December 31, 2019

The April 27, 2011 Tornado Outbreak Shaped How We Viewed The Weather In The 2010s

This was the first decade that allowed us to track every weather event on social media in excruciating detail. We went into 2010 getting weather info from big companies, a few apps, and a handful of popular blogs. We're ending 2019 with more apps and Facebook and Twitter pages than any one person could ever hope to download or follow. The technological advances we've seen in the last ten years changed how we consume weather information, but the storms themselves—and one outbreak in particular—did just as much to shape how we approach future weather events.

April 27 was a seminal moment in meteorology. The peak of the generational tornado outbreak that unfolded that day shaped severe weather communication for every major outbreak since. Much of the day's legacy involves personal impacts and the emotional toll it took on people affected by the storms and the meteorologists who watched them unfold.

216 tornadoes touched down on April 27, 2011, setting the record for the most tornadoes ever recorded in a single day. National Weather Service meteorologists surveyed the damage left behind by dozens of major tornadoes, including 4 scale-topping EF-5s. More than 300 people died as a result of tornado-related injuries.

The tornado outbreak was a well-predicted event. Meteorologists sounded the alarm days in advance that an unusually potent tornado outbreak might take place that afternoon. Long-track tornadoes allowed meteorologists to give people hours of notice ahead of the storms. Just about every local television and radio station preempted programming to carry live coverage of the storms.

Despite the advanced warning and extensive live coverage of the storms, hundreds were killed and thousands more were injured in the day's tornadoes. The high death toll was a combination of infrastructure failures and the sheer strength and number of tornadoes.

A powerful squall line swept through Alabama early in the morning on April 27, causing widespread power outages across the state. Several weather radio transmission towers went offline during the power outages, leaving many Alabama residents with no electricity and no NOAA Weather Radio going into that afternoon's storms.

The raw power of the tornadoes also contributed to the immense death toll. Many homes in the path of the strongest tornadoes were scrubbed from their foundations. There's no amount of walls separating you from the outdoors that can save you when your entire house is simply swept away.

That single afternoon built a culture of weather awareness in the south. To this day, Alabama's most beloved living resident is probably James Spann. People who normally wouldn't care about the weather can decipher radar products without needing any help. The physical, emotional, and mental scars left behind by that day's tornado outbreak did more to instill weather awareness and storm education than just about any event before it.

That day's events also shaped how we cover the weather. That afternoon is the reason I write about the weather today. Every meteorologist and weather enthusiast who was around and paying attention uses that day as the benchmark for how to measure their coverage of potential tornado outbreaks.

Think back to Hurricane Sandy in 2012, the EF-5 tornado in Moore in 2013, blizzards, major flooding, Matthew, Harvey, Irma, Maria, Florence, Michael, Dorian...all the major weather events that came after April 27, 2011, were covered through a lens adjusted on that horrible day.

It strengthened the resolve to push back against hype-filled weather coverage. It taught millions of people to pay attention to the weather and take everything seriously. The closest that weather folks as a whole have come to ringing the alarm as loudly as April 27, 2011, was back on May 20, 2019, a day when the atmosphere appeared primed for an intense tornado outbreak in Oklahoma, but the storms ultimately had trouble forming.

We'll have historic disasters in the next ten years. It's likely that some of them will set new benchmarks for storms in the years that follow. Thankfully, technology today is better than it was back on April 27. Smartphones are more prevalent than ever and they're all equipped with wireless emergency alerts that receive tornado warnings instantly. Weather radar was upgraded with dual-polarization in the 2010s, giving us the ability to see tornado debris in a storm.

The next decade will see more advances in forecasting, detection, and alerting, progress that will help us stay ahead of storms even better than we can right now. People change. Tech changes. The weather is changing. It's up to all of us—meteorologists, reporters, the public—to learn the lessons of the past and apply them to whatever storms lie ahead.

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December 25, 2019

This Was The Warmest Christmas On Record For Much Of The Midwest

The sun just set on one of the warmest Christmases in recent memory. The abnormal blast of winter warmth stretched from the Rocky Mountains to the East Coast, with the bulk of the above-average temperatures focused on the central part of the country. Temperatures climbed as much as 30°F above normal in parts of the central United States on Wednesday afternoon, leading several cities to their warmest December 25 on record.

A strong ridge of high pressure over the eastern two-thirds of the United States is responsible for the current burst of above-average temperatures. The most significant and widespread warmth occurred on Wednesday afternoon, but the unseasonably comfortable temperatures will stretch into Thursday and Friday for some in the eastern part of the country.

This kind of warmth doesn't seem like much. It's pretty nice out! How often do you get to throw the windows open on Christmas and air out the house before the cold of winter sets in? However, just because it's comfortable doesn't mean that this isn't an unusually warm stretch for late December. It's easy to lose sight of the fact that it's not supposed to feel like late September in late December when that eye-popping temperature anomaly's practical effect is "ooh, this is comfy."

