Tuesday, October 22, 2019

October 20, 2019 Dallas, Texas tornadoes after dark - no deaths or injuries!

Wow... it has been an active several days for tornadoes this past weekend in October (see my recent post about the EF2 tornado in Florida from T.S. Nestor).

As anyone watching news the last couple days knows, Sunday evening (10/20/19) saw several tornadoes in the Dallas, Texas area after dark, including one EF3 that struck the North Dallas-Richardson corridor around 9 pm CDT (top image above).  Another of EF1 intensity hit the Rowlett, Texas area a little later from the same supercell storm (middle and bottom images above, note the very impressive power flash!) .

**** Update 10/24/19:  Additional tornadoes have been surveyed by NWS Dallas/Ft. Worth in recent days, including a short-track EF2 tornado in Garland just before the Rowlett tornado mentioned above, and an EF1 in Rockwall after the Rowlett tornado. These tornadoes were from the same supercell that produced the North Dallas and Rowlett tornadoes. ****

No one wants to see damaging tornadoes in a metro area, especially after dark, but it is great news that there were no injuries or deaths reported in the Dallas area, largely due to a tornado watch and good warnings by NWS.

I've had several people ask me, "Isn't that odd for this time of year?"  Not really.  Based on  statistics over the past 25 years, Texas sees an average of around 9 tornadoes in October each year, and 58 tornadoes occur on average nationally in October.  So it does happen with the right meteorological settings.

Sunday evening's surface map (below, 7:00 pm CDT) showed a dryline west of Dallas with moist air (dew points upper 60's to near 70 deg F) that had moved back into north Texas on south winds during the day, with the deepest moisture from the Red River southward:

Tornado parameters from the SPC mesoanalysis at 7:00 and 8:00 pm CDT (below, enhanced energy-helicity index or EEHI, and the effective-layer significant tornado parameter or STP) suggested that combinations of instability and wind shear were quite supportive of tornadoes over the Dallas area as storms were developing rapidly and becoming supercells to the west:

The northernmost supercell on the 7:00 and 8:00 pm SPC images above produced the damaging EF3 tornado in north Dallas around 9:00 pm CDT, followed by the Rowlett tornado just after 9:30 pm CDT.  In fact, the warm sector setting east of the dryline over north Texas was so supportive of tornadoes that no boundaries were needed to help produce tornadoes, unlike last Friday evening in Florida.

A forecast of instability and wind shear from the RAP model sounding at Dallas a couple hours before the tornado shows excellent combinations of CAPE (instability), low-level wind shear (0-1 km storm-relative helicity or SRH), and deep-layer wind shear (0-6 km shear) were in place, with not much convective inhibition (CIN) in the environment.  These factors were all supportive of significant supercell tornadoes if discrete storms developed:

It is worth noting that the High-Resolution Rapid Refresh (HRRR) model from earlier on 10/20/19 (see below) was not successful in forecasting convective storms and supercells over the Dallas area that evening, although it did forecast storms in Oklahoma, and over west central Texas:

So, even with our often impressive automated model guidance of convective storms these days, the human forecast element is still greatly needed!

In my post this past weekend about the Lakeland, Florida tornado, I pointed out from radar images how that supercell behaved somewhat like a typical Plains tornadic supercell with one tornadic mesocyclone occluding and dissipating, while a new one formed to its east-southeast.  That same evolution was seen Sunday evening with the North Dallas and Rowlett tornadic mesocyclones, as is evident on the reflectivity and storm-relative velocity images below:

Looking at the larger synoptic picture, the NAM model 500 mb forecast for that evening showed a very large and strong midlevel trough (dashed red line below) moving through the Central Plains, with a typical "branching" jet pattern ahead of the trough.  This area of dynamic forcing overspreading the returning low-level moisture through the Plains was where the bulk of severe weather occurred Sunday evening and Sunday night:

One final note... The north Dallas tornado touched down 15-20 miles east-northeast of AT&T Stadium where the Dallas Cowboys were playing at the time of the tornado.  Although the soon-to-be tornadic North Dallas supercell stayed well north of the stadium, it is nevertheless very fortunate that the EF3 tornado did not directly impact the thousands of people at the game!

