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Heavy rain caused localized flooding

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The sun is shining! After the amount of rain that has fallen across the area since Saturday, it will take a while to dry things out across the state. While this particular rain event wasn’t historic or record-breaking, it was serious and damaging to many low-lying spots around the Triangle.

satellite image

Satellite image of low pressure circulating over North Carolina the morning of April 25, 2017

I was asked what caused such massive amounts of precipitation over the last few days, and here is the simple, short-term answer: Saturday through Sunday, we saw a frontal system pass bringing the first round of rain. Almost right on its heels, a slow-moving low pressure system that developed over the Deep South arrived and creeped across North Carolina. Drawing moisture from the ocean, it had a large amount available to dump on much of the state.

This isn’t the first time a situation like this has occurred, and it won’t be the last. In fact, we should probably be grateful that it’s not January — at least, those of us who aren’t fans of snow. Instead of snow drifts, we are dealing with the aftermath of localized flooding. Maybe that’s not much better, but the higher elevations recover and get back to business quicker after a heavy rain than after a heavy snow. The lower elevations may take a bit more time.

One infamous low-lying area in Wake County is Crabtree Creek near Highway 70/Glenwood Avenue, which is home to Crabtree Valley Mall. Anyone who has lived around here for any length of time knows that when we see four-plus inches of rain fall in a short period, Crabtree Valley is probably going to flood.

Crabtree Creek water level

Graph of water level of Crabtree Creek at Highway 70 in Raleigh during April 22-24 extreme rain event

The mall opened in 1972, and the first historic peak discharge listed at the Crabtree Creek and Highway 70 gauge operated by the U.S. Geological Survey is listed as June 29, 1973. I found it odd that the next peak flow listed wasn’t until 1996, so I inquired about the history of that station.

According to Doug Smith at the USGS Raleigh office, that gauging station “was operated as a partial record site and a few flow measurements were made at the site beginning in 1972. There were no continuous data collected at that site before February 1988.” There have been at least 10 flood-level or above-peak stream flow events at that gauge since September 6, 1996 (Hurricane Fran).

What contributes to Crabtree’s flooding issues? First and most obviously is that it is a low point in the geography of Raleigh. Second, the amount of urban development surrounding it has grown exponentially over the decades. The more impervious the surfaces created around the creek, the faster precipitation flows directly into the creek leading to faster water level rise and flash flooding. Concrete, asphalt, and buildings surrounding a creek with very little open green space and absorbant soil to slow the flow are a major cause of Crabtree Valley’s troubles.

Another potential factor there and elsewhere is storm drain blockages. When you see areas that don’t often flood, or those that do, flood more quickly, it’s quite possible that nearby storm drains are unable to do their jobs. Storm drains should divert the flow of water away from roads and into locations where the water can safely collect and eventually disperse. Precipitation that falls too fast for the storm drains to do their jobs is a possibility, but another is blockages caused by debris and litter. A simple rule of living with storm drains: don’t put anything down there except storm water. That water flows to streams which flow to rivers which flow to the ocean. Those drains need to be kept clean for that reason at the very least.

Some people would attribute rain events like this one to climate change, and they might be partially right. I have written here before about studies that point to a warming climate as a cause for extreme rain events. Below are links to a couple of relatively recent stories about two such studies. There is no question that climate models predict dramatic warming and related weather events such as heavy single-day rainfall, prolonged drought, and temperature extremes. I would be remiss if I did not acknowledge the documented questions about the accuracy of the climate models and such predictions and their potential fallacies.

Whether flooding is caused by poor choices in urban development, blocked storm drains, slow moving low pressure systems, or climate change, we need do what we can to mitigate the risk. There are some things we have no control over such as the weather. Other things we have pretty good control over include storm drains and choosing to use pervious materials in and around urban development. Considering storm water runoff when deciding where to build both residential and commercial developments can help avoid issues like those faced by our neighbors along Crabtree Creek in Raleigh.

We can’t go back in time and rethink where to put that mall, but we can avoid repeating that developer’s mistake.


