Wednesday, June 13, 2018

Landspout vs Tornado

It was probably the most photogenic landspout I have ever seen in Arkansas.  At first I thought it was only on the ground for a couple minutes.  However, now I have learned from eyewitnesses that it was on the ground for a whopping 11 minutes.  That's incredible.  As of the time I'm writing this, I have heard of no damage or injuries.

A landspout is not a typical tornado.  Even though their formation processes are different, they are counted as tornadoes for record keeping purposes.  This will likely go down as the 25th tornado so far this year in Arkansas as of June 13th. 

The landspout formed as storms began to develop when 2 outflow boundaries collided in eastern Arkansas.  1 was moving east away from the metro while another was moving west towards the metro.  The two boundaries are a little north of what I had circled. 

So what is the difference between a landspout and a tornado?  Here's a great explanation from the NSSL (National Severe Storms Laboratory)... 

"Tornadoes come from mainly two types of thunderstorms: supercell and non-supercell.
Tornadoes that come from a supercell thunderstorm are the most common, and often the most dangerous. A rotating updraft is a key to the development of a supercell, and eventually a tornado. There are many ideas about how this rotation begins. One way a column of air can begin to rotate is from wind shear – when winds at two different levels above the ground blow at different speeds or in different directions.
An example of wind shear that can eventually create a tornado is when winds at ground level, often slowed down by friction with the earth's surface, come from the southwest at 5 mph. But higher up, at 5000 feet above the same location, the winds are blowing from the southeast at 25 mph! An invisible “tube” of air begins to rotate horizontally. Rising air within the thunderstorm tilts the rotating air from horizontal to vertical – now the area of rotation extends through much of the storm.

Non-supercell tornadoes are circulations that do not form from organized storm-scale rotation. These tornadoes form from a vertically spinning parcel of air already occurring near the ground caused by wind shear from a warm, cold, or sea breeze front, or a dryline. When an updraft moves over the spinning, and stretches it, a tornado can form. Eastern Colorado experiences non-supercell tornadoes when cool air rushes down off the Rocky Mountains and collides with the hot dry air of the plains. Since these types of tornadoes happen mostly over scarcely populated land, scientists are not sure how strong they are, but they tend to be small.
One non-supercell tornado is the gustnado, a whirl of dust or debris at or near the ground with no condensation funnel, which forms along the gust front of a storm.
Another non-supercell tornado is a landspout. A landspout is a tornado with a narrow, rope-like condensation funnel that forms while the thunderstorm cloud is still growing and there is no rotating updraft - the spinning motion originates near the ground"

I can't thank all of you enough for sending pics and videos.  Here's one from Jason Reynolds.

Friday, June 01, 2018

Severe Saturday

In this video...

  • Near record breaking highs
  • High heat index temperatures
  • Severe storms possible
  • Possible threats
  • MUCH cooler and drier air follows

The NEW Arkansas Weather Blog