In my own front yard! At 4:49 PM CDT the National Weather Service has issued a severe thunderstorm warning for davidson county. Here is the text…

* AT 445 PM CDT…NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING FROM 15 MILES WEST OF ASHLAND CITY TO BURNS…MOVING EAST AT 40 MPH.

So, I decided that since I would be unable to go mobile with the storm, I would make the best of things. I grabbed a tripod, my anemometer, and a zip tie and marched across the street to Julia Green Elementary to set up the anemometer in the best position to measure windspeed. After I got it set up, I grabbed some rocks to anchor the tripod, and then ran back to the house to grab the camera. I had decided that I would stay and observe the updraft side until the core was near hitting and then I would run back home. May I say that that was the most photogenic storm I have seen to date.

The updraft created a weird coronal phenomenon, and you can see it in the gallery below. The other incredible thing, I experience a true and genuine updraft and it scared me pretty bad… warm and almost hot air started rushing towards the thunderstorm, and the clouds above were extremely turbulent. Some clouds began to weakly rotate, while there was some scud also lifting into the base. Just barely, but enough to keep me on edge and repeating, “I have GOT to get out of here…” It was quite the experience, and one of my favorite storms to date.

I was also able to collect some cool data with the anemometer. It recorded windspeed, barometric pressure, dewpoint, humidity, heat index… you name it, it measured it! There were some very cool things it observed… for example, the temperature rose as the thunderstorm drew near, and dropped 25 degrees once the downdraft hit. Max temperature was 101.8, and min was 75 Fahrenheit. The humidity also greatly increased after the downdraft passed over. Minimum Barometric pressure as the updraft passed was 29.89 inHg, with a max of 29.97. Enough of the data, you all just want the photos =) Have at it!

PLEASE leave your comments below!

[View with PicLens]

In the larger news, there was a massive tornado that struck Yazoo City, Mississippi on April 24th. The tornado at its widest point was 1.75 miles, and was on the ground for about 200 miles! This was the strongest and longest living storm of the day, and it caused 10 fatalities in Yazoo. The tornado was rated EF-4, with winds estimated to be at 170 MPH. It caused major damage in Yazoo, practically wiping out half of the city. Storm chaser Reed Timmer of TornadoVideos.Net got incredible footage of the moster, of which you can see here.

On this day there were a total of 54 tornado reports across several states, and 3 different tornadoes occurred here in Middle Tennessee. The largest of which was rated EF-1, with estimated 100 MPH winds within the tornado. The tornado damage path is 13 miles long, and was 300 yards wide at the widest. More information about this tornado and others in Tennessee can be seen here.

I intercepted the same storm that produced this tornado when it hit Dickson, which was a little after the tornado had dissipated. I did not encounter a tornado when it passed to my north, but I did get some great video of the dying supercell’s outflow/shelf cloud. This was my first intercept as a mobile spotter, and I was quite please with my positioning and timing on this storm. Maybe I will have another opportunity as this weekend may yield yet another severe weather system, which I will discuss in a later post. When watching this video of the April 24th supercell, please be kind to the fact that I am a novice storm spotter and was pretty excited. I don’t expect you to watch the whole thing, but please leave your comments below if you liked it!

10 minutes earlier the same day, a SKYWARN storm spotter reported a funnel cloud 6 miles northeast of Ashland City. Here is the link to the storm reports for Friday

http://www.srh.noaa.gov/ohx/lsr/stormreports.php?yr=2009&mo=10&dy=10

Below is the National Weather Service report on this tornado. You can see it at http://www.srh.noaa.gov/productview.php?pil=OHXPNSOHX

...NWS CONFIRMS EF-1 TORNADO DAMAGE ALONG DAVIDSON/ROBERTSON COUNTY
LINE...

