Middle Tennessee Weather News

Middle Tennessee tornado climatology completed: Southern Middle Tennessee may not be the mid state's "tornado alley" after all

A research paper written by meteorologist Mark A. Rose, "A Tornado Climatology of Middle Tennessee (1830-2003)," is the first cumulative study of the mid state's entire tornado database, which lists 469 twisters dating as far back as 1830. The paper has been submitted to the National Weather Association's Electronic Journal of Operational Meteorology for publication.

The area covered by the tornado climatology includes the 39 counties currently serviced by the National Weather Service in Old Hickory, plus three Middle Tennessee counties -- Franklin, Lincoln, and Moore -- that are serviced by the Huntsville, Alabama office.

Most of the conclusions reached in the study produced no surprises. For instance, population growth and warning coordination and awareness efforts have dramatically increased the number of documented tornadoes -- especially weak tornadoes -- in recent years, while simultaneously lowering the number of tornado-related fatalities.

The most common hour of the day for tornadoes to touch down is between 1700 and 1759 CST. Fifty-eight percent of tornadoes touch down during the seven-hour period between 1400 and 2059 CST. Tornadoes are least common during the early daylight hours of 0700-0959 CST.

Nearly two-thirds (66%) of Middle Tennessee's tornadoes have occurred during the months of March, April, and May. Tornadoes are least likely to occur during September.

The average path length for all tornadoes is approximately eight miles. However, this figure increases dramatically beyond F2-rated storms. The average path length for F3 tornadoes is 18.7 miles, and increases to 26.6 miles for F4 storms.

Eighty-six percent of tornado fatalities have been caused by F3+ tornadoes, which in reality constitute just 17% of all tornado occurrences. Fifty-four percent have been caused by the twenty-one documented F4 tornadoes, which represent 4% of all tornado occurrences.

During the first decade of the 1900's, tornadoes produced 109 fatalities (an average of seven fatalities per event). By comparison, a total of 102 fatalities have occurred since 1950 due to tornadic activity.

The costliest tornado was the F3 twister which struck downtown Nashville during the afternoon of 16 April 1998. The $100+ million dollar storm greatly overshadowed a much larger supercell which produced the only F5 tornado in Tennessee's history later that day in Lawrence County.

However, when the tornado database is distributed geographically, some very interesting -- and unexpected -- facts surface. Because the size of Middle Tennessee's counties are highly variable, the number of tornadoes per county were normalized according to square mileage in order that a true comparison could be made.

It is shown that nine counties have documented at least 4.7 tornadoes per 100 square miles, and are largely clustered in two geographic locations. The first cluster encompasses five counties that include the Nashville Metropolitan Area and areas east (Davidson, Rutherford, Sumner, Trousdale, and Wilson Counties). The second cluster is formed in southern Middle Tennessee by the three counties of Giles, Lincoln, and Marshall.

Davidson County has the highest frequency of tornadoes, with 7.4 per 100 square miles. Trousdale and Wilson Counties tie for second at 6.1. Rutherford ranks fourth, with 5.8. Marshall comes in fifth, with 5.3, and Sumner is sixth, with 5.1. Tied for seventh are Coffee, Giles, and Lincoln Counties, at 4.7 tornadoes per 100 square miles.

When only F3+ tornadoes are considered, there also does not appear to be any one part of Middle Tennessee that can be considered most prone to strong tornadic activity. In fact, Pickett, Trousdale, and Giles Counties have the highest frequency of F3+ tornadoes -- 1.8 per 100 square miles. And when F4+ tornadoes are broken out, Pickett County comes in first, with a frequency of 1.2 tornadoes per 100 square miles.

Guest Column
EYEWITNESS WEATHER: Weather Programming at Adventure Science Center
Valerie Johnston, Educator & Outreach Coordinator

There are definite signs that Spring is on its way to the Midstate: there will be snow one day and hot sun the next, and elementary teachers will be booking the Eyewitness Weather programs at Adventure Science Center for their young learners.

