The pattern has finally shifted to one that is unfavorable for classic severe weather in the Great Plains.  My thanks to Dr. Sam Ng for the courtesy of allowing me to tag along and the collaboration. Also to Dr. Scott Landolt and Cameron Redwine for the group collaboration on forecast and target decisions.  Scott also found us lodging each night, and did the lion’s share of the navigation.

(L to R) Dr. Sam Ng, Mr. Cameron Redwine, Dr. Scott Landolt, and Dr. John Monteverdi

Sam and Scott’s class on Storm Observing at Metropolitan State University in Denver, CO yielded a great set of students for this trip.  I was happy to meet all of them.

What We Saw

We held up in Salina and went a little further east, to catch developing storms moving towards Lawrence KS. However, a cell rapidly developed southwest of Russel, KS, about 60 miles to our west. It immediately became tornado warned.

So we decided to drive back towards it since it was moving slowly north east. That decision proved a very very good one.

As we drew closer to intercepting the rain free base, a bulbous lowering developed. And then a very large tornado, between a wedge and a stove pipe, with a satellite tornado on its north side.

When we were within 5 miles or so, the view opened up to a scene of utter beauty and atmospheric violence. (Picture used with permission by Cameron Redwine)

And then we were treated to quite a spectacle.

After 10 minutes or so the tornado shrunk to an elephant trunk with another funnel off to the west (not shown in this picture).

Then a third tornado formed to the north of the original updraft area.

The original tornado continue to shrink to the “rope” stage.

We attempted to stay with the storm, stair stepping across north-central KS. And we saw one more tornado in the distance. But we were never really able to view the storm again while it was actively Tornadic.

So we called it a chase. And on our way back, we were able to see the back sides of the big storms that caused so much havoc in our original target area.

This view of the supercells to the east shows the backsheared anvil with “knuckles” of one east southeast of Salina. A great view as we called it “a chase”.

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Targeting Decision

The boundary left over from the previous evening’s thunderstorms lay over northeastern KS. That cold air had joined with the cold air north of the synoptic scale boundary. This left a beckoning source of low level vorticity in northeastern KS.

This area of high dew points was associated with rich CAPE and little CIN expected in the afternoon ahead of a surface trough between the moisture advection area and the Dry Line, which was too far west to be a player in Kansas.

The continued presence of a southwesterly flow with embedded disturbances also lay over central and eastern KS. The juxtaposition of favorable deep layer shear, CAPE, and low level shear is quantified by the Supercell Composite Parameter. This does not mean that supercells will form in the highest valued areas, but that if thunderstorms do form they have all the ingredients for supercells.

The convection allowing models showed that during the afternoon thunderstorms would begin formig in south-central KS and then move northward towards the boundary, where the low level shear was the most favorable. So we targeted the area in the box drawn on the surface plot above. But note the area of high SCP curling around the northside of the low,

The forecast sounding for the area just east of Salina shown below describes a thermodynamic and shear environment favorable for powerful supercells and tornadoes.

What we saw:

The initial supercell near Brush, Colorado had a wall cloud, a velocity couplet on radar, and then a very brief spin up of a ground circulation underneath a small funnel cloud. At this time, the storm was not pushing outflow, so this was not a gustnado.

This storm became outflow dominant, with a massive hail core. We drove through part of that and measured temperatures that had dropped from 73F to 42F. So we dropped south to a developing storm near Holyoke, CO. It quickly developed a wall cloud and what appeared from our distance to be a tornado.

This storm had wild features, and at one time developed an awesome hail core that descended to the ground. By the way you can see the helical updraft that developed to the right of the view. You’re looking edge on at the vortex tube. And there may have been a brief additional tornado.

The storm became a stacked wedding cake, with beautiful lightning on its northeast flank.

Later on as it came into Imperial, marble to golf ball hail treated our dinner gathering

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Targeting Decision

A weak cyclonic circulation in Nebraska had circulated dew points > 50F into northeastern Colorado. Surmounting this was a strong southwesterly jet.

CAPE values of around 1500 J/kg and 0-6 km vertical shear values of around 40 knots created an environment for long-lived storms, particularly in northeastern Colorado where CIN values would be low or zero by mid afternoon. Low level shear values were just into the range in which mesocyclone tornadoes would be possible. The Hodographs had nice anticyclonic sickle shapes.

So we targeted the area near Limon, Colorado.

