This is a short clip of the video we shot in west Texas overnight. Today (Monday) we will be staying close to the MX/TX border in hopes for more supercell action!

A significant rainfall event is ongoing across south Alabama. A daily record of over five inches has already been recorded in Mobile. Rainfall totals will continue to rise through the night. In fact, hourly doppler estimates have been as high as four to five inches per hour with stronger storms. The following video reveals some of the most extensive flooding that occurred this evening. This event will have to be monitored through the night and into tomorrow.

SPC has outlined parts of the Central and Southern Plains for a Slight Risk of Severe Weather today. The biggest threats will be large hail and the possibility for a few tornadoes, particularly in the Southwest KS, OK Panhandle, and TX Panhandle region. A shortwave trough ejecting out of the four corners region will quickly become negatively tilted tomorrow afternoon/evening. Negatively tilted troughs are often very conducive for severe weather because they induce stronger cyclogenesis (i.e. the resulting surface low that forms is stronger and deepens more rapidly). Below is an image of 250mb wind and ageostrophic wind vectors. Without getting too technical the vectors essentially show where the upper level divergence is strongest (vectors pointed in opposite directions or away from an area) and upper level convergence is strongest (two vectors pointed towards one another).

Furthermore lee-side troughing from Westerly flow over the Rocky Mnts. will further aid in cyclogenesis and pressure falls.

Although a strong Low-level jet is not anticipated throughout the day, strong low level moisture return is still anticipated. In fact, models have been struggling with the northward advection of moisture/dewpoints and have been underestimating them. 60-65 dewpoints can be expected across much of the slight risk area. Additionally, this moisture return combined with a cooling temperature profile aloft, will aid in creating an unstable atmosphere. Convective Inhibition will be strong throughout most of the day preventing convection from developing until late afternoon or evening.

Taking a look at shear profiles, they aren’t overly impressive but do appear conducive for supercells. Bulk shear will be >40 knots and hodographs are exhibiting some clockwise curvature.

Looking ahead to this time last year…There was a high risk issued today for parts of the Mid-South including a PDS Tornado Watch. This was a precursor to what would become one of the largest Tornado Outbreaks in U.S. History: April 27 Super Outbreak. More will be posted today on some of the precursors to the Super Outbreak and how all the necessary ingredients fell into place for a Catastrophic Event.

Great Warnings and Model Struggles

SPC did an outstanding job forecasting this event over a week in advance. Furthermore, the warnings (the day of) were very efficient and accurate. The NWS recently instated new warning text changes that proved to be very effective! This included more aggressive wording and a more detailed threat assessment for each individual storm. While many of the storms hit low populated areas, this new warning text wording likely still helped save lives!

I want to briefly mention that the models did a great job forecasting the overall synoptic (large scale) environment for Saturday. However, they struggled greatly in the depiction and evolution of convection. This shouldn’t come as huge surprise since convection remains one of the biggest struggles for models to this day. Models simply don’t have enough resolution to resolve many of the small-scale features that drive convection. Furthermore, even the higher-resolution models can’t resolve certain features and don’t solve the issue of limited observations input to the model. Also, high-res models commonly struggle in “weaker forcing” scenarios such as Saturday’s Outbreak. Basic forecast reasoning was that despite models not developing much if any convection, supercells would still develop due to a weakly capped environment. The HRRR was one of the only models that at least partially gave a correct depiction of what actually occurred (at least prior to the 00z runs the night before).

Chase Recap

Chase members Jason Moreland, Ryan Beesley, and Trey Alvey started the day near Oklahoma City. The initial morning target was North-Central Kansas and Southern Nebraska. Supercells were expected to develop earlier in this area have better areal coverage. By late morning storms began rapidly developing in Western Kansas aided by a weak upper level impulse. Overall, the environment was weakly capped so it didn’t take much to trigger storms with a primed atmosphere.

We drove north and intercepted our first tornado warning of the day near Bunker Hill, Kansas. Conditions were very ominous with 40+mph inflow and very low cloud bases. With junk convection all around the storm it quickly became “High Precipitation” making visibility very poor from a chaser standpoint. We quickly aborted this storm and blasted southward in the expectation that developing supercells would be “Classic”.

