March 24, 2020

Some Strong Tornadoes Are Possible In Alabama And Tennessee On Tuesday Evening

Not for nothing, but the recent questions about whether it's safe to break social distancing to seek shelter from tornadoes in community storm shelters wasn't a hypothetical. There's a risk for severe thunderstorms across parts of the southeastern United States this afternoon and evening, with a risk for damaging winds, large hail, and tornadoes. Some of the tornadoes could be strong or long-tracked. The threat will ramp up in the late afternoon and evening hours, clearing out as the night progresses.

Today's setup is common for what you'd see on a late March afternoon. A weak low over southeastern Oklahoma will set the stage for the severe weather today. Thunderstorms will develop in the warm, muggy air over the southeastern states as the low moves east through the evening.

Severe thunderstorms are possible this afternoon and evening across a wide area from Little Rock to Myrtle Beach. Any thunderstorms that form across this area today could produce damaging wind gusts in excess of 60 MPH, hail the size of quarters or larger, and tornadoes.

There's plenty of wind shear in the atmosphere for thunderstorms to organize into supercells along and near the warm front. As a result, the Storm Prediction Center issued an enhanced risk for severe weather in northern Alabama and southern Tennessee, including Huntsville, Decatur, and Florence. The area under the enhanced risk got upgraded due to a 10% risk for "significant" tornadoes, which means the environment is capable of supporting strong (EF-2+) or long-tracked tornadoes.

Most folks are home right now as a result of school and business closures. It's important to pay attention to the weather even as we try to distract ourselves from the boredom at home. Peeking at the radar on a weather app, leaving local news or The Weather Channel on in the background, keeping the NWS open in another tab...anything that keeps the weather in constant view is a good plan today so warnings don't pop up by surprise.

The best way to receive tornado warnings is to activate the emergency alerts on your smartphone. Even if all the other alerts are disables, make sure tornado warnings are switched on. These alerts go off the moment a tornado warning is issued for your location. They've alerted me to tornado warnings when I wasn't paying attention before, and I'm constantly staring at the radar. It's a good system to have.

Oh, one more thing. Please...pretty please...don't rely on tornado sirens for tornado warnings. These systems are only designed to be heard outdoors and there's no guarantee they'll work at all in the middle of a raging thunderstorm.

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March 23, 2020

Storm Shelters: It's OK To Skip Social Distancing For An Hour If It Means Surviving A Tornado

Most Americans are parked at home right now as we try to slow the spread of a dangerous virus that's moving through communities here and around the world. But even as we adjust our lives to spare one another, the world continues around us just as it ever would. We're quickly moving into the heart of severe weather season and it won't be long before we have to deal with tornado outbreaks on top of everything else that's going on. It's important to remember that sheltering from a tornado is an urgent matter of life or death that (at least, temporarily) overrides our need to practice social distancing.

This may seem like a weird question to ponder for folks who live outside of the southern United States, but it's a pressing concern for lots of people who don't have safe shelter at home.

The concept of "community storm shelters" has grown in popularity in the south, especially after several devastating tornadoes and tornado outbreaks during the 2010s. A community storm shelter is a large reinforced room designed to hold lots of people—sometimes an entire neighborhood—who don't have a better alternative to ride out a storm.

Now that we're trying to slow the spread of COVID-19, huddling together with a few dozen of our neighbors doesn't sound like the best thing to do right now. The rapid approach of severe weather season is going to force people to choose between social distancing and staying safe from a tornado. Seeking shelter from a tornado is absolutely the best bet. In a dangerous situation like this, it's absolutely riskier to stay in an unsafe home and hope the tornado misses than it is to come in close contact with your neighbors.

The Alabama Department of Public Health released a joint statement with the National Weather Service offices in Huntsville, Birmingham, and Mobile, on Sunday addressing this concern. Their advice is simple: the urgent risk posed by a tornado temporarily outweighs the risk of the virus, and to seek shelter if one is available.

