May 21, 2019

Oklahoma Is Extremely Lucky That Monday's Severe Weather Didn't Live Up To Its Potential



The parameters existed on Monday for an intense tornado outbreak on the southern Plains had thunderstorms managed to develop in the warm sector. That didn't happen. Even though there was plenty of severe weather from western Texas to southwestern Missouri, it's safe to say that Oklahoma got extremely lucky compared to what could have been.

It's admittedly a little tough to say Oklahoma got "lucky" when there were still damaging tornadoes there and in Texas—some of which likely rated as a significant EF-2 or stronger—and major flash flooding across Oklahoma and parts of Kansas and Missouri. But the overall situation wasn't as bad as it could have been given the potential that existed. Something—possibly unexpected subsidence in the mid-levels of the atmosphere or rising air not rising fast enough near the surface—prevented thunderstorms from blowing up in the most favorable area for tornadoes. That was truly the best outcome given how dire the situation looked going into Monday afternoon.



The above tweet from NOAA's Hazardous Weather Testbed shows the significant tornado parameter on May 31, 2013—the day of the 2.6-mile wide tornado in El Reno, Oklahoma—compared to what we saw on Monday, when the parameter was twice as high as it was on that awful day six years ago. The environment over the region on Monday was about as favorable for tornadoes as it gets. The atmosphere was ready to spin anything that managed to root itself in central Oklahoma, but nothing really got going until later on when approaching storms had coalesced and the tornado threat began to wane.

The weather doesn't suddenly veer from a predetermined path. Thunderstorms were never going to develop in central Oklahoma when conditions were most favorable for tornadoes. We just didn't know that ahead of time, and that's a failure. The search for answers as to why that wasn't detected and accounted for ahead of time—and how to catch it the next time—will come through plenty of research in the coming months and years. Meteorologists have gotten really good at tornado forecasting over the years, but there's still a lot left to learn.

Rare and memorable severe weather outbreaks are rare and memorable for a reason. It's really hard for all the ingredients to come together at the same time to produce a high-end tornado outbreak. I made note of that going into the day on Monday:

It appears the environment will be capable of supporting a high-end severe weather outbreak. It's hard for big severe weather outbreaks to occur. Lots of things have to go right and it's easy for storms to morph into a sloppy mess on a day like this. Even if the storms on Monday don't reach maximum capacity—and many likely won't!—one storm breaking through to produce one bad tornado is still a big deal.

I won't pretend to have had any special intuition that made me include that blurb. I thought it would be ugly just the same as everyone else. But we've seen lots of seemingly high-end severe weather outbreaks in recent years turn into a sloppy mess. Sloppy clusters of storms and the lack of a sufficient trigger in the warm sector mostly stifled the extreme tornado threat away from the dry line farther west. The setup still produced plenty of tornadoes in parts of the Texas panhandle and western Oklahoma, but it wasn't nearly as bad as it could have been given the dynamics in place.

The most important part of a forecast is getting it right. Messaging is a close second, though—and I'm not convinced (at least not yet) that the high risk yesterday was unwarranted given the extreme parameters in place had a storm been able to form and take advantage of that kind of environment. Can you imagine if it had gone the other way and supercells had blown up around the Oklahoma City area after forecasts downplayed the threat?

Sounding the alarm for a big day that doesn't quite pan out will hurt trust in weather forecasting at least a little bit. You know how averse I am to hype, and yesterday will probably hurt some readers' trust in me. The atmosphere pointed a loaded gun at central Oklahoma on Monday. We're very lucky nothing pulled the trigger.

Thankfully, instead of mourning, today we have an internet full of part-defensive and part-introspective weather folks, storm chasers ticked they didn't see the best day of their lives, residents peeved that they worried over nothing, and officials left explaining why they cancelled classes and moved armies (well, just some planes) based on a potential that went unfulfilled.

It's a good thing that people took the threat seriously. Every live shot of Oklahoma City on television yesterday showed the streets virtually empty for most of the day. Yesterday's response shows that people really do trust the forecasts and they really do prepare when things get scary. I hope they still choose to take action the next time.