THE TORNADO TOUCHED DOWN ON A FARM NEAR THE INTERSECTION OF GREER
ROAD AND DICKENS LANE IN ROBERTSON COUNTY. IT OCCURRED ON FRIDAY,
OCTOBER 9TH, TOUCHING DOWN AT APPROXIMATELY 1225 PM CDT. THE TORNADO
THEN CONTINUED ON A 1.8 MILE PATH EAST-NORTHEAST INTO DAVIDSON COUNTY.
THE LAST EVIDENCE OF DAMAGE WAS AT A RESIDENCE ALONG BAKER ROAD.

AN OLD BARN WAS DESTROYED NEAR THE BEGINNING OF THE DAMAGE PATH IN
ROBERTSON COUNTY.  THE MOST SIGNIFICANT DAMAGE WAS RIGHT ALONG GREER
ROAD...WHICH MARKS THE BORDER BETWEEN ROBERTSON AND DAVIDSON
COUNTIES.  ON THE ROBERTSON COUNTY SIDE OF THE ROAD DOZENS OF
HARDWOOD TREES WERE SNAPPED OR UPROOTED AND A RESIDENCE AND
OUTBUILDING RECEIVED ROOF DAMAGE. ON THE DAVIDSON COUNTY SIDE
SEVERAL TRAILERS WERE DAMAGED...INCLUDING ONE WHICH WAS PUSHED
APPROXIMATELY 15 FEET OFF IT`S FOUNDATION.

THIS WAS THE FIRST RECORDED OCTOBER TORNADO IN EITHER ROBERTSON OR
DAVIDSON COUNTIES.

$$

SUMMARY...

STRENGTH...EF-1
WIND SPEED ESTIMATE...90 MPH
PATH LENGTH...1.82 MILES
TOUCHDOWN LAT/LON...36.3725   -86.7983
WIDTH...100 YARDS
TOUCHDOWN TIME...1225 PM CDT  (BASED ON RADAR)

TOM JOHNSTONE
NATIONAL WEATHER SERVICE NASHVILLE

As you can imagine, I was pretty upset about not being in town to see this. It would have been a great opportunity to go spotting for the National Weather service. One day…

I am sorry there was no forecast on this day. I was taking the 4 hour tour of D.C. then, and had no time for the computer afterwards. Honestly, it caught me by surprise when I saw Nashville under a Tornado Watch! I will pick the forecasts back up when I am back in town, but until then posting may be sparse. Enjoy the rest of Fall Break!

Monday September 7, an Outflow Boundary, sometimes know as a Gust Front, formed north of Nashville. See image above.

An outflow boundary, or gust front, is a rush of cool/cold air from a thunderstorm. Gust fronts can last over 24 hours, and travel hundreds of miles before dissipating. Gust fronts can be seen on radar as a slight crescent moving on the map. Outflow boundaries of gust fronts can kill off the supply of warm, moist air to a thunderstorm, but they can also rapidly shoot warm air up into the atmosphere creating new, stronger thunderstorms. Monday was such a day, and had surprising results.

I was able to document the complete lifecycle of a thunderstorm created by a gust front, and it went from severe, to dropping 70+ DBz hail, to producing a mesocyclone!

At 3:30, i noticed the gust front on radar. At 6:00 PM, the storm of interest started to initiate. The storm became severe warned at 6:13 PM. 6:25 PM I began to notice some weak, low level rotation in the storm, some miles north of McMinnville. 6:27 PM, Base Reflectivity Tilt 3 shows a pocket of 70 DBz hail. At 6:30, the rotation becomes very noticeable. At 6:40, GRlevel3 decides on it, and issues a low level Mesocyclone icon right on the center of rotation! At 6:45, the National Weather Service issues a tornado warning for areas north of McMinnville, through McMinnville. At 6:47, strongest rotation appears on Base Velocity and Storm Relative Velocity. When the storm was slightly south of McMinnville, residents report a funnel cloud.

All of this from ONE outflow boundary!

The images below are in order from left to right, in the complete life cycle.