HailSTONE 2 Day 6: 22 May 2012

After leaving work on May 21, I prepared for what would be my second marathon drive in a week's time to meet up with Project HailSTONE for the first time in 2012.  I departed ICT for Watertown, SD around 3:30 pm and finally arrived shortly after midnight on the 22nd.  After a short night of sleep, the PI's held the morning briefing deciding on a target area of Bismark, North Dakota.

The team departed Watertown, SD ~10:30 am to get in position to wait for convective initiation north of Bismark.  After a few car issues (including my data card antenna getting blown off of my roof again), ice cream sandwiches for good luck, and footraces down dirt roads, the cold front had overtaken us without convection initiating due to abundant stratus clouds in the area.  Taking this into account, the team repositioned to the east and was able to salvage the day by intercepting a cluster of storms south of Jamestown, North Dakota during the evening hours. 

 
The team decided to trek eastward across South Dakota and brave gusty outflow winds (measured ~50mph; 5-10mph error) from collapsing storms to return to Watertown, SD for a short night's rest.

First Kansas Tornadoes: 19 May 2012

I departed ICT around 3:30pm after work and quickly outfitting my car with chase gear.  Due to my late departure time, I chase to adjust my initial target area eastward from Pratt, KS to Kingman, KS.  Unfortunately, my late departure prevented me from being able to join Project Hailstone for operations on this day.  With meager low level shear, my main goals for the day were to get back into the groove of chasing before rejoining HailSTONE, shoot structure and observe hail.

Storms initiated along the cold front across Central Kansas around 4pm, with the southernmost cell near Stafford, KS showing the most promise.  Upon reaching Kingman, Kansas a little after 4:30pm, I decided to move north on State Highway 14 and northeast on back roads toward Hutchinson to get ahead of this particular storm. After spending an hour shooting structure and observing the updraft base of the storm that featured persistent rainfall in the vicinity, I noticed the storm begin to move to the southeast and backbuild toward cumulus towers that were going up to the south.

At this point, I decided it was in my best interest to proceed south on highway 17 toward Murdock, KS.  Before I could do this, I met the entire ROTATE team waiting to turn onto the same road. After allowing the ROTATE team to go ahead of me, I was able to proceed south.  After 5 miles of driving south, I spotted a thin funnel cloud through the persistent precipitation in the vicinity of the updraft.  After quickly pulling over and grabbing my camera, I observed and documented two seperate rope landspouts that lasted a little less than a minute apeice.

After documenting these landspouts, I noticed storms were beginning to initiate and intensify to the south of my storm, thus introducing the chance for mergers to occur. I decided to quickly proceed south of Highway 400 toward Harper and Argonia, where I began to take back roads to better position myself to observe additional tornadoes. I coincidentally ran into Jared Leighton and Mike Mezuel from the HailSTONE team while repositioning to the south and observed my third tornado of the day near Rago, KS from a distance over the trees that landscaped the area.   Upon my initial analysis of radar data, it appears that these tornadoes formed as the result of a storm merger, thus marking the first time that I've observed such an event from start to finish in the field (12/31/10 in Jackson, MS was also a merger, but rainwrapped).

After finally briefly getting caught in hail, I quickly blasted southeast out of the path of the rapidly developing QLCS and shot some structure in the company of some storm chasers from Switzerland near Caldwell, Kansas.  After observing some decent structure, several CG strikes, and a colorful sunset behind the newly formed QLCS, I wrapped up one of my most surprising and satisfying chases with a short drive back to ICT.

Distance: 200 miles
Wx: 3 tornadoes, large hail, structure

Slight Risk, No Reward: 11 March 2012

On a day where there was little school work to do, Cooper, Blanchard, and myself departed MLU around 11am with an initial target of Fordyce, AR.  Although this particular day garnered the attention of the SPC, who issued a 10% tornado risk across much of Central and Southern Arkansas into Northwestern Louisiana in their morning outlook, My expectations for this particular chase were tempered. Stratus covered much of the region from the previous day's convection that was generated from a residual MCV in northeastern Texas. This would greatly inhibit destabilization across the region, thus making intense convection in the target area a longshot.

