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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February 6, 2020

A Drenching Storm Could Bring Severe Storms, Flash Flooding To The Southeast Thursday





An unusually juicy storm for early February will drench the southeastern United States on Thursday, carrying a moderate risk for flash flooding and an enhanced risk for severe thunderstorms. The sprawling system is so large that it'll produce significant snows in northern New England at the same time it's bringing heavy rain to the southeast.

Flash Flooding

Precipitable water on Thursday afternoon, per the GFS model (Tropical Tidbits)


Widespread flash flooding is a distinct possibility along and east of the Appalachian Mountains on Thursday as a surge of moisture moves north from the tropics.

The above model image shows precipitable water (PWAT) on Thursday afternoon. PWAT is a measure of how much moisture is available in the atmosphere. If the PWAT value for Podunk is 1.00", it means that 1.00" of rain would fall if you were to wring out all the moisture in the atmosphere over that particular spot.

Higher PWAT values indicate a greater potential for heavy, flooding rains. Models indicate a potential PWAT of 1.50" (roughly 40 mm) or more across the interior southeast on Thursday, which is extremely unusual this far north at the beginning of February.

The heaviest rain and highest totals are likely in thunderstorms and along the eastern side of the Appalachians where orographic lift enhances the rainfall rates.

A moderate risk for flash flooding exists along and east of the Appalachians in Georgia, South Carolina, and North Carolina, according to the Weather Prediction Center's update on Wednesday night. It won't take much heavy rain to send waterways over their banks and overwhelm man-made drainage systems in populated areas.

The flooding threat here is similar to what we'd see from the remnants of a landfalling tropical cyclone. Thursday's weather is more common of the warm season than February 6—but it's also felt more like April for much of the winter, so why not?



Some areas could see more than 5.00" of rain as a result of the heavy and persistent rain. The Weather Prediction Center's latest rainfall forecast paints a widespread area of 4"+ of rain across the Southeast, with even higher totals possible along the eastern side of the Appalachians and where thunderstorms enhance rainfall rates.

Severe Thunderstorms

It's not just flooding that we have to worry about. The influx of warm, moist air, combined with extremely strong winds not far above the surface, will allow lines of strong or severe thunderstorms to develop and move across the southeast on Thursday.

Thunderstorms that fire up won't have to work hard to produce damaging winds, isolated tornadoes, and occasional instances of large hail.

An enhanced risk for severe weather is in effect on Thursday across much of the southeast from Florida's Big Bend through central North Carolina, including the cities of Tallahassee, Columbia, and Charlotte. Slight risk and marginal risk areas radiate out from there, covering just about everyone between Mobile and the Virginia suburbs of D.C.

It's likely that a portion of the severe weather will occur after dark, ratcheting up the threat as people tune out for the evening and go to sleep.

The best way to prepare for this kind of severe weather and flooding threat is to make sure the wireless emergency alerts are activated on your smartphone. I know it's repetitive to bring it up in every one of these posts, but lots of folks shut off the alerts after one ill-timed interruption. The push alerts are proven lifesavers, and it's possible for tornado warnings to catch you off-guard at home (it's even happened to me!) and it's even more common to unknowingly drive into an area experiencing flash flooding.

Snowstorm



It's worth mentioning that the northern fringe of this storm will bring significant snows to northern New England. This storm is large enough that it'll produce significant winter weather around the U.S./Canadian border at the same time it's drenching the southeast with flooding rains and severe thunderstorms.

This will be a long-duration event for northern parts of New York, Vermont, New Hampshire, and Maine, with some areas seeing a foot-and-a-half of snow by this weekend. The National Weather Service's latest snowfall forecast is shown above. Some areas to the south of the snow could see a glaze of ice from freezing rain that could lead to slick surfaces and spotty power outages. 



The storm left a decent blanket of snow across the southern Plains in its infancy on Tuesday night. This was the first significant winter storm to hit the area in a while. Oklahoma City measured its first inch of snow since January 19 of last year, and this was the first measurable snow in Midland, Texas, since December 8, 2016.