One particular storm was intensifying just to the Northeast of Dodge City, Kansas. This storm became tornadic as we were approaching and we observed a rope tornado from the initial development. After the initial low-level mesocyclone developed and occluded, subsequent development occurred rapidly. We observed numerous brief tornadoes including the Photogenic Elephant Trunk tornado from this storm. Also, of note this particular storm was not very impressive in radar appearance. Furthermore, it wasn’t even Tornado Warned at one point, despite the fact it was continuously producing brief tornadoes. Eventually this storm moved into more stable air from the earlier morning convection further north and began to weaken.

Then, we decided to drop south on a supercell that was producing tornadoes to the South of Great Bend. This storm rapidly tightened up and began producing a wedge tornado. Due to poor contrast at the time we weren’t 100% certain that we were in fact looking at a wedge tornado. Many times rain shafts get mistaken for tonadoes; in this case we mistook the tornado for a rain shaft. Needless to say, we overshot the storm too far to the South as well due to poor road options. From there we began to play catch up and had to get back ahead of the storm on I-135. Fortunately, storm speeds were manageable and we had great visibility on the storm once again near Assaria. We witnessed the first initial Wedge Tornado become a Stovepipe and rope tornado. The initial tornado occluded but a new low level mesocyclone developed within minutes and began producing a multi-vortex tornado as shown below. This tornado fortunately occluded just before reaching Salina and the new meso didn’t produce until on the outskirts of town. The storm then proceeded to produce two more tornadoes including another photogenic “Stovepipe” Tornado.

As that storm weakened it began to get dark so we decided to start heading south in the direction of home. We had a long drive through the night back towards Mobile ahead of us! On the way back we intercepted another supercell Southwest of Salina that was reported as producing a Large tornado. We did witness numerous power flashes but did not see a tornado and were in fact fairly certain there was NOT a Tornado on the ground. All in all we saw over 9 Tornadoes on a day that we will not soon forget!

A Look Ahead

We’re on pace for half the number of tornadoes this April from last April; however, we’re still on pace to have an above average year in terms of tornadoes. The biggest difference from last year is how much further north the severe pattern has shifted earlier. I can’t completely rule out the Southeast but with no significant severe weather looming in the next couple weeks due to the pattern across the U.S., things are looking up for many areas that got hammered last year. With the coldest air much further north this year in Canada the strongest thermal gradient is also located in this area. The jet stream likes to follow the strongest thermal gradient, meaning the mean jet position is already beginning to shift well north this year. Furthermore we’ve been in a La Nina so this isn’t all that uncommon with strong ridging dominating most of the Southeast. Essentially the ridging to the Southeast and Jet retreating further north means the bulk of severe activity should shift north as well.

Over 120 Combined Tornado Reports have been totaled from yesterday’s tornado outbreak. 28Storms chase team intercepted at least 8 tornadoes across Kansas during the afternoon and evening hours! Below are a couple pictures of the tornadoes and the video. A full chase summary will be posted tomorrow!

A Tornado Outbreak will likely be well underway within the next 3-6 hours across Oklahoma, Kansas, and Nebraska. The SPC has issued a very large High Risk area encompassing parts of all 3 states! As a very strong mid-upper level jet streak continues to prograde eastward it will rapidly deepen a surface low pressure area on the lee-side of the Rockies. This combined with height falls and an increasingly moist/unstable warm sector will make way for robust supercell development late this afternoon and evening. Below is an image of the Significant Tornado Parameter showing values through the roof. All supercells will have the capability of producing strong/violent Tornadoes. The biggest question mark at this point is convective coverage and initiation. Many models have been struggling to break out much qpf/convection; however, some of the more recent short range models are increasing coverage. Furthermore, models likely aren’t picking up on the subtle forcing that will be able to initiate convection in the presence of weak capping. Overall, coverage looks much more isolated across Southern KS/OK; however, as mentioned before any storms that form will be very dangerous. The highest threat and coverage overall looks to be in Northern Kansas and a large portion of Nebraska. 28Storms chase team is headed north into KS/NE and will be streaming live throughout the afternoon!

28storms chase team embarked on a 26 hour drive/storm chase yesterday! The trip began on Wednesday night when we left Mobile during the evening. We drove through the night and were able to reach our initial target near Liberal, Kansas by early afternoon. After examining the latest data, it became apparent that weak forcing and limited upper level support would confine the threat to NW Kansas and SE Nebraska near the dryline/warm front intersection. Also, the low-level shear, while abundant all along the dryline, was most significant in this region. We reached Northwest Kansas around 4PM to a rapidly developing cumulus field. Storms struggled for the first several hours but eventually were able to break the cap and become sustained supercells. We managed to intercept the only tornado warned supercell in far NW Kansas/SE Nebraska, and we witnessed multiple rotating wall clouds and funnel clouds as the supercell cycled through multiple occlusions. Below is some of the video we managed to capture from the day.