As the statement points out, it's critically important to know whether or not a shelter is open before severe weather strikes. If not, make alternate plans to stay somewhere safe before a warning is issued.

Tornado safety advice tells us to seek shelter in an interior room on the lowest level of a home or building. The goal is to put as much distance between you and the wind and flying debris as possible. The aftermath of stronger tornadoes often leaves just an interior bathroom or closet standing even as the rest of the house is swept away.

That's not always an option for some communities. Millions of people live in mobile homes that can barely withstand the wind gusts of a potent thunderstorm, let alone the violent winds of a tornado. Millions more live in homes without basements, modular homes, or apartment buildings, all structures in which you're often reduced to picking the least-worst option to ride out a tornado.

Folks who live in homes that can't withstand strong winds have to go somewhere else to stay safe ahead of a tornado. It's common practice for folks who live in mobile homes, for instance, to spend the day at the library or at a friend's or relative's house on a severe weather day. Unfortunately, there aren't many public spaces left open to seek shelter—libraries, schools, restaurants, and most other businesses are closed, which can limit one's options in a pinch.

Do what you need to do to stay safe. But during a tornado, it should go without saying that you've got to get to a safe place to ride out the storm.

Weather safety advice has come a long way in the last couple of decades, but there are still some pressing questions for which there's no easy answer. The most analogous scenario to this "distance or shelter?" question was a situation faced by thousands in and around Houston during Hurricane Harvey in 2017. The storm produced historic flooding in southeastern Texas, and, as we commonly see during a landfalling tropical system, many of those heavy thunderstorms wound up spawning tornadoes. This put lots of people in the horrible situation of choosing between staying low in the water to escape the tornado or climb high away from the water and hope the tornado missed.

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March 19, 2020

A Widespread Threat For Severe Weather Will Cover The Central U.S. On Thursday Evening

A widespread risk for severe weather will develop across much of the central United States on Tuesday as warm, humid air surges northward behind a warm front. Several rounds of severe thunderstorms will develop through Thursday night, bringing the risk for damaging winds, tornadoes, and large hail. The greatest tornado risk appears centered on the Mississippi and Ohio Rivers.

Today's severe weather threat looks like the first large-scale severe weather threat of the season, with a slight risk extending from Waco to Milwaukee, Grand Island to Columbus, and everywhere in between. The Storm Prediction Center issued two separate enhanced risk areas for Thursday evening; one covers the threat near the center of the low-pressure system across portions of Iowa, Missouri, and Nebraska, while the other covers the threat for severe storms between central Arkansas and southern Indiana.

Source: Tropical Tidbits

You can see the basic setup by glancing at a map of dew points this afternoon. There's a beautiful low-pressure system centered right over the Colorado/Kansas border this afternoon—look at the moisture swirling around its center!—with a series of warm fronts extending from there all the way east to the Delmarva Peninsula. This swath of warm and humid air will fuel the development of thunderstorms this afternoon and evening, and strong wind shear through the atmosphere will allow many of the storms to grow severe. The warm front will serve as a focus for the tornado threat across Iowa, Missouri, and Nebraska, while a low-level jet will drive this evening's tornado risk in the Mid-South and Ohio Valley.

A 10% risk for tornadoes exists across both of the enhanced risk zones, with slightly lower threats radiating out from there. That doesn't sound like much, of course, but when you consider there's typically about a 0.1% to 0.2% risk for a tornado within 25 miles of any location across today's risk areas on an average March 19, today's 10% risk should make everyone's ears perk up and pay attention to the radar.

Damaging winds are likely in any of the thunderstorms that form today. Don't sleep on the damage that can result from 60+ MPH wind gusts. It's important to take severe thunderstorm warnings seriously, as well. Flowers and leaves are developing on the trees now, which can act like little sails by catching the wind and adding stress to limbs and trunks.

Any of today's severe thunderstorms could produce large hail (the size of quarters or larger), but there's a risk for "significant" large hail—the size of golf balls or larger—across the enhanced risk in IA/MO/NE.

