THIS POST WILL BE UPDATED AS NEW INFORMATION COMES IN.

EDIT 2: The flash flood warning has expired, but has been replaced with an Area Flood Advisory is still in effect as some roads are still flooded.

THE NATIONAL WEATHER SERVICE IN NASHVILLE HAS ISSUED AN

* URBAN AND SMALL STREAM FLOOD ADVISORY FOR…

EASTERN WILLIAMSON COUNTY IN MIDDLE TENNESSEE… THIS INCLUDES THE CITIES OF FRANKLIN…BRENTWOOD…

* UNTIL 730 PM CDT

* AT 527 PM CDT

…NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED RAINFALL HAD ENDED ACROSS THE AREA. HOWEVER…LOCAL LAW ENFORCEMENT OFFICIALS AND NATIONAL WEATHER SERVICE EMPLOYEES REPORTED SEVERAL ROADWAYS REMAIN FLOODED UNDER SEVERAL FEET OF WATER ACROSS WILLIAMSON COUNTY…INCLUDING AREAS AROUND FRANKLIN…BRENTWOOD…AND COOL SPRINGS MALL.

RADAR ESTIMATES INDICATE 2 TO 4 INCHES OF RAIN FELL ACROSS PORTIONS OF FRANKLIN AND BRENTWOOD THIS AFTERNOON. FLOODING WILL SLOWLY SUBSIDE ACROSS THE AREA OVER THE NEXT COUPLE OF HOURS.

PRECAUTIONARY/PREPAREDNESS ACTIONS…

MOST FLOOD DEATHS OCCUR IN AUTOMOBILES. NEVER DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE ROADWAY. FLOOD WATERS ARE USUALLY DEEPER THAN THEY APPEAR. JUST ONE FOOT OF FLOWING WATER IS POWERFUL ENOUGH TO SWEEP VEHICLES OFF THE ROAD. WHEN ENCOUNTERING FLOODED ROADS MAKE THE SMART CHOICE…TURN AROUND…DONT DROWN.

EDIT: Water should be receding. Updates will cease unless any other important information comes about. Again, for the 3rd time, do not drive into the water! Vehicle flood deaths outnumber tornado deaths!

Currently, a lot of the Cool Springs area is under water, where many busy roads have become impassable. Several cars are stranded and water rescues are under way. Currently, the National Weather Service has a Flash Flood Warning for ALL large portions of Williamson county. Doppler radar estimates that over 3.5 to 3.7 inches fell over the Franklin/Cool Springs area over 2 hours! Roads that are flooded include Cool Springs blvd, Baker’s Bridge, and Duke Drive. The image is a picture that has been circulating twitter – credit unknown. Please DO NOT ATTEMPT TO DRIVE THROUGH THE WATER!  As little as 2 feet of water will wash a car away, so TURN AROUND AND DON’T DROWN!

The rain has subsided for now, but expect more showers and thunderstorms tomorrow morning and afternoon. There is a risk for severe thunderstorms tomorrow, and storms will mainly be in the morning and early afternoon, with scattered storms in the afternoon and evening. These storms will also have the potential for torrential downpours, so isolated flash flooding *might* be possible.

EDIT: THE RADAR IMAGE BELOW IS THE RADAR ESTIMATED RAINFALL, PEAKING AT 3.74 INCHES.

The National Weather Service in Nashville has now issued a flash flood warning for Cumberland and Putnam counties, TN. A stationary thunderstorm has dropped over 3.5 inches of rain over the area, and flash flooding can be expected. This storm is currently over I-40 in between Cookeville and Crossville.

* AT 451 PM CDT…NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED FLASH FLOODING FROM A THUNDERSTORM OVER THE WARNED AREA. RADAR ESTIMATED RAINFALL RATES UP TO 4 INCHES PER HOUR ACROSS THE WARNED AREA.

* LOCATIONS IN THE WARNING INCLUDE BUT ARE NOT LIMITED TO MONTEREY AND MAYLAND. PRECAUTIONARY/PREPAREDNESS ACTIONS…

DO NOT DRIVE YOUR VEHICLE INTO AREAS WHERE THE WATER COVERS THE ROADWAY. THE WATER DEPTH MAY BE TOO GREAT TO ALLOW YOUR CAR TO CROSS SAFELY. MOVE TO HIGHER GROUND.

Flash flooding in Cool Springs will start to go down with time as water begins to run off. However, crossing deep water is still dangerous, as 2-3 feet of water is still present in some areas. Do not attempt to cross a flooded road!

In the next couple of days, I will be making a post discussing certain events that will take place over the next few weeks and are major in the continued development of Tempest Storm Chasing. Feel free to check back for the news!

