January 19, 2019

A Disruptive Weekend Storm Will Blanket Much of the Northeast With Over a Foot of Snow



The early flakes of a widespread and disruptive winter storm are already flying across parts of the Plains and the Midwest as a low-pressure system gets its act together and heads east. This weekend's winter storm will produce a large swath of snowfall in excess of one foot from the Ohio Valley to New England. Isolated areas just south of the rain/snow cutoff could see a damaging ice storm.

Snow, ice, and a chilly rain will continue to develop through early Saturday morning as a low-pressure system gathers organization and strength in the Midwest. Heavy precipitation will spread across the Midwest and Ohio Valley through daybreak on Saturday. The heaviest snow should reach Ohio and Pennsylvania by Saturday evening, spreading through the rest of the Northeast overnight Saturday and into Sunday.



This will be a disruptive snowstorm for just about the entire Northeast save for the immediate coastline. The National Weather Service expects a foot or more of snow to fall from northeastern Ohio through the Canadian Maritimes. The heaviest snow will fall from central Pennsylvania through Maine, where snowfall totals of 18-24" are likely, with higher totals in higher elevations. Exact snowfall totals really stop mattering once you get this high up the yardstick, but in an instance like this, more snow will lead to a thicker slab of glacial ice encrusting the Northeast once temperatures plummet behind the storm.

If you're wondering what's up with that weird bullseye of snow over the Chicago area, the NWS is predicting double-digit snowfall totals in northeastern Illinois thanks to an expected lake effect snow event on Lake Michigan this weekend. Models continue to suggest that one or more bands of north-south oriented lake effect snow will develop on Lake Michigan and blanket its southern shores with extra snow on top of what falls during the big storm. The main shield of snow with the storm is expected to continue through Saturday afternoon. There should be a brief lull before the lake effect snow picks up on Saturday night and continues through the day on Sunday.

Back east, there will be a sharp cutoff between the rain and the snow. That's tricky business when the event will take place so close to so many major metropolitan areas. The entire I-95 corridor between Philly and Boston is close enough that it would only take a southward nudge of a few dozen miles in the storm's track to bring heavier snows into the major metro areas. Forecasters don't believe that's the most likely scenario at this point, but it's always worth keeping in mind that the cutoff of heavy snow isn't that far away.

Source: NWS EDD


The transition zone just to the south of the snow will feature sleet and freezing rain for a period during the storm. The latest forecasts from local NWS offices show the possibility for a crust of ice from Virginia through Maine, with the most significant icing possible in western Maryland and southern New England. Those spots could see up to half an inch of ice accretion from freezing rain according to the latest forecasts, which would cause widespread tree damage and power outages. We had 0.30" of ice from freezing rain here in my part of North Carolina last weekend and some people in my town were without power for three days. Snow is bad, but ice is worse.

Hundreds (if not thousands) of flights will be delayed or cancelled due to the combination of wintry precip, heavy rain, low visibility, and trickle-down effects from connecting airports. Rail service will likely be delayed or cancelled due to snow and ice. Travel by car will be nearly impossible in areas that see more than a foot of snow. I wouldn't be terribly surprise if we wind up with news of people getting stuck on the side of the highway when the heaviest snow starts cranking.

The snow that falls won't go anywhere anytime soon. Temperatures are going to crash through the floor as bitterly cold air floods in behind this storm system. The freezing line will make it as far south as Florida on Sunday and Monday nights as the cold snap rotates through the eastern half of the country. Many communities in the Midwest, Great Lakes, and Northeast will see temperatures in the single digits and below zero for a couple of mornings. Monday will be the coldest day; highs on Monday will struggle to climb above zero in western New York.

Temperatures this cold will freeze solid any snow, sleet, and ice through the middle of next week. It will be extremely difficult to remove lingering snow from solid surfaces once it gets this cold. We could also see a flash freeze on Sunday as the bitterly cold air washes over wet roads where most of the precipitation fell as rain, so keep the potential for unexpected black ice in mind if you're out and about on Sunday.

We're heading into an active pattern for the final half of January. This is just the first round. It's too early to say what's to come, but it's certainly going to stay cold for most of us east of the Rockies.