- Jon Davies  10/22/19

Saturday, October 19, 2019

October 18, 2019: A strong Florida supercell tornado with Tropical Storm Nestor

It's been awhile since I posted about a recent tornado case, so I pulled together some graphics about the meteorological setting with last evening's EF2 tornado after dark (see images above) near Lakeland in west-central Florida east of Tampa.  This tornado was associated with a tropical storm (T.S. Nestor, centered well out in the Gulf of Mexico at the time).  But instead of the supercell being embedded within an outer band of storms as with many tropical systems, it was discrete and occurred near an east-west stationary front, behaving in some ways more like a Plains supercell storm.

The stationary front is shown on the surface map below at about 0300 UTC (11:00 pm EDT), about the time of tornado development near Lakeland:

There was not a tornado watch in effect at the time, probably because the environment most supportive of significant tornadoes appeared to be out in the Gulf of Mexico closer to the center of Nestor, as indicated on the 0300 UTC (11:00 pm EDT) SPC mesoanalysis graphic below using the effective-layer significant tornado parameter (STP):

However, low-level wind shear (0-1 km storm-relative helicity or SRH) and low-level CAPE (0-3 km MLCAPE) on the SPC mesoanalysis at 11:00 pm EDT (below) were notably co-located together over west-central Florida near the stationary front:

This was in the same area where a supercell storm (shown in later graphics down below) was moving north-northeast near and across the stationary front.  The combination of these two low-level parameters near the ground probably facilitated low-level stretching and tilting of environmental vorticity into the storm's updraft to produce strong low-level rotation, even though total instability and numerical shear/instbility combinations did not appear especially large.  The stationary front likely provided additional low-level shear to add to the background environment as the supercall moved across the front.

A 3-hr forecast sounding from the RAP model at Lakeland valid at 0300 UTC (11:00 pm EDT) also suggests that the environment was supportive of supercell tornadoes:

Notice above that the red CAPE area extended only up to around 30,000 ft MSL (300 mb), with the "fattest" area of CAPE located near 10,000 ft MSL (700 mb), rather low in the sounding relative to the ground.  This is similar to many "cold-core" low-topped supercell  environments that support tornadoes in the Plains, suggesting significant upward air acceleration in low-levels, resulting in strong vertical stretching of low-level vorticity near the ground, even though total CAPE does not appear unusually large.  

So, the vertical distribution of CAPE near the stationary front was probably important in this case.  Also, deep-layer shear (0-6 km shear) near 30 kts on the sounding above, while not overly impressive, was just enough to support supercells and tornadoes.

This discrete supercell associated with a tropical system also behaved more like a Plains supercell on radar.  The Tampa radar reflectivity and storm-relative velocity images zoomed in below show the original tornadic mesocyclone northwest of Lakeland occluding and dissipating (drifting toward the back side of the storm while wrapping in rain-cooled air), while a new mesocyclone formed to its east and southeast, similar to the evolution of many Plains supercells:

Thankfully, even though the EF2 tornado was on the ground after dark for 9 miles and was nearly a third of a mile wide at times, there were no injuries due to timely warnings from NWS Tampa.

- Jon Davies  10/19/19

Saturday, August 17, 2019

Tornadoes in Kansas in mid-August! 8/15/19 in northeast Kansas

Supercell tornadoes undoubtedly can occur in Kansas in early to mid-August, but they don't happen that often, and even as a native Kansan, I've never seen one.  That changed on Thursday, August 15 when a well-established supercell (see Shawna's photo above) in northwest flow produced tornadoes southeast of Manhattan and southwest of Topeka.

Here's a map showing the approximate location of three tornadoes that occurred with the supercell pictured above in the 7:00-9:00 pm CDT time frame:
(A fourth brief tornado occurred with a separate trailing supercell after 9:00 pm CDT.)