Additonal reading not included in the hyperlinks above:

“Study finds more extreme storms ahead for California”

“Extreme downpours could increase fivefold across parts of the U.S.”

Weather Blog

Wow! What happened with that forecast?

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My print forecast in the Wake Weekly made a lot of sense on Wednesday morning when I wrote it. I thought I might have been a little optimistic about Sunday’s forecast high in the mid to upper 70s. I know my personal bias is caused by my preference for warmer temperatures. However, I didn’t expect my forecast and that of the models I used for it on Wednesday morning to be so drastically different from reality.

The forecast for Saturday was for partly to mostly cloudy skies, a high in the upper 70s, and a chance for showers and thunderstorms with the possibilty that a few storms could be strong to severe. It looked to me like the cold front and its rain would approach early Saturday evening and bring those storms with it.

rain total map

Map of the 24-hour rain totals over central North Carolina from 8am, April 23, to 8am, April 24, 2017 courtesy of the National Weather Service Raleigh Office.

What happened Saturday was a bit surprising – the front stalled in Virginia, the sun shone here, and the temperature at RDU International Airport reached 87 degrees! I doubt anyone was too angry over a sunnier reality on a Saturday filled with outdoor events across the area. I know I wasn’t. Well, I was not thrilled that the forecast busted, but I was happy with the nicer weather.

The severe weather Saturday evening was mostly constrained to just north of the Virgina border where the stalled frontal boundary sat. By the time it started moving south, the atmosphere had cooled and lost its instability, which led to more rain and less thunder.

My forecast busted on the cool side yesterday. I had predicted a rainy day, but the rain and the winds from the east kept the temperature 20 degrees cooler than it looked like it would be several days before.

As I beat myself up a bit over the way my printed forecast did not verify, a friend pointed out to me, “Most people don’t expect weather people to be right. They just want some guidance on what to expect for the next few days.” He told me that he appreciated my personal need to be accurate, but he didn’t think accuracy was all that expected.

While I appreciate his sympathetic thoughs, I disagree. Accuracy should be expected. Maybe not on a weekend like this recent one — when the speed of a cold front’s movements ultimately determined the temperatures over two days and there was not a huge amount of confidence in the models three days in advance — but it should be expected.

Meteorologists’ accuracy over the long term is what gains the public’s trust. Without that trust, we can’t expect them to take us seriously when we forecast a chance for severe weather or a winter storm or a hurricane making landfall several days out. While most of the time we are actually right, it’s those times that we are not that the public seems to recall most. It’s human nature, and it is something we have to work hard to overcome — both as forecasters and as humans.

The best way for a forecaster to improve is to spend time picking apart a forecast that didn’t verify and figuring out what happened. Sometimes, there is not much to blame other than the very models we rely on to make the forecasts. Other times, we can see trends in hindsight that we should have recognized in advance. So, that is why this morning, I asked myself the question that I expected to receive from my readers. “What happened with the forecast?”

Weather Blog

Seeing a storm from many angles highlights technology

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GOES-16, also known as GOES-R, is the satellite that was launched in November of last year, and although it is still in the testing phase, it is already showing exciting images. “GOES” stands for Geostationary Operational Environmental Satellite. GOES-16 is one of many satellites, as the number implies, tasked with orbiting the earth and transmitting information about the atmosphere for severe weather tracking, space weather monitoring, and weather forecasting and research.

SPC Storm Reports

Storm Prediction Center Preliminary Reports from April 14, 2017 including Dimmit, TX, tornado sightings.

So far, we have seen some pretty impressive, high resolution images from the new satellite. On Friday, for example, it captured the development and lifespan of a storm that originated on the border between New Mexico and Texas that spawned multiple tornadoes.

On the satellite loop, you can see the overshooting tops of the tornadic supercell — the parts of the cloud that push through the tropopause and up into the stratosphere — showing an extremely potent updraft around which the tornadoes form.

