The National Weather Service (NWS) Storm Prediction Center and Harris County have issued outlooks for today that include risks of heavy rainfall, hail, high winds, tornadoes and street flooding.
NWS predicts an “enhanced risk” of severe weather (3 on a scale of 5) with a 10%-14% chance of tornados. NWS rates the excessive, heavy rainfall risk as slight (at least 15%).
Light rainfall has already begun in the Lake Houston area and will increase throughout the morning hours as storms approach and pass through. The threat should be past us by 3-4 PM, just in time for school pickup.
NWS severe weather outlook as of 12:01 a.m. CST.NWS tornado outlook as of 12:01 a.m. CST.NWS excessive rainfall outlook as of 1:55 a.m. Houston time.
Rainfall Accumulation
Jeff Lindner, Harris County’s meteorologist, warns, “Forecasters have tended to increase rainfall amounts over the last 24 hours with the potential for storm clustering and cell training in southwest to northeast bands.”
Lindner says rainfall amounts of 1-3 inches appear to be common today with higher isolated totals of 4-5 inches especially for areas south of I-10, where activity may linger into the evening hours.
Moisture levels will be high for late November. Plus onshore winds will feed more moisture into the area. Widespread showers and thunderstorms are likely.
Some models show banding and training of storms this afternoon into the evening hours. But that’s for areas mainly south of I-10 and around Galveston Bay (SE Harris, Liberty, Chambers, Galveston, Brazoria Counties).
Potential for 1-2 Inches Per Hour, Street Flooding
Soils are generally dry over the area, but hourly rainfall rates of 1-2 inches per hour may result in some street flooding at the usual flood-prone locations.
The front will sag off the coast tonight into early Friday, but you can expect additional disturbances across the region on Friday with showers and thunderstorms expanding inland toward the I-10 corridor.
Wind and Hail
While much focus has been on the tornado threat, we also have the potential for damaging wind and large hail. Stronger showers may produce 40-50mph winds today. Additionally, gradient winds of 25-30mph with a few higher gusts will be common over the area for much of the day with the coastal locations seeing the stronger winds.
Posted by Bob Rehak on 11/30/23 at 7:40 a.m. based on information from NWS and Jeff Lindner
2284 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2023/11/image003.png?fit=887%2C699&ssl=1699887adminadmin2023-11-30 07:36:082023-11-30 07:39:19Heavy Rainfall, Hail, High Winds, Tornados, Street Flooding Possible Today
Says Lindner, “Early on the 24th, surface low pressure developed over south-central Texas. It helped draw a warm front northward. It eventually formed a line from near Sealy to Downtown Houston to Chambers County. This warm front when combined with strong lift, impressive low level wind shear, and winds changing direction, resulted in the formation of supercell thunderstorms along a line from near Victoria to Sealy to Conroe.
They trained across northwest Harris County. Rainfall amounts southeast of US59 ranged from 1-2 inches, but 2-6 inches northwest of 59.
One of the storms along the front produced a tornado over southern Fort Bend County. Another formed over northern Brazoria county near Pearland. Rotation increased as it tracked through SE Houston, Pasadena, Deer Park and Baytown.
Duration and Rates
The heaviest rainfall occurred over portions of west, northwest, and northern Harris County in a 3 to 6 hr period. Several locations in northwest Harris County recorded 1.0-3.0 inches of rainfall in an hour during the late morning hours. Additionally, as the line of storms moved eastward, numerous locations recorded 1.0-2.0 inches of rainfall in 15-45 minutes. That resulted in rapid street flooding over many portions of Harris County during the early to mid afternoon hours.
Total 6-hr rainfall amounts ranged from 3.0-6.0 inches from north of Katy along west/north of FM 1960 into the Humble and Kingwood areas. The highest amount was at John Paul Landing Park in northwest Harris County where 5.48 inches was recorded in 3 hours. Unfortunately, most of this rain fell on grounds that were still wet from heavy rainfalls on January 8 and 9. This maximized runoff into area creeks.
