November 15, 2018

Florida Will Participate In Autumn If It's The Last Thing The Other 47 States Do, So Help Us



Florida will soon learn that the terms of autumn are non-negotiable. The Sunshine State will participate in chilly fall mornings even if it's the last thing the other 47 contiguous states do, so help us. (Alaska can send moose if they want. Hawaii can sit this one out.)

When the state isn't exporting weird headlines or conducting horrendously-flawed elections, residents spend much of the year looking for ways to keep cool. It's no surprise that it stays toasty pretty late into the year in Florida. The state is a huge attraction during the winter months because its enduring warmth seems unshakable outside of the biggest, meanest storms that envelop the eastern half of the country.

The heat of late really has been unshakable. Not only has it been unusually warm so far this fall even by Florida standards, but the months-long extension of summer has approached record territory across the peninsular portion of the state.

The period between September 1 and November 14 saw the warmest average daily temperature ever recorded at Miami International Airport. The average of all the daily average temperatures—that is, the high and low temperature averaged together each day, and all those averages then averaged together for the entire 76-day period—came in at 81.8°F, which is the warmest recorded during climatological fall since records at the airport began in 1937.

Here's a breakdown of temperatures in Miami so far this fall:



You can see that daily highs have been above-average, but they only deviated from normal by a degree or two each day. The difference is in the lows. Most days saw a low temperature dramatically higher than what you'd expect to see for this time of the year. Except for the a couple of days at the end of October, the low temperature in Miami has remained in the mid- to upper-70s almost every day since the end of summer.

Hot and humid days fading into warm and humid nights provides residents no respite from the heat. Warming nighttime temperatures is a noticeable trend across much of the United States. The increase in the number of warm nights is one of the concerning effects of climate change.

Making matters worse is that it's a wet heat. The Iowa Environmental Mesonet shows that Miami has seen dew points of 76°F or warmer for nearly 1,700 hours so far in 2018, an excessively-muggy length of time that's second only to 2005. Dew points are generally considered to be oppressively humid once the value rises above 75°F.

I've focused on Miami in this post because it's an extreme example of summerlike heat and humidity lasting well beyond its expiration date, but it's not just Miami that's suffering. The average daily temperature since September 1 is also sitting in record territory up at the major airports in Orlando and Tampa. It remains to be seen how much averages for the entire fall will moderate back toward normal with the upcoming cooldown.

Thankfully, things are going to change soon, even if it's only by a little bit. Look at this GFS model animation of dew points over the next couple of days:

Source: Tropical Tidbits



Ahhhh. That's nice. Air temperatures are likely going to remain warm for the next couple of weeks—hovering at or slightly above average most days—but the break in oppressive humidity will make it feel nicer and the relatively drier air will allow nighttime temperatures to finally fall back near normal for this time of year.

Communities near Pensacola will likely see a hard freeze on Thursday morning, and morning lows on Friday could dip into the 30s across inland areas as far south as Ocala. Low temperatures in the 40s may even reach the northern shores of Lake Okeechobee on Friday and Saturday.


You can follow me on Twitter or send me an email.

Please consider subscribing to my Patreon. Reader-funded news is more important than ever and your support helps fund engaging, hype-free weather coverage.
 

November 13, 2018

An Early-Season Winter Storm Will Bring Snow and Ice to the Midwest and Eastern States



The raw chill that's settled over the eastern half of the United States over the past couple of weeks set the stage for winter weather to follow closely behind. There's a decent chance that many areas will see their first significant snow and ice storm between Wednesday and Friday, with the heaviest snow falling in the Midwest and Northeast, while freezing rain will coat much of the Appalachian Mountains in a crust of ice.

Our storm developing tonight comes fresh on the heels of a storm that brought heavy snow to the southern Plains and heavy rain to just about everyone else east of the Mississippi River. More than half a foot of snow fell in parts of Texas and Oklahoma as the system met cold air locked firmly in place over the region. Farther to the south on the warm side of the system, persistent heavy rains and thunderstorms led to flooding and even a couple of reported tornadoes in North Carolina.

Source: Tropical Tidbits


That storm is out of here and the next one isn't far behind. An upper-level low will develop over the Mississippi River valley on Wednesday and slowly make its way east over the following two days. The system will bulk up in a hurry as it moves east, producing yet another prolonged round of heavy precipitation along its path.