Combining the satellite imagery with radar returns and ground confirmation from Skywarn spotters and storm chasers, meteorologists knew exactly what they were dealing with in that storm. The ability to see a thunderstorm from three different angles in real time is invaluable and amazing. Think about the advances in technology required in the last century for us to be able to track a severe thunderstorm from space, from a stationary point on the ground miles away, and to live-stream a chase feed from an automobile on the internet!

Instead of hearing about a tornado after the damage has been done, we are able to forecast a severe weather outbreak days in advance, warn that a storm may produce a tornado before it does, and confirm a tornado is on the ground at the moment it is witnessed touching down.

If you want to see two of the angles of this particular storm and geek out a bit like I did, check out the Satellite Liaison Blog from GOES-R and JPSS and then search Youtube for the Dimmitt, Texas, April 14, 2017 tornado. A word of warning before viewing chaser videos, sometime the language can be a bit much for children. (Imagine what you might say at the moment you see a tornado touch down.)

Weather Blog

Tornadoes and manufactured homes: an unfortunate combination

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In response to my blog post about tornadoes and sociology shared on Facebook a few weeks ago, Pamela P. said:

When it comes to tornados, I always wish we had sirens. But because that’s not feasible, at the very least they should be installed in every trailer park, along with a storm cellar. Most people of a certain income can be warned through news, social media, cell phones, radio, etc. However, those who live in the flimsiest of housing have the most to fear (trailer parks are always decimated in a tornado), and they are also the hardest to warn. They may not have access to any of the devices mentioned above, and they have a higher chance of not speaking English. Why not pass a law requiring a siren and a storm shelter in every trailer park? Those are just my thoughts. Thanks!

destroyed mobile home

National Weather Service photo: Mobile home in Henry County, Alabama, was flipped and destroyed by an EF-1 tornado while residents took shelter in a near by home.

I agree, Pamela! I have always thought sirens and storm shelters should be required for manufactured housing communities. Truly, I wish there were a safer option in affordable housing for those who live there. Manufactured homes are unsafe in tornadoes, and as importantly, they are unsafe in high-speed straight-line winds as well because they roll easily. So, severe thunderstorms with 70 to 80 mph winds can be just as dangerous to people who live in mobile homes.

A weak tornado of the Enhanced Fujita Scale category of one (EF-1) with 86 to 110 mph winds can push mobile homes off their foundations or completely overturn them. An EF-2 with winds of 111 to 135 mph can demolish one completely. In contrast, an EF-1 tornado would damage roofs of frame houses, and an EF-2 could tear roofs completely off, yet the majority of the structures would still remain intact — assuming they were built sturdily and to code.

So far this year, of the 27 fatalities caused by tornadoes, 17 have been in manufactured houses, seven have been in stick-built houses, two have been outside, and one was inside a vehicle. These numbers are tragic and far too high to begin with, and when you think about how having a reliable hyperlocal warning system and safe, sturdy shelter may have helped save even a couple of them, the situation is even sadder.

Now, I am not saying that I know the situation in each fatality location. Maybe the people received the warnings and chose not to act upon them — that does happen sometimes. Typically though, I choose to believe that when given an urgent, timely warning, if there is a safe place to go, people will wisely opt to shelter there.

Weather Blog

Whispers, marches, and science

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I’m not marching for science on April 22. I think it’s a waste of time, energy, and somewhat hypocrytical.

March meme

Meme posted on the Facebook page “March for Science” on March 31, 2017

The Facebook page “March for Science” posted the meme to the right. “Science is unbound by borders, working at its best when ideas flow freely among peoples and nations,” is a beautiful thought, but it’s not reality, and President Trump is not to blame for that fact. The squelching of scientific free speech came long before he took office, and it came from within the scientific community itself.

Let me comment on one issue I am aware of personally, although I’m sure it is just one of many — the issue of the mythological climate consensus. (Oh, I’m in trouble now, aren’t I?)