Lindner points out that, “Heavy rainfall and flooding can occur every month of the year in Harris County and there have been other recent heavy rainfall events in January. Compare rainfall duration and intensity in the table below.”
“Cool season” events tend to be short in duration with the majority of the rain occurring in 6 hours or less,” says Lindner.
Interestingly, all of the January flooding events listed above had identical contributing factors: a surface warm front, high moisture levels, and training movement over the same area.
Rainfall amounts for the 1- and 3-hour time periods ranged from 2- to 10-year rains on the Atlas 14 scale. For the most part, channels could accommodate the rainfall. No widespread house flooding occurred although streams came out of their banks at numerous locations and came dangerously close to homes. See below.
Homes surround by floodwaters near West Fork San Jacinto on 1/30/23.
Tornado Impacts
The tornados were a different story, though. As they swept across the southern part of the county at 40 to 60 mph, they produced significant damage.
Lindner said, “Video obtained from the City of Deer Park indicated a tornado heavily shrouded in heavy rainfall with very little if any visibility of a condensation funnel or lofted debris. Unlike tornadoes in the Great Plains, many of the tornados along the US Gulf coast are hidden within heavy rainfall and very difficult to observe.”
Damage assessments as of February 7, from the cities impacted indicate approximately 1,635 single family homes were damaged, 855 multi family units, and 15 mobile homes. The tornados ranged from EF0 to EF2 in intensity. EF2 winds range from 111-135 mph.
Jeff Lindner, Harris County Meteorologist
For a complete listing of rainfall intensities and damage assessments at different locations through the county, see Lindner’s report here. It contains an interesting history of tornados in Harris County.
The pictures below were taken by a retired Kingwood resident, John Knoerzer, who owned a business in one of the hardest hit areas. They illustrate damage in Pasadena at one of his former employee’s home and shop.
Roof and walls torn away by winds. Note sheet metal twisted around tree in upper right. That came from a neighbors home several hundred feet away.Sheet metal from same building shredded the power lines in this 23-second video.
Never Bet Against Mother Nature
Lindner’s report and these images provide powerful reminders of why we should never take flood or wind risk for granted. And why we need to see flood-mitigation projects through to completion.
These were only 5-year storms. But remember. Those exceedance probabilities are like odds on a Las Vegas roulette wheel. I once saw the same number come up six consecutive times!
Don’t bet against Mother Nature. Insurance gives you much better odds.
Posted by Bob Rehak on 2/8/23 with thanks to John Knoerzer for his imagesand Jeff Lindner for his reporting
1989 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2023/02/20230130-DJI_0904.jpg?fit=1200%2C799&ssl=17991200adminadmin2023-02-08 11:53:382023-02-08 12:13:53HCFCD Issues Reports on Late January Flooding, Tornados
Update: 10/28/22 11am: Today’s reports indicate the highest severe storm risk is shifting SW of Houston and offshore. Experts now predict 1-2 inches of rain for the Houston area today.Areas offshore are already getting 2-4 inches per hour.
Tomorrow will likely bring strong thunderstorms. Rainfall rates could exceed the capacity of street drains leading to localized street flooding. And the severe weather may also spin up some tornados, according to Harris County’s meteorologist and the National Weather Service (NWS).
Heavy Rainfall
NWS predicts two to three inches of rain could fall on Friday, as warm, moist air pushing in from the Gulf collides with a cold front pushing in from the northwest. Jeff Lindner, Harris County meteorologist, predicts the worst period for us will be Friday afternoon.
Tornados Possible
The NWS Storm Prediction Center in Norman, Oklahoma, issued this warning for Friday . It shows a marginal risk of severe weather for the entire Houston area and a slightly higher risk for areas south and west of us.
Reasons for Concern
For the weather wonks reading this, Lindner cites an unusual convergence of storm systems at different levels of the atmosphere.
A trough will begin to move eastward toward Texas later today. Surface pressures will begin to fall this afternoon as low pressure develops ahead of the approaching mid-level low. Southeast winds will increase today, letting Gulf moisture quickly return to coastal Texas.
