5/15/2013 – DFW Area Tornado Outbreak (Granbury and Cleburne Tornadoes)

- At least 6 dead in Hood County -
- Preliminary Ratings Per NWS Fort Worth – Granbury – EF-4; Cleburne EF-3-

Aerial damage photo from the area hardest hit by the Granbury tornado. Photo via National Weather Service – Fort Worth Facebook Page – https://www.facebook.com/US.NationalWeatherService.FortWorth.gov

On the evening of May 15th, strong to violent tornadoes went through portions of Hood County and Johnson County, TX.  Six people were killed in the Granbury area from this storm, and multiple tornadoes were produced as the storm cell tracked through the region.   The maps below were created from radar images, and depict the rotation paths of the tornadoes as they impacted areas near Granbury and Cleburne, TX.  As you can see from the images, the storms progressed from WNW to ESE (you can look at the timestamps), however the tornadoes tracked from south to north while they were on the ground.  I’m sure this scenario has occurred before, but the differences between the storm motion and the path of the tornadoes themselves could be lending to some of the initial confusion in reporting areas impacted.

Granbury Tornado (Hood County, TX) – As of the morning after the storm, authorities in Hood County were reporting -6- fatalities from the storm, with nearly 100 injuries.  Based on radar observations, correlated to scanner reports of streets impacted, below is some preliminary information on primary impact area.  The hardest hit area was located south and east of Granbury, TX on the north side of Lake Granbury.  Some areas / roads in the area most impacted include the area near Rancho Brazos Estates / Tumbleweed Lane (http://goo.gl/maps/HRxfL - Google Maps Link).  There were a number of tweets reporting structural damage, homes collapsed.  Looking more closely at some of the buildings in this area show that many homes are mobile homes, likely contributing to the high casualty numbers.

NWS Dual-Pol Radar image showing Correlation Coefficient (CC) and the Tornado Debris Signature ~810pm CT.  Low values of CC in areas with high rotation (likely tornado areas) are consistent w/ debris being produced by a tornado on the ground.  This location correlates with law enforcement and social media reports describing the hardest hit areas. (click for larger image)

Rotation Path for the 5/15/13 Tornado – Hood County, TX (Aerial – Click for larger image)

Bing Maps imagery showing the area hardest hit by the Granbury tornado. Note the concentration of mobile homes in the center of the image. Many homes were “wiped off their foundation”. Because of their vulnerability to winds, my guess is that these homes were some of the hardest hit in the area. (Click for larger image)

Rotation Path for the 5/15/13 Tornado – Hood County, TX (Street Map – Click for larger image)

Later in the evening, another large tornado (reported by spotters to the NWS as a mile-wide tornado) impacted areas South and West of Cleburne, TX.  One of my best friends from College lives there, so I’m quite familiar with that part of town.  There is a lot of new residential development in that part of town – single story homes, most without basements, however the relative age of the homes hopefully means that they’re built to withstand stronger winds.  The roofs in most of this area are hip roofs which hold up better to stronger winds.  Here’s a link to Google Maps to Southwestern parts of Cleburne (http://goo.gl/maps/JfMvA)  I’ll update more as I hear more from the Cleburne area, but the radar images did not look good.  Thankfully though, the strongest radar images occurred outside of town.  Below are the timestamps (UTC) showing the rotation path through the Cleburne area.

Picture of mile wide tornado (backlit from lightning) near Rio Vista, TX – via Fox4 Weather Facebook Page

Rotation Path for the 5/15/13 Tornado – Cleburne, TX (Aerial – click for larger image)

Rotation Path for the 5/15/13 Tornado – Cleburne, TX (Street Map – click for larger image)

Damage to houses along Lakecrest Court in Cleburne (image from WFAA). For more pictures from WFAA, visit http://www.wfaa.com/home/HD-chopper-8-gets-first-look-of-tornado-damage-in-Cleburne-207684041.html?gallery=y&c=y.  Note: Lakecrest Court is located almost exactly at the 0215 UTC location dot on the previous map, depicting the approximate path of the tornado.

Mayor: “We Were Blessed” – No Fatalities as Tornado with Winds Up to 170mph Tears Through the Deep South

Damage to Music Building at University of Southern Mississippi (WDAM)

UPDATE: 536pm CT – The National Weather Service office in Mobile, AL has released the preliminary storm survey results confirming two tornado tracks in their forecast area produced by the same storm that impacted Hattiesburg, MS.  The storm survey team found EF-1 intensity damage in Wayne County with a tornado tracking nearly 17 miles in a discontinuous path.  The tornado first touched down near the community of Clara and then tracked to Denham before lifting.