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February 3, 2020

The Weather Should Mostly Cooperate For Monday's Cumbersome Iowa Caucus



Weather shouldn't hinder Iowans heading out to caucus on Monday night in the first contest of the 2020 presidential election. The lengthy and rigid nature of caucuses makes this type of voting more susceptible to dampened turnout than traditional elections. Most of Iowa can expect a typical February evening with subfreezing temperatures and a breeze that makes it feel even colder. Freezing drizzle might make for some slick roads in the southwestern part of the state.

Iowa's Democrats and Republicans will begin their caucuses at 7:00 PM CST. Temperatures will struggle to climb much above the 30s across most of Iowa during the day on Monday, allowing temperatures to quickly fall once the sun sets. The National Weather Service expects most of Iowa (except the southeastern counties) to fall below freezing by the start of the caucuses.

Patchy drizzle and freezing drizzle is possible across the southern half of Iowa during the evening hours, especially east of Omaha, which could make roads and sidewalks slippery in some places. Any icing issues could deter voters from heading out to caucus, but it's unlikely that the drizzle will become a big deal. Overall, it should just be cold and windy for the election's first voters.

Caucuses are a lengthy process compared to traditional elections. Rather than casting ballots, voters arrive at their voting precincts at a set time and physically gather in different sections of the room in support of their preferred candidate. Officials conduct a headcount for each candidate's section and tabulate the results. In the Democratic contest, supporters of candidates who don't win enough support have the opportunity to caucus for a different candidate or persuade others to come to their side before the second count. The final tally is used to calculate delegates at the state and national level.

Monday night's bearable conditions across Iowa should remove the one natural barrier to this otherwise obstacle-laden process. The involved nature of caucuses makes the event last about an hour, though a contested race or a heavily attended caucus can stretch it out even longer.

This kind of rigid time commitment—aside from making caucuses difficult to attend or flat-out inaccessible for parents, low-income workers, disabled individuals, those who are sick, those without transportation, or those for whom a public and confrontational voting process may be ill-advised due to social, domestic, or mental pressures—means that foul weather can easily dissuade potential caucusgoers from venturing into rain or snow or extreme temperatures. Political scientists have found that foul weather depresses turnout, and it stands to reason that the effect is even more pronounced in an involved caucus than it would be in a traditional election.

The 2020 presidential nomination process will feature less than half the number of caucuses we saw during the 2016 cycle. Democrats in 14 states held a caucus during the 2016 election, compared to just three traditional caucuses (IA, NV, and WY) this time around.


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January 18, 2020

Newfoundland Just Endured A Historic Blizzard That Buried People In Their Homes



Residents of eastern Newfoundland spent Saturday conducting an archaeological dig in a valiant attempt to remember what life was like before Friday's historic blizzard. The impressive snowstorm dropped more than two feet of snow on parts of the island in Atlantic Canada, an insult made even worse by 75+ MPH sustained winds that drifted the snow so high that many folks had to tunnel out of their homes.

Friday's snowstorm is widely considered to be one of eastern Newfoundland's worst blizzards in living memory by folks who were in the thick of it. St. John's, Newfoundland, the easternmost major city in both Canada and North America, recorded 30" of snow during the storm and reported blizzard conditions for about 17 consecutive hours between 8:30 AM on Friday and 1:30 AM on Saturday.

The airport's weather station saw a minimum air pressure of 970.5 mb on Friday evening as the center of the winter storm passed just offshore. Some communities around St. John's saw even greater snowfall totals, with Mt. Pearl—the name of a city, not a mountain—reporting just over three feet of snow by the end of the storm.










The pure volume of snow, combined with the immense size of the drifts, quickly transformed this storm from a quirky novelty into a serious situation. The most populated area of the province is at a standstill at the moment while crews attempt to clear away the steep drifts of snow.

Tropical Tidbits


This was the perfect setup for an epic blizzard in Newfoundland. A strong jet stream dipped over eastern Canada at just the right angle to allow a sprawling low-pressure system to rapidly strengthen off the island's southern coast. The storm then underwent bombogenesis, or the process of strengthening 24+ mb over the course of 24 hours...hence all the "bomb snowstorm" and "bomb cyclone" headlines you've seen this weekend. The northwestern side of the storm rode directly over the Avalon Peninsula, exposing St. John's and its suburbs to the storm's heaviest snow and strongest winds.