The morning sounding from KSHV revealed no instability and no capping inversion, which would allow storms to quickly intensify and new storms to initiate over a large area as existing convection moved into the pre-frontal convergence axis.

Regional radar showing stratiform rain affecting the target area in southern Arkansas as convection intensifies in the pre-frontal convergence zone in far eastern Texas. 

Upon arriving in El Dorado, AR around 12:30pm, we were greeted by cool stable air and a light stratiform drizzle that essentially killed any chance of decent convection over the target area as expected. After spending about 30 minutes analyzing the situation around Shreveport and deciding that the main threat for the remainder of the day would be damaging wind and a few isolated MCS/QLCS tornadoes, we decided to chalk up our losses and return to Monroe.

Miles: 200
Wx: None

First Chase of 2012

After initially deciding not to chase on a day where parts of the southeast and Midwest would experience the largest severe weather outbreak of the year to date; Cooper, Blanchard, Chenoweth, and myself decided to go spot around the Monroe area.  Upon convective initiation shortly after 18Z (12pm CDT), I initially did not pay much attention to the storms as they formed in a linear fashion oriented from southwest to northeast along a pre-frontal boundary.  At this stage, it appeared that QLCS formation was imminent.  However, a fairly significant amount of CIN observed on the morning sounding from SHV was responsible for limiting convection to the area of strongest forcing (along the pre-frontal boundary).  This allowed for an isolated storm mode along the boundary, thus making it conducive for some storms to exhibit supercellular characteristics despite the lack of 0-1 km directional shear in the area.  

 12Z KSHV Sounding courtesy of the SPC.

One storm north of Ruston, LA piqued my interest around 2045Z.  Although hail was the main threat with these isolated storms, this storm in particular was one of the first storms to exhibit rotation at upper levels on radar (due to radar beam properties as the beam travels away from the radar).  With this storm being so close to our location, Cooper and I rounded a few people up and departed MLU for Sterlington, LA around 21Z to check the storm out.

 Convection across the Southeast ~21Z.  Note the isolated nature of the cells in Northern LA.  Image courtesy of UCAR image archives.

Upon our arrival to the Sterlington area, Cooper spotted a wall cloud to the west of Sterlington associated with our storm of interest.  As expected, this wall cloud was not rotating at all due to lack of directional shear at the lower levels of the atmosphere, but was fairly picturesque for Northeast Louisiana.  Despite its history of producing up to golfball sized hail in Union Parish, no hail was observed in the precipitation core of the storm.  After spending 15 minutes observing the storm’s characteristics as it moved off to the northeast, we decided to relocate to the south of Monroe in anticipation of another storm that was exhibiting supercellular characteristics south of the Ruston, LA area.  

 Part of the chase party.

After a quick drive through Monroe and Richwood, we decided to stage just outside of Logtown, LA and wait for the storm to come to us.  Despite our timing and excellent positioning, mother nature did not produce a repeat of what was observed in the Sterlington area.  This particular storm went outflow dominant just to the southeast of Ruston, which choked off its warm inflow causing it to begin a weakening cycle as it approached the Richwood area.  Several interesting undulations in the cloud deck associated with the gust front responsible for the demise of our storm were documented by Cooper.  Despite the weakening trend, RFD was spotted and documented wrapping around and eventually concealing the main updraft base of our storm, providing another excellent photo opportunity.  Almost immediately following this, a wind shift to the west and increase in wind speeds were experienced followed by a ~10 degree Fahrenheit drop in temperature, thus effectively marking the end of our first expedition of the new chase season. 

