Saturday, April 28, 2018

Multi-Day Severe Weather Event Possible Next Week (Plus Chase Gear & Online Data Sources)

  After chasing the first four outbreaks this year in the jungles East of the Mississippi the Plains are heating up! A multi-day severe weather event seems to be coming together for next week (Sunday 29 April, Monday 30 April,Tuesday 1 May, Wednesday 2 May) and it's obviously garnering quite a bit of attention. This attention is exacerbated by the fact that there have been a whopping 0 tornadoes in Oklahoma and Kansas so far but this isn't all hype; significant, dangerous storms capable of all hazards are possible, especially on Wednesday.

   I'll be heading West Monday to spend the next few days chasing storms so I'll post another, more detailed blog update then with a full chase forecast this weekend when we've had more time to see exactly how things evolve to set the stage but we'll still take a brief look tonight at how I see the general synoptic-scale features coming together.

  Since this is the first big, multi-day, central plains chase setup this season I thought it would also be cool to break down some of the gear I use when I'm chasing. I've had several people ask me about this so this seems like a perfect time to do so. I'm also going to post links to some of my preferred online sources for analysis data that I often use when I'm out. I typically use a suite of operational or "professional" software programs designed specifically for the most detailed forecasting and analysis work when I'm at home or in the office but obviously I don't have quite the same computing power when out on the road so I have several resources I use regularly for various things.

My Chase Gear
  Believe it or not, despite the "flashy" stuff I use for weather forecasting when I'm not out chasing, I'm not a particularly high-tech storm chaser. I'm not a Luddite or anything, I just prefer a good balance between having access to the amount of data I like and being able to focus on what's actually going on around me as well.

Cameras: 
- Sony FDRAX53 4K Ultra-HD Video Camera W/26.8mm Zeiss Vario Sonnar Zoom Lens, 40x Image Zoom, Optical "SteadyShot" Technology, 120fps Recording, 3" LCD, and a High-Sensitivity Image Sensor, Video/Still Photos/Time Lapses
This is my "go-to" camera for all the higher quality video I shoot and it's the one that captures most of what ends up in my YouTube videos. For one thing, it just captures unbelievably crisp video and *gasp* that's the main thing I look for in a video camera. I switch up how I utilize it based on what I'm chasing and how I'm chasing it. Sometimes I'll mount it and use it as my dash cam because it absolutely will not give you any "jello" unless you're driving Dukes of Hazard style, and even then I think it will hold a steady shot. There are several times, if I'm feeling froggy, that I'll switch out the dash cam pre-chase, and keep this one next to me for throwing on a tripod and letting it catch whatever is going on in front of us. It's also amazing for time lapses. One of the best things about this camera and one of the reasons I ALWAYS have it by my side is its ability to film at night. No need for that goofy green nightvision with this thing because it can see better than a cat at night, I swear it. There have been at least a half-dozen tornadoes I've been able to confirm (and scud I was able to confirm wasn't a tornado) that were invisible to the naked eye but a peek on the LCD screen showed exactly what was there. 
Honestly, you can get the job done just fine without spending $1,000 on a video camera but if you were trying to spend that much this is the camera I'd recommend because I've gotten my money's worth for sure.

- Canon SX120IS 
This is not the fanciest camera you'll ever see but this 9 year old Canon is still always in the bag. First of all, shooting photos in/near tornadoes, supercell thunderstorms, hurricanes, and any other severe weather you can think of isn't necessarily the same "user friendly" environment you might find if you're say, photographing a sunset or a wedding. This camera has always held up perfectly when photographing in dangerous, difficult conditions with rain, hail, tornadoes, and most recently milk crates and housing insulation blowing at me. I'm not sure how much it costs these days but 9 years ago it was like $90 so I'm way more comfortable having this in the field. It's still a good camera too though. A little knowledge and practice with tweaking your exposure/aperture settings/angles/etc and you can take great photos that won't look like they came from an old PowerShot camera. 

- Samsung Galaxy 3 
Yes, that is my phone. Yes, I still use a Galaxy 3. Listen, I've had this phone forever and it does every single thing I need it to. Plus I can export all of my apps and such to external storage which basically means my stack of Micro SD cards at home equates to unlimited storage because some new model phones scratched the ability to export apps to external storage in exchange for larger internal memory (but not unlimited internal memory). I really do consider this as another camera however. Most of the time I'll have other cameras set up with one set up on a wide-angle shot, one set up on a tight shot, and I can use my phone for miscellaneous other shots. Specs aren't too much to talk about, it takes HD photos up to 1920x1080 resolution and has the ability to manually set exposure etc so you can outdo many cheap cameras on the market these days.

