Monday, January 30, 2012

The Tornado Chronicles: Birmingham, AL Area Pre-Dawn Tornadoes of 1-23-12

Unfortunately, our fears of nighttime tornadoes came true on Sunday night / Monday morning, January 23, 2012.  Extensive damage was reported during the pre-dawn hours of Monday morning in the Oak Grove, Center Point, Clay and Trussville areas, which are located on the Northeast side of the city of Birmingham, AL.  

The image below was created by the National Severe Storms Laboratory in Norman, OK.  The red and yellow "swirl" paths indicate where doppler radar estimates that a tornado track took place on Sunday night.  The areas circled in red roughly correspond with the actual on-ground damage reports, which the NWS in Birmingham is out surveying at this time.

Of approximately 11 total tornadoes, the National Weather Service (NWS) storm damage survey found 5 tornado paths of EF2 intensity or higher in the general area of Birmingham, as summarized on the map below (please note, this is an approximation only - based on preliminary data):

First I'd like to highlight the series of damage photos below which were taken in the Pilgrims Rest subdivision of Clay, AL.  First, note the "hilly" terrain surrounding the damaged (or destroyed) homes.  Should put to rest any myth's regarding tornadoes avoiding such an area:

The next photo (from the same subdivision) shows what appears to be most of a home laying in the driveway (at left) after having been lifted off of its foundation (at right):

The next two photos show what appears to be a similar result, with the home having been lifted off of its foundation and dropped adjacent to it (or demolished in the case of the 2nd photo):

These appear to be (once) well constructed homes with brick veneer on at least 3 sides. 

Additional photos from the Pilgrims Rest area:

The remainder of the damage photos below are sorted by location (see the notations at the bottom of each photo):

Damage to Commercial Building(s) in Center Point, AL

Wells Fargo Bank in Center Point, AL

Unknown Commercial Damage in Center Point, AL

Residential damage near Clay, AL

Residential Damage in Paradise Valley near Clay, AL

Residential Damage in Paradise Valley near Clay, AL

Home moved off of foundation near Clay, AL

Residential Damage near Toadvine, AL

"Missile" near Trussville, AL

The video below is an unedited version of the damage as captured by the helicopter of the ABC affiliate in Birmingham:

...and from the same crew near Maplesville:

This rather telling "before and after" photo was put together by the AP, and shows what part of one block in Clay looked like before and after the tornado:

Media reports indicate 2 fatalities took place in association with the tornadoes, with an unknown number of injuries (estimated at 100+). The fatalities took place in Clay (a 16 year old girl) and in the Oak Grove community (an 82 year old man).

The images below show the NWS radar near Birmingham at 4:03 a.m. CST, as the tornado was impacting the Center Point area.  The first image depicts the radar in reflectivity mode (i.e., rain, hail, etc.), and the second depicts the radar in velocity (wind speed and direction) mode.  I have placed a small red square on the location of Center Point, very near the center of each image (directly South of Pinson):

Note the "debris ball" on the reflectivity image, and the strong tornado signature on the velocity image.  I have circled both in white on the otherwise identical images below:

A debris ball is a signature that is indicated on radar when debris is literally being lifted up and carried along inside of the tornado and/or the parent circulation in the storm.  This is always a sure sign of a devastating tornado, and one that we saw repeated numerous times in 2011 (click the image to enlarge):

When looking at the velocity image, keep in mind that the red colors indicate wind that is blowing away from the radar, while the greens indicate wind that is blowing toward the radar.  The radar site in this case is located off of the bottom center of the screen.  Thus, the couplet indicating strong rotation near Center Point (within the white circle - click image to enlarge):

Another take away from the reflectivity imagery is that this tornado was 100% surrounded by walls of heavy rain.  Even if it had taken place in broad daylight,  no one in its path would have been able to see it coming.

Needless to say, we need to keep the folks in this region in our thoughts and prayers.

Bookmark this post and check back for updated information, photos, etc. throughout the coming days and weeks.  In a situation like this one, valuable information often continues to emerge well after the event...

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Sunday, January 29, 2012

Relatively Quiet Weather Ahead for Much of This Week; Becoming Active S. Rockies/Plains by Friday/Weekend...

The above image is from the GFS computer forecast model, which is forecasting near normal temperatures across much of the Western and Southern U.S. (grey shaded areas) through at least Friday.  Above normal temperatures (red and orange shaded areas) are forecast for much of the upper Mississippi Valley, Midwest and the Northeast during the same period of time.

It will also generally remain dry across most of the country, at least for much of the period Monday through Friday:

It appears that the weather will start to become active again toward the end of the week and into this coming weekend, with a strong upper-level storm system forecast to emerge out over the Southwest and move into the adjacent Plains.

There is still much uncertainty as to exactly how this system will play out for the end of the week and into the coming weekend, but widespread wintry weather is certainly possible across portions of the southern and central Rockies into the central and southern Plains.  Heavy rain and severe storms will be possible out ahead of this system in the warm sector.

If you live from the Rockies of New Mexico or Colorado into the adjacent Plains of Kansas, Oklahoma and northwest Texas, as well as adjacent areas to the East of there, you'll want to keep a close eye on the latest forecasts for late in the week and this coming weekend.