Dozens of reporting stations broke their daily high temperature record for December 25, cementing this as the warmest Christmas on record for many parts of the Midwest. The animation above shows the high temperatures that fell (in red) on Wednesday.

Moline, Illinois, saw its warmest December 25 on record, topping out with a high of 62°F. That doesn't seem like much until you consider that the city's average high for this date is 32°F. The high in St. Louis, MO, clocked in at 70°F, which is also a solid 30°F above what the city should see this time of year.
City Average High
for Dec. 25
Observed High
on Dec. 25, 2019
Departure From
St. Louis, MO 40°F 70°F +30°F
Moline, IL 32°F 62°F +30°F
Kansas City, MO 38°F 66°F +28°F
Chicago (MDW), IL 33°F 61°F +28°F
Wichita, KS 42°F 68°F +26°F
Indianapolis, IN 36°F 62°F +26°F
Oklahoma City, OK 49°F 70°F +21°F
Memphis, TN 50°F 70°F +20°F
Buffalo, NY 34°F 50°F +16°F
Mobile, AL 61°F 73°F +12°F
Sources: xmACIS2 / NWS
Extremes beget extremes. Folks east of the Rockies often have to endure relentless wintertime teasing from friends and family basking in California's mild winters. A strong ridge is usually paired with a strong trough nearby, and this ridge's companion found itself right over California on Wednesday. Chicago Midway recorded a warmer high temperature (61°F) than Los Angeles (58°F),

The ridge will slide east through the end of the week, briefly allowing more seasonable temperatures to wash across the Midwest before a ridge redevelops this weekend and pumps 50s and 60s back toward the Great Lakes. It's likely that above-average temperatures will continue across parts of the eastern U.S. through next week.

Here's a look at the National Weather Service's forecast high temperatures through Sunday.

Thursday, Dec. 26

Friday, Dec. 27

Saturday, Dec. 28

Sunday, Dec. 29

[Top Image: Tropical Tidbits]

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December 19, 2019

Those New 'Snow Squall Warnings' Are Designed To Prevent Deadly Pileup Accidents

Millions of smartphones across the Northeast flashed an unfamiliar warning on Wednesday afternoon. The message came across as a push alert with the iconic screeching tone and an abrupt vibration: "Emergency Alert. Snow squall warning until 4:15 PM. Sudden whiteouts. Icy roads. Slow down! -NWS" These alerts may seem a little excessive on first glance, but they're targeted at motorists who need to know that they're approaching a potential whiteout that could cause a deadly pileup accident like the one that occurred in Pennsylvania on Wednesday.

The National Weather Service created snow squall warnings as a way to warn people in the path of snow squalls that they could experience sudden whiteout conditions, giving them enough time to pull off the road and wait for things to calm down before driving again.
Source: NWS New York

A local NWS office can issue more than a hundred different types of watches, advisories, and warnings. Some of the products are more urgent than others. The most important warnings—the ones that require you to stop what you're doing and pay attention to the weather instead—are usually issued using polygons, which allow forecasters to target warnings to only the areas at risk for life-threatening hazards like tornadoes and severe thunderstorms.

There's a different target audience for each of those polygon-based warnings. Tornado warnings and severe thunderstorm warnings are "everyone" warnings, no matter who or where you are. Flash flood warnings are important to people who live in flood-prone areas and motorists who may approach a flooded roadway, but the vast majority of us can usually ignore them if we're going about our business at home or work.

Beginning in November 2018, the National Weather Service officially began issuing polygon-based snow squall warnings, giving forecasters the ability to instantly warn people that they could be in the path of a sudden burst of snow. Snow squall warnings are "driver" warnings. They're not targeted to people sitting in their living room or working at their cubicle. They're targeted at people on the road or those who are getting ready to head out.

Snow squall warnings are handled with the same urgency as tornado and severe thunderstorm warnings for good reason.
We hear about pileup accidents all the time during the winter. A chain-reaction crash is pretty much the worst-case scenario for anyone out on the roads when a sudden burst of snow turns the roads to ice and drops visibility down near zero. Pileups can involve hundreds of cars in the most serious incidents, amassing dozens of injuries and fatalities as people get stuck in the wreckage and absorb the blow of every car and truck careening toward them.

The warnings worked exactly as expected on Wednesday. Several snow squalls moved across portions of the Northeast today, bringing whiteout conditions and dropping up to two inches of snow in under an hour. It doesn't look like much on radar (shown at the top of the post), but the tweet above shows how abruptly a cloud of snow can drop visibility down near zero.

Unfortunately, a snow squall in central Pennsylvania actually did cause a deadly pileup on I-80 about 20 miles east of State College. The Daily Item reported that two people died and dozens more were injured during the chain-reaction crashes.

