August 15, 2018

Another Weak Storm Forms in Oceanic Boondocks As Peak of Hurricane Season Nears

Subtropical Storm Ernesto formed in the northern Atlantic Ocean on Wednesday, posing a threat to nothing but some fish and ships. The cyclone may strengthen a tiny bit over the next day or two as it accelerates northeast toward a less favorable environment. The Atlantic hurricane season has been rather anemic this year, puffing out storms that look more like Ernesto than anything more serious. (Not that there's anything wrong with that.) But don't let the quietness fool you—we're on the doorstep of peak season, and history says there's a good chance we'll see a decent storm or two in the next few weeks.

The National Hurricane Center says that Subtropical Storm Ernesto has 40 MPH winds as it lingers many hundreds of miles from anyone who cares. The system is...sufficiently spinny?...on satellite imagery. It's hard to find anything complimentary to say about a sad storm like this. One interesting sight is that you can actually see smoke from the California wildfires wrapping into the storm from the north. (Yes, really.) The storm will continue in the general direction of the Ireland and the United Kingdom as it degenerates and merges into a frontal system this weekend.

Ernesto is a subtropical storm. The difference between subtropical and tropical is an academic exercise that does more to confuse people than serve a practical purpose. A tropical cyclone is a low-pressure system that has a tightly-packed core of thunderstorms around its center of circulation. A tropical cyclone has warm air through the entire storm—top to bottom, side to side—and the storm gathers its energy through the thunderstorms at the core of the storm.

A subtropical cyclone, on the other hand, is one that features characteristics of both a tropical cyclone and an extratropical cyclone, or the typical low-pressure system you'd see over land. A subtropical cyclone isn't uniformly warm throughout the entire storm. A subtropical cyclone's thunderstorms and winds can be far removed from the center of circulation. A subtropical cyclone usually gathers some of its energy from upper-level winds rather than through thunderstorm activity.

Subtropical cyclones are kind of tropical, and their impacts are similar enough to tropical systems that the NHC gives them the same treatment.

So far this year, four out of the five storms we've seen in the Atlantic Ocean were subtropical at one point during their life cycles. It's a testament to the unfavorable conditions that have dominated the ocean basin for the past couple of months.

The end of May saw Alberto make landfall in Florida as a subtropical storm. The unlikely life of Hurricane Beryl swiftly ended as it approached the Lesser Antilles, only to redevelop as a subtropical storm almost a week later. And Debby formed in roughly the same spot as today's Ernesto, starting life as a subtropical storm before transitioning into a fully-tropical storm with 50 MPH winds.

We'll have to keep a very close eye on the tropics over the next month. While unfavorable conditions for tropical development—high wind shear, dry air, Saharan dust—will continue for the foreseeable future, we're in prime season for tropical waves coming off of Africa's west coast to develop into something more. The NHC's evening forecast on Wednesday called for a small window of opportunity for a bulky tropical wave moving toward the Lesser Antilles to develop a bit before wind shear gets a hold of it.

The most dangerous threat we face in a quiet hurricane season is complacency. There are plenty of examples of slow years pumping out a major storm. The slow 1997 hurricane season produced Hurricane Danny, a destructive storm on the Gulf Coast that caused nine-figure damages and dropped more than three feet of rain on Dauphin Island, Alabama. The posterchild for "don't let a quiet season fool you" is Hurricane Andrew, forming in the middle of August during the otherwise-quiet 1992 hurricane season.

[Satellite Image: RAMMB/CIRA]

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August 10, 2018

Here Are the Best Ways You Can Get Emergency Weather Alerts

I think I've written the phrase "keep an eye out for warnings" in every post I've ever written about thunderstorms. Urging folks to listen up for weather alerts is a mainstay of daily weather forecasts. Most bad storms are warned in advance, but judging by the amount of people who say "we had no warning!" after a major disaster, it makes you wonder just how many people are listening for warnings at all.

I have so many weather alerts coming at me during severe weather that the apartment sounds like WUPHF from The Office when there's a severe thunderstorm nearby. I've long been open about the recent reemergence of storm anxiety. There were a couple of times in college I came close to finding myself in a dangerous spot because I didn't hear a severe thunderstorm or tornado warning. One of my roommates chose not to wake me up for a tornado warning one morning even as the sirens blared outside—the tornado touched down not far from campus.

It would be pretty embarrassing if I were to die in a tornado or earn myself a new head shape thanks to a hailstone. Could you imagine the fun the tabloid websites would have with that one? Storm Clown Torn Down By Cloudy Beatdown. Well, regardless of the reasoning, I try my best to stay ahead of any storms that come my way, and that's something we should all strive to do.

Meteorologists and reporters always tell you to listen for warnings, but what's the best place to look to make sure you hear every warning every time? Here's how I get my warnings.

NOAA Weather Radio

Source: Amazon

I have a NOAA weather radio. These devices are like smoke detectors for the weather. The radios themselves are a bit outdated compared to the technology we have today, but they're a fantastic backup device when dangerous weather is on its way.

Each county/parish in the United States has a unique six-digit identifier (called a SAME code) that you can program into your weather radio. If you tune to the right frequency for your area, the radio will listen for that county's code to come across in a watch or warning and it'll sound a loud siren and turn on the audio feed when it hears that code in the broadcast. You know that annoying screeching sound in the Emergency Alert System? That's actually a coded message similar to dial-up, and it's that tone the radio listens for and uses to sound an alert.

A basic SAME-enabled weather radio costs somewhere around $30 depending on where you look. More advanced radios—ones that allow you to program which alerts you want to hear and which you'd rather ignore—are a little more expensive, but worth it if you want to tune out some alerts that don't apply to you.

The Weather Channel's Bot on Facebook Messenger

One of the most surprising tools I've found useful during severe weather is The Weather Channel's bot on Facebook Messenger.


Facebook Messenger allows companies to set up bots to communicate with you through automated messages. You can use Messenger to do things like order food, discover music through Spotify, receive breaking news alerts from NBC News, and get weather forecasts and severe weather alerts from The Weather Channel.