Meanwhile, a Multi-day Severe Weather Episode is well underway across the Plains. Tornadoes appear likely today and tomorrow with the threat of strong/long-lived tornadoes. SPC has a 10% hatched tornado threat for today across Western Oklahoma. Yesterday, one of the limiting factors was a lack of upper-level support/shear. Today, as the upper/mid-level jet max continues to overspread the region, a much better overall shear will be in the place. Tomorrow looks like the most Significant Tornado Outbreak for the Oklahoma/Kansas region since at least the May 24th Outbreak last year. The SPC has issued a RARE DAY 2 HIGH RISK for parts of OK/KS/NE/IA! EVERYONE in this region needs to be taking the necessary precautions/preparations for Tomorrow! Shear profiles are very favorable for significant rotating mesocyclones capable of producing strong/long-lived tornadoes. Below is a hodograph from the NAM model sounding:

Significant veering is shown capable of strongly rotating mesocyclones.

28storms chase team is currently headed out towards the Southern Plains for an active period of Severe Weather! We’ve got a long drive in store with 15+ hours from Mobile to our target area! Current plans are to chase tomorrow and Friday in the Oklahoma/Kansas region (with an initial target near Liberal, Kansas for tomorrow). We’ll be providing live updates from the field and a live stream throughout the days on Thursday and Friday, so be sure to stay tuned to 28storms.com.

The Storm Prediction Center currently has tomorrow’s (Thursday) threat as a Slight Risk across Texas, Western Oklahoma, and Western Kansas. An upper level jet and associated Short Wave Trough is currently nosing into Southern California. Here’s a look at the upper level pattern expected for tomorrow evening. You can clearly see the intense jet streak >120 knots entering the four corners region. This is the precursor for what will be a very active few days across the Southern Plains.

By 00z or 7PM tomorrow the Upper level jet will just be starting to enter the Southern Plains across W Kansas, W Oklahoma, and the TX Panhandle. In combination with a shortwave and mid-level impulse, this will help rapidly deepen an area of surface low pressure on the Lee-Side of the Rocky Mountains. This deepening area of Low Pressure will help to rapidly draw “rich” moisture northward from the Gulf of Mexico. This will also help bring in dewpoints of 60+ F as far north as SW Kansas.

As all of this occurs a dryline will rapidly develop and progress eastward across Western TX, the OK Panhandle, and Western Kansas. This will set the stage for a rapidly destabilizing atmosphere during the afternoon on Thursday. As instability increases and the dryline bulges eastward, thunderstorms will develop during the mid-late afternoon. Many of these storms will have the potential to become severe and potentially supercellular.

With abundant moisture, instability, and lift in place tomorrow, the only other necessary ingredient will be the wind shear. Because the upper/mid-level jet will just be entering the region, the flow at these levels will be weaker. Weaker mid-upper level shear may work to inhibit the development of supercells; however, low-level shear (particularly in the lowest 3 km) will be more than abundant for low-level rotating mesocyclones. The main question is the dominant storm mode: Will it be multicellular of supercellular. Current thinking is that there will be a mix of supercell and multicell structures moving eastward off the dryline. Any supercell that develops will have the potential for tornadoes in the presence of strong low level shear and 0-1km Storm Relative Helicities >150 m2/s2. Any supercellular storms will likely pose an increased risk for tornadoes during the evening hours as low level shear increases further from the strengthening low level jet. Here’s a look at the 850mb chart clearly showing a strong low-level jet at 7PM.

Additionally, more substantial risks of severe weather exist across similar areas (Kansas, Oklahoma, W Texas) on Friday and Saturday! The approaching upper level jet will be clearly established across the Southern Plains during this time frame. Essentially, the only missing ingredient from Thursday’s risk will be in place for Friday and Saturday. Both days pose the potential for a Severe Weather Outbreak! More details will be posted on the blog tomorrow regarding the upcoming threats. Stay tuned to 28storms.com for blog updates and be sure to follow us on Facebook and Twitter. We’ll also be streaming throughout the afternoon and evening tomorrow so be sure to tune in!
-Trey Alvey

The dramatic videos of the tornado near Woodward, Oklahoma, are just a precursor for what is likely to follow over the next 5 days. Today, a Slight Risk of severe storms centered over west Texas has been issued by the Storm Prediction Center. Today’s threat will be marginal, but damaging hail, winds, and a stray tornado cannot be ruled out. Much of the western plains will face a similar threat Wednesday. Tornadoes will certainly be a threat.

