When I went to bed last night (Saturday, 5/18 after we finished chasing the squall line in south central Kansas), I planned to spend much of the evening writing an Insiders Briefing discussing the process we use to make a chase target choice. With the main risk in Kansas being flooding, I thought it would be in interesting change of pace for those who are really into weather and the site.

But we pulled the plug on chasing Oklahoma about 9pm Sunday. I thought it might be illustrative if I explain our thought process getting to that decision.

Disclaimer up front: I make no judgment of any other chaser or team’s decision to chase or not chase this event. For me and the three people I’d be responsible for in the truck, this just didn’t fit the risk profile.

Strike 1: forecast widespread precipitation in the warm sector ahead of the main event

Here’s a selection of model forecasts for tomorrow. I’ve tried to keep it light with my naming of the image loops because this is a serious situation. The GIFs may not all animate, so I’ve also provided the download link for each.

GFS: If the first round doesn’t get you, hang on there’s another round that may

HRRR: Are we getting a storm outbreak or an acne outbreak this morning?

HRW WRF-ARW: how ow many rounds at the plate does this batter get? Oh, and let’s give Kansas some too in the middle of the night!

 

HRW WRF-NSSL: Round 1, 4pm; round 2, midnight; round 3, 5am

A mess like this means we have to be on the constant lookout for storm interactions, mergers, splits, and the effect they have on the environment. The environment in one 3-5 mile square box may be markedly different from any of the eight boxes surrounding it. For safety sake, that means playing/working further from the expected tornadic storms.

Strike 2: low visibility, very low cloud bases

These images show 1pm forecast temperature and dew point

1pm forecast temp at OKC, 73 degrees give or take

OKC 1pm Dew Point, 73 degrees give or take

What do you get when the temperature and dew point are the same, or within just a couple degrees? Fog, mist, and cloud bases in the hundreds of feet (like 500 feet or less) at these temperatures.

As I heard from someone else “we’re going to be crawling around under these bases looking for the wedges.”

As in, crawling on our hands and knees.

It also means for our own safety we have to play further from the storms.

Strike 3: Traffic, Chaser Convergence, Lack of Options

This is really the one that made the decision for me. Let’s set aside that the models basically rake storms the length of I-44 — one of the most classic setups for major tornadoes in Oklahoma. Let’s set aside that the Oklahoma City metro has its own traffic problems and slowdowns. Now add a couple thousand storm chasers…and those are just the ones who know about storms enough to pass the test to beacon their location on Spotter Network.

So we’re going to have these….

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In these conditions…

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With chaser traffic like this…

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Combine all those things and I evaluate our risk of becoming part of the problem as too high to be acceptable. If I lived in the OKC metro I would be out, but that’s because for me being out in a tornado is a more realistic expectation than staying home. But I live in Wichita, and I’m not going to put myself, those in my vehicle, and others on the roads at risk of getting forced into a place I can’t get out of.

There is a bit of light in the forecast, though

How can I say that when SPC has a HIGH risk posted? Because that high risk currently does not include the Oklahoma City metro. That is not in any way to say that lives in rural Oklahoma are any less valuable than those in the city. It’s an acknowledgement that because of the lesser population density there are fewer people total at risk of having their lives changed today. However, as you’ve seen in the models above, the MODERATE risk area does include both Oklahoma’s metro areas.

Here’s the (very strong) wording from SPC about today’s threat:

An outbreak of strong tornadoes and severe thunderstorms is expected today across parts of the southern and central Plains. In addition, many of the storms will have very large hail and wind damage. The severe threat will be concentrated from west Texas and the Texas Panhandle eastward across Oklahoma, Kansas into western Missouri and western Arkansas.

And the graphics:

SPC Categorical Severe Storm Threat:


Light Green/Yellow: Slight    Brown: Enhanced      Red:  Moderate     Violet:  High

SPC Tornado Probability

 

Probability of any tornado within 25 miles of a point

Green: 2%     Brown (most of Kansas): 5%

10% probability of EF-2 or stronger tornado within 25 miles of a point

White overlay from Texas panhandle to far southern Kansas, covers most of Oklahoma.

Probability of any tornado within 25 miles of a point (shown overlaid by the significant tornado risk area)

Yellow (entire significant area outside the red and violet): 10%        Red: 15%        Violet:  30%

SPC Large Hail Probability

Probability of hail 1″ to 2″ in diameter within 25 miles of a point

Brown: 5%       Yellow: 15%     Red: 30%     Violet: 45%

Bone-color overlay: 10% probability of hail larger than 2″ within 25 miles of a point

I didn’t run a wind image, but it’s just as ominous.

I offer my prayers and well wishes to those who will be impacted by these storms, to the chasers who choose to document this event, and to the emergency responders and recovery workers who will be called to “do what they do” in the upcoming days and weeks.