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Weather Blog

Severe weather season is in full swing!

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This past weekend brought our first truly widespread severe weather outbreak of the year. On Saturday and Sunday, April 13 and 14, a vigorous system delivered storms from central Texas to eastern Massachusetts. Damage ranged from limbs down to homes and businesses destroyed. Three fatalities and twenty-six injuries were reported according to the filtered storm reports on the Storm Prediction Center’s website, as well as 56 tornadoes, 548 straight-line wind and 22 hail reports.

Here in North Carolina, Sunday brought the worst damage, much of it during the late-night hours. Many people arrived at work Monday morning with tired eyes and the need for an extra cup of coffee. Some complained that weather alerts woke them while others complained they never received any. Truly, the most reliable way to receive emergency alerts for your specific county is still via NOAA weather radio. Mine did not fail, much to my delight and my cat’s dismay.

April tends to be one of the worst months for North Carolina with respect to severe weather. As an example of the kinds of severe weather we have had in past years, today is the eighth anniversary of the April 16, 2011 tornado outbreak that included the Sanford-Raleigh tornado and the Fayetteville-Smithfield tornado, which were each attributed with more than 100 injuries. Both of which were also long-track tornadoes that traveled over 55 miles each. That day, a total of 24 people lost their lives and more than 400 were injured.

As we look ahead to this coming Easter weekend, pay attention to the weather on Friday. Last Saturday, the Storm Prediction Center had already marked Good Friday as the East Coast’s next good chance for organized severe thunderstorms. As the day approaches, the outlook map for it has not changed much. It’s unusual to have 7-days of advance warning on the Outlook maps, and it means that the upper levels of the atmosphere in the forecasting models have been consistently showing the ingredients for severe weather for days.

The closer Friday gets, the better grasp forecasters will have on the timing of the storms. They’ll also be able to narrow down the region of concern – if it does narrow – with each model update. The good news is the worst should be over by Saturday morning, and by Easter Sunday, high pressure will bring sunshine and spring temperatures.

April 13, 2019 SR map

Graphic courtesy of The Storm Prediction Center shows the filtered storm reports for Saturday, April 13, 2019.

April 14, 2019 sr map

Graphic courtesy of The Storm Prediction Center shows the filtered storm reports for Sunday, April 14, 2019.

Saturday day1 outlook

Graphic courtesy of the Storm Prediction Center shows the severe storm outlook for Saturday, April 13, 2019, as of that morning.

Saturday day2 map

Graphic courtesy of the Storm Prediction Center shows the severe weather outlook for Sunday, April 14, 2019, as of the prior Saturday morning.

Day7 outlook map

Graphic courtesy of the Storm Prediction Center shows the Day 7 Outlook for Friday, April 19, 2019, as it was posted last Saturday morning.

SPC April 16, 2019, day 4 map

Graphic courtesy of the Storm Prediction Center shows Friday, April 19, 2019 as of this morning (April 16). You’ll notice the outline hasn’t changed very much since Saturday.

Weather Blog

Cooler temperatures limit severe weather

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Scientists at the University of Alabama at Huntsville recently released their analysis of the global temperatures in March. The map shows how the temperatures in the lower troposphere – the layer of the atmosphere closest to the ground – compared to seasonal norms. The blue tones represent cooler-than-average temperatures, and the yellow and orange tones represent warmer-than-average temperatures.

The light blue draped from the west coast to the northeast coast of the United States should not be too surprising to most of us. Much of the month was on the cool side, and in the Northern Plains and Upper Midwest, it was downright wintry. While most of us spent the month looking forward to warmer weather and outdoor spring activities, those that despise severe weather might not have minded the prolonged chill.

Severe storms require a great amount of energy to get going, and warmth equals energy. When forecasting thunderstorms, meteorologists look at something called CAPE, which stands for Convective Available Potential Energy. It’s one of the measurements that tell us how unstable the atmosphere may be on a particular day. Usually, in order to see the greatest amount of instability and have the best chance for storms, we need to surpass a certain temperature at the ground level. So, the warmer the surface temperature gets, the more likely we’ll see thunderstorms develop.

There are other factors in thunderstorm development, and even more for severe storms to develop, which I’ll save for future posts. My point here is to say that the cooler temperatures across much of the country during March, with the exception of the deep southern and southeastern states, kept severe weather at bay.

