Tag Archive for: National Weather Service

Tornado Watch, Flood Warning, Flood Watch In Effect

4:30 PM May 16, 2024 – The National Weather Service has issued a trio of alerts that affect the Lake Houston Area. A tornado watch, flood warning, and flood watch are all simultaneously in effect.

Scene Capture from RadarScope Pro at 4:12PM 5/16/24

Tornado Watch

The three include a tornado watch until 10 PM tonight. The watch includes all counties in the Houston Region and then some. 

AUSTIN               BRAZORIA            BRAZOS
BURLESON             CHAMBERS            COLORADO
FORT BEND            GALVESTON           GRIMES
HARDIN               HARRIS              HOUSTON
JASPER               JEFFERSON           LIBERTY
MADISON              MONTGOMERY          NEWTON
ORANGE               POLK                SAN JACINTO
TRINITY              TYLER               WALKER
WALLER               WASHINGTON          WHARTON

Update: At 5:50 PM, issued a tornado warning for NW Harris, Austin and Waller Counties. They spotted rotation on radar. The warning will expire at 6PM, but it speaks to the severity of these storms.

Flood Warning

The Weather Service has also issued a flood warning for the San Jacinto East Fork. Predicted crests are increasing from minor to moderate levels near FM1485. This could affect people in Harris, Montgomery and Liberty Counties. Some are still cleaning up from the flood two weeks ago.

Flood Watch in Wider Area

Finally, a flood watch has been issued due to excessive rainfall across the region. This one could trigger flooding on other creeks, streams and bayous. The watch area includes:

Houston-Trinity-Madison-Walker-San Jacinto-Polk-Burleson-Brazos-
Washington-Grimes-Montgomery-Northern Liberty-Austin-Waller-
Inland Harris-Southern Liberty-Coastal Harris Counties

This watch is primarily due to excessive rainfall associated with the approaching storm. It could drop 2-4″ across a wide area, with isolated totals up to 6-8″.

Lake Houston is in the area of highest risk – Level 4 – for excessive rainfall.

National Weather Service (See below.)

Flash Flooding Possible

High intensity rains could produce flash flooding that makes driving dangerous.

The ground is already super saturated from previous rains. “There is just nowhere for the water to go,” said Harris County Meteorologist Jeff Lindner.

According to Lindner, “Widespread rainfall amounts of 2-4″ will be likely north of HWY 105. Isolated totals could reach upwards to 6-8 inches. Amounts will decrease toward the south with totals near the coast less than 1 inch. This will virtually be a carbon copy of the last several rainfall events in terms of location and amounts.”

Lake Report

Lake Conroe was releasing 1590 cubic feet per second until the noon hour today. Then, the SJRA stopped releasing water give the Coastal Water Authority a chance to reduce the level of Lake Houston. Lake Houston continues to release water.

Lake Conroe operators hoped they had enough capacity in the Lake to absorb the expected influx of water. But at 4:30PM, the resumed releasing 1587 CFS.

They also announced that they will “pass through storm water and runoff received in the Upper San Jacinto River Basin until Lake Conroe returns to conservation pool.” (201 feet)

Both lakes just returned close to their normal levels from the floods in early May. However, Lake Houston is still a few inches above normal.

Total inflows into Lake Houston are at 6,627 cfs and outflows are at 8,960 cfs. Lake Houston gates have and will remain open until the gate that is stuck partially open is repaired.

Impact on Sedimentation

Most sediment moves during floods. And the West Fork sure has been piling up sediment lately. KSA just completed a sonar survey in River Grove Park where the Kingwood Diversion Ditch enters the West Fork.

Before the last storm, sand had built up at the mouth so that only about two feet of clearance was available for boats. After the last storm, sand is poking up even closer to the surface…and the river is still about a half foot above normal.

Even with water up about a half foot, you can see sand bars lurking just below surface at the River Grove boat launch.

The City of Houston is getting ready to launch a new $34 million dredging program between Kings Point and FM1960.

DRC/Callan Marine mobilizing for new dredging program south of Forest Cove Pool.

Unfortunately, the new City program won’t include the mouth of the Diversion Ditch. KSA will have to hire its own dredger to keep the boat docks open.

KSA’s dredging interval has gone from 8 to 4 to 2 years. It sure seems as though it would be less expensive if we didn’t have West Fork floods flowing through sand pits.

Sand mine on San Jacinto West Fork near Kingwood

For Real-Time Information

To monitor:

Posted by Bob Rehak on 5/16/24 at 4:30 PM

2452 Days since Hurricane Harvey

The thoughts expressed in this post represent opinions on matters of public concern and safety. They are protected by the First Amendment of the US Constitution and the Anti-SLAPP Statute of the Great State of Texas.