The extended range outlook is also highlighting Thursday through Sunday as potential days for severe storms across the central US. Thursday could feature a somewhat significant severe episode. The Storm Prediction Center has already outlined west Texas, Oklahoma, and Kansas under 15% hatched probabilities of severe storms. That is fairly high three days in advance. A dry line will be in play, with plenty of instability and strong shear.

Saturday also has plenty of potential, with the risk area being northern Texas/east Oklahoma/east Kansas/west Missouri/SE Nebraska/S Iowa. As stated before, it is still far too early to get into specifics. Guidance can shift drastically so stay tuned.

Today is generally quiet, but several rounds of severe storms will impact the plains beginning tomorrow.

Monday: Jet dynamics will not support a vigorous surface low. Mid-level ridging over the Rio Grande Valley will promote northwest flow over the central plains. However, modest 500mb positive vorticity advection, slight 250mb divergence via acceleration, and lee-side troughing along the Rockies will promote weak surface cyclogenesis over the Texas panhandle. An associated warm front extending from southern Kansas into central Oklahoma, and a dry line over west Texas will be the convergence boundaries that initiate convection by mid to late afternoon. Large hail will be the primary concern over western Oklahoma and the eastern TX panhandle, where surface-based CAPE values near 2,000 J/KG are being progged by the GFS/NAM. Steep lapse rates will aid in dropping the lifted index between -5 & -7. The highest risk area could easily extend into southcentral/southwest Kansas if moisture return is maximized. Storms motions will be relatively slow and northwest to southeast. The tornado threat is minimal. An isolated tornado or two cannot be ruled out especially if discrete supercells interact with previously generated outflow boundaries.

Tuesday: The weak front will remain nearly stationary across central Oklahoma, extending westward into the Texas panhandle. Convection will likely be limited due to a lack of upper level forcing and sharper temperature and moisture gradients at the surface. However, southeast flow will result in increasing moisture return, moderate instability, and marginal bulk shear values of 30-35 knots. With these ingredients in place, a continued risk of hail and damaging winds associated with isolated thunderstorms will remain over the same general areas threatened Monday.

Beyond this time, forecast uncertainty begins to increase as a result of model disagreement.

Thursday: The severe weather threat could be a bit more significant if guidance remains consistent. A longwave trough entering the western United States by mid-week will set the stage for perhaps a few days of severe storms across the central part of the nation. The first shortwave trough embedded within the longwave will eject out of the Rockies and into the Dakotas. Positive vorticity advection will support the development of a sub-1000mb low over the northern plains. A dry line feature may extend from the Dakotas, southward into western Texas. Along and ahead of the dry line, 50+ dewpoints will extend as far north as South Dakota, which may be high enough to support severe storms given the upslope flow. Mid-level subsidence may inhibit convection most of the afternoon, but supercells should initiate along the line by evening. Supercells are possible from Oklahoma through Nebraska where vertical ascent is strongest due to the close proximity of the best surface troughing and lapse rates. Tornadoes will be more probable as bulk shear values exceeding 40 knots perpendicular to the dry line are likely. A strengthening, south-southwest oriented Low Level Jet of 50 knots due to more robust cyclogenesis will also aid tornadogenesis.

Friday: The Storm Prediction Center has not outlined any areas for severe weather for this period, but only due to uncertainty as to where the first shortwave trough will track. It is too early to pinpoint where the best severe potential will develop, but a slight risk in subsequent outlooks is somewhat likely.

Saturday: It is far too early to determine specifics including exact location and storm mode, but a severe episode appears probable in the central plains. The aforementioned longwave trough will prograde into the central US, with a 250mb jet exceeding 100 knots aloft. A cold front will extend southward into western OKlahoma and Texas. Ahead of the front, the Gulf of Mexico will be open for business with surface dewpoints approaching the mid 60s as far north as northern Missouri and southern Iowa.

If all of this weren’t enough, today’s guidance insists that the pattern will remain active beyond day 7. The longwave trough could remain anchored over the southwest US, hence the formation of a series of storm systems to its east.