Update on Tuesday’s Severe Storm Threat

This morning, the Storm Prediction Center placed the entire Tri-State in a slight risk for severe storms on Tuesday and Tuesday evening:


A review of the latest model guidance suggests there will be modest instability (in purple) over the Ohio Valley Tuesday:


The black dot is Cincinnati. The highest amount of instability will likely be positioned west and southwest of the Tri-State.

The jet stream will be overhead Tuesday afternoon, with the highest wind speeds to the west of the Tri-State. Favored areas for lift in the atmosphere are highlighted in blue:


This is not impressive lift over the Tri-State, but it helps. How about the placement of upper-level disturbances? Here’s what Sunday morning’s NAM model things by 4pm Tuesday:


Disturbances are highlighted in blue. Lift in the atmosphere will be highest ahead of these disturbances (which will move from west to east).

How is the tornado threat looking? Let’s assess this threat using the Significant Tornado Parameter (STP). Values of 1 or highest suggest an elevated risk for tornadoes. Here’s what the NAM projects for STP at 4pm Tuesday:


Values of 1+  are in light yellow, so there is a risk for tornadoes Tuesday…BUT it is a secondary threat at this time based on review of other data.

Do we have moisture available to storms? Here’s the dewpoint forecast during the work week:


We don’t need to be humid in February to get strong or severe storms, but higher dewpoints suggest an increased likelihood for storms. Dewpoints in the mid 50s is high enough to strong strong storms in the cold season.

After a review of these parameters and a bunch of other data, the slight risk seems appropriate for Tuesday, with damaging straight-line wind and large hail being the main threats:


I’ll update this threat as time permits on Monday and Tuesday.

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Severe Storm Threat Tuesday: Knowns & Unknowns

The Storm Prediction Center has placed the Tri-State in a risk for severe storms on Tuesday, highlighted here:


For this and all graphics below, Cincinnati is labeled with a green dot. What type of risk is this? Think of it as a “slight” risk for now. A formal classification of “marginal,” “slight,” “enhanced,” “moderate,” or “high” is only used for a given day and the two days that follow it, so we will get the category tomorrow.

What is contributing to this risk? First, strong or severe storms need access to instability. Warm, moist air at the ground and cold, dry air aloft will help air to rise and create storms. Here’s what Saturday morning’s NAM model thinks for instability at 4pm Tuesday:


Modest amounts are in the purple, and higher amounts are in the blue. Even the purple shades can support storms, but other ingredients need to be in place (especially in the colder months of the year) to get thunderstorms.

Will it be warm? That’s important. I see temperatures only dropping to near 50° early Tuesday…


…and rising into the 60s Tuesday afternoon:


That’s more than warmth enough to see thunderstorms, including strong and severe storms.

How about moisture? Here’s the dewpoint forecast for the next few days:


We don’t need to be humid this time of the year to get strong or severe storms, but the dewpoint almost always needs to be above 50° to get severe storms in February.

How about lifting mechanisms for the assist? The NAM model (like others) has several compact disturbances (orange/red colors) over the Ohio Valley Tuesday afternoon:


…this supports storms, but it’s not impressive lift. How about the jet stream? Here’s what the NAM thinks at 4pm Tuesday:


Jet stream level wind speeds are in blue, and upper-level divergence of air (promoting lift) are in contours of pruple. There is also lift in the “left-exit” region of the jet streak (part of the jet stream) over the Tri-State. This lift overhead will support storms, but it’s not big time lift.

How about wind shear (the change of the wind speed or direction with increasing altitude)? The NAM has plenty of that:


Remember this is SPEED shear shown here, not directional shear (a lot of the latter supports tornadoes).

How about helicity (a measure of how likely storms are to rotate)? The NAM has us in a 200 m2/s2 area:


What the heck does that number mean? The threshold for what supports severe storms can vary from one season to the other, but this is significant to mention a tornado risk somewhere in the Ohio Valley. Let’s not discuss the level of this risk for now, but instead, acknowledge that this threat should be watched.