National Weather Service Rolling Out New Flood Warning Maps

The National Weather Service (NWS) has launched a nationwide rollout of “experimental” flood forecasting maps. The maps show when, where and how much floodwaters will impact specific areas up to five days in advance.

NWS’s new experimental flood inundation maps help communicate the timing and magnitude of high water events by showing modeled inundated areas in blue overlay. Emergency managers may use these services to preposition resources, secure critical infrastructure and recommend evacuations and evacuation routes.

System Already Rolled Out to Houston Area

NWS has already rolled out the system for Houston and East Texas with other parts of the county to follow.

The new system should enable emergency managers to see how predicted rainfall could impact structures, communities and people.

Until now, the best NWS could do was issue a flood watch or warning for communities. But the new maps will show how far floodwaters could spread in a community. That will help people better prepare for floods and evacuate from them. For instance, it will reportedly show when roads will be cut off by rising waters.

However, the new maps can’t yet forecast urban flash flooding related to lack of storm sewer capacity.

Near Real-Time View for Emergency Managers

NWS announced the new experimental flood maps on September 26, 2023. “These new services complement and support the issuance of flood watches and warnings by providing near-real-time, high-resolution, street-level visualizations showing where, when, and how much flood waters are forecast.”

The descriptions conjure up images of floodplain maps. But they show expected flooding from approaching storms – not just the extent of flooding in a hypothetical 100-year event.

David Vallee, director, Service Innovation and Partnership Division, NOAA’s National Water Center said, “These services will dramatically improve our ability to provide impact-based decision support services to our partners so they can preposition people and resources ahead of flood events.”

Three New Tools

Three new near-real-time services will help improve flood impact information. They include:

For more on how the system will work, see this story map based on Houston and Hurricane Harvey. Imagine how many lives could have been saved if we had this system then!

Posted by Bob Rehak on 10/16/23 based on information from NWS

2239 Days since Hurricane Harvey

Is Precipitation Increasing with Temperature?

Data provided by the National Weather Service (NWS) shows that precipitation appears to be increasing with temperature in Houston and Harris County. A reader recently asked whether there was a correlation. The hypothesis: in this climate, if temperature increases, then so will evaporation and rainfall. Eighty to 130 years worth of data at different locations show both variables trending up. But most scientists would consider the coefficient of correlation weak to non-existent.

Behind the Theory

The theory is plausible from several perspectives.

  • Warm air holds more moisture than cool air. Warm air also rises. As it cools at higher altitudes, precipitation forms. Think “afternoon thunderstorms on hot summer days.”
  • Precipitation also forms when warm and cool fronts collide.
  • It often forms when warm moisture-laden air streams in from the Gulf.
  • Hurricanes form in the hottest parts of the year.
Distribution of hurricanes by month during the last 100 years.

But the question concerned correlation, not causation.

Other outside factors could reduce precipitation, such as droughts triggered by changes in Pacific Ocean currents. Those who remember the drought from 2011 to 2014 may also remember how hot it was.

But looking at 80 to 130 years of data highlights long-term climate trends. That “evens out” the influence of individual events.

Qualifiers

NWS plotted all available historical data for precipitation and temperature on line graphs and then superimposed trend lines. The graphs show official data from two sources: Houston-Hobby Airport and the “City of Houston.”

I put City of Houston in quotes because the the official City-of-Houston data is currently collected at Bush Intercontinental Airport. But the location has bounced around. So the “City” isn’t one location, but many:

  • Cotton Station (July 1881 – September 1909)
  • Stewart Building at Preston and Fannin (September 1909 – February 1926)
  • Shell Building at Texas and Fannin (March 1926 – August 1938)
  • Federal Building at Franklin and Fannin (August 1938 – May 1969)
  • Intercontinental Airport (June 1969 – Present)

We have less data for Houston-Hobby because Hobby Airport didn’t exist until 1927. That’s when someone turned a 600-acre pasture into a landing field. The City of Houston purchased the field in 1937 and expanded it.

With those qualifiers, see the charts below. Both temperature and rainfall vary from year to year. But rainfall shows extreme variance. Regardless, in all four graphs the trend lines slowly increase.

Houston-Hobby Airport

Mean temps at Hobby increased from 69 to 73 degrees – a 4 degree increase between 1931 and 2022.
During roughly the same time period, precipitation increased approximately 9 inches from about 48 to 57 inches. Also notice the extreme range – from less than 30 to more than 80 inches.

City of Houston Data

The City of Houston data covers a wider time period. Within that, the location varied as noted above. The big jump was from downtown to Bush Intercontinental Airport in 1969. Generally speaking, as you go farther north from the coast, precipitation decreases. But the difference is less than an inch. Atlas 14 shows that a 100-year, 24-hour storm is 17.6 inches at Hobby, 17 inches downtown, and 16.9 inches at Intercontinental.