What We Saw

Here are the seasoned meteorologists who were collaborating on this chase. Left to Right, Scott Landolt, John Monteverdi, Sam Ng, Cameron Redwine.

This is a panorama movie showing the first cell we chased. It had promise. Here you see the Rear Flank Downdraft cut, the updraft area with a ragged wall cloud, the forward flank rain area, and the outstretched anvil.

The initial storm we tracked in se Colorado looked briefly good. But we left that behind to target a storm southwest of Lamar, Colorado. It had intermittent wall clouds and reports of tornadoes. We did not see any tornadoes…but in these two pictures apparently observers near by the features saw them. The storm was tornado warned.

We tracked the storm northward, but eventually decided it was becoming outflow dominant, which means it was no longer drawing in warm unstable air. Along the way, we were subjected to a convergence of idiotic chasers, including this joker.The radar imagery shows the development of the hook on the storm near Lamar. The radar site was Pueblo, CO, which was to the left of the image. You will note the couplet that developed on the south side of the storm (green next to red on the velocity image) and the associated tornado warming (red quadrilateral).When we got back to Garden City, the storms we had been chasing congealed into a squall line. The lightning would not cooperate when I took this short video.

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Targeting Decision

Today’s surface weather map has a mesolow developing in southeastern Colorado. A synoptic scale stationary front extends northeast of that intersecting an outflow boundary with ongoing elevated convection northeast of that.

At 500 mb, a short wave trough with upwards vertical velocity associated with it is moving through New Mexico. 40-50 knot southwesterly winds are associated with it.

At 700 mb, 10-12C temperatures are found over western KS into the western Panhandles indicating a breakable capping inversion during the day.

Forecast soundings in the area of upslope flow in eastern Colorado and at the eastern edge of the outflow boundary in northwest KS are favorable for supercells. The eastern area is more problematic because of the rapid evolution of the outflow boundary.

CAPE, little to no CIN, deep layer shear favoring both longetivity and mid level mesocyclones, low level shear favoring the development of low level rotation…all are focused in these two areas.

Hence our target is as shown in the box on the surface chart above. I’ve put some other charts below that I will refer to when I have more time.

What we saw

in extreme sw Kansas. As we were driving to the apex of our target area a storm formed there and became a weak supercell.

We drove east and then south to get ahead of the storm and got to the rain-free base. It had several lowering, and also a brief funnel cloud. We also noticed “inflow stingers” coming into the storm at mid levels. But it’s life was brief. Storms to the south rapidly moved northward into the updraft area of the storm and suppressed it. Still, at least we had a chase this first day.

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Targeting Decision

I am currently in Denver awaiting the other members of the group I will be with, including Drs. Sam Ng, Scott Landolt and veteran chaser Cameron Redwine. They will be leading a crew of student meteorologists from Metropolitan State University in Denver.

The morning surface chart shows a stationary front extending from southwest to northeast from extreme northeast New Mexico to Iowa.

South of that boundary high dew points are found through the whole region. There area couple of outflow boundaries that are left behind from last night’s convection. One large old cold pool extends from southwest KS to theTX Panhandle. That is expected to moderate during the day.

Aloft, strong southwesterly winds at 500 mb are expected to overspread the area roughly shown in the triangle above by the afternoon, with wind speeds 40 knots and greater. At 700 mb, the edge of the warm air cap seems to be on the southeastern edge of that triangle. So the Lid Strength index shows a breakable cap over the western OK and TX Panhandles and sw KS.

Underneath the cap southeasterly winds are bringing an air mass with high CAPE lapping at the edges of the cap.

The indices that combine the factors leading to Tornadic supercells are there fore focused in this area.

Forecast soundings plotted through the area are quite interesting. The one above is for a location just northeast of Perryton TX.

So my early thoughts are that the region roughly in the triangle on the surface analysis above would be a target. There is another target in eastern KS that bears analysis…and I’ll look at that too later.

As the pattern in the middle and upper troposphere continues to show an anchored trough in the western part of the United States with southwesterly flow aloft over the Great Plains, it appears that favorable conditions for severe storms will persist through much of the period from May 23 through May 30.

So the first chase day will be be May 25, 2019, and I plan to be in place for that.  The 500 mb height/wind, 700 mb height/temperature, and surface dew point field given above are from the 12 UTC run of the NAM on 5/22/19, forecast for Saturday afternoon 5/25/19.

