Update On Wednesday And Thursday’s Severe Weather Threat

As I highlighted in my Sunday blog post, there is a significant threat for severe storms Wednesday, Wednesday night, and early Thursday. Damaging straight-line wind was the main concern per yesterday’s guidance, and it still is the main threat. The tornado threat, though, has come up, but it is still a secondary threat at this time.

Just after 3am on Monday, the Storm Prediction Center placed the Tri-State in a slight to ENHANCED risk for severe storms Wednesday and Wednesday night:


The highest potential for severe storms is focused northwest of Cincinnati.

This morning’s guidance has shifted the main area of severe weather farther north into the Great Lakes. Despite this shift, we are still in a significant threat for severe storms Wednesday and Wednesday night.

In yesterday’s blog, I discussed the derecho parameter. While I am not forecasting a derecho at this time, this parameter gives us an idea of how high the damaging straight-line wind threat is IF storms occur. Here’s what this morning’s NAM model thinks the derecho parameter will be at 2am Thursday morning:


Clearly, these are high values (anything over 5 is very significant, really) over the Great Lakes and Ohio Valley. Here’s what this morning’s GFS model thinks for the same time:


While values are not as high, they are still high.

While computer guidance suggests the complex of storms may stay focused to our north, the Weather Prediction Center suggests there will be warm front (the leading edge of warmer air bisecting the Tri-State) Wednesday night:


The air mass lifting in from the southwest will be warm, humid, and unstable, and the front will help provide shear (the change in the speed and direction of the wind). All of these elements combined elevate the threat for tornadoes and damaging-straight wind locally (despite a higher threat closer to Chicago).

The Significant Tornado Parameter tells us where there is a elevated risk for tornadoes IF storms can form. Number greater than 1 are usually supportive of at least the potential for tornadoes. Here’s what Monday morning’s NAM model has the significant tornado threat at for 8pm Wednesday night:


This is elevated. Let’s see what Monday morning’s GFS model has for the same time:


This is also elevated. Notice that this does not guarantee tornadoes, but it does show us the magnitude of the tornado threat.

It is also important to note that model guidance is NOT is not a forecast. A meteorologist must review other guidance to make a forecast, and here is what I have come up with for now regarding late Wednesday and early Thursday’s severe weather threat:


This forecast may change as model guidance changes and as we near the event. Know that the damaging straight-line wind threat and tornado threat are both in play for late Wednesday and Thursday. I’ll update this blog as needed.

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What We Know And Don’t Know About Wednesday Or Thursday’s Severe Weather Threat

In the Ohio Valley, it is rare to be put in a severe weather risk area by the Storm Prediction Center more than 3 days out. This week will feature one of those rare occasions.

The Storm Prediction has put the Tri-State in the 15% severe storm risk for Thursday. The 15 percent risk means SPC feels there is a 15% probability of a tornado, severe hail, or severe wind event occuring within 25 miles of a point:


This is – essentially – a “slight” risk for severe storms on Thursday. The 30% area would be the equivalent of an “enhanced” risk. “Marginal,” “moderate,” and “high” risk equivalents are not issued on forecast days 4 through 8.

The takeaway here is that the Storm Prediction Center feels there is a significant severe weather threat in the Great Lakes and Ohio Valley Wednesday.

Or will it be Thursday? Models disagree on the timing of this mid-week storm threat.

There is already a buzz on social media about a complex of storms racing through the Midwest and Ohio Valley Wednesday. Some are predicting a “derecho” (a long-lived complex of storms that causes wind damage over a large area), which predicting at this range is not worth our time and ridiculous. The definition of a derecho is loose. The SPC believes a derecho must go 250 miles and contain separated 75mph wind gusts. Others disagree that a derecho needs to fulfill this requirements.

Regardless, let’s investigate this severe threat using the derecho parameter, which suggests where derechoes may grow or evolve IF storms are able to occur. The higher the derecho parameter, the better the support for them. Here’s what Sunday morning’s NAM model suggests the derecho parameter will be at 2pm Wednesday:


Clearly, there is a significant risk for storms with damaging wind to our west Wednesday afternoon if you believe this model. Let’s compare it to Sunday’s morning’s GFS model:


The GFS is not as impressed with the threat compared to the NAM, especially for Indiana. It is a model model with a different engine, but it is still showing a significant risk for storms with damaging straight-line wind. The GFS model actually holds the better threat off until Thursday:


The NAM model produces a future radar product. Here’s what Sunday’s morning’s NAM model suggests the radar might look like Wednesday morning:


…and here’s what it suggests the radar will look like 12 hours later:


Even history suggests we need to watch for a damaging straight-line wind threat. The Storm Prediction Center’s database suggests the historical odds of seeing severe weather on June 22 is focused over the Tri-State, central Plains, and Carolinas:


When severe weather occurs in the Ohio Valley on June 22nd, it is very likely to be a damaging straight-line wind report versus a tornado or large hail report:


It is apparently that we need to monitor the damaging straight-line wind threat later this week, although tornadoes and large hail are possible with any storms that sweeps through the Ohio Valley. Our confidence, however, is muted when we see discrepancies in model guidance. The last two runs of the European forecast model (ECMWF) suggest the damaging straight-line wind threat will peak late Wednesday night or early Thursday. It is the “middle of the pack” right now.