The Weather Channel's severe weather alerts are usually the very first notification I get when a watch or warning is issued for my town. These alerts actually come through to me on Facebook Messenger a second or two before my weather radio goes off.

The only downfall to these alerts is that they don't follow you around when you're out and about. You only receive alerts for the location you program into the app. Much like weather radios, this Messenger bot is a great tool if you're at home or the office, but it's not the ideal source for warnings when you're out traveling.

Wireless Emergency Alert System

The Wireless Emergency Alert System is a default feature on all modern smartphones sold in the United States. The system sends out emergency alerts to users based on their location. This is a great improvement over the county-based method in that only people in a tornado warning will receive a tornado warning. This cuts down on the Crying Wolf effect and ensures the folks who are in harm's way know that they need to take the alert seriously.

The only problem with wireless emergency alerts is that people tend to deactivate the feature after one or two annoying disruptions. The main purpose of the system, as with on television and radio, is to allow the President of the United States to quickly communicate with the public in case of a national emergency. The most common use, though, is for severe weather. These alerts are typically sent out for tornado warnings and flash flood warnings, but they can be used for hurricane warnings in coastal areas and even dust storm warnings in desert regions.

It's a really good idea to look in your phone's settings and make sure these alerts are activated. They may be annoying, but the NWS has found at least one case where these alerts were directly responsible for saved lives.


There are more weather apps available on Android and iOS than anyone could possibly cover in one blurb. Heck, I've written enough words about the trustworthiness of apps to fill a book. Most reputable weather apps give you timely severe weather alerts based on your location. If you're going to rely on an app for a potentially life-saving warning, I'd rely on one of the big ones—someone like The Weather Channel, Wunderground, AccuWeather, or WeatherBug.

I try to shy away from apps when I'm under the threat for severe weather. My apps sometimes tell me when there's an alert and sometimes they don't. I have The Weather Channel and Wunderground apps on my phone and they both stopped giving me alerts months ago. I don't know if an update tripped a setting or what.

Situations like that are why I like redundancy. I like it when my phone and radio and TV all go off at the same time because I know I'm covered when it suddenly sounds like I won a few bucks on a dorky slot machine.

Code Red Alerts

A growing trend among towns and counties in the United States is to allow residents to sign up for "Code Red" alerts. These services allow localities to push out emergency alerts to people ahead of events like dangerous weather, police activity, boil water advisories, and road closures.

My town in North Carolina, along with many other communities around the country, subscribe to Code Red alerts from OnSolve. Through this program, I receive a text message, email, and phone call when there's an emergency in my area. The lead time is comparable to NOAA Weather Radio. I've only ever had a one-minute delay at most.

Check your city or county's website to see if your local government is signed up for the program.

Television and Radio

When all else fails, it never hurts to flip on the TV or listen to an AM/FM radio. Emergency alerts are broadcast within a few minutes of the issuance of a severe weather alert. Television alerts are usually more useful than ones broadcast over AM/FM radio since they're more targeted to your county. Emergency alerts on the radio have to cover the station's entire listening area.

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August 6, 2018

Major Hurricane Hector Will Likely Pass South of Hawaii This Week

Hurricane Hector is a powerful category four storm with sustained winds of 140 MPH as it entered the central Pacific basin on Sunday night. The hurricane will likely remain south of Hawaii as it makes its closest approach this weekend, but a small northward change in its track could bring dangerous conditions close to the islands.

Hector is downright impressive on satellite imagery today. Its appearance reflects its strength. The storm has a solid eye, thick core, and good outflow. It's unsettling to see a storm this strong in any ocean basin let alone moving in the general direction of heavily-populated islands.

The hurricane will make its closest approach to the Hawaiian Islands between Tuesday night and Wednesday night. Most strong storms in the past that have moved through Hurricane Hector's current location stayed south of the islands and it looks as though this one will do the same. Assuming Hector stays south as forecast, the greatest threat to the islands will be rough surf and rip currents.

The hurricane's track depends on the strength of a ridge of high pressure to the north of the Hawaiian Islands. The outer edge of a high acts like a guardrail for hurricanes, steering them along the outer periphery of the ridge. A stronger ridge will steer Hurricane Hector farther south of Hawaii, while a weaker ridge will allow the storm to track farther north and closer to the 50th state. If the ridge turns out to be weaker than forecast and Hector jogs north, dangerous conditions can't be ruled out on the Big Island on Wednesday.

The Central Pacific Hurricane Center—the NHC's counterpart in Honolulu—expects that the hurricane is at or very near the strongest it'll get this week. Dry air from the north is starting to wrap around the hurricane and will soon start chipping away at its organization, forcing the storm to slowly weaken as it makes its closest approach to Hawaii.

The close approach of a hurricane is the last thing Hawaii needs at the moment. The May 3 eruption of Kilauea on the southeast coast of the Big Island destroyed entire neighborhoods and the lava flow is still going three months later. A large wildfire also broke out on the island of Oahu this weekend, consuming at least 5,000 acres of land and several homes.

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August 1, 2018

Damaging Winds and Isolated Tornadoes Possible on the East Coast on Wednesday

A threat for severe weather will accompany thunderstorms that pop up east of the Appalachians this afternoon. The Storm Prediction Center has issued a slight risk for severe weather—a 2 on a scale from 1 to 5—due to the threat for damaging winds and an isolated risk for tornadoes and large hail. The threat shouldn't be widespread, but any storm that develops could get strong in a hurry.

The eastern United States is deep in a gross weather pattern that just doesn't want to go away. A strong Bermuda High over the western Atlantic is funneling rich tropical moisture as far north as the Canadian Maritimes. This is why the East Coast has been so unusually muggy and wet for the past couple of weeks.

Source: Tropical Tidbits
A sharp trough stretching from the Great Lakes to the Gulf Coast on Wednesday will force thunderstorms to develop along and east of the Appalachian Mountains once daytime heating sufficiently destabilizes the atmosphere. There's enough wind shear in the atmosphere that conditions are favorable for storms to organize into squall lines—where damaging winds would be the greatest threat—or even isolated supercells, where large hail and tornadoes could occur.

