Tornado Recap (and news of a very nice weekend)

Multi-vortex Tornado. The tornadoes that formed in the sky above Minnesota Thursday PM were Kansas-size twisters, in some cases nearly 1/2 mile wide, large, long-lasting, violent tornadoes, more common in Oklahoma and Missouri than the Gopher State. A few were multi-vortex (wedge) tornadoes, so big and fat they didn't even resemble typical tornado funnels. A multi-vortex tornado is composed of 3-8 mini-tornadoes, all rotating around a common center. If one of those violent vortexes passes overhead total damage is all but insured. This accounts for crazy stories: one home flattened, while the home across the street suffers only minor damage. To see the video of the tornado that hit near Albert Lea click here.



Wadena: Before the Tornado Struck. Doppler radar did an amazing job tracking Thursday's tornadic storms. At WeatherNation we use a "Vipir" Doppler Radar system that measures wind velocities inside tornadic storms, detecting the most intense wind "shear". Thursday's supercell thunderstorm bearing down on Wadena was SCREAMING tornado - all the indicators were present: over 100 mph of spin, a BTI (tornado index) over 7 (on a scale from 1 to 10), and we were getting suggestions of 4" diameter hail from this mega-storm. The bigger the hail = the stronger the updraft = the greater the potential for tornadogenesis. The NWS issued a tornado warning for the Wadena area at least 20-25 minutes before the tornado roared into town. There was sufficient warning for local residents. A death toll of 3 from 39 separate tornadoes is tragic, but in one sense it's almost miraculous - there could have been hundreds killed had there been no warning, or had the tornadoes arrived late at night, after dark, when tracking becomes difficult to impossible. More on the chronology of Thursday's outbreak below.

NWS Statistics from Thursday's Tornado Outbreak

* 36 separate tornado REPORTS. The actual number of individual tornadoes has yet to be determined - some of the 36 separate reports were almost certainly people seeing the same tornado from different vantagepoints.

* Intensity: NWS damage teams on the scene are reporting EF-0 to EF-1 damage from most of these storms, which surprises me a bit, based on the extent of damage. I thought a few of these would be stronger than EF-2.

* Number of tornado warnings issued by the Chanhassen NWS office: 26.

* Severe thunderstorm warnings issued by the same office: 23.

For more details from the Chanhassen NWS Office click here.



39 tornado touch-downs and counting. How did we (seemingly overnight) become Kansas - with lakes? We go from NO tornadoes through midday on June 17 to 39 separate twisters over an 8 hour period, from mid afternoon into the evening hours last Thursday. I've seen a lot in my 30 year meteorological career, but Thursday's wild tornado outbreak left me dazed, in a state of suspended disbelief. Did that really just happen?



I remember looking at the maps Thursday morning, seeing the moderate risk from SPC, the wind shear, instability, 70-dew point air surging in from the south, and a warm frontal boundary snaking across the state. I went on record saying "we will see our first tornadoes of the year today." But nothing could prepare me for the atmospheric convulsions that resulted.

Doppler radar works best on the big tornadoes, the EF2-5 twisters that form underneath solitary, "supercell" thunderstorms. That's exactly what happened during the afternoon hours last Thursday, huge, rotating storms began to blossom along the frontal boundary. No one can say that there wasn't ample warning. Just about the entire state of Minnesota was under a tornado watch until 9 pm, and (interject personal opinion here) the local NWS office did a VERY good job getting warnings out in advance, based on the velocity fields showing up on their Doppler screens. Doppler measures not only the location of a raindrop or hailstone, but also whether that raindrop or hailstone is moving toward, or away from the radar site. Using algorithms Doppler radar can measure the intensity of these wind fields, detecting areas of spin, small, focused "couplets" - where air is rotating violently. The big challenge: is that rotation taking place 4,000 to 25,000 feet above the ground, or is it actually reaching the ground? That's where professional (SKYWARN) storm spotters and law enforcement come into play - providing the ground truth, the verification we need when issuing warnings to the public. Sometimes the most intensely rotating storms DO NOT spin up tornadoes, in fact 70% of all tornado warnings (based on rotation alone) turn out to be false alarms. That can lead to a dangerous "cry wolf" scenario...."oh, there they go again, another warning. We never see anything here. Best to ignore them." People in Wadena and Albert Lea and Almora and Buffalo won't be taking any tornado warnings for granted anytime soon.

