May model madness begins!

The calendar finally flips to May on Saturday, so it’s storm chasing month! But another key event on the storm chasing calendar has occurred a day earlier: The long-range GFS model is just now starting to show the opening day of the window for the first of two Virginia Tech storm chase trips, May 16. And as you can see from the posted maps above, two different runs of the GFS today have come up with two wildly different solutions: the 12z at top depicts a northwest jet stream flow through the Plains over the top of a shallow ridge in the Southwest, while the 18z GFS digs a trough into the Southwest.

The 12z scenario would be a familiar pattern for Dave and me, with weak moisture return underneath the cool, dry flow from the northwest. We saw this same pattern for several  days in 2005 … and 2006 … and 2007 … and 2008 … and 2009. In all but 2009, we were able to wait it out until there was at least some modest improvement in storm potential. If this pattern is reality, we would probably drift slowly west until there was a substantial change, and possibly would even delay departure a couple of days to save gas money while the pattern resets.

The 18z scenario would signal enhanced severe storm potential in the central U.S. right out of the gate, with strong south to southwest winds aloft, strong moisture return and a major trigger for storms. If that were to verify, we’d probably leave early that Sunday, get as far west as possible on the first day, and set up for a chase on the second day of our trip.

But really, this is almost pointless right now. The models will flip and flop to various scenarios over the next 2 weeks. If they begin to hit on one particular pattern in multiple successive runs, we pay attention.

So don’t bother looking at every run of the GFS between now and departure time.

Meanwhile, Dave and I will be doing exactly that!

— Kevin Myatt


16 responses to “May model madness begins!

  1. hokiestormchaser

    …at this point in May each year, I recommend counseling for Kevin…preferably combined with a 2-week prescription for some sort of pill depending upon the model output he is seeing at that time. He is “outta” control! -Dave

  2. … and I’m usually the optimist between the 2 of us …

  3. i have yet to decide what i think. i have discovered that if i expect the worst/have low expectations, i am pleasantly surprised even in meager situations!

  4. In a roughly 10-day period in the central US in late May, there will almost always be some notable severe weather, usually on multiple days. The northwest flow pattern sometimes presents unique situations that we have to be smart enough to nab, and we’ve done it before. Even last year produced an unusual supercell for us in North Texas.

  5. Let the games begin…

  6. I think I’ll do the same Kathryn. Keep expectations down a little…at least until it’s May 16!

  7. hokiestormchaser

    …in all honesty, Kevin and I have faced many less-than-desirable patterns over the years, and have still managed to net good storm intercepts (and some outstanding intercepts) in them. 2009 was really an exception…we did manage some storms, but they were not nearly of the caliber we have come to expect on these trips. When you wake up in Storm Lake IA with dewpoints in the 30’s in May…all is not well with the pattern! I have a tendency to low-ball my expectations just like you have mentioned…but, for some reason, I have higher expectations this year. This is the least field-tested crew we have had in recent years, but my initial impression is that it is among the strongest we have had…which explains part of my optimism. Kev: what was your informal pre-trip storm tally for quality storms, wall clouds, and tornadoes? -Dave

  8. My guess for the May trip: 7 quality storms, 5 wall clouds, 2 tornadoes. I think the pattern is going to be fairly zonal (west to east flow) with occasional shortwaves moving through. Neither a ballistic pattern nor a dead one.

  9. hey will!

    quality storms: 9
    wall clouds: 6
    tornadoes: 5

  10. And Kathryn … you say you have LOW expectations … wow.

  11. conflicting emotions…?

  12. hokiestormchaser

    …Kevin will remind you that you may see multiple wall clouds from one sustained supercell that undergoes multiple RFD occlusions…AND, if you are on THE storm, multiple tornadoes from one storm too. 🙂 -Dave

  13. hokiestormchaser

    Chris: the games have been playing in my mind for quite awhile…I’m sure to you too! -Dave

  14. hokiestormchaser

    AR tonight: deaths confirmed in Van Buren, and damage in Lonoke…hope our catfish restaurant is okay! -Dave

  15. Just got off the phone with my mother who is under a tornado warning … don’t really think it will be too bad for her as storms are lining out and showing broad rotation vs. tight/deep rotation. But she’s been through this drill many times before. Sirens are going off.

  16. Wow! Another High Risk in the Mississippi valley region. With the wind shear and available CAPE already in place those folks could see more long track violent tornadoes.

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