The St. John's area could see another 5-8 inches of snow on Sunday as another winter storm moves across the region. Temperatures could briefly jump above freezing on Monday before dropping back below freezing through next weekend.

[Top Image: NOAA]


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January 11, 2020

An Inch Of Ice From Freezing Rain (!) Is Possible In Parts New York And Quebec This Weekend



A significant ice storm appears likely across the U.S./Canadian border this weekend as a winter storm moves across the region. Conditions appear favorable for a prolonged period of freezing rain near the border from Michigan to Maine, with some areas potentially seeing as much as 1.00" of ice accretion on exposed surfaces. If the highest totals come to fruition, it will cause significant tree damage and widespread, long-lasting power outages.

The threat for wintry precipitation lies on the northern side of the dynamic low-pressure system that's causing all the severe weather in the southern United States right now. It's cold enough for some areas to see all snow—it's pouring snow in most of Iowa!—but warm air in the lower levels of the atmosphere will make a mess of things in many of the areas expecting wintry precipitation.

Significant Icing Possible

Forecasters expect a prolonged freezing rain event to unfold from Michigan to Maine—including our friends in Ontario and Quebec—as the system moves through the area on Saturday and Sunday. The National Weather Service issued ice storm warnings for eastern Michigan and portions of northern New York ahead of the system, while freezing rain advisories are in effect for parts of southern Ontario and Quebec, including the Montreal metro area.

Precipitation will start as rain early on Saturday, slowly transitioning to freezing rain from west to east on Saturday night as warm air takes over aloft and cold air entrenches at the surface. The storm will likely end with snow on Sunday.

Environment Canada warns of the potential for 15-30 mm of ice accretion from freezing rain in and around Montreal, which translates to about 0.60" to 1.20" of ice. That's a major ice storm anywhere, let alone a heavily populated metropolitan area.
NWS


The National Weather Service in Burlington, Vermont, calls for similar ice accretion totals in northern parts of New York and Vermont. The official NWS forecast on Friday night called for 1.00" of ice from freezing rain around Ogdensburg and Massena in New York, with around 0.50" of ice in northwestern Vermont.

It only takes about 0.25" of ice to begin doing damage to trees and power lines. Anything greater than that and the damage increases by a great deal. Significant and widespread damage to trees and power lines is likely once ice accretions exceed 0.50". Areas that see a full inch of ice could see power outages that last for a week or longer and roads made impassable by parts of (or entire) downed trees.

It's also going to be windy in many of the areas expecting freezing rain. Wind will only create additional stress on trees and power lines already struggling under the weight of ice. The additional weight of accumulating snow on the back-end of the system would complicate matters even further.

How Freezing Rain Forms

Freezing rain forms when a layer of subfreezing air hugging the surface is capped by a thick layer of warm air above it. Snowflakes melt as they fall into the layer of warm air. The melted snowflake—now a raindrop—falls into the subfreezing air at the surface, supercooling the liquid and allowing it to freeze on contact when it touches an exposed surface.
Tropical Tidbits


Data collected by weather balloons (or, in this case, simulated by weather models) do a fantastic job showing the temperature profile behind the formation of freezing rain. Take a look at the above sounding from Friday night's run of the GFS model near Montreal, Quebec, showing the atmosphere there just after midnight on Sunday.

The red line traces the temperature of air over Montreal from the surface to the top of the atmosphere. This particular model run shows a surface temperature of -9°C (about 16°F), while temperatures are firmly above freezing between 700 mb and 850 mb, or between about 5,000-10,000 feet above ground level. That's a freezing rain profile if there ever was one.

Freezing rain is finicky. It takes slow and steady freezing rain for ice to build into a thick crust. If it rains too heavily, the water won't be able to freeze on contact, simply running off and freezing into puddles on the ground instead. The worst ice storms are the ones that see hours and days of persistent freezing rain and drizzle. This won't be historic, but it has the potential to be memorable for folks in the hardest-hit areas. 1.00" of ice accretion from freezing rain is enough to fell thousands of trees and damage a power grid for a week or longer. That's no small inconvenience.