It's not hard for thunderstorms in the middle of the summer to produce damaging wind gusts, especially in the southeastern United States where storms have ample moisture to work with. The severe weather threat today is exactly where you'd expect to see severe thunderstorms at the beginning of August.

Not only is there a risk for severe weather, but we can't discount the threat for flash flooding where storms develop. Flash flood watches are in effect from the Alabama coast all the way up to northeastern Pennsylvania. This region has seen a lot of rain recently. Parts of Pennsylvania and Maryland saw more than a foot of rain last week. The combination of soggy ground and the potential for torrential rain in any storms that form will heighten the risk for flash flooding through the end of the week.

It's a good idea to check your smartphone to make sure that emergency alerts are activated. People like to shut those off after one too many AMBER Alerts or flash flood warnings, but it's really helpful when you're out and about and a tornado warning is issued for your location.

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July 30, 2018

Oh, For Crying Out Loud, Please Not This Gross Weather Pattern Again

Please no. Please, have mercy. This has been such a gross summer. Please, give us a break. I beg of you. I can't take it anymore. [clears throat] Sorry about that. I'm so tired of the nasty weather pattern that's plagued the eastern United States over the past couple of weeks that I've reached the bargaining stage of the grief process.

As you could have guessed, the weather over the East Coast this coming week will closely resemble the intensely muggy, torrentially rainy, and persistently stormy pattern we've seen on and off for the past three weeks. This week will feature a strong Bermuda High over the western Atlantic Ocean and a stubborn trough running up against it from the west.

Just about everyone from the Gulf to New England will deal with the fallout from this atmospheric tug-of-war between the ridge to the east and the trough to the west. The southerly winds flowing between the ridge/trough combo will open up a conveyor belt of tropical moisture across the East Coast, bringing deep tropical moisture over the region.

The GFS model's precipitable water forecast on the afternoon of July 31, 2018. | Source: Tropical Tidbits

Precipitable water measures the amount of moisture in the atmosphere, effectively telling us how deep of a reservoir of moisture thunderstorms will have to tap into as they rain themselves out. The greater the precipitable water, the greater than moisture thunderstorms have to work with, and the heavier the rain can be. The Sunday evening run of the GFS (American) weather model shows precipitable water values over the southeast and Mid-Atlantic hovering at or above 2.00", which is very high outside of the tropics.

Accordingly, any showers and thunderstorms that develop will have a rich supply of moisture feeding their heavy rains. The Weather Prediction Center expects a widespread shot at two or more inches of rain over the next seven days from the Gulf Coast through Pennsylvania, with the greatest totals expected along and to the east of the Appalachians in the southeast. It's not out of the question for some areas to see much higher rainfall totals if they get caught under training thunderstorms.
Source: NWS

The region certainly doesn't need it. Recent rains have brought extensive flooding to the Mid-Atlantic and brought many of us out of a growing rainfall deficit. More than a foot of rain fell across communities from eastern Maryland through east-central Pennsylvania, leading to widespread flooding. It won't take much more heavy rain to cause more flooding concerns over areas that have already seen plenty of heavy rain in recent days.

[This post was updated at noon on Monday to include the latest WPC rainfall forecast.]

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July 26, 2018

Why Are Summertime Thunderstorms So Intense?

We've all experienced one of those afternoon thunderstorms that was surprisingly strong. Summertime thunderstorms in the eastern United States can get rough in a hurry. It's not hard for a storm to produce strong winds or a few inches of rain in one sitting. These storms are usually right on the line between strong and severe—sometimes not enough to trigger a warning, and rarely enough to warrant a watch. While summertime thunderstorms usually aren't as strong as the worst outbreaks spring can throw at us, even a run-of-the-mill storm in July can be a force to reckon with.

Pop-Up Storms

Source: NWS Jetstream
Not all thunderstorms are alike. Different types of thunderstorms form in different environments. A supercell, a storm driven by a rotating updraft, forms in an atmosphere high in instability and wind shear. The rotating updraft in a supercell makes it strong and resilient, allowing it to survive for hours and possibly produce very large hail, strong tornadoes, and intense winds.

The vast majority of thunderstorms we see around the world are single-cell thunderstorms, or thunderstorms that develop individually and survive for about half an hour before dissipating. Single-cell thunderstorms are also known as pop-up, popcorn, garden-variety, or airmass thunderstorms, depending on who you talk to. The common diagram of thunderstorm development we learned in elementary school—a single updraft growing into a tall, mature cloud, raining out, and dissipating—depicts single-cell activity.

It's these single-cell storms that pose so much of a hazard during the summer months. Most of them are innocuous and just a headache at their worst, but some can grow severe in a hurry, producing damaging winds, flash flooding, and occasionally some hail.

50% Chance of Rain

You don't want to hear a forecast say "I don't know," but when it comes to forecasting afternoon thunderstorms in the middle of the summer, sometimes we really just don't know. Painful as it is, waiting to see where the day's first thunderstorms will develop usually boils down to watching satellite and radar for signs of development.

It's easy to see where they'll pop up at the coast because of the sea breeze. Looking on the ridges and eastern side of the Appalachians is a safe bet for initial storm development in the Mid-Atlantic and parts of the southeast. Everywhere else, though, it's a matter of small-scale features that trigger storm development.

It's still a hit-or-miss ordeal once the storms pop up. Outflow boundaries, the leading edge of rain-cooled air that descends from a thunderstorm, usually determine where the next thunderstorms pop up. A single storm could lead to just one more storm or could be the catalyst for a dozen more. It's all a matter of the environment at the moment.

The gist of it is: don't be too hard on your favorite meteorologist when she or he forecasts a 50% chance of thunderstorms in the middle of July. We can tell a lot about the weather in advance, but there are some things that are still wait and see.