I was chasing with James Skivers and my wife, following the southernmost supercell that developed northwest of Manhattan and moved sharply southeast across Wabaunsee County, Kansas (KS).  We missed the first brief tornado (EF0) from this supercell near the western Wabaunsee County line south of I-70 around 8:12 pm CDT when we were driving south to stay ahead of the storm through a low area with trees.  Here's Brian Miner's cool photo of the full supercell base and this first tornado, all in the same shot:

The second tornado (rated EF1 by Topeka NWS) was longer-tracked near dark, southwest of Alma, KS and northeast of Alta Vista.  The image of this tornado below is from Shawna's video, backlit by lightning looking east-northeast, with the rear-flank downdraft (RFD) and gust front visible:

A third brief tornado (EF0, below, looking north and also backlit by lightning) occurred near the time the second tornado was ending, back to its northwest under an occluded mesocyclone behind the one that generated the EF1 tornado:

A separate supercell back farther to the northwest produced a brief EF0 tornado after 9:00 pm CDT east of Alta Vista (not shown).

The satellite image below, with relevant features superimposed, shows the setting just before 7:00 pm CDT (0000 UTC 8/16/19):

Note the stationary front and outflow boundary (from earlier storms that moved into northern Missouri) close together over northeast Kansas near Manhattan and Topeka. Winds from the low-level jet (LLJ, around 850 mb or 5000 ft MSL) were impinging on and overrunning these boundaries, helping to initiate storms northeast of a "cap" that was inhibiting convection to the southwest.

Three different supercells are visible in the image above (black arrows show their southeastward motion), but only the southernmost cell near Manhattan was able to access the most unstable air along and south of the boundaries by virtue of its location and motion, probably a big factor in its ability to produce tornadoes about 90 minutes after the time of the satellite image.  The low-level jet was also increasing near dark, as is typical, enhancing low-level shear supportive of tornadoes.

The SPC mesoanalysis depiction of the effective-layer significant tornado parameter (STP) at 8:00 pm CDT (shortly before the tornadoes) showed large values supportive of tornadoes along and near the aforementioned boundaries in northeast Kansas (the enhanced energy-helicity index, an experimental parameter, is also shown):

Notice that, even though these tornado forecasting parameters appeared "favorable" over a rather large area extending north of the boundaries, the tornadoes were limited to the air mass south of and near the boundaries.  This suggests the importance of following the location and evolution of relevant boundaries in forecasting/nowcasting tornado potential, rather than just relying on parameter "bulls-eyes".

Also, here's the NAM model 500 mb forecast (winds at roughly 18,000 ft MSL) showing the northwest flow driving into Kansas, a little unusual that far south in mid-August, and the reason the supercells moved southeastward to the right of the midlevel flow:

Two shortwave troughs are marked on the forecast above (thick dashed red lines) showing a lead shortwave associated with the morning and early afternoon storms that moved from northeast Kansas into northern Missouri, and a fairly strong trailing shortwave not far behind crossing Nebraska.  Often, morning and early afternoon storms leave subsidence (sinking motion) and a "worked-over" air mass in their wake, reducing the chances of severe storms behind them.  But that was not the case here, with another shortwave immediately behind generating upward motion and intensifying low-level winds converging on and overrunning the surface boundaries.

All in all, an extremely interesting case for mid-August in Kansas!

- Jon Davies  8-17-19

Thursday, August 8, 2019

Updated map and images of May 28, 2019 EF4 tornado in northeast Kansas

It's been over 2 months since the long-track EF4 tornado in northeast Kansas (KS) on May 28 that just missed the main population of towns like Lawrence, Linwood, and Bonner Springs KS.

Some interesting video has surfaced since May 28.  I thought it would be useful to correlate some images of the tornado with a newer map I put together (above) that shows the relative width of the tornado path (> 1 mile near Eudora & Linwood) at various points from my own survey.  The smaller tornado that occurred earlier and merged with the larger one as it formed southwest of Lawrence is also shown.