There's only so much meteorologists can do to warn people of what's on the horizon. Just like a tornado or severe thunderstorm warning, it's not always possible to pull off the road or avoid a wreck when you find yourself driving into a snow squall. The new warnings are designed to give you an opportunity to seek safety that wasn't available before. It's all worth it if each warning helps even a couple of people stay safe.

[Top Image: Gibson Ridge]

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December 16, 2019

A Quick-Hitting Storm Will Bring Midwest Snows And Severe Thunderstorms To South

A low-pressure system will develop over the Mid-South on Monday and dominate weather east of the Mississippi River for the next couple of days. The storm will start with a quick thump of snow across the Midwest and Ohio Valley, with severe thunderstorms developing in the storm's warm and humid airmass across the Deep South. Snow and ice will spread toward the Northeast on Tuesday before the storm races out to sea on Wednesday.

Wintry Weather

Winter storm warnings are in effect across central Missouri and central Illinois ahead of a period of heavy snow expected during the day on Monday. The snowfall forecast map above shows all the snowfall forecasts issued by local National Weather Service offices across the country. The NWS forecast shows up to five inches of snow across the winter storm warning, which isn't a whole lot, but it's enough to snarl traffic and make travel a headache when roads are at their worst.

Winter weather advisories exist from the central Plains to the Northeast, with more advisories and warnings likely as the storm moves east. It doesn't take much snow or ice to make travel difficult or even impossible. I've long argued that an inch of snow is more dangerous than a foot of snow, and the danger only grows when there's freezing rain, sleet, or roadway refreezing in the mix.

Severe Thunderstorms

It's not all cold and snow. Warm and humid air will rotate around the southern end of the low-pressure system, providing a decent amount of instability to fuel severe thunderstorms.

The Storm Prediction Center issued an enhanced risk for severe weather—a three out of five on the scale measuring the risk for severe thunderstorms—across portions of Louisiana, Mississippi, and Alabama, on Monday afternoon.

The greatest risk from the strongest thunderstorms is damaging wind gusts in excess of 60 MPH and the possibility for tornadoes. The threat for tornadoes appears maximized around central Louisiana and Mississippi, where the SPC painted a 10% risk for tornadoes on Monday. Tornadoes are most likely in discrete thunderstorms, while damaging wind gusts are favored in squall lines.

If you have any friends or family in the area, it's a good idea to give them a heads-up about the risk for severe thunderstorms on Monday and Monday night, especially since a decent number of the storms will roll through after sunset. Nighttime storms are dangerous both because people tune out as they wind down before bed and the fact that the urge to look for approaching storms and tornadoes can be overwhelming. Make sure you've got a way to receive severe weather warnings once you go to bed, and please trust that they're real and resist the temptation to look for the storm before seeking shelter.

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December 6, 2019

This Weekend Will See Heavy Rain In Northern California, Heavy Snow In The Sierra

A storm approaching California on Friday will produce plenty of heavy rain and snow across the northern half of the state this weekend. While the storm is nowhere near as strong as the record-breaking system we saw before Thanksgiving, which set California's all-time record low air pressure reading, it's bringing plenty of moisture ashore with it.

Unlike the system that came ashore the week of Thanksgiving, this storm will weaken as it approaches the northern California coast on Friday. Even though the approaching low-pressure system is much weaker than our previous storm, forecasters still expect the system to produce quite a bit of rain and snow through the weekend.

The latest forecast from the Weather Prediction Center shows up to five inches of rain falling across parts of northern California and southwestern Oregon, with the heaviest rain expected north of Santa Rosa. The Sierra could wind up with several feet of fresh snow by early next week, which is great news for both ski resorts and future water reserves.

It's also going to get windy. Coastal counties in central California could see wind gusts of 50 MPH as the storm comes ashore on Friday and Saturday, which could lead to (nature-induced) power outages and tree damage. Make sure you're prepared for a power outage—of course you are, thanks PG&E!—and stay mindful of large trees and tree limbs over your home/vehicle/smoking spot/what have you.

Flight delays are likely at SFO and other northern California airports over the next couple of days as pilots and air traffic controllers deal with rain, low ceilings, and gusty winds. Any delays or cancellations will cause a ripple effect of delays and cancellations down the line, as any slip in the schedule will affect all of an aircraft's future scheduled legs.

It's also worth noting that flash flood watches are in effect for the burn scar left by the Kincade Fire in northern Sonoma County, including areas downstream from the burned land. It's exceptionally difficult for rainwater to permeate soil burned by wildfires, forcing much of the rain to simply run off as if it had fallen on an asphalt parking lot. Debris flows are also common on and around burn scars in hilly areas as a result of fires destroying the vegetation that held the soil together.

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