Chase Highlights

1 Non-rotating Wall Cloud

58 Miles

2011 Season Recap

Chases: 10  (4/4, 4/15*, 4/27, 5/19, 5/20, 5/21**, 5/22, 5/23, 5/24*, 5/25*)
Successful Chases: 9 (4/4, 4/15, 4/27, 5/19, 5/21, 5/22, 5/23, 5/24, 5/25)
Busts: 1 (5/20)
Storms Intercepted: 13
Tornadoes: 7  [Strongest: EF4 (5/24)]
Largest Hail Intercepted: ~1.75in [(Golfball sized) (Does not include HailSTONE collection)]
Strongest Winds Encountered: ~60 mph
States Chased In: LA, AR, MS, OK, KS, AL
Miles Driven: 6,089

*denotes days where tornadoes were observed
**denotes multiple tornadoes observed

Recap:

4/4: Targeted Northwest Mississippi with Cooper in hopes of intercepting semi-discrete cells out ahead of the ongoing MCS, as well as bowing segments within the MCS.  We succeeded in intercepting several semi-discrete cells that managed to produce sporadic quarter sized hail.  Unfortunately, the section of the MCS that we traversed gusted out before reaching our location north of Tupelo, MS, therefore no severe winds were experienced on a historic day for wind damage reports.

4/15: Forecasted semi-discrete cells to form south of an ongoing MCS due to outflow boundary interactions in Central LA early on this day.  This forecast verified, however class didn’t allow me to depart MLU until well after 10:00am.  At this point, the initial discrete cell matured into a supercell and produced an EF3 tornado in Jackson, MS.  I managed to salvage the chase by chasing all the way into far Eastern MS and extreme Western AL intercepting 3 different storms (1 originating from an outflow boundary, the other 2 from a “dry boundry”)  bagging two wall clouds and a semi-rainwrapped cone tornado near Quitmann, MS.

4/27: Did not intend on chasing on this day, however ended up in the middle of the Apocalypse on the way home from Dauphin Island, AL.  Cooper, Torres, Voight, Willis, Keys and I intercepted a strengthening storm near Crystal Springs, MS as it crossed I-55.  This particular storm featured two “hooks” at the time of intercepting.  We barely missed the first hook but managed to document and call in a rotating wall cloud associate with the second hook.  The gradient behind the dry boundary in eastern LA was among the strongest that I’ve ever personally experienced - extremely strong gusty winds made driving a challenge.

5/19: Day one of Project HailSTONE was met with a marathon drive from MLU to Wellington, KS beginning at 2am.  Operations commenced upon arrival in Wellington with a brief training before jumping right into the action.  The team intercepted several storms the weakened rapidly before intercepting a storm that produced decent results near Jetmore, KS that evening.  The day officially ended in Woodward, OK 24 hours after initially departing from MLU.

5/20: Day two of Project HailSTONE turned out to be a bust.  However, this provided valuable time to have a proper training session as well as bonding time with members.  Following training and practice, activities for the day included a heated game of rock curling, touring a wind farm, and climbing a mesa to watch a storm ~80 miles to our north at sunset.

5/21: Day three of Project HailSTONE was an epic day on many levels.  The team intercepted two supercells that featured incredible structure and produced ~5 tornadoes total (4 were documented by Cooper and I before going into collection mode).  To top this off, a successful data set was collected by the team.

5/22: Day four of Project HailSTONE was arguably the most difficult day mission-wise due to the HP nature of the storms.  The strength as well as the destruction produced by the Joplin, MO storm made collection and communication extremely difficult on this day.

5/23: Day five of Project HailSTONE was by far the most successful day of the project.  The team identified an Oklahoma record sized stone that was 6 inches in diameter.

5/24: The final day of Project HailSTONE was short lived due to the excessive forward speed of the storms as well as the high number of tornadoes.  Operations were called off and the team chased the tornado outbreak in central OK.  After nearly getting stuck on dirt and clay roads, Cooper and I rebounded and managed to punch into the hook of a tornado producing supercell near Chickasha, OK.  We were able to follow and document the EF-4 for the duration of its lifetime.