Stay tuned. Wednesday and Thursday are days to be prepared for strong and severe storms.


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A Breakdown Of Today’s Severe Weather Potential

Morning showers and storms have stabilized the low-levels of the atmosphere and have prevented temperatures from rising significantly. As of 11am, most in the Tri-State are in the 70s:


Sunshine is, however, returning to the Tri-State per the 10:45am visible satellite image:


Note a boundary (in the form of clouds) from southern Indiana back close to Dayton. The Ohio Valley radar image as of 11:15am shows showers and storms moving east and southeast of Cincinnati:


While the boundary now from southern Indiana into west-central Ohio is moving southeast and will trigger isolated to scattered storms early this afternoon, the main axis of instability is in northwestern Indiana and is dropping southeast. This secondary front will be the one that triggers storms later this afternoon and early this evening.

The Storm Prediction Center has the entire Tri-State in a slight risk for severe storms through this evening:


This is mainly for the potential of damaging straight-line wind. Secondary threats include large hail and localized flooding, especially with dewpoints in the upper 60s and lower 70s as of 11am. Here’s a breakdown of severe weather threats through this evening:


The most likely time for severe weather today centers between 3pm and 9pm, especially between 5pm and 8pm.

Clusters of rain and storms will develop to our northwest later today, gradually coalescing into a line as it moves southeast. The afternoon forecast calls for showers and storms to redevelop this afternoon. Highs today will be in the mid to upper 80s, and it will be steamy:


Showers and storms will diminish and end this evening. Strong and severe storms will be favored early:


Be alert, friends!

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Was It A Storm That Wasn’t In The Forecast? Nope.

If you were watching Ohio Valley radar yesterday afternoon, you might have noticed radar returns in southern Indiana. Were these showers and storms bubbling up due to temperatures rising through the 70s? Did I bust a forecast?

Despite what you may think, the same device that suggests I blew the forecast also suggests I got it right. Modern radar is a power thing when used to it’s fullest potential.

First, is it realistic to have radar returns in this area? A visible satellite snapshot of the Ohio Valley shows cumulus clouds in southern Indiana at 5:15pm yesterday afternoon:


We need clouds to have showers and storms, so the returns on radar could be precipitation. Notice there are no towering clouds in the area though (unlike in northern Ohio were showers and storms were in progress with higher instability); satellite imagery leads us to believe there was just a sea of shallow cumulus clouds yesterday afternoon in southern Indiana.

Here are the radar returns as viewed by the National Weather Service Doppler radar in Indianapolis late yesterday afternoon. The reflectivity (commonly shown on television or apps) is on the left, and correlation coefficient (showing the relationship between the height and width of objects like raindrops, hail, or debris sampled by radar) at the right. Blue values of correlation coefficient here suggest these returns are particles of different shapes and sizes and likely not raindrops, hailstones, or something related to meteorology:


Radar cross sections show these returns did not extend well into the atmosphere. Here’s the reflectivity cross section from NWS’ Indianapolis’ radar at 5pm ET yesterday:


These returns are relatively close to the ground (below 10,000′). Here’s the correlation coefficient cross section at the same time:


Blue values here suggest these radar returns are likely not raindrops or hailstones. So what could it be?

The radar returns become apparent around 4:40pm in the afternoon. See the green dot in the reflectivity at the left with blue (low) correlation values in the same area at the right:


This is surprisingly close to Camp Atterbury in Indiana. The military is known for dropping chaff to scramble radar and serve as a countermeasure. Low (blue) correlation coefficient values on radar are common with smoke plumes and military chaff. The meteorological environment did not support showers and storms, so military chaff is the most likely bet.

Need some additional evidence? Fast forward to this morning. Here’s the visible satellite snapshot as of 8:45am Wednesday:


Notice no clouds in the sky. There were still no clouds over southern Indiana as of 10:30am ET.

Yet there is something on radar in the same area near Camp Atterbury as of 10:20am ET:


Reflectivity values are high and correlation coefficient values are low in the image attached. It looks like chaff is the culprit here. Remember, we need clouds to have showers and storms, and there were no clouds in the sky when these returns were on radar.