The map above shows image locations (in red) by image number as discussed below, along with direction of view.

Image 1 below (from Quincy Vagell's video) shows the wet portion of the storm in southwest  Douglas County looking west around 5:57 pm CDT where a small EF1/EF2 tornado was embedded that struck Silver Lining Tours (SLT).   The new mesocyclone from which the large EF3-EF4 tornado developed about 10 minutes later is also visible north of the rain-wrapped area concealing the smaller tornado:

Image 2 below (from video by Robert Reynolds) shows this smaller EF1/EF2 tornado emerging out of the rain near Lone Star Lake around 6:05 pm CDT, looking east about 1/2 mile away.  This is the same tornado that struck SLT 2 to 3 minutes earlier:

Image 3 below (from video by Dalton Coody) shows the large tornado shortly after forming southeast of the town of Lone Star (in Coody's video, it is only visible briefly before rain wraps around it).  This was at roughly 6:10 or 6:11 pm CDT, after the merger of the smaller tornado with this larger one as it was developing:

Image 4 below (from video by Jack Miller) shows the HP supercell at about 6:12 pm CDT looking southwest from the south side of Lawrence.  The tornado, visible in the Coody video, is hidden by rain wrapping in from the southeast (a wet rear-flank downdraft or RFD):
Image 5 below (from video by Matt Grantham) jumps ahead to near Linwood KS around 6:35-6:40 pm CDT, looking west along Highway 32 west of Linwood.  The tornado was about a mile wide (!) at this point, but somewhat visible even though still wrapped up in rain:
Image 6 (from video by Cybil Walters) is from a housing development north or northeast of Linwood, and shows suction vortices (smaller intense "swirls" within a larger tornado) clearly visible.  This was around the time of EF4 damage near Linwood, and suggests why some houses north of Linwood were totally demolished, while others were still standing with mainly roof and outer wall damage:

Image 7 (from video by Matt Grantham again), looking southwest from northeast of Linwood around 6:40-6:45 pm CDT, also shows the tornado at about the time of EF4 intensity, although it is still somewhat difficult to see from some rain-wrapping:
The more I look at the path of this large tornado, the more I'm struck by how very fortunate it was that it did not directly hit any population centers, including the Kansas City metro area!

The images in this post also show how difficult it was to see this tornado (and the smaller one before it), as they were both associated with a large high-precipitation (HP) supercell.

Spotters and chasers BEWARE such storms, especially when they are moving faster than 30 mph... give them a very wide berth!

Thanks to Robert Reynolds, Quincy Vagell, Dalton Coody, Jack Miller, Matt Grantham, and Cybil Walters for their video images, and thanks to Rick Schmidt and Eric Lawson for pointing me to additional documentation and information.

- Jon Davies  8-8-19

Monday, July 1, 2019

A surprise photogenic tornado in southwest South Dakota on June 29, 2019

Similar to the unexpected and stunning Laramie tornado last year (see here), June 29 saw a striking and widely-photogrpahed tornado (photos above) that lasted around 40 minutes west of Martin, South Dakota.  It occurred mainly over open fields, and so was rated only EF1, although it may have been more intense.

The Storm Prediction Center (SPC) had outlooked a 5-10 % chance of tornadoes over parts of North Dakota on Saturday, but nothing over southwest South Dakota (SD).  Why?  The reason is that this tornadic storm was not a typical tornadic supercell storm, and like the Laramie tornado, was difficult if not impossible to forecast.

Looking back at Saturday afternoon June 29, there were certainly doubts about whether storms would even develop over SD - see the model radar simulation forecasts for mid-afternoon below:

Given these model radar forecasts and very high cloud bases expected (around 2500-3000 meters above ground, not shown) along with little if any low-level wind shear, no forecaster would anticipate a long-lived tornado hours in advance within such a setting.  Tornadoes from purely supercell processes typically occur with cloud bases under 1500 m and at least some low-level wind shear; it is unusual for tornadoes to occur when temperatures are near 100 deg F, which guarantees high cloud bases.

