The heavy rainfall threat for the northeast Houston area from PTC1 (Potential Tropical Cyclone #1) has shifted southwest somewhat today. While the storm takes its time getting organized, high pressure from the eastern US is building into the Houston area. That’s squeezing the heaviest rains toward the coast and the Rio Grande Valley.
Meanwhile, the National Hurricane Center warns of a second storm forming next week exactly where PTC1 is forming now. But it will likely head north, not west.
Heaviest Rainfall from PCT1 Shifting Southwest
Over the weekend, early predictions suggested heavy rains would arrive in the Lake Houston Area on Monday. Monday’s predictions suggested Tuesday. And now Tuesday’s predictions say the Lake Houston Area might get 1-3 inches of rain during the next three days.
The National Weather Service (NWS) now predicts PTC1 will produce rainfall totals of 5 to 10 inches across northeast Mexico into South Texas. Maximum totals could approach 15 inches.
This rainfall will likely produce flash and urban flooding along with new and renewed river flooding.
NWS also predicts the broad circulation of PTC1 could produce extreme rainfall in Central America. Totals could average 10 to 20 inches with maximum amounts of 25 inches. Areas most affected include the Pacific coast of far southern Mexico, southern Guatemala, much of El Salvador, western Honduras, and far western Nicaragua.
Here’s what the storm looked like earlier today from space.
Landfall in Mexico
As of 4PM CDT Tuesday, NWS predicted PTC1 would make landfall in Mexico sometime within the next 24 to 36 hours as a tropical storm. They currently give it an 80% chance of formation.
At present, the storm exhibits wind speeds approaching tropical storm strength (39+ MPH). Tropical storm conditions could begin tonight or Wednesday along portions of the Texas coast south of San Luis Pass.
Tropical storm force winds extend outward 415 miles north of the center.
So focus less on the track and more on the impact.
The National Hurricane Center (NHC) warns, “Regardless of the exact track of the low, this system will have a large area of heavy rains. Expect moderate coastal flooding and tropical-storm-force winds well north of the center.”
Moderate coastal flooding is likely along much of the Texas Coast through midweek.
If PTC1 becomes a tropical storm, its name will be Alberto.
Double Trouble?
NHC’s website showed something unusual today. One possible tropical system could develop within the area vacated by another. Within days of each other!
NHC gives a 20% chance of the second storm developing in the yellow area with the red X.
But instead of moving into Mexico, they predict the second storm could move northward. That could make it a direct threat to Houston.
So check NHC’s weather forecasts daily during hurricane season. As PTC1 proves, weather can change quickly.
Posted by Bob Rehak on 6/18/24
2485 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2024/06/180154WPCQPF_sm.gif?fit=892%2C716&ssl=1716892adminadmin2024-06-18 17:27:272024-06-18 17:32:42Heaviest Rainfall Threat from PTC1 Shifting Southwest
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.
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.
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
2484 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2024/06/Gulf-20240617.jpg?fit=1100%2C631&ssl=16311100adminadmin2024-06-17 17:42:542024-06-22 10:42:40NHC Issues Advisory on Potential Tropical Cyclone One
6/16/24 – 8 PM update – As of 8 PM, the National Hurricane Center has increased the chances of tropical formation to 70% from 50% for the disturbance in the Bay of Campeche.
Excessive rainfall and flash flooding chances are increasing for the middle part of the week. Coastal counties could see 8-11 inches in widespread areas with isolated totals topping 12 inches.
According to Harris County Meteorologist Jeff Lindner:
The I-10 corridor could experience 5-8 inches (widespread) with isolated totals up to 10 inches
North of I-10, people will see 3-5 inches (widespread) with isolated totals up to 8 inches.
Much of the rainfall will come over a 36-48 hour period (Tuesday and Wednesday).
National Weather Service gives most of Harris County a 3 out of 4 chance for excessive rainfall.
All of this rain is in association with a tropical disturbance in the Bay of Campeche.
The National Hurricane Center has increased the chances of tropical formation for that red area in the Gulf to 70%.
Whether the storm gets a name or not, it will impact the Houston area in several ways.
Forecasts have been trending upward with rainfall amounts over the last 24 hours. Given the incoming tropical moisture combined with the potential for cell training and high hourly rainfall rates, flash flooding is becoming an increasing concern.
Sustained heavy rains will be possible from Tuesday afternoon into Wednesday over the area.
High hourly rainfall rates will result in rapid onset flash flooding.
Jeff Lindner, Harris County Meteorologist
Uncertainty remains as to where any sustained banding features will form and how far inland the heavy rainfall threat may extend. Stay tuned for changes to the forecast.
Significant rises on area creeks, bayous, and rivers will be likely given the rainfall forecast. Where maximum totals occur, overbank flooding will be possible on creeks and bayous. Rivers which are still elevated from the spring rainfall will also likely see additional rises. However, flooding will depend on the position, magnitude, and coverage of the heavier rains and the inland extent.