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Saturday, January 28, 2012

The Tornado Chronicles: Austin, TX Tornado of 1-25-12

A sporadic tornado touchdown took place during the early morning/pre-dawn hours of Wednesday, January 25th in the northeast part of Austin, TX.  

The official National Weather Service survey rated this tornado EF-1 intensity.  The tornado is estimated to have touched down around 2:58 am CST near the intersection of Old Manor Rd. and Commercial Park Drive:

The tornado then traveled in a general Northerly path before ending near Ferguson Lane just Southeast of Sansom Road at approximately 3:05 am CST.  This results in a total estimated path length of 1.14 miles.  The damage swath was 50 yards wide in some spots along the path

Here's an interactive path map that you can look at on Google Maps or Google Earth.  Click on the balloons with points in them to see the corresponding damage photo:

View Austin Tornado Track 1-25-12 in a larger map

I live just South of Austin, so I was able to go up and personally inspect and photograph the damage myself the following day.  Based on what I observed, I do not believe that the tornado was necessarily on the ground continuously, but likely "hopped and skipped" along the above path.

The most concentrated and significant damage took place near both the beginning and ending points of the track.  There were 3 buildings directly impacted near the beginning point of the tornado.  I have labelled their locations as A, B and C on the same track map below:

Building "A" suffered damage to the South (not shown) and West sides, as shown in the photo below:

The circulation then continued Northward, striking a destructive blow to the warehouse next door, which is noted as Building "B" on the above map:

A projectile was ejected from building "B" and became embedded in the exterior wall of a stucco-veneer building across the street (noted as building C on the map).  Please note, the 2 photos showing the projectile were taken by YNN TV in Austin:

The tornado then continued Northward, skipping along its path breaking windows and lifting rooftop air conditioner units off of a few neighboring buildings.  A partially downed wooden fence and a few broken tree limbs were the only evidence of damage as the circulation approached Highway 290 between Springdale Road and Ferguson Cutoff.  

After crossing Highway 290, the circulation entered the Walnut Place subdivision, causing fairly widespread (but generally minor) damage to the tops of trees and some wood fences in the Western portion of the subdivision.  The fence and tree damage below is shown at point "D" on the track map:

The circulation then apparently intensified once again, removing most of the roof of a home located near Happy Trail and E-K Lane (point "E" on the map):

The circulation then mostly lifted again, taking off the tops of a few trees before diminishing near the intersection of Ferguson Lane and Sansom Road.

It is also noteworthy that the parent thunderstorm continued on to the North or Northeast and produced some significant straight-line wind damage in the vicinity of Crystal Bend Drive and Immanuel Road in Pflugerville, including damage to the Pflugerville ISD Bus Barn:

Thunderstorms with heavy rainfall were widespread across the region at the time of the event.  The best radar site with a relatively clear view of the storm was the "Central Texas" site, which is located near Granger (which is located approximately 30 miles to the North/Northeast of the damage path).  

The series of images below show the radar in base velocity mode (wind speed and direction), for each of 2:56, 3:00, 3:05 and 3:10 am CST, respectively.  The two white dots near the center right portion of each image (to the left of the notation of the city of Manor) note the beginning (Southern/bottom dot) point and ending (Northern/top dot) point of the tornado damage:

When examining the wind velocity data, keep in mind that the green colored shadings show wind blowing toward the radar site, while the red colored shadings show wind blowing away from the radar site.  The radar site is located just off of the top right corner of each image.

With the above in mind, the only image that depicts any tight rotation (which would suggest a tornado on or near ground level) is the 3:00 am CST (second) image.  I have circled that rotational couplet in yellow on a copy of the same image below:

The radar estimates that the peak winds at the center of the rotation couplet were blowing at approximately 86 mph at that time.  This was shortly after the damage to the warehouse had taken place, and just before the damage to the roof on Happy Trail likely took place.  

The next two images depict a zoom-in on the rotation couplet as shown in the 3:00 am CST image.  I have noted the couplet by a yellow circle with white arrows showing the wind direction in the second image:

The circulation unwound rapidly by the 3:05 and especially the 3:10 am CST images, however strong, gusty outflow winds of 50-60 mph are noted, which caused the damage to the bus barn near Pflugerville (annotated 3:10 am CST image is shown below):

The reflectivity (rain, hail, etc.) imagery is not particularly revealing, with widespread, heavy rainfall taking place across much of the region at the same time that the damage took place.  The sequence of images below show the same radar in reflectivity mode for the same image times of 2:56, 3:00, 3:05 and 3:10 am CST, respectively:

I suppose you could interpret somewhat of a "comma head", particularly in the last 2 images.  When we look at the velocity data at the same time, we could argue that it was a rotating comma head, which can be associated with wind damage and/or tornadoes.  I've noted what I'm talking about with a white circle on the following copies of the 3:05 and 3:10 am CST images:

A Tornado Watch (#13) had been issued by the SPC in Norman at 10pm CST on Tuesday evening, about 5 hours before the event took place.  The watch was valid until 5am CST Wednesday morning.  There were no Severe Thunderstorm or Tornado Warnings in effect when the event took place.

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