Chronology of a Killer. This is what the Vipir Doppler Radar looked like shortly before 4 pm Thursday, a "shear marker" showing up near Wadena, suggesting violent rotation reaching the ground. A BTI (Baron Tornado Index) of 7.1 provided very strong evidence of a tornado on the ground, and during a video update I mentioned "I'm almost certain there is a tornado on the ground with this storm right now." About 25 minutes later a tornado ripped into Wadena, producing widespread damage, claiming at least 2 lives.


Video of the Hollandale, Minnesota tornado can be found here.

What we're discovering is that the intensity of the spin showing up on Doppler is just one (of many) important factors to consider. The environment surrounding the storm is just as critical. Is there a generous supply of warm, humid air surging into the supercell? Is the surrounding airmass warm (and buoyant)? RFD's, "rear flank downdrafts" within severe T-storms are thought to be the mechanism that pulls severe rotation down to the ground, but research is showing that tornadogenesis requires warm, buoyant downdrafts. We look at hundreds of parameters when determining when/where a tornadic storm may form. Some of these tornadoes moved at 45 mph, a few were preceded by monstrous hailstones (4" diameter in Douglas County, near Wadena). I'll say it again: if you witness big hail, anything larger than golf ball size, it means the T-storm updraft overhead is exceptionally intense. If it's strong enough to keep baseball or softball size hail suspended aloft, it may be severe enough to initiative nature's most intense updraft, a tornado.


Extreme Shear. Notice the small box: 103.57 mph of wind shear, meaning over 51 mph of shear in each direction, toward and away from the NWS Doppler in Chanhassen. BTI was still 7.1. Anything above 4 or 5 suggests a tornado on the ground.


Revolutionary Tools. The average lead-time for a tornado in the US (the time between when a warning is issued by the local NWS office and when the tornado ACTUALLY HITS) has doubled, from 7 minutes in the 1970s to nearly 15 minutes in 2009. Doppler Radar is largely responsible for this improvement in safety, but the contribution from storm spotters (including the public) on the ground can not be underestimated. The system works best when Doppler is complimented with reliable reports from professionally-trained spotters.

I want to make an important distinction. Storm SPOTTERS are the SKYWARN professionals who have taken classes, know the difference between roll clouds and wall clouds, don't confuse scud with funnels, know what to look for with rotation, etc. Storm CHASERS are the men and women with cameras who try to get into a position to get the "money shot", the actual moment when a tornado touches down. On Thursday storm chasers from as far away as Texas and Oklahoma were in Minnesota, converging on the developing tornadoes (especially the cluster near Albert Lea and Kiester). One great 5:00 to 10:00 clip of a tornado on the ground can fetch thousands of dollars from local TV stations, the Weather Channel, etc. Yes, you can make a living chasing (and filming) tornadoes, and hundreds of people in the USA do just that.

I've chased my fair share of tornadoes, mostly in Oklahoma (where it's flatter, easier to get around, and there are 3-6 times more twisters than Minnesota). To tell you the truth: I'm not scared of the tornado itself. What scares the crap out of me are the chasers, who will sometimes drive in excess of 100 mph, weave in and out of traffic recklessly, doing anything/everything to reach a developing tornado to GET THE SHOT! At some point there will be a horrific traffic accident - I've seen chasers blast through stop signs, pass on double-yellow lines, do stuff that could easily get them locked up in jail for a least a year or two - just to get into position to have cameras rolling when the twister touches down. Crazy. But when the warning is issued, when you see the hook on Doppler, the wall cloud rotating off in the distance, adrenaline kicks in, the competitive juices start flowing - everyone wants to be able to call the local TV affiliate and say, "I got it - I have the tornado on tape!"

