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:

jan4-1015amclouds

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

jan4-11amtemps

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

jan4-11amwc

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

jan4-afternoon

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:

jan4-evening

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

jan4-thursday

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):

jan4-snowfall

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:

jan4-ride

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:

jan3-11amradar

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:

dec13-11atemps

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

jan3-afternoon

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

jan3-evening

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

jan3-overnight

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:

jan3-wednesday

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:

jan3-snowfall

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:

jan3-screaming

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:

dec7-blog-snow

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:

dec7-wednesdayamgfs

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

dec7-tuesdaypmgfs

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:

dec7-wednesdayamec

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:

dec7-tuesdaypmec

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:

sep9-ffw

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:

sep9-spctonight

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:

sep9-spcsaturday

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

sep9-impacts

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:

sep7-2pmthursday

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

sep7-2pmfriday

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:

sep7-spcthursday

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

sep7-spcfriday

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:

sep7-thursdaythreats

And here is the breakdown of threat for Friday:

sep7-fridaythreats

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:

may19-oldwatch

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:

aug18-watchtext

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

aug18-watchcounties

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:

aug18-watchboxexample1

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?

aug18-watchboxexample2

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:

aug18-watchboxexample3

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?

aug18-watchboxexample4

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:

aug18-watchboxexample5

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.

 

aug18-watchboxexample6

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:

aug17-reflectivity

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:

aug17-velocity

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:

aug17-cc

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:

aug17-radarloop

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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