TWISTEX Field Operations for April 28, 2011

April 28, 2011 – 6:45 am

Currently in a southern suburb of Birmingham, AL


Historic tornado outbreak in Dixie Alley yesterday with a reported 162 tornadoes (as of SPC this morning).  All of the severe weather parameters were textbook perfect, with sickle-shaped hodographs everywhere in Mississippi and Alabama, and with incredible low level shear, provided the perfect environment for destructive tornadoes. Almost every storm that initiated in Dixie Ally created tornadoes sometime during their lifespan.

Intercepted numerous violent tornadoes including the long-track tornado that moved through the Tuscaloosa and Birmingham area claiming numerous lives.  These tornadoes were moving at 50 MPH making any kind of instrument deployment extremely dangerous.  We witnessed the Tuscaloosa tornado about 30 miles to the southwest of Tuscaloosa, and immediately called emergency personnel warning them of the tornado in progress.

All of these tornadoes were only intercepted once as they passed the highway in front of the team.  One interesting item of note–these tornadoes were passing through trees that were 40-80′ high, and noted that due to the surface roughness(created by the trees themselves), the tornado vortex was very disorganized near the ground, and by visual observations-the collective wind speed was considerably less.   Even these violent tornadoes were not simply a ‘buzz saw’ moving through the trees maintaining good vortex structure.  As the vortex crossed the road in front of us, it briefly ‘organized’ into a continuous ‘cone’, then broke apart as it progressed to the east back into the vegetation.

Kudos to the entire team yesterday.


Today begins a multiple drive day back to Colorado.  There is a small opportunity for a chase in SE OK on Saturday, but this will be carefully monitored and weighted on delegating time to fully prepare for full TWISTEX operations in a week.

RADAR installation will likely commence sometime next week if all the hardware is ready.


After a brief return of severe weather in OK on Saturday, we might get a long needed break for the crew to continue final preparations.

TWISTEX Field Operations for April 26, 2011

April 26, 2011 – 8:51 am

Currently in Palestine, Texas

April 24:

Witnessed three tornadoes near Baird, TX.  One of those tornadoes was a large multi-vortex tornado along the forward flank of the supercell. Original target two days ago was around the Abilene, TX area. Forward-flank tornadoes are very difficult to deploy instruments on, as they often have unpredictable motions, and are short-lived (at least most of the time).

April 25:

Witnessed one tornado southeast of Teague, TX yesterday.  Storm initiated just southwest of the Dallas-Ft. Worth metroplex with fears of the storm tracking along the southern suburbs.  Fortunately, the storm tracked south of Cleburne to Oakwood, totally missing large populated areas.  Tracked the storm through Oakwood, and terminated the mission at dark.


Parameters are coming together for a significant tornado outbreak initiating within a Paris-Sulpher Springs-Mt. Pleasant, TX corridor.  We struggle to find anything wrong with the forecast.  Large sickle-shaped hodographs are suggested by the RUC south of the Red River with 0-1 KM EHI over 10.  Its been a long time since we’ve seen such a perfect tornado forecast such as this.

Team plans to depart for the suggested corridor by 10:30 AM.


Perhaps another repeat of a tornado outbreak is likely in the Tennessee valley/Alabama area.  Once again, it seems that everything is in place for another round of significant tornadoes beginning mid-late afternoon in the aforementioned area.


Next system should move across the midwest late this week, but difficult to evaluate due to model differences, and evolution(s) of current system.

TWISTEX Field Operations for April 23, 2011

April 26, 2011 – 6:47 am

Currently on the road from St. Louis, MO

Yesterday, April 22:

We had an original target of a few miles north of the St. Louis, MO area, where a warm front was lifting northward providing excellent low level (0-1 km) shear.  Model data suggested that storms would fire along the warm front, so our group waited north of the St. Louis area.