As the mid-level low approaches us, it will meet the northward-moving, moisture-laden warm front moving in from the Gulf.
Severe threats will be highest along the boundary. Tropical moisture will march quickly northward tonight on a 30-knot low level jet. Precipitable waters – the amount of moisture in a column of air – will equal 1.8 inches by Friday morning over much of the region.
As large-scale lift increases over the developing warm sector, showers and thunderstorms will develop from southwest to northeast across the region.
The cold front associated with the mid-level low will sweep west to east across southeast Texas on Friday afternoon, touching off more thunderstorms. The front will slow Friday night, so showers will linger over the area.
Severe Threat:
The surface low approaching from the northwest will meet the warm front coming from the opposite direction along a NW to SE axis on Friday. This warm front will extend from near San Antonio to near Freeport during the day and produce strong to severe thunderstorms. Low-level winds near the warm front will circle back toward the ESE and enhance low-level storm rotation.
Such collisions are notorious for tornado production, according to Lindner. Discrete cells may develop ahead of the line of storms approaching from the west. The location of the greatest severe risk will depend on where the warm front sets up Friday morning. Areas along and south of the front will have the highest risk.
If the warm front moves just a few miles farther north, it will increase risk to the Houston metro area. Kingwood was struck by tornados in a similar setup earlier this year.
Damaging winds will be the main threat. The worst of the storms should be over by 3-5 pm Friday, but lighter rains may linger well into the evening hours.
Heavy Rainfall:
Moisture will deepen Thursday into Friday. By Friday morning, a saturated air mass will be in place over the region. “Strong divergent lift coupled with low-level inflow will increase the potential for heavy rainfall along with cell training from southwest to northeast.”
Lindner describes himself as “aways wary of such setups.” They can help anchor and train convection.
The overall pattern favors supercell formation with both a tornado and heavy rainfall risk.
Jeff Lindner, Harris County Meteorologist
These storms could become significant rainfall producers – if they become sustained along the warm frontal boundary. The good news is that the ground is dry and can handle several inches of rainfall. “However, rainfall rates may exceed localized drainage capacities and result in some street flooding regardless of the dry ground conditions,” says Lindner.
Weekend:
Cloudiness should linger much of Saturday keeping temperatures in the 50’s under northerly winds. South of the cloud line temperatures will warm into the 70’s. Where that line will be Saturday is hard to determine. Clouds should erode Saturday night with mostly clear skies. Sunday will be mild.
Tropics:
The hurricane season has another month to go. It isn’t over yet! The National Hurricane Center now gives an area of low pressure moving WNW across the Caribbean a 50% chance of turning into a tropical depression in the next five days. No one is yet predicting what will happen if it does.
Posted by Bob Rehak on 10/27/22based on information from Jeff Lindner, NWS, and NHC
1885 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/10/Rainfall-10.28.22.png?fit=793%2C561&ssl=1561793adminadmin2022-10-27 14:16:182022-10-28 10:52:03Strong Thunderstorms, Street Flooding, Tornados Possible Tomorrow
Severe Weather, Flash Flood Likelihood Increasing for Monday Afternoon into Early Tuesday
Updated at 7:30 PM:
According to Jeff Lindner, Harris County Meteorologist, a powerful storm will move into Texas over the next 24 hours bringing multiple hazards to the area. The chances of severe weather and heavy rainfall by Monday afternoon and evening continue to increase. They are also expanding over a wider area. Since the original post, Harris County’s Meteorologist, Jeff Lindner has raised concerns about rises on the San Jacinto River West and East Forks to flood stage over the next few days. Rises on other creeks and bayous in Harris County also look likely, especially where we experience cell training and higher rainfall totals. Lindner advises to monitor weather closely on Monday and Monday night.
Outlook tomorrow for severe weather from the NWS Storm Prediction Center.