City data indicates mean temp has increased roughly 4 degrees in last 120 years.
During roughly the same years, precipitation increased about 5-6 inches. Here, the range was even more extreme. From less than 20 inches to 80 – a 4X difference.

So the change in where the City collects official data actually worked against the hypothesis. And it shows.

Summary of Trend Differences

Summarizing the key differences:

  • As the temp trend line increased 4 degrees at Hobby, precipitation increased 9 inches.
  • As temp increased 4 degrees at various City locations, precipitation increased 6 inches.

Low Coefficient of Correlation

Jimmy Fowler of the National Weather Service’s Houston/Galveston office calculated the coefficients of correlation between the two series of data at each location.

For Hobby, the coefficient of correlation is only .03. The City’s is slightly higher at .11.

Jimmy Fowler, Meteorologist, National Weather Service

For those who didn’t study statistics in college, the coefficient of correlation tells you how much one variable changes in response to another.

  • A perfect positive correlation is 1.0. Example: population growth and food consumption.
  • A perfect negative correlation is -1. Example: hours worked and free time.

In both cases, one unit of change in the first variable accounts for an equal unit of change in the second. But most correlations fall between the two extremes with different degrees of strength.

The chart below indicates how scientists would characterize correlation coefficients of .03 and .11. Both are considered “very weak” or having “no association.”

correlation strength
By Wayne W. LaMorte, MD, PhD, MPH, from the Boston University School of Public Health website.

Fit of Trend Lines to Data

So, if the trends are all up, why is the co-efficient of correlation so low? Part of the answer has to do with those R2 (R squared) values you see at the bottom of the charts. They show the data doesn’t conform to the trend lines very well. Temperature fits moderately well. But precipitation shows extreme variance.

A perfect fit (1.0) would show all the data points on the line. As a rule of thumb, 0.8 (80%) or higher is considered a good fit. But the R2 values in these trend lines range from 0.03 to 0.5.

Conclusion

You can read into this data whatever you want depending on your point of view. Climate change advocates might see proof in the consistent slope of the trend lines that warming temperatures and more precipitation are related. A deeper dig into the data reveals the correlation is weak at best and possibly non-existent. Other factors may be at play and influencing the data.

To demonstrate causation, you need to show a directional relationship with no alternative explanations. But with weather, you have a multitude of alternative explanations.

Remember that weather is global and that we looked only at Houston in this instance.

However, a friend who traded weather-related derivatives before retirement tracked hundreds of temperature sites. He found they all trended warmer over time. But he believed the variance resulted primarily from changes in surrounding ground cover, i.e., replacement of natural ground cover with concrete – also known as the urban heat island effect.

He also tracked variance to changes in measurement locations (as with Houston).

Finally, remember that some of the hottest and coldest places on earth get very little precipitation. The Sahara and the North and South Poles are all considered deserts based of the amount of precipitation they get.

Net: I find the similarities in the graphs interesting enough to keep digging. As my friend suggested, it would be interesting to find the coefficient of correlation between population growth and temperature change. I won’t leap to any generalizations at this point.

Posted by Bob Rehak on 12/30/2022 with thanks to Jeff Lindner, Harris County Meteorologist and Jimmy Fowler of the National Weather Service.

1949 Days since Hurricane Harvey

NWS Says Chance of San Jacinto River Flooding in Next Three Months is Minor

The National Weather Service (NWS) predicts only minor flood risk for both the West and East Forks of the San Jacinto through the end of May. That’s the good news.

NWS predicts only minor long range flood risk for the East (38.85%) and West Forks (26.22%) of the San Jacinto.

Drought Conditions Expanding Across Texas

But there is a downside: potential drought.

The reason for the low risk has to do with a below-average rainfall pattern across much of Texas. The Texas Water Development board posted two stories in the Texas Water Newsroom last week about the potential for drought. Large parts of the state are already severely behind on rainfall for the year and the pattern is expected to continue through May when weakening La Niña conditions could return us to normal.

Source: Texas Water Development Board as of end of February 2021.

The map above shows that most of the Houston area has received about 90% of expected rainfall year to date. But large parts of the state have received less than 20%. TWDB predicts those dark areas on the map will expand at least through May. At that point, TWDB predicts only the extreme eastern part of the state will not be in some kind of drought condition.

At the end of February, drought covered just over half the state, according to the TWDB. Statewide storage in our water-supply reservoirs is at 82 percent of capacity, about three and a half percentage points less than normal for this time of year. 

Drought Relief Could Come as La Niña Fades

Says Dr. Mark Wentzel, Texas Water Development Board Hydrologist, “The National Weather Service anticipates drought expansion across all but the eastern edge of the state by the end of May. Looking a little farther out there is some good news. La Niña conditions, that are at least partially responsible for drought in Texas, are expected to dissipate after April.”