Storms initiated along the cold front around 22z, and of particular interest–the northern most storm along the ‘triple point’ initiated southwest of Columbia, MO.  We also noted an isolated storm initiated in the warm sector east of the cold front and south of the warm front, and initially targeted that storm.  For whatever reason, this isolated storm struggled, so we decided to target the storm that within this triple-point area moving towards us at 40+ mph.  Storm was projected to cross just north of Hermann, MO and with only 5 minutes to spare, we drove through town, and watched a low wall-cloud/foward flank overtake us on a road that lead us back to I-70.  Encountered 2″ hail (no broken windows) with occasional baseball hail.  Hail up to 4″ were noted along the road.

Supercell storm evolved several times as it traveled towards the St. Louis area after dark.  As the storm went through a cell merger near New Melle, MO (outskirts of St. Louis), it quickly went tornadic as our group raced ahead to get in position.  Tornado was rain wrapped as it crossed just to our north, only offering a quick glimpse of the large ‘elephant trunk’ type shape before dissipation.  Significant damage was noted in the town of New Melle, MO.

We then repositioned ourselves as the storm went through another evolution from a linear-type structure to a developing hook just to the northwest of the St. Louis area.  Probe actually collected MM data of the developing hook area just before tornado genesis occurred for the second time.  Team dropped south of the hook, and witnessed power flashes, and offered glimpses of the white ‘cone’ type tornado as it devastated the community of Maryland Heights, MO.  Tornado crossed I-70 where several semi trucks and vehicles were overturned.  Fire rescue was on the scene very fast, so the decision was made for our TWISTEX team to immediately leave the area to help relieve the traffic congestion for emergency vehicles to get through.  Very impressed on how quickly emergency personnel were on the scene.  Terminated the chase and stayed in southern St. Louis for the evening.  Looking at the damage on morning TV newscasts showing significant damage—perhaps EF3(whole structures destroyed).

Instrumentation, vehicles, and equipment performed very well.

Heck of a first day.


Currently en-route to the Texas Red River area where a marginal day exists for tornadoes from Little Rock, AR to Dallas, TX.  Not impressed with 200 mb winds over Arkansas, but much stronger (in time) over the southern end of the target.  Low level turning (0-1 KM) decreases in time over the whole area, so chances of tornadoes is far less than yesterday.  Excellent moisture and reasonable surface winds exist in a Dallas-Gainsville-Paris Texas line.  Chances of extremely large hail is high over the same path.  Our plans is to follow the stationary boundary to the Red River area through Little Rock, AR and work our way to the Paris-Gainesville area by late afternoon.


Part of the mission today is to get our group to the Red River tonight for an active day tomorrow.  Haven’t spent a lot of time looking at tomorrow, but it looks like the next 500 mb trough swings our over the Texas hill country by tomorrow afternoon with adequate moisture and a sharp dryline should provide the focus for intense convection from the Childress-Abiline-Stockton, TX area.


Monday and Tuesday are forecast to be a very active period for the Mississippi-Alabama area.  Will evaluate this later.

Start of TWISTEX 2011

April 26, 2011 – 6:43 am

Currently in Norman, Oklahoma

Our program objectives are described in detail on our website:

The following items will be new for this year:

* X-band RADAR provided by EWR located in St. Louis, MO.

* Revised tornado in-situ instrument with additional wind speed measurement capability and acoustics monitoring.  A new wind speed sensor is currently being developed for inclusion on instrument.

* ‘Probe’ vehicle converted to a flatbed with toolboxes for easy deployment of in-situ probe and inclusion of the RADAR system.

Field effort will be divided into two parts:

* Limited TWISTEX deployment:  April 21- May 5 (Probe and M3)

* Full TWISTEX deployment:      May 5- 30 June (Full vehicle deploymennt Probe, M1, M2, M3)


April 21:

Our first day of limited operations may commence on Thursday.  The limiting factor is having adequate moisture after the cold front passes through Oklahoma today.  At the moment, only 50F dewpoints are expected in northern Oklahoma.  We’ll be monitoring this to see if there is enough moisture for operations on Thursday.

April 22nd:

At the moment, an active day seems to be in order for this Friday as the next system moves through the midwest from Colorado.  Excellent shear and adequate moisture are in place to support Supercells with (possibly) strong tornadoes from Missouri through Illinois.