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January 17, 2019

Former AccuWeather CEO Barry Myers Renominated to Run NOAA



President Donald Trump on Wednesday renominated former AccuWeather CEO Barry Myers for the position of NOAA Administrator. Myers' nomination has been stalled since October 2017 due to opposition over his conflicts of interest and general pleasure with Acting Administrator Tim Gallaudet's performance on the job. His nomination expired at the beginning of the month with the end of the 115th Congress.

The (now-former) CEO of AccuWeather faced opposition for the head job at NOAA as the company he and his brothers have run for decades considers the National Weather Service a direct competitor. Critics worry that Myers would use his position to diminish the reach of the NWS in favor of his family's Pennsylvania-based weather company, or use the office to make decisions for the financial benefit of weather companies such as his own.

I elaborated on some of the worries when Myers' nomination expired a few weeks ago:
The greatest single point of opposition to Barry Myers leading NOAA is the many conflicts of interest that would follow Myers into office. The greatest example of these potential conflicts was his company's support for S.786—the National Weather Service Duties Act of 2005. The bill, introduced and unilaterally supported by former Sen. Rick Santorum (R-PA), would have effectively privatized the NWS and used the agency to subsidize private weather companies.

Santorum's legislation would have required the National Weather Service to stop issuing public forecasts except for "severe weather forecasts and warnings designed for the protection of life and property of the general public"—in other words, it limited the agency's public portfolio to emergencies like tornado warnings. All of their other forecasts, products, and data had to be provided "through a set of data portals designed for volume access by commercial providers of products or services," turning private weather companies into middlemen between the NWS and the public. 

[...]

A failed piece of legislation from a decade-and-a-half ago isn't the entire reason for opposition to Myers' nomination. But it typifies the potential that exists for Myers to act in ways that benefit companies like AccuWeather. The nominee would enter office with enormous conflicts of interest in tow. If Myers became the NOAA Administrator, he would control the agency that directly competes with his company. Even if Myers divested from AccuWeather, his brothers still control the company and he has a vested interest in seeing his family's company thrive against the direct competitor he would control.
Myers will also be one of the only NOAA Administrators in the agency's history not to hold a science degree.

The move did not come as a surprise. AccuWeather announced earlier this month that Myers resigned his position as CEO on January 1 and divested his financial interest in the company. Myers' renomination to the post, along with his resignation and divestiture from AccuWeather, is a sign that the increased Republican majority in the U.S. Senate will likely confirm Myers to the position at some point in the near future.

[Top Image: Pierre cb via Wikimedia Commons]

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Thunderstorms Roll Across Central California as Potent System Drenches West Coast



A strong low-pressure system rolling through the northeastern Pacific Ocean is responsible for the latest wave of precipitation washing over the West Coast. The storm system is so potent that thunder (gasp!) was reported across central California on Wednesday night as clusters of storms moved ashore between San Francisco and San Luis Obispo. The heavy rain will continue through Thursday before a brief break ahead of the next storm system this weekend.



PowerOutage.US tracked more than 100,000 power outages in California late Wednesday night, mostly situated in the central part of the state where strong winds accompanied heavy rain and thunderstorms. The radar was pretty interesting to watch during the height of the storms. A squall line that developed in the Central Valley around 11:00 PM PDT—pictured at the top of this post—would be impressive anywhere else in the country, let alone in California. There were still about 60,000 power outages across California by noon on Thursday.



Much of the West Coast will continue to see heavy rain on and off for the next week. The heaviest of the rain set to fall over the next week will cover most coastal areas from British Columbia through northern California. The higher terrain of southwestern Oregon could see up to seven inches of rain over the next week. The I-5 corridor between Portland and Seattle should see lower rainfall totals, but they're still on track for a couple of inches of rain by the end of the next procession of storms.



It's not just rain the west is dealing with. Higher elevations are seeing snow from this storm—and lots of it. Blizzard warnings are in effect for the Sierras in California as ripping winds blow around the many feet of snow that will fall through Thursday night. Local NWS offices warn that the ridgetops could see wind gusts in excess of 100 MPH with five to six feet of snow possible in some spots. Heavy snow will continue through the Rockies as the latest storm—as well as the next storms behind it—make the trek across the country. (PS: Yes, that's a lot of snow back east. Yes, I will cover that in another post.)

