5/24/09 DISC: TN/AR/MO

[Jason Bolt]

Yesterday there were 10 tornado reports, 6 from a group of storms that tracked east to west across west TN into AR and MO. I watched most of this on radar and could not get over how many storms were moving west or wsw throughout the day. What ingredients were in place for this to happen? I was driving home from the holiday and encountered a non-severe storm in SE KS that also was moving straight west.

Also, in looking at the SWODY1 the area in TN/AR/MO that saw tornadic cells was not within the 10% thunder line for the outlook that was in place when the first tornado was reported. (Later a SEE TEXT was added for the area). How does that happen? Not being critical in anyway of the SPC, just curious how there can be zero signs that something like that may happen.

 

[Jeff Duda]

Those storms were associated with a tropical low that moved inland over the weekend. They were wrapped into the circulation, which, in the position the storms were in relative to the low, caused them to move westward. It can happen in any tropical situation or when the flow is weak, as it is in most of the US right now. Also, whenever a tropical system moves over land, friction at the surface slows surface wind speeds, but low-mid level winds do not slow, so shear can increase to the point where tornadoes can form pretty easily. I'm pretty sure the storms that spawned the tornadoes were not supercellular.

 

[Kelley Austin]

I watched a small ropppy funnel over Newport, AR yesterday afternoon about the time a Tornado was reported about 20 miles east of here. Lasted all of about 30 sec. Surface winds were about 25 to 30 at the time, The system that moved through here yesterday was very much Tropical.