How about the SHERB parameter? What’s that? See more on this in this blog post from 2015. This is a helpful parameter in severe weather setups when instability is low. Now that that’s been explained, here’s what the NAM thinks for SHERB at 4pm Tuesday:


Any value over 1 with thunderstorms in the area suggests those storms may be strong or severe. How about effective SHERB (in simple terms, SHERB but accounting for storm depth) at 4pm Tuesday?


Again, values are near or just above 1, which supports a strong to severe storm threat.

So what do I think about Tuesday’s severe storm threat? Here’s my latest thinking based on the setup and acknowledging uncertainty:


Stay tuned. This threat may change, and new guidance will help to target areas that have a better threat versus other areas.

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Snow Likely Thursday

While snow is coming Thursday, the sky will be sunny to mostly sunny this afternoon. A 10:15am cloud snapshot of the Ohio Valley shows some clouds to the northwest moving southeast:


Despite sunshine, it is still cold. As of noon, temperatures are in the mid to upper 20s for most:


A sustained wind between 10 and 20mph means it feels colder. Wind chills in the Tri-State are in the teens and 20s:


Temperature will barely rise this afternoon thank to a westerly wind dragging cold air in from the Plains and Mississippi:


The influence of low pressure will begin tonight in the form of high- and mid-level clouds increasing. Plan for temperatures fall through the 20s:


Snow is likely Thursday. The coverage will increase in the morning, be steady for most of the afternoon, and end Thursday evening:


Temperatures in the low to mid 20s will mean snow-to-liquid ratios will be higher than usual. This means that liquid-equivalent precipitation (all forms of precipitation melted down) will need to be multiplied by a factor that is higher than usual. A baseline ratio for temperatures in the upper 20s and low 30s is 10:1. Given that temperatures will be in the low to mid 20s, this snow-to-liquid ratio is more like 18:1. Remember, 10:1 or 18:1 are snow-to-liquid ratios, NOT forecast snow totals. I am explaining the meteorology of taking what forecast models produce to a snow forecast. Models are producing 0.1″ to 0.18″ of liquid for this event (all snow), so totals of 2-4″ totals look appropriate for most, but not all. Here’s what I’m thinking for event total snowfall (Thursday and Thursday night):


This is a significant increase in amounts compared to 24 hours ago. This will not be a winter storm, per se…but it will be significant winter weather event. Roads will at least be wet on Thursday, and they will likely be snowy in spots with pavement temperatures in the 20s. Snow squalls are unlikely tomorrow, but the visibility will be reduced by snow…especially in the late morning and first half of the afternoon Thursday:


Red lights for travel conditions are somewhat rare for me. Again, this does not appear to be a winter storm, but impacts will be significant!

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Rain Showers Today, Snow Showers Thursday

Scattered showers are forecast through the lunch hour. Regional radar shows rain showers moving from west to east through the Tri-State:


Notice the break in showers over west-central Indiana. That break is over the Tri-State by mid-afternoon, but the area of rain showers in Illinois will overspread the Tri-State late in the business day and this evening. The amount of lift in the atmosphere is increasing to the west, so plan for more showers later today and tonight after a brief break this afternoon.

It’s warm outside! As of 11am, temperatures are in the 50s:


Temperatures will be gradually falling through the 50s this afternoon with showers favored early and late:


Showers will continue this evening as temperatures fall through the 40s:


Showers will diminish late tonight, briefly mixing with flurries, especially northwest of Cincinnati:


Notice the quicker fall in temperatures late tonight compared to this evening! We’ll start Wednesday in the upper 20s and low 30s. Little if any warm up is forecast Wednesday, even with decreasing clouds:


Wednesday will be a much colder and breezy day. The next wave of precipitation (Thursday) will be in the form of snow showers. Models are getting more aggressive with the strength of this wave, so up to 1″ of snow is forecast Thursday:


Notice that no Tri-State community is favored for more or less snow. Snow showers implies snow that starts and stops. Here is a summary of late week impacts:


Snow showers will increase in coverage Thursday morning, decrease in coverage late Thursday, and cold air will plunge into the Ohio Valley behind this wave. Lows will be in the low to mid teens and highs will be in the mid to upper 20s Friday through Sunday.