Radar is a powerful tool if you review the data thoroughly. Even as a meteorologist, it’s easy to fall into the trap of seeing radar returns and assuming showers and storms are developing. Radar can sample dirt, bugs, plumes from wildfires, tornado debris and precipitation. Things aren’t always as they seem!


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Historical Perspective On This Morning’s Freeze

A freeze in the second half of May in Cincinnati is rare. While rare, freezes and frosts and do occur in late May.

The official low temperature this morning at the Cincinnati/Northern Kentucky International Airport was 31°. This sets a new record low temperature for May 16th; the previous record for May 16th was 32°, set in 1997. Low temperatures in the low to mid 30s were widespread this morning:


Inside the I-275 loop, temperatures were slightly warmer due to the urban heat island effect (more building/concrete to retain heat):


Notice Okeana dropped to 28°. Two weather stations just north of Lebanon reported low temperatures of 29° and 28°. Several sites reported a low of 30° or 31°.

How rare is a low temperature of 32° in mid or late May in Cincinnati? Here are the latest spring dates in the Queen City with a low temperature of or below 32°:


Notice that today’s low of 31° is the 3rd latest spring freeze date on record (back to 1871).

Frost can occur at various temperatures, but 36° or below is a good threshold to use for frost. Using 36° as a baseline, here are the latest spring frost dates in Cincinnati back to 1871:


Today’s low of 31° ties as the 9th latest spring frost date in the Queen City. A freeze (which we had this morning) implies widespread frost.

I am cautiously optimistic that this morning will be the last freeze and frost of the season. There are no forecast overnight lows in the 30s through this weekend. Additionally, history suggests we’re safe from a freeze or frost once we get into June!

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What You Need To Know About Today’s Severe Weather Threat

The Tri-State is in a slight to enhanced risk for severe storms this afternoon and evening. This is the highest threat for severe storms we’ve had so far in 2016.

The latest Storm Prediction Center outlook has the enhanced risk (the highest risk for severe storms over and southwest of Cincinnati this afternoon and evening; strong and severe storms are (slightly) less likely to the northeast and north of Cincinnati:


I encourage you to focus not on the severe threat category for which you live; instead, know that the threat for severe storms is higher in Cincinnati and points south and southwest of Cincinnati and slightly slower from Middletown to Hillsboro.

Based on radar, satellite, and model trends, it appears the highest threat for severe storms will be highest between 3pm and 10pm today:


What might the radar look like at various times today? One model, the High-Resolution Rapid Refresh, seems to have a decent grasp on rain and storm placement now. Here’s what it suggests the radar will look like at 2pm today:


Notice the round of showers and storms that came through late in the morning exiting the Tri-State completely (to the northeast) by 2pm.

Forecast radar at 5pm shows showers and storms becoming more numerous:


Forecast radar at 8pm shows showers and storms bowing and gradually pushing east of Cincinnati:


By 11pm, the High-Resolution Rapid Refresh model shows storms diminishing and pushing east of I-75:


Be prepared! Some storms may produce damaging straight-line wind and large hail. The strongest storms in the Ohio Valley will be capable of producing flash flooding and tornadoes.

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The Best Gift Tim Hedrick Ever Gave Me

Long before I got a bobblehead, grocery bags with his name on them, worked with him, spoke with him on the phone, or trained to be a meteorologist, Tim Hedrick did something for me that put the pendulum in motion. When you help or speak with someone today, you’ll never know who you’ll inspire over 20 years later.

When I learned of his death, I immediately went looking for photos of or with him. I only found one with him, and I found several of him. A few hours later, I realized I had one memory of him that I have had for over 25 years.

I was at my mother’s house a day later, looking through bookshelves and bins in my old room. I couldn’t find that memory. A few days later, my mother thought I might have it at my home. I went through my bookshelves, and I found it.

The memory of him is from when I was a young child, approximate 5 to 8 years old (I can’t remember exactly). I went to the Blue Ash branch of the Hamilton County Public Library one morning during the summer for a short weather presentation Tim was giving; Tim was just starting a career in Cincinnati. I remember my mother taking me there, but I don’t remember the presentation. Before the presentation, my mother encouraged me to bring something for me to get Tim’s autograph. I brought a book my mother had gotten for me through the Scholastic school catalog (remember those)? Because I was young, it was simple and appropriate for an early grade school student.

After days of searching, I found that book today:


The book is very fragile. The book is intact, but it wouldn’t take much to get pages falling out of the book. Inside of the book’s front cover is a special message:


In an ironic twist as I read these words today, rays of sunlight started pouring from behind the clouds through my window.