Snow



Cold air on the northern side of the system will allow precipitation to fall in the form of snow, sleet, and ice. The heavy snow will start falling in and around southern Illinois on Wednesday night and Thursday morning. Some areas could see more than half a foot of snow, though widespread shovelable totals will make it difficult to get around on Thursday.

Snow will be more widespread across the Ohio Valley, Great Lakes, and Northeast on Thursday and Friday. Many areas west of I-95 are on track to see several inches of snow, with much higher totals in higher elevations and where lake effect snow enhances snowfall totals. It won't take much for the rain/snow/ice line to shift a dozen miles to the east or west, so if you live right on that line between nothing and something, it's wise to watch the forecasts and make sure you're ready with the ice scraper or snowbrush just in case.

Ice



Temperatures hovering right around freezing with above-freezing temperatures above the surface will allow for freezing rain and sleet to fall in the Appalachians and parts of the Mid-Atlantic. The most significant ice accretion will occur in the Appalachians, where one-quarter of an inch or more of ice is possible on exposed surfaces.

1/4" of ice doesn't seem like much, but that's a lot of weight on power lines and tree limbs, and it could lead to downed trees and power outages in some areas. The ice will also make travel difficult or impossible for a time on Thursday until temperatures climb back above freezing.



You can follow me on Twitter or send me an email.

Please consider subscribing to my Patreon. Reader-funded news is more important than ever and your support helps fund engaging, hype-free weather coverage.
 

November 5, 2018

Nighttime Severe Thunderstorms and Tornadoes Are Likely Tonight in the South



The Storm Prediction Center has issued a tornado watch for portions of Louisiana and Mississippi as a dangerous nocturnal severe weather outbreak gets underway. An enhanced risk for severe thunderstorms—a three out of five on the scale that measures the threat for severe weather—is in place tonight for the Mid-South. Severe weather, especially tornadoes, are extremely dangerous after dark because you can't see and many people start tuning out the weather as they head off to bed.

The situation tonight is a classic setup for severe weather in November. A developing low-pressure system over the Midwest is dragging a cold front across the southern states. In fact, you could apply just about everything I wrote about last Wednesday's risk for severe weather to today's risk, just moving all the locations a bit to the north and east. Warm, unstable air ahead of the cold front will foster the development of thunderstorms, and wind shear ahead of the storm system will allow the individual thunderstorms to turn severe.

All modes of severe weather are possible, including damaging straight-line winds, large hail, and tornadoes.



The Storm Prediction Center has issued a 10% risk for significant tornadoes across much of Mississippi and central Tennessee. The black hatching indicates the area where the environment is capable of support tornadoes that could be strong or long-lived. Tornadoes are most likely in discrete (individual) thunderstorms that pop up ahead of the main lines of thunderstorms that develop along the cold front pushing into the region.

The threat for damaging winds is greatest in the line (or lines) of storms as they organize ahead of the cold front tonight. However, tornadoes are also possible in those lines of storms. Just like we saw last week a bit farther to the southwest, we could see little kinks develop along the leading edge of the lines of thunderstorms. These rotating kinks can lead to tornadoes that develop quickly, sometimes with little or no lead time before it hits.

The storms will move from west to east through the nighttime hours, reaching the Appalachian Mountains by early Tuesday morning. The line will regenerate on the eastern side of the mountains by Tuesday afternoon, bringing the risk for severe weather to parts of the southeast and Mid-Atlantic during the day tomorrow. If you haven't voted yet, it's a good idea to vote early so the weather doesn't affect your ability to cast your ballot.

Severe weather is dangerous anytime, but storms pose a greater threat to life in the cold months and even more so again after dark. Many people want to see a tornado coming at them before they act. On top of the many, many reasons that's a bad idea, the least of which is the fact that you can't see tornadoes after dark. What's worse is that the tornadoes in a setup like this are likely to be rain-wrapped, adding an additional shroud to the tornadoes that makes it impossible to see them even when they're backlit by lightning.