Summertime thunderstorms can take you by surprise, but they sure can have a hard time sneaking up on you. The lightning in warm-season storms can be prolific. The most intense storm complexes can produce thousands of lightning strikes an hour. Lightning is more vivid during the summer because thunderstorms have more moisture to work with, increasing the chance of frequent lightning strikes.

The dramatic reduction in lightning deaths in the United States over the past couple of decades is one of the greatest weather success stories of the modern era. We used to average several hundred lightning fatalities every year back in the 1950s. The average number of lightning deaths now is just a few dozen a year. The reduction is due to better detection, warnings, education, and the simple fact that we're spending more time indoors now than ever before.

Heavy Rain 

The second hallmark of a pop-up thunderstorm in the summer is the heavy rain. Gully-washing, toad-strangling, cats-and-dogs kind of rain. We're dealing with this right now in parts of the east where persistent thunderstorms have dropped up to half a foot of rain parts of Virginia and Pennsylvania over the past couple of days.

A great way to measure the amount of moisture in the atmosphere is precipitable water (PWAT). Precipitable water tells you how much rain would fall if you condensed all the moisture out of a column of the atmosphere. If the PWAT over your house is 1.75", it means that you'd have 1.75" in your gauge if all the moisture above your house fell as rain.

Source: Tropical Tidbits

Higher PWAT values indicate a better chance that thunderstorms can tap into a deep reservoir of tropical moisture and produce copious amounts of rain. That's why the recent storms in the southeast and Mid-Atlantic have all been deluges. The PWAT value near Washington, D.C., at 8:00 PM on July 24, 2018, was 2.19", higher than the 2.09" measured in Miami, Florida, at the same time. That's a deep reservoir of tropical moisture over the Mid-Atlantic, and it's that conveyor belt from the south that's responsible for the intense rain we've seen from thunderstorms lately.


Source: NWS
Most storms are just a nuisance, but some can grow severe. Aside from flooding from heavy rain, the most common severe weather threat we see from summertime thunderstorms is damaging wind gusts. due to microbursts. We usually see microbursts in the southern and eastern United States where there's deep, tropical moisture available to any storm that forms.

A microburst is a small, focused burst of winds that quite literally drops out of the bottom of a thunderstorm. A distant view of a microburst falling out of a thunderstorm looks like a dark water balloon that speeds toward the ground and "bursts" upon impact, spreading out in all directions as severe winds.

These downward bursts of wind can be as small as a neighborhood or they could affect an entire town. Microbursts, in addition to being lethal for approaching and departing aircraft, are usually responsible for those thunderstorms where the wind cranks up from docile to raging in a matter of seconds.

Microbursts can form as a result of water loading and dry air entrainment. Water loading is a process that works just about how it sounds. Updrafts hold a massive amount of water aloft in a thunderstorm, especially in juicy storms like we see in the middle of the summer. If the updraft suddenly weakens, or the weight of the water is too much for the updraft to hold, all of that water can fall at once. The column of water and descending air speeds up at it approaches the ground, hitting the surface as a dramatic burst of severe winds.

Dry air entrainment occurs when dry air intrudes into the mid-levels of a thunderstorm. The dry air causes the raindrops to evaporate; since evaporation is a cooling process, this leads to cool air developing in the middle of a thunderstorm. This newly-cooled air will start to sink as it's less dense than the air around it. As the dry, cool air descends, it causes more rain to evaporate, leading to more cooling, which leads to the air descending even faster. The descending air eventually breaks through the base of the storm and hits the ground.

You can see the dramatic effect of a microburst in this fantastic video taken in North Carolina a couple of years ago:

The wind really can crank up that fast. Microbursts are just as dangerous as they are frightening.


Hail isn't a big threat in daily thunderstorms during the summer. It usually takes a severe weather setup in order for thunderstorms to produce hail in the summer. An extreme recent example of this was an unusual severe weather outbreak that brought near baseball-size hail to central Georgia and produced large hail as far south as southern Alabama.

Most of the hail you'll see in the middle of summer is on the smaller side. Sometimes it grows big enough to leave dents and break a few windows, but it's (usually) not like the honkin' hail you would see in April that leaves craters in your front lawn.

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July 20, 2018

Photogenic Iowa Tornadoes Get More Coverage Than Storm That Kills 17 in Missouri

Severe thunderstorms killed 17 people in Missouri and produced multiple damaging tornadoes in Iowa on Thursday. The destructive but non-fatal tornadoes in Iowa got more coverage than the deadly thunderstorm in Missouri in large part because the tornadoes were well-documented in excruciating and dramatic detail. More severe weather is possible during the day on Friday across the Ohio Valley.

Thursday was a bad day for severe weather in the United States. Multiple tornadoes touched down across central Iowa on Thursday afternoon. At least two of the tornadoes were particularly destructive, destroying buildings and tossing parked cars several hundred feet. All of the damaging tornadoes were caught on video in vivid detail. The tornadoes were strong, but the frenetic reaction on social media and from some news outlets in the hours after the storms was a bit much relative to what happened.

The Associated Press' story on the tornadoes repeatedly calls the tornadoes "unexpected." The forecast called for a low chance of tornadoes on Thursday—the risk for hail was supposed to be higher—but meteorologists issued a tornado watch ahead of the storms and each tornado was warned well in advance. The number and intensity of tornadoes was unexpected, but the tornadoes absolutely didn't come without warning.

The tornadoes in Iowa on Thursday struck a nerve on social media for a few reasons. The weather has been boring lately. I wrote a post about the "summer doldrums" the other day, the period in July when the weather is active but usually boring and repetitive. There also haven't been that many tornadoes this year. We've only seen 55-60% of our normal number of tornadoes so far in 2018. The lack of exciting weather and relative lack of tornadoes amplifies an event like we saw yesterday.

There were also multiple HD videos shot from pretty much the outer circulation of the tornadoes. The people who took the videos likely would have been injured had the tornadoes shifted a few dozen yards closer to them. We watched in striking detail as homes violently shredded apart and dazed survivors surveyed parking lots full of overturned cars that had come to a rest just seconds earlier.