As we head into April, it’s likely that we’ll start to see an uptick in thunderstorm potential. The Climate Prediction Center is forecasting above-average chances for the temperatures across most of the nation to be above normal. While I don’t always agree with its predictions, I don’t see much reason to doubt this one.

As a point of reference, today’s average high temperature at RDU International Airport is 69 degrees, and today’s average low is 45.

Weather Blog

Weather data unfiltered by human memory

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“Ugh! This winter was so cold!” That’s what my brain says anyway. It’s no secret that I’m not a fan of winter weather. So, when you ask me what I thought of this past winter, my reflexive answer is to focus on the historic snow storm in early December and the ridiculous cold snap (but not as ridiculous as last year) in January.

The crazy thing is that I know I’m wrong.

I understand that I see winter through a filter because that’s what humans do. Each of us has our own personal way of filtering the information we receive from the world around us, which in turn affects how we think about the world we experience. In fact, we usually have more than one. I have a filter for winter. I have a filter for how I assess people. I have a filter for how I decide what new information I want to understand or ignore. Sometimes, I have to remind myself that I’m using my filter again.

For example, this winter wasn’t that cold despite what my filter wants me to believe. In fact, according to the Quarterly Climate Impacts and Outlook published by the Southeast Regional Climate Center earlier this month, the region had its ninth warmest winter on record. The report says the following:

“While daytime maximum temperatures were near normal for most of the region, nighttime minimum temperatures were much above normal; in fact, every state in the region was ranked in the top tenth warmest minimum temperatures for 1895-2018. This was due in part to plumes of moisture streaming northward from the Gulf of Mexico, producing many clouds and much rainfall (4th wettest winter on record for the Southeast).”

You might be asking yourself what plumes of moisture have to do with warmer minimum temperatures. The more moisture the atmosphere contains, the higher the dewpoint. As a general rule, the actual air temperature cannot go below the dew point. So, more moisture in the air leads to higher minimum temperatures.

On a larger, national scale, many people are claiming that the colder weather across the middle of the country this year is proof that the earth isn’t warming. Their filter seems to be that if it didn’t happen in their backyard, it just didn’t happen. However, if you look at the global temperature maps for the winter, you’ll see that with the exceptions of a few places in the world, it was warmer than normal overall.

NCEI temperature map

The NCEI January 2019 temperature anomaly map shows warmer-than-normal temperatures in shades of red and cooler-than-normal temperatures in shade of blue.

Take January for example. The map from the National Centers for Environmental Information shows the eastern halves of the United States and Canada were near average with respect to temperature for the month. Parts of the southeastern Pacific Ocean and the waters off the coast of western Australia and southeastern Greenland were all cooler than average. However, much of the rest of the world registered in the above-average range.

Our filters taint our memories of weather, be it for a day, a season, or a year. If you want to know to how accurate your memory is, you can use the official records to verify it. The National Weather Service records daily almanac data at all their major reporting stations. While not every town has official records, most are located near enough to a reporting station to be pretty accurate for the purpose of answering questions like “Wasn’t that the coldest year that decade?” or “Didn’t it rain more than usual that spring?”

The information is out there. It just takes a few minutes to find it. Your tax dollars pay for the service, and the records are available online. So, there’s no real excuse to rely on memory if you have a question that needs an accurate answer.

Weather Blog

Welcome, Spring!

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Wednesday, March 20, is the Spring Equinox. The days are getting longer. The ground and lakes are slowly warming, and thankfully, our yards have gotten a chance to dry out after a year of higher than average rainfall.

This week’s temperatures so far have been a bit lower than normal – as defined by the 30-year average from 1981 to 2010. For example, today’s average high temperature at Raleigh-Durham International Airport is 64 degrees and the average low is 41. At Fayetteville Regional Airport, those numbers are 67 and 42, respectively.

Of course, it’s actually rare that we experience exactly average temperatures, so it surprises me when people talk as if that’s what it takes to experience a season. Typically, it’s a little cooler than normal or a little warmer than normal. In fact, spring and autumn are transitional seasons, which means we ride a roller coaster of temperatures with some wild swings between the two for a few weeks.