Make sure the emergency weather alerts are activated on your phone. I know quite a few people who tried to disable them in the lead-up to last month's nationwide test of the Emergency Alert System. There are people alive today only because they acted when the Wireless Emergency Alerts pushed a tornado warning to their smartphones. If you don't have a smartphone or live in an area with a bad signal, keep a television or radio on when you go to sleep so you have a chance to hear warnings when they're issued. Do not rely on tornado sirens for severe weather alerts. I know your parents and grandparents swore by them, but these systems are aging, they're not designed to be heard indoors, and (ironically) they're unreliable during a storm.


You can follow me on Twitter or send me an email.

Please consider subscribing to my Patreon. Reader-funded news is more important than ever and your support helps fund engaging, hype-free weather coverage.
 

October 31, 2018

Some Strong Tornadoes Are Possible Tonight in Louisiana and Mississippi


A potent storm system moving through the southern United States today will trigger severe thunderstorms as the evening hours wear on. The environment ahead of the low-pressure system will allow some of those thunderstorms to spawn tornadoes, a few of which could be strong or long-tracked. Any threat for severe weather is a big deal at night, but especially today due to people going out for Halloween.



I wrote about the broader weather setup over at my blog on Forbes early this morning. A low-pressure system developing over the central south will trigger severe thunderstorms in the warm, unstable air over the stretch of land between central Texas and Mississippi. As we see so many times during severe weather, the threat will occur in two stages. The most dangerous storms are the discrete cells that form in the unstable airmass over eastern Texas, Louisiana, and Mississippi this evening and tonight. A line of thunderstorms will follow soon after as the cold front pushes into the region. The threat for severe weather will cease once the cold front moves through.

A tornado watch was in effect across eastern Texas and parts of Oklahoma, Arkansas, and Louisiana as of the publication of this post. Some tornadic storms are already popping up west of Houston. This activity will increase and spread east as the evening wears on.

Source: COD 


The above chart shows the crossover between winds at the 850mb level (the red barbs, around 5,000 ft) and the 500mb level (the blue barbs, around 18,000 ft). The wide angle of the crossover between lower-level and upper-level winds across eastern Texas, Louisiana, and Mississippi, is a sign that storms that form there may turn into supercells capable of producing tornadoes, damaging winds, and large hail. Damaging winds are the greatest threat from any lines of storms that develop.



This afternoon's update from the Storm Prediction Center paints parts of eastern Texas, Louisiana, and southwestern Mississippi under a 10% risk for tornadoes. The 10% risk zone includes Houston, Shreveport, Baton Rouge, and Jackson. A 10% risk doesn't seem like much, but that's pretty high all things considered. The black hatching on the map above is where forecasters believe the environment is favorable enough for some of those tornadoes to be strong and have long tracks.

Tornadoes at night are dangerous no matter what, but it's even worse when the nocturnal tornadoes occur in late October—when a lot of people don't necessarily expect tornadoes—and when people will be out trick-or-treating or attending Halloween parties. The risk for severe weather will transition shift toward the northern Gulf Coast on Thursday and move through the rest of the southeast on Friday.

Please pay close attention to weather radar and listen for watches and warnings through the evening and overnight hours. Make sure emergency weather alerts on your phone are activated in case a tornado warning is issued when you're asleep.


You can follow me on Twitter or send me an email.

Please consider subscribing to my Patreon. Reader-funded news is more important than ever and your support helps fund engaging, hype-free weather coverage.
 

October 27, 2018

Fighting Conspiracy Theories Is a Matter of National Security

I'm not shocked that the accused mail bomber, a Florida man who allegedly sent more than a dozen live explosives to prominent politicians, actors, and a news organization, shared posts about the chemtrail conspiracy theory on his social media pages. It doesn't take much for someone who believes in seemingly-silly conspiracy theories to fall for harder conspiracies that can completely warp their perception of reality. That's a dangerous prospect when the person falling down the rabbit hole may lash out based on the posts they read and videos they watch.

The chemtrail conspiracy theory insists that the trails of condensed water vapor (called "contrails") left behind by the jet exhaust of high-flying airplanes are really a mixture of dangerous chemicals intentionally sprayed into the atmosphere to control the weather or make us sick. The conspiracy theory came to prominence in the 1990s at the height of talk radio and spread like wildfire as social media came into existence. There are millions of websites, forums, YouTube videos, and pages on Twitter and Facebook that work every day to try to convince people to buy into this outlandish bastardization of physics and meteorology.

