Joe’s Weather Blog: Math: Sun + humidity + … = rain + storms (SUN-5/22)

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5 years ago later this afternoon Joplin, MO was devastated by an EF5 tornado packing winds of over 200+ mph. The town still hasn’t recovered. It was on the ground for over 22 miles and at times was 1 mile across. It killed over 155 people and injured well over 1000 people. Folks there are thinking back to that day today especially…and we continue to wish them the best in their recovery.

Meanwhile as that is in our minds…today’s weather, there and through the KC area is delightful. Sunshine and warming temperatures. Highs today should be around 80° with increasing south winds and slowly increasing dew point levels.


Tonight: Fair skies>increasing clouds towards daybreak. Lows tonight will be closer to 60°

Monday: Variable clouds with showers moving through the area. There may be some rumbles of thunder as well. The higher rain chances appear later in the morning into the afternoon. Rain amounts may not be too high though…odds favor under 1/2″ it appears unless there is a bit more convection to increase those totals. Highs should be closer to 75° as temperatures may fluctuate from the 70s to the 60s to the 70s with the rain in the region.

Tuesday: Depending on the evolution of Monday’s rain (a theme for most of the week) rain/storm chances may increase again during the early AM through lunch hour period before drier weather moves in during the afternoon. Highs should be well into the 70s.


I thought today we’d start the blog with a quick look back at the Joplin tornado. As I mentioned at the top of the blog…it was an EF5 tornado, the highest ranking we give out to damaging tornadoes.

It started, as they usually do…as a smaller tornado…but because it quickly intensified and did so so close to the city, things got complicated fast for the folks down there.


Through the city limits it was an EF4-5 tornado.




Tornado ratings of the Joplin tornado

It touched down around 5:34 and within 4 minutes was tearing through the city limits.

Tornado warnings were in effect for the city…however the system didn’t work as well as hoped for. Between a previous tornado warning that was issued earlier for areas slightly north of Joplin and other complications including a population base that had suffered years of “tornado fatigue” because of being “over-warned” by tornado warnings that never materialized into a tornado…the death and injury toll was significantly high.

The NWS wrote up a fascinating report about the actions taken by them and the citizens of Joplin as the events unfolded. It’s worthy of a read for you weather geeks out there. There were actions taken from this report that are being used today.


Today’s satellite picture is a tranquil one for us in the KC metro area…


You can clearly see the moisture streaming northwards today as the dew points are increasing through the Plains states.

At the 11AM hour…you can see the 60-65° dew points becoming more and more common through the Plains states.



11 AM dew points

We’re on the eastern edge of the higher dew points and eventually this will work eastwards and things are going to get pretty darn “thick” around these parts as our dew points should pop into the 65-70° range as the work week moves along.

So a big check mark on the surface moisture in the region.

The moisture above the surface also gets a check mark too. We measure this by looking at the “PW” values or Precipitable Water data.

Here is the forecast for later Tuesday…notice the contours through the Plains and Midwest. Values over 1″ are decent…over 1.5″ are high…and around or over 2″ is VERY high. We sort of are in the area of 1-1.5″ for the most part.


7PM Tuesday PW values

So the moisture from the surface (dew points) upwards (PW) is very healthy shall we say. This tells me that as whatever moves through the region that there will be a lot of moisture for it to work with…and this will result in locally heavy rains depending on the set-up each day. The location of the heaviest rains will vary with the location of the most concentrated thunderstorm activity and this will likely vary from day to day.

Now the warmth factor. Depending on the amount of residual cloud cover from day to day…temperatures this week are likely to be well into the 80s for a day or two or three. So there will be plenty of surface heat to get the lower part of the atmosphere in motion…instability. This is reflected by looking at surface based CAPE values. We’ve talked about CAPE values before as a way of measuring the instability in the atmosphere. Higher values mean more potential instability for storms to tap into should they form. CAPE values this week will be rather significant towards the latter part of the week. Monday and Tuesday may yield more cloud cover reducing the amount of instability generated by the warm surface temperatures.

There is also a matter of wind shear which really won’t get a check mark till later in the week it appears. Wind shear is important as it can be created by changing wind speeds as you go up in altitude as well as changing directions as you go up in altitude. Wind shear values won’t be too high for a few more days…so widespread severe storms may be tough to come by for awhile this week…perhaps till later in the week.

The reason why the wind shear will be increasing later in the week is that’s when we expect a stronger wave to lift out of the SW part of the country and move through the Plains states. Here is a look at the flow pattern at about 18,000 feet or so for later Thursday. See the dip in Rockies…near CO…that is a rather stout wave that is going to come across the Plains later THU into FRI…it should create some big thunderstorms. We may end up NOT getting the worst of the storms with this…it’s still too early to say for sure…but we will get some significant thunderstorm activity with it…perhaps the timing is more towards the overnight hours.


GFS forecast for THU 7PM. NOTE the “dip” in eastern CO…this is going to create a LOT of lift out through the Plains states THU PM and night

How all this plays out obviously to still to be figured out…but I do have some takeaways.

  1. Monday’s rain may come a bit later rather than earlier in the day. Odds favor the PM hours for most of the rain that we see. Some may not get much from this initial batch.
  2. Tuesday’s chances may be more tied to the low-level jetstream that is forecast to develop. Should there be a remnant boundary left over SW of KC from some rain cooled air via Monday PMs rain…we could see additional storms TUE AM
  3. I don’t think it’s going to rain for 5-6 days straight. I’m not sure WED and THU may have much rain. Still worthy of holding onto the chance right now…because as I mentioned…what happens one day will affect the next day will potentially affect the following day.
  4. VERY muggy weather (think summer humidity) with our 1st heat index values are likely WED>THU
  5. That wave later THU out west may create some nasty severe weather in the central and western Plains. Typically when this happens we get a line of storms/heavy rainfall locally in the KC region during the overnight hours. Again too early to say with a lot of confidence that this is how it will play out…but that is possible
  6. Some areas will get a lot of rain obviously. Not confident in the exact locations though…odds seem to favor areas north of the I-44 corridor up towards the I-80 corridor as an initial “region to watch”.

So a lot going on this week and the forecast will change from day to day. Even yours truly who keeps things as consistent as possible from day to day when I’m working…will be forced to adjust on the fly as the events unfold. I’ve given you some decent ideas though what to expect as am opening salvo on a busy weather week in the Plains states.

Speaking of “busy weather”. There weren’t a ton of storms yesterday in the western Plains…but one in particular was the picture perfect supercell thunderstorm that ended up producing several tornadoes. The thing though was it was almost stationary which meant storm chasers didn’t have to drive all over the place to watch it evolve. This allowed them to do timelapses of the storms evolution and the best one I saw was this one.

Just some amazing pictures from this one lone cell out near Leoti, KS

Finally I see encouraging signs about the holiday weekend ahead. I’m not sure if this situation will run it’s course by Saturday or not…so that is a questionable weather day at this point.


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