EF-1 Tornado Confirmed in Dickson County…Straight Line Winds Caused Damage Around Montgomery Bell Park and White Bluff

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE NASHVILLE TN
558 PM CDT TUE APR 5 2011

…EF-1 TORNADO CONFIRMED IN DICKSON COUNTY TENNESSEE…
…STRAIGHT LINE WINDS CAUSED DAMAGE AROUND MONTGOMERY BELL PARK AND
WHITE BLUFF…

DATE…APRIL 4, 2011
ESTIMATED TIME (RADAR)…1333 – 1341 CDT
MAXIMUM EF-SCALE RATING…EF1
ESTIMATED MAXIMUM WIND SPEED…110 MPH
MAXIMUM PATH WIDTH…150 YARDS
PATH LENGTH…7.3 MILES
BEGINNING LAT/LON…36.0952 N / 87.5390 W
ENDING LAT/LON…36.0845 N / 87.4099 W
FATALITIES…0
INJURIES…0

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS
STORM DATA.

…SUMMARY…
A NATIONAL WEATHER SERVICE DAMAGE ASSESSMENT TEAM HAS CONFIRMED A
TORNADO TOUCHED DOWN NEAR TENNESSEE CITY IN DICKSON COUNTY ON
APRIL 4, 2011.

INITIAL DAMAGE WAS NOTED ALONG HWY 70 APPROXIMATELY 1 MILE WEST OF
TENNESSEE CITY IN WESTERN DICKSON COUNTY. DAMAGE WAS NEARLY
CONTINUOUS ALONG A 7.3 MILE TRACK INTO THE WEST SIDE OF THE CITY OF
DISCKSON. THE LAST EVIDENCE OF DAMAGE WAS JUST WEST OF DICKSON
LAKE. THE MAXIMUM PATH WIDTH OF THE TORNADO WAS NEARLY 150 YARDS.

HUNDREDS OF HARDWOOD TREES WERE SNAPPED AND UPROOTED ALONG THE
DAMAGE PATH. SEVERAL STRUCTURES EXPERIENCED SIGNIFICANT ROOF DAMAGE
INCLUDING A FIRE HALL IN TENNESSEE CITY. SEVERAL OUTBUILDINGS AND
BARNS WERE ALSO HEAVILY DAMAGED.

AN ADDITIONAL SURVEY NEAR MONTGOMERY BELL PARK TO WHITE BLUFF
REVEALED STRAIGHT LINE WIND DAMAGE. SEVERAL HOMES SUFFERED MINOR
ROOF DAMAGE…DOZENS OF TREES WERE SNAPPED AND UPROOTED…AND A
COUPLE OUTBUILDINGS WERE TOPPLED. MAXIMUM WIND SPEEDS WERE
ESTIMATED TO BE NEAR 90 MPH.

THE NATIONAL WEATHER SERVICE WOULD LIKE TO THANK THE DICKSON
COUNTY EMERGENCY MANAGEMENT AGENCY FOR THEIR ASSISTANCE WITH THESE
SURVEYS.

THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT
WEATHER.GOV/OHX.

FOR REFERENCE…THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES INTO
THE FOLLOWING CATEGORIES:

EF0…WIND SPEEDS 65 TO 85 MPH.
EF1…WIND SPEEDS 86 TO 110 MPH.
EF2…WIND SPEEDS 111 TO 135 MPH.
EF3…WIND SPEEDS 136 TO 165 MPH.
EF4…WIND SPEEDS 166 TO 200 MPH.
EF5…WIND SPEEDS GREATER THAN 200 MPH.

EF-1 Tornado Confirmed in Waverly

PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE NASHVILLE TN
545 PM CDT TUE APR 5 2011

...EF-1 TORNADO CONFIRMED IN WAVERLY TENNESSEE / HUMPHREYS COUNTY...

DATE...APRIL 4, 2011
ESTIMATED TIME (RADAR)...1319 - 1322 CDT
MAXIMUM EF-SCALE RATING...EF1
ESTIMATED MAXIMUM WIND SPEED...100 MPH
MAXIMUM PATH WIDTH...75 YARDS
PATH LENGTH...2.9 MILES
BEGINNING LAT/LON...36.0841 N / 87.8069 W
ENDING LAT/LON...36.0850 N / 87.7550 W
FATALITIES...0
INJURIES...0

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS
STORM DATA.

...SUMMARY...
A NATIONAL WEATHER SERVICE DAMAGE ASSESSMENT TEAM HAS CONFIRMED A
TORNADO TOUCHED DOWN NEAR WAVERLY TENNESSEE IN HUMPHREYS COUNTY ON
APRIL 4, 2011.

