What would you say is the most important breakthrough in the tornado warning process? You could go back to the nineteenth century and say the telegraph, which made advance warnings possible. It could be Fawbush and Miller’s excellent, albeit lucky, tornado forecast at Tinker AFB in 1948. It could be the discovery of the hook echo on conventional radar. It might be NOAA Weatheradio, which came to the forefront after the 1965 Palm Sunday outbreak. It could be the proliferation of local television stations arming and equipping their meteorologists with the latest in radar and warning technology.

To me, the most important breakthrough in the tornado warning process has been the use of Doppler Radar. The technology has really fulfilled its promise or greatly increased warning lead times. Some would argue that there has been a higher false alarm ratio, but I think the trade off has certainly been worth it. Thirty two years ago on May 24, 1973, that promise was just coming to the forefront as a team of scientists from the National Severe Storms Laboratory prepared to attempt to intercept a tornado using their powerful experimental Doppler radar. Conditions seemed to be right for the formation of tornadoes, and a team of scientists including Chuck Doswell, Joe Golden and Don Burgess prepared to try and capture a tornado on radar and in the field with an armada of instruments, video and still cameras. The scientists at NSSL had been studying the use of Doppler Radar in tornado prediction since the sixties.

The tiny farming community of Union City, OK will forever be known as the place that they found their quarry. As the F4 tornado tore right through the center of town on that Thursday, it was the most intently studied tornado until that time. Research of the radar data from the storm would lead to discovery of the TVS – or Tornado Vortex Signature. The presence of a TVS on Doppler radar data is a very strong indication of tornadic potential in a severe thunderstorm. Researchers also discovered the telltale signature of a mesocyclone, or rotating thunderstorm, an important precursor to tornado formation.

Check out the VIL levels in this storm over western Tennessee.

Tennessee Hailer

This image is from the Memphis radar. The VIL is at the top of the scale. The actual reading 72 dBz. This indicates very large hail. The radar algorithm indicates that hail up to 3 inches is possible.

Severe thunderstorm warnings are in effect for this storm in Henderson and Decatur counties.

At 9:52 p.m. quarter sized hail was reported in Wildersville in Henderson County, Tennessee. This storm will eventually affect the Tennessee Valley of North Alabama.

Additional storms are back upstream over Southeast Missouri. Atmospheric conditions may allow these storms to remain strong for some time overnight although they should gradually weaken.

Two severe thunderstorm watches are in effect for North Alabama. The southernmost county is Marshall. Activity should stay north of the Birmingham and Anniston areas. Northeastern sections will continue to be affected for the next few hours.

Thunderstorms are slowly weakening over North Alabama this evening.

They are mostly over Jackson and extreme northern DeKlab County a 9:45 p.m. An large area of light to moderate rain covers much of Madison, Morgan and Marhsall Counties. A fairly good storm is over northern Madison County.

All of the activity is moving east southeast at nearly 50 mph.

Another strong storm is over western Tennessee to the east of Jackson is moving southeast and may affect the Tennessee Valley later tonight if it holds together.

Two severe thunderstorm watches cover the Tennessee Valley until the wee hours of the morning.

The severe thunderstorm watch for Mississippi, Tennessee and extreme Northwest Alabama goes until 1 a.m. CDT.

The severe thunderstorm watch that was in effect for northeast Alabama has been allowed to expire but another one is being issued in its place. It will cover the rest of the Tennessee Valley. It will be valid until 2 a.m. CDT It covers DeKalb, jackson, Limestone, Madison and Marshall Counties.

The NWS Huntsville has just issued severe thunderstorm warnings for Franklin and Lincoln Counties in southern Tennessee. These storms are part of a line of strong storms over southern and eastern Tennessee that extends into Northwest Georgia and western North Carolina.

The activity over southern Tennessee will move into the Tennessee Valley of North Alabama over the next few hours. The severe storm over Franklin County TN will move into Alabama's Jackson County by 8:45.

The storms have the potential to produce large hail and damaging winds.

They should stay north of the Birmingham, Tuscaloosa and Anniston areas.

The Storm Prediction Center has included Lauderdale County in the northwestern corner of Alabama in a new severe thunderstorm watch that goes until 1 a.m. CDT.

Thunderstorm activity is increasing over western Tennessee in association with a slow moving cold front. The activity may tend to increase during the evening hours as an upper level trough approaches from the west.

Go out side and look to the northeast and see an impressive thunderstorm over northwestern Georgia. This storm is 150 miles northeast of Birmingham and is clearly visible. The top of the storm is nearly 50,000 feet in the atmosphere.

It is in the other severe thunderstorm watch that is in effect until 8 p.m. CDT for five counties in Northeast Alabama.

The Saturday map discussion video is on the server at:

http://beta.abc3340.com/weather/video.hrb

May has certainly been a great month so far with temperatures much below seasonal values for at least the last couple of weeks. But heat is returning today as afternoon high temperatures are expected to flirt with the 90 degree mark. This won't be our first 90-degree readings as we saw those back in mid-April.

A frontal boundary remains positioned just to the north of the Birmingham area generally across Tennessee. If you saw any radar yesterday, you saw showers across Tennessee moving eastward. That pattern is expected to remain with us into the first of the week. While we expect showers to remain to our north, it is going to be close so a stray shower or thunderstorm can't be completely eliminated from the forecast for Central Alabama.

The front moseys southward but washes out as it does leaving a lingering boundary that could see the development of a shower or thundershower into the first of the week. No major change in air mass so the warm weather will stay with us.

A strong short wave in the northwesterly flow will bring better changes for rain in the form of showers and storms toward the latter part of the week - the Thursday and into Friday time frame. That disturbance will weaken and begin pulling off to the northeast on Saturday so we should see improving weather during the weekend.

James has commented about summer weather patterns, and I have to echo some of his thoughts. I hate the monotony that we see with a summertime weather pattern. There is very little skill if any in being able to tell exactly where showers will form, so our forecasts change little from day-to-day. Oh, well, one of the downsides of the weather biz!!

Got a full plate of activites today. Off to Do-Dah-Day this morning to judge the parade. They didn't tell me when I agreed to be a judge that once you are appointed a judge you remain a judge for LIFE! It's fun to see all the animals and the creativity that goes with those entering the parade. Then I'm off in the Storm Chaser to Hokes Bluff for their community awareness day. Hope you get a chance to say hello at one of these events today.

Hope you have a great weekend. Be sure to spend time with your family.

-Brian-