It's silly, of course. Anyone who paid attention during science lessons in elementary school—or, you know, breathed outdoors when it was cold—understands the basic concept of condensation. The hot, moist jet exhaust of high-flying aircraft can condense into a thin, wispy cirrus cloud if the atmosphere is cold and moist enough. These condensation trails can linger for hours and eventually cover the entire sky if it's cold enough and there's enough moisture at flight level, or the trails can immediately dissipate (or not form at all) if it's too dry or warm. Contrails can even form at ground level in frigid parts of the world like Siberia and Antarctica.

Conspiracy theorists would like you to believe that basic physical and meteorological principles are bunk and that the clouds are really a nefarious government plot to unleash chaos on the world. If you're uninitiated to the world of weather conspiracy theories, that's actually one of the tamer theories, coming in behind the folks who believe that antennas in Alaska and Doppler weather radar dishes can create and control destructive storms with precision that allows them to destroy entire towns and even individual homes. (If that was possible, Iraq would be tornado alley and Raytheon would own a controlling stake in The Weather Channel.)

I've written quite a bit about these theories in the past—in fact, I wrote a post much like this one back in 2014. While it's fun to make fun of the silliness of it all, I really do believe in combating nonsense with good science. My anti-conspiracy messaging was effective. For years, I was a frequent target of the ire of popular conspiracy theorists looking to hold their ground. My name showed up on lists of "disinformation government shills" or whatever term they chose to use to make me sound like I was a well-paid CIA agent for writing about things like elementary science.

Protecting the integrity of science is important; however, debunking conspiracy theories like chemtrails plays another important role. People used to ask me why I went to such lengths to debunk such a silly conspiracy theory. They usually said that my bringing attention to these theories could actually lead people to believe in them. My argument goes the other way: if we don't fight back against the nonsense, people who consume false research and start believing in little conspiracy theories like chemtrails will ultimately start down a dark path of believing in bigger and more destructive stuff.

Believing in conspiracy theories makes it harder for someone to discern objective truth in the world. One conspiracy theory often leads to another, and pretty soon that person is open to believing everything they read, no matter how detached from reality the theory is. Once someone believes that the thunderstorm currently raging over their apartment may have been created by the government—and even worse, possibly created specifically to target them—all bets are off when it comes to how they view the world. After all, if they're spraying clouds of sickness in the sky or generating a thunderstorm over someone's house, what else are they capable of? Who's pulling the strings? Who's next on the hit list?

It's tempting to tell people to just ignore the crazy ramblings of random no-names and even to brush off those with millions of followers. But online conspiracy theories don't exist in a vacuum. There are real people behind those keyboards. A real person walked into a pizza joint in Washington D.C. and opened fire because of false information he read online. Real people regularly harass the real parents of the real children who died in the real massacre at Sandy Hook Elementary School because of conspiracy theories they read on Facebook and watched on YouTube convinced them that it was all an act.

Once you're convinced that the world around you is a stage play controlled by a handful of evil people, it doesn't take much fiery rhetoric or bombastic vitriol (hello, Mr. President!) to cause someone to flip out over how scary the world is and try to do something to break the perceived cycle of control and deception. That can manifest itself in scary ways when the person trying to break the system finally snaps and decides to pick up a gun and go to a baseball field or assemble and mail a dozen live explosive devices to former presidents and cabinet members.

The world becomes vastly more dangerous as people become farther untethered from a basic plane of reality. The crazier things become, the crazier people will act. Weather exists as a way for nature to balance itself out. An enormous hurricane over the Atlantic Ocean exists to redistribute heat from the tropics to the poles. Political tension that grows without end will only serve to encourage people already on the edge to engage a severely misguided attempt to correct the world back to the balance they believe should exist—and the world they believe we live in is dramatically different from the way things really are.

When you see a conspiracy theory online—no matter how insignificant—don't let it go unchecked. A fact check may fall on closed eyes, but when we stop defending science, when we let simple facts like the size of a crowd or what someone said on tape become a subjective free-for-all that's up for debate, when we let conspiracy theories rule the internet without anything there to greet curious searchers with an alternative to the bunk they're consuming, we're waving the white flag and conceding the fight to preserve reality. This stuff is too important. The internet is a real place that's run and read by real people who can make decisions that have real-world consequences based on the things they read and see online. It's time we start acting like it.