How could such an environment support a long-lived tornado?  Some important ingredients can be seen coming together just before the tornado occurred. 

Here's the surface map at 3:00 pm CDT, roughly 30 minutes before the tornado.  Notice the northeast-southwest boundary/trough over southwest South Dakota:

A storm or two did begin to form on this boundary shortly before 3:00 pm CDT (see satellite image below) with strong surface forcing and convergence on the boundary.  The very hot temperatures (around 100 deg F, see heat axis on map above) also helped to break through a stout layer of warm air aloft (700 mb temperatures > 14 deg C, not shown) to initate a storm.

SPC mesoanalysis graphics at 3:00 pm CDT also showed heating and steep low-level lapse rates poking into southwest SD along the boundary, along with large surface vorticity (light blues lines) along the same boundary:

This combination of strong low-level lapse rates and vorticity (slowly "spinning" air) along the boundary apparently set the stage for rapid vertical stretching beneath any storm updraft that could form and establish itself directly over the sharp boundary.

Typical supercell tornadoes require significant low-level wind shear (a rapid change in wind speed and direction with height) in the lowest 1 or 2 km.  But this was definitely not a typical case, as there was very little low-level wind shear (storm-relative helicity, or SRH) over southwest SD on SPC mesoanalysis graphics at 3:00 pm CDT:

However, the storm updraft essentially "locked on" to the sharp wind shift boundary to provide the necessary vorticity ("spin") to stretch vertically into a tornado, in lieu of significant SRH/low-level wind shear (again, note the large surface vorticity along the boundary on the earlier SPC graphic).

In the 2nd panel of the graphic immediately above, also notice that there was just enough deep-layer vertical wind shear (25-30 kt) to support a supercell storm.  So, instead of only brief updraft stretching from steep lapse rates along a boundary, the storm became more organized and long-lived through interacting with this deep-layer shear.  Indeed, it took on supercell characteristics with a hook-shaped echo and clear rotation detectible from a distance on radar (see radar inset below):

Thus, the tornado was able to keep going for quite awhile.  With the contribution of non-supercell processes (stretching of boundary vorticity in a steep lapse rate setting) and not a lot of rain falling from the storm (see photos at top), the high cloud bases and potential evaporative cooling did not seem to be a negative factor.  The tornado was also quite visible from a distance due to these same high cloud bases.

Because this setting combined both non-supercell ("landspout") processes with supercell characteristics, I would call this a "hybrid" tornado event.  WIthout the boundary and the storm directly linked to it, the tornado probably would not have occurred in the absence of notable SRH.  But with enough deep-layer shear to support a supercell, that was also part of the "recipe".

Farther north (not shown), tornadoes were expected over North Dakota on June 29, bur did not occur.   This was probably due in part to the slight cooling influence of an outflow boundary from morning storms.   Without as much surface heating, a strong layer of warm air aloft (temperatures around 14 deg C at roughly 10,000 ft MSL) helped to "snuff out" evening storms that managed to form over south-central North Dakota before they could really mature and take advantage of increasing low-level shear/SRH as nighttime approached.

Believe it or not, another tornado from processes similar to those on Saturday formed again on Sunday afternoon (June 30) over south-central South Dakota near the town of Burke, along yet another sharp boundary with strong heating and ingredients lining up enough to support a tornado:

But to reiterate, such tornadoes are almost impossible to forecast hours in advance because everything has to come together just right, and typical supercell tornado forecasting factors (such as SRH and lower LCL heights) don't work with these type of "hybrid" tornadoes.  Yet when the proper ingredients do come together, these "hybrid" tornadoes can be quite spectcular visually!

- Jon Davies  7/1/19

Wednesday, June 5, 2019

A merger of two separate long-track tornadoes in northeast Kansas on May 28, 2019 !