Higher Likelihood of Severe Weather Including Tornados Starting Monday Afternoon
There were some doubts yesterday about the likelihood for supercells to develop. But as we get closer to the storm’s arrival and certainty increases, supercell formation looks increasingly likely. “All severe modes will be in play including tornadoes, large hail, and damaging winds,” says Lindner. “There could be a few strong tornadoes, especially for locations north of I-10.” Yesterday, the main likelihood was north of SH105.
The National Weather Service Storm Prediction Center has expanded the enhanced risk (3 out of 5) outline to include more of Southeast Texas. The severe threat will begin in the mid-afternoon hours on Monday and continue into the late evening hours.
6-7 Inches, Flash Flooding Possible
While the heaviest rainfall will likely occur over North Texas, the potential for high-precipitation supercells to develop and train across Southeast Texas is increasing for Monday afternoon and evening. As the front slows over Southeast Texas Monday night, Lindner expects the severe threat to gradually shift toward heavy rainfall and possible flash flooding throughout the night.
The greatest threat will generally be along and north of I-10. A slow-moving line of supercells will raise the flash-flood threat. If you get caught under one that’s training across your area as we saw back in January, be prepared.
Lindner has virtually doubled his rainfall predictions since yesterday. Instead of widespread 0.5-2 inches across the area, he now sees widespread 3-4 inches. And whereas yesterday he saw isolated rainfall totals up to 4 inches, today he estimates up to 6-7 inches.
Hourly rainfall rates of 2-3 inches will be possible leading to rapid onset flash flooding over urban areas. Street flooding will be the primary threat, but under corridors of excessive rainfall, significant rises on creeks and bayous will be possible.
Jeff Lindner, Harris County Meteorologist
In an update at 7:30 PM Sunday night, Lindner specifically mentioned the possibility of the East and West Forks of the San Jacinto rising to flood stage if we receive the higher rainfall totals in the forecast.
The NWS Weather Prediction Center has upgraded the area north of the I-10 corridor to a moderate risk for flash flooding.
National Weather Service outlook tomorrow for excessive rainfall.
Monday afternoon and evening will be active over the area. So have multiple ways to receive warnings.Make sure you have fresh batteries in your weather radio and flashlights; it could be a long night.
Putting Forecast in Perspective
To put this in perspective:
The supercells that spawned tornadoes over Kingwood in January dumped approximately 5 inches of rain. I talked with a lady on Facebook this morning whose home was destroyed by a tornado in that storm. She said she received warnings seconds before the tornado struck. She barely had enough time to get to an interior hallway before her home started crumbling around her.
The May 7th, 2019, storm that flooded more than 200 homes in Elm Grove dumped 7 inches of rain. But less than 20% of the floodwater detention capacity on Woodridge Village had been built at that point.
The City announced at 5:15 this afternoon that it will lower Lake Houston by 1 foot starting tonight. A forecast greater than 3 inches triggers the Lake Houston lowering protocol.
How To Get Warnings
NOAA broadcasts warnings on weather radio in a continuous loop during emergencies.
USGS has a web app called Water On the Go that shows water elevations at flood gages wherever you go in Texas.
Harris County Flood Control District’s Storm Center can connect you to a wide variety of preparedness articles and ways to summon help in an emergency.
A number of companies offer good apps for cell phones that offer warnings. I especially like one called Dark Skies that bills itself as “hyper-local” weather. It frequently tells me to the minute when a storm will arrive at my exact location…wherever I am.
You can also find links to dozens of other weather related apps and sites on my Links Page. Check them out before the storm arrives. You never know when a storm will knock out a web site, a cell tower, or power. So be prepared with multiple backups.
Posted by Bob Rehak on 3/20/2022based on input from the NWS, HCFCD and City of Houston
1664 Days since Hurricane Harvey
https://i0.wp.com/reduceflooding.com/wp-content/uploads/2022/03/image001.gif?fit=815%2C555&ssl=1555815adminadmin2022-03-20 16:05:352022-03-20 20:54:09Severe Weather Threat Increasing for Tomorrow, Up to 7″ Now Possible
