SKYWARN, Weather

Unusually high tornado probability in northeastern Indiana May 7

Leave a comment
A map of Indiana showing tornado probabilities in different areas.
Click the image for a higher-resolution view.

A large part of northeastern Indiana has a level 3 of 5 (enhanced) risk of severe weather Tuesday, May 7, 2024, with tornados, damaging straight-line wind and large hail all possible, according to an outlook that the National Weather Service Storm Prediction Center (SPC) issued at 1:30 p.m. today, May 6.

The level 3 risk is largely due to a doubling of the probability of a tornado in that area, versus the SPC’s earlier outlook.

On its tornado probability map (above), the outlook uses yellow shading to indicate a 10% probability that a tornado will occur within 25 miles of any point during the 24 hours beginning at 8 a.m. ET May 7. In our experience, a 10% probability for this area is quite unusual.

In that area, the normal probability of a tornado on any May 7 is only 0.40%, according to historical data analyzed by the NOAA National Severe Storms Laboratory. A 10% probability is therefore 25 times normal.

A map of Indiana showing an area that has a 10% or greater probability of a significant tornado.
Click the image for a higher-resolution view.

Of additional concern is the outlook’s indication that the same area (shaded in gray on the map above) has 10% or greater probability that any tornado that forms will be capable of damage rated EF-2 or greater on the Enhanced Fujita Scale. Possible EF-2 damage includes snapped or uprooted trees, destroyed mobile homes and roofs torn completely off houses.

The outlook gives most of the remainder of Indiana a 5% tornado probability, except for extreme northwestern Indiana, where the probability is 2%. This means a tornado is possible anywhere in Indiana tomorrow.

A map of Indiana showing probabilities of large hail in different areas.
Click the image for a higher-resolution version.

On its large hail probability map (above), the outlook shades all but extreme northwestern Indiana in yellow, indicating a probability of at least 15% that one inch or larger hail will occur within 25 miles of any point during the same period. The remainder of the state has a 5% large hail probability.

A map of Indiana showing an area that has a 10% or greater probability of 2-inch or larger hail.
Click the image for a higher-resolution view.

The outlook indicates that all but northwestern Indiana (shaded in gray on the map above) has a 10% probability that any hail that falls will be 2 inches or larger.

A map of Indiana showing damaging wind probabilities in different areas.
Click the image for a higher-resolution view.

On its damaging wind probability map (above), the outlook shades all but extreme northwestern Indiana in yellow, indicating a probability of at least 15% that damaging, straight-line winds or gusts of 58 mph or stronger will occur within 25 miles of any point during the same period. The remainder of the state has a 5% damaging wind probability.

It would be wise for people in Indiana — especially #Skywarn storm spotters and anyone who has an outdoor activity planned for Tuesday — to plan for all forms of severe weather and pay closer than usual attention to reliable sources of weather information, including the National Weather Service and professional broadcast meteorologists.

#severeweather #tornado #INwx #largehail #damagingwind

SKYWARN, Weather

Significant tornado outbreak outlook targets Ohio on eve of 50th anniversary of 1974 super outbreak

Leave a comment

Tornados, some significant, also possible in most of Indiana and other states

Probability of a tornado within 25 miles of any point during the 24 hours beginning at 8 a.m. EDT Tuesday, April 2. Black hatched area indicates a 10% or greater probability that any tornado that forms will be “significant,” doing damage of at least EF2 on the enhanced Fujitsu scale. Source: Storm Prediction Center Day 1 Convective Outlook issued at 2 a.m. EDT April 2, 2024. Click the image for a larger, clearer version.

Note: This blog post was updated at 8:23 a.m. Tuesday, April 2, with newer SPC data.

Strong and potentially long-track tornadoes are possible
from Indiana and Ohio southward into the Mid South today, Tuesday, April 2, 2024, according to an outlook the National Weather Service Storm Prediction Center (SPC) issued at 2 a.m. EDT Tuesday, April 2. The highest probability of such weather is centered over Ohio, including Xenia, a city where a tornado killed at least 32 people during the super outbreak of April 3, 1974. The highest risk area also includes the Indian Lake area northwest of Columbus, Ohio, where a March 14, 2024 tornado killed three people.