Data Acquisition:
-Custom HP ProBook 450G3 Notebook
It's probably self-explanatory what I use this for and the links to sites I visit most often will be most helpful so I'll just list a few specs. (Surprisingly, I don't often have this with me because I use RadarScope and a few apps on my phone while I'm chasing solo as opposed to this. Honestly, RadarScope completely changed my life because now I can just jump in the car and go instead of hooking my laptop up)
  • Intel Core i5 Processors
  • Discrete Radeon Graphics
  • 500GB (8GB Internal)

Miscellaneous:

There's no reason to go through every single thing I pack but I do have a few things I like to make sure I have in my bags. I vary what I take depending on whether I'm hunting for supercell tornadoes or riding out a hurricane somewhere along the coast. 



  • This might not seem like I should mention it but it's my blog so I am. I always pack 3 extra outfits (plus the expected number of outfits for the planned duration of the trip). I'll pack one warm-weather outfit, one cool-weather outfit (sounds crazy chasing storms when it's 80 degrees but you'd be surprised just how cold post-frontal air masses can be, and can't forget cold RFD etc). The third outfit is packed for the unfortunate scenario of a damaging storm impacting people. When storms damage/destroy people's property they can easily end up dirty and wet and having seen this happen more times than I'd like to I like to have a warm, dry set of clothes to offer them. 
  • Obviously the camera accessories are always in my bags.
  • Extra chargers. I have learned that you can't have too many chargers for phones and whatnot but you can certainly have too few.
  • Card Reader. I bought a cheap card reader that reads SD/Micro SD cards, larger memory cards from a laptop, as well as direct file transfer via USB. This comes in handy when you have mutiple devices for capturing footage because you can just take a card out, pop it in the reader, and upload that precious lightning shot to social media meaning you can start getting those "Likes" that so many need to survive a little bit quicker.
  • Backup MiFi hotspots. I pack two mobile WiFi devices. One AT&T, and one Verizon. Different providers work better in different areas so I like to cover my bases.
  • PAPER MAPS! These are NOT obsolete. I've found that an updated trucker's atlas will work wonders when you drop to 1 bar of 3G and you can't get Google Maps Offline to work or that GPS that loves to give orders and doesn't care how much we cuss it says State Road 37 is supposed to cross the interstate but it's actually just some guy named Atticus' driveway.
  • Colored Pencils. Makes sense right? Storm chasing often consists of hours of sitting roadside waiting for the cap to break so you've got to have something to do right. I actually make sure I have these because I print off surface obs charts every chance I get and it's frustrating to not have my pencils when I want them.
  • Reference Books. Oddly enough I take lots of notes when I'm chasing (things to remember for case studies, observations, etc) and I like to have paper and reference books to use.
  • I always have safety/search and rescue gear like flashlights and first aid kits. I'm not going to list everything but the most useful things I've had with me are flashlights and chainsaws.
  • Lastly, various random things I decide to throw in my bags for no real rhyme or reason.
29 April-3 May Severe Weather Setup

  As I said earlier, I'm going to be posting a detailed chase forecast later so we're just going to look at some current observations and how they should evolve to assemble the general background environment for our multi-day severe weather outbreak this coming week.

Looking at the 250mb level to assess the jet stream winds we can see a split-flow regime in place with a longwave trough over the East CONUS and a ridge over the West. A strong upper-low is entering the PacNW and this is actually energy that will be associated with our storms. The polar-front jet is evident diving in from central Canada around the Great Lakes and rounding through the trough before phasing with energy from the subtropical jet over New England. This pattern has been pretty stagnant for awhile now and that's resulted in quiet weather over the Plains as it has inhibited meaningful moisture/theta-e return flow. The pattern has become more progressive now however, and as the PacNW upper-low digs into the Rockies, associated cyclogenesis will promote a strong increase of sustained theta-e return and this will fuel an extended severe weather episode. The subtropical jet is evident entering West Mexico before travelling through extreme southern Texas and rounding the base of the eastern trough over Florida. That feature resulted in a few severe storms, including a couple tornado warnings in Florida today. 