Additionally, EF-0 damage was found in Northwest Perry County – an extension of the track of the same tornado that moved through Hattiesburg and Petal, MS.

Additional details will be forthcoming over the next few days after survey teams complete their data, especially looking on Tuesday in the Washington and Clarke County areas in Southwest Alabama.

UPDATE: 505pm CT – The National Weather Service in Jackson, MS has just upgraded the intensity from the Hattiesburg / Oak Grove tornado that impacted Lamar and Forrest Counties yesterday.  The tornado was preliminarily rated EF-3, but that rating has since been upgraded as damage consistent with 170mph winds was observed in the area of Oak Grove High School.  This violent tornado was only the second violent tornado (EF-4 or EF-5) recorded in Lamar or Forrest Counties since record keeping beginning, the other tornado being the April 24, 1908 Purvis tornado which was on the ground for 155 miles and impacted a wide ares from Louisiana into Mississippi (Source: NWS Jackson MS).

The  NWS storm survey teams have also preliminarily confirmed EF-2 tornado damage in Southwest Marion County – a separate track from the tornado that hit Hattiesburg.  This confirms the suspicions in the original  post that the storm “cycled” and produced separate tornadoes – as indicated by radar signatures.

Storm survey teams preliminarily confirm EF-2 tornado damage in SW Marion County. Seperate tornado track from the one that hit Hattiesburg.

— NWS Jackson MS (@NWSJacksonMS) February 11, 2013

— Original Post Below:

“We were blessed”.  That is what the Mayor of Hattiesburg, Mississippi said repeatedly when interviews on CNN after a strong tornado tore through the city on an otherwise calm Sunday afternoon in February.  As he stated repeatedly, even though the University of Southern Mississippi, several high schools, and the American Red Cross center were all directly hit by this storm, there were only limited injuries and not fatalities.  The fact that we’re reporting on damage to buildings, NOT fatalities is key in this story, and with storms like these, timing is everything.

First off, with students already on a long weekend break with Mardi Gras coming up, so the tornado occurring on the middle day in a four-day weekend meaning that the campus was relatively quiet.  Throw in the fact that the campus is a short two-hour drive from New Orleans, many students were likely out of town for one reason or another.  Additionally, the Elam Arms residence hall was hit by the tornado, blowing out windows to the multi-story residence hall… But the residence hall has not been used for some time, and according to a July 15, 2011 story from WDAM in Hattiesburg, the university was hoping to tear down the dormitory because “it’s considered to be in a prime location, for a developer to put in a business…. An excellent site for a hotel.”

According the University website, several structures in the southern portion of the campus were damaged including Jazz Station, the Mannoni Performing Arts Center, Ogletree Alumni House, and Elam Arms.

Mississippi is no stranger to strong tornadoes as we have seen in years past in places like Yazoo City.  This storm was similar to previous supercells producing long-lived tornadoes.  The supercell tracked from Southern Walthall County in Southern Mississippi through the counties of Marion, Lamar, Forrest, Perry, Jones and Wayne.  The same storm was also responsible for damage near Millry and Coffeeville in Washington and Clarke Counties in Southwest Alabama.

Based on an initial review of the radar data from this storm, the same supercell appeared to have cycled at several points along this 3.5 hour, nearly 170 mile long path.  The National Weather Service Offices in New Orleans, Jackson and Mobile will likely be performing damage assessments over the next several days.  It will be interesting to see where the damage paths are confirmed to have started/stopped, but the most likely points for breaks in the paths appear to be located near the following locations in that path:

• Near the Marion / Lamar County, MS line – slight jog in the storm path to the right
• Southwest Wayne County, MS – Just west of Camp Eight Road in the De Soto National Forest
• Clarke County, AL – The storm appears to have crossed US-84 roughly 5 miles east of Coffeeville, AL

Radar-based rotation path for the Hattiesburg, MS supercell. Note the path changes and possible locations for breaks in the path (cycling supercell).

In all, it is pretty likely that there were multiple tornadoes along this path.  The worst of the damage appears to be EF-2 to EF-3 in intensity, with the Hattiesburg tornado causing damage consistent with a tornado of at least EF-3 strength.  EF2 and greater tornadoes are rated as strong, so regardless of the damage, it is clear to say that the area was impacted by a strong tornado.

Tornadoes are rated by the damage they produce.