The pursuit of science is the pursuit of knowledge by observation, creation of hypotheses, testing of hypotheses, more observation, and tweaking of hypotheses, etc. It is a cyclical process. Only when a hypothesis has been tested over and over in ways that are replicable and it is strenthened by replication can that hypothesis graduate to status of theory. Even theories can eventually be proven incorrect.

Somehow the idea that climate change is caused by an increase in carbon dioxide in the atmosphere has been elevated beyond theory to some new belief system that is not allowed to be questioned. Anyone who proposes an alternate hypothesis or questions the quality of the data and experiments gets blacklisted, name-called, and pushed to the back of the bus, or worse, pushed off the bus altogether — figuratively speaking, of course. How is this behavior by other scientists exemplary a free exchange of ideas?

Many of us who are willing to look into potential alternative causes of climate change speak quietly amongst ourselves in hushed tones because we fear the kind of vehement judgement that our more outspoken counterparts have faced. One example is Judith Curry who testified in front of the House Science Committee on March 29. Here is the link to her oral comments in her own words. If you weren’t aware that some scientists question the consensus, reading her statement might prove quite enlightening.

Personally, I like to read everything I can find about alternative explanations to most super-popular theories because I am proud to be a scientist in the truest sense of the word. I like to keep an open mind, and it would be wonderful if those of us who do could speak above a whisper when we meet.

Weather Blog

Radar images are just snapshots in time

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As I prepared for work this morning, I glanced at the radar and saw a number of signs in a single image that let me know I could be in for a rough commute. The screen, a snapshot of which is to the right, showed that a gust front had just passed my part of North Raleigh, a heavy rain shower was moving toward my house, and a large area of rain was heading into the Triangle.

radar image

A screenshot of the radar image at 6:19 A.M. on Tuesday, March 28, 2017.

I set my phone with its radar app back down and rushed to get out the door before that heavy rainshower hit, but it never did. The shower dissapated, or rained itself out, before it made it to my neighborhood. The large blob of rain behind it developed holes and weakened into lighter showers. The next time I looked at the radar, about 20 minutes after the first, I saw a very different situation. That’s how it goes with the radar.

Any time someone asks me if it’s raining, I follow my answer with the obligatory “right now,” because a radar image is just a snapshot in time. Just like any photograph, it shows the situation at that moment whether that be rain, hail, high winds, rotating winds, or nothing at all.

Doppler radars take four to six minutes to complete a full scan, so the image takes four to six minutes to update. A lot can happen between updates. Tornadoes can form, hail can fall, rain can begin, snow can end, etc. What you see at that moment is what the radar saw in the last sweep.

Radar is a tool for nowcasting and very short-term forecasting at best — a highly important and effective tool. Without radar, we would be utterly dependent upon people on the ground reporting tornadoes, and by the time those reports were disseminated and the public was alerted, the damage would already be done. It wasn’t long ago when that was the case –merely decades.

With Doppler radar, we can see velocity signatures that indicate rotation in storms before a funnel even develops. Our warning time for most storms has greatly improved, and tornado warnings for long-lived, slow-moving storms may even be 45 minutes to an hour in advance of the storm’s arrival at a point on the map. That’s pretty impressive when you think about it!

What about those moments when storms are forming faster than the radar can keep up? Those are the times when it is extremely important to take it upon yourself to pay attention to weather watches and warnings and to look at the sky. Your own eyes on the horizon are invaluable to your safety. If you see a rotating wall cloud, green clouds, lightning, or the effects of strong winds, don’t wait for a warning to be issued. Take shelter.

A rotating wall cloud is a lowering of the cloud base that is rotating around a vertical axis, and it is a sign that a storm could produce a tornado at any moment. Greenish-tinted clouds tend to signal that there could be hail or very large raindrops inside. Lightning is a danger if thunder is close enough to be heard. Strong winds can kick up debris and do as much damage as a weak tornado. All of these things could develop quickly, and being weather aware could be the one thing that saves your life. It sounds rather dramatic, but it’s true.

As we head into one of our busiest storm seasons of the year, practice safe weather watching. Watch the radar and look at the sky to stay truly weather aware.