INITIAL DAMAGE WAS NOTED JUST WEST OF WAVERLY NEAR THE INTERSECTION
OF BOWEN HILLS DRIVE AND HWY 70.  THE DAMAGE CONTINUED DIRECTLY
THROUGH DOWNTOWN WAVERLY FOR APPROXIMATELY 2.9 MILES.  THE LAST
EVIDENCE OF DAMAGE WAS NEAR THE INTERSECTION OF FAIRFIELD DRIVE AND
HWY 70.  THE DAMAGE PATH WAS VERY NARROW...WITH A MAXIMUM WIDTH OF
ONLY 75 YARDS.

IN ADDITION TO DOZENS OF SNAPPED AND UPROOTED TREES...SEVERAL
BUSINESSES IN WAVERLY SUFFERED SIGNIFICANT ROOF DAMAGE.  SIGNS AND
OVERHANGS WERE ALSO TORN OFF BY THE WINDS...AND THERE WERE SEVERAL
HOMES AND VEHICLES CRUSHED BY FALLING TREES.

AN ADDITIONAL SURVEY NEAR MCEWEN IN EASTERN HUMPHREYS COUNTY
REVEALED STRAIGHT LINE WIND DAMAGE.  A CARPORT WAS
DESTROYED...SEVERAL HOMES SUFFERED MINOR ROOF DAMAGE...AND DOZENS OF
TREES WERE SNAPPED AND UPROOTED.  MAXIMUM WIND SPEEDS WERE ESTIMATED
TO BE 80 TO 90 MPH.

THE NATIONAL WEATHER SERVICE WOULD LIKE TO THANK THE HUMPHREYS
COUNTY EMERGENCY MANAGEMENT AGENCY FOR THEIR ASSISTANCE WITH THESE
SURVEYS.

THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT
WEATHER.GOV/OHX.

FOR REFERENCE...THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES INTO
THE FOLLOWING CATEGORIES:

EF0...WIND SPEEDS 65 TO 85 MPH.
EF1...WIND SPEEDS 86 TO 110 MPH.
EF2...WIND SPEEDS 111 TO 135 MPH.
EF3...WIND SPEEDS 136 TO 165 MPH.
EF4...WIND SPEEDS 166 TO 200 MPH.
EF5...WIND SPEEDS GREATER THAN 200 MPH.

EF-1 Tornado Confirmed SE Davidson and NW Rutherford

000
NOUS44 KOHX 052317 CCA
PNSOHX
TNZ005>011-022>034-056>066-075-077>080-093>095-060230-

PUBLIC INFORMATION STATEMENT…CORRECTION
NATIONAL WEATHER SERVICE NASHVILLE TN
321 PM CDT TUE APR 5 2011

…TORNADO CONFIRMED IN EXTREME SOUTHERN DAVIDSON COUNTY AND
NORTHWEST RUTHERFORD COUNTY TENNESSEE…

LOCATION…SOUTH OF CANE RIDGE PARK IN DAVIDSON COUNTY TO NEAR
SMYRNA IN RUTHERFORD COUNTY
DATE…APRIL 4, 2011
ESTIMATED TIME…2:20 – 2:24 PM CDT
MAXIMUM EF-SCALE RATING…EF1
ESTIMATED MAXIMUM WIND SPEED…104 MPH
MAXIMUM PATH WIDTH…100 YARDS
PATH LENGTH…4.19 MILES
BEGINNING LAT/LON…35.98 N / 86.65 W
ENDING LAT/LON…35.98 N / 86.57 W
FATALITIES…0
INJURIES…0

* THE INFORMATION IN THIS STATEMENT IS PRELIMINARY AND SUBJECT TO
CHANGE PENDING FINAL REVIEW OF THE EVENT(S) AND PUBLICATION IN NWS
STORM DATA.

…SUMMARY…
THE NATIONAL WEATHER SERVICE IN NASHVILLE TN HAS CONFIRMED A TORNADO
IN EXTREME SOUTHERN DAVIDSON COUNTY AND NORTHWEST RUTHERFORD
COUNTY IN TENNESSEE ON APRIL 4, 2011.

THE EF1 TORNADO BEGAN ALONG THE DAVIDSON AND WILLIAMSON COUNTY
LINE…ALONG KIDD ROAD. THE DAMAGE PATH EXTENDED EAST ACROSS
BATTLE ROAD…WALDRON ROAD…ALONG BLAIR ROAD…AND ENDING NEAR
INTERSTATE 24 AND SAM RIDLEY PARKWAY. THE DAMAGE PATH RANGED FROM
50 TO 100 YARDS WIDE. DAMAGE WAS VERY CONSISTENT ALONG THE
PATH…WHICH WAS JUST OVER 4 MILES LONG.

