainfall

Locally, Harris County Meteorologist Jeff Lindner predicts:

  • Coastal Counties: 7-9 inches (widespread), isolated totals over 12+ inches
  • I-10 corridor: 3-5 inches (widespread), isolated totals up to 7 inches
  • North of I-10: 3-4 inches (widespread), isolated totals up to 5 inches.

Lindner adds, “The most favorable time for heavy rainfall over southeast Texas will be from Tuesday afternoon into Wednesday afternoon.”

Use the rainfall amounts above as average. Training bands can quickly result in much higher totals and flash flooding in small areas near other areas that see little rainfall.”

Watersheds Most at Risk

Where the heaviest rains fall will determine responses on area watersheds. Lindner feels most Harris County creeks and bayous can handle 4-6 inches of rainfall. However, he warns that if isolated higher totals exceed 8 inches in southern Harris County, we might see trouble on:

  • Clear Creek and its tributaries
  • Armand Bayou
  • Willow Spring Bayou
  • Big Island Slough
  • Taylor’s Bayou
  • Goose Creek
  • Berry Bayou
  • Hunting Bayou
  • Keegans Bayou
  • Willow Waterhole

Lake Report

At 5PM, the SJRA has lowered Lake Conroe by one-third of a foot.

The Coastal Water Authority has lowered Lake Houston by a full foot.

I asked Lindner how much rain he expected between the lakes. The short answer: 2-3 inches with isolated totals up to 4 inches. With that amount of lake lowering, he does not expect structural flooding. But there are other dangers.

The mouth of the Kingwood Diversion Ditch at River Grove Park shows how high sediment deposits have become. At Lake Houston’s normal level, that sand lurks just inches below the surface. Boaters have churned a temporary shallow channel through the sandbar with their props.

Mouth of Kingwood Diversion Ditch at River Grove Park on afternoon of 6/17/24 with lake down one foot.

But with all the sand coming down the West Fork from sand-mine breaches, that sediment you see above will likely increase during this storm.

Confluence of Spring Creek and West Fork (right) near US59 Bridge on 6/16/24

But the greatest immediate threat exists near the coast.

Coastal Warnings

Six to nine foot swells will be common throughout the Gulf for the next several days, according to NHC.

The combination of a dangerous storm surge and the tide will cause normally dry areas near the coast to be flooded by rising waters moving inland from the shoreline. The water could reach the following heights above ground somewhere in the indicated areas if the peak surge occurs at the time of high tide…

  • Sargent, TX to Sabine Pass, TX…2-4 ft
  • Galveston Bay…2-4 ft
  • Mouth of the Rio Grande, TX to Sargent, TX…1-3 ft
  • Sabine Pass, TX to Vermilion/Cameron Parish Line, LA…1-3 ft

Surge-related flooding depends on the relative timing of the surge and the tidal cycle.

Posted by Bob Rehak on 6/17/24 at 5PM based on information from NHC and NWS

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