[Top Image: Tropical Tidbits]


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January 10, 2020

Dangerous Severe Thunderstorms Are Likely Across The South On Friday And Saturday



A dangerous mid-winter severe weather outbreak will roll across several southern states on Friday and Saturday, bringing the potential for all types of severe weather, including flash flooding. The threat will begin late Friday morning in Texas and slowly shift east through Saturday night.

Severe Weather Risk

The Storm Prediction Center issued a moderate risk for severe weather for parts of the Deep South on Friday, which is a risk more common of mid-April than mid-January. A moderate risk is a 4 out of 5 on the ascending scale used to measure the risk for severe weather.

The moderate risk covers a large portion of Texas, Louisiana, Oklahoma, and Arkansas, including Dallas, Shreveport, and quite a few smaller cities in between. Forecasters pulled the trigger on the moderate category due to the risk for significant, widespread wind gusts in excess of 70 MPH. While the red shading will get all the headlines, it's important to remember that damaging winds, tornadoes, large hail, and flash flooding certainly aren't confined to the moderate risk area. The overall threat for severe storms covers a swath from the U.S./Mexico border to St. Louis.

Damaging winds are the main threat with the storms on both Friday and Saturday, but don't discount the potential for some strong tornadoes. Supercells that develop ahead (or within) the lines of thunderstorms will be able to produce tornadoes, especially if they manage to break away from surrounding storms and take full advantage of the environment around them.

Saturday's storms carry much the same risk as Friday's storms—damaging winds in excess of 70 MPH, tornadoes (some potentially strong), large hail, and flooding rains—just farther east toward the northern Gulf Coast.

Timing

Severe thunderstorms are possible across Texas and Oklahoma as early as midday Friday, growing in coverage and intensity as the day wears on. The storms will organize and move into the most favorable environment for severe weather by Friday evening. The line (or line segments) will continue tracking east through Louisiana and Arkansas overnight on Friday into Saturday, reaching Mississippi and Alabama by Saturday morning.

It's helpful to think of this as one long severe weather event. Once the storms develop on Friday afternoon, the threat for severe thunderstorms marches east straight through Saturday night. A broken line of strong storms could even make it to the Carolinas by Sunday morning.

Severe weather taking place after dark makes it even more difficult to get the word out and keep up with rapidly changing conditions. It's tough to deal with nighttime severe weather because 1) people are asleep and 2) people like looking outside before they take cover. Make sure you've got emergency alerts activated on your smartphone so you can hear a tornado warning the moment one is issued for your location. If possible, it's a good idea to hold off going to sleep until the threat for severe weather passes.

The Setup

The GFS model's guidance for winds about 5,000 feet above ground level around 12:00 AM on Saturday, January 11. (Tropical Tidbits)


A low-pressure system will develop over Oklahoma on Friday morning, setting the scene for the severe weather we'll see over the next couple of days. The real story is the wind.

Winds will be ripping in the lower levels of the atmosphere ahead of the cold front, where a "low-level jet"—a localized area of strong winds—could produce winds stronger than 100 MPH just a few thousand feed above the surface. It's dangerous to deal with such strong winds so low in the atmosphere because it wouldn't take much of a downdraft for a thunderstorm to push those damaging winds down to the surface (hence the hullabaloo). A strong low-level jet can also increase the risk for supercells and tornadoes.

Flooding Risk

Damaging winds and tornadoes aren't the only threat over the next couple of days. Showers and thunderstorms will bring a risk for flash flooding for a huge swath of the country from Texas to upstate New York. Several inches of rain are possible even in areas that aren't expecting any severe thunderstorms. This kind of heavy, persistent rain will push natural waterways and drainage systems to their limit, especially if the rain falls quickly. The heaviest totals are likely across areas where severe thunderstorms as possible, where the Weather Prediction Center calls for more than 5 inches of rain in some spots.