You can follow me on Twitter or send me an email.

Please consider subscribing to my Patreon. Reader-funded news is more important than ever and your support helps fund engaging, hype-free weather coverage.
 

October 26, 2018

Can't Stand the Gloomy Weather in the Southeast? Blame Cold Air Damming.

Happy CAD season! Today is the first installment of many gray, soggy days that will cast a shroud of gloom over the southeastern United States through next spring. Cold air damming (CAD) is a frequent phenomenon east of the Appalachian Mountains during the chilly months, and it's something that—despite how common it is—you never quite get used to when you live around these parts.

Cold air damming is one of those great weather terms that doesn't leave much to the imagination. It describes exactly what's going on. The atmosphere is a fluid. Cold air is denser than warm air, so it tends to stay close to the surface. When easterly or northeasterly winds blow cool air across the Mid-Atlantic and Carolinas, the cooler air gets dammed up on the eastern side of the Appalachians because it's too dense to simply flow up and over the ridges. The cold air pools up east of the mountains and leads to chilly, dreary days like we're experiencing today.

Other parts of the country can experience cold air damming—especially in Montana along the eastern base of the Rocky Mountains—but the region between north-central Georgia and the Mid-Atlantic is where this type of weather is most common and most prominent.

Today's bout of cold air damming is about as classic as it gets. Northeasterly winds are blowing chilly air across the Piedmont as a result of high pressure near New Jersey and a developing low-pressure system entering Georgia. That area of low pressure will grow into a full-fledged nor'easter this weekend, bringing heavy rain and gusty winds to the Mid-Atlantic and Northeast. Some of the wind gusts could reach 60 MPH in coastal parts of New Jersey and New York.

The weather on cold air damming days is usually harmless—today, it's just heavy rain with temperatures in the 40s—but it can have significant impacts depending on the overall setup that led to the event. The most common feature is the unshakable gloominess that can blanket the southeast from Atlanta through the Washington D.C. area. Areas to the south could have a warm, sunny day, and even communities just on the other side of the Appalachian Mountains could see temperatures as much as 20-30°F warmer than towns stuck in the pool of cold air. Locations stuck under the wedge of cold air, however, remain chilly and socked under a thick deck of clouds—sometimes even thick fog—until the wind shifts direction and begins to scour away the cold air.

Cold air damming can have major implications on precipitation type when temperatures are hovering around the freezing mark. The wedge of cold air at the surface can lead to sleet or freezing rain when precipitation moves into the area, creating a travel nightmare in areas that aren't used to wintry precipitation or where the ice wasn't particularly well-forecast.

We probably won't have to deal with the winter weather aspect of cold air damming anytime soon. Today's weather is a dreary preview of what we can expect as we head deeper into the fall. Whenever you can't stand that winter-like gloom looming over the southeast or Mid-Atlantic, just look to the west and blame the mountains.


You can follow me on Twitter or send me an email.

Please consider subscribing to my Patreon. Reader-funded news is more important than ever and your support helps fund engaging, hype-free weather coverage.
 

Unusually Dry Pacific Northwest on Track to See Much-Needed Rainfall, But Not Enough

We don't really get the chance to talk about rain out west these days. A recurring story across much of the past...well, several years...is that the west is thirsty for any drop of water it can wring from the sky while areas east of the Rocky Mountains have more rain than they can handle. Fortunately, the Pacific Northwest is in the midst of a much-needed rainy spell, but the region is also grappling with a hefty rainfall deficit, and it'll take more than a couple of days of rain to make a dent in the region's drought.


NOAA's latest precipitation analysis really tells the tale of this year's weather patterns. The above map shows the departure from normal precipitation since January 1. The departure from normal is measured in inches. Vast swaths of land east of the Rockies have seen feet more rain than they typically see through the end of October—isolated pockets of North Carolina have seen more than 100" of rain this year—while the West Coast between northern California and Washington stands out for having fallen more than a foot below normal in rainfall so far this year.