As I have mentioned an earlier blog post on April 9, 1999, my love of meteorology was strong as a young child, waned some through grade school (mainly by the amount and other types of school work), and developed again in the wake of the Blue Ash/Montgomery/Symmes Township tornado.

I suppose things end about where they begin. My time with Tim began with sun, had days of turbulence, days of storms, days with bumps, but ended with sunshine. No bobblehead will inspire you to follow a dream, but words of inspiration early in the game seemed to do the trick for me.

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What You Need To Know About Tomorrow’s Severe Weather Threat

There is a risk for severe storms tomorrow. There is uncertainty in the timing and the strength of thunderstorms tomorrow. I’ll provide updates as the timing and threat changes, but this is the plan for now.

The entire Tri-State is in a marginal to slight risk for severe storms Thursday and Thursday night. The slight risk is basically for communities along and west of I-75; this is where the threat is highest:


As usual, the threat for damaging straight-line wind and large hail will be highest. Tornado threat is in play, but it is a secondary threat. Here’s are my thoughts how high each threat is:


Note that the most likely time for strong to severe storms late in the week is 8pm Thursday to 2am Friday.

Computer guidance is of little help with the timing and strength of tomorrow’s storms. For the time being, the NAM model appears to be more accurate. It shows rain and isolated storms developing overnight and early Thursday (Cincinnati is the pink dot):


Rain and isolated storms move east of Cincinnati tomorrow morning and early tomorrow afternoon, and partial clearing is forecast during the second half of the day:


The second round of showers and storms will develop to our west during the afternoon and move east, towards the Tri-State, nearing sunset:


A line of rain and storms will sweep through the Tri-State during the second half of the evening and very early Saturday morning:


Rain and storms will diminish and end well before sunrise on Friday:


The screaming message here is that rain and isolated storms are forecast overnight and early Thursday and a second round of storms is forecast tomorrow night. Be alert for warnings!

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11:20am Weather Update – Including Today’s Severe Threat

Feeling stuffy? The pollen count is high as of 10am this morning…


Breezy and windy days tend to have an elevated pollen count. It will probably be high tomorrow.

It’s a warm windy day in the Tri-State. As of 11am, temperatures are already in the mid 60s:


The wind will be sustained out of the southwest this afternoon between 15 and 30mph. Gusts may be as high as 45mph to 50mph in some Tri-State communities today. A Wind Advisory is in effect through 6pm for the entire Tri-State:


Radar shows a well-defined line of rain and storms approaching from the west:


Rain and storms will increase through mid-afternoon. Rain and storms will decrease early this evening. Here’s one one model thinks the radar will look like at 5pm:


While rain and storms will be moving through the Tri-State, I believe this model is too slow. The threat for strong storms will be decreasing around and after 5pm. Here’s what the same model thinks the radar will look like at 8pm tonight:


With modest instability, temperatures in the 60s, and dewpoints rising into the 50s, the Storm Prediction Center has placed the entire Tri-State in a marginal risk for severe storms through this evening:


Large hail and strong to damaging-straight line wind is the main threat. The tornado and flooding threat are low at this time. Note the most likely time for any strong or severe storms today will be between noon and 5pm:


In summary, this afternoon’s forecast calls for a cloudy sky, rain, and storms with a strong wind out of the southwest:


Rain and storms will diminish this evening as colder, drier air moves into the Ohio Valley from the west:


Stay weather aware through early evening!

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3:30pm Update On Severe Weather Threat

A Tornado WATCH or a Severe Thunderstorm WATCH may be issued for most of northern Kentucky and southwestern Ohio shortly.

Carroll County and all of southeastern Indiana are under a Tornado Watch through 9pm:


Additional watches and warnings may be posted for the Tri-State later this afternoon and this evening. Be alert!

The radar composite as of 3pm shows a bowing line of storms to our west. These storms are moving east at roughly 45mph and are quite capable of producing damaging straight-line wind in excess of 60mph:


Additional round of rain and storms are likely tonight, but the round approaching from the west is likely to be the main event. It will zap a lot of the instability available for storms this evening.

The visible satellite snapshot as of 2:15pm shows breaks in the cloud both ahead of the line of storms around Louisville and also behind it:


Breaks in the clouds will support to an increase in instability and stronger storms. Temperatures have been slow to rise today due to a cloudy sky, but strong southerly flow has pushed temperatures into the mid 60s for most:


There is still plenty of time for the record high today in Cincinnati of 66° set in 1933 to be broken or tied.

The main severe weather threat through tonight continues to be damaging straight-line wind, but tornadoes are also a secondary threat:


Most of the Tri-State is still in an ENHANCED risk for severe storms through tonight, with the highest threat being southwest of Cincinnati:


You are encouraged to have multiple ways of getting warnings and watch information, including from a NOAA weather radio!

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