Thursday, August 20, 2009

Minneapolis tornado, New York City's violent winds, Anchorage's tremors

Twin Cities Doppler Radar display around 2 pm yesterday, showing a tight velocity "couplet" over south Minneapolis. The bright red area is wind moving away from the Doppler site in Chanhassen, the bright green smudge is high velocity air moving toward the radar - evidence of a small, tight, vigorous mesocyclone, a rotating thunderstorm capable of damaging winds, in all probability, an EF0 or EF1 tornado. We were in a "slight risk" of isolated severe storms, according to SPC. But no watches were in effect at the time the tornado touched down, the local NWS would issue a tornado warning for this cell approximately 15-20 minutes later, around 2:20 pm, after the circulation had passed directly over downtown Minneapolis (debris was spotted from a number of downtown high-rise office buildings!) Thankfully it was a "minor" tornado - had it been a major tornado there would be a lot more red faces today.

Nature reminded several American cities of its powerful presence in the last 24 hours.

Both Minneapolis and New York City are cleaning up, the former after a tornado struck south of downtown on Wednesday, the latter after a storm brought hurricane-force winds Tuesday night that toppled scores of trees in Central Park, including giant American elms more than 100 years old.

Meanwhile, Anchorage, Alaska was shaken on Wednesday by a magnitude 5.0 earthquake which apparently jangled some nerves but didn't break anything.

According to the Minneapolis Star-Tribune, the Minneapolis tornado destroyed trees and caused some damage to buildings but caused no injuries.

An excerpt:

"This dispels myths that tornadoes don't hit urban areas, they go where they want to," said Pete Boulay, assistant state climatologist. "It doesn't happen very often, but they do happen."
Northbound Interstate 35W at Hwy. 62, already a tangled mess at the southern edge of Minneapolis because of construction, is closed due to flooding.
Central Lutheran Church in downtown had an old copper steeple damaged, and two tents used for entertaining also were struck. One was blown into the street and the other was collapsed, said church spokesman Joe Bjordal. The tents were set up in connection with the national gathering of about 2,000 at the Evangelical Church in America at the Convention Center. "We're thankful that nobody was hurt," Bjordal said.
Representatives on the convention floor could hear rain on the roof, but only became aware of the turbulence outside when unofficial convention-goers were moved in from the outside corridors for their safety.

(There is still some question about whether the wind damage in Minneapolis was caused by a real tornado or straight-line winds, a "wet downburst", I've heard a number of competing theories. But after looking at the video [check it out on WeatherNation's main web site here], after hearing the reports from survivors - those in the path of the storm - AND - after seeing the Doppler SRV, storm relative velocity image from 2 pm yesterday, sorry, I don't think there's any question this was a tornado).

I know this makes a number of people uncomfortable - no severe watches or warnings were in effect at the time, no local media was on the air giving advance notice of this potentially dangerous/deadly situation. A lot of people would LOVE for this to go away, or be designated as straight-line wind, which doesn't have quite the stigma, or impact of a TORNADO. I'll be amazed if it was anything but a small EF0 or EF1 tornado. BTW, the rest of the article from NPR is right here.

Sunday, August 16, 2009

Big tropical storms in the Atlantic hit a 1,000 year high

The people of U.S. Gulf Coast have felt unusually battered by big storms during the past few years. Now, it turns out their instincts are right.

A new report in the scientific journal Nature indicates that the last decade has seen, on average, more frequent hurricanes than any time in the last 1,000 years. The last period of similar activity occurred during the Medieval Warm Period.

The study is not definitive, but it is a unique piece of work that combines an analysis of sediment cores from inland lakes and tidal marshes with computer modeling and finds a "striking consistency" between the two, the authors suggest.

The use of sediment cores to place and date ancient storms -- called "paeleotempestology" -- is becoming an increasingly useful tool in the broader effort to try to reconstruct the history of hurricane activity in order to better predict a future potentially influenced by climate change.

The complete ABC News story is here.

Considering a tornado chasing vacation?

A group from Silver Lining Tours scanned the skies over eastern Colorado in June for signs of a tornado.

“WE’VE got to go right now, folks,” Roger Hill shouted on a recent Monday afternoon in Scott City, a beautiful speck on the map of western Kansas. “We’re going east. The eastern storm is a monster.”

After waiting hours on a sultry day — first at a Pizza Hut, then at a Dairy Queen — we finally heard the words we had been waiting for. We were on the second day of a tornado chase in the Great Plains led by Mr. Hill and David Gold, owners of Silver Lining Tours, a 12-year-old company that specializes in extreme-weather travel, and it seemed that our quarry was finally within reach.Along on the journey were seven tourists, from Oregon to England — each had paid $2,200 for a six-day storm-chasing vacation devoted to seeing some of the world’s worst weather up close — and me, a reporter shadowing their experiences for two days. It was not, as you might imagine, a typical vacation. As Russell Glenister, from London, told me, “Most of the time when you tell people you’re chasing tornadoes, they think you’re crazy.”

(I have chased tornadoes on 3 separate occasions, and gotten "lucky" each time, although the truth of the matter: I had to invest a couple of weeks each time I went out before I actually saw a tornado. The first few days you invariably see hail, rainbows, thunderheads of every possible shape and dimension - a LOT of false alarms. If you know what you're doing and how to approach a severe local storm the threat to life and property is fairly small and manageable. The biggest risk is being hit by lightning, or some yahoo driving at 100 mph + to try and intercept a twister and get the money shot! It is the most amazing visceral rush you can ever imagine - a buzz to end all buzzes! Not sure you have to pay thousands of dollars to see a tornado - one of the cheapest, most effective ways to see a tornado is to fly to Oklahoma City, rent a car [never use you own car, the hail damage risk is off the scale!] and drive down to NSSL, the National Severe Storms Lab in Norman, Oklahoma, and TAG ALONG with the pro's. That's right, stalk the pros! The best time to go is late April into mid May. If you spend at least 2 weeks in Oklahoma, and are willing to drive a rental car (fast) into Texas, Kansas, Nebraska - if you're tenacious, you WILL see a tornado!)

For the complete New York Times article from Brian Stelter click here.