Nighttime tornadoes are exceptionally dangerous because people are tuned-out, asleep, or they can't fight their urge to look outside and visualize the threat before they take action. As always, make sure wireless emergency alerts are activated on your phone before you tune-out or go to bed tonight. Given the advanced radar technology available to meteorologists today, you can trust that you're at risk if your location goes under a warning.

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March 12, 2020

There's A Risk For Some Strong Tornadoes Over The Western Ohio Valley On Thursday

Severe thunderstorms are likely across parts of the Ohio Valley and Mid-South on Thursday afternoon. Some of the thunderstorms will be capable of producing tornadoes, some of which could be strong or long-tracked. 

The Storm Prediction Center issued an enhanced risk for severe weather from southeastern Missouri to central Kentucky, with slight and enhanced risks radiating out from there to cover a wide area from northern Texas to central North Carolina. The bullseye for severe weather is the western Ohio Valley, including Bowling Green and Evansville. This is the area where conditions are most favorable for supercell thunderstorms capable of producing tornadoes.

A low-pressure system developing over the mid-Mississippi Valley on Thursday morning will provide the focus for strong to severe thunderstorms to develop across the risk area. There’s enough lift and wind shear for thunderstorms to develop into supercells capable of producing tornadoes. Conditions appear favorable enough across the enhanced risk area that some of the tornadoes could be “significant,” per the SPC, which means that the tornadoes could be strong or long-tracked. This is most likely along or near the warm front, since surface boundaries tend to serve as a focal point for tornadoes.

If you’re in or anywhere near the areas that could see severe thunderstorms today, the best way to prepare is to make sure that the emergency alerts are activated on your phone. It’s the best way to receive tornado warnings the moment they’re issued for your location. Emergency alerts are located prominently in your phone’s settings. Folks tend to disable all of the alerts after one ill-timed disruption for a flash flood or AMBER Alert; leaving these alerts enabled for tornado warnings is a good idea no matter how many disruptions they cause.

Source: NWS Nashville

The region is still reeling from last week’s severe weather. Several destructive tornadoes moved across central Tennessee early in the morning on March 3, producing severe damage up to EF-4 intensity across a path dozens of miles long. One of the tornadoes moved through the northern part of downtown Nashville, the second intense tornado to strike the city center in the last 22 years. (An F3 hit the downtown core in 1998.)

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March 3, 2020

A Meteorologist's Nightmare: A Strong Tornado Struck Downtown Nashville After Midnight

Nashville lived through a nightmare early Tuesday morning as a strong tornado struck the city’s core in the middle of the night. The tornado—or tornadoes, if there were several along a path—touched down west of Nashville after midnight and likely continued well to the city’s east, killing at least nine people and damaging hundreds of homes and businesses. The tornado was strong enough to loft debris thousands of feet into the air just as it began moving over the heavily populated downtown core.

The long-lived supercell began in west-central Tennessee and moved toward the Nashville region around midnight. The Storm Prediction Center issued a tornado watch for central Tennessee at 11:20 PM CST as they watched the supercell move toward the area. (Yes, they really do issue watches for single thunderstorms, and for good reason!)

The National Weather Service issued a severe thunderstorm warning for Nashville and surrounding areas at 12:11 AM. The supercell’s well-defined hook echo tightened up considerably as it approached Nashville proper, prompting a tornado warning at 12:35 AM. Debris began showing up on radar within a few minutes, and a debris ball was clearly visible on radar a few miles northwest of Nashville by 12:38 AM (shown in the screenshot at the top of this post). The fast-moving tornado struck the north side of downtown Nashville at about 12:42 AM, continuing east of the city over the next hour.

An employee of NWS Nashville caught video of the rain-wrapped tornado as it moved through the city’s core. It’s hard to see the tornado as it’s obscured by rain and the dark of night, but power flashes caused by transformers failing in the strong winds make the path easily traceable as it races through town.