Source: U.S. Drought Monitor


The drought situation across the West Coast—and most of the rest of the country, as well—has actually improved slightly over the past couple of months. Above is an animation showing the difference in drought conditions between the beginning of last November and today's update for January 15. The drought has worsened a bit in central and northern California where they haven't gotten as much precipitation as they historically do by this point in the rainy season. Elsewhere, though, it's improved a bit. It hasn't improved all that much, but any improvement is a step in the right direction.


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January 10, 2019

Here's What We Do (And Don't) Know About This Weekend's Snowstorm



A winter storm will move across the Midwest and Mid-Atlantic this weekend, bringing a blanket of snow to the center of the country and a mix of rain, snow, and ice to the Mid-Atlantic. A significant chunk of Missouri stands to see more than half a foot of snow from this storm. Exact totals—and even what kind of precipitation will fall—is still uncertain farther to the east.

What We Know


A low-pressure system will develop in the southern Plains on Friday.

This storm system will likely track farther north than the one we saw a month ago that produced epic snowfall totals in North Carolina and Virginia. My little town north of Greensboro, N.C., saw an entire season's worth of snow in one day back on December 9. What does that mean in practical terms? A track farther to the north will also force the warm air farther to the north. This storm also isn't as juicy or intense as the storm we saw last month, either. That will help to cut down on snowfall amounts in many places.

The best chance for snow exists in the Midwest.



If you're looking for a good snowstorm, your best bet is probably to stake out in central or eastern Missouri on Friday and Saturday. The latest forecast from the Weather Prediction Center, which I've mapped out above, calls for a widespread area of 6"+ across a huge chunk of Missouri and central Illinois. The bullseye for the heaviest snow will very likely shift around and change over the next couple of days as forecasters get a better idea of what the storm will do, but if you're looking for snow, it's probably a safe bet to meet it in St. Louis. (Booo. Sorry.)

Aside from specific amounts, the storm's life in the Midwest is a fairly straightforward event. From here on, I'll mostly talk about the effects of the storm once it crosses the Appalachian Mountains.

Something's gonna happen back east.

That's the best non-answer I can give for what is likely to unfold overnight Saturday and into Sunday. The storm will run into too much cold air for everyone in Virginia and North Carolina to wind up seeing plain old rain. Some folks will have a decent, shovelable thumping of snow. Others may see a prolonged period of freezing rain or sleet. Many communities—likely to the south of I-85—will just deal with a cold, annoying rain.

Cold air damming will determine the rain/ice/snow line.

This point is in a similar vein to the big storm back on December 9. That storm was able to produce prolific snowfall totals across N.C. and Virginia in part due to the resilient wedge of cold air that dammed up against the eastern slopes of the Appalachian Mountains. This allowed precipitation to almost entirely fall as snow, plopping a foot or more of snow across dozens of counties.

The cold air damming ahead of this storm likely won't be as intense or resilient as what we saw the last time around. There's going to be a layer of warm air forcing its way above the cold air during the storm, causing at least some of the snow to turn into freezing rain or sleet before it reaches the surface. It looks like the best chances for an ice storm exist in the Piedmont Triad, the border region between Winston-Salem, Greensboro, and Burlington in North Carolina and Danville and Martinsville up in Virginia.

What We Don't Know


What kind of precipitation will fall.

Snow is more likely closer to the Appalachian Mountains in the Mid-Atlantic and along a relatively narrow path between the mountains and the Atlantic Ocean. Delightfully vague, right? That's because it depends on how much precipitation is able to coincide with the best profile of cold air through the atmosphere.

Since Saturday night and Sunday are too far out right now for me to post any WPC/NWS forecasts, here's a look at (forgive me, Weather Twitter, for I am about to sin) what the last ten runs of the GFS weather model have shown in terms of precipitation types. Each image shows what the model thinks will happen at 7:00 AM EST on Sunday. The first image starts with the Monday afternoon run of the GFS model and shows 7:00 AM Sunday according to each successive run of the model through Wednesday evening. This shows us the trends from run to run.