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May 20, 2019

Subtropical Storm Forms Near Bermuda, 2019 Hurricane Season Starts in May. (Again.)

Subtropical Storm Andrea formed southwest of Bermuda on Monday. The appearance of a named storm in the Atlantic means this basin's hurricane season has started before June 1 for the seventh time in the last decade. Andrea will be weak and short-lived, posing no threat to land.


This storm forming while everyone is paying attention to the severe weather over the Plains is the atmospheric equivalent of a Friday night news dump. Most people will never know it existed, and the rest will forget about it soon enough. Subtropical Storm Andrea will probably dissipate by early Wednesday morning without affecting land. The storm's remnants could bring showers to Bermuda by the middle of the week, but that's about it as far as impacts are concerned.

A subtropical storm is a low-pressure system that shares both tropical and extratropical characteristics. It's tropical-like. It forms and acts like a tropical cyclone, and carries the same impacts as a tropical cyclone, but it's not fully warm throughout the system and it derives some of its energy from upper-level winds. A fully tropical cyclone would be warm from top to bottom and the thunderstorms near the center of the storm would completely drive its formation and maintenance.



We're almost to the point where you can wager money on a named storm forming before June 1 and wind up winning the bet. This is the seventh hurricane season since 2009, and the fifth season in a row, that we've seen at least one named storm form in the "pre-season."

I argued a few weeks ago that we should move the beginning of the Atlantic hurricane season up a few weeks into May. Not only would moving up the start of the season to, say, May 15, which would sync it up with eastern Pacific's season, but it would start the awareness campaigns a little earlier than they run right now. That'd be helpful for coastal residents, seeing as several of these "pre-season" storms, like Alberto in 2018, wound up making landfall in the United States.

The tropics should fall quiet again for a while after Andrea dissipates.

[Top Image: RAMMB/CIRA]



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Here's Why the Atmosphere Is Primed for a High-End Tornado Outbreak on the Plains



A rare high risk for severe weather is in effect Monday for a large chunk of Texas and Oklahoma, now including the Oklahoma City metro area, ahead of what could be a high-end severe weather event for the region. It's been a long time since conditions have been this ripe for severe weather on the southern Plains. Today's forecast—and stern warnings from meteorologists—are the weather equivalent to red lights flashing and alarm bells ringing. Here's a quick look at why the environment is so primed for dangerous thunderstorms today.

(See my post earlier today for a detailed look at today's threat and some safety advice.)



The high risk is in effect because of the high risk for potentially violent and long-track tornadoes—and that's the SPC's words, not mine. There's a 45% risk for tornadoes across parts of Texas and Oklahoma, which is an extreme probability when you consider your daily risk of seeing a tornado, even on the Plains, is down around 0%. The tornado threat isn't confined to the high risk. Just about everyone in Oklahoma, a large chunk of Texas, and parts of Arkansas, Missouri, and Kansas, are under an elevated threat for tornadoes today. For some perspective, we really start to get concerned when the probability for tornadoes ticks up to 10% or higher.

Here's why this is happening today.

Modeled upper-level winds at 3:00 PM CDT Monday. (NOAA/SPC)


A powerful jet stream—unusually powerful for this far south in late May—moving across the southern Rockies will set the stage for dangerous thunderstorms across the southern Plains on Monday. The trough generated a low-pressure system at the surface in northeastern New Mexico, which is allowing strong southerly winds to drag deeply unstable air north from the Gulf of Mexico.

Modeled surface Theta-E at 4:00 PM CDT Monday. (TwisterData)


The above image shows "Theta-E" at the surface this afternoon, according to the latest run of the GFS weather model. Theta-E is a great way to visualize an unstable air mass in this kind of severe weather setup because it combines temperature and moisture. The reds and purples over Texas and Oklahoma show warm temperature and high moisture, which act as the fuel that powers thunderstorms.

Severe thunderstorms will develop in a hurry today in that warm sector over Texas and Oklahoma. Storms will likely start firing along the dry line, which is the sharp gradient between high moisture and low moisture located over the Texas Panhandle, and grow eastward from there through the afternoon and evening hours.