I wasn't planning on posting anything further about the Lawrence-Linwood tornado and the Silver Lining Tours (SLT) encounter with a separate rain-wrapped tornado, thinking enough has been said already.

However, the National Weather Service in Topeka today released an addendum to their original survey identifying and adding a new tornado (EF2) that was previously unreported in southwest Douglas County, Kansas.  This was the rain-wrapped tornado that struck SLT, rolling two of their vans, and was located at the time of the incident within the rain-filled rear flank downdraft (RFD) of the developing mesocyclone to its north that gave birth to the large Lawrence-Linwood tornado.

As I suggested in my prior post, this additional tornado was not a satellite tornado, but a separate tornado that had not yet been confirmed or reported previously.  It ended up merging with the developing large Lawrence-Linwood tornado, a complex and fascinating evolution and interaction.

Here's a map I constructed by putting together NWS Topeka and NWS Kansas City survey maps of the two tornadoes.  This shows the full tracks (nearly 43 miles total) and where the two tornadoes merged:

Roger Hill was kind enough to share his video with me privately, shot while SLT was retreating to the south away from the developing Lawrence-Linwood mesocyclone and what they thought was away from danger.  With Roger's permission, here's a panoramic image I put together from his video as they were pulling away to move south:

You can clearly see the visual mesocyclone to their west-northwest (at right), also the focus of several other chaser videos online.  But also notice the advancing rain-filled RFD coming up from their south (center of the image) that unbeknownst to them contained a hidden and unreported tornado that no one yet knew about.

Most spotters and chasers are taught to stay southeast of northeastward-moving mesocyclones (areas of organized rotation in supercell storms) to stay safe.  So, SLT thought they were doing the careful thing to head back south to Highway 56 and follow the primary mesocyclone from a safe distance.

Complaints and accusations online (Facebook, Storm Track, etc.) have focused on the question, "What was SLT even doing in the bear's cage?"  Well, that question kind of misses the point when the room becomes dark and you don't even know an additional bear's cage is there after you're already steering clear of the main bear's cage that you know is behind you.

The tornado merger in this case was very similar to the Hesston-Goessel, Kansas tornado merger I studied on March 13, 1990 that led to an EF5 tornado:

The difference is that the 5/28/19 merger took place hidden in rain within an HP storm, while the Hesston-Goessel supercell was a classic non-HP storm and very visible.  In fact, we might not have even known about this merger had SLT not had their encounter!

To my knowledge, this is the first time a merger of two separate medium or long track tornadoes has actually been documented within an HP supercell, although similar mergers have undoubtedly occurred but not been documented.  This case certainly deserves further study from several perspectives.

Thanks to meteorologist and severe storms expert Greg Stumpf for being astute enough to recognize the similarity to the 1990 Hesston-Goessel merger/interaction, and mentioning it on Facebook already several days ago.

- Jon Davies  6/5/19

Sunday, June 2, 2019

Radar data and the Silver Lining Tours incident 5/28/19 south of Lawrence, Kansas

Roger Hill and Silver Lining Tours (SLT) have been getting a bunch of heat on social and other media for two of their tour vans getting rolled during last Tuesday's tornadic storm south of Lawrence (see my post about the weather setting here).

I'm certainly no radar expert, but based on radar data I went through carefully on Saturday, I do think everyone needs to chill a bit before passing judgement about Roger and the tour group being "too close".
A discussion on Storm Track forum has been looking at the early stage of the Lawrence tornado's track via Topeka (TWX) radar, and there was definitely some complex evolution going on with the storm.   This data does suggest that the main tornado was developing a couple miles to the north of SLT's position around the time they were struck by strong winds or some sort of 2nd rain-wrapped circulation coming up from the southwest in an unusual location, which matches statements by Roger.