5/25: Before ending our spring season, Cooper, Kelley and I chased the high risk in northeast Arkansas.  We witnessed a brief tornado on our storm north of I-40 before chasing its persistent wallcloud into the flooded plains of northeastern Arkansas.  Cut off by the historic Mississippi River flood, we trekked back toward I-40 in hopes of getting on the next storm.  However, a very crowded I-40 prevented us from achieving this as the storm raced ahead of us into Tennessee producing a tornado around Memphis in its wake.

HailSTONE Identifies Oklahoma Record Stone

Project HailSTONE, the project in which me and Dylan participated in this past spring identified an Oklahoma state record hail stone (6 in. diameter) on 23 May 2011.  Read more about this exciting announcement at http://www.hailstoneresearch.org/may2311news.html

March 5, 2011 Southern Louisiana Severe Wx

This past Saturday, March 5, 2011, southern Louisiana was rocked with another round of severe weather, with the primary storm modes being wind and tornadoes.  Unfortunately, this episode of severe weather proved to be both damaging and deadly, as a fairly short lived tornado produced EF2 damage in the town of Rayne, LA killing one person and injuring twelve others in its wake.  This was one of nine tornadoes that were produced across Southern Louisiana last Saturday, with four occurring in WFO LCH's CWA and five occurring in WFO LIX's CWA (County Warning Area).


What caused this event?
Through the analysis of upper air soundings and maps, I was able to identify several important features that were responsible for the initiation of this severe weather event.  In order for severe thunderstorms to occur, several conditions must be in place in conjunction with several atmospheric processes.  A moist layer of sufficient depth must be present in the lower to mid troposphere (including the boundary layer), instability, and source of lift (e.g. forcing from a front, upper level shortwave).  A fourth ingredient, wind shear, is crucial for the formation of supercell thunderstorms and tornadoes. 

This event initiated when several subtle shortwaves downstream of a well defined vort max passed over SE Texas and SW Louisiana, providing the lift needed for thunderstorms to develop.

 

 A series of subtle shortwaves are denoted by the red circle.  A well defined vort max (red area) can be identified over west Texas.  The "X" in this area denotes an area of maximum vorticity while the N to the north of this area denotes an area of minimum vorticity.  With the area of interest being downstream of this vort max, positive vorticity was advected into the area with time thus enhancing vertical lift over SE Texas and SW LA 

The 12Z sounding from WFO LCH profiled the atmosphere about an hour before the initiation of this event.  Multiple features in this sounding support the potential of severe weather.  The black boxes denote the depth of two significant dry layers in the atmosphere.  The wind profiler shows backed surface winds and veering winds with height.  Winds increase with height, thus indicating the presence of speed and directional wind shear.  The red box in this area of the sounding shows slight backing of the winds at upper levels, thus indicating slight cold air advective tendancies.  The "inferred temp advection" graph supports this observation, denoting temperatures decreasing at rates of 0.6 and 0.7 degrees Celsius per hour.  The hodograph in the top right area of the picture supports the observations made from the wind profile.  This tool shows how wind direction and speed change with height.  0-1 km shear (denoted by the black box) indicated that the atmosphere was conducive for rotating updrafts.  Despite these features, a weak capping inversion in the lower levels was inhibiting convection at the time the atmosphere was profiled (SB CIN values of -46 and ML CIN values of -149).  This cap quickly eroded in the hour following this sounding and allowed thunderstorms to develop.  

The Event

The image above is a base reflectivity overview of the entire MCS.  The red "L" just to the south of the Louisiana coast (Cameron Parish) denotes the location of the subsynoptic low that influenced storm motion.  The black arrows show the differences in storm motion with respect to distance from and location around the low.  Convection well ahead of the main thunderstorms featured a northerly component of motion whereas activity behind and north of the low featured a southerly component of motion (air rotates counterclockwise around low pressure systems in the northern hemisphere).  The main convection associated with this system moved to the eastnortheast as the entire MCS propogated to the east. 