As we head toward the weekend, our afternoon highs will creep up toward normal. By Sunday and Monday, they could be in the 70s. Then, if you believe the extended forecast from the GFS model, the bottom could drop out on Tuesday and Wednesday with January-like temperatures. Personally, I’m not sure I buy into the 30s and 40s for highs this late in March, but it’s not impossible. My expectation (and hope) is that the model will moderate those days as we get a little closer to them.

Even if the extreme temperatures hold true for Tuesday and Wednesday, by the following weekend, the afternoon highs should easily be back to the normal or above-normal range. In fact, the Climate Prediction Center is forecasting a good chance for above-average temperatures for the rest of March, April, and May. With an El Nino in full effect now, I see no reason to disagree with that forecast.

CPC MAM map

The Climate Prediction Center‘s temperature outlook map for March, April, and May shows above-average chances for above-normal temperatures during the period.

Weather Blog

Severe weather preparedness: Tornadoes

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Do you recall learning about tornadoes in elementary school? I do. In Mississippi, we were taught the basics: tornadic storms form when warm, moist air from the Gulf of Mexico clashes with cold, dry air crossing the Rockies. That information was pretty accurate when my whole world consisted of the town in which I lived. Knowing what I know now, it wasn’t wrong, but it wasn’t totally right either.

Tornadoes can occur anywhere, which means the Gulf of Mexico and the Rocky Mountains are not required for their formation. What is required is a battle zone between two conflicting air masses. Warm, moist air and cooler, drier air are definitely needed. The bigger the difference between them, the stronger the frontal system.

Rotation in the atmosphere is also needed to spin up a twister. Not every strong cold front will spawn tornadic storms. All the right pieces have to be in place.

We’re still in the process of learning exactly why some storms with all the right ingredients will produce tornadoes and some will not. For the longest time, we thought they all reached down from the base of a supercell cloud. Last year, a study discerned that at least some tornadoes may form from the ground up. Each year brings new data and hopefully a better understanding of why twisters happen.

The good news is with each little increase in knowledge, we are getting better at forecasting potential severe weather days. It used to be that we couldn’t be very accurate more than three days in advance. Now, we can see the potential for severe weather up to eight days out. As with any forecast, the closer we get to the day of the storm, the more precise we can be about when and where the battle zone will be.

SPC 5-Day outlook

The Storm Prediction Center’s 5-day Outlook shows a 15% risk for severe weather in the highlighted region from Sunday morning through Monday morning (3/10-3/11/19)

Yesterday, while looking at the Storm Prediction Center website, I noted there was already a region highlighted with a 15% risk for severe weather five days out – Saturday morning through Sunday morning. The map wasn’t a surprise to me after having made the forecast for the weekend. I could see the setup for a strong frontal system to cross the Midwest and the south during that period. Seeing that risk highlighted was actually a small point of pride in our science. We’re getting better at this!

Today, the five-day outlook is for Sunday morning through Monday morning and shows a risk across the southeast. It makes sense given the forecasted movement of the same frontal system.

So, what does a 15% risk of severe weather across an area mean? It means that there is a 15% chance that a severe thunderstorm will occur within 25 miles of any point. So, at any one point, the risk is slight, but across a region that covers several states, it means someone is probably going to experience severe weather – possibly many someones.

Anyone within that highlighted area needs to be situationally aware with respect to changing weather conditions during that time period. Situational awareness means knowing where the storms are in relation to where you are. It also means thinking ahead about where you would take shelter if a severe storm, or worse – a tornado – hits your location.

Think ahead because in the middle of a crisis, there isn’t always time to think.

Whether we have five days of advanced notice or just 15 minutes to get to safety, being weather aware and situationally aware can make a world of difference when it comes to surviving the worst.

tornado safety

Graphic courtesy of North Carolina Emergency Management and the National Weather Service

Weather Blog

In like a snow leopard?

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The old adage about March weather is “In like a lion, out like a lamb.” Whether you use the climatological calendar on which spring begins on March 1 or the astronomical calendar on which spring begins on the equinox, March 20, it’s a month of transition. Wild swings in weather are expected in the mid-latitudes, where we live.

In central North Carolina, we are almost as likely to experience snow and ice storms through mid-March as warmth and thunderstorms. Our geographic location between the mountains and the Atlantic Ocean positions us perfectly for cold air damming events – when cold air from the north is trapped against the mountains and warm air from the ocean overruns it. Rain falling into the cold air near the surface freezes and creates icy situations.