500mb 0z obs show similar features as the 250mb chart but the location and amplitude of shortwaves embedded within split flow is noticeable at this level. A 50kt speed max is visible over the Iowa region and it's associated with a surface baroclinic zone that is resulting in some weak convection in the East but we're focusing on the upcoming chase. In my everyday forecasts I've assessed this feature much more but for our purpose we are more concerned with the high-pressure in the wake of this trough as it is suppressing moisture return now but by Sunday-Monday it will be positioned near the Gulf Coast and will be promoting strong moisture surges northward.



The main thing I want to point out here is the beginning indications of our elevated mixed layer over the SW CONUS. 700mb is a good proxy for the location of the EML and you can see strong heating over the SW already with temps approaching 10C. As southwesterly flow becomes more prevalent in response to the digging trough early next week we should see this EML advect relatively easily over the Central Plains forming a strong cap but with very steep lapse rates atop the inversion above the moist sector (perhaps 9C/km).

Tonight's surface analysis doesn't look particularly impressive but the beginning of our setup is hiding in there. A frontal system associated with the speed max we identified aloft is located near the Great Lakes with a "dry front" passing through the Ohio Valley. A cold front is crossing Florida as well and this is keeping moisture confined to the South for now but a surface-high is noted over the southern plains. Once this high slides eastward in the next 24-36 hours we will see moisture return through the central plains. Also note the frontal system in the PacNW, this is the surface reflection of our initial energy that will dig in and should help assemble our storm environment early/mid-week.

I just wanted to share this to demonstrate the deep, rich moisture that isn't necessarily evident on CONUS soundings yet but is primed just upstream in Mexico to surge northward. This shows rich moisture extending up through the 850mb layer. Once the aforementioned high moves eastward and our surface-low develops over the Kansas area the southerly flow will advect this moisture well through the central CONUS resulting in a very moist warm sector ahead of our dryline.

So now we have a solid conceptual model of how things should come together, at least in a general sense as smaller-scale details will become evident in the coming days. We can infer that the eastern trough will progress eastward as ridging aloft builds in its place and a Pacific trough will build in the West. As a shortwave pivots around the base of the western trough and digs into the central plains by Sunday-Monday we should see cyclogenesis occur with a surface-low developing somewhere in the KS/OK vicinity. This will result in strong moisture advection northward along the front range region of the Rockies. Based on upstream observations in Mexico and the Gulf we should be able to generate 60F dew points into OK by Monday. This deep moisture will continue to spread northward through Tues-Wed as a warm front moves all the way into the Great Lakes area. Steep mid-level lapse rates already becoming evident over the SW will advect over the central plains within southwesterly flow and will overlap a sufficiently deep moist sector ahead of our dryline and cold front. Surface heating beneath a strong cap will aid destabilization each day and moderate to strong instability should develop with classic "loaded gun" soundings the anticipated thermodynamic profiles. Although forcing for ascent will be weaker on Monday and Tuesday compared to Wednesday, convergence along the dryline should be enough to eventually break the cap and initiate scattered storms. (I will admit that I've already looked at forecast model cross-sections to assess the depth of mixing behind the dryline relative to the depth of moisture ahead of it and I think it's sufficient to get parcels to their LFC) We can narrow down the burst point and dryline/frontal position as we get closer to "go time". Wednesday looks like the most significant day as confidence in convective initiation is a little higher since upper-air support is more favorable as our upper-level energy arrives providing stronger forcing for ascent. Given boundary-relative flow I think storms should have a favorable "parcel residence time" to maintain intensity but also have storm motions to help maintain discrete structures. This coupled with elongated, looping hodographs suggests that supercells capable of large hail and tornadoes will be possible each day with the threat increasing daily. 
  The main concerns will be the strength of the cap and the effect of previous day/morning convection on destabilization and boundary positions. I don't think the early convection will inhibit this threat entirely but it could certainly affect the areal extent of the threat. The cap of course is, well, it's the cap so there's always the chance that it does what caps do.