Probability of a tornado within 25 miles of any point Tuesday, April 2, 2024, according to the Day 2 Convective Outlook that the Storm Prediction Center issued at 2 a.m. EDT Monday, April 2, 2024. Click the image for a larger, clearer version.

A large part of Ohio and parts of southeastern Indiana, northern Kentucky and western West Virginia (shaded red on the map above) have a 15% probability of a tornado within 25 miles of any point, according to the SPC outlook. Because tornados are generally so rare, a 15% probability is unusually high. By comparison, the “normal” probability of a tornado in that part of Ohio on April 2 of any year is no more than 0.40%, according to climatology (weather history) data compiled by the National Severe Storms Laboratory (NSSL). That puts Tuesday’s probability at more than 37 times what’s normal for this time of year!

Even more disconcerting is the outlook’s forecast for what the SPC calls a “significant” tornado, which it defines as a tornado capable of doing damage that garners a rating of at least EF2 on the Enhanced Fujita Scale of tornado damage and associated wind speeds. Tornados that do EF2 or greater damage contain winds of 111 mph to more than 200 mph.

Gray shading indicates a 10% or greater probability that any tornado that forms will be “significant”; capable of doing EF2 or greater damage. Click the image for a larger, clearer version.

If a tornado forms in parts of Ohio, Indiana, Kentucky, Tennessee and other nearby states (shaded in gray on the map above) Tuesday, there’s a 10% or greater probability that tornado will be “significant.” In Ohio, the normal probability of a significant tornado on April 2 of any year is no more than 0.10%, according to NSSL climatology. That puts the probability of a significant tornado at 100 or more times what’s normal for this time of year.

Data from weather balloons “imply fast storm motions and the
possibility for several cyclic tornadic supercells, some of which
may yield strong and long-lived tornadoes,” wrote SPC forecasters Bryan Smith and Elizabeth Leitman in the overnight outlook.

Although the highest probability of tornados is mostly in Ohio, tornados are possible Tuesday in many other states. For example, Fort Wayne, Indiana, where the author of this post resides, has a 5% tornado probability, 25 times the climatology norm.

Tuesday, April 2, 2024 is therefore a day during which it is essential to remain aware of weather forecasts, watches and warnings. Here’s a link to a previous blog post about reliable (and less reliable) ways to remain weather aware.

Spread the word, especially if you know anyone who lives in Ohio!


SKYWARN, Weather

Severe weather is possible Sunday, Aug 6, including a tornado.

Leave a comment
This map from today’s SPC Day 4 Severe Weather Outlook indicates an area (shaded in yellow) that has a 15% probability of severe weather on Sunday, August 6. It includes the entire state of Indiana.

TLDR: The National Weather Service Storm Prediction Center issued an outlook early this morning that indicates a probability of all forms of severe weather throughout Indiana Sunday, including tornadoes; damaging straight-line thunderstorm winds; and large hail. People should pay attention to reliable sources of weather information as Sunday nears, especially people who are planning outdoor activities Sunday afternoon and evening.

How we know this is possible

The Storm Prediction Center (SPC) is a branch of the U.S. National Weather Service (NWS) that’s responsible for providing timely and accurate forecasts and watches for severe thunderstorms and tornadoes over the contiguous United States. Every day, it issues severe weather outlooks for the current day (Day 1) and for days two (tomorrow), three, four, five, six, seven and eight.

Accurately predicting severe weather more than two days in advance is difficult. So, if the SPC indicates a possibility of severe weather in an outlook for three days from now, it’s wise to pay attention.

In the outlook for Sunday that SPC issued this morning (Aug. 3), it indicated a 15% probability of severe weather, including tornados, damaging straight-line thunderstorm winds and large hail, within 25 miles of any point in Indiana as well as parts of neighboring states.

Tornadoes, damaging straight-line winds and large hail are all possible in Indiana Sunday.

Why is 15% a big deal?