Aftermath. The Deer Creek High School in Wadena was heavily damaged from Thursday's tornado - you can see the mangled cars in the parking lot, tossed around like toys by winds that may have approached 200 mph. at times. This is tangible, visible evidence why you don't want to be in, under or near a vehicle during a tornado. Best to get out of your car/truck and either seek shelter in a building or nearby ditch. Image courtesy of startribune.com.

Mentor Damage. One of the 3 fatalities took place in this gas station, which seems to have suffered a direct hit from the tornado. NWS employees are on the scene, analyzing the damage pattern, calculating how far heavy objects were tossed when making their determination of the severity of the tornadoes that touched down from near Grand Forks to Wadena to Buffalo and Albert Lea. Photo courtesy of startribune.com.

Stunned. More damage photos from startribune.com. Many of the tornado survivors will suffer something similar to PTSD, post traumatic stress disorder, the same shock that many soldiers have to grapple with after returning from battle. The sudden (severe) stress, coming face to face with possible death, will haunt many of these local residents for years to come, many will need therapy to cope going forward. PTSD storm survivors often complain about inability to concentrate when storms are in the forecast, elevated heart rate, sweaty palms, irritability, and these are only the milder symptoms. Wadena residents just went through a war, a weather-war.

Winsted Damage Path. Track of the tornado that hit just north/west of Winsted, sparing the town itself. Image courtesy of the NWS. To see the actual (detailed) storm evaluation click here.

Buffalo Damage Path. Another near-miss for a heavily populated town, the tornado spared downtown Buffalo, passing north/west of town.

Friday Almanac. Yesterday we experienced more of a "dry front" than an actual cool front. Winds shifted around to the southwest, then from the west, pumping much drier air into town. There's about half as much water vapor overhead now than there was Thursday afternoon, before the tornadoes developed. Friday highs ranged from 63 at Grand Marais to 82 in St. Cloud, 86 in the Twin Cities and Redwood Falls. Rochester picked up nearly 1.4" of rain.

Amazingly, I don't see any last-minute flies in the weather ointment, no flies in the weather ointment which will sneak up and bite me (us) in the butt, but I don't see any weather-monsters lurking out there. Today will be sunny, with low humidity, gusty winds (from the west/northwest as high as 20-25 mph through midday, easing up a bit by evening).

Sunday a sloppy storm passes off to our south across Iowa, brushing far southern counties with thicker clouds and a few hours of showers and T-storms, from Fairmont and Worthington to Albert Lea and the La Crosse area. Here in the metro area we may see some patchy high cirrus clouds, dimming the sun from time to time, but I still expect enough sun for highs near 80 (with less wind).

Saturday looks sunnier (but windier statewide).

Sunday will be a bit cloudier (southern quarter of MN), but winds will ease considerably.

Not bad for mid June. Comfortable for Grandma's Marathon in Duluth (pack your sunscreen), fantastic conditions for the Jazz Festival in St. Paul, not a bad Father's Day statewide. BTW Monday at 6:28 am marks the official kick-off of summer. The Summer Solstice is imminent, the best day of the year (in theory) for a sun tan (or burn). Enjoy the extra-long days, the late sunsets (well after 9 pm). I love that....looks like a super-sized summer weekend. Finally, Mother Nature shows a little mercy....

Close Call. The latest NAM/WRF model shows a storm sliding off just to our south Sunday morning, throwing a shield of clouds into the southern third of MN, the thickest clouds staying south of the MN River, any showers brushing far southern counties along the Iowa border. The NAM model (probably the most reliable) keeps most of Minnesota dry all weekend long. Remarkable!

But wait, there's more!

Storm Front. Check out this amazing time lapse of a front surging into northern Iowa from KCRG-TV's web cam. One of the best I've ever seen.