So, the river flooding outlook could be very different by Hurricane season this year.

Did snow in February not help? Not really. Wentzel points out that snow is mostly air. It takes up to a foot of snow to equal and inch of rain.

Posted by Bob Rehak on 3/14/2021

1293 Days since Hurricane Harvey

Beta Moving Ashore Today Then Likely Tracking Slightly South of Houston

As of 10:00 a.m. Monday morning, the National Hurricane Center (NHC) still shows the center of Tropical Storm Beta located offshore. The latest forecasts from the NHC predict that Beta will move onshore near Matagorda Bay, then move up the coastline toward League City.

The NHC also advises that the storm has picked up speed. Yesterday, they estimated 3 mph; today 7 mph.

No one seems to predict that the storm will intensify before landfall.

“Dry air continues to work into and wrap around the large wind field of Beta yielding the disorganized precipitation field with the system.”

Jeff Lindner, Harris County Meteorologist
National Weather Service radar Image of Beta as of 10:04 am Monday 9/21/20.
Lake Houston Area is the blue dot in the center of the swirl. Red line is predicted path of Beta. Source: Weather Live.

Main Threat: Storm Surge

At this time, Beta’s main threat is to the coastline through storm surge. “Tides are currently running 4.0-4.5 feet in Clear Lake and across coastal sections of Harris County with several sites near the Gulf beaches running 4.0-4.5 feet. Coastal flooding is ongoing and will continue for much of the day. Several roadways are underwater along the coast and around Galveston Bay,” says Lindner.

Lindner continues, “As Beta makes landfall along the middle Texas coast later today, the storm will begin to slow and then turn ENE toward the upper TX coast. It will slowly weaken along the way. This track will keep onshore flow along the upper Texas coast tonight and Tuesday. Tides will remain high into the high tide tonight. Impacts along the coast will continue through the day and into tonight and likely Tuesday.”

Wind Forecast

The most likely arrival time of tropical storm force winds, if we get them, is later tonight.

Tropical storm force winds already cover a large part of the mid-Texas coast.

The storm will weaken as it moves toward the Houston Area and turn into a tropical depression. The further north you live from the coastline, the less intense winds will be.

Depending on where you live in Houston, you have a 30% to 100% chance of experiencing topical storm force winds. The Lake Houston Area is on the low end of that range. The National Weather Service predicts that the Lake Houston Area has a chance of seeing 39-57 mph winds. But Spaces City Weather advises that Beta is “not a significant wind threat.”

However, note that tropical-storm-force winds currently extend outward up to 175 miles (280 km) from the center of the storm.

Galveston has reported sustained winds of 39 mph and a gust of 43 mph during the past couple of hours.

Rainfall

Dry air has worked into the circulation of Beta, according to Lindner. “This has resulted in a more disorganized and scattered rainfall pattern. However, the system is still capable of heavy rainfall especially near the center later today and in bending structures east of the center for the next 48 hours.”

Models show several banding features developing during the next 48 hours over SE TX, But little consensus exists on where the heaviest rainfall totals may be.

Lindner advises that, “Given that much of the area will reside on the eastern side of a the tropical system, we should keep some level of concern of heavy rainfall and flooding in place through the next 48 hours.”

Lindner predicts that widespread rainfall amounts of 4-8 inches will be possible for areas along and south of I-10 with isolated totals of 10-12 inches under any training feeder bands. Totals to the north of I-10 will likely average 3-5 inches with isolated totals of 6-7 inches. 

However, the NHC predicts slightly less rain. See the map below.

As long as the rainfall spreads out over the next 48 hours, most of the creeks and bayous can handle the expected rainfall amounts, Lindner says. But should any training develop, flash flooding would be possible. 

Watches and Warnings in Effect

A Storm Surge Warning is in effect for Port Aransas, Texas to Rockefeller Wildlife Refuge, Louisiana. That includes Copano Bay, Aransas Bay, San Antonio Bay, Matagorda Bay, Galveston Bay, Sabine Lake, and Lake Calcasieu.

A Tropical Storm Warning is in effect for Port Aransas Texas to Morgan City Louisiana. That includes the Lake Houston Area.

National Hurricane Center

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

Lindner, the NHC and NWS all warn that tornadoes remain a threat with this storm. Especially, tonight and Tuesday.

Track

Yesterday, models predicted that Beta would track up US59 toward the Humble/Kingwood Area. However, today, forecasters think the storm will track closer to the coast. They put it on a line toward League City.

Wind shear will keep Beta’s track close to the coastline, but it will also affect the cyclone’s intensity along with land interaction. The closer the cyclone stays near the Gulf of Mexico, the more likely that bands of convection containing tropical-storm-force winds will continue to roll onshore the Texas coast through 36-48 hours.