I also looked at radar data saved from the Kansas City radar (EAX, a little farther away), and can make out two separate circulations at 6:00 pm CDT in the storm-relative velocity field:

This was just before the large tornado developed at 6:05 pm CDT, with the 2nd smaller circulation visible closer to Highway 56.  This 2nd circulation was located about 2 miles (check the scale on the graphic) to the south or south-southeast of the developing large tornado.

Base reflectivity at the same time (below) showed the large developing tornado circulation to be within some rain, with the 2nd circulation located southward within the wet rear flank downdraft (RFD) that was beginning to surge east with this large HP supercell:

Discussion on Storm Track has highlighted this additional circulation to the south of the axis along which the large tornado formed, based on radar images and other information.  Here are radial velocity images from TWX (courtesy of Jeff Snyder on Storm Track) at 5:56 pm, 6:00 pm, and 6:04 pm CDT.  I've marked the locations and tracks of the two circulations.  Notice that it appears the southern circulation moved right over the location where the SLT incident occurred, which lends credence to Roger's description of the incident (click on the image to view it larger):

Dan Robinson on Storm Track put together a graphic suggesting the evolution of the two circulations discussed above.  Here it is, a rather complex evolution prior to the start of the large tornado, with a red "X" marking SLT's location:

Quincy Vagell was shooting video at about 6:00 pm CDT from near the location of the SLT incident,
looking toward the north-northwest:

Notice the lowering visible to the northwest (in spite of rain), which is probably the developing circulation and feature that spawned the large tornado at 6:05 pm, matching what Roger and SLT say they were watching from the southeast.

Quincy describes on Storm Track a "bluish" rain curtain that was moving up from the southwest behind him and to his left.  This was probably the wet RFD containing the small embedded circulation closer to Highway 56 that was not visible, and may have been what hit SLT.

To give some scale and context, I'll mention that my wife Shawna and I watched last year's Tescott, Kansas EF3 tornado on May 1, 2018 (a "classic" non-HP supercell) develop from a distance of about 2 miles to our northwest and north:

This was a similar distance and position to what Roger and SLT had on 5/28 relative to the lowering that they could see to their northwest, which appeared to spawn the large Lawrence tornado a few minutes later.  But, with the wet RFD curtain coming up from the southwest, there was no way to see the 2nd circulation coming with it (from an unusual location within the storm) as they drove back south toward Highway 56 in order to head east and follow the storm from what they thought was a safe distance.

As I mentioned in my prior post, my wife Shawna and I got caught in a somewhat similar surprise situation (strong surging wet RFD winds from the southwest, south of a large tornado) with the El Reno storm in 2013, even though I have years of experience chasing storms as a meteorologist. Luckily, we managed to drive out of the RFD winds without incident.

I think what has sparked accusations of being "too close" in this situation is the characterization of the 2nd / southern circulation shown in the radar images above as a "satellite" tornado, something that implies being really close to a larger tornado.  In fact, this 2nd circulation was separated from the developing main tornadic circulation by at least 2 miles or more, until it moved toward the developing large tornado after striking SLT.  As such, it seems part of a complex evolution that gave birth to the tornado, and not a true "satellite" tornado.

I talked to Roger briefly on Saturday, and know that he is very shaken and more than a little confused by the evolution of what happened last Tuesday.  I think we should all give him the benefit of the doubt on this event.

He and I also talked about swearing off HP storms in the future.... they often surprise and do the dangerously unexpected.

Looking at the bigger picture, maybe spotter and chaser training should start focusing more on large HP storms as a special case with elevated dangers, emphasizing the possibility of wet RFD surges and dangerous winds as an additional hazard south and some distance away from a rain-wrapped tornado.  And, maybe training should teach and emphasize, for safety's sake, that spotters and chasers give large HP storms a much wider berth than what would seem necessary with storms that are more "classic" in nature.  Large tornadic HP supercells are complex and visually challenging, even for experienced spotters and chasers.

Shawna and I are incredibly glad this did not turn out to be another deadly situation, and that everyone with SLT survived.  That’s what's most important.  Just my two cents worth…

- Jon Davies  6/2/19