A diagram of wind shear (left) and a diagram showing how a thunderstorm updraft tilts that rotation into the vertical, leading to a supercell thunderstorm (right). NOAA/NWS


Any thunderstorm that develops has the potential to turn into a tornadic supercell in this kind of environment. A supercell is a thunderstorm with a rotating updraft. The updraft begins rotating due to strong wind shear through the atmosphere. We've got strong southeasterly winds near the surface and strong southwesterly winds at the upper-levels of the atmosphere. The rapid increase in wind speed and sharp change in wind direction with height creates horizontal rotation in the atmosphere. The updraft in a developing thunderstorm can push that horizontal rotation into a vertical position, which causes the updraft (and the storm itself) to begin rotating.

Modeled Significant Tornado Parameter (STP) at 3:00 PM CDT Monday. NOAA/SPC


You can neatly summarize the threat by looking at composite indices, which take into account factors such as wind shear and instability to determine the threat for features like supercells and significant tornadoes. The above image is a model-generated image of the much-advertised "significant tornado parameter," which shows how favorable the environment is for significant (EF-2+) tornadoes. STP values around 1 or 2 are typically cause for concern, so when we're seeing models spit out a large field of values greater than 6 where we know dangerous thunderstorms will likely develop, the alarm bells start going off.

I mentioned in my last post that not every storm will reach its maximum potential, but there's a really, really good chance that some storms will:

It appears the environment will be capable of supporting a high-end severe weather outbreak. It's hard for big severe weather outbreaks to occur. Lots of things have to go right and it's easy for storms to morph into a sloppy mess on a day like this. Even if the storms on Monday don't reach maximum capacity—and many likely won't!—one storm breaking through to produce one bad tornado is still a big deal.

I keep flashing on the Lee County, AL, tornado from a couple of months ago. The storms that day were largely sloppy, but one supercell broke loose and put down an EF-4. It's cliche, sure, but it really does only take one. Please take the threat seriously and prepare even if it doesn't turn into a classic tornado outbreak.
Even the storms that don't produce significant tornadoes will be dangerous. This severe weather outbreak will occur in several rounds. Supercells will eventually grow and merge into large clusters and lines of thunderstorms, which could produce damaging rain and very heavy rain that leads to significant flash flooding.

Keep following updates from the Storm Prediction Center and your local National Weather Service office throughout the day.


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A Rare 'High Risk' Tornado Outbreak and Flash Flooding Are Likely in Texas and Okla. Monday



Monday could be a high-end severe weather day on the southern Plains, with a threat of severe weather we only see once every couple of years. Multiple rounds of severe thunderstorms are possible, beginning in the morning and likely continuing after people go to bed on Monday night. This is a complicated setup that has the potential to produce significant, long-track tornadoes if the storms are able to take full advantage of the environment around them. Heavy rain from Monday's storms could also produce significant flash flooding in Oklahoma.

The Storm Prediction Center has issued a rare high risk for severe thunderstorms across parts of western Oklahoma and Texas. This is the highest category on the SPC's scale used to convey the risk for severe thunderstorms, saved only for days that feature dynamics that could produce the most dangerous severe weather outbreaks. A moderate risk—one rank lower, but still extremely serious—radiates from the high risk to include Oklahoma City, Tulsa, Lubbock, and Abilene.

It's been two years since we last saw a high risk issued by the Storm Prediction Center. The agency reserves high risk days for when they're forecasting high-end severe weather events. They're very careful not to pull the trigger on a high risk so that the term keeps its urgency and invokes a specific response from people in harm's way.

It appears the environment will be capable of supporting a high-end severe weather outbreak. It's hard for big severe weather outbreaks to occur. Lots of things have to go right and it's easy for storms to morph into a sloppy mess on a day like this. Even if the storms on Monday don't reach maximum capacity—and many likely won't!—one storm breaking through to produce one bad tornado is still a big deal.

I keep flashing on the Lee County, AL, tornado from a couple of months ago. The storms that day were largely sloppy, but one supercell broke loose and put down an EF-4. It's cliche, sure, but it really does only take one. Please take the threat seriously and prepare even if it doesn't turn into a classic tornado outbreak.