Lake Conroe Being Lowered
In preparation, the San Jacinto River Authority continues to lower Lake Conroe. On Sunday morning, it was at 200.82 feet, several inches below its normal level of 201 feet. At 10 AM, SJRA was discharging 660 cubic feet per second.
Lake Houston Discharge Rate Jumps 7X
Downriver, the Coastal Water Authority increased the discharge rate from Lake Houston. The rate jumped from 1386 CFS to 9,905 CFS between 5 AM and 7 AM this morning.
Note steep jump in discharge rate at the far right.
Gusty Winds, Coastal Flooding, Dangerous Seas
As the much-advertised tropical weather event unfolds over the western Gulf of Mexico in the next 24 hours, Lindner anticipates increasing impacts, especially along the Texas Coast.
The plume of tropical moisture will arrive late tonight into Monday. Scattered showers will begin to work toward the coast tonight. Even greater moisture will flow inland Tuesday and Wednesday.
Banding thunderstorms and cell training will create potential for flash flooding. Models have trended upwards in the last 24 hours. The National Weather Service has given all areas south of I-10 a level 3 out of 4 flash flood risk from Tuesday morning to Wednesday morning.
Wind Forecast
According to Lindner, winds will begin to increase on Monday, but really ramp up Tuesday into Wednesday. Coastal areas will likely experience frequent gusts to gale force.
Coastal waters: 35-45mph
Coastal counties: 25-40mph
Inland: 25-30mph
Coastal Flooding Likely Mid-Week During High Tides
Lindner expects building seas and elevated tides to exceed coastal flood thresholds along the upper Texas coast, especially Tuesday and Wednesday. Total water levels are forecasted to reach 4.5-5.5 feet above barnacle level along the Gulf facing beaches late Tuesday into Wednesday and 4.0-5.0 feet in Galveston Bay.
Minor coastal flooding is likely late Tuesday into Wednesday in the usual low lying coastal areas (Bolivar, west end of Galveston Island, Blue Water Highway, Tiki Island, San Leon, Seabrook, Shoreacres).
Water and debris may cover portions of HWY 87 near HWY 124 on Bolivar at high tide. Low lying coastal roads will likely be impacted and covered with sea water at times of high tide.
10-12 Foot Seas
Lindner also warns that extreme dangerous/hazardous marine conditions will develop across all waters Tuesday into Wednesday. Seas will build 5-9 feet on Tuesday offshore and 4-6 feet in bays. Then they will build 10-12 feet on Wednesday offshore and 5-7 feet in bays.
Sustained winds of 30-40mph with frequent gusts of 45mph will be common across our local waters. Expect frequent squalls and periods of heavy rainfall and reduced visibility. Small craft should be secured in port by late Monday and remain in port until conditions improve.
Posted by Bob Rehak on 6/16/24 based on information from Jeff Lindner, Harris County Meteorologist, and NWS
2483 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2024/06/GQMc-Mea0AAQPCN.jpeg?fit=1243%2C705&ssl=17051243adminadmin2024-06-16 10:09:522024-06-16 20:05:17Flash Flooding Chances Increase for Tuesday, Wednesday
Heaviest Rainfall Threat from PTC1 Shifting Southwest
The heavy rainfall threat for the northeast Houston area from PTC1 (Potential Tropical Cyclone #1) has shifted southwest somewhat today. While the storm takes its time getting organized, high pressure from the eastern US is building into the Houston area. That’s squeezing the heaviest rains toward the coast and the Rio Grande Valley.
Meanwhile, the National Hurricane Center warns of a second storm forming next week exactly where PTC1 is forming now. But it will likely head north, not west.
Heaviest Rainfall from PCT1 Shifting Southwest
Over the weekend, early predictions suggested heavy rains would arrive in the Lake Houston Area on Monday. Monday’s predictions suggested Tuesday. And now Tuesday’s predictions say the Lake Houston Area might get 1-3 inches of rain during the next three days.
The National Weather Service (NWS) now predicts PTC1 will produce rainfall totals of 5 to 10 inches across northeast Mexico into South Texas. Maximum totals could approach 15 inches.
This rainfall will likely produce flash and urban flooding along with new and renewed river flooding.
NWS also predicts the broad circulation of PTC1 could produce extreme rainfall in Central America. Totals could average 10 to 20 inches with maximum amounts of 25 inches. Areas most affected include the Pacific coast of far southern Mexico, southern Guatemala, much of El Salvador, western Honduras, and far western Nicaragua.
Here’s what the storm looked like earlier today from space.
Landfall in Mexico
As of 4PM CDT Tuesday, NWS predicted PTC1 would make landfall in Mexico sometime within the next 24 to 36 hours as a tropical storm. They currently give it an 80% chance of formation.
At present, the storm exhibits wind speeds approaching tropical storm strength (39+ MPH). Tropical storm conditions could begin tonight or Wednesday along portions of the Texas coast south of San Luis Pass.
So focus less on the track and more on the impact.
The National Hurricane Center (NHC) warns, “Regardless of the exact track of the low, this system will have a large area of heavy rains. Expect moderate coastal flooding and tropical-storm-force winds well north of the center.”