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January 8, 2020

Twitter's Proposed "No Replies" Feature Could Be A Nightmare During Weather Emergencies



Twitter announced on Tuesday that they would test a new feature to give users another tool to deal with the site's rampant and often-unchecked harassment problem. Twitter users will be able to limit who can reply to their tweets, even allowing users to shut off replies to their tweets altogether. This feature could have major unintended consequences when it comes to countering false or misleading information. This is especially true during weather emergencies like tornado outbreaks or hurricanes, where every second counts and even a short-lived viral weather hoax can do significant damage to the safety and trust of those in harm's way.

Last year, Twitter rolled out a feature that let users hide individual replies to their tweets, which is great if you get one hateful bonehead yelling at you or saying something completely off-the-wall. In practice, though, it's often used to hide dissenting opinions or replies that attempt to debunk hoaxes and conspiracy theories. Today's proposal goes a step further by allowing users to completely prohibit replies to tweets altogether.

As someone who's been on the receiving end of more hate mail and death threats than anyone should ever see, it's a positive step that Twitter is at least attempting to create tools that help people shake off nasty or harmful replies, even if it's far from enough to address the overall problem. But this new feature fundamentally alters how people interact with each other on Twitter. Limiting or prohibiting replies to certain tweets could have serious unintended consequences when it comes to the spread of fake weather news.
YouTube


Imagine the scenario I posted on Twitter this morning. We're in the middle of an intense springtime tornado outbreak and a line of supercell thunderstorms is marching across the southern Plains. Amid the flurry of reports comes an ominous tweet: "TAKE SHELTER—MASSIVE TORNADO HEADING TOWARD DOWNTOWN DALLAS!" Attached to the tweet is a picture of the EF-5 tornado that devastated Moore, Oklahoma, on May 3, 1999.

Seasoned meteorologists spot it immediately and try to wave people off of the malicious hoax as it rapidly goes viral in the growing panic, but the person who published the hoax shut off all replies. Meteorologists can't directly reach people seeing the tweet as it crosses their feeds. The only thing most people see is the warning, the old picture, and the fact that it's going viral. Meteorologists have to put the warning on their own feeds and hope that, in the fog of harried warnings about real storms, enough people see the corrections to make a difference.

It's not unrealistic. People pass off old pictures or false information all the time in the midst of severe weather events—tornadoes, hurricanes, floods, blizzards, fires, you name it. Some folks do it for the thrill of going viral, while others just get a sick pleasure out of tricking others in a time of crisis.

That very situation has played out before during tornado outbreaks, but other Twitter users were able to blunt the impact by quickly and forcefully pointing out the hoax. Right now, you have a chance to reach people who are seeing the false information by replying to a tweet. "Hey, this is false. This is an old tornado picture." People do click tweets and look through the replies.

This feature will remove the ability to directly reach those who are taken in by the false information. If there are no replies, that false weather report just hangs out there for thousands of people to see with no indication that it's not true. Under the new system, anyone who tries to refute the incorrect information has to implore their followers to help them spread word that it's bunk. It's a mess, and the corrections don't reach the people who are seeing the viral hoax.

Misinformation and outright hoaxes have plagued the weather community since social media came into widespread use. It's easy for anyone to sound authoritative and go viral. However, unlike politics where stories can take days or weeks to play out, severe weather occurs over a matter of minutes. A major tornado can touch down, destroy neighborhoods, and dissipate in just a couple of minutes. The decision to evacuate ahead of a hurricane needs to be made quickly. False information about the weather isn't just a silly internet thing—it can have a serious, real-world effect on people's safety and well-being.

With the ability to turn off replies to tweets, anyone can craft themselves into an authority figure on any subject without consequential pushback. Folks try to do that anyway, of course, but if you post "this blizzard will hit Washington tomorrow," you're going to get 200 people telling you you're wrong, and anyone who looks at your tweet will see all the people who corrected your misinformation. Eliminating replies will remove that pressure to skew toward truth. In practice, the tweet with the most retweets will become the uncritical truth on the subject, because now who will say otherwise?


After I posted that scenario on Twitter, the company's product lead reached out and said that they were taking this risk into consideration. Using the site's other features to respond to or highlight someone else's tweet simply isn't enough. It's important to be able to pipe up and say "no, this is wrong" when someone posts something that could lead people astray. Without some major tweaks or guards against it, this new feature will make it that much harder to get the word out during bad weather.


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