Weather Blog

Best practices for gathering weather information

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In January, the American Meteorological Society adopted a statement called “Best Practices for Publicly Sharing Weather Information Via Social Media.” It is basically a how-to for meteorologists who are doing their best to use digital platforms such as Facebook and Twitter to share forecasts and explain complicated topics in what are typically short-format media.

For some of us, the guidelines are common sense. Others really needed to read them. Social media usage doesn’t come naturally to everyone.

The rub for me is that communication is, or at least should be, a two-way street. We can responsibly put the information out there for the public to find, but the public needs to be smart about consuming it, too. I remind my colleagues pretty often that you can lead a horse to water, but you can’t make him drink – or if he does drink, is he drinking responsibly? Okay… maybe that’s not the best analogy since it’s water, but you get my point.

There are a few things you can do as a consumer of weather information that will help ensure that you are getting accurate weather information in a timely manner.

Screen capture of snow over Scranton, PA, on radar. There is a time stamp, but no date, which may lead to confusion if viewed and shared on social media on a different date.

1. Check the time stamp, especially on social media.

I’ll use Facebook as an example since it is the platform with which I am most comfortable, and I use it the most. Facebook’s news feed algorithms default to “most popular news,” which doesn’t necessarily mean the most recent. Even if you choose to use the “most recent” option, it ranks recency by what has the most recent comments. I can look at my feed right now, and a Yankee cousin’s story about a grocery store run prior to the blizzard from yesterday is second on my feed this morning because someone just commented on it. It’s not a new story, but it’s at the top of my “most recent” feed right now. If you don’t know how the feed works, it will just add to confusion during a time-sensitive event.

2. Have more than one reliable source for weather information.

I have good friends whose loyalty I totally appreciate, but it worries me when they say they wait until they see my weather posts before they act on weather information. You have no idea how good that makes me feel on one hand, but on the other — YIKES! What will happen on the days when I’m unplugged, in long meetings without the ability to look at my radar, or suffering the same power outage as the rest of the area? That’s a lot of pressure and expectation for one person. Sure, when we can afford a whole team of meteorologists to make around the clock forecasts and updates, I’ll feel more at ease, but right now, I am flying solo and begging them to follow other resources, too!

3. Understand that 140 characters or less makes communicating complicated science a challenge, and that one post may mean there are more posts before and after it.

If you’re following thousands of people on Twitter, those posts will get lost in the feed. No matter how careful a meteorologist is about putting all the information out there, we have no control over how the platform disseminates it.

4. Don’t only use social media to get your weather information.

Bookmark your favorite forecaster’s website; look at your local National Weather Service Office’s site. Have a radar app on your smart phone. Buy a NOAA weather radio. There are multiple ways to get reliable information, and using just one leaves you open to missing out.

In recent years, meteorologists as a group have put a lot of thought into how we communicate weather information. We are partnering with social scientists and psychologists on studies of how people best understand things like precipitation probabilities, the best wording for storm warnings to be taken seriously, and even the colors we use on our weather maps and graphics. The more we understand, the better we are becoming at putting useful information out there, but we can’t do it all ourselves. You have to participate in the process, too, in a smart and savvy way.

Weather Blog

Resilience and adaptation are necessary in any climate.

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It doesn’t matter to me which side of the conversation you land on when discussing whether or not the climate is currently changing faster under post-industrialized human influence. It really doesn’t. I have read enough from scientists on both sides to understand each side’s perspective and some of the possible alternative explanations for the current warming trend. I’ve also read enough to know that there will always be more to read, so don’t think I know it all. I would never make that claim.

I will, however, not have to stick my neck out too far to say that there are two things that humans have always been pretty good at — well, most humans anyway — and those are resilience and adaptation. The few societies in the past who were not are the very ones that are the subjects of speculative documentaries based on geological, archaeological, and anthropological findings. Did the Minoans disappear because they were weakened by famine caused by a huge volcanic eruption and fell victims to rival societies? Did the Mayans disappear because they over-forested their land causing drought and driving their populations back into the coastal areas where water and food were more plentiful?

