3-19-2020

Apr 4, 2010
75
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Bruning Nebraska
So I know this is a month away. But I was looking at the 00z CFS run. The 19th of march shows a 998MB low in western ks. With dew points streaming from the 50s from the Dakotas to the mid 60s in texas. Temps from the 60s-70s in across the region. Surface base cape raging from the 500s from Nebraska to 1399 in texas (ik thats not much but you dont need alot). 200MB winds from the SW at 100 knots, 300MB from the SW at 90 knots, 500MB SSW at 41 knots, and 850MB from the south at 32 knots. Now i am posting this cause I want to start making forecast. Now say we had this like 3 days out would anyone chase it?
 

Dan Robinson

Staff member
Jan 14, 2011
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The problem with any model forecast beyond 7-10 days is that there will almost always be a potentially chaseworthy system showing up at some point during that range, particularly as we move farther into spring. The issue with say a big western trough showing up is that even if you do end up getting that configuration, there are so many other factors that play into whether a day will be chaseable - moisture return, cloud cover, wave timing, etc. Those factors you don't typically have a good handle on even 3 or 4 days out, much less 7 days or more.

Of course a big western trough/eastern ridge will always be on chasers' radar, but until the details start becoming clearer within 3-5 day range - with good model agreement and consistency, that is - only then can you say with any confidence that chasers would be interested. I don't even get that excited at a trough at 10-15 days because most of the time, it isn't there on the next model run.
 

Jeff Duda

Resident meteorological expert
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Oct 7, 2008
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So I know this is a month away. But I was looking at the 00z CFS run. The 19th of march shows a 998MB low in western ks. With dew points streaming from the 50s from the Dakotas to the mid 60s in texas. Temps from the 60s-70s in across the region. Surface base cape raging from the 500s from Nebraska to 1399 in texas (ik thats not much but you dont need alot). 200MB winds from the SW at 100 knots, 300MB from the SW at 90 knots, 500MB SSW at 41 knots, and 850MB from the south at 32 knots. Now i am posting this cause I want to start making forecast. Now say we had this like 3 days out would anyone chase it?
I'm guessing you are not aware of this, but there is essentially no point in taking any NWP forecast that is more than about 10-12 days old as having any serious reliability. As the atmosphere is a chaotic nonlinear dynamical system, predictability on the synoptic scale is pretty much completely lost beyond that 10-12-day time frame almost regardless of modeling system (ECMWF, GFS, CFS, or whatever). Therefore, there is no reason to start a discussion for this case at this time.

For proof of why, I recommend you start religiously following updated runs of the CFS for this particular valid time as the event draws closer. You will notice the forecast for this event will change wildly from one cycle to another. Once this period of time is within 10-12 days, you'll finally start to notice some convergence from this model as to what it thinks is predictable for this valid time. However, it will likely not resemble what you currently see from it.