That said, the SPC's 2:00 AM EDT update on Monday doesn't mince words. Here are some of the phrases they use in their technical forecast discussion explaining why they issued this forecast:
"[...] a tornado outbreak is likely across the southern Plains. The tornado outbreak is expected to continue into the overnight period. This event should result in a significant threat to life and property."

"This will be ideal for a tornado outbreak with strong tornadoes [...]"

"[...] making conditions favorable for long-track strong tornadoes and possibly violent tornadoes."
The SPC doesn't use strong language like that lightly.

Timing

This will be a long-duration event that begins Monday morning and likely lasts through early Tuesday morning. The greatest threat for severe weather exists during the afternoon hours, but dangerous thunderstorms will be possible for a solid 12+-hour window.

It's likely that several rounds of storms are possible. The greatest tornado and hail threat will occur in discrete supercell thunderstorms that manage to engage with their environment without contamination from other storms. The greatest threat for damaging wind gusts and flash flooding will occur in squall lines and clusters of storms that train over the same areas.

Tornadoes



Monday's high risk is in effect due to the 30% probability of seeing strong, long-lived tornadoes within 25 miles of any point within the shaded area. A 30% risk doesn't seem all that big—we see a 30% chance of thunderstorms almost every day!—but when you consider your odds of seeing a tornado on any given day are down around 0%, it's extremely high. The 10% and 15% risk areas are also nothing to sneeze at. Usually you would start to raise an eyebrow when you see 10% on the chart.

Additionally, there's a risk for strong, long-lived tornadoes in and around the areas covered by black hatching on the map above.

Not everyone will see a tornado, of course, but the environment appears extremely favorable for strong tornadoes to develop in any storms that can tap into the instability and wind shear available to them on Monday. This has the potential to turn into a very serious situation very quickly.

Flash Flooding



It could turn out that flash flooding is the most significant disaster that unfolds across the southern Plains on Monday. High moisture and deep, robust thunderstorm activity will allow any thunderstorms that form to drench whoever's caught beneath them.

Heavy rain and flash flooding will occur regardless of tornadoes or damaging winds or large hail. It appears that many of the thunderstorms that form across Texas and Oklahoma on Monday will begin to train, or repeatedly move over the same areas like a train on railroad tracks. Some models are spitting out bonkers rainfall totals in Oklahoma—even approaching double-digits in just 24-36 hours.

This kind of heavy rain will quickly lead to life-threatening flash flooding, both for residents in vulnerable areas and motorists trying to cross roads covered by moving water. It doesn't take much water to carry a car downstream and drown the occupants inside. An average year sees more people die in floods than tornadoes. Take the threat for flooding just as seriously as the threat posed by the thunderstorms themselves.

Hail and Wind

Don't sleep on the threat for hail and wind. Strong supercells can produce enormous hailstones to the size of baseballs or larger. That can easily total a car and break through windows, skylights, and even flimsy walls and ceilings. It's certainly deadly if you're caught outside when that kind of hail is falling. Wind-driven hail is even more dangerous. Severe thunderstorm warnings say "stay away from windows" for a reason.

Everyone under a threat for severe weather on Monday is under a threat for damaging wind gusts. Straight-line winds can produce as much damage as a weak tornado, but over a much wider area. Downed trees are a hazard to people in cars and in homes. Power outages are a given. Structural damage is even possible if some of the squall lines can produce wind gusts above 70 MPH.

Perspective

Monday is sure to be a long, stressful day, and there's (understandably) quite a bit of anxiety about it. Many schools in Oklahoma have cancelled on Monday to keep everyone home ahead of the severe weather. Area businesses, churches, and governments will likely follow suit. The main goal is to keep people at home where they're safer than they'd be if they were in a big building or out on the roads.


This is prime time for tornadoes on the southern Plains. The last two weeks of May—and Monday's date in particular—occupy an uncomfortable period in tornado climatology in this part of the country. No two severe weather outbreaks are exactly alike. It's hard for a significant tornado outbreak to occur. But the environment is more than capable of supporting serious thunderstorms that could produce significant tornadoes. Even one storm producing one bad tornado is one too many.