We’re also in a good spot to experience coastal low-pressure systems running up our eastern shore and becoming nor’easters. Those tend to bring mixed precipitation events, too, if cold air is already in place or moves in quickly behind the storm.

It’s also possible in early March for the polar vortex to weaken enough to allow a blast of arctic air to shoot down this way. At this writing, it looks like that will be the case next week.

A cold front will cross the state Sunday, and the temperature will drop behind it. Any rain falling late Sunday night into early Monday morning may change over to or mix with snow. Accumulation shouldn’t be too much of a problem with milder temperatures in place this week and a rebound back into the 40s expected on Monday.

Cold air from the Arctic will pour into the eastern half of the nation behind the front and bring much cooler-than-normal temperatures to the region through most of next week. For reference, the 30-year average high temperature at RDU International Airport for today is 59 degrees. In contrast, the GFS forecast model is predicting our high temperatures will not surpass the 40s after the cold front passes on Sunday until the cold air finally retreats next Saturday.

Regular readers of this blog know that I have trust issues with forecasts that go beyond four or five days because the errors in the models compound quite a bit that far out. However, this cold snap has been pretty well forecast by some of the more trusted long-range prognosticators for the last couple of weeks. Now that the time period is getting closer, the models seem to be coming into agreement. I think this one will verify as truth.

So, this year, March will come in like a snow leopard, or an Arctic wolf. Pick your favorite cold climate predator. Only time will tell if it will go out like a lamb.

cpc map

The Climate Prediction Center’s 6-10 day temperature outlook map shows very good chances of below normal temperatures for most of the country next week.

Weather Blog

Rain, runoff, and our part in the water cycle

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As of 6:30 this morning, I’ve had more than two inches of rain over the last nine days in my CoCoRaHS gauge. My front yard has become a pond – a normal occurrence during wet periods as I’ve learned over the exceedingly rainy past year. Part of my little triangular plot of land backs up to a farm field, which sits a couple feet higher than mine. Excess water from the field creates miniature waterfalls across the property line and floods my yard. Because of a slight hill in advance of the drainage ditch in the front yard, the water has no place to go. So, it sits. Sometimes for days. I joke with my friends that I’m going to teach my black cat to snorkel out there.

rain report

The author’s rain gauge report for the Community Collaborative Rain, Hail & Snow Network (CoCoRaHS) showing her daily rain totals for the last 9 days.

When I watch the little rivers of runoff coming down from the field, I wonder what nutrients or pollutants are coming with it. To be sure, there must at least be fertilizer and possibly pesticides. In a way I’m glad the water stops there and doesn’t run down the ditch and into the closest stream which flows into the closest river, which isn’t far from my house. My front yard is serving as a filter. Sure, it’s a mucky mess to look at after days of rain, but it’s actually serving a higher purpose.

Rain is typically clean when it falls.

We poetically say it washes away the dirt, pollen, and grime of the world, and it does. What most people rarely consider, though, is to where it washes the dirt, pollen, grime and pollutants.

We learned in elementary school that part of the water cycle includes the rainwater draining into streams which run into rivers which lead to the oceans. In a perfect world, by the time the rainwater reaches the ocean, it should be clean again. Unfortunately, our world is rarely perfect.

From cigarette butts discarded from a car window to drink containers dropped by a carefree child, trash ends up on the ground. In urban areas, when the rain comes, the refuse is carried to storm drains. From the storm drains, it makes its way into streams – possibly even streams nobody remembers exist – and from the streams into the rivers, and so on.

Rocks, soil, and plants along the water’s route help to filter out small pollutants including fertilizer and pesticides caught in the runoff. Some of the larger trash may end up on the shoreline. Still, plenty continues to float downstream.

Beyond aesthetics, one huge reason to not litter – and even to pick up litter that isn’t yours – is to protect our water.

It’s too easy to wave off someone else’s trash as disgusting without doing anything about it. After all, it’s not ours. Why should we clean up after someone else? I agree that we shouldn’t have to. Unfortunately, that’s not how the world works. Pollution happens, and we can’t just ignore it because we didn’t have a hand in causing it.

So, what can we do?