Thursday's update of the U.S. Drought Monitor shows drought conditions overspreading almost everyone along and west of the Continental Divide. The very worst drought conditions exist over the Four Corners region, but parts of the Pacific Northwest—especially in Oregon—continue to slip into deeper levels of drought. Conditions have actually improved somewhat in northwestern Washington, where some areas have managed to escape drought over the past month or so.


We have the chance to erase some of those rainfall deficits over the next couple of days. Several rounds of rain will move ashore in the Pacific Northwest through early next week, bringing a general swath of 3-5" of rain to western Washington. The highest totals will fall in the mountains, where the highest elevations will see some precip fall as snow, while the Weather Prediction Center predicts about 3" of rain around the Puget Sound in the coming days.

Long-range models continue to show waves of rain moving across western Washington over the next week or so. While this will help erase some of that steep precipitation deficit in some areas, it won't do much to ameliorate the worsening drought in Oregon. The Climate Prediction Center's latest precipitation forecast for the next three months shows heightened chances of below-average rainfall in interior parts of Washington and Oregon, while equal chances for above- or below-normal precipitation exist along the coast.


You can follow me on Twitter or send me an email.

Please consider subscribing to my Patreon. Reader-funded news is more important than ever and your support helps fund engaging, hype-free weather coverage.
 

October 19, 2018

Texas' Lake Travis Approaches Record Levels as Heavy Rain Continues

It's been pretty calm across most of the United States for the past week, a far cry from what we've experienced for...well, the entire year up until now. Hurricane Michael is out of the picture, the raging Santa Ana winds in southern California have calmed down, and the rest of us only see the occasional passing shower, if that. The only active weather in the United States right now is a persistent slog of heavy rain over Texas, and the persistent slog of rain for days on end is leading to some pretty big flooding problems.

Parts of Texas have recorded more than a foot of rain over the past week. The heaviest rains have fallen in the central part of the state. Much of that rain fell in a short period of time, and much of it fell across the Colorado River watershed.

The surge of water into the Colorado River led to a significant rise in Lake Travis, northwest of Austin that's created by the Mansfield Dam. Water levels in the lake have exceeded major flood stage, and the pool is just six feet shy of its record high of 710 feet. The excess water in Lake Travis is flooding surrounding communities. Water levels are so high that officials may have to open all eight flood gates on the dam, something they've never had to do before.

The National Weather Service has flood characterizations for every major waterway in the country, detailing the kind of flooding you can expect once water levels reach a certain point. Here are the characterizations for flooding on Lake Travis:

714 Flow reaches and goes uncontrolled over the emergency spillway over Mansfield Dam at Lake Travis. Hundreds of homes around Lake Travis flood, many with water well over their roofs or in the second floor level.
710 Hundreds of homes around Lake Travis at Graveyard Point at Lakeway flood with water well over some roofs and into the second floor of lower homes.
705 Disastrous residential flooding of hundreds of homes occurs around Lake Travis at Graveyard Point at Lakeway, many with water over their roofs in up to 17 feet of water.
700 Many homes flood at Graveyard Point at Lakeway on Lake Travis, some with water to their roofs in up to twelve feet of water.
695 Lowest temporary and mobile homes in Graveyard Point at Lakeway on Lake Travis have up to seven feet of water in them.
691 The lowest permanent homes at Graveyard Point at Lakeway on Lake Travis flood. Several temporary homes are in several feet of water.
688 Lowest temporary and mobile homes at Graveyard Point at Lakeway on Lake Travis flood.
685 The lowest temporary and mobile homes at Lakeway at Graveyard Point on Lake Travis are threatened.

The lake is just a few inches shy of the level at which "disastrous residential flooding" is possible, and any further rise in water levels will have a significant impact on surrounding communities.

The region isn't hurting for rain anymore. Drought conditions that existed across large parts of Texas for the past year vanished with the onset of heavy rains over the past month. Only small pockets of drought conditions remain over parts of Texas that largely avoided the recent rains.

Heavy rain will continue across parts of the southern Plains through Saturday, and the greatest chances for heavy rain over the next week will be confined to southern Texas and the Gulf Coast.


You can follow me on Twitter or send me an email.

Please consider subscribing to my Patreon. Reader-funded news is more important than ever and your support helps fund engaging, hype-free weather coverage.