As percentages go, 15% looks pretty small. But that’s because severe storms don’t happen all the time. The SPC, in collaboration with another branch of the NWS, the NOAA National Severe Storms Laboratory (NSSL), analyzes historical weather data to determine the normal probability of severe weather on any given date (based on how many times it happened on that date in the past). That analysis indicates that in Indiana, the normal probability of severe weather on any August 6 is 2% to 3% (depending on where in the state, see graphic below).

SPC/NSSL map showing probabilities of severe weather in various parts of the continental United States on any August 6, based on data collected between 1982 and 2011.

That means Sunday’s 15% probability of severe storms is 5 to 7.5 times what’s normal for that date.

What’s most likely, tornadoes or severe thunderstorms?

Day 4 is too far away for SPC to provide probabilities for specific severe weather hazards, like tornados. Nonetheless, the text of today’s Day 4 outlook implies that tornadoes, damaging straight-line winds and large hail are all possible in Indiana Sunday.

In addition. local NWS offices in Indiana issued their own outlooks today that indicate the possibility of severe weather Sunday, especially in the afternoon and evening. These local outlooks also indicate the NWS might need reports from trained, volunteer storm spotters Sunday.

Tomorrow, SPC will issue a Day 3 outlook for Sunday that will provide a categorical risk level from one to five (five being the greatest risk) and possibly modify the target area based on the latest available weather data.

Saturday, SPC will issue a Day 2 outlook for Sunday that will provide individual probabilities of a tornado, damaging straight-line thunderstorm winds (58 mph or stronger), and large hail (one inch or larger). By then, we’ll have a much better idea of what parts of the state have the highest risk and which hazards are most likely.

What should you do now?

No matter who you are, if you’ll be in Indiana Sunday afternoon and evening, and especially if you plan to be involved in an outdoor activity, pay close attention to a trusted source of weather information as Sunday approaches, such as your local NWS office or professional broadcast meteorologists. If you don’t have a weather alert radio in your home, this would be a good time to buy one.

If you’re a trained Skywarn storm spotter like me, prepare for possible activation Sunday, including charging all your battery-powered devices and reviewing what to look for, what to report, and how to report it. The NWS will likely need your eyewitness reports so they can issue the best warnings and keep people safe.

SKYWARN, Weather

Tornado strikes NW Allen County July 29

Leave a comment
Path of a tornado that touched down just west of the Eel River Golf Course south of Churubusco and tracked rapidly east southeast, crossing US 33 before dissipating in a corn field west of Chase Road. NWS image.

The National Weather Service Northern Indiana weather forecast office (IWX) announced August 2 that it found evidence that a tornado did damage in eastern Whitley County and northwestern Allen County, Indiana at approximately 2:30 a.m. July 29.

“But wait,” you might say, “I never heard about a tornado warning for Allen County that day!” That’s because IWX didn’t issue a tornado warning for this storm. At the time of the tornado, however, a severe thunderstorm warning was in effect that included the words, “tornado possible.”

Most severe thunderstorm warnings do not automatically create alerts on your cell phone.

It’s not unusual for the kind of storm we had Saturday morning (a bowing “squall line”) to spawn weak tornados that appear and disappear before the National Weather Service can issue a warning. That’s why, when they warn us of a severe thunderstorm that could contain such tornados, they mention that a tornado is possible.

Weather radar loop slowing the bowing squall line that moved across Indiana early July 29.

It’s also one reason that it’s so important to know about and react appropriately to severe thunderstorm warnings, including those the National Weather Service issues in the middle of the night, when you’re sleeping. But that requires extra effort on your part, because most severe thunderstorm warnings do not automatically create alerts on your cell phone.

If you’ve ever been someplace covered by a tornado warning, you probably received a Wireless Emergency Alert (WEA) on your phone, even if you never installed a weather app. That’s because all modern smartphones come with WEAs enabled and all tornado warnings prompt WEAs.