Moderate coastal flooding is likely along much of the Texas Coast through midweek.
If PTC1 becomes a tropical storm, its name will be Alberto.
Double Trouble?
NHC’s website showed something unusual today. One possible tropical system could develop within the area vacated by another. Within days of each other!
NHC gives a 20% chance of the second storm developing in the yellow area with the red X.
But instead of moving into Mexico, they predict the second storm could move northward. That could make it a direct threat to Houston.
So check NHC’s weather forecasts daily during hurricane season. As PTC1 proves, weather can change quickly.
Posted by Bob Rehak on 6/18/24
2485 Days since Hurricane Harvey
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.
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.
Some slow strengthening is possible, The disturbance is forecast to become a tropical storm by Wednesday. Formation chance through:
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.
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:
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:
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.
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.
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…
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
2484 Days since Hurricane Harvey
Flash Flooding Chances Increase for Tuesday, Wednesday
6/16/24 – 8 PM update – As of 8 PM, the National Hurricane Center has increased the chances of tropical formation to 70% from 50% for the disturbance in the Bay of Campeche.
Excessive rainfall and flash flooding chances are increasing for the middle part of the week. Coastal counties could see 8-11 inches in widespread areas with isolated totals topping 12 inches.
According to Harris County Meteorologist Jeff Lindner:
All of this rain is in association with a tropical disturbance in the Bay of Campeche.
Whether the storm gets a name or not, it will impact the Houston area in several ways.
Forecasts have been trending upward with rainfall amounts over the last 24 hours. Given the incoming tropical moisture combined with the potential for cell training and high hourly rainfall rates, flash flooding is becoming an increasing concern.
Sustained heavy rains will be possible from Tuesday afternoon into Wednesday over the area.
Uncertainty remains as to where any sustained banding features will form and how far inland the heavy rainfall threat may extend. Stay tuned for changes to the forecast.
Last week, NWS was predicting far less rain from this system.
Significant Rises Likely on Waterways
Significant rises on area creeks, bayous, and rivers will be likely given the rainfall forecast. Where maximum totals occur, overbank flooding will be possible on creeks and bayous. Rivers which are still elevated from the spring rainfall will also likely see additional rises. However, flooding will depend on the position, magnitude, and coverage of the heavier rains and the inland extent.
Lake Conroe Being Lowered
In preparation, the San Jacinto River Authority continues to lower Lake Conroe. On Sunday morning, it was at 200.82 feet, several inches below its normal level of 201 feet. At 10 AM, SJRA was discharging 660 cubic feet per second.
Lake Houston Discharge Rate Jumps 7X
Downriver, the Coastal Water Authority increased the discharge rate from Lake Houston. The rate jumped from 1386 CFS to 9,905 CFS between 5 AM and 7 AM this morning.
Gusty Winds, Coastal Flooding, Dangerous Seas
As the much-advertised tropical weather event unfolds over the western Gulf of Mexico in the next 24 hours, Lindner anticipates increasing impacts, especially along the Texas Coast.
The plume of tropical moisture will arrive late tonight into Monday. Scattered showers will begin to work toward the coast tonight. Even greater moisture will flow inland Tuesday and Wednesday.
Banding thunderstorms and cell training will create potential for flash flooding. Models have trended upwards in the last 24 hours. The National Weather Service has given all areas south of I-10 a level 3 out of 4 flash flood risk from Tuesday morning to Wednesday morning.
Wind Forecast
According to Lindner, winds will begin to increase on Monday, but really ramp up Tuesday into Wednesday. Coastal areas will likely experience frequent gusts to gale force.
Coastal Flooding Likely Mid-Week During High Tides
Lindner expects building seas and elevated tides to exceed coastal flood thresholds along the upper Texas coast, especially Tuesday and Wednesday. Total water levels are forecasted to reach 4.5-5.5 feet above barnacle level along the Gulf facing beaches late Tuesday into Wednesday and 4.0-5.0 feet in Galveston Bay.
Minor coastal flooding is likely late Tuesday into Wednesday in the usual low lying coastal areas (Bolivar, west end of Galveston Island, Blue Water Highway, Tiki Island, San Leon, Seabrook, Shoreacres).
Water and debris may cover portions of HWY 87 near HWY 124 on Bolivar at high tide. Low lying coastal roads will likely be impacted and covered with sea water at times of high tide.
10-12 Foot Seas
Lindner also warns that extreme dangerous/hazardous marine conditions will develop across all waters Tuesday into Wednesday. Seas will build 5-9 feet on Tuesday offshore and 4-6 feet in bays. Then they will build 10-12 feet on Wednesday offshore and 5-7 feet in bays.
Sustained winds of 30-40mph with frequent gusts of 45mph will be common across our local waters. Expect frequent squalls and periods of heavy rainfall and reduced visibility. Small craft should be secured in port by late Monday and remain in port until conditions improve.
Posted by Bob Rehak on 6/16/24 based on information from Jeff Lindner, Harris County Meteorologist, and NWS
2483 Days since Hurricane Harvey