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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Intense Southern California Heat Wave Shatters All-Time Record Highs

The eastern two-thirds of the United States has been mired in an oppressive heat wave for the past couple of weeks, bathing much of the country in a brutal mix of hot temperatures and high humidity. However, while the east has gotten all the headlines (as usual), it's not the only heat in town. The desert southwest and southern California are in the midst of their own historic heat wave, the likes of which have never been recorded in some cities. The heat in the west has more than made up in intensity what it lacks in longevity.

Temperatures easily climbed into the 100s across much southern California and the state's Central Valley, and readings pushed 120°F in the California and Arizona deserts. Downtown Los Angeles reached 108°F on Friday. San Diego saw a high of 96°F. Yuma, Arizona, set a daily record high of 117°F. Las Vegas reached a toasty 112°F—a few degrees short of a record, sure, but still 8°F above normal.

You would expect this type of heat in the desert, but many spots in urbanized areas of California set record highs on Friday. Some of those cities saw their warmest July day on record, and some reporting stations even saw the hottest day ever recorded in decades of weather observations. At least six reporting stations in southern California on Friday broke their all-time record highs.

  • Burbank Airport, which is east of downtown Los Angeles, saw a high temperature of 114°F on Friday afternoon. This broke the all-time record high of 113°F set there in September 1971.
  • UCLA, which is in western Los Angeles, saw its all-time record high of 111°F on Friday, beating the previous record of 108°F set all the way back in September 1939.
  • Van Nuys Airport, northwest of downtown Los Angeles, measured a 117°F high on Friday. The previous all-time record high at the airport was 114°F—however, the airport's records only go back 24 years.
  • Riverside, California, reached 118°F on Friday,  tying the all-time record high first set there back in July 1925.
  • The fire station in Santa Ana, California, south of Anaheim, measured a high temperature of 114°F on Friday afternoon. This was the hottest temperature ever recorded in Santa Ana, where records go back to 1893. The previous all-time record high was 112°F set in June 1917.
  • The airport in Ramona, California, northeast of San Diego, saw an all-time record high temperature of 117°F on Friday. While impressive, records here only go back to April 1998.

The cool water of the Pacific kept communities immediately along the coast much cooler than spots just a few miles inland, but the air was considerably hotter just a few thousand feet above ground level. It was still hot at the surface despite the marine layer's powerful influence. Los Angeles International Airport only ("only") reached 92°F on Friday, but that still beat the record high of 88°F for July 6 set back in 1957.

Temperatures will climb back up into record territory for many of the same areas on Saturday. The heat will start to break on Sunday and should fall back to simply above-normal through early next week.

Why is it so blazing hot? There's a large and powerful upper-level ridge over the western half of the United States. Ridges are associated with sinking, stagnant air; we saw a great example of this last week when several derechos rode around the ridge over the Plains. There are also localized factors at play, such as downsloping winds off of higher terrain (air warms as it descends) and the classic urban heat island effect.

This type of heat is more common of early fall than the middle of summer. Our traditional idea of weather fitting neatly into three-month seasonal blocks kind of falls apart once you travel west of the continental divide. The brutal heat of summer usually plagues southern California once September rolls around, as evidenced by Burbank and UCLA's all-time record highs falling in September.

This is typically the dry season across southern California. Cities like Los Angeles historically see very little rainfall between the end of May and the end of September. Much of southern California has slipped into a moderate to severe drought over the past couple of months. These brutally warm temperatures won't help the cause. Extreme heat helps remove moisture from the ground even faster than normal, which could exacerbate dry conditions heading through the rest of the summer.

[Weather Model: Tropical Tidbits | Temperature Map: me]

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July 6, 2018

Itty Bitty Hurricane Beryl Defies the Odds, Makes Fools of Us All

Looks sometimes aren't deceiving at all. A tiny, good lookin' tropical depression far out in the Atlantic Ocean suddenly and surprisingly developed into a full-fledged hurricane that's so small you could miss it from space without knowing where to look. Hurricane Beryl unexpectedly strengthened into a category one hurricane in less than 24 hours, packing 80 MPH winds around a pinhole eye. The hurricane is about as small as one can get, barely registering larger than your average squall line.

Yesterday I wrote that this storm is "the kind of cyclone that tries to defy the odds" due to its appearance and location, but ultimately couldn't due to its weakness and the hostile environment it's approaching:

The system initially wasn't expected to develop into much of anything, but it started to look more impressive on satellite imagery during the day on Wednesday. This is the kind of cyclone that tries to defy the odds, but fortunately for storm-weary folks near the coasts, the environment is too hostile to allow this storm to buff itself up beyond what we think should be possible. Even a stronger, more solid storm would struggle against the obstacles ahead of T.D. Two.

Oops. Talk about defying the odds.

