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Here's a quick preview of this month's contents:
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Davis stations walk the beat of Tornado Alley.... E-news touches down with twister truths and trivia.... A retired pro replies to our article on rooftop rain readings.... And we announce the winners of the North Pole Weather Challenge... Enjoy!

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Cool Application: Patrolling Tornado Alley
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Three quarters of the world's tornadoes touch down each year in the United States, and the greatest number of these occur in "Tornado Alley" - a region in the Central Plains that stretches from central Texas to Nebraska. How do people in Tornado Alley cope? One of our station owners in Oklahoma, John Utech, heads up a group whose mission is to track approaching tornadoes and alert those in its path. We asked John to tell us more about what his team actually does. This was his reply:

>Ok, let's set the stage.

>The county in which we live still has the lead on this planet for the most tornado warnings, but we are followed closely by the county south of us.

>Now go get an atlas or something that shows Wichita, KS, Tulsa, OK and Oklahoma City, OK.... Now find Interstate 35 which runs north and south cutting Oklahoma in half. Find the intersection of the Oklahoma-Kansas border and Interstate 35. We are about 15 miles south of that intersection... the heart of Tornado Alley.

>Our location, if you notice, is between the three previous metro areas. This section of Oklahoma and parts west are basically out of the "profit" range of those cities as far as weather coverage. However, the Emergency Operation Centers (formerly known as the "Civil Defense") are without a doubt the best equipped in the nation for these type of storms. These E.O.C.'s are all equipped with NEXRAD systems, known in this state as "OK-First". In a nutshell, the E.O.C.'s notify city governments, law enforcement agencies, and emergency personnel so that all are prepared for nothing...or...the worst!

>The only thing left is getting the information to the public. Well, the metro TV stations will mention storms in this area as long as there isn't any severe weather going on as far as the metro's area. In all fairness they do the very best that they can while still keeping their main market area covered.

>This is where our "Weather Lab" comes into play. We are under contract with a nearby radio station that will broadcast the warnings, watches and special weather statements that we receive from the National Weather Service (NWS). The Weather Lab's chief meteorologist, Tim Bradfield, will make almost all the announcements to the public over the radio and TV. We also have our own spotters, chasers and interceptors. It's kinda run as a military operation once things get going. We make use of the spotters who are stationary, the chasers who seek out the worst part of the storm to watch for rotation in the lower part of the storm, and the interceptors who wait for the "core" of the storm to roll over them in order to inform and confirm what radar is indicating. Things like is there hail? How big? How fast is the wind?

>Now what do we use? We are in touch with all of the E.O.C.'s and their directors, Sometimes we are the ones who actually inform the directors of what's going on. We use scanners, as well as satellite feeds from the NWS & the Storm Prediction Center (SPC). We have real time NEXRAD radar, lightning detection and counters and, of course, Davis Weather Stations. We use Davis data to check the barometer rate, the wind direction and speed, and the dew point (the dew point is VERY important in this area). My job is the chaser and interceptor and CEO. I was trained for over 20 years in this area. I saw my first tornado at the age of 7 and have chased them ever since.

>During the May 3rd Kansas-Oklahoma outbreak, we also had tornado warnings in this area. To give you an idea of how good the warning system is here: the small town of Mulhall was completely destroyed the next day. There was only one injury, and that was when the poor man was getting out of his cellar and cut his finger on a piece of broken glass.

>By the way, the tornado in Oklahoma City was on the ground for about an hour, during rush hour, going through residential areas, leaving nothing but the foundations. It was a half-mile wide and it traveled 19 miles on the ground. The citizens had almost 3 hours warning of the approaching storm and though there were a lot of injuries, so far only 44 deaths....

Thanks, John, for giving us a peek into Tornado Alley's awesome defense network. We wish you the best of luck in future encounters! For more information about the recent Oklahoma outbreak, check out the National Severe Storms Laboratory site at http://www.nssl.noaa.gov/headlines/outbreak.shtml.

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Weather Whys: Twisters
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After the devastating effect of the latest tornadoes in Oklahoma and Kansas, we decided to do a little digging and learn more about them. This is what we found:

About 800-1000 tornadoes touch down each year in the United States. Most of these tornadoes cause little or no damage whatsoever, it's just the few F4 and F5-intensity whoppers that wreak havoc. Which state is the worst hit? Well, it depends on what criteria you use. Oklahoma has the highest number of significant and violent tornadoes per square mile, while Kansas has the highest number of F5-intensity tornadoes recorded since 1880. Oklahoma City, in particular, has been struck by tornadoes at least 33 times in the past 90 years.