We've always had dramatic videos of violent weather from up close. But even this far into the smartphone era we're still getting used to being inundated with views from every angle of a natural disaster. The raw, realtime quality of the videos we saw yesterday—watching the storms march into towns on radar and then watching videos of the destruction a few minutes later—seems to have resonated quite a bit with a lot of folks, especially those in online media.

The Iowa tornadoes wouldn't have gotten half the attention they received if it weren't for the captivating videos. I can say that with confidence because, while nobody died in the storms in Iowa, storms at the same time in Branson, Missouri, killed 17 people and that tragedy didn't get a fraction of the attention until today.

Divers are still searching Table Rock Lake near Branson, Missouri, after a tourist boat capsized in high winds during a severe thunderstorm on Thursday evening. Out of 31 people on the boat, 14 survived, 13 bodies were recovered, and crews are still searching for four who are missing and presumed dead. This was one of the deadliest severe thunderstorm-related incidents in the past several years. To put this storm in perspective, no single tornado has killed as many people as that one severe thunderstorm since 24 died in the EF-5 that hit Moore, Oklahoma, on May 20, 2013.

Despite the boat company's statement that the storm came on suddenly, a severe thunderstorm warning was issued for the area at least half an hour before the onset of high winds.

Friday Storm Threat

The threat for severe weather isn't over yet. A moderate risk for severe weather is in place across the Ohio Valley on Friday as severe thunderstorms develop through the afternoon hours. Some of the storms will be supercells capable of producing very large hail, tornadoes, and damaging winds. The moderate risk was issued due to the potential for hail the size of golf balls or larger. The greatest risk for tornadoes exists in the moderate risk zone along and near the Ohio River.

A risk for all modes of severe weather exists far outside of that bullseye over the river, stretching as far south as Montgomery, Alabama, and as far north as central Michigan.

There's No Excuse For "We Had No Warning"

We are saturated with weather information these days. There's no excuse for anyone to be caught off-guard by severe weather anymore. Most dangerous storms are warned in advance. When people say they had no warning, they really mean they didn't hear the warning.

The best way to keep up with severe weather is to check the forecast every day and keep an eye on products and forecasts issued by the Storm Prediction Center. Always make sure you have a way to receive severe weather warnings, whether you're at home, school, work, or out and about. All modern smartphones are equipped with emergency alert capability.

Keeping a weather radio capable of alert mode is a good idea for homes, businesses, and RVs. Even if you have no cell coverage and you're not paying attention to the weather, most areas receive a weather band signal and the devices can sound a loud siren when a watch or warning is issued for your county.

Very few storms truly come from nowhere. A severe weather warning is only good if we hear about it.

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July 18, 2018

U.S. Weather Hits the Summer Doldrums

It took a while, but we've finally arrived. We're in the midsummer doldrums, that long slog in July when the weather is kinda boring. There's lots of weather across the country this week, but none of it is particularly exceptional or exciting. It takes a true weather buff to find joy in a pattern like this. It's there if you look hard enough.

Quiet Atlantic

Source: WeatherBELL Models
There isn't so much as a whisper of tropical activity in the Atlantic Ocean right now. The remnants of Hurricane Beryl regenerated over the Gulf Stream this past weekend as a subtropical storm—so called because it derived some of its energy from upper-level winds instead of solely from thunderstorms around the center of circulation. Beryl's regeneration was nothing more than a novelty to gawk at from afar.

The most interesting thing coming across the Atlantic lately is Saharan dust that's lowered air quality and led to hazy skies across Texas. Each puff of dry, dusty air that crosses the Atlantic makes the environment inhospitable to tropical development. You can watch the progression of Saharan dust on weather models.

Eastern Storms

Source: Tropical Tidbits

A cold front marching toward the East Coast tonight will bring drier and slightly cooler air the the Northeast and Mid-Atlantic through Thursday. It won't be nice enough to throw the windows open (maybe up north at night), but it'll be a nice, short break from the nonsense we've been dealing with over the past couple of months.

Southerly flow on the west side of the Bermuda High—a persistent ridge of high pressure over the western Atlantic Ocean—will steadily feed warmth and mugginess into the southeast even as the cold front presses south and stalls out. The influx of tropical air will slowly push back against the front this weekend, winning out over the unseasonably dry air and helping return much of the east back to its muggy ways.

The end result is a daily chance of heavy showers and thunderstorms. They'll be your typical summertime thunderstorms—a few storms pop up, rain out, and more storms form along their outflow boundaries. It's very hard to say exactly where one storm will pop up. It's hit or miss. Some of the storms could grow strong enough that they produce damaging wind gusts or flash flooding.

The coolest thing about these storms is watching them bubble up and fizzle out on weather radar. A couple of storms in southwestern Tennessee formed in just the right spot for NWS Memphis' radar to pick up the fine details of the storms and their outflow boundaries. You can see the cool air of the outflow rippling away from the storm like waves on a pond as the thunderstorms rain themselves out. These boundaries can act like mini cold fronts, digging into unstable air and triggering new thunderstorm development.

Brutal Heat

Source: The Weather Channel
The only reprieve from the July heat in the south is sunset, and that's not even a sure bet some days. A strong ridge will keep the southern Plains particularly toasty this week. 

It's been hot and it's going to get even hotter. Dallas, Texas, is under an excessive heat watch on Thursday and Friday as highs are expected to climb above 105°F by the end of the week. The Weather Channel's forecast on Tuesday night shows a bullseye of 100-degree readings across the southern Plains during the day on Thursday and Friday. (Friday's forecast from The Weather Channel is shown above.)

The 100°F+ heat will continue through next week across Texas and Oklahoma.

It's not uncommon to reach the triple digits in this part of the country. Dallas typically records 20 triple-digit days in a year, 14 such days in Austin, 11 in Oklahoma City, and just a couple each year in Houston where it's much more humid but somewhat cooler due to the influence of the water.

Dry West

It's pretty dry out west.  Much of the West Coast and interior mountain regions have slipped into some sort of rainfall deficit over the past couple of months. The worst drought is in the southwest and southern Rockies where some areas have reached "exceptional drought," the worst category on the weekly U.S. Drought Monitor.

