Happy Father's Day - Chris's Corner 19 June 2022

Large scale pattern starting to look downright cool by August standards later next week with a huge amplification of the trof across the E US...would probably be some 50s around if model trends hold.

Guessing typo, or more accurately, copy/paste error from the writeup from previous storm.

Mathz iz hard.

Kind of fun to read the evolution of the storm that brought the "first inch of snow to st louis" - thread started jan 12 of this year.

I'm still waiting on a 1-1000 year snow event here. Whatever that is it sounds fun.

59* 7 miles west of De Soto. What a beautiful morning.

Models backed off on the ring of fire potential this weekend with stronger low-level ridging in place and seasonable temps but they are starting to look very favorable for another heavy rainfall setup early next week.

UK and EC is further west with placement...00z UK had 6-8" near COU. Of course, this is ~4 days out so that could change. But it shows the potential. Have to say it looks somewhat similar to the setup that produced the historic flooding a few weeks ago. But I wouldn't expect 12"+ amounts just yet, lol

By my count there has been 4 separate 1-in-1000 year flash flood events in the last couple of weeks. The first is St. Louis. The second is Kentucky. The third is Illinois. And the fourth is Death Valley.

Is this unusual? Maybe not.

To answer this question we need to understand what a 1-in-1000 event means exactly. A lot of people think it is a misnomer, but it's actually pretty reasonable jargon. It means that there is a 0.1% of chance of the event each year. Given a reasonably large sample we would expect the ratio of event years to non-event years to be 1-in-1000. There may gaps of 2000 years or only 10 years. But the expectation is still about every 1000 years. The odds of two 1-in-1000 year events occurring in the same year is about 1-in-1,000,000; unlikely, but possible. And the odds of it happening in any randomly selected 2 week period is about 1-in-25,000 (lots of caveats here though).

Now back to the question. To answer it let's assume the events are contained within a boundary that is 25 km * 25 km = 625 km^2. Each 625 km^2 region has a 1-in-25000 chance of experiencing the event in a 2 week period. There is about 9,800,000 km^2 of land area in the United States. Assuming all of that area is of enough interest to observe and report on extreme events that gives us 15,680 unique regions. Based on the Monte Carlo simulation I did that means each 2 week period we expect the odds of at least one of them experiencing the event to be about 47%. And the odds of 4 of them experiencing the event in the same 2 week period is about 0.4%. That means the recurrence interval of 4 separate 1-in-1000 year events occurring within the same 2 week period in the United States is about 1-in-10 years.

This is just a rough approximation. In reality the true recurrence interval of 4 separate 1-in-1000 year events in the same 2 week period is much more difficult to calculate when we consider all of the caveats. But it does provide a first approximation using first principal reasoning.

The point...hearing of 4 separate 1-in-1000 years so close together in 2022 is noteworthy. There's no doubt about that. But it's probably not as exceptional as you might think considering there are so many different regions rolling the dice within the United States.

Some models are shifting the heaviest rain eastward toward the metro. The NBM has been scooting eastward the last couple runs with the rainfall axis.

I think people misinterpret the 1 in a 1000 verbiage. It "sounds" to the masses a lot different than a .1 chance of a rain like that. Even having two in exactly the same area, to me, is not all that far fetched because to me anyway, that's what the pattern is all about. While statistics say the chances of two in the St. Louis area is .01, a persistent weather pattern providing two such extreme rains is not at all unrealistic. I agree having 4 separate events across the conus is noteworthy, but not at all exceptional. It's part of the pattern.

On to weather I would not let our guard down on the early week system for flash flooding. I am becoming increasingly concerned about an eastward trend and would not be surprised to see the potential for at least 2 to 4 inches of rain (haha I almost said snow), expand all the way to MS River. I'm not saying for sure that heavy rains will make it all the way to the river, but obviously I think the odds are such that you want to plan for heavy rain especially if you live in the far western western counties of the metro and points west - I'm speaking of places like Warren, Franklin, Montgomery, Audrain, down to Washington. Seems to me that Springfield, MO had flash flooding in the last event - they are in line for potentially another flash flood this time as well. I hope it stays west, but we do need some light rain here. The 15 inches certainly ran off.

So, preliminary discussion on winter - I see the almanac came out with its annual dooms day scenario...again. Just a bunch of drunk guys gathering in a bar scribbling their outlook on a bar napking I think. I do think what is noteworthy is that the heat and drought is not like 2012 for us as we are closer to the ring of fire all summer long. I also think the erosion of the drought in the plains into the 4 corners area could play a part as well. If these ongoing patterns survive the transition of the seasons, that could impact our winter months in some way. I don't think 2012 is a good analog for the upcoming winter as some on social media have suggested.

So where is the heaviest rain axis setting up now according to the NAM?