There are a number of ancient societies that arose and fell under sudden and mysterious circumstances — giving even the most unusual hypothesis a tinge of credibility. I mean, I’m not saying it was aliens, but…

Sorry. I couldn’t resist.

ancient sea level

From NC DEQ. Historic northeastern N.C. shoreline, 125,000 years ago. Image credit: Peter Parham, 2007.

A fact of history — and even prehistory — is that the climate changes. Sea levels rise and fall. The atmosphere warms and cools. Volcanoes erupt, continents move, and on extremely rare occasion, giant space rocks wreak havoc by falling on our little blue planet. Assuming that the latter doesn’t totally destroy us all, we adapt, we move, we develop new technologies, and we survive.

One other thing we do: we plan.

Learning from the past helps us to plan for the future. Scientists and engineers discover and develop new ways to understand the world around us and enhance how we interact with it. That newly found knowledge and those break-through technologies can be used to mitigate our risk and build our resilience in an ever-changing world.

Some articles and research that I have read recently have rejuvenated my optimism about facing the future — not just personally, but on a societal scale.  Two examples: a Durham company invested in technology that had not even been proven yet, but is now being tested, for a power plant to be able to capture and reuse all of its carbon dioxide emissions. A Native American tribe in the desert southwest is already adapting to a warmer and drier climate while at the same time improving access to healthy food for its people.

What makes these two stories stand out to me today is the amount of acumen and ingenuity required to see those ideas through to actualities.

It takes vision and planning to come up with new ways to deal with a changing environment. It takes open-mindedness and understanding to see other people’s visions and dreams and to help make the ones that are built on solid foundations become realities. It takes a whole community’s effort to be resilient — meaning it takes scientists, engineers, public officials, planners, neighbors, and you.

Weather Blog

Does your home have a safe room?

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If you’re paying attention to any number of local meteorologists, you probably already know this week is North Carolina’s Severe Weather Preparedness Week. It happens every year near the beginning of climatological spring, also known as March. The state declares a special week in which to focus on preparing for the natural disasters that are most likely to occur here — severe thunderstorms, hail, lightning, flooding, tornadoes… you get the idea.

For me, the most important thing about this annual event is encouraging people to be more situationally aware. Knowing your surroundings is always key to being safe in potentially dangerous situations.

tornado damage

Image of damage from Lone Grove, OK, February 2009. Notice the closet is intact and clothes are still on hangers inside.

Ask yourself, if a tornado were coming my way right now, where would I go? Knowing that “outside to watch it” is not necessarily the best and definitely not the safest answer, let’s look at our options. Does your home or office have a safe room? My guess is that if you define a safe room as a place to hide from Hollywood villains, the answer is probably “no.” While a constructed safe room is actually an option, for the purpose of this discussion, a “safe room” is one that you can enter quickly in the event of an emergency. It should be in the lowest level of the building and an interior room away from windows and exterior walls. This could be a basement, a closet under the stairs, or bathroom as long as it fits the “lowest interior” room qualifications.

Safe rooms aren’t necessarily just for hiding out from tornadoes. Some severe thunderstorms include dangerous straight-line winds that can be as much of a threat as rotating winds. For this reason, severe thunderstorm warnings will often tell you to stay away from windows because flying debris caused by straight-line winds can do as much damage as tornado debris when encountering glass.

In the Midwest, large hail is another reason to stay away from windows because hail there can be as big as softballs, or larger, in their worst severe storms. Our hail tends to be smaller than golf balls here in North Carolina, but never say “never” when it comes to the weather. If we had a freak storm with softball-sized hail, you would definitely be told to stay away from windows.

Think about your home, your work place, the mall, or your favorite restaurant. Where would you go in the event of a tornado warning? How about the the dog park, a nature trail, or the soccer fields? Is there a building nearby that could hold everyone? Each place is going to have a different answer, and in some locations, the answer may simply be “no.” For this reason, weather awareness and situational awareness go hand-in-hand.