Now that we've made a basic forecast we'll look at one or two model products to see how the models compare to our forecast. (Note: I am only posting a few graphics that blend well with the model consensus. These are not all the models I analyze while forecasting and the graphics posted do not constitute the exact forecast as, like I said, the specifics will work out in the coming days and will be covered in the chase forecast post this weekend. These are only to show a general, large-scale synoptic setup and demonstrate the relationships between various features and how we predicted them in our observation analysis)

Multi-Model "Spaghetti Plot" Showing Simulation of 500mb Heights. There is clearly still some divergence between models regarding small-scale details. This is a typical degree of divergence with some struggling with an embedded shortwave across the SE CONUS and differences regarding the precise amplitude of the western trough but the general idea is consistent with this run of these models. (Model Valid 12z Monday 30 April 2018) 

Same multi-model comparison, this time with MSLP. Quite a bit of model disagreement as expected regarding exact timing of cyclogenesis and placement of surface boundaries. 










The above graphics show GFS modeled surface dew points for Monday, Tuesday, and Wednesday (Top to Bottom) along with mid-level lapse rates for Sunday. Notice a plume of very unstable lapse rates over the SW CONUS. You can see the general organization of our moist sector and when southwesterly flow arrives, this plume of steep lapse rates will advect over the top of the warm sector, likely resulting in strong, capped instability. This should limit cells from initiating everywhere and allow the updrafts that do break the cap to be relatively explosive.

Monday 30 April 2018



GFS and ECMWF comparison of CAPE for Monday. A corridor of moderate to strong instability should exist across the central plains, although the GFS is more aggressive. Even though dynamics and upper-air support is weaker on Monday, this would certainly support severe storms and the shear profiles would support supercellular storms, although boundary-relative winds may force updrafts to shoot off the boundary fairly quickly resulting in loss of ascent. Storm-relative mid-level flow is a bit weaker too so there may be some negative interference between close-proximity cells.

Tuesday 1 May 2018




As the northern surface-low moves eastward toward the Great Lakes the severe threta shifts slightly eastward for Tuesday. Again, a corridor of moderate instability is suggested to develop ahead of a KS/OK/TX dryline. 0-6km shear overlapping the moist sector is a little on the weak side, on the order of 30kts initially. This will strengthen throughout the day so the timing of initiation could be important as it relates to the evolution of convective mode. Regardless, severe storms capable of all hazards are possible.


Wednesday 2 May 2018





Current thinking is that Wednesday could be the most significant day of this event, although anyone in the threat area may be impacted any of the days. Once again, a corridor of moderate instability is progged across the central plains. The big difference this day should be the arrival of a substantial shortwave. This shortwave will increase both deep-layer shear and forcing for ascent. The low-level cyclogenetic response will lead to the development of a dryline triple point somewhere in the Kansas vicinity. This will act to increase storm-scale ascent due to convergence and increasing baroclinicity and the potential for streamwise vorticity, which is a factor in tornadogenesis as hodographs become enhanced with a marked increase in curvature. Storm-relative winds throughout the mid-level should promote sufficient updraft/downdraft separation and parcel residence time should be favorable for storms to maintain. These factors are some of the reasons why I believe the most likely convective mode will be supercells on Wednesday with the potential for a few tornadoes, particularly in the KS/OK area. Tornado potential may increase through the evening as well coincident with the arrival of a 40-50kt low-level jet.


 I'll post regular updates over the next week as I will be out each day chasing storms across the plains, starting with the initial chase target forecast this weekend.

Weather Analysis Resources
Now that we have a broad idea of what the next several days may look like regarding the potential for a widespread severe weather event, and we took a look at some of the gear I take with me to chase these storms, lets look at where in the world you can track this event as it plays out. These are just a few of the websites I've used from time to time while chasing severe storms, in no particular order. (Note: I did not create any of these sites)

Friday, April 13, 2018

Chase Forecast for Friday 13 April 2018

  Hey hey folks! We're hitting the road super early in the morning for a few days of chasing tornadoes so let's get right into it. Things are actually coming together, and have been for several days if you've been following along, for a pretty widespread severe event over the next three days (Friday, Saturday, Sunday). The greatest tornado potential appears to be tomorrow but Saturday and Sunday aren't sleepers either. We'll cover tomorrow's setup and chase plan in this post and once I get in somewhere to rest tomorrow night we'll break down Saturday's setup and so on.

So what are we looking at? Well in short a pretty widespread area from East Texas northward through Iowa is at risk for potentially significant storms. The SPC issued an "enhanced" risk (3/5) for severe weather 3 days out, which is notable alone, and it seems likely that tornado and severe thunderstorm watches will occupy many-a-mile tomorrow. You obviously can't just target East Texas to Iowa