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