Source: Tropical Tidbits
Don't take it literally—it's just a weather model and there's a bunch of caveats to what it's showing above. But you can see how the rain/mix/snow line shimmies with each update of the model. That's due to changes in the track of the storm and temperature profile through the atmosphere near that transition point. Folks close to that transition zone will likely see multiple precipitation types during this storm, complicating predictions of how much will fall and making conditions exceptionally dangerous for travel by car or foot.

How much will fall.

We can't quantify snow/ice that may or may not exist. Not yet, anyway. The best chance for an all-snow storm will lie well to the north of the low-pressure system's track. The folks who manage to stay all snow will see the greatest snowfall totals, since freezing rain and sleet pack significantly pack down accumulated snow.

Right now, it looks like the higher elevations of the Appalachians and central Virginia stand the best chance of seeing all (or mostly) snow from this storm, which would give them a shot at the best snowfall totals. Farther south, enough ice is possible that it could damage to trees and power lines. Again, it'll depend on how much precipitation falls as freezing rain and how long it lasts.

We'll know a lot more about this storm on Thursday evening and Friday.



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January 2, 2019

AccuWeather CEO's Nomination to Run NOAA Expires as 115th Congress Adjourns

Donald Trump's nomination of AccuWeather CEO Barry Myers to run NOAA will expire without action on Thursday with the adjournment of the 115th Congress. Myers' nomination faced pointed opposition from ethics watchdogs and groups within the weather industry due to the nominee's conflicts of interest, including his company's past support for legislation that would have severely curtailed the National Weather Service's ability to provide weather forecasts and data to the public.

The New York Times reported last month that the Senate will not take up Myers' nomination by the end of the session on January 3, and it was unclear whether Trump would re-nominate Myers to the position once the new Congress begins. 

For the foreseeable future, NOAA—and, by extension, the National Weather Service—will remain under the charge of Acting Administrator Tim Gallaudet, who holds a doctorate in oceanography. Myers, who holds a business degree, would have been a rare NOAA Administrator without an academic background in science. Gallaudet's leadership of the agency has so far been uncontroversial.

Myers is one of hundreds of presidential nominees who didn't receive a final confirmation vote before the Republican-controlled Senate. A whopping 47 percent of executive branch positions that require presidential nomination and Senate confirmation remained unfilled during the first half of Donald Trump's term in office, either for lack of a nominee or through Senate inaction. These positions are currently filled by acting officials or simply remain vacant.

Unlike the protracted battles over other controversial nominees to the executive and judicial branches, the kerfuffle surrounding the AccuWeather CEO's nomination to run NOAA came and went fairly abruptly in the days after the White House announcement in October 2017.

The greatest single point of opposition to Barry Myers leading NOAA is the many conflicts of interest that would follow Myers into office. The greatest example of these potential conflicts was his company's support for S.786—the National Weather Service Duties Act of 2005. The bill, introduced and unilaterally supported by former Sen. Rick Santorum (R-PA), would have effectively privatized the NWS and used the agency to subsidize private weather companies.

Santorum's legislation would have required the National Weather Service to stop issuing public forecasts except for "severe weather forecasts and warnings designed for the protection of life and property of the general public"—in other words, it limited the agency's public portfolio to emergencies like tornado warnings. All of their other forecasts, products, and data had to be provided "through a set of data portals designed for volume access by commercial providers of products or services," turning private weather companies into middlemen between the NWS and the public.

Why would the bill go to such great lengths to dismantle the National Weather Service as we know it? First, some right-leaning meteorologists and weather industry executives routinely criticize the National Weather Service's efforts to directly interact with the public, arguing that the federal government is unfairly competing with private companies like AccuWeather. (Sidenote: this is also the main reason you'll never get an official NWS smartphone app, in case you've ever wondered.)  