Wednesday at 9:30 a.m., there will be a statewide tornado drill, and while your office might not actively participate, you can virtually participate. All you have to do is take a minute at that moment and answer the question, “where would I go if a tornado were bearing down on me right now?” If you want to take it a step further, don’t wait until that moment. Keep it top of mind every time you visit a new place. I do.

Weather Blog

Thoughts on Bill Paxton, chasers, spotters, and a risk for severe weather

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It’s rare that I shed a tear over the passing of an actor, but yesterday, I did when I learned of Bill Paxton’s sudden death. There was shock, sadness, and the realization of how much the man influenced so many of my friends by portraying a meteorologist doing his best to catch a tornado without becoming a victim of it. The character was everything budding meteorologists wanted to be — brave, tenacious, and just crazy enough to do it.

‘Twister” came out in 1996, which was the year that I graduated with my mass communication degree and the year that I realized I should have gotten a meteorology degree. An elective meteorology course for non-science majors that last semester at N. C. State University gets the credit for that realization, but the movie just added to my intense fascination with tornadoes and severe storms. Despite all the editing flaws and some occasionally iffy science, it wasn’t long before I had every line memorized.

When I returned to NCSU at the age of 30, I quickly learned that my younger atmospheric science course classmates also knew every word of that movie. An entire generation of meteorologists felt the same love for Bill Paxton’s character that I did. Some of those students went on to take part in Vortex 2 — a real life research project in 2009 and 2010 with the goal of using instrumentation to gain a better understanding of why some severe storms produce tornadoes and some don’t. They got to live the dream that “Twister” portrayed in its Hollywood style without quite so many overly risky decisions. For example, driving through  a tornado-tossed farm house and exploding gas tanker might not look quite as good on a research report or resume as it did on the big screen even if that opportunity had presented itself.

When I worked at Weather Eye Radio Network in Minnesota, I had the opportunity to become a Skywarn spotter trainer as well as attend the Minnesota Skywarn Workshop. I met a number of fellow storm enthusiasts, and I learned how to train people to recognize parts of severe storms from a safe distance and call helpful storm reports in to the National Weather Service. At the workshop, I listened to storm chasers tell their stories, NWS employees explain how they categorize tornadoes based on damage, and statisticians explain some of the data behind what we knew so far about tornadoes.

I thank John Wetter for putting so much of his heart and soul into educating and training spotters and chasers.  John runs the Minnesota Skywarn Workshop and is the president of the Spotter Network – a group that gained national attention yesterday when they organized a heartfelt tribute to Bill Paxton by spelling out his initials on the map using gps coordinates. It was a fitting and touching tribute to the “Twister” star.

I’ve written before in a different blog about how Skywarn spotters save lives by helping provide ground truth to the National Weather Service’s severe thunderstorm and tornado warnings. Severe storm researchers and serious storm chasers should get credit as well. Every bit of video and data that they glean from a successful chase or instrument reading adds to our understanding of how and why storms form and tornadoes occur. We still have a long way to go toward complete understanding of why some storms produce tornadoes and some do not, but we get a little closer every year.

SPC day 3 outlook

The Storm Prediction Center’s convective outlook map shows a slight risk for severe weather over much of North Carolina on Wednesday.

On Wednesday, our local Skywarn spotters may have a chance to put their skills to use here in North Carolina. The Storm Prediction Center has already predicted a slight risk for severe thunderstorms over much of the state with a 15% chance of severe weather within 25 miles of any point highlighted in yellow on the map to the right. A slight risk usually means that someone in the area will experience a short-lived, isolated intense severe thunderstorm, but there just won’t be a lot of severe storms over the whole region.

What makes a storm severe? A storm reaches the severe threshold when it has winds in excess of 58 miles per hour, one-inch in diameter (quarter-sized) hail, and/or a tornado. So, by definition a tornadic storm is severe, but not all severe storms are tornadic — hence, the amount of research that is poured into why and how tornadoes form.