THE DEBRIS PATTERN SHOWED CLEAR CONVERGENT PATTERNS…AND
EYEWITNESS ACCOUNTS SUPPORT THE DETERMINATION THAT A TORNADO
CAUSED THE DAMAGE. NUMEROUS POWER POLES WERE SNAPPED. HUNDREDS OF
TREES WERE SNAPPED OR UPROOTED. SOME HAD LARGE ROOT SYSTEMS. SOME
SMALL STORAGE BUILDINGS WERE DESTROYED. NUMEROUS HOMES HAD ROOF
AND SIDING DAMAGE. SEVERAL FENCES WERE BLOWN DOWN. DEBRIS WAS
SCATTERED HUNDREDS OF YARDS. A TRACTOR TRAILER WAS BLOWN OVER ON
INTERSTATE 24. SEVERAL CARGO TRAILERS WERE OVERTURNED BY I 24.

THANKS TO DAVIDSON COUNTY AND RUTHERFORD COUNTY EMERGENCY
MANAGEMENT FOR VERY HELPFUL ASSISTANCE WITH THIS SURVEY.

THIS INFORMATION CAN ALSO BE FOUND ON OUR WEBSITE AT
WEATHER.GOV/OHX.

FOR REFERENCE…THE ENHANCED FUJITA SCALE CLASSIFIES TORNADOES INTO
THE FOLLOWING CATEGORIES:

EF0…WIND SPEEDS 65 TO 85 MPH.
EF1…WIND SPEEDS 86 TO 110 MPH.
EF2…WIND SPEEDS 111 TO 135 MPH.
EF3…WIND SPEEDS 136 TO 165 MPH.
EF4…WIND SPEEDS 166 TO 200 MPH.
EF5…WIND SPEEDS GREATER THAN 200 MPH.

Monday, July 26th 2010 a severe thunderstorm developed in northern Davidson county. Here is the copied NWS Survey and report. Also, two radar images of the storm before it died. I will also add that I was not chasing this storm, the storm was certainly chasing me. I was at home with my family keeping an eye on thing and ready to head for cover if need be. However, it was torturous! I don’t want to ever let an opportunity like that slip my hand again… I was so close to it and could have spotted it. However, sometimes it is smart to say no, so I hope this was one of those situations…

PUBLIC INFORMATION STATEMENT

NATIONAL WEATHER SERVICE NASHVILLE TN

325 PM CDT TUE JUL 27 2010




...NWS CONFIRMS EF-1 TORNADO IN NORTHERN DAVIDSON COUNTY...




NATIONAL WEATHER SERVICE AND METRO NASHVILLE OEM OFFICIALS SURVEYED

DAMAGE IN NORTHERN DAVIDSON COUNTY THIS MORNING.  THE DAMAGE WAS

FROM STORMS WHICH AFFECTED THE AREA MONDAY EVENING.




MOST OF THE SURVEYED DAMAGE...INCLUDING TRAIL HOLLOW LANE JUST WEST

OF I-24...AND COMMUNITIES ALONG BRICK CHURCH PIKE FROM NORTHBROOK

DRIVE SOUTH TO BRILEY PARKWAY...WAS FROM MICROBURST WINDS.  A

SEMI-TRAILER WAS BLOWN OVER...DOZENS OF TREES WERE SNAPPED AND

UPROOTED...AND SEVERAL ROOFS SUFFERED MINOR DAMAGE.  MAXIMUM WINDS

IN THESE AREAS WAS AROUND 80 MPH.




FURTHER NORTH AREAS ALONG WESTCHESTER DRIVE EXPERIENCED MUCH MORE

SIGNIFICANT DAMAGE.  APPROXIMATELY 12 BRICK HOMES SUFFERED HEAVY

ROOF DAMAGE...INCLUDING ONE WHICH HAD A LARGE SECTION OF THE ROOF

REMOVED.  TWO BUILDINGS WERE IMPALED BY TWO BY FOURS...AND A COUPLE

DOZEN WINDOWS WERE BLOWN OUT.  THE DAMAGE PATTERN IN THIS AREA WAS

CHARACTERIZED BY CONVERGENCE AND OBVIOUS ROTATION CONSISTENT WITH A

TORNADO.  DAMAGE IN THE HIGHEST END OF THE EF-1 RANGE...105 TO 110

MPH...OCCURRED.

$$




SUMMARY...TIMES BASED ON RADAR




WIND SPEED ESTIMATE...105-110 MPH

EF SCALE...EF-1

DAMAGE PATH LENGTH...1/2 MILE

DAMAGE WIDTH...50 YDS

START POINT...36.25343 -86.7778

END POINT...36.255446 -86.771126

BEGIN TIME...705 PM 7/26/2010

END TIME...706 PM 7/26/2010










THOMAS JOHNSTONE

MICHAEL E. DAVIS

NATIONAL WEATHER SERVICE NASHVILLE

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!

[Show as slideshow]

[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.