The good news for some of the hardest-hit areas is that the monsoon is kicking in. The monsoon is a seasonal pattern change that brings moisture and rainfall to the American southwest in July and August. This is typically the rainiest time of the year for cities like Phoenix, where they usually see a few inches of rain between the beginning of July and the end of August.

The extreme heat in Texas and Oklahoma will contribute to worsening drought conditions over the next few weeks. The most significant bouts of rain in the southern Plains this time of year comes from landfalling tropical systems; lacking those, the bulk of summer's rain comes from pop-up thunderstorms and squall lines moving in from the north.

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July 11, 2018

NOAA's Efforts to Fix Critical Weather Radar Gaps Are Slow Going

Doppler radar transformed the way we look at the weather. Tornadoes and severe thunderstorms rarely sneak up on us anymore. However, it only works when it can see the right parts of the storm. Central North Carolina has one of the worst weather radar gaps in the United States. Charlotte is the largest city in the country without adequate low-level radar coverage. There are several similar gaps across the country, but none with so many people at a disadvantage. Congress has tried multiple times over the past few years to rectify the problem. Although a renewed effort to look into gaps in radar coverage became law last year, progress is slow going.

Congress doesn't pay much attention to the weather unless there's discussion about a disaster or climate change. There are a few bills in each meeting of Congress to beef-up funding for forecasting and research, but like most proposed legislation, they never see the light of day. The Weather Research and Forecasting Innovation Act of 2017 represented the most attention Congress has paid to weather forecasting in decades. The bill, which the president signed into law in April 2017, was geared toward improving forecasts and creating better and more timely severe weather warnings.

Among other things, the lengthy piece of legislation specifically directs NOAA to conduct research into critical efforts like increasing tornado warning lead time, increase the accuracy of hurricane forecasts, and work toward better weather modelling.

The bill also directs the agency to identify gaps in the country's network of weather radars and propose a plan to fill those gaps. Lawmakers gave NOAA 180 days after the bill became law to submit to the Senate a report on gaps in radar coverage across the country and 90 days after that to formulate a plan to rectify the problems.

It's been exactly 450 days since the enactment of that legislation. The agency has not yet completed a report on radar gaps or a plan to fix them, a spokesperson for the National Weather Service told me on Tuesday.  When I asked when the agency expected to complete the report, the spokesperson added:

NOAA is working diligently to complete the study and report required. We take this requirement very seriously. Congress was made aware during the formulation of this legislation that such a study and report would take much longer than six months.

Gaps in weather radar coverage is an issue I've talked about for years. The first freelance article I ever wrote was about the radar gap in North Carolina. I've lived near Greensboro for the past eight years.  I'm intimately aware of the occasional sketchiness of radar coverage in this state. The stretch of Interstate 85 between Charlotte and Greensboro has minimal low-level radar coverage, a dangerous gamble with the number of severe storms that regularly traverse over so many people.

Why is this such an issue? It starts with the nature of weather radar and the nature of bureaucracy.

Despite Its Flaws, Radar Today Is Still Better Than Ever

Source: National Weather Service/Wikimedia

Weather radar came into operational use in the United States at the end of the 1950s. The network started with installation of the first WSR-57 radar dish at the National Hurricane Center in Miami on June 26, 1959. Dozens more would be installed over the following years, including the WSR-57 radar atop 30 Rockefeller Plaza in New York City (pictured above) that's still there to this day.

Source: NWS

Early weather radar had limited range and could only see the location and, later on, the intensity of precipitation—a far cry from today's capabilities. The above image shows the terminal that displayed radar data from a WSR-57 radar near Cincinnati, Ohio*. The hook echoes on the monitor are supercells producing destructive tornadoes during the Super Outbreak of April 3, 1974.

There were more than 130 densely-packed radar sites across the central and eastern United States before the network was modernized with the rest of the National Weather Service in the 1990s. The Next Generation Radar (NEXRAD) network was developed in the late 1980s and the National Weather Service began retiring the old radar sites and installing Doppler weather radar (WSR-88D) around the country in 1992.

Weather radar sites before modernization (pre-1989) and after modernization in the 1990s. The radar installed in western Washington in 2011 is not shown. (Source: NWS/National Academy Press | Titles added by author)

The current generation of radar uses the Doppler effect to detect the wind speed and direction within a storm, critical in the detection of storms capable of producing severe winds, hail, and tornadoes. The improved technology also gave the new radar devices a larger radius and higher resolution than the older generations, allowing the use of fewer sites that are spread across a greater distance. Recent upgrades added dual-polarization capability to the existing radar network, giving meteorologists the ability to identify rain, hail, wintry precipitation, and tornado debris.

If Only Earth Was Flat...

Source: NWS Jetstream

Doppler weather radar works by sending out strong radio waves from the radar dish at a slight angle—the standard angle for low-level coverage is 0.5°. The energy reflects off of objects in the atmosphere and the radar measures the strength of the returning beam and the time it takes to return in order to determine the location, intensity, speed, direction of movement, size, and shape of the objects in the beam's path. The radar dish then adjusts its angle upward and repeats this process for several minutes until it has a complete scan of the atmosphere.

This leads to a couple of flaws in radar technology. The first is that large objects like water towers, wind turbines, and mountains can block the beam. A temperature inversion can refract the radar beam back toward the ground and lead to false returns. Radar towers are vulnerable to lightning strikes, wind damage, and aging mechanics, which could render them inoperable at the worst possible time.

Source: NWS Jetstream

Radar is also eventually thwarted by the curvature of the Earth itself. The radar beam grows higher and higher above ground level as it gets farther away from the radar site. This limits a radar site's effectiveness beyond a certain radius when it comes to looking for tornadoes and other severe hazards.

Source: NWS
The beam curving upward with height results in gaps in radar coverage. Most of the largest gaps occur in the Rocky Mountains where the terrain simply blocks the signal from covering some communities, but some of the gaps are due to radar sites being spaced too far apart. The worst gaps east of the Rockies occur over South Dakota, Missouri, parts of the Deep South, and the worst (by number of people affected) is in central North Carolina.