On my property, I pick up the trash people lazily throw out of their car windows. (Who said living in the country guaranteed a clean environment?) When I visit the beach, I take two plastic bags on my morning walks: one for special seashells and one for trash. Sadly, the seashell bag usually ends up full of trash, too. It’s not my trash and it’s not my beach, but it is my planet. I take ownership.

As we head toward spring, local community volunteer and government organizations will start posting stream clean-up dates. If you want to make a difference in just a few hours, pick a date (or multiple dates) and join the effort. It’s easy. I’ve done it. You meet new people and get some exercise in the process of helping to divert garbage from our water supply.

You could even take it a step further and form a group to adopt a stream within the city of Raleigh. If you’re not in the Raleigh area, check with your local government. It may have a similar program. The state of North Carolina also has a program called NC Stream Watch. Its website explains ways to get involved including trash pickup, water source tracking, and submitting photos of the waterway.

Grab some friends or make new ones, set a good example for the children in your life, and get involved.

It’s your world. Take ownership!

Weather Blog

Confidence levels in forecasting

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This weekend’s weather will be unsettled – meaning we’re in an active pattern that will bring clouds, showers and swings in temperature. That much I’m sure of. Sunday’s forecast carries a little less certainty, though, which is why I have low confidence in the forecast.

I’ve written before about what the word “confidence” means when it comes to forecasting, but the idea is worth revisiting since we have such a great example this weekend.

When the computer models meteorologists use to forecast the weather are in total agreement, it’s easy to have high confidence in a forecast. Generally, that scenario happens in a quiet, relatively simple weather pattern. The more complicated the pattern and the more dynamic the atmosphere, the less the models tend to agree, especially when looking more than 48 to 72 hours out.

Sometimes, the difference between the models is only in how high or low the temperature will go. Other times, it’s how much or little precipitation will fall. One model may call for sunny skies and the other shows 90% cloud coverage most of the day. When these differences occur, the forecaster has some decisions to make. Which model seems to be the most believable based on how it has handled recent similar situations? Which one seems to be seeing everything that is currently happening at the moment the forecaster is viewing them?

A skilled, experienced forecaster has a better chance of getting the forecast right in these situations because experience is often the key differentiator. For example, someone who has lived in the Triangle area for a long time will be more likely to spot the kind of forecast-busting, cold air damming-like situation that could happen on Sunday.

As of this writing on Wednesday morning, the Global Forecasting System (GFS) model is showing a cold, cloudy, rainy Sunday, at least through the afternoon. With light breezes from the east and overcast skies, showers are possible. The high temperature may not even make it to the low 40s by afternoon. It’s also showing that the temperature may jump quickly from around 40 degrees into the lower 50s between 7:00 PM and 10:00 PM as a warm front passes and the winds turn from easterly to southerly. If that scenario plays out, our high temperature for the day will happen during the late evening hours.

On the other hand, the European model is showing slower progression of the warm front moving up from South Carolina through the day. By midnight, Wake County may still only be in the mid 40s, and the area from Fayetteville south could be in the low 50s.

The difference between these two models may not seem that great, but when forecasting a high temperature for the 24-hour period of midnight Sunday morning to midnight Monday morning, the timing of that front can make a huge difference. With the GFS solution, the high temperature for Sunday could be about 55 degrees and occur close to midnight Sunday night. With the European model’s solution, the high may only be about 46 degrees.

After so many of us experienced forecasters were burned on Tuesday with that day’s warm front stalling out in the southern part of the state, it’s hard to buy into the warmer solution. Because I know from more distant past experience that when moist wind from the east butts up against our mountains to the west, it’s hard to break down the cold air that gets trapped at the surface, I went with the cooler solution in my weekend forecast this morning.

How confident am I? If I had to give it a number on a scale of one to ten with ten being absolution sure, I’d say I’m at a six. For me, that’s low confidence. I prefer to be at an eight or higher when putting a forecast in print.

As Sunday gets closer, the models should start to agree more. This morning’s model runs were already getting closer than yesterday morning’s. It will be interesting to see how Sunday plays out. One thing I can say with certainty is that if the day turns out warmer than I predicted, that’s one forecast I don’t mind busting.

GFS map

Map credit: College of Dupage Next Generation Weather Lab. This map shows the GFS model’s temperature forecast for late Sunday night. Notice the temperature at Raleigh-Durham International Airport is expected to be 55 degrees at that time.