While three out of four twisters that do touch down occur in the US, many countries around the world are hit regularly. The worst tornado disaster in history may have been when a twister struck about 40 miles north of Dhaka, Bangladesh on April 26, 1989. At least 1,109 people were killed, 15,000 injured, and 100,000 left homeless. Other twisters have struck that region and may have taken even greater tolls.

Tornadoes are still not fully understood, though each year scientists learn more. We asked Jason, our resident meteorologist, to spotlight what science does know about how tornadoes form:

>When cold and/or dry air overlays warm moist air, you have an unstable, thunderstorm-prone atmosphere. For example, in the spring, cold air off of the jet stream frequently blankets the surface air of the Central Plains. Meanwhile, below this blanket, cold air coming in from the north induces warm moist air to flow from the south. A layer of warm dry air from the southwest then caps the moist air along a boundary called the dryline, creating, in effect, a pressure cooker. Where these air masses regularly collide, you have "Tornado Alley."

>The advance of either cold or dry air into warm moist air (as when a cold front advances) forces the warm moist surface air upward where it cools, condenses and forms clouds. As more warm air rises and condenses, the storm matures and the updraft forces parts of the thunderstorm upwards into the shear environment (that is, where each air layer is moving at a different speed and/or in a different direction).

>The shear environment causes the air to spin about an axis parallel to the ground, like rolling a cigar. This axis is then pushed into a "standing" position by the thunderstorm's updraft, creating a "mesocyclone" (a small scale low pressure system). As air rushes in toward the low pressure of the mesocyclone, the rotational wind speeds increase (like an ice skater bringing her arms closer to her body as she spins). Eventually, for reasons not yet understood, this rotation is translated downward and a tornado is formed.

>There are two main theories about why this translation might occur: one, that the boundary between the thunderstorm's updraft and its downdraft creates more spin; two, that local topography induces certain wind flows that create more spin (thunderstorms and tornadoes have been observed to favor formation in certain areas over others).

Thanks, Jason, for the whirlwind tour! For more detailed introductions to the "mother of all vacuums," check out http://whyfiles.news.wisc.edu/013tornado/index.html or http://www.usatoday.com/weather/wtwist7.htm. You can also build your own homemade twister at this not-to-be-missed warehouse of all things tornado: http://www.tornadoproject.com/cellar/workshop.htm.

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Talk Back: Right as Rain
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In April's e-news we discussed some of the sticky considerations involved in siting rain collectors when ideal locations are simply not possible. Club Member Don Warner of Idaho wrote in with his own National Weather Service (NWS) account:

>I am retired from the Lewiston, Idaho branch of the NWS (located on the third floor of the airport terminal). For over twenty years, our official rain gage (a weighing gage) was on the edge of the roof outside the office. Our "eight inch" gage was also on the third floor roof. The reason they were located there, of course, was because they were then "convenient" to our third floor office.

> By the way, the office is closed now as part of the modernization and automated with ASOS (Automated Surface Observing System).

Thanks, Don, for lending some official weight to our suggestions. It is good to know that sensibility and practicality are as important to the NWS as they are to the rest of us who are concerned about readings.

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Miscellany of the Moment: North Pole Challenge Winners
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We've come full (arctic) circle! Last month we shared news of Curtis Lieber's North Pole Weather Challenge. Curtis invited club members to guess the average temperature and wind chill at the North Pole during his visit. Just last week, we received this follow-up from the still-slightly-chilled explorer:

>Congratulations to Michael Fox, Joe Denison and Rob Holtz - the winners of the North Pole Weather Challenge! I've tabulated the weather results from this April's North Pole Expedition and the average temperature and wind chill were -29 and -46 degrees Fahrenheit respectively. The North Pole Expedition recorded weather data from the North Pole between April 18 and April 24, 1999.

>For the first 30 hours the sun was shinning and the weather was calm and clear, but then the weather took a turn for the worse. For the next five days, the expedition was caught in the middle of a severe North Pole blizzard, that in fact set the polar ice cap into such a frenzy that the "Blue Ice Runway" cracked and stranded everyone at the Pole for six days. No one could see further than five feet ahead.

>Again congratulations to the winners and we will be sending them the American Expedition Patch and Logo Pin for their accurate assessment of the weather at the "Top of the World". They are also invited to join the expedition next year, if they choose such a wonderful adventure...

Thanks, Curtis, for the challenge! And thanks too for keeping us up-to-date on the latest conditions at the Pole!

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That's it for May's E-news! See you next month! To subscribe to this e-newsletter go to: http://davisnet.com/news/e_club_signup.asp

The Davis Weather Club E-newsletter mailto: news@davisnet.com