Safety

The region's climate leaves most residents well-prepared for the basics of tornado safety. We all know the deal..."get to an interior room in the lowest level of the building, putting as many walls between you and the outdoors as possible." That's just the beginning, though.

Plan your day accordingly. Don't run to Walmart or another big box store when storms are on the way. Mentally map out your home, work, or school to scout out the safest place to go if a tornado warning is issued. Do you have a safe building to pull off the road if you have to go out? If you have to be in a big box store, do you know the safest place within the store? Ask the manager. Seriously. They have to have a plan for that kind of stuff in this part of the country.

Leave mobile/prefabricated homes. Spend the whole day somewhere safer—a friend's house, the library, anywhere but home. Mobile homes can start to roll and break apart in winds as low at 70 MPH. Even a small tornado can heavily damage or destroy a mobile or prefabricated home and leave you in a life-threatening situation. Hell, the bathroom in a McDonald's provides you with more protection than a mobile or prefab home.

Consider the flooding risk when seeking shelter from a tornado. If your home is in a flood-prone area, consider leaving and going somewhere safer for the day. You don't want to be put in the impossible situation of deciding whether to go to the basement—and possibly drown—or stay at ground level and possibly risk a direct strike from a tornado.

Wear a helmet, jeans, and closed-toe shoes if you have to take cover from a tornado. The most vulnerable part of your body in a tornado is your head and a helmet will spare you from at least some debris if the worst happens. Jeans and closed-toe shoes will protect your feet and legs if you have to walk over debris.

Make sure wireless emergency alerts are activated on your cell phone. These alerts have saved countless lives over the past couple of years. Some folks disabled these alerts ahead of a nationwide test last year. Keep them on! I often receive my emergency alert within a minute of my weather radio going off.

Use a weather radio. Many people in this part of the country already have weather radios. Modern weather radios are like smoke detectors for the weather. You can program them with your county's unique code so they sound a loud siren when you're placed under a watch or a warning. Most devices even flip on the weather radio feed and read the warning out loud.

Don't rely on tornado sirens for warnings. These systems are outdoor warning systems and they are not meant to be heard indoors. Tornado sirens are also vulnerable to technical failures, power outages, and wind shifts that affect where they can be heard.

Don't hide from a tornado under a bridge or overpass. It is not safe. Strong winds grow even stronger when they press under a bridge. Three people died under three separate bridges during the 1999 Bridge Creek-Moore tornado in central Oklahoma. Bridges will not protect you. Get to a sturdy building and take shelter there.

Don't hide from large hail under an overpass, either. Drivers trying to protect their vehicles from hail damage often wind up creating a traffic jam, stranding hundreds (possibly thousands) of people and emergency crews behind them. This is especially dangerous since large hail often precedes a tornado in a classic supercell, which could leave all those people trapped in the path of a tornado with nowhere to go.

Don't go storm chasing. Monday is going to be a dangerous day even for the experts and experienced weather enthusiasts, and it's magnitudes more dangerous for folks who don't know what they're doing. Just stay home. Honestly, if I was a storm chaser, my first move on Monday morning would be to book the first flight to anywhere out of Oklahoma City. I don't know why anyone wants any part of that mess, especially with the high risk for flash flooding in many of the areas expecting severe weather.

Keep up with the Storm Prediction Center's website through the day. The SPC issues severe thunderstorm and tornado watches, as well as short-term forecast discussions that can give you a heads-up of what's coming over the next couple of hours. Stay proactive on a day like this. You should know about the threat for storms an hour or two before they arrive. Don't simply wait for a warning to act.


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May 16, 2019

An Extended Period of Severe Storms Is Likely in the Central U.S. Starting Friday



A multi-day severe weather event will begin to unfold across the central United States beginning on Friday and lasting through early next week. It's been a while since we've seen a favorable setup that leads to a back-to-back(-to-back-to-back-to-back) severe weather threat like we're about to see unfold. Each day carries the risk of tornadoes, large hail, damaging winds, and flash flooding from torrential rainfall.