The only severe thunderstorm warnings that trigger WEAs, however, are those in which the National Weather Service includes a “destructive” damage threat “tag.” They do that for storms that have either hail that’s at least 2.75 inches in diameter (baseball-sized) and/or 80 mph straight-line thunderstorm winds. According to Saturday morning’s severe thunderstorm warning, meteorologists expected winds of up to 60 mph and no large hail. That warning therefore did not trigger a WEA.

So, how can you know if a storm like Saturday’s is headed toward your home in the middle of the night, while you’re asleep? I know of two really good ways:

  1. Buy a weather alert radio and keep it near enough to your bedroom to wake you.
  2. Install a weather alert app, like Storm Shield, and configure it to alert you to severe thunderstorm warnings.

When the NWS issues a severe thunderstorm warning for your location, the best way to be safe is to do the same thing you’d do in a tornado warning. Move to the most interior room on the lowest level of your house. This will provide the best protection from a brief tornado, like the one that touched down July 29 and from straight-line thunderstorm winds dropping a tree limb on your house, which is what killed a woman in Ohio City, Ohio July 20.

Weather

How much snow would a blizzard bring?

3 Comments
Blizzard conditions along a highway. South Dakota Highway Patrol photo, 2020.

National Weather Service meteorologists from the Northern Indiana office and elsewhere have used the “B word” when writing about the winter storm that’s forecast for Indiana later this week.

For example, a winter storm watch that the Northern Indiana office issued today includes the phrase, “blizzard conditions possible.”

When I was a kid, depictions of blizzards in movies and TV dramas led me to think of a blizzard as a very bad, very dangerous storm that drops huge amounts of snow.

It wasn’t until much later that I learned that the meteorological definition of “blizzard” has nothing to do with accumulation!

What really defines a blizzard is how strong the wind is and how far you can see through the snow and blowing snow. The National Weather Service website defines “blizzard” as “blowing and/or falling snow with winds of at least 35 mph, reducing visibilities to a quarter of a mile or less for at least three hours.”

This means that if the wind is strong enough and the forward visibility is low enough, you can have blizzard conditions without large accumulations!

Travel in northern Indiana could be extremely dangerous Friday, no matter how much snow falls, because strong wind could cause white-out conditions. Making the situation even more dangerous will be extreme cold, which would be especially bad for anyone who slides off a road and gets stranded in a ditch.

It’s wise, therefore, not to focus too much on accumulation forecasts with this storm. The wind, visibility and cold could be dangerous even in areas where accumulation is relatively light.

Weather

Here’s why real meteorologists don’t yet know how bad the coming winter storm will be

1 Comment

A winter storm is coming to Indiana and will likely impact travel Thursday night and Friday, December 22 and 23.

Some areas could get a lot of snow. Some could get mostly rain.

As of this morning, the expert meteorologists at the National Weather Service’s Northern Indiana Office can’t forecast where the heaviest snow will fall.

The biggest reason is that meteorological science isn’t capable yet of forecasting the exact track of a low pressure system four days in advance.

I’m not a meteorologist, but I’ve spent enough time collaborating with meteorologists to develop a fair understanding of their work. So, I’ll try to explain here what I know about the coming storm, based on what the pros have published.

First, it helps to know how low pressure systems affect winter weather. Typically, the heaviest snow falls to the north and northwest of a low pressure system. Areas to the east and northeast usually get mostly rain. Areas to the southeast can get clear skies with little or no precipitation.

The path a low pressure system takes therefore has a major impact on where the biggest winter storm impacts will occur.

The main way meteorologists predict a system’s path is by monitoring the output of special computer programs known as numerical weather prediction models. These programs run on supercomputers, because they ingest massive amounts of weather observation data and apply complex equations in their attempts to create reliable, mathematical simulations of the atmosphere. Several such programs exist, all written differently. It’s not unusual for the various models to produce different solutions, which typically come out every 12 hours.

Meteorologist Megan Dodson at the Northern Indiana NWS office wrote in an Area Forecast Discussion this morning that they’re watching the outputs of at least four different models. They’re paying attention to how much consensus exists between the solutions of the various models and how consistent each model’s output is with previous output from the same model.