Summary

Flash, urban, and isolated minor river flooding is possible, but the danger is “slight.”

National Hurricane Center

Net: Beta is still a threat. But it may be less of one than yesterday. That’s because of the dry air folding into the system and wind sheer which seem to be weakening it somewhat. Be hopeful, but cautious. Expect several inches of rain and high winds in the next two days with both tapering off Wednesday.

Posted by Bob Rehak on 9/21/2020 at noon based on data from NHC, NWS, Jeff Lindner, Space City Weather and Weather Live

1119 Days after Hurricane Harvey and 368 since Imelda

How Close Was Laura?

After a week of worry! After adrenaline-fueled prep for two back-to-back hurricanes that could have wreaked havoc on Houston…I woke up refreshed this morning, walked to my weather window, and saw…nothing unusual. What happened? I checked my weather gauge. It read 0.00 inches of rain. Max winds since midnight: 3 mph.

It would appear the Houston Area dodged Laura’s silver bullet. But why? According to Harris County Meteorologist, Jeff Linder, two things spared us the wrath of Laura. First, Laura shifted slightly east. Second, as Laura intensified, the wind field pulled in tighter. That diminished feeder bands on the western side of the storm.

How Close Laura Came

Here are some radar and satellite images that show how close the storm came.

From Weather Live App at 5:55 am Thursday 8/27/2020
From the National Hurricane Center at 5:56 am. Houston is the bright spot on the SW side of the swirl.
From the National Weather Service at 1:53 CDT as Laura came ashore.
From Lake Charles Louisiana radar at 12:46 am CDT. (This and following images from RadarScope Pro app.)

The shot above and the radar loop below show dramatically how the storm shifted east last night. The National Hurricane Center had predicted eye of the storm to move up the Sabine River near Port Arthur, about 40 miles west.

Radar Loop showing Laura coming onshore that started at 11:28pm 8/26/2020.
Little Rock, Arkansas radar at 5:41 am CDT as Laura approaches

6 A.M. Update from NHC

At this instant, Laura has diminished to a Cat 2 storm. An update issued by the NHC at 6:00 a.m. says,

  • HURRICANE CONDITIONS SPREADING FARTHER INLAND ACROSS SOUTHWESTERN LOUISIANA…
  • CATASTROPHIC STORM SURGE, HURRICANE FORCE WINDS, AND FLASH FLOODING WILL CONTINUE THIS MORNING…
  • Fort Polk, Louisiana recently reported a sustained wind of 45 mph (72 km/h) and a wind gust of 70 mph (113 km/h). SUMMARY OF 600 AM CDT…1100 UTC…
INFORMATION
  • LOCATION…30.9N 93.3W ABOUT 55 MI…90 KM N OF LAKE CHARLES LOUISIANA
  • MAXIMUM SUSTAINED WINDS…105 MPH…170 KM/H
  • PRESENT MOVEMENT…N OR 355 DEGREES AT 15 MPH…24 KM/H
  • MINIMUM CENTRAL PRESSURE…964 MB…28.47 INCHES

Hurricane Guilt

After Hurricane Rita, which dodged Houston like Laura, I coined a term called “hurricane guilt.” It’s that feeling of elation you get when you realize the storm missed you…followed closely by the realization that it destroyed innocent lives elsewhere.

That’s what I feel right now. As I write this, the sun is rising and birds are singing. Soon images of Laura’s destruction will start to pour in. Only then will we know how lucky we were.

Posted by Bob Rehak at 6:45 am on 8/27/2020 based on information from NWS, NHC, RadarScope, and Jeff Lindner, Harris County Meteorologist

1094 Days since Hurricane Harvey

Impact Corridor of Hurricanes Much Wider than Cone of Uncertainty

Many people mistake the cone of uncertainty associated with a hurricane as the width of a storm. It’s not. It merely shows likely paths the hurricane’s eye could take as it comes ashore. There’s an equal probability of any path within the cone. Cones expand with more distant projections because uncertainty increases. But as forecasters always warn us, the impact of a major hurricane extends far beyond the cone of uncertainty.

Difference Visualized

Compare these two pictures to fully understand the difference.

Cone of uncertainty for Laura as of Wed. morning, 8/26/2020 at 10 a.m. CDT.
Satellite image of Laura taken at about the same time the cone image above was produced.

I have arbitrarily assigned the term “impact corridor” to the area between the two lines to help describe the difference. (No one uses this term but me, although they probably should.)

Of course, as you go further from the center of the storm, the intensity decreases and so do negative impacts.

Currently (12:30 pm CDT, 8/26/2020), hurricane-force winds extend outward up to 70 miles from the center and tropical-storm-force winds extend outward up to 175 miles. That’s 350 miles across!