Looks like a break in the action for the weekend, with an active pattern returning to the plains states by Monday and Tuesday.

PROGRAM END: TWISTEX Field operations

July 1, 2010 – 9:35 am

As of today, TWISTEX operations have concluded operations for the year.

The crew had one last trip last Friday/Saturday (June 25, 26) where they intercepted a rain-wrapped tornado that wasn’t visible near Courtland, Minnesota on 25 June.

TWISTEX had a very successful 2010 with several in-situ deployments and numerous mobile mesonet datasets collected.  Some in-site hail data was also collected.

The new 450 pound in-situ instrument was deployed once in the path of a developing EF4 tornado near Bowdle, South Dakota on June 22.  We’ve collected the first-ever wind speed data at two different heights (.7 and 2 meters).

Several abstracts have been submitted for approval to be presented at the upcoming Severe Local Storm Conference to be held the week of October 11-15 of this year as a result of TWISTEX operations.  Topics include:

‘Recent In Situ and Very Close Proximity Tornado Observations (Karstens, et. al.).’

‘Surface Observations of the Rear-Flank Downdraft Evolution Associated with a Violent Tornado near Bowdle, SD on 22 May 2010(Finley, et. al.).’

‘Surface Observations of the Rear-Flank Downdraft Evolution Associated with the Aurora, NE Tornado of 17 June 2009 (Lee, et. al.).’

‘Wind Measurements Within a Tornado Core (Samaras, et. al).’

We wish to thank all of the TWISTEX participants for their tireless efforts as we logged nearly 28,000 miles traveling from Montana to Arkansas-from southern Texas to Minnesota from the middle of April until the end of June.  Crews had to endure hardships of being away from their families, and having to deal with hotels and food of varying qualities on the road.

With five to six vehicles within the TWISTEX armada, there was not one safety/traffic incident the entire 11 weeks being on the road.

Everybody’s efforts have been rewarded with some of the richest datasets ever collected from Supercells and tornado cores/environments to date.

I also wish to thank all of the supporters of TWISTEX both in funding and vehicle support hardware.  Without all of your support, the TWISTEX research mission would not have been possible.

TWISTEX investigators are currently planning TWISTEX 2011 for next season with hopes to have mobile Doppler RADAR aboard.  RADAR is the research tool that TWISTEX needs to help provide kinematic descriptions of tornadoes and supercells.

Continued improvements to current tornado in-situ technology are also planned for more accurate wind and pressure measurements in the future.

In a few months, my attention will turn towards lightning research, and a similar email dissemination will begin around the first of August.

Please let me know if you wish to be REMOVED from the lightning research list.

Until next year!

Tim Samaras

TWISTEX Field operations for June 18, 2010

June 18, 2010 – 12:34 pm

Currently in Minneapolis/St. Paul


A frustrating day for part of the TWISTEX group. A flat tire in Lemmon, South Dakota yesterday morning delayed our departure to the tri-border area of South Dakota, North Dakota and Minnesota where the triple point of a pre-frontal trough, a cold front, and a warm front come together.

Fortunately, part of the TWISTEX group (M1, M2) were ahead of us and were able to witness numerous tornadoes including the wedge tornado that eventually caused significant damage in Wadena, Minnesota.

We (Probe, M3) were 10 minutes late, but was able to witness the RFD (with rain-wrapped tornado inside) move over the Wadena area from the southwest. On the southwest side of the RFD, a smaller sattelite circulation/tornado was observed going through the south part of Wadena, where stunned residents were outside trying to asses the damage. We (M3, Probe) stopped to let law enforcement know of the pending situation while in town, as nobody was focussed on the sky at that point.