Five days of severe thunderstorms will occur in two rounds. The first round will begin Friday from western Texas northward to the Upper Midwest, with the severe threat sliding eastward Saturday and again on Sunday. The second round of severe weather will shift back to the central Plains on Monday—likely including Dallas-Fort Worth, Oklahoma City, and Wichita areas—moving east of there on Tuesday.

Despite some of the chatter that's caused my friends and followers some consternation over the last couple of days, the extended nature of this severe weather threat won't necessarily translate to an intense outbreak. It's prime time for tornadoes on the Plains, and it's likely that at least some of the tornadoes that occur will be on the stronger side. Five days of severe weather doesn't mean we'll see a Twister-like sequence of mile-wide wedges gnawing away at wheat fields each day, but rather that conditions will be favorable for dangerous thunderstorms over a longer period that we've gotten used to seeing over the last couple of years.

Classic supercells are dangerous, of course, but even a sloppy field of thunderstorms can produce damaging wind gusts, large hail, and extremely heavy rain that leads to flash flooding. Just because everything isn't a major tornado outbreak doesn't mean the threat can be shrugged off.

Heavy Rain




Before getting into the severe threat, it's important to note that the central part of the U.S. is expecting a lot of rain over the next couple of days from these thunderstorms. The joy of convection is that not everyone will see all of the rain predicted, and some will see much more than what's shown on the map. This heavy rain will lead to flash flooding in some areas, and it will exacerbate ongoing river flooding.

First Round—Friday/Saturday/Sunday

A trough in the jet stream moving over California—which brought the state some heavy rain and mountain snow—will cross the Rockies on Thursday night and set the stage for the first round of severe weather. A low-pressure system will develop at the surface and cross Nebraska during the day on Friday, providing the focus for thunderstorms to develop. Southerly winds at the surface will drag warm, humid air north from the Gulf, providing plenty of fuel for thunderstorms to quickly intensify once they pop up.

Friday:



The Storm Prediction Center on Wednesday issued an enhanced risk for severe weather for parts of Texas, Kansas, and Nebraska on Friday. The enhanced risk is split between two areas because of the different mechanisms expected to drive the storms.

The southernmost risk, encompassing parts of western Texas and Oklahoma, will develop along a dry line. A dry line is a sharp boundary separating areas of high moisture and low moisture at the surface, making them really easy to spot on dew point maps. If you learned about supercells and tornadoes in school, dry lines in Texas and Oklahoma probably featured prominently in your lessons.

A dry line pushing into an unstable environment can serve as a focus for the development of supercells capable of producing tornadoes, very large hail, and damaging wind gusts. Forecasters believe that's possible in parts of Texas and Oklahoma on Friday.

The other area of enhanced risk is closer to the low-pressure system at the surface in Nebraska. The warm sector near the center of a surface low is often a favorable area for focused severe thunderstorm development. The SPC's outlook on Wednesday said "very large hail" and tornadoes are possible there on Friday.

Saturday and Sunday:

Severe thunderstorms will likely form early Sunday ahead of a cold front advancing into central parts of Kansas, Oklahoma, and Texas. Tornadoes are large hail are more likely in discrete storms that form in the warm sector, while damaging winds and quick tornadoes are favored in storms that develop into squall lines. The threat for severe weather will shift toward the Mississippi River Valley on Sunday.

Second Round—Monday/Tuesday

Another trough will drop over the southern Rockies this weekend and emerge over the south-central Plains on Monday, providing the focus for the second round of severe thunderstorms. The latest forecast from the SPC has Monday's risk centered on parts of Texas, Oklahoma, and Kansas, shifting a little farther to the east on Tuesday. All modes of severe weather will be possible with this second round of storms. Forecasters will have a better idea about locations and specifics once we get closer to the second round of storms.

The forecast for specific locations on the maps above will likely have changed by the time you read this post, so, as always, it's a good idea to visit the Storm Prediction Center a few times a day during the warm season to keep up with their latest forecasts.