Interesting Facts About Hurricanes

As you ride this one out with your children or grandchildren, make it a learning experience. Here are some interesting facts about hurricanes taken from Weather.gov.

  • Each year, an average of ten tropical storms develop over the Atlantic Ocean, Carribean Sea, and Gulf of Mexico. Many of these remain over the ocean. Six of these storms become hurricanes each year. In an average 3-year period, roughly five hurricanes strike the United States coastline, killing approximately 50 to 100 people anywhere from Texas to Maine. Of these, two are typically major hurricanes (winds greater than 110 mph).
  • Typical hurricanes are about 300 miles wide although they can vary considerably in size.
  • The eye at a hurricane’s center is a relatively calm, clear area approximately 20-40 miles across.
  • The eyewall surrounding the eye is composed of dense clouds that contain the highest winds in the storm.
  • The storm’s outer rainbands (often with hurricane or tropical storm-force winds) are made up of dense bands of thunderstorms ranging from a few miles to tens of miles wide and 50 to 300 miles long.
  • Hurricane-force winds can extend outward to about 25 miles in a small hurricane and to more than 150 miles for a large one. Tropical storm-force winds can stretch out as far as 300 miles from center of a large hurricane.
  • Frequently, the right side of a hurricane is the most dangerous in terms of storm surge, winds, and tornadoes.
  • A hurricane’s speed and path depend on complex ocean and atmospheric interactions, including the presence or absence of other weather patterns. This complexity of the flow makes it very difficult to predict the speed and direction of a hurricane.
  • Do not focus on the eye or the track. Hurricanes are immense systems that can move in complex patterns that are difficult to predict. Be prepared for changes in size, intensity, speed and direction.

What Hurricanes Need to Grow

Weather.gov lists six widely accepted conditions for hurricane development:

1. The first condition is that ocean waters must be above 79 degrees Fahrenheit. Below this threshold temperature, hurricanes will not form or will weaken rapidly. Ocean temperatures in the tropics routinely surpass this threshold.

2. The second ingredient is the Coriolis Force. Without the spin of the earth and the resulting Coriolis force, hurricanes would not form. Coriolis force causes a counterclockwise spin to low pressure systems, such as hurricanes, in the Northern Hemisphere and a clockwise spin to low pressure in the Southern Hemisphere.

3. The third ingredient is that of a saturated lapse rate gradient near the center of rotation of the storm. A saturated lapse rate insures latent heat will be released at a maximum rate. Hurricanes are warm core storms. The heat hurricanes generate is from the condensation of water vapor as it convectively rises around the eye wall. The lapse rate must be unstable around the eyewall to insure rising parcels of air will continue to rise and condense water vapor.

4. The fourth and one of the most important ingredients is that of a low vertical wind shear, especially in the upper level of the atmosphere. Wind shear is a change in wind speed with height. Strong upper level winds destroy the storms structure by displacing the warm temperatures above the eye and limiting the vertical accent of air parcels. Hurricanes will not form when the upper level winds are too strong.

5. The fifth ingredient is high relative humidity values from the surface to the mid levels of the atmosphere. Dry air in the mid levels of the atmosphere impedes hurricane development in two ways. First, dry air causes evaporation of liquid water. Since evaporation is a cooling process, it reduces the warm core structure of the hurricane and limits vertical development of convection. Second, dry air in the mid levels can create what is known as a trade wind inversion. This inversion is similar to sinking air in a high pressure system. The trade wind inversion produces a layer of warm temperatures and dryness in the mid levels of the atmosphere due to the sinking and adiabatic warming of the mid level air. This inhibits deep convection and produces a stable lapse rate.

6. The sixth ingredient is that of a tropical wave. Often hurricanes in the Atlantic begin as a thunderstorm complex that moves off the coast of Africa. It becomes what is known as a midtropospheric wave. If this wave encounters favorable conditions such as stated in the first five ingredients, it will amplify and evolve into a tropical storm or hurricane. Hurricanes in the East Pacific can develop by a midtropospheric wave or by what is known as a monsoonal trough.

Posted by Bob Rehak on 8/26/2020 based on data from Weather.gov.

1093 Days since Hurricane Harvey

NWS Predicts Local Impacts to Lake Houston Area from Hurricane Laura

The National Weather Service (NWS) Southern Region has produced an interactive map that lets users click on their location and produce estimates of danger from Hurricane Laura.

For the Lake Houston Area, NWS predicts potential for moderate flooding rain

Click one a location near you and review the threat potential.

Potential Impacts Include:

  • Moderate rainfall flooding may prompt several evacuations and rescues.
  • Rivers and tributaries may quickly become swollen with swifter currents and overspill their banks in a few places, especially in usually vulnerable spots. Small streams, creeks, canals, and ditches overflow.
  • Flood waters can enter some structures or weaken foundations. Several places may experience expanded areas of rapid inundation at underpasses, low-lying spots, and poor drainage areas. Some streets and parking lots take on moving water as storm drains and retention ponds overflow. Driving conditions become hazardous. Some road and bridge closures.