Drove through the western part of the township only minutes after the tornado passed through and met up with the TIV group (Tornado Intercept Vehicle). We assisted to help extract an injury (Marcus mentioned possible broken pelvis, possible back injuries) from a severely damaged house, and loaded into a waiting ambulance. After that-myself, Carl Young, and son Paul went house to house looking for people needing assistance. Extensive damage was found in the main damage path including vehicles lofted and thrown 10s of meters. Observed significant damage to the local high school-which looks like a total loss. A school bus was smashed to half it’s size. Several rail cars were derailed, as well as an unknown steel building or grain bin being tossed several blocks and smashed on several houses. Based on our observations–probably EF3 damage, perhaps more pending a more detailed NWS survey of the vehicles that might have been lofted and thrown.

Once the town had enough emergency workers on site, group left to pursue another tornado warned storm to the distant north east that we failed to keep up with.

Strongly mixed emotions prevail with our group this morning, as TWISTEX could not totally operate on this storm, due to Probe being only 10-15 minutes late. We halted the chase (letting the tornadic storm drift off to the northeast) so that we can assist the hard hit area of Wadena. Spending time searching for victims puts into perspective on why TWISTEX is so driven to understand these powerful storms.


Looks like a reasonable play in north central/northeast Iowa today along the cold front as extreme CAPE values reach nearly 5000 J/Kg. Wind profiles aren’t perfect, but should be adequate for very large hail and possible tornadoes. If the windfield can remain backed (RUC shows a small meso-low in northeast Kansas), a strong tornado is possible. Big unknown today is how the current convective line will affect mid-late afternoon storm initiation. Model data suggests that renewed convection should initiate by 22z.


Chances of operations may continue through early next week as the last piece of energy passes through the midwest. Variances in the model data precludes specific targets, but it appears that operations are possible in Nebraska and South Dakota.

After Wednesday, the model data suggests that the summertime ridge will settle in, thus its quite possible that TWISTEX may terminate by the end of next week.

TWISTEX Field operations for June 15, 2010

June 15, 2010 – 9:27 am

Currently in Norman, Oklahoma

June 13:

Team intercepted a long lived tornado at very close range north of Booker, Texas in the Oklahoma panhandle. Tornado was moving too fast towards us for deployment of instruments, and the path was mostly off the east-west road we were on. TWISTEX had two mobile mesonets to the immediate east of the tornado, and two mesonets to the west collecting data from both sides. Observed another tornado 7 miles away near Slapout, Oklahoma


Looks like two more days of operations are likely Wednesday and Thursday. Strong mid level flow emerges into the plains on Wednesday from Montana through western Nebraska.

On Thursday, the mid level wave pushes hard to the east providing a very strong environment for supercells and tornadoes from Manitoba through Minnesota and Iowa. Mid level flow along with a very powerful low level jet across a broad region of the northern plains will create very favorable hodographs that will favor strong supercell development.

It appears that after Thursday, operations will likely go down for an extended period due to zonal flow fo several days through the weekend.

Denver team plans to drive to Denver today, and will depart for the Dakotas/Nebraska early Wednesday morning.

M1/M2–let us know of your participation status for Wednesday–and will discuss tentative targets for tomorrow afternoon.

All participting teams–please do bring your passport, as there is a chance that we might be crossing the border into Canada on Thursday.

TWISTEX Field operations for June12, 2010

June 12, 2010 – 9:40 am

Currently in Goodland, KS

June 10:

Team intercepted tornadic supercell near Last Chance, Colorado (we were too late to see the tornadoes–they touched down in a roadless area anyways). Followed the storm to the Colorado border where the storm struggled to produce any more tornadoes. Stayed overnight in Goodland, Kansas

June 11:

Drove to Limon, Colorado where the team eventually intercepted a large supercell coming out of Simla, Colorado. Storm briefly produced baseball hail where several high-speed images were collected from falling hailstones impacting the plate (need to review yet). Followed the storm eastward down I-70 where team members witnessed several ‘spinups’ along the way, but no significant tornadoes reported. Stayed overnight in Goodland, Kansas.


Cut-off low is centered over New Mexico, and a cold front will push through most of western Kansas into the Texas panhandle where the front (hopefully) stalls. A short span of easterly/southeasterly surface winds, with 30-40 knot mid level winds should provide a reasonable environment for supercells and very large hail. Tornadoes are also possible across the Texas panhandle northwest of Amarillo.