The second factor is just pure politics. Joel Myers, the nominee's brother and founder of Pennsylvania-based AccuWeather, donated $2,000 to a political action committee supporting Santorum's failed 2006 reelection bid just days before Santorum introduced the doomed legislation on the floor. It's not exactly breaking news when a company's executives appear to have a cozy relationship with their home state's congressional delegation, but the bill was awful enough—and AccuWeather's tremendous potential benefit from the bill obvious enough—that the donation sent up red flags in the weeks and months after its introduction.

A failed piece of legislation from a decade-and-a-half ago isn't the entire reason for opposition to Myers' nomination. But it typifies the potential that exists for Myers to act in ways that benefit companies like AccuWeather. The nominee would enter office with enormous conflicts of interest in tow. If Myers became the NOAA Administrator, he would control the agency that directly competes with his company. Even if Myers divested from AccuWeather, his brothers still control the company and he has a vested interest in seeing his family's company thrive against the direct competitor he would control. 

Donald Trump can easily re-nominate Myers once the 116th Congress is sworn-in on Thursday. The president could also nominate someone else or simply opt to let Gallaudet continue serving as Acting Administrator for the remainder of the administration. Republicans gain two additional seats in the midterm elections, expanding their majority to 53-47. However, the president's party could easily confirm nominees on a simple majority vote—a luxury they had in the previous Congress, as well, indicating a lack of will to expend the political capital necessary to push Myers into the job.

[Top Image: Pierre cb via Wikimedia Commons]


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December 31, 2018

2018 Is Set To End With The Fewest Tornado-Related Fatalities On Record


A relative lull in tornado activity in 2018 allowed the year to finish with the fewest number of tornado-related fatalities since reliable records began in 1940. Assuming we get through today’s severe thunderstorms without any significant tornadoes, the United States will end the year with 10 deaths attributable to tornadoes.

2018 will end with a little more than 1,100 reports of tornadoes submitted to the Storm Prediction Center. A decent number of those reports were sent in for the same tornado—adjusted for inflation, the agency received reports of just shy of 1,000 tornadoes across the country in 2018. An official count of all confirmed tornadoes will be released sometime in the new year.

Fewest Tornado Deaths




Ten people died as a direct result of injuries inflicted by a tornado according to the latest count from the Storm Prediction Center. This would be the lowest number of tornado fatalities in a year since the National Weather Service’s database of weather-related fatalities began in 1940. The previous record low occurred in 1986 when 15 people died in tornadoes.

Half of this year’s tornado deaths occurred in November or December. Four people died in a permanent building, including two Amazon employees who were killed when a tornado struck the company’s distribution facility near Baltimore, Maryland. Four people died at home, and two others were killed in vehicles.

The record-low number of tornado-related fatalities this year is attributable both to the overall downtick in tornadoes this year, the lack of violent tornadoes, and likely an overall trend of better warnings and tornado safety education.

Below-Average Tornado Activity


Source: Storm Prediction Center


The Storm Prediction Center’s inflation-adjusted tornado count for 2018 shows this year’s tornado activity well below average and near an all-time minimum. Tornado activity was fairly steady through 2018, steadily building up through the year rather than coming in big bursts like we’ve seen in years past.

The biggest single day for tornadoes reports in the U.S. was Halloween, when the SPC received 61 tornado reports, followed by April 13 (46 reports), December 1 (38), July 19 (31), and April 3 and November 11 tied at 28 tornado reports. It’s notable that only two of the six biggest tornado days this year occurred in the springtime, which is typically the peak of tornado activity across the country.

We also made it through the year without recording any EF-4 or EF-5 tornadoes anywhere in the United States, the first such year on record. The last EF-4 tornado in the U.S. touched down in Texas in April 2017, and the last EF-5 struck Moore, Oklahoma, in May 2013.

Where Tornadoes Happened




It’s no surprise that an unusually quiet year populated by off-season tornado outbreaks would see the bulk of tornadoes touch down outside of what is traditionally considered Tornado Alley. The stretch of the Plains from Texas to the Dakotas saw fewer tornadoes than usual. Nobody died in an Oklahoma tornado this year for the first time since 2006.