I have been an Educator with the Science Center since the summer of 2001 and have taught hundreds of students and adults about Tennessee's "wacky weather." But each program is different and each time I am amazed at how much the students already know, how much they want to learn, and how many weather misconceptions they hear.

Weather is one area of science that every child can relate to because they can see it happening all the time and they understand, at an early age, what impact weather has on mankind. This is the reason I love teaching the weather programs. I caught the weather bug in college attending a meteorology class required for my Earth Science Education emphasis. It is amazing how you can stop being afraid of something when you finally understand it! This understanding is what I try to give my students in the 45 minutes I capture their attention with vacuum jars, homemade clouds, and miniature lightning bolts.

The Eyewitness Weather programs are, understandably, one of the top choices for school groups. In this school year alone, Weather bookings at ASC have comprised 23% of the total number of school groups attending programs with 31 programs to choose from; that is approximately 2337 students since August 2003.

But weather education is not limited to students. During the upcoming June 2004 Celebrate Earth Month, ASC will host its first "Extreme Weather Event." Participation from a variety of weather resources, including the National Weather Service and NOAA, is expected to draw a large crowd, curious to know more about extreme weather-related events. With any luck, we will be inspiring the next generation of weather educators, eager to impart understanding to the public.

Valerie Johnston
Educator & Outreach Coordinator
Adventure Science Center
(615) 401-5079
vjohnston@adventuresci.com
www.adventuresci.com

National Weather Service Scores Well

The White House Office of Management and Budget (OMB) has completed its Program Assessment Rating Tool (PART) to review and rate federal agencies for the FY 05 cycle, and the National Weather Service received a score of 89 out of 100.

The average score for all agencies rated was 60 out of 100. The PART rating tool examines four key areas, including Program Purpose and Design, Strategic Planning, Program Management, and Program Results and Accountability.

The National Weather Service ranked 22nd out of the 399 agencies rated in FY 05 by OMB. The National Weather Service score was second highest in the Department of Commerce, behind the Bureau of Economic Analysis. In addition to the scores, OMB gave each agency an overall assessment, using the categories of effective, moderately effective, adequate, ineffective, or results not demonstrated. The National Weather Service was given the highest rating of "effective." Only 11 percent of the 399 programs were rated effective.

Why is this important? According to the National Weather Service's Deputy Chief Financial Officer Steve Gallagher, the external recognition always helps on Capitol Hill.

"More importantly," Gallagher said, "OMB is using the rating to make budget decisions. Agencies with effective ratings are receiving increases above inflation while agencies rated ineffective or results not demonstrated are being eliminated or receiving significant reductions in their budget pass back. Thanks to all National Weather Service employees for their daily contributions to the NWS mission and improving our performance in FY 03."

More weather records for Middle Tennessee

The National Climatic Data Center has backloaded several years of weather records for a plethora of stations, including some in Middle Tennessee. This has enabled more weather data to be loaded onto the Middle Tennessee climate database. Thus far, several decades worth of extra data have been made available to our internet users for Carthage, with an entire set of daily weather records now going back to 1890, as well as Clarksville (1890), Cookeville (1896), Dickson (1900), Franklin (1891), Lebanon (1902), Lewisburg (1890), McMinnville (1894), Murfreesboro (1890), Tullahoma (1893), and Waynesboro (1891). New cities added to the database thus far are Byrdstown and Celina, bringing the number of Middle Tennessee cities whose entire set of weather records are accessible on our website to 39.

Interestingly, the windfall of additional data from NCDC has also shed light on greater extremes at many of the locations. Previously, the all-time record high temperature for Middle Tennessee was assumed to be 110 degrees, but two occurrences of 112 degree readings have been uncovered. These occurred at Clarksville, on September 7, 1925, and Madison, on July 28, 1930. The previous accumulation of records also showed the most rainfall ever to have occurred during one calendar day to be 8.76 inches (Lawrenceburg, July 14, 1998). But that claim now belongs to Lewisburg, which measured 9.00 inches of precipitation on March 28, 1902. Not to be outdone, it has also been discovered that the assumed record for most snowfall in one day, 18.0 inches (Crossville and Jamestown), is no more. During the St. Patrick's Day snowstorm of 1892, the community of Riddleton, a few miles northwest of Carthage (Smith County), measured 18.7 inches. For the record, the all-time record low for the mid state is -30 degrees (Kingston Springs, January 24, 1963). That record still stands.