For Lake Houston Area, NWS Predicts Winds from 58 to 73 mph

Potential wind threats from Laura and protective actions for people in the Lake Houston Area

Potential Impacts Include:

  • Some damage to roofing and siding materials, along with damage to porches, awnings, carports, and sheds. A few buildings experiencing window, door, and garage door failures. Mobile homes damaged, especially if unanchored. Unsecured lightweight objects become dangerous projectiles.
  • Several large trees snapped or uprooted, but with greater numbers in places where trees are shallow rooted. Several fences and roadway signs blown over.
  • Some roads impassable from large debris, and more within urban or heavily wooded places. A few bridges, causeways, and access routes impassable.
  • Scattered power and communications outages, but more prevalent in areas with above ground lines.

…TROPICAL STORM WARNING REMAINS IN EFFECT…

West of Lake Houston, the threat level decreases. Between Dayton and Liberty, it increases.

For those closer to the coast, the map also includes storm surge warnings. Also check out the estimates of tornado threats.

The latest satellite images show Laura just off the coast. The storm is moving north at about 15 miles per hour.

Hurricane Laura as of 11 am 8/26/2020

No Lake Conroe Release Anticipated Before Storm

In other hurricane related news, the SJRA just issued a press release stating that:

“SJRA is operating under standard protocols for a severe weather event and will be onsite at Lake Conroe throughout the night and into Thursday. 
Lake Conroe remains about 15 inches low, and based on the current forecast, no reservoir releases are expected.“

Posted by Bob Rehak on 8/26/2020 at 11:00 a.m. based on estimates from the National Weather Service.

1093 Days since Hurricane Harvey

As of 7 a.m., Laura Predicted to Make Landfall at Sabine Pass as Cat 4 Hurricane

This update on Hurricane Laura is based on information from Harris County Meteorologist Jeff Lindner and the National Hurricane Center based on their 4 a.m. and 7 a.m. updates on Wednesday 8/26/2020.

Laura rapidly strengthening…now a 115 mph Category 3 hurricane, predicted to reach Cat 4.

Extremely dangerous hurricane will make landfall near Sabine Pass tonight with catastrophic impacts.

All preparations must be completed by 6:00 p.m. this evening.

Conditions will begin to deteriorate late this afternoon and evening over the region.

Rainfall predictions for the Lake Houston Area increased overnight. We could now receive up to six inches.

The Lake Houston Area now has a 60-80% chance of experiencing topical-storm-force winds from Laura.
Tropical-storm-force winds could arrive as early as mid-afternoon.
The most likely time, however, for the arrival of tropical-storm-force winds is later this evening.

Discussion 

Laura became a large and dangerous hurricane overnight with expansion of the wind field. USAF missions indicate the central pressure continues to fall. Winds are increasing. And Laura has experienced a 40 knot increase in winds in the last 24 hours. (A knot = 1.15 mph.) The eye of the hurricane is starting to clear out. Further rapid intensification is likely today.

The cone of uncertainty now shows Houston will NOT experience a direct hit from the storm, but we will still feel it. Effects from the Laura extend well outward from the center.
Track: 

The center of Laura should cross the coast near Sabine Pass, TX, near the Texas/Louisiana Border. Models have tightly clustered just either side of the state line. There is high confidence that Laura will make landfall in the areas between Sea Rim State Park and Cameron LA early Thursday morning. The hurricane should move rapidly northward, up the Sabine River Valley on Thursday. 

Given the fast forward motion, significant wind impacts will extend well inland along the track of Laura with wind damage likely extending 100-200 miles inland over eastern Texas and western Louisiana.

Intensity: 

Laura will pass over warm Gulf waters today and upper air conditions that favor intensification through landfall. The National Hurricane Center forecasts a category 4, 130 mph hurricane at landfall.

Hurricane force winds extend outward 70 miles from the center and tropical storm force winds 175 miles.

Wind damage and storm surge impacts will extend well beyond the center.

Jeff Lindner, Harris County meteorologist

Impacts

Storm Surge: 

Expect a catastrophic storm surge event over extreme SE TX and much of coastal Louisiana.

Strong north winds tonight may drive water levels along the north side of Galveston Island and Bolivar to elevated levels and water levels in the NW part of Galveston Bay may fall well below normal.

The following values are above ground level:

Galveston Bay: 1-3 ft

Bolivar: 2-5 ft

High Island to Sea Rim State Park: 6-9 ft

Sea Rim State Park to Intracoastal City (Including Beaumont and Lake Charles): 10-15 ft.

Large destructive waves will accompany storm surge.