 

Euro map

Map credit: weather.us. This map shows the European model’s temperature forecast for midnight Sunday night. Notice the temperature range in Wake County will be in the mid to upper 40s.

Weather Blog

Winter isn’t over

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Disagreeing with a groundhog is not a popular thing to do, especially when the little rodent predicts an early spring just a few days after a brutal Arctic blast the way Punxsutawney Phil did on Saturday. However, I’ve never really been concerned about popularity, and I prefer my weather forecasts grounded in science as opposed to random rodent lore.

While you can definitely count this week’s weather as spring-like, it’s just part of the natural roller coaster ride that is central North Carolina winter. Our geographic location allows us to experience wild swings between unseasonable warmups and bitter Arctic cold, which is a blessing and a curse depending on whom you ask. Personally, I count the warmups as a blessing, but I recognize that snow lovers aren’t fans.

The temperatures will trend back toward normal this weekend with morning lows in the 30s and afternoon highs in the lower 50s. By mid-February, it looks like we could see the polar vortex weaken again and allow another Arctic air mass to head our way.

We can expect the moderate peaks and dramatic valleys so common with the roller coaster through at least early March, and that wavy nature of our winter temperatures really is normal. Anyone who has lived here for more than a few years will recall 70-plus degree days in January and February and ice storms in early March.

I’ll allow Phil fans to claim victory this week if they really feel the need because it won’t be long before Mother Nature brings them back to reality.

February 2018 temp graph

Graph credit: weather.gov. This graph shows the range of daily temperatures recorded in February 2018 at RDU International Airport. Notice the ups and downs from day to day with some afternoon highs in the 40s and others in the 70s.

Weather Blog

Lessons learned from Puerto Rico

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I’ve written before about how humans are good at adapting and figuring out ways to mitigate risk with respect to climate change and weather extremes. That theme echoed throughout my days at the National Meeting of the American Meteorological Society in Phoenix earlier this month.

While some of the talks focused just on the latest research studies of what is changing and where with respect to climate, there were many about the lessons learned so far from specific case studies and extreme storms. I attended many of those presentations.

One in particular explained how Puerto Rico is still dealing with the aftermath of Hurricane Maria. Ada Monzon is one of my new heroes. Until I attended the conference, I had never heard of this passionate and brilliant broadcast meteorologist. She lives and works in Puerto Rico, and she told us what the island has learned from Maria’s devastating landfall.

A few of her key points:

  • Nearly everyone on the island has post-traumatic stress disorder from the storm.
  • Homes and roads still need a lot of work. Many homes are not safe, especially with respect to weathering another hurricane.
  • Energy and communications have been restored, but the energy grid is still fragile and the energy infrastructure needs to be completely rethought.
  • Of the almost 3,000 deaths blamed on the storm, less than 10% were directly caused by Maria; the rest were due to the loss of electricity – especially in hospitals – and access to care.
  • Puerto Rico can’t handle another hurricane right now. Landslides and coastal erosion are still to this day ongoing problems.

Since the storm hit in 2017, Monzon has changed the way she presents the forecast during the news broadcasts because she has to be careful about the tone and terms she uses because the people respond emotionally now. So, she focuses on hope and education, and she makes sure that she gives information that is as specific and useful as possible.

Her personal goal is to teach the people of the island to be self-sufficient. Monzon talks to them about sustainability, health, and well-being. To that end, she founded a pop-up science museum that she says will soon have a permanent location. She has developed the Resilient School Program that uses STEM activities to build resilience and empower kids. She has introduced Community Emergency Response Team (CERT) training for teens, and her group has built a network of weather stations with 4K cameras.

Many of the inspired ideas Monzon has implemented are things we on the mainland could – and probably should – copy. She stated emphatically, “Kids are resilient!” and she’s right. Teach them what they need to know to help themselves, their families and their neighbors survive a natural disaster. Educate them about the basics of risk mitigation on a level they can understand, so they start thinking about it early in life. Show them technology that can aid in communication after a disaster disrupts the cell towers and landlines – short wave radio – so that if and when a disaster damages their world, they understand they are not totally helpless. That sense of empowerment brings hope, not just to them, but to their communities.

Satellite of Maria

Credit: NOAA. The GOES-16 satellite image shows Hurricane Maria as it crossed Puerto Rico and destroyed much of the island’s infrastructure, electric grid, homes, and businesses.