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It's not too often that I get surprised like I did Tuesday (thank GOD)! Outside of my far southern counties, way down around Ft. Madison and Keokuk, I expected a dry day. Instead, rain fell in just about all of my region with some spots picking up 4 inches plus! Needless to say, I'm eating humble pie which tastes like crap but is certainly effective when it comes to staying grounded. Essentially I was rode hard and put away wet...

So how did this happen you ask? Well, I wanted answers to that question myself so I went back in time to when I created my post Monday night. My routine is to always wait for the 0Z model runs which come down between 10 PM and 2:00 AM so I can have fresh "reliable" data for those reading it later that night or early the following morning. I wanted to make sure there wasn't something glaring in that data that I missed in my analysis.

With that in mind I called up the 0Z runs of the EURO, GFS, and 12K NAM which is what I used to formulate my opinions. They all depicted an MCS (mesoscale convective system) but its rains were shown well west and south, perhaps just grazing my southernmost counties in SE Iowa and WC Illinois. Since the event was less than 12 hours away it appeared pretty cut and dry that 95% of my area would remain dry. See below.


The 12K NAM

Well, instead of quiet rain free radar, the Doppler looked like this at 5:00 PM with flash flood warnings in effect for parts of the Quad Cities and surrounding counties to the southeast. Compare that to what was indicated by the modeling above.

Now if you follow this page, you know that in recent weeks I have made numerous remarks about how mesoscale details can alter a forecast, especially beyond 24 hours. In this case, we didn't even get beyond 12 hours when what's known as an MCV formed. An MCV is a mid-level low pressure center that develops within the stratiform region of a mesoscale convective system (MSC) as it releases latent heat over a period of hours. The low pressure develops a circulation that ranges in diameter from (30 to 125 miles). An MCV can persist and sustain precipitation for 12 hours or more after its parent MCS has dissipated.

Anyway, if you are still with me, the MCS alone would likely have missed my region as models suggested. However, the energy associated with the MCS created the MCV which (was not) anticipated. The creation of the mid level vortex is where everything went haywire. Not only did it bring rain but it altered the temperatures which ended up substantially cooler than anticipated.

Here's some of the rain totals from the area that just 12 hours earlier was expected to be dry. Amounts in the various shades of green range from 1/2 inch to 2 inches. The yellows and pinks go from 2 to as much as 6 inches. Much of it came in a very short period of time.

Just for kicks, here are the QPF (quantitative precipitation forecasts) from Monday night which I based my post on for Tuesday. You can compare the model output below to what actually happened above.


The 0Z GFS

The 0Z 12K NAM

Dang it, that's a terrible bust. The big takeaway is that the models performed poorly and so did I as neither of us visualized the MCV development. I would not say I mailed it in last night as I really wanted to make sure Tuesday was going to stay dry and I presented my case accordingly . However, in retrospect I wonder if I would have dug a little deeper if would have seen the potential. One thing I did notice today is that the next model run, 6 hours later than I used was onto the trend but by then I was sound asleep around 4:00 AM. That's one of the limitations of what I can do. During the week I'm the only one driving forecasts 24 hours a day. At some point I need to sleep and yes, I do have family to attend to. I give it my best but in cases like this, it wasn't good enough. I apologize for letting this one get through the cracks! Things like this really bug me but hopefully you can see I wasn't just throwing darts.

I was once told you are as good as your last forecast. As such, all I can do now is put it behind me, get the next one right, and hope it doesn't happen again for a good long time. The silver lining is that some places that needed a good rain got one, especially near and south of I-80.

So, moving forward we look to be back in the good graces of mother nature Wednesday and Thursday as skies clear and the MVC moves away and dissipates. Both Wednesday and Thursday mostly sunny skies and pleasant temperatures will be with us. Highs will be in the upper 70s to low 80s with very low humidity.

Really the next big challenge is what to do with the rain potential late Thursday night into Friday night. Yesterday the GFS was showing a healthy rain and the EURO was not with just showers. Now the models have flipped showing the opposite scenario. That certainly leads to low confidence and it may take another 24 hours before this all gets sorted out. My arguments against widespread moderate rains is the amount of moisture return and forcing. Those are in question and without them in tandem it will be hard to accomplish. At any rate, here's what the EURO and GFS are indicating for rain from this system.



Well, I've had more than enough for one day. The sun will come up tomorrow and I'll be there to embrace it. Let's all make it a good one. Roll weather....TS


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