Winds: 

West of I-45: 30-40mph

East of I-45: 45-55mph

Chambers, Liberty, Polk Counties: 50-65mph

Jefferson, Orange Counties and Lake Charles: 110-120mph

Higher gusts will occur in squalls. 

Hurricane-force winds currently extend outward up to 70 miles from the center and tropical-storm- force winds extend outward up to 175 miles.

The Harris County line is 75 miles from Sabine Pass; Lake Houston 80 miles.

Rainfall: 

West of I-45: 1-2 inches

East of I-45: 2-6 inches, isolated totals up to 8 inches.

Sabine River Valley: 8-12 inches

Overnight, rainfall predictions for the Lake Houston Area increased 2 inches. The six inches now predicted roughly equals the amount of rain the Lake Houston Area received on May 7th last year. Elm Grove residents: Please note: the volume of detention ponds now on Woodridge Village should be enough to protect you unless there is a design flaw.

The main rainfall threat comes from rapid, intense rains which can cause street flooding.

Actions

Complete all preparations by 6:00 pm this evening. Earlier the better.

If in evacuation areas, evacuate immediately…especially in the Beaumont and Lake Charles area.

Lake Report

Lake Houston as of 6:30 a.m. was at 41.17 feet (full pool 42.4). The Coastal Water Authority will continue releasing water from Lake Houston until it reaches 41 feet.

Lake Conroe is not releasing water and stands at 199.72 feet (full pool is 201).

For More Up-to-the-Minute Information

For the most up-to-date rainfall totals and water levels in bayous, creeks, and rivers, visit www.harriscountyfws.org. This system relies on a network of gage stations that have been strategically placed throughout Harris and surrounding counties.

Also visit the National Hurricane Center and the National Weather Service.

Posted by Bob Rehak at 7:12 a.m. on 8/26/2020 based on input from the National Hurricane Center and Jeff Lindner, Harris County Meteorologist.

1093 Days after Hurricane Harvey

Laura Intensifying into Major Hurricane; Prepare for Big Winds, Power Outages

These warnings were just issued by Jeff Lindner, Harris County Meteorologist, the National Hurricane Center, and City of Houston:

Hurricane warnings issued from San Luis Pass into Louisiana.

Landfall of a devastating hurricane likely between Galveston Bay and Sabine Pass tomorrow night.

Rush to complete preparations to protect life and property.

Heed all evacuation recommendations.

Discussion

Laura – now a hurricane with sustained winds of 75mph – is continuing to intensify. The hurricane will likely rapidly intensify over the next 24-36 hours, right up to landfall along the upper TX coast. The National Hurricane Center predicts Laura will become a major hurricane with sustained winds over 110 mph by tomorrow night or early Thursday morning when it makes landfall somewhere between Galveston Bay and Sabine Pass.

Track: 

Everyone should be planning for the landfall of a very serious hurricane between Galveston Bay and Sabine Pass on the Louisiana border. Additional shifts in the track are possible that could bring the core of Laura into Galveston Bay and Harris/Galveston Counties.

The large wind field will result in strong winds likely 100-150 miles inland across east Texas.

Prepare for power outages extending well inland along with significant wind damage and extended outages.  

Intensity:

Prepare for the impact of a major hurricane (cat 3 or higher). Once the inner core of Laura forms, significant intensification is likely, and conditions look very favorable for intensification. 

Tropical Storm force winds will begin along the coast at around 8:00 pm Wednesday evening.

Advice from City, Lake Status

“Rainfall amounts in the Lake Houston Watershed over the next six days are expected to be 2 – 4 inches with isolated accumulation of 6 inches possible,” said Dave Martin. “Currently, the Lake Houston Watershed is dry and the projected impact to our area will be to our east with the largest possible impact expected along the East Fork of the San Jacinto River. Lake Houston is already down one foot from normal pool with the possibility of being lowered additionally, if necessary. Please make sure all property along the shoreline is secured in the event additional lowering is ordered.”

“Regardless of where this storm lands,” said Martin, “it is important all residents prepare themselves and have a plan. Hurricane Laura will likely be similar to Ike with severe wind impacts and power outages. The City of Houston has prepared resources to help you get ready for upcoming disasters and make sure you are prepared for this one. Please visit www.readyhoustontx.gov to learn more.

Actions

  • Prepare for the landfall of a major hurricane along the SE TX coast
  • Bring in anything in your yard, such as lawn furniture, that could become airborne.
  • All preparations will be to be competed by 6:00 p.m. Wednesday evening.
  • Heed all evacuation orders. 

For hurricane preparation tips from the National Weather Service, click here.

Posted by Bob Rehak on 8/24/2020 based on input from the National Hurricane Center and Jeff Lindner, Harris County Meteorologist.

1091 Days after Hurricane Harvey