As of this morning’s forecast discussion, these models indicated that the low pressure system would move from the southwest to the northeast and that the path it follows would be farther west than previous model runs indicated. The image below, published by the Indianapolis NWS office, shows three possible paths for the system. One model, known as the Global Forecast System (GFS), is an outlier, forecasting the most westward path. If it’s right, and the center of the low stays west of Indiana, the Hoosier state won’t get much snow. Other models forecast more easterly paths.

Graphic published by NWS Indianaolis showing possible tracks of a low pressure system associated with a forecast winter storm

All the models could still be wrong!

Numerical weather prediction is not perfect, but the closer the low pressure system gets to Indiana, the more the models will align and the better the forecasts will get.

As I write this, the system is still over the Pacific Ocean, so it should be understandable that it’s too early for the models to accurately predict how it will track over the Midwest.

For now, it’s important to understand that a winter storm will very likely occur somewhere, but as much as you’d like to know exactly where the most snow will fall (and where the most travel impacts will be), it’s just too early to know.

That said, because it’s also too early to rule out big impacts in any part of northern Indiana, it’s wise to prepare for such impacts. For example, you might shop for Christmas dinner ingredients a day earlier than you originally planned, just in case.

It’s also important to realize that some people who are not meteorologists post official-looking but unscientific forecasts on social media. Often, they choose the single model output that looks the most dramatic (even though it’s an outlier), rather than create legitimate forecasts based on a full understanding of model limitations and model consensus. Often, the main goal of such posts is to create bigger audiences for advertisements. Keep that in mind the next time you see a dramatic snow forecast for any time that’s more than a few days away.

SKYWARN, Weather

High probability of very severe weather in Indiana today

Leave a comment
Probabilities of damaging, straight-line winds or gusts.

Damaging, straight-line thunderstorm winds — the kind that can knock down whole trees and cause widespread power outages and road blockages — are likely in Indiana this afternoon and evening, especially in extreme southwestern counties (shaded purple in the map above), according to a convective outlook that the National Weather Service (NWS) Storm Prediction Center issued at 9 a.m. ET today.

The 45% probability indicated on the map above compares to “normal” or “average” probability for this time of year of only 1%, acccording to climatology (weather history) data from the National Severe Storms Laboratory.

And in a large part of southern Indiana (shaded gray on the map below), any severe thundertorms that form could create wind gusts of 75 mph or stronger. That’s the same as a category one hurricane. The probability of that happening is 10 percent, or approximately 100 times the climatology norm of 0.1%

Probability of gusts of 75 mph or stronger.

Tornadoes are also possible throughout Indiana and once again, the greatest risk is in the southwest (shaded yellow on the map below), where the probability is 10%, or about 25 times the climatology norm. The 5% probability in the rest of the state is about 12.5 times the norm for this time of year. So even though 10 and five are small numbers, they’re important in this context.

Probability of a tornado.

Any tornadoes that form in southwestern Indiana (shaded gray on the map below) have a 10% probability of doing damage rated EF-2 or higher on the enhanced Fujitsu scale. That’s about 50 times the climatology norm.

Probability of a significant tornado doing damange of EF-2 or greater.

The entire state also has a risk of one-inch or larger hail, but as the map below indicates, the hail risk is lower than the straight-line wind risk.

Probability of one-inch or larger hail.

It’s important for anyone in Indiana to have multiple ways to receive severe thunderstorm and tornado warnings today. Unfortunately, the Indianapolis NWS office reported this morning that three NOAA Weather Radio transmitters in southern Indiana were inoperative.

NWS Indianapolis tweet about inopertive weather radio transmitters

Update: The Indianapolis NWS office reported at 11:44 a.m. ET that all three transmitters had returned to service.

That makes multiple alerting methods even more important. People in that area shold probably keep a TV on, turned up, and tuned to a local station (i.e., not ESPN or Netflix!). Another idea is to install the free FEMA app on smartphones.

If your phone and other rechargeable devices are not fully charged, start charging them now.

If you’re a volunteer Skywarn storm spotter, prepare for activation this afternoon or evening.

Severe weather, ham radio & anything else I feel like writing about