The aforementioned stations also have several "new" local records.

Greetings From the New Guy

Hello Middle Tennessee! I'm Larry Vannozzi, the new Meteorologist-in-Charge (MIC) at the National Weather Service's (NWS) Nashville office. I literally and figuratively have huge shoes to fill as I replace Derrel Martin. Derrel retired in January after serving as the Nashville MIC for an incredible 25 years.

The NWS is at a crossroads. We're changing at a faster rate than ever before, all in the name of providing more timely and accurate warnings and forecasts. I'm excited to be associated with Nashville's professional staff as we carry out the NWS mission of saving lives and protecting property across Middle Tennessee.

Here's a little about my journey to Nashville: I've been in the NWS for almost 18 years and have worked in Houston, Albuquerque, Lubbock (twice), and at our Southern Region Headquarters in Fort Worth. Most recently, I was the MIC at the NWS's Lubbock office for the past two years. I earned a Bachelor's degree in meteorology from Penn State prior to entering the NWS in 1986, and went back to school years later for a Master's in management (Texas Tech University, 1998). I realize my Penn State blue-and-white things might clash a little with all the orange-and-white things I see around here, so I'll do my best to keep a low profile during the college football season. (Hey, after the Nittany Lions' 3-9 season last year, I need to keep a low profile!)

My family and I are thrilled to be here. It seems like a wonderful place to live and raise our children. My wife is a meteorologist (though she's changing careers), and we have two young boys ages 6 and 7.

I look forward to meeting and working with our customers and partners, including emergency managers, the media, spotters, emergency planning/response officials, and so many others who work toward public safety and/or depend on critical weather information. Please call me or anyone at our office any time that you feel we can be of service. You can reach me at (615) 754-4633, extension 222.

Regards,
Larry

Additional repeaters added to MTEARS system

The National Weather Service's Middle Tennessee SKYWARN organization utilizes a specially designed UHF Repeater Link System for SKYWARN and Emergency Communications. The system became a necessity after the April 16, 1998 tornado outbreak across Middle Tennessee. The outbreak produced three tornadoes in Nashville, and a more destructive F5 tornado in Lawrence County. During the course of 18 hours, numerous amateur radio frequencies were utilized and monitored to pass critical weather information and emergency traffic, thus hundreds of real time reports were either delayed or not even forewarded to the National Weather Service. This created tremendous disorganization and chaos. Immediately after the event, an assessment of the existing SKYWARN communications system was made, and it was decided there must be a more organized system.

After much planning and coordination, the Middle Tennessee Emergency Amateur Radio Society (MTEARS) was formed, and implementation of a new system began in February, 1999. The goal of MTEARS was to establish a reliable repeater link system to provide direct communications to and from the National Weather Service, Emergency Management Agencies, and SKYWARN groups, and cover the entire National Weather Service (NWS) Nashville's 42 County Warning Area (CWA).

The system comprises numerous repeaters linked into the hub repeater located at the Tennessee Emergency Management Agency (TEMA) in downtown Nashville. The MTEARS Link System is strictly organized as a higher level of communications. This allows local spotter groups to communicate directly to "their" net control operator, then the net control operator and/or an appointed liaison passes the pertinent information directly to the NWS. This strict setup is more organized, and allows for less traffic on the link system. This keeps the system free for higher priority traffic such as tornadoes, injuries, and fatalities. During normal operations, the link system is available for anyone and everyone to enjoy and communicate across Middle Tennessee.