EF0…WEAK……65 TO 85 MPH
EF1…WEAK……86 TO 110 MPH
EF2…STRONG….111 TO 135 MPH
EF3…STRONG….136 TO 165 MPH
EF4…VIOLENT…166 TO 200 MPH
EF5…VIOLENT…>200 MPH

On a related topic the National Weather Service in Mobile tweeted the following graphic.  Incredibly their 30 minute forecast for this supercell was HIGHLY accurate both temporally and spatially.  The storm passed within a mile of Robinson’s Junction at 0027 UTC – right in line w/ the forecast graphic below.  The use of Social Media in this case to not only get out the tornado warnings, but to EMPHASIZE areas that are at greater risk represents a MAJOR opportunity for the National Weather Service to enhance their communication with customers.

NWS Mobile – Projected Path of Tornadic Supercell – VERY ACCURATE 30 MIN FORECAST – Storm passed w/in a mile of Robinson’s Junction at 0027 UTC.

Mapping Severe Weather Probabilities

Have you ever wondered if there are patterns to where and when severe weather occurs in the United States?  There are days where we see tornado watches, severe thunderstorm warnings, reports of high wind, hail and even tornadoes.  But, what if you could see these patterns visually – say for example on a map of the country.  Well, University of Oklahoma Ph.D. candidate Patrick Marsh has just created an incredible set of animations hosted on Youtube depicting daily severe weather probabilities over a 30 year period.

You can read more on Patrick’s most recent posts at the links below:

• Climatological Estimates and Evolution of Local Daily Severe Weather Probabilities (Part 1)
• Climatological Estimates and Evolution of Local Daily Severe Weather Probabilities (Part 2)
• Climatological Estimates and Evolution of Local Daily Severe Weather Probabilities (Part 3)

Radar Derived Storm Paths from the 4/14/2012 Tornado Outbreak

Click the Image to Open an Interactive Map Depicting Rotation Paths for Spotter Confirmed Tornadoes

[UPDATED: 4/17/2012 - 12am CT - Several National Weather Service Forecast Offices have completed preliminary storm surveys.  The product I created Saturday evening has been verifying very well, especially with the long-tracked storms.  Comparisons will be added for each tornado below.]

First off.. my thoughts and prayers are with all those impacted by today’s tornadoes, especially in Kansas, Oklahoma, Nebraska and Iowa.  I’ve put together path tracks of the tornadoes based on radar data.

I hope this has helped some people today save lives, and in the days to come, I hope it helps people recover faster from the storms.

Below is an interactive map that is based on spotter confirmed significant tornadic storms.  The points on the map UNOFFICIALLY depict the most likely areas where a tornado went based on radar products from the National Weather Service.  It will likely take several days for authorities in the area to fully assess the damage, but in the mean time, I hope this helps people as a starting point.  Once official damage surveys are released, I’ll be merging them into the map. Also, please note that while the radar may indicate a continuous path, detailed damage assessments and storm surveys may end up splitting these storms into separate tornadoes.

Preliminary Path Estimate for the 4/13/2012 Norman, OK Tornado

Preliminary likely tornado path created at 600pm CT

This post covers the Friday 4/13/2012 tornado that impacted Norman, OK in the evening hours.  The tornado outbreak continues into Saturday.  For the newest blog post covering the Saturday, 4/14/2012 Tornado Outbreak with interactive map, Click Here. (THIS INCLUDES THE PATH OF THE WEDGE TORNADO SW OF SALINA, KS)

4/13 – 1028pm CT – Added link to NWS Norman preliminary UNOFFICIAL track map from @NWSNorman

4/13 – 928pm CT – Updated interactive map to include links to media video and photo of damage with locations.  The locations verify quite well with the initial map points

It’s incredible to think of how today progressed…. First I shared a presentation on this topic to several of my peers around the country to share a methodology with the hopes of helping people tomorrow and in other tornado outbreaks, and the next thing I know, I’m talking to my brother in Oklahoma who is trying to get home to Norman after school, with a tornado warning for his home town.  It’s amazing to see the impact of how technology and information can be brought together to help protect lives.  I ended up helping guide him home to keep out of the storm while the tornado passed less than 1/2 mile from his house, telling him to stay put and keeping him out of harm, but still guiding him home.  Thankfully everyone in the family is safe, but it’s incredible to know that it makes a difference so close to home.