Most of the tornadoes we saw this year touched down in the southeast or Upper Midwest. There’s a strong argument to be made that the United States’ “tornado alley” is actually shifting (or at least expanding) east toward the Deep South—covering states like Louisiana, Mississippi, and Alabama.

Noteworthy tornadoes occurred in central North Carolina—where an EF-2 tornado cut through the city of Greensboro and very close to where I live—as well as Maryland (hitting the aforementioned Amazon warehouse) and a photogenic tornado that hit central Iowa at the same time a severe thunderstorm capsized a duck boat in Missouri, killing 17 people.

Some Still Strike Without Warning




Tornadoes striking without warning is a popular narrative news organizations use to cover devastating tornadoes. But the fact of the matter is that most tornadoes that injure or kill people are warned in advance—it’s just that some people in the path of the storm don’t hear the warning in time.

However, some tornadoes really can (and do!) strike without warning. I combed through the tornado reports and tornado warnings issued between January 1 and December 30 and found more than 100 tornado reports that didn’t coincide with any tornado warning polygons at any point during the year.

Now, not all of these tornado reports were confirmed tornadoes. Some likely wound up being damaging straight-line wind events once crews took a better look on the ground. But it’s a stark reminder that warningless tornadoes can happen anywhere in the country—from coast to coast—and that it’s more important than ever to take strong thunderstorms seriously even if they lack a tornado warning.



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December 20, 2018

Look At This Entire Trough



An ambitious butterfly could make it from Orlando to Buffalo in a couple of minutes if it flew high enough on Friday. An incredibly amplified trough entering the eastern United States will bring this week to the same dreary close we saw last week. In addition to lots of heavy rain and dangerous thunderstorms in Florida, the resulting surface low could bring some of the lowest air pressures ever recorded during the month of December in the Mid-Atlantic.


A line of severe thunderstorms was ongoing in Florida at the time of this post. It's a classic wintertime severe weather setup for this part of the country. Warm, moist air ahead of an advancing cold front allowed a line of strong thunderstorms to sweep across the Florida Peninsula. Cooler, drier air will follow soon after the rain stops, bringing comfortable conditions as far south as Cuba and Mexico's Yucatan Peninsula through the weekend.



A slog of steady, heavy rain will coat just about every square inch of the East Coast between now and Saturday. Most areas can expect an inch or two of rain with heavier totals likely in areas that experience thunderstorms. Some of the storms in the Carolinas could be severe on Thursday night, packing the risk for damaging winds and possibly an isolated tornado.

That trough is something else. I mean, look at this thing:
An animated model image of the jet stream. Source: Tropical Tidbits

A sharp trough like that is impressive enough on its own, but the combination of the amplified trough and strong winds of the jet stream within will strengthen the surface low moving over the Carolinas tonight and Friday. The latest forecast from the Weather Prediction Center shows the minimum surface pressure at the center of the low potentially reaching 987 mb on Friday as it moves over western North Carolina and Virginia.
December record low air pressures (adjusted for sea level). Add a 9 to the front of every number for the value, which is rounded to the nearest tenth ("888" in Greensboro is 988.8 mb). Source: WPC



A surface pressure of 987 mb is extremely unusual for this part of the country during this time of the year. Surface pressure records compiled by David Roth at the WPC show the lowest air pressure recorded during the month of December in Greensboro, N.C., was 988.8 mb, and 986.5 mb up the road in Roanoke, VA. It'll be a close one.

The lower air pressure itself won't really have much of a direct effect other than kicking up a stiff breeze and possibly making your joints achier than usual. Other than that, it's just a novelty.

[Top Image: Tropical Tidbits]


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December 19, 2018

A Rare Tornado Touched Down Near Seattle on Tuesday



A strong tornado touched down in Port Orchard, Washington, on Tuesday, damaging several homes and businesses along its path. Meteorologists will conduct storm surveys on Wednesday to assign the tornado an EF-Scale rating, but pictures from local news organizations and social media seem to show that this was a formidable tornado in a part of the country that doesn't typically see this kind of weather.

Today's tornado in Port Orchard—which is next to Bremerton and about 30 miles west of Seattle—is a stark reminder that A) tornadoes can happen anywhere in the United States, and B) a significant number of tornadoes in the United States truly occur without warning.

