May 16, 2011

Storm Chase Trip 2011 -- In to the Great Plains, May 19th

Well, it's hard to believe that a year has gone by....but here we are about three days before our trip into the Plains. The long range forecasts have been showing a favorable pattern for the first week or so of our trip.
The first graphic here is the composite (average) of 500 mb weather patterns for similar weather maps at this time of year in the shows a fairly dramatic trough in the far West, setting up a favorable jet stream pattern over the Plains.

The dates shown on this figure indicate the best matches from past years, by year and date. We won't try very hard to look at that, because some of those dates include some very significant tornado events.

We'll be posting each day, and probably on the fly during the day, as we can now post images via our cell phones, and we'll have live access to the web in the car. We're looking forward to this, our 26th storm chasing time has flown. Meanwhile, Thom will be posting updates to his blog. That's the real story behind the scenes....

The pattern on the day that we arrive in Denver, May 19th, is setting up nicely for some severe thunderstorms in north central and central KS. So our target will be the area from Salina back west to Hill City or so (of course, to be adjusted as approach the time of our departure). The map shows our target as a blue box, and you can see we will be at the intersection of a dry line, cold and warm fronts...often called a "triple point" by storm researchers.
I have plotted a sounding and hodograph for the region between Hill City, KS and Salina for around 6PM CDT for Thursday. The red area shows the surface-based CAPE (the region where an ascending air parcel will be warmer than its surroundings and will freely loft). The hodograph is very interesting, as it shows that the low level wind shear will be quite strong, 20-30 knots underneath a very strong southewesterly jet. If this profile develops, then storms will rotate strongly, and the low level shear tells us that isolated storms are liable to become tornadic.