Snow squalls are unlikely Thursday, but there will be drops in visiblity underneath snow showers.

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An Annual Reminder: Think Before You Share Weather Posts

While the courtesy applies to any time of the year, the courtesy of “thinking before you sharing weather-related posts” especially applies to the colder months of the year.

As a meteorologist, I look at a look of computer forecast model data daily. This is often referred to as “guidance” for a reason; these models are designed to “guide” the decisions of meteorologists while making a forecast. Sometimes the guidance is wrong, and sometimes it is right. Sometimes one model will propose one solution, and other model will have a different idea of how the weather will change.

You may have seen some of this guidance without even knowing it. If you see a map of snowfall totals that doesn’t look like a human being created it, that’s likely computer model guidance. It’s raw computer output, so it’s not a forecast. That one computer forecast model may look very different from the model run before it or different types of computer forecast models. But all you likely see in that social media post is what one model at one time thought. It may not be current; it may be a map saved from years ago and just re-posted.

Sometimes the maps you see are created by a human, but not by a meteorologist or someone with years of forecasting experience. For example, someone messaged me this screenshot from the other day on Facebook asking if it was true:


Who was this created by? Do you know them? Did their forecast from last time verify? These are questions you should ask yourself. This post had hundreds of shares when I researched it. Why? Because it’s scary. Blizzards are rare. True blizzard conditions usually don’t cover multiple states and aren’t forecast 5 to 7 days in advance. A lot can change in a span of a few days, especially when the system hasn’t even developed yet. But it gets shared on social media because it’s potentially scary.

How often do forecasts change in the weather world? Here’s a forecast for atmospheric pressure (black lines) and precipitation (colored contours) from Wednesday morning’s GFS model for the Ohio Valley, New England, and Great Lakes for 7am Monday morning:


Cincinnati looks dry. Here’s what the same model (GFS) had forecast for the same time (7am Monday) 12 hours earlier:


Cincinnati also appears dry here, but notice a forecaster using this model in Boston may have some trouble because precipitation amounts differ.

Let’s take another model, the ECMWF. Many meteorologists feel, over long periods of time, that it’s more accurate than the GFS. Is it? Here’s the forecast for atmospheric pressure (black lines) and precipitation (colored contours) from Wednesday morning’s ECMWF model for the Ohio Valley, New England, and Great Lakes for 7am Monday morning:


That’s a lot different that what Wednesday morning’s GFS model showed. That’s also a lot of precipitation. Some of it may be snow and some of it may be rain, depending on the temperature at various levels of the atmosphere. Here’s what the ECMWF had forecast for 7am Monday just 12 hours earlier:


That’s quite a difference in 12 hours. Precipitation amounts are much different in the Ohio Valley and Great Lakes…plus the center of low pressure (closed off black lines) is in a much different spot.

So which one is right? That’s why meteorologists go to school for 4 years to study math and science. They throw the book at us and teach us how these models behave and work. What isn’t learned through education is learned through experience. This knowledge is not a part of a social media post showing massive amounts of snow, ice, cold, and a blizzard days or weeks out. Realistically, a social media poster wanting “likes” will post Wednesday morning’s ECMWF precipitation forecast because it’s scary and (if it verified) would be quite disruptive to travel.

So before you share a weather-related social media post, think of these:

  1. Who posted this information? Are they a meteorologist? Do you know them? Do they actually forecast the weather, do or they just post computer forecast model graphics? Have they been right before? Do you trust their forecasts?
  2. Who shared this information? If it’s a trusted source of information, then it’s probably giving you more truth than lies. If it’s a friend that shares everything and anything, then it’s probably a good idea not to share it and go to a trusted source.
  3. Did they post model output or did they make an actual forecast? Odds are higher that the outcome they are predicting will be right if it’s an actual forecast (meaning it doesn’t just look like a computer made it). Remember, snowfall forecasts usually have ranges not specific numbers for cities because wise forecasters and meteorologists acknowledge variability and uncertainty.
  4. A forecast for a massive storm or hazard several days or weeks out – especially if it is a very specific forecast – is usually wrong to dead wrong. When it doubt, don’t share it.
  5. Computer forecast models often overdevelop areas of low pressure in the long range (7+ days), so of course they are going to produce big storms as you go farther into the future.
  6. Some meteorologists hype. It’s just a fact. I hate it, and you hate it. Don’t fall for the hype. Remember if that meteorologist or forecast got it right last time. When I say “got it right,” I mean “was responsible,” “not scaring you then changing their thinking last minute,” and “at least in the ballpark with amounts and impacts.”
  7. When in doubt, don’t share it. There are a lot of teenagers out there who have no formal training in the weather posting scary images just to get your attention and likes. Would you trust a teenager with your car if he or she said they were a mechanic, or would you look for someone with experience and certification in their field? Education and experience aren’t everything, but it should count for more than something.
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Flooding And Severe Threat Through Saturday Night

A Flash Flood Watch has been posted for much of southwestern Ohio and southeastern Indiana, thanks in part to saturated soil after last night’s heavy rain:


While the coverage of showers will be low through mid-evening, scattered showers and thunderstorms will develop late this evening and early in the overnight. There is a risk for strong storms tonight, but the main concern is flooding and flash flooding in the watch area.

The Storm Prediction Center only has communities northwest of Cincinnati in the marginal risk for severe storms through sunrise:


Even if storms aren’t strong or severe, they may produce heavy rain and frequent lightning.

While the Flash Flood Watch will expire at 6am, the threat for flooding and heavy rain returns Saturday afternoon and evening. The threat for strong and severe storms will also be higher Saturday, especially for areas east of Cincinnati:


The most likely time for storms – including strong to severe storms – Saturday is 2pm to 9pm. Damaging straight-line wind is the main threat:


The key takeaways here are to be aware for flooding and strong storms through Saturday night. The risk for both of these is highest northwest of Cincinnati tonight and along and east/south of I-75 and I-71 Saturday afternoon and evening. Never drive through flooded roads!

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A Threat For Strong And Severe Storms Thursday And Friday

While the threat is small, you should be alert for strong and severe storms Thursday and Friday, especially during the afternoon. Even if storms aren’t strong, some cells may produce heavy rain and lightning.

Models are quite sloppy with the coverage and timing of showers and storms Thursday and Friday. Wednesday morning’s NAM model has precipitation developing in the Ohio Valley around 2pm Thursday afternoon:


The same model also has showers and storms developing in the Tri-State Friday afternoon:


Other models and guidance is not as aggressive with the coverage storms both Thursday and Friday. My forecast for Thursday calls for scattered showers and storms developing, especially during the afternoon and ending in the evening.

The Storm Prediction Center has placed areas west and north of Cincinnati in a marginal risk for severe storms Thursday:


The marginal risk is farther west in SPC’s severe weather outlook for Friday:


At this point, all severe weather threats for Thursday and Friday are low and mainly during the afternoon and early evening. Here’s are forecast severe impacts for Thursday:


And here is the breakdown of threat for Friday:


Be alert! This threat may change in the next 24 to 48 hours.

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It’s Time To Stop Issuing Tornado And Severe Thunderstorm Watch Boxes

No, I don’t want the Storm Prediction Center to stop issuing Tornado and Severe Thunderstorm Watches. I just want them to stop issuing the boxes.

If you’re confused, I’ll explain.

If the Storm Prediction Center feels there is an organized threat for severe or tornadic thunderstorms, they will issue a Severe Thunderstorm or Tornado Watch. But what exactly do they issue? Years ago, they would draw a parallelogram (like the one pictured below), and other text bulletins:


If you were in the box, you were in the watch. If you were out of the box, you weren’t in the watch. It was that simple.

Nowadays, the box is issued, but so is a list of counties in the watch. First the box comes down:


Then the county list comes down (this example is a status update, not the initial update):


No problem, right? You see the box, you see the counties, and you know whether you are in the watch or not. Right? Not always.