[Model Image: TwisterData.com]

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May 10, 2019

This Week, The U.S. Is The Least Dry It's Been In At Least 20 Years



A well-moisturized United States set a new record in this week's update of the U.S. Drought Monitor (USDM), with more than 90 percent of the country not experiencing any type of drought or "abnormally dry" conditions. This is the greatest expanse of the contiguous United States that's escaped unusual dryness since the USDM began issuing its analyses on January 4, 2000.



This is the fourth week in a row we've set an all-time record for the amount of land that's seen on-par or excessive hydration. The only regions experiencing dry conditions at the moment are a chunk of the southeast, a lingering-but-much-improved drought in the Four Corners region, and the long-term drought in the Pacific Northwest that steadily improved through the winter and early spring months.

Bob Henson of Weather Underground reported this week that the United States just endured its wettest 12-month period on record, with records dating all the way back to 1895. Recently, an assortment of storm systems over the last couple of months provided ample opportunities for rain and snow from the Pacific coast to the Atlantic seaboard. Above-average snowfall in the northern Plains and Upper Midwest set the stage for record river flooding downstream once it started to melt this spring. Ample rainstorms across the West Coast allowed the entire state of California to completely eradicate its drought—and even see many of its reservoirs approach 100 percent capacity.

Strictly from a drought-is-bad perspective, the May 7 update is probably the best drought monitor we'll see for a long, long time. It took a long time to get here. It wasn't too long ago that it felt like the epic droughts in California, Texas, and the southeast would never end.



We're almost six years removed from the July 17, 2012 update of the USDM, which showed a record high of 80.75 percent of the United States in some form of dryness or drought. The weeks-long heat wave that summer was infamously miserable, the effects of which included the destructive derecho that tore across the Midwest and Mid-Atlantic on June 29, 2012.

The drought monitor is analyzed every Tuesday and the results are released every Thursday morning. Subsequent drought monitor updates likely won't change much from what we're seeing this week. The greatest chance for drought relief exists in parts of the southeast, while warm and dry conditions will likely contribute to a spread of dry/drought conditions in the Pacific Northwest.


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Another Round Of Flash Flooding Is Likely In Southeastern Texas Over The Next Few Days



Extensive rainfall over the last week will set the stage for more flash flooding in the Houston area over the next couple of days as another round of extreme rainfall drags across the region. More than half a foot of rain is possible through Saturday as periodic thunderstorms train across southeastern Texas.



NOAA's Weather Prediction Center calls for a ton of rain across the northwestern Gulf Coast over the next seven days. Much of that rain will fall through the weekend. A significant threat for flash flooding will unfold across coastal communities over the next couple of days, with the greatest chances occurring in areas that saw heavy rain earlier this week.

It's important to note that not everybody painted in "build an ark" colors on the above map will see all that rainfall. Rainfall totals will depend on the tracks of individual thunderstorms and where the training thunderstorms set up. Training occurs when heavy thunderstorms continuously develop and moves over the same areas for hours at a time, appearing on radar like train cars moving along railroad tracks.

Houston's Hobby Airport recorded 2.26" of rain in the one hour between 9:53 PM and 10:53 PM on Thursday night. The chance for that kind of flooding rain will persist through early Friday morning, and continue across the region through Saturday before a pattern shift allows things to calm down.



The latest observations between the mornings of May 2 and May 9 show up to a foot of rain has fallen across parts of Harris, Montgomery, and Fort Bend counties in southeastern Texas, covering some of Houston's suburbs. The extreme rainfall totals were rather isolated; unlike Hurricane Harvey, which broke area-wide rainfall records, this week's intense rains were the result of thunderstorms that merged and trained over relatively small areas.

Small as this week's rainfall bullseyes have been, though, they caused significant problems. News reports from Houston described a flash flood in Sugar Land, one of Houston's southwestern suburbs, occurring so quickly that residents barely had time to react to water covering their streets and entering their homes. One resident told the Houston Chronicle that the flooding was "quicker than Harvey." Neighborhoods that didn't flood in Harvey are still at risk for flooding—the ground in the Houston area leaves the entire region susceptible to flooding. Areas that don't flood in one major rainfall event could easily flood in the next as every situation is different.

