Chinook

The SPC web page has max/min/average climatology for basic upper air observed values, like 700mb dew point. The extremes at DTX of 700mb dew points are -45C and even lower for several days of the month of April.

Desert, you say? how about 2% relative humidity aloft, measured in Michigan. It's like 2% milk. 700mb dew points should still be -20C to -30C in Michigan right now.

Snowing at APA (Centennial Airport) and raining in the rest of Denver

These are above the July average temps for some or all of the northern Michigan region. Alpena was 35 deg F above average yesterday, for the high of the day. The 850mb temperature was up to 15 deg C, and as you can see, the surface temperature was an even 30 deg C, I guess that's perfect mixing, if you assume 10 deg C/km and give 1500 meters from the 850mb level to the ground, both of which are not exact.

An 2-d cross section across Colorado and Kansas. The development of the nighttime low-level jet goes from the 20's knots range (3-hour forecast, not shown), to 34 knots (first picture) to 46-48 knots (second picture) tonight. There are not thunderstorms expected, so this is showing that the low-level jet is a common feature, whether the moisture is there or not. It has this way of speeding up to the east of the Rockies that's probably unlike a lot of other places in the world. GFS 6-hr forecast GFS 9-hour forecast normal view

It took me perhaps a very long time to figure out that the degree of 0-6 km shear (and layers above 0-6km) directly related to the amount of stretching out of the FFD and also the extent to which the anvil or cirrus material is carried away from the storm. And along with that, the storms with greater 0-3km storm relative helicity but less impressive 0-6km shear, such as 30 kt or 35 kt, turned out to be high precip. as the higher level winds did not remove material. I'm saying this because sometimes you just have to do something for years to learn it. Or you could have "Convective Chronicles" say it in a pretty easy way to understand.

I pulled up the archived Level-3 radar data a couple of days ago, so that's what you see here. Somehow, my vast amount of saved data didn't contain this, although I remember looking at this radar data as it happened. It probably because I had some data lost when I had two laptop crashes between 2013-2015, but thankfully a lot of my data is backed up in various formats (like CDROMS from the old days).

The SPC research page only says EF-4. I wonder why that is wrong. It's not like it happened yesterday. Other information that I didn't post. I discovered that the supercell must have started close to the stationary front and tracked to the cool side of it. The cell must have been using the most unstable layer (MUCAPE) to power up the huge updrafts. As you can see, the mesoanalysis surface-based CAPE was close to zero with the colder air, and apparently this didn't stop the system from creating a huge tornado.

It was up to 93 at the lower elevations of South Dakota yesterday, up to 80 degrees at Cheyenne (6100 ft). That would be like a million degrees at sea level. (well, maybe not.)

I've been looking at some various case studies of tornadoes/outbreaks on Youtube. I just took a quick search of Youtube and also the internet in general, and not a whole lot has been said about the devastating Mayflower-Vilonia tornado (9 years ago). The Mayflower-Vilonia tornado was 41 miles long and started near 0000z and continued for about 1 hour. It was the only tornado in Arkansas on April 27, 2014. Storm reports and tornadoes were widely spread out within the Moderate risk segment in Arkansas and Missouri. (note: HIGH RISK issued at 20z in Arkansas) On April 28, there were dozens of tornadoes in that day's Moderate risk segment. back to April 27th: There was CAPE up to 3000 J/kg in southern Arkansas with a stationary front near Little Rock. With the easterly winds north of Little Rock, 0-3km SRH maxed out at a large value of 600 m2/s2. (Also supported by Little Rock special sounding at 21z, 612 m2/s2)

First day in the upper 60's without some sort of crazy wind machine, chance for rain, that sort of thing.

Here is an approximate damage path of the March 31st EF4 tornado in Iowa, as per the information shown. I'm not sure how close to the town of Keota the EF4 level damage was.

My area has been fortunate enough to have two days of sunshine. Hmmm. That makes me think of 2024, when an eclipse will come through the center of the US. I am thinking of driving to Texas because it's climatologically cloudy here.

a bit of tornado trivia

The models have 77-83 degrees this week.

Here's the stats for the 3/31 from Wikipedia. I consider this to be somewhat of a super-outbreak with now over 100 tornadoes confirmed

Unfiltered storm reports on three previous days. Up to 161/990 preliminary unfiltered reports on March 31st.

Now there are have peak winds gusts of 47mph at Defiance without thunderstorms

The radar is kind of a mess, with only 4 severe warnings in the country right now. I'm not used to temp of 77 with dew of 63. It's like insta-summer. I'm used to getting the first few 70 degree temps out West, not too long after snow, with a dew point of 20 and a view of the snowy mountains. The SPC really kind of busted with the Arkansas area yesterday, you know, like 100% bust when you look at this map.

Almost baseball size hail north of the warm front near I-80. That's pretty nasty considering the storm doesn't even seem that big, and the surface based CAPE is 0. VIL and reflectivity maxed out near Princeton, so that must be the region where the large hail developed.

A little morning-time rear flank downdraft

There is 1.5"-2.5" in Fort Collins and Loveland, some snow in Denver. A massive section of Wyoming and the Dakotas have a blizzard warning today.

I don't think the CAMs have a lot of storms, if you exclude the FV3 monster storm near Chicago. (seriously, that's like a 10mile wide updraft helicity track. I mean, it could represent a realistic tornado threat that's not a super monster.)

Maybe this is just a case where the 12z CAM models see a cap of some strength. Then, none of the CAM models have much convection at 00z-04z tomorrow night. The SPC is essentially saying they're just really wrong.