Sometimes the watch and the counties don’t match up. Here’s a watch from earlier this year:


Is Charleston, West Virginia in the watch or not? Charleston is outside of the box, but is in a highlighted county. How about another example? Suppose you’re watching TV in Rapid City, South Dakota. Are you in this watch?


If the TV meteorologist on Channel A shows only the box, you’re “out” of the watch. If the TV meteorologist on Channel B shows only the counties, you’re “in” the watch. If the TV meteorologist on Channel C shows both, you’re “in” and “out” of the watch.

Here’s another tricky one:


What if you were in the southeastern part of the county just east of Colorado Springs? This area is in the box, but not in a highlighted county.

How about a watch where a few counties west and north of the box aren’t even close to the edge of the box?


Because the box “must” be a parallelogram, SPC color outside of the lines. Or perhaps the local National Weather Service forecast office wanted to include areas in the watch, and the SPC agreed. Storms rarely fit in parallelograms.

It gets more confusing. Suppose the threat for severe storms is high, and a Particularly Dangerous Situation Tornado Watch is issued:


This Particularly Dangerous Situation is particularly confusing. If you’re in Fort Campbell, Kentucky, are you in this watch? This is a bad time to be unsure. There were several strong tornadoes in this watch.

What about when several counties in the box are not in the watch? It has happened.



So let’s go back a second…was Charleston, West Virginia in the Severe Thunderstorm Watch above? The answer is yes. How about Rapid City, South Dakota? They were. Fort Campbell, Kentucky? Yes. The box doesn’t define the watch; the county list does. In other words, if your county is on the list, you’re in the watch. The box doesn’t matter.

Suppose a pair of watches are put up side by side, and you’re on the edge. One watch is in effect through 3am, and the other is in effect through 6am. There’s a big difference there. That’s a lot of lost sleep if you think you’re in the second watch and actually in the first.

This brings me to my point: it’s time to stop issuing Severe Thunderstorm and Tornado Watch boxes. Being in the box or out of the box means nothing, so why issue it? The box is a legacy product that is outdated and only confuses those reviewing the watch. The box idea worked in the 1960s, but it doesn’t work now. The only reason I can think the box is around is the Internet and media. Intellicast.com will show Tornado and Severe Thunderstorm Watches in box form. Some TV meteorologists will, too. I’m not sure why they do. But change is slow, so I suppose it’s easy to not make a change.

I’ll argue, however, this change needs to be made. Severe Thunderstorm and Tornado Watches are not life or death, but they are likely the most – at least least one of the – important types of watches issued. Many people have died in these watches. The last thing I want is for someone to get hurt or killed because they weren’t sure if they were in the watch.

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Confirmed Tornado In Sardinia

At approximately 11:16am Wednesday morning, a tornado damaged homes in the city of Sardinia, Ohio (of north central Brown) County. The National Weather Service confirmed the tornado at 3pm this afternoon, but radar actually confirmed the tornado shortly after it occurred.

Here was the snapshot of radar reflectivity (the shower and storm mode) from the National Weather Service radar at 11:16am Wednesday:


The Tornado Warning is outlined in red. Note the weaker echoes between stronger echoes in the image above compared to the radar velocity (the “Doppler” part of Doppler radar) below:


In the highlighted area, the wind on the west side of the storm is moving away from the radar to the north of the storm (the red area), and the wind on the east side of the storms is moving towards the radar to the north of the storm (the green area immediately right of the red area). This is the circulation associated with the tornado.

How was it possible to confirm this tornado in real-time? See the correlation coefficient image from the National Weather Service’s radar at the same time:


That “cool” colored spot in the middle of red colors is a debris signature. It is very close to the rotation on radar and the hook seen in the reflectivity image. Correlation coefficient shows the correlation in shape and size of objects (raindrops, hailstones, etc) in each pixel. A high correlation (red colors) between objects suggests objects the radar samples are relatively the same size and same shape. A low correlation (cooler colors) suggests objects are of different shapes and sizes. In this case, the objects are pieces of trees, someone’s home, or crops being lofted into the air and being sampled by the radar. As a meteorologist, you hope you don’t see this. This signature (really, all three of them) confirmed the damaging tornado shortly after it caused damage.