Crew will depart around 8:30 for the northern Texas panhandle for possible early initiation around 20z.


Chance of severe storms on Sunday, as the cold front stalls across the Texas panhandle. At the moment, it appears that the chances of tornadoes will be less than Saturday, but given the fact that the team will be in place in the panhandle already, we’ll give it a shot.

After Sunday, it appears that the chances drop significantly, and its quite possible that operations will briefly end until late in the week when the next wave emerges on the plains Thursday.

TWISTEX Field operations for June 10, 2010

June 10, 2010 – 12:33 pm

Currently in Lakewood, CO

June 9:

Intercepted severe storm as it initiated about 20 miles southwest of Torrington, Wyoming. Several attempts at tornado genesis were witnessed as strong RFD winds continue to wrap into updraft base, but failed. Followed the storm into Scottsbluff, Nebraska, where the storm died. Stayed in Scottsbluff for the evening


Surface low is forecast to deepen in Colorado, and in response-modest upslope flow develops across northeast Colorado, southwest Nebraska, and southeast Wyoming. A disturbance is expected to pass through the area by mid evening, thus thunderstorms are expected to develop across the Colorado/Wyoming front range, and rapidly become severe as they move off into the eastern plains. A low level jet is also expected to develop by mid-late evening, and will aid in the development of tornadic supercells especially after 6 PM. Limiting factor are the warm mid level temperatures-but with the expected short wave, thunderstorm initiation shouldn’t be a problem(?)

Preliminary target is Julesburg, CO–or we may choose to stay near the I-80/I-76 junction to give us mobility to either adjust to Colorado or remain in Nebraska (perhaps McCook?) as the day progresses. Not an easy forecast.

Current parameters could come together for a big day.


Low continues to dig south, and will likely ‘cut off’ by the weekend. The speed and progression of the cut-off low is difficult to predict, but it appears that we’ll have opportunities for field deployments through the weekend. By Wednesday, the system finally ejects east, thus the severe threat lessens considerably, thus TWISTEX will likely be down for a period of time beginning the middle of next week.

However–current model variation suggests that the above outlook will change.

TWISTEX Field operations for June 9, 2010

June 9, 2010 – 9:22 pm

Currently in Lakewood, CO

June 7:

Intercepted two supercells from Torrington, Wyoming to Scottsbluff, Nebraska. The western most cell seemed to be the one most likely to produce a tornado. Intercepted the supercell when it was north of Scottsbluff, and when it was tornado warned (actually produced a brief tornado). We stayed north in hopes of getting into the path of the 70+ dBZ core for in-situ hail measurements. Did encounter some large hail (maximum size was 1.5″). Returned to Denver for the evening


Zonal flow continues over the high plains where some modest upslope remains (although the surface winds are more southeasterly by 0z). Moisture improves significantly by early afternoon with 60+ dewpoints against the Colorado/Wyoming front range with RUC forcast CAPE of 3,000 J/Kg by late afternoon. Thunderstorms should initiate by ~22z in the higher terrain, and (hopefully) move off into western Nebraska panhandle by 0-1z.


Opportunities for higher end severe should be much better tomorrow as modest southwesterly flow finally returns across the western Dakotas and Nebraska. At this point, it appears that south central South Dakota or western Nebraska could be the play tomorrow with strong instability and reasonable winds, although it seems the low level jet that develops later in the evening is displaced a bit too far to the east.

After Thursday, the NAM suggests that the low digs far south into New Mexico by Saturday morning. Wild variances between model fordcast products brings low confidence in any attempts at a long-range planning except that we’ll have southwest flow, and good instability in the plains–and operations should (hopefully) continue through early next week.

Teams should ‘target’ Valentine, NE for planning purposes, with a more defined target decided tomorrow morning.

Denver teams will be departing ~12 Noon today for the cheyenne ridge area for storm initiation by 22z. Plan on a multi-day mission that could exceed 4+ days.