The supercell that spawned the tornado (or tornadoes) is an example of how it only takes a brief moment of the right ingredients coming together to create an exceptionally dangerous situation. The SPC’s discussion of the tornado watch mentioned how the storm “may maintain its organization in a marginally favorable low-level air mass for a few hours before weakening.” It sure did. The supercell found just enough instability and low-level wind shear along a surface boundary north of Nashville to spin up a strong tornado. 

Meteorologists will survey the damage on Tuesday and issue a preliminary rating based on the damage they find.

The very situation that played out in central Tennessee last night is one of the scenarios that keeps meteorologists and emergency managers awake at night. A tornado approaching a city center is terrifying any day, but a strong, fast-moving tornado at 12:30 in the middle of the night is near the top of the list when it comes to dangerous situations.

Severe weather is possible across parts of the southern U.S. over the next couple of days. As we head through this period of active weather—and start climbing toward the peak of springtime severe weather—it’s important that you have multiple ways to receive severe weather warnings. You don't want to get caught off guard by a storm anytime, but especially at night when you're tuned-out or asleep.

Make sure your cell phone is set to receive Wireless Emergency Alerts for tornado warnings. Spring a few bucks for a programmable NOAA Weather Radio if you can. It may seem redundant or outdated given all the technology we have now, but phones and weather apps don’t always work. It’s good to have a backup.

[Screenshot: Radarscope]

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February 29, 2020

The Rare Meteorological Phenomenon "Snow Firehose" Is Neither Rare Nor A Phenomenon

Poor CBS News. The more I write about their weather coverage, the more it just feels like bullying. The radar started spinning off the pedestal in 2014. First, there was CBS's infamous "sideways tornado," which was not a tornado. A year later, CBS discovered a 'massive' tornado that was perhaps massive to several ant colonies and no one else. They responded to criticism of that coverage by issuing a correction that the storm had the potential to turn into a massive tornado, just like I have the potential to turn into Andrew Walker.

A few months later, CBS reported on a "Monster 'Freak' Storm" (wrong) that brought 230 MPH winds to Iceland (wronger). Two years after that, CBS reported Hurricane Nate "touched down" (wronger-er) on the northern Gulf Coast, bringing flooding to the Mississippi River community of Mobile (wrongest).

And then there's Maude!

Today we learned about a "rare meteorological phenomenon" known as a "snow firehose."

Who knew?

I've used plenty of cheeky hyperbole in my oddball blogging adventures. I peppered The Vane with dorky phrases like "wind bagel," "dangerous sky onion," and "Polar Flortex" to describe annular hurricanes, large hail, and a storm off Florida, respectively. It was meant to be hokey!

But CBS News, bless its heart, isn't in on the joke. We've graduated from sideways tornadoes to a snow firehose. Granted, I'll give the reporter the benefit of the doubt that somewhere in his reporting, a meteorologist may have analogized the thick, intense band of lake effect snow plastering northern New York as akin to a firehose.

Nowhere, though, is it ever an actual term used for actual events. Go ahead. Google it. If you filter out February 27-29, it's nearly impossible to find any mention of "snow firehose" that doesn't loop back to CBS's report on Friday.
The band of lake effect snow over Watertown, New York, on February 28, 2020. (Gibson Ridge)

Lake effect snow can occur when wind blows cold air over relatively warm waters. The warmth of the water warms up the air immediately above the surface of the lake. This warm air rises through the colder air above through convection, creating bands of snow that blow ashore. The resulting lake effect snow can develop as thin bands that produce a broad swath of accumulation (common on Lake Michigan), or it can form into a solid band that traverses the length of the lake and plasters a small area with a lot of snow, which is common on Lakes Erie and Ontario.

The latter process, called single-band lake effect snow, is what we've seen in northern New York for the last couple of days. A long, cold fetch across an ice-free Lake Ontario allowed an intense band of snow to ride up the Tug Hill Plateau and drop several feet of snow. In fact, the orientation of the winds allowed for several bands of snow to set up across Lakes Superior, Huron, and Ontario, giving the appearance on radar that it was a single band of snow stretching from one body of water to the next.