Low-level radar coverage is important because that's where tornadoes form. It's crucial to see rotation within a thunderstorm as close to the ground as possible in order to detect a potential tornado and issue warnings with adequate lead time. 

Central North Carolina Got Overlooked

A radar image of the tornado near Charlotte, N.C. at 2:32 AM on March 3, 2012. The left image shows base reflectivity (precipitation) and the right image shows base velocity (wind). The radar is located to the west near Greenville, S.C.

The urgency surrounding the radar gap in North Carolina surrounds the unease of knowing what can happen without adequate radar coverage in a densely populated area. Charlotte is the largest metropolitan area between Atlanta and Washington D.C. The city and its suburbs are home to more than 2.4 million people, a population greater than that of 15 states.

There's a small Terminal Doppler Weather Radar (TDWR) site at the Charlotte Airport, part of a network of airport-based radars meant to protect arriving and departing flights from dangerous conditions. These radars are different from the WSR-88D in that they have a much shorter range and they're more susceptible to interference.

The lack of low-level coverage in central North Carolina isn't a theoretical game of what-if. An EF-2 tornado touched down a few miles northeast of Charlotte in the middle of the night on March 3, 2012. There was no tornado warning before the storm. The tornado damaged hundreds of homes and injured several people.

The tornado happened quickly and, despite its strength, the rotation was shallow. The beams from nearby Doppler radar sites were far too high to catch the rotation in the storm. The beam from the radar near Greenville, S.C., was 8,200 feet above ground level at the site of the tornado. The radar image above shows the Greenville radar at the time of the tornado. The beam there from the radar in Columbia, S.C., was 9,100 feet high. The tornado signature did show up on Charlotte's TDWR site, but it wasn't particularly strong.

This issue was known long before any new radar sites were built. Years of debate preceded the Weather Service Modernization Act of 1992, which consolidated smaller, more localized offices into the agency we know today.  A subcommittee in the U.S. House of Representatives held a hearing called "Tornado Warnings and Weather Service Modernization" on August 7, 1989, to specifically discuss the proposed closure of the Charlotte weather service office.

The modernization plan divided the Charlotte area between the consolidated NWS offices in Greenville, S.C., Columbia, S.C., and Raleigh, N.C. The new Doppler weather radars sites were co-located with those three offices, leaving Charlotte—a city whose metropolitan area has millions of people—split in thirds with radar coverage to match.

Many of the issues we're dealing with nearly 30 years later came to light in that congressional hearing. The subcommittee heard a variety of opinions on the topic. The head of citizens' emergency preparedness committee at UNC Charlotte pleaded in his testimony not to move city's radar to Columbia for fear of losing low-level radar coverage:

Jack Roper, broadcast meteorologist for WSPA in Greenville, S.C., expressed his concern about the  new radar system's spatial coverage in his part of South Carolina. He characterized the new Doppler network as something that "could be a new Edsel," a reference to Ford's aggressive marketing of a line of cars that failed to meet the ad campaign's lofty expectations and resulted in tremendous financial losses for the company.

The issues were raised again in a letter from Rep. Liz Patterson (D-S.C.) to Sen. Ernest Hollings (D-S.C.) before a June 1991 U.S. Senate hearing on NWS modernization.

Despite all of the concerns voiced in the years leading up to modernization, Charlotte still lost its weather office and its weather radar to smaller cities down the road. Problems with radar gaps were well known when the government started planning the current radar network, especially in central North Carolina, even as the agency said several years after modernization began that there was no lowering of the quality of service in the Charlotte area.

Past Attempts to Fill Radar Gaps

Several congresspeople introduced legislation to improve Doppler weather radar coverage in the years before the 2017 bill became law. The most recent legislative success that directly resulted in a new weather radar came after a push by Sen. Maria Cantwell (D-WA) to secure funding for a new radar site on the Washington coast. The new radar, which went into service in the fall of 2011, was important in monitoring Pacific storms as they approach Washington and Oregon.

Rep. Robert Pittenger (R-NC) and Sen. Richard Burr both introduced the Metropolitan Weather Hazards Protection Act of 2015 in their respective chambers. The bill directed the government to construct new Doppler weather radar sites near big cities in known radar gaps within a year and a half of the bill's passage. The, uh, creative specifications laid out in the bill—"maintain and operate at least one Doppler weather radar site within 55 miles of each city in the United States that has a population of more than 700,000 individuals"—served to limit the scope of the bill to pretty much just Charlotte, North Carolina. The bill passed the Senate by unanimous consent but died after the House took no action.

Rep. Charles Boustany (R-LA) introduced the RADAR Act in 2016, which died without any legislative action. The bill would have required both 1) the operation of at least one Doppler radar site within 55 miles of each state capital and 2) that any future radar sites would be located near at least one county with a population of 130,000+ that doesn't have adequate low-level radar coverage.

The capitals of 13 states, including Boustany's home state of Louisiana, would have been eligible for new radar sites under the proposal. While the bill would have filled in some glaring gaps in coverage, including those in central South Dakota, central Missouri, and southern Louisiana, it essentially told North Carolina that it can wait its turn until the next time around.

All of the radar-related bills introduced in Congress since Cantwell's successful push a decade ago have died in their respective chambers except for the Weather Research and Forecasting Innovation Act of 2017, the effectiveness of which is still pending.

Assuming a similar timeline to the western Washington radar earlier this decade—funding secured in 2009 and the radar made operational in 2011—we likely won't see any new radar sites until the early 2020s.

[Top Image: Pierre cb via Wikimedia Commons]

*I originally said the old WSR-57 radar image was from Wilmington, Ohio. The NWS office is in Wilmington, but the radar is in Covington, Kentucky, near Cincinnati. I've corrected my error.