After six years, the MTEARS Link System covers over 90% percent of the CWA, with overlapping coverage. The latest repeaters to be added are at Columbia and Hinch Mountain (Cumberland County). The Columbia repeater provides hand-held coverage to those in and around Maury County. Hinch Mountain provides coverage across the Cumberland Plateau and as far as Knoxville. Over the next year, there are three proposed repeater links to complete the mission with 100 percent coverage of Nashville's CWA. The system has been utilized for numerous severe weather events, such as the Tornado Outbreak of November 10, 2002, Amateur Radio Emergency Service (ARES), emergency communications of the September 11, 2001 Terrorist Attacks, and an Earthquake Simulated Emergency Test on November 9, 2002, as well as other events such as Bike Rides and Airshows.

For more information about the MTEARS Repeater Link System or Middle Tennessee SKYWARN, please go to http://www.mtsh.org.

Michael Davis
Information Technology Officer

Middle Tennessee Flood Potential Outlook

Late Winter into Spring is flood season for Middle Tennessee. Through this period, soil temperatures are usually at their lowest and most vegetation is dormant. Rainfall, which would normally filter down into the soil, runs off over the ground and quickly reaches area rivers and streams during this time of year. These conditions, combined with an increase in migratory weather systems, increase the potential for flooding.

Across Middle Tennessee, rainfall during December and January was slightly below normal. Through the first 10 days in February, rainfall was well above normal. On the 5th of February, between 4 and 6 inches of rain fell across a large part of Middle Tennessee. A few areas received more than 7 inches. The heavy rain produced widespread flooding and left soil moisture content well above normal. Flooding has since ended. However, area rivers and streams remain above normal levels.

The outlook through the end of February indicates the possibility of above normal precipitation. The long range outlook for March, April, and May indicates normal precipitation through the period.

At this time across Middle Tennessee, soils are nearly saturated, river and stream levels are higher than normal, and several weather systems are forecast to affect the area during the next 7-day period. Therefore, the potential for flooding is higher than normal.

For the latest river forecasts and current river information, visit our web page at http://www.srh.weather.gov/ohx. Under "Current Conditions," click "Rivers & Lakes AHPS."

Michael Murphy
Service Hydrologist

Strangest of the Strange

The following anecdote was taken from Symons's Monthly Meteorological Magazine, Volume 4, pages 123-124, published in 1869.

Out in Cheatham County about noon on Wednesday -- a remarkably hot day -- on the farm of Ed Sharp, five miles from Ashland, a sort of whirlwind came along over the neighboring woods, taking up small branches and leaves of trees and burning them in a sort of flaming cylinder that traveled at the rate of about five miles an hour, developing size as it traveled. It passed directly over the spot where a team of horses was feeding and singed their manes and tails up to the roots. It then swept toward the house, taking a stack of hay in its course. It seemed to increase in heat as it went, and by the time it reached the house it immediately fired the shingles from end to end of the building, so that in ten minutes the whole dwelling was wrapped in flames. The tall column of traveling caloric then continued its course over a wheat field that had been recently cradled, setting fire to all the stacks that happend to be in its course. Passing from the field, its path lay over a stretch of woods which reached the river. The green leaves on the trees were crisped to a cinder for a breadth of twenty yards in a straight line to the Cumberland. When the "pillar of fire" reached the water, it suddenly changed its course down the river, raising a column of steam which went up to the clouds for about half a mile, when it finally died out. Not less than 200 people this strangest of strange phenomena, and all of them tell substantially the same story about it. The farmer, Sharp, was left houseless by the devouring element, and his two horses were so affected that no good is expected to be got out of them in future. Several withered trees in the woods through which it passed were set on fire, and continue burning still.

Photograph of the Quarter

This quarter's best photograph was taken by NWS employee Bobby Boyd looking across Old Hickory Lake just a few hundred yards from the weather office.

If you have a unique weather photograph you would like to share, please either e-mail it to the editor, or send it to: National Weather Service, 500 Weather Station Rd., Old Hickory, TN 37138, Attn: Mark A. Rose. If you mail your photograph(s), I will scan them and mail them right back.