Posted at 9:50 AM on August 20, 2009
by Paul Huttner
NWS storm reports show severe weather events clustered around the Twin Cities.
They don't teach you this stuff in meteorology school.
Wednesday's severe weather and tornado event was highly unusual. This was far from your classic textbook severe weather day. Here's why.
-A potent upper level low was producing rain in the area. A smaller mini low or "vortex" rotated around the larger parent low right over the Twin Cities around 2pm. This mini vortex triggered the tornadoes that hit the metro.
-This was a "non-supercell" type event. There were not classic individual supercell thunderstorms marching toward the metro as is usually the case with tornado outbreaks.
-There was no clearing to cause surface heating.
-There was very little lightning with these storms.
The unusual synoptic situation did not signal a classic severe weather day. As a result there was:
-No Storm Prediction Center (SPC) risk area for the metro. That means the best severe weather minds in Norman, Oklahoma did not see this one coming.
-No severe thunderstorm or tornado watch was posted for the area.
-No warnings issued before the first (likely to be confirmed today) tornado touchdown in south Minneapolis.
-No sirens sounded in Minneapolis before the first twister.
The Twin Cities NWS did do an excellent job of reacting once the first tornado was sighted. I believe all subsequent tornado touchdowns were covered by tornado warnings after the first event.
The event then evloved into a non-tornadic high wind event for Duluth. It was remarkable in that the system resembled a mini hurricane at times. NWS Duluth even noted an "eye-like structure" and "spiral rain bands" in the description of the high wind warning.
In 25 years of watching weather professionally I have never seen a day exactly like Wednesday. It's amazing how things can come together in unusual ways to trigger severe weather events. Wednesday was likely a once in a lifetime severe weather event.
I know you said in your 25 years nothing like this has happened. My question is has anyting like this Ever happened?
Love the blog!
I am wondering if this tornado event is similar to one t hat occurred in the early 80's that did damage in Edina before cutting a swath of damage from SW to NE across Lke Harriet in S. Minneapolis. My recollection of the weather was that it was relatively cool and rainy like yesterday. Does the diminishing of the urban heat island make yesterday's events more likely?
I'm sure something similar has happened somewhere. I just don't recall an event or case study that resembles this one.
That's the beauty of weather; it'll throw us a curve ball now and then.
Tom: I remember that storm well. It was June 14th, 1981. I was at Lord Fletcher's on Lake Minnetonka when huge hail began to fall. A friend and I followed the storm from Excelsior right into south Minneapolis. (Okay we were going to see Sussman Lawrence at Duff's near 26th & 26th)
We came upon damage moments after it had occurred.
I recall that storm as being a little more typical than yesterday's event.
Cathy Wurzer did an interview with my former WCCO colleague Bill Endersen remembering that tornado here.
I live near the E 48th St and Park avenue area and surveyed the damaged from my car. The trees seemed to be uprooted and mainly to have fallen to the west. Damage further north seemed to have trees that have snapped off at their trunks and trees that have fallen in any direction.
I am reading now that the tornado is said to have started at E 53rd St and Park ave.
I do not know the definition of a tornado vs straight line winds, but couldn't some of the most southerly damage really be high velocity winds generating the tornado.
It sounds as though a tornado was formed just above the ground and in fact thousands of people were witness to the formation of a tornado that they were inside of.
The rapidity of the damage and the funnel cloud being all the way up near 94 and 35 W seems to be faster than a tornado that would have traveled from E 53rd to the southern part of downtown
They don't teach you this in weather school? Really? And just what exactly is "weather school"?
Having a undergrad degree in meteo qualifies one for precisely nothing, save the potential to get into a graduate program in meteo. And even then, it says nothing of one's operational meteorology skills. It's quite astounding the hubris exhibited by weather presenters/readers in popular media outlets.
I point this out because people need to be aware -- particularly those that narrowly escaped injury yesterday -- that operational meteorology failed yesterday. It failed in epic fashion.
It is the responsibility of those in positions of authority, and those that are actual experts in the field of operational meteorology, to come forward and point out that, despite assertions to the contrary, operational meteorology is far from a perfectly understood science.
In addition, many millions of tax dollars spent on the national nexrad doppler radar system (so crucial in identifying rotating updrafts and tornado vortices--frequently before they ever touch down--and which has likely saved many 100s of lives since going operational) also failed yesterday--at least initially. After a certain point, it was clear that the local NWS offices were seeing TVSs everywhere and starting to (wisely) cry wolf.
Yesterday, nearly every atmospheric severe weather index (excepting perhaps vorticity at lower levels) was below severe thresholds. The impressive pinwheel MCS/MCV associated with this event--so typical of summers in the northern great plains--are mesoscale features that frequently fall out of or completely skew synoptic level models. As such they are not part of the current regime of operational models and poorly understood. (In fact, the entire concept of severe weather associated with elevated convection seems to completely elude people that spend their lives transfixed on observing/chasing severe weather.)
This should be a call to a shake-up. At the very least, the TVS identification methods clearly need adjusting. And attitudes among SPC forecasters could use adjusting as well. The convective outlooks issues by their lead forecasters previous to the event, and the one written by one of their outlook forecasters serve to document the problem.
Since nobody was killed, it not likely that anything will happen, and that is unfortunate.
Who decides to turn on the Tornado sirens in this area?
This comment is late, nevertheless, important enough I believe to be said. This rare tornado touched down at approx. 2pm. At this exact same time, something monumental was taking place at the Lutheran church. Some thing important enough that the One who controls the weather would take notice.
The Lutheran church, at precisley 2pm, was voting whether or not to allow homosexuals as Pastors. Needless to say, the church voted to allow this by a 68 to 32 percent margin!
The tornado ripped through the streets, damaging the convention center where the votes took place, and also the church steeple, topling the cross over end upside down!
My belief, the Lord did not approve of this vote!!!