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July 10, 2018

The Stalled Tropical Storm Off the East Coast Cooled the Gulf Stream Beneath It

Tropical Storm Chris is very close to hurricane strength this afternoon as it finally starts to move northeast a few hundred miles off the North Carolina coast. The storm has barely moved since it formed five days ago, caught between weather systems without any steering currents to shove it along. The storm's stalled motion has induced upwelling in the ocean beneath it, which worked in part to keep the storm from strengthening too quickly.

Chris is one of those storms that gives coastal residents some uneasy relief. The storm is pretty darn close to the United States, and it's never comforting to see a storm approaching hurricane strength right off the eastern seaboard. Chris is pinned between ridges of high pressure to its north, west, and east—the storm got trapped by the same features keeping it from hitting the United States, and there hasn't been anything to steer it away until the ridge holding it in place broke today and a trough lifts the storm out to sea.

The tropical storm sitting over roughly the same spot in the Atlantic Ocean for five days has considerably churned the seawater beneath it. This churning has allowed for upwelling, or cooler water from deep in the ocean to rise to the surface. A buoy near the storm has recorded a precipitous drop in water temperatures over the past couple of days. The buoy measured water temperatures around 82°F on Saturday, July 7, before falling as Chris grew stronger. The buoy's latest measurement recorded waters below 76°F, a six-degree drop in just a couple of days. That's even more impressive when you consider that the buoy is in the Gulf Stream.

The pool of cooler water is readily apparent in daily sea surface temperature analyses. The animation at the top of this post shows the sudden drop in sea surface temperatures beneath the tropical storm between the mornings of July 6 and July 9. Today's analysis, likely showing even cooler waters in spots, will be released tomorrow morning.

The cooler water clearly had an effect on Chris when it started to struggle a bit with its organization on Monday. The combination of dry air wrapping into the storm and cooler water beneath it served to disrupt the tropical storm's structure on Monday. The storm is much better organized today after it mixed out and walled off the dry air and it's starting to lift northeast away from the pool of cooler water it churned up. The storm's look (above) matches its strength now, with a tight core and a clearing eye.

Tropical cyclones strengthen through latent heat release. Warm water on the surface of the ocean evaporates and condenses in the storm, releasing latent heat that provides the instability necessary to sustain thunderstorms around the core of the cyclone. The warmer the water, the greater the latent heat release, and the stronger a storm can get. Cool waters inhibit this process and eventually choke off a storm by weakening the thunderstorms that surround the center of circulation.

The National Hurricane Center expects Chris to reach hurricane strength later today as it accelerates toward the northeast. While the storm will remain far offshore, dangerous rip currents and rough surf are still likely along the East Coast for the next day or two as Chris finally exits the area. The storm's peak strength won't last long—Chris will reach cooler water and less favorable conditions on Thursday, weakening the storm and forcing it to transition into an extratropical cyclone. The latest forecast shows Chris or its remnants clipping southeastern Newfoundland early Friday morning, likely bringing some heavy rain and gusty winds to the provincial capital of St. John's.

[Chart: NOAA | Maps: me | Satellite data courtesy of AllisonHouse]

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July 7, 2018

New Tropical Depression Forms Off East Coast as Tiny Hurricane Beryl Collapses

The circle of life in the Atlantic Ocean is whirring once again as Beryl winds down and Chris winds up. Beryl weakened from a hurricane to a tropical storm on Saturday morning after its surprise performance on Friday. A disturbance between Bermuda and the North Carolina coast finally developed into a tropical depression and it looks like it could make it to hurricane strength as it parallels the coast through next week.

Hurricane Chris?

An Air Force reconnaissance plane investigated Tropical Depression Three this afternoon and found it a bit disorganized as it sits a few hundred miles southeast of North Carolina's Outer Banks. The fledgling tropical depression is bigger now than Hurricane Beryl was at its strongest, truly a sad statement about the latter.

While it's unsettling to watch a storm sit and grow this close to land, the National Hurricane Center expects the cyclone to stay far enough away from the East Coast that the only problems we'll face are rip currents and rough surf. Close is close, though, and it's worth keeping an eye on it just in case things change. It's always a good idea to make sure you have emergency supplies.

Tropical Depression Three is pretty much stuck in place right now, pinned between a stalled cold front to its west and a ridge of high pressure to its east. This will allow the storm to meander for the next couple of days as it gathers strength before a trough picks the storm up and lifts it out to sea early next week.

The depression, which will gain the name Chris when it reaches tropical storm strength, will slowly gather strength thanks to the fact that it's moseying directly over the Gulf Stream. The storm should track directly over or very close to this current of warm water as it lifts off toward Newfoundland next week. Future-Chris could briefly reach hurricane strength before moving over cooler water and into a less favorable environment.

The latest forecast from the NHC shows that Chris will lose its tropical characteristics by the time it reaches Newfoundland, but it will still be a strong cyclone with gusty winds, heavy rain, and rough surf.

Beryl Collapses

Alas, poor Beryl. The loosely amalgamated clump of water vapor now known as Tropical Storm Beryl is clinging to life by a wisp of an updraft. Its low-level circulation is swirling bare, broken free of the convection that once gave it improbable life.

Beryl's triumph was its downfall. The small storm collapsed this morning just as spectacularly as it developed 36 hours ago. Beryl, much like me, fell to pieces after a minor inconvenience, in this case an intrusion of dry air and some moderate wind shear.

Nobody initially expected the itty bitty depression to strengthen into a hurricane based on its size and the hostile environment around it. Tiny hurricanes are fragile and extremely susceptible to adverse conditions. They can strengthen and weaken without much forewarning.

The 5:00 PM EDT update from the National Hurricane Center shows Beryl with maximum winds of 50 MPH in a wind field that only stretches a few dozen miles wide. A tropical storm warning is in effect for the island of Dominica as the system—or at least what's left of it—is forecast to track over the island on Sunday night. Regardless of its organization or official title, the storm or its remnants could bring heavy rain to islands susceptible to flooding and mudslides.

(I updated this post at 7:00 PM EDT with the latest information about each storm.)

[Satellite Images: NOAA | Maps: me]

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