Single-band lake effect snow is relatively common and it's often intense, dropping several inches of snow an hour and occasionally producing lightning. This was a particularly hefty band that dropped four feet of snow in some higher elevations. There's a reason northern New York isn't exactly known for sunbathing in the wintertime.

It's okay to refer to this as a "snow firehose" as an analogy to explain it, but it's not a term anyone uses seriously as the report reports. News organizations have got to be more precise and accurate in their reporting of events like lake effect snow. Meteorology is a science, after all, and goodness knows we don't need another ripe-for-TV buzzword at the expense of the facts.

[Screenshot: CBS News]

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February 21, 2020

Nothing Happened Today

There was no weather.

Weather is possible again tomorrow.

[Satellite Image of Nothing: NOAA]

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February 20, 2020

North Carolina Could See A Li'l Thump Of Snow On Thursday

A fast-moving storm will develop over the southeastern United States on Thursday, potentially dropping a couple of inches of snow across the eastern half of North Carolina and the Virginia Tidewater. There's still some uncertainty around the storm right now—oh, little things like "how much snow will fall?"—but it's likely that the season's first (and only?) snowfall is on the way.

This isn't going to be a mammoth storm, but it will drop a shovelable snow in areas that can go a few winters without seeing much snow at all.

Right now, most meteorologists in the state expect at least an inch of snow across most of North Carolina. The latest forecast from local National Weather Service offices shows the thinking. Forecasters don't expect the system to be a bangin' rock fest like the short-range models keep trying to spit out, though there's a 10 percent chance that the "high-end" totals grow problematic east of Raleigh. The position and movement of heavy bands of snow within the storm leave open the possibility that some towns in eastern North Carolina could see half a foot of snow or more.

Snow should begin in western North Carolina on Thursday morning, spreading east toward the coast through the afternoon hours. The evening rush hour, should there be one, looks messy for just about every part of N.C. and southeastern Virginia.

The storm will clear out to the Atlantic by Friday morning, leaving behind an icy mess that will make it tough to get around on untreated surfaces. Above-freezing temperatures and sunny skies should take care of most roads by Friday afternoon.

This is one of those uncomfortable situations where the final forecast will come down to the wire in a few spots. Some towns will see more snow than they were expecting, while others wind up with little to no snow at all. That's the nature of southern snowstorms.

Charlotte meteorologist Brad Panovich laid it out in plain terms on Wednesday. These flaky southern snowstorms rely entirely on minuscule changes in temperature and moisture throughout the atmosphere. If it's even just a little bit warmer than predicted, snow will change to sleet or freezing rain and the entire forecast is blown to smithereens. Dry air can chomp away at snow like a snack. If the storm moves five or ten miles farther north or south than expected, that also nudges the heaviest bands of snow right along with it.

Forecasters had a tough time getting a handle on this storm until Wednesday morning. Short-range regional models like the NAM, which is great for forecasting thunderstorms but not so much when it comes to snow, have been incredibly bullish on the threat for snow across N.C., consistently painting a swath of double-digit snowfall totals along and east of I-95. Global models like the GFS and European have been less impressed by the storm, lurching back and forth between a few inches and hardly a flurry.

Like many of its neighbors, North Carolina hasn't seen much of a winter so far this winter. It's as if the end of October started skipping and nobody bothered to jiggle the CD player. The coldest we've gotten in Greensboro this season is 20°F—potentially setting us up for the first winter on record without a low in the teens—and most of North Carolina has gotten this far without any measurable snow to speak of, another unusual feat for areas sees at least a dusting or two by the middle of February.

While winter storms aren't out of the question in the southeast in March, encroaching warmth from the south and the increasing angle of the sun makes it more difficult for wintry precipitation to fall with each passing day.

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