Come to Florida - the Most Oil-Free State on the Gulf! You have to feel sympathy for Floridians - they derive ZERO income from oil drilling in the Gulf of Mexico, yet their towns are increasingly threatened by the growing slick of crude washing onto their sugar-sand beaches. Most of Florida is, in fact, still pristine - unaffected by the spill. But Florida is launching a nationwide advertising campaign, reminding Americans that they can still come down and enjoy the Sunshine State. There's a lot a stake, an estimated $60 billion (with a b) in tourism revenue that is already being impacted. More on the impact in Florida here.

* Anderson Cooper Becomes Loud Voice for Gulf Residents. The story in the N.Y. Times is here.


Somewhere Over The Rainbow. I've seen a lot of photos and video clips of the impact of the oil spill on the ecosystem of the Gulf of Mexico, but nothing quite like this. Yes, it's set to music. Yes, it was created to tug at your heartstrings, your emotions. But what's happening in the Gulf is more than a scientific challenge, it's an environmental catastrophe unlike anything our nation has ever experienced. It IS an emotional tragedy, summed up all too well in this heartbreaking video.

Climate Stories.

* Climate Change Deniers doing a Disservice to Legitimate Science. Amen to that. The story in the Vancouver Sun is here.

* Shadow Elite: Merchants of Doubt. Do Scientific Denialists Have No Shame? Short answer: no. Naomi Oreskes is the Phd scientist who studied over 900 research papers from climate scientists, trying to determine if there really was any lingering controversy among peer-reviewed scientists about whether man is responsible for much of the warming we're measuring worldwide. Listen to the mainstream media and you believe there is still doubt, still a significant number of scientists who aren't convinced about anthropogenic climate change. There is a growing cottage industry in "experts" who are paid to keep doubt alive. There is a lot of money at stake, and just like the manufactured "controversy" over the ozone hole, acid rain and the effects of smoking and lung cancer, there is money to be made by floating pseudo-science, by cherry-picking specific events or data to make a case that this is all one great big coincidence and climate scientists are "overreacting". Decide for yourself - keep an open mind. If a better theory comes along that explains what we're seeing worldwide, I'll be happy to change my mind. But for me the critical mass of evidence came in the late 90s. Since then more pieces of the climate puzzle have fallen into place. One snowy winter in Washington D.C. doesn't disprove anything. The evidence is compelling, and growing larger every day. Unless NOAA, NASA and the National Science Foundation are all in on this "conspiracy" I'd say we have a problem on our hands. We can either deny and delay, or decide that this is, in fact, a real issue, and take steps to mitigate some of the worst impacts. At some point our kids and grandkids are going to ask, "what did you know, and what did you do?" A moment of truth is inevitable. At some point the deniers will go into hiding and deny they ever denied. That's my prediction. Sadly, I think we've probably passed the point of no return - barring a series of climate disasters I can't see any real chance of banding together (internationally) to tackle climate change in the near future. My hunch: we'll have to get very serious about adapting to a warmer, drier, stormier world. It's already happening, and it's going to get worse. And I'm a naive optimist! I hope I'm wrong on this one...

The story is here.

Paul's SC Times Outlook for St. Cloud and all of central Minnesota

Today: Plenty of sun, low humidity, stiff breeze (best Saturday in over 3 weeks!) Winds: W/NW 10-20+ High: 76

Saturday night: Mostly clear, comfortably cool. Low: 55 (low 50s up north).

Sunday: Sun dimmed by high clouds, showers/storms brush far southern MN, near the Iowa border, most of the state remains dry. Winds: SE 8-15. High: 78

Monday: Partly sunny, slight chance of thunder. High: near 80

Tuesday: Unsettled with more clouds/humidity, better chance of thunder. High: 84

Wednesday: Drier and sunnier statewide. High: 86

Thursday: Fading sun, clouds increase - thunder late? High: 85

Friday: Mostly cloudy and sticky, T-storms likely. High: 81