Surface observations around the time of initiation (~13Z).

Jefferson Davis EF0's

This is a base reflectivity (BR) and storm relative velocity (SRV) image the supercell thunderstorm that produced two EF0 tornadoes in Jefferson Davis Parish.  At the the screen shot was take, the second EF0 tornado was in progress.  The base reflectivity product features an impressive signature that supports the strong velocity couplet that is featured in the SRV product.  The BR image shows areas of higher reflectivity associated with heavier rainfall "spiraling" toward the area of lower pressure where the mesocyclone and tornado were located.  The behavior of the rainbands is a direct result of the strong inbound/outbound velocities that are shown by the SRV product.  The red arrow in the BR image denotes modified inflow air (modified by wetbulb cooling at the surface due to rainfall) being advected into the inflow notch to the northeast of the mesocyclone and tornado.  This particular storm eventually gusted out as a rear inflow jet built into the area, leading to several more tornadoes, including the Rayne EF2.

Crowley & Rayne Tornadoes

Both the Crowley tornado (EF0) and the Rayne tornado (EF2) were the result of bookend vorticies, as a rear inflow jet built into the area.  This inflow jet may have been the result of wet-bulb cooling occuring in the mid-levels of the thunderstorm that was located just to the west of the HP supercell that produced the Jefferson Davis Parish tornadoes.

In this series of photos, I utilized the base reflectivity (BR), storm relative velocity (SRV), echo top (ET), and normalized rotation (NROT).  The echo top product shows cloud top heights.  The NROT product is an algorithm that was developed by the makers of GR Analyst.  This product features a range of -5 to +5. Anything above 1.0 is significant and values above 2.5 are extreme.   A detailed explanation of this product can be found here: http://grlevelxstuff.com/forum/showthread.php?t=314.

The BR product in the photos above show streaks of lighter reflectivity in the trailing stratiform precipitation behind the tornado producing thunderstorm.  This signature suggests the presence of a rear inflow jet.  This occurs as strong winds change the direction of rain droplets from vertical to horizontal, thus preventing the radar beam from intercepting some these droplets and leading to lighter reflectivity returns.  The series of photos also shows the evolution of the velocity couplet, with it being the strongest and tightest over the city of Rayne.  Gate to gate velocity (inbound/outbound velocity combined) was 85 knots and NROT values were 1.53 at the time.  Echo tops associated with this storm peaked ~41,000 feet.

All together, 683 homes were damage with 42 being completely destroyed and 48 receiving major damage in Rayne.  Unfortunately, these two tornadoes injured a total of 15 people and killed one woman when a tree fell on the house she was in. 

How does a bookend vortex form?

Bookend vorticies are the result of shear vorticity (a form of relative vorticity).  The photo above illustrates this process very clearly.  As strong winds move through an area, it creates areas of vorticity on both sides of the area of strongest wind.  This is the same principal as dragging your hand in bathwater.  The water that is not being pushed by your hand has a tendancy to rotate away from the area of forcing, thus creating vorticity on a small scale.  Although the image above is a model of this principle at the 300 hPa level, this can occur at any level in the atmosphere.


Southeastern Louisiana Tornadoes
The tornadoes that were produced in southeastern Louisiana were also the result of a shear vorticity/bookend vortex situation.  Of the five tornadoes in this region, four were EF0's and one was rated EF1.

These two cases from SE Louisiana explicitly show the same radar signatures that the Crowley and Rayne storms exhibited.  Bookened vorticies and areas of rotation are depicted by the black circles in each image.


What lessons were learned?
In conclusion, March 5, 2011 is another classic example of the kinds or tornadoes that we are faced with in Southern Louisiana and throughout the southeastern US.  Unlike many cases from the Great Plains, tornado producing storms in the south are often messy storm structure wise, making them much more difficult to detect and dangerous to chase.