See the comparison of the products:


The tornado had a damage path that was 1 mile long and up to 100 yards wide. The maximum wind was 75mph. This was the first confirmed tornado in Brown County since March 2, 2012; the 2012 tornado also went through Moscow, one of the deadliest Tri-State tornadoes in recent history.

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Why The Dewpoint Needs To Be A Part Of Official NWS Weather Records

Everyone knows the word moisture. It is a fundamental ingredient for making precipitation or even keeping it away. It is the reason why it was humid today; the more moisture there is in the air (the higher the dewpoint), the more humid it is. The dewpoint is critical for knowing whether clouds will form or whether they will break apart. The dewpoint has either a direct or indirect impact on the strength, positioning, and timing of all weather systems. The dewpoint (a temperature) can impact the air temperature and what type of precipitation falls at the ground and aloft.

For some reason, though, the dewpoint is not listed in official weather records (kept by the National Weather Service in the United States). When you look at weather records for the month of July 2016 in Cincinnati (so far), the maximum, minimum, or average dewpoint is nowhere to be found:


Records of air temperatures, precipitation, snowfall, wind speeds, and even snow depth are kept every single day. Yet the dewpoint is not here. Why?

The dewpoint is so important that is it listed not once, but twice in airport weather observations:


The red number is the dewpoint to the nearest whole number (°C), and the green number is the dewpoint (°C) in tenths (and the first “0” or 1″ here is used to indicated whether the dewpoint is positive or negative, respectively). It’s important enough to go here, but not in official weather records?

The dewpoint is so important it is measured vertically using a weather balloon (to the top of the troposphere, the layer of the atmosphere that we live in and where weather occurs) twice a day at numerous sites around the country and the world. Here’s the weather balloon “sounding” from 8pm Thursday night from Wilmington, Ohio:


Guess what the green line is? It’s the dewpoint! It’s right next to the temperature in red! Wind directions and speeds (listed as barbs on the far right) are also listed. And that’s it for a weather balloon sampling! Every other variable is derived. If the dewpoint makes the variable list here, it should be in official weather records

You want to know what the record lowest or highest dewpoint was at a pressure of 850 millibars (about 5,000 feet above the ground) back to the early days of when weather balloons were launched? Here you go! It’s all here! Want to know how the average dewpoint this month compared to last month or last July? It’s not easy; even the most data savvy meteorologists will need time to make this calculation.

Keep in mind, temperature ranks for a week, month, year, decade, or ANY stretch of time are done by averaging the average temperatures for each day in that period. The average temperature for the day is simply the high and the low divided by 2. I can calculate the average temperature for a year or month and compare it to a similar length of time easily because high, low, and average temperatures are listed in official weather records. High, low, and average dewpoints are not. Comparing the average dewpoint for one year to another can take hours. It should take minutes.

Part of the argument is that dewpoint records don’t go as far back as temperature records. Hourly dewpoint records for Cincinnati go back to the late 1930s, but temperature, rainfall, and snowfall records go back to 1870, 1870, and 1893 (officially and respectively). So it’s not the same period of record…but so? Records are records. The first half of 1872’s temperature records in Cincinnati are gone; they were lost in a fire. We didn’t throw out the entire record on account of some records being lost. Jackson, Kentucky’s weather records (at the National Weather Service office there) began in 1981, some 100 years after Cincinnati’s records began. Still, we aren’t throwing out weather records from Jackson because their period of record is less than 40 years.

It’s time to add the maximum, minimum, and average dewpoint to official climate records for the United States. Moisture in the air is fundamental to understanding what type of weather occurs and how poor conditions will be. The public, not just meteorologists, should have knowledge of how weather conditions are changing so that we can see how moisture is moving over time and space. With a large enough period of record in place, dewpoint records will add to the ongoing discussion about climate change and give all a better indication of whether certain areas are more humid or less humid over time.

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