Preliminary Radar Based Rotation Paths – Devine, Natalia, Lytle, TX

During the evening of March 19, 2012, numerous supercell thunderstorms were observed across portions of the Southern Plains.  One of these storms impacted areas just southwest of San Antonio, TX near the towns of Devine, Natalia and Lytle, TX.  While further from the radar site (~60 miles from the radar in Austin, TX), the rotation signatures are definitely present on radar.  Additionally these signatures and their paths are typical of a supercell thunderstorm that “cycles” – essentially where one area of rotation weakens, and a new area of rotation emerges.  Note the time stamps (UTC times) and follow the intersection of the red/green colors along the path as the radar animation progresses.  Also, note how the paths curve to the left before weakening, and then a new area of rotation emerges to the right of the old one.  This is quite typical of a supercells that cycle.

We’ll learn more in the morning and as tomorrow progresses, but if I was to make an educated guess on the areas potentially impacted, they would be as follows:

Survival from the Storm – Couple seeks shelter from Michigan tornado in car wash!

Great to see prayer in a time when there are just no other options – can’t do anything else…  Also interesting to see the statement on our reliance upon technology… when one of the first questions just after you survived the tornado was “Where’s your iPad?” followed up immediately by “there’s no network”, implying that it was already out.

Watch this video of a couple that found terrifying shelter from the Dexter, MI tornado in a car wash (Link to story at Detroit Free Press) – via @jimcantore

With video: Couple found terrifying shelter from tornado in car wash | Detroit Free Press | freep.com.

Radar-Based Maps of the Henryville, IN Storm Tracks

NWS Louisville Statement on the Challenges in Damage Assessment for the Henryville, IN Tornado.

UPDATE: MARCH 6 – The National Weather Service in Louisville has published their initial findings including descriptions of the areas impacted.  That information is available at: NWS Louisville Damage Surveys – March 2, 2012.

Also, I have put together an initial version of an interactive web-map at ArcGIS.com that combines information from the second map below with the damage path information from the NWS in the link above.  The map is accessible at: Web Map of the Henrysville damage path and radar based-storm tracks at ArcGIS.com

ORIGINAL POST: March 4, 2012 – 630pm ET:

The past two days have been full of media reports, tweets and information being shared on the tornado outbreak that occurred on March 2nd, 2012 affecting towns like Henryville, IN.  As you can see from the statement below from the NWS Louisville Forecast Office, there were two supercell storms that impacted the area, with the first one producing the tornado that most people are talking about.  There was in fact a second storm behind the first one that also produced tornadoes and tornadic damage.  To make things more complicated for damage assessment teams, the paths essentially paralleled one another, and even crossed in places, making it difficult to attribute the damage to one storm versus the other.

I’ve put together the following the following map based on the NWS Radar information from the March 2nd tornado outbreak.  The map shows the paths of the two storms and paint the clear challenge that the NWS professionals have in identifying and differentiating between the two damage paths.

Tornado Fatailities and the NWS Dual-Polarization Radar Upgrades

One of the fatalities occurred in this area near Jackson Gap. The NWS warnings for this storm were very clear, telling people to “seek shelter underground” and that a debris signature was appearing on radar.

Some people might ask is it worth it to upgrade the National Weather Service (NWS) radars to this “new” dual-pol technology.  While only 25% of the 160 radar sites around the country have been upgraded, the performance in the March 2, 2012 Tornado Outbreak is quite an impressive statement to the effectiveness of the technology.

During the March 2nd tornado outbreak, many of the tornadoes occurred in areas where the radars have already been upgraded.  When the debris was detected by the dual-pole technology, meteorologists could enhance their tornado warnings, confirming that a damaging tornado was indeed on the ground.  These signatures are essentially as good as visually confirmation of the tornadoes being on the ground.  The technology works because when the radar beams hit debris (leaves, shingles, branches, parts of houses, etc), there is a different signature from what is seen by the radar.  In the graphic above, you can see the blue area in a circle.  This area means that the radar is seeing a “different” signature from the surrounding areas.  When this is in the same location as strong rotation as seen by the doppler velocity products, it is essentially a confirmation of a tornado on the ground at the time of the radar sweep, or just before that time.

This will be significant with difficult-to-see tornadoes, especially ones that are either rain-wrapped or occurring in the overnight hours.

Case Study – 11/7/2011 SW Oklahoma Tornadoes – Radar Indicated Rotation Tracks

Below are several screen captures that I’ve put together showing the locations of the rotation couplets for the SW Oklahoma tornadoes. These are usually spot on with damage surveys [UPDATE: CHECK OUT THE NWS TRACK MAP AND COMPARE IT TO THE ROTATION MAP CREATED FROM RADAR DATA - IT WORKED AGAIN!!]. We’ll see how close they are, but since all points were within 30-40 miles of the Frederick, OK radar site, they’re likely to be less than 1/4 mile off from wher damage would be expected.