This region is no stranger to flooding. Hurricane Harvey in 2017 brought the worst flooding ever recorded in southeastern Texas, killing dozens of people and leaving thousands more homeless. Extensive flooding followed more than a foot of rain in some of Houston's suburbs in April 2016, less than a year after double-digit rainfall totals turned area interstates into rivers and left behind nearly half a billion dollars in damages.


[Top Image: Radar at 10:15 PM CDT May 9, 2019, via GREarth/AllisonHouse]


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May 3, 2019

The 1999 Okla. Tornado Sticks With Us Because It Was Our First Immersive Weather Disaster

Twenty years ago today, a mile-wide tornado touched down in central Oklahoma and forever changed the way Americans viewed severe weather. The F5 tornado was so strong and so destructive that it's served as a benchmark for all tornadoes since. People who otherwise wouldn't pay any mind to the weather, even people who live thousands of miles away from Oklahoma, can usually recall that one storm because it was our nation's first experience with the shock of fully immersing ourselves in the scope and power of a natural disaster.

24/7 news fundamentally changed the way we process emergency situations in faraway places. When we watch a disaster unfold on television or online, we're not watching something that already happened. We're taking in the disaster before we know the outcome. You can flip on any news channel and hear the screams and the gunshots and see the fireballs and the towers fall and monitor live footage from storm chasers who follow so close to the tornado that you can practically see the occupants of newly-destroyed houses getting pelted by their shredded living rooms if you look hard enough.

It's like you're right there as it happens, and that leaves a mark.
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The tornado in 1999 turned into a national trauma because we saw it happen live and you could relive the storm from every possible angle. A news helicopter chasing the tornado hovered over leveled homes before the people inside had a chance to crawl out of the debris. Live footage from the ground showed a mile-wide wedge of darkness tearing into neighborhoods like a desk fan through playing cards. A news station's chief meteorologist sternly told viewers that they needed to be underground to survive the storm while the television screen showed neighborhoods so freshly destroyed that the debris hasn't stopped falling from the sky yet.

The Bridge Creek-Moore tornado was a horrific storm that's served as the high water mark for every tornado in the 20 years since that day. It was one of the strongest tornadoes on record and it was one of the deadliest tornadoes ever recorded in Oklahoma. And it was the first time many Americans actually saw what happens when a tornado hits your house rather than just seeing footage and photos of the aftermath. It took the curiosity spawned by the movie Twister three years earlier and made it real and personal. That could really happen. And it's stuck with us for the last two decades.

There had been big natural disasters before. Hurricane Andrew was a seminal moment in hurricane history that you could watch unfold on The Weather Channel. But up to that point, we'd only had piecemeal footage of large-scale natural disasters, and usually well after the fact. Most of the scale-topping tornadoes since the Super Outbreak of 1974 were filmed or photographed from a great distance. At the time, the 1999 tornado was likely was the most documented tornado in history. There are dozens, if not hundreds, of recordings both from a distance and right within the tornado itself.


Every national tragedy sparks those "where were you" conversations. Where were you when you heard Kennedy was shot? Where were you when you heard the planes crashed? We don't have to ask that anymore because we're always there now. Modern technology allows us to experience the psychological trauma of every attack or shooting or tornado or hurricane from every angle as it unfolds. The tornado in 1999—occurring at a time when camcorders were ubiquitous, documentaries were a mainstay on cable TV, and right in the middle of the internet boom—was the first of countless tornadoes to have been documented in such fine detail that you can watch it as if you were standing right there.

We've had plenty of tornadoes like this in the last 20 years. The tornado outbreak of April 2011 was documented in frightening detail. The tornado in Joplin, Missouri, just a month later was so ruinous that it leveled every building as far as the eye could see. And there was another EF-5 tornado in Moore, Oklahoma, that left behind similar death and destruction with even greater documentation than the storm 14 years earlier. Those tornadoes are all memorable, but none so memorable for so many people as the F5 tornado that touched down on May 3, 1999. That storm 20 years ago today was our first full experience with this new era of watching the weather. And it was terrifying.


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