The nasty weather today in the Pacific Northwest is directly tied to the same low-pressure system that generated all of the epic waves that hit the West Coast a couple of days ago. A long fetch across the northeastern Pacific Ocean allowed wave heights to reach 50 feet, posing significant risk to anyone ill-advised enough (to put it nicely) to go swimming or even just wander to the ocean's edge.

Each dot represents a lightning strike on December 18, 2018. Source: LightningMaps.org
Bursts of showers and thunderstorms moved across western Washington during the day on Tuesday, producing dozens of lightning strikes along the way. (That's nothing east of the Rockies, of course, but even one rumble of thunder out west is a talking point for days.) At least one of the thunderstorms was strong enough to tap into enough low-level wind shear to begin rotating.



The thunderstorm that produced today's tornado had a fairly pronounced signature on it as it crossed the Kitsap Peninsula. The storm's rotation grew strong enough to produce a short-lived tornado once it reached Port Orchard. Social media lit up as onlookers recorded a funnel that was mostly obscured by heavy rain but clearly present due to the immense amount of debris kicking up into the air. The thunderstorm quickly fell apart after the tornado touched down as more stable air wrapped in and choked off the instability feeding the storm.

We only had five-minute radar scans of the storms in northwestern Washington today—we're spoiled by rapid-scan radar imagery these days—but we did get a radar sweep at a critical moment: 1:51 PM PST, during or immediately after the tornado touched down and caused the most damage. That sweep took place at just the right moment to allow us to see debris in the air.


Dual polarization technology allows us to see the size and shape of the objects showing up on radar. Correlation coefficient (CC) tells us how similar or dissimilar airborne particles are to one another. Raindrops have a high CC value because they're all pretty much the same size and shape. Tornado debris, on the other hand, has a low CC because you're seeing everything from branches to vehicles being lofted into the air by the tornado.

Here's a two-pane radar image from Port Orchard around the time of the tornado. The left pane shows CC values while the right shows precipitation.


The debris on the CC imagery stands out as the dark blue circle near the center of the pane on the left. The radar beam is about 3,100 feet above ground level when it reaches the location of the tornado. Even if we didn't have videos of the tornado in progress, a quick look at that kind of a debris signature that high above the ground is a sign of a strong and sizable tornado.



It's common to see this somewhere like Alabama or Kansas, but not Washington. The Storm Prediction Center has more than 62,500 tornadoes in its database since reliable records began in 1950. Since then, only about 100 of those tornadoes occurred in Washington.

Heck, there are so few tornado tracks in Washington that you can barely make them out on a map of the whole country. You have to zoom in on the state to see them.

Most of the tornadoes reported in Washington over the past seven decades occurred along the coast, in valleys, and in the eastern part of the state where thunderstorms aren't as hampered by terrain and a stable marine layer as out west. The majority of Washington's tornadoes were relatively weak and short-lived.

The Storm Prediction Center's tornado database shows 121 tornadoes recorded in Washington between 1950 and 2017. More than half of those tornadoes—69 of them—were an F0 or EF-0 on the Fujita and Enhanced Fujita scales. (The Fujita scale was updated as the Enhanced Fujita Scale in 2007.) Only three tornadoes in Washington have produced F3/EF-3 damage. Based on pictures of the damage, today's tornado is likely to get at least an EF-1 rating, if not higher.

Tornadoes are rare in Washington, and strong tornadoes are even rarer yet. They're so rare, in fact, that the National Weather Service office in Seattle hasn't issued a tornado warning in more than four years—including today. Residents of Port Orchard had no tornado warning or severe thunderstorm warning before the tornado touched down. They only knew there was a tornado if it hit them, they saw it, or they heard about it afterwards.

For all the talk of false alarms when it comes to tornado warnings, an uncomfortable fact we have to live with is that quite a few tornadoes actually wind up going unwarned. The National Weather Service fails to issue a tornado warning for 30-50% of all tornadoes that form each year. The agency does better warning for tornadoes that occur during organized outbreaks than in one-off situations like we saw today.


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