Hurricane Beryl has maximum winds of 80 MPH this morning as it scoots west toward the Lesser Antilles. The latest forecast from the National Hurricane Center shows the storm possibly reaching the islands as a hurricane before slowly weakening once it enters the Caribbean. Beryl's diminutive size will be its saving grace—even if the worst conditions affect land, it wouldn't be for more than a few hours. The greatest threat with this storm would be flooding and mudslides from heavy rain.

Hurricane Beryl's hurricane-force winds only extend 10 miles away from the center of the eye, and winds greater than 39 MPH only extend out 35 miles. My favorite size comparison for tropical cyclones (and one that always draws ire from some weather folks for its ridiculousness) is to overlay a storm's wind field over the Washington D.C. metro area to show how relatively small it is:

Beryl's hurricane-force wind field is so small that it just barely covers Washington D.C. with just enough room to fit in most of Arlington County, Virginia. The storm's field of 39+ MPH winds would be big enough to stretch from Howard County to Charles County in Maryland.

Meteorologists and weather models have a hard time forecasting the intensity of exceptionally small tropical cyclones; this storm's core isn't much bigger than a healthy supercell. Beryl is tiny, and tiny storms have a history of wildly fluctuating in intensity. On paper, at least, it seems like the storm shouldn't have achieved its current strength. But Beryl is small enough that it found itself a pocket of favorable-enough conditions and took full advantage of what it found.

The storm's structure should insulate it just enough from wind shear and dry air that it could survive into the Caribbean before starting to weaken and fall apart. However, the NHC notes in its latest forecast that predictions are more uncertain than usual because of the hurricane's tiny size. Tiny storms are fragile. Beryl brings to mind Hurricane Danny from 2015, a similarly tiny storm in roughly the same spot that reached major hurricane strength before collapsing as it approached the Lesser Antilles.

Storms like this are humbling for meteorologists and weather enthusiasts alike. I was wrong. They were wrong. We were all wrong. (Crow all around!) Nobody initially expected this storm to strengthen the way it did and they're probably lying to make themselves look good if they tell you otherwise. Predicting the weather is still an inexact science and there's a lot for even the experts to learn about how and why tropical cyclones suddenly intensify, especially itty bitty ones like Beryl.

[Satellite: NOAA | Maps: me]

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July 5, 2018

Hostile Atlantic Ocean Eagerly Waiting to Tear New Tropical Depression to Shreds

Newly-minted Tropical Depression Two is a visually impressive but ultimately doomed cyclone that's far out in the Atlantic Ocean between the Lesser Antilles and Africa. The system in any other year would become a serious concern for interests near the coast, but in this year, this hostile year for the Atlantic Ocean and us all, the storm will last about one-third of a Scaramucci, meeting its untimely fate this Sunday in a swift and meteorologically gruesome fashion.

The National Hurricane Center's first forecast discussion for T.D. Two reads more like the eulogy at a living funeral rather than a dire prediction of tropical woes. The environment is not suitable for significant development. The cyclone may grow strong enough to achieve the name Tropical Storm Beryl before dissipating this weekend at the hands of cooler-than-normal waters, dry air, and strong winds.

The system initially wasn't expected to develop into much of anything, but it started to look more impressive on satellite imagery during the day on Wednesday. This is the kind of cyclone that tries to defy the odds, but fortunately for storm-weary folks near the coasts, the environment is too hostile to allow this storm to buff itself up beyond what we think should be possible. Even a stronger, more solid storm would struggle against the obstacles ahead of T.D. Two.

A quick look at this morning's visible satellite image across the Atlantic shows a small, classic-looking storm that looks like it could have been the nucleus to something more ominous had it formed in a better environment. All that beige fuzz ahead of the storm over the Caribbean is Saharan dust that blew off of Africa ahead of the tropical wave that would become T.D. Two. Dusty desert air is not conducive to a juicy tropical cyclone.

Adding insult to injury is strong wind shear over the eastern Caribbean that will shred the storm to pieces in a hurry. Strong upper-level winds disrupt the updrafts in thunderstorms that try to form and displaces existing thunderstorm activity far away from the center of the cyclone. Both of these work together to kill storms fast. It's something special to watch the thunderstorms in a tropical cyclone floof away (technical term) so fast in dry air and strong wind shear that all that's left is a naked low-level swirl confusedly spinning itself to oblivion.

The remnants of T.D. Two/Beryl will continue into the Antilles through early next week and bring some heavy rain to the area. Aside from a slight chance that a disturbance near Bermuda could briefly develop over the next day or so before also meeting a swift end, the Atlantic will return to its quiet state soon enough.

Related: Here's a Hype-Free Rundown to Help You Keep Track of Storms This Hurricane Season

[Map: Dennis Mersereau | Satellite: NOAA | Model: Tropical Tidbits]

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