These show implied favorable wind shear from the surface to 6 km (500 mb winds around 40 knots are greater for storm ventilation and mid level rotation. The surface dew point field shows a dry line punch into north-central Kansas that afternoon.  ml CAPE values (not shown) of 3000-4000 J/kg are substantial. The problem might be the cap…as implied by the 700 mb temperature field shown.  The deep yellow colors extend into KS, with just north-central KS at the edge.

This forecast sounding is for a spot between Salina and Hill City.  All the parameters are great, but you can see the remains of the capping inversion present at 0000 UTC is awful close the parcel ascent curve.  This suggests initiation may be an issue.

 

In any case, the parameters that measure the chances of the supercell cascade proceeding to “conclusion” are suggested to be in place over that area Saturday
afternoon. This shows one such parameter, the Supercell Composite Parameter.  There’s definitely a signal in this preliminary target area.

Beyond Saturday, the GEFS model continues the prospects.  In fact, it has been suggesting what meteorologists refer to as a “synoptically evident” pattern towards Monday, May 27.

This shows a very prototypical pattern for severe weather in the Great Plains.  The 500 mb heights and winds suggest a strong southwesterly jet over the area from Oklahoma northward to southern Nebraska.  And this will overspread ample CAPE (the colors show the chances that CAPE values will exceed 1000 J/kg.

The other set of tea leaves posted here include the Extended Range Tornado Activity Forecasts (ERTAF) from the Victor Genuine group.  The red and orange tiles at the bottom shows the average risk for SCP values favoring tornadoes based upon the average of all 20 ensemble members from the GEFS.   Based upon this, there is confirmation of chasable patterns on the 25 through the 29th or 30th.

 

Well, the pattern collapsed in on itself, despite promise last week at this time. We saw a few great storms, had fun experiencing the local cafes and restaurants.  We had a fun chase with Chuck and Vickie Doswell and it’s always challenging to be forecasting on the fly so to speak!

And there is always the ever present beauty of the Plains.  So long.

Synopsis

Nature didn’t quite change water into wine for us in our target area.  Storms did develop east of Emporia, though.

They were CAPE-starved, though, and although they started out as stout towers, they eventually  became “mushy” and not particularly tall.

One cell initially had a very good look as it approached Louisberg, with an attempt at a wall-cloud.  On radar, there was a weak couplet associated with this area of the storm, and we had hopes for it.  But like the others before it, it’s supercellular motion (which should have been nearly from north to south) changed to translation with the mid level winds, as it lost its structure and rotational characteristics.

We have decided to call it a (brief) “chase” and are planning to depart from OKC tomorrow, 31 May.

Discussion

] The surface pattern in the area of east central KS expected to have  favorable shear this afternoon is complicated by several outflow boundaries. One of those is over east turn portions of Oklahoma  and the other is in north central Kansas. We are targeting the area south of Topeka in and around Emporia Kansas where the convection allowing models are  initiating new storms around 3 PM Central daylight Time. The models are also showing isolated cells with rotation as  as they move southward into east central Kansas.

The outflow boundary in southern Kansas really should be located in the trough evident in the isobars.

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Looks like the risk of supercells reappears in Kansas tomorrow, May 30.  So we will use this day to reposition northward.  On the way our initial plans are to visit the site often Branch Davidian Complex, the Twistex El Reno Tornado Tragedy memorial, the memorial to the Oklahoma City bombing in 1995, and, perhaps, the National Weather Center.

Summary

We crossed into Texas just north of the cold front that was slowly sliding southward.

As we had lunch, thunderstorms erupted along and just north of the boundary.  We were targeting the area south of the boundary where thunderstorms would be rooted in the boundary layer. And in that region deep layer vertical shear was favorable for supercells.    Storms north of the boundary were strong but disorganized.  We drove through several intense cores with staccato cloud to ground lightning.

South of the cold front and west of the outflow boundary coming out of Louisiana, there were isolated cells that had organization and seemed to have brief supercell structures.  In fact, one developed into an HP supercell about 20 miles southeast of us, but we did not want to drive through the core to get to it, nor did we like the storm motion, which was fast and moving towards Louisiana. The storm eventually had a Tornado Warning on it.

We spent the overnight in Waco as other thunderstorms rolled through that city.

Discussion

Well we are out here, so might as well pull out all the stops. Our prior target of west central TX disappeared with the reality of the actual observations this morning. so we will drift to ne TX. CAPE and shear there. Outside risk of a supercell there. The outflow boundary there can help with iniation, but there is considerable CIN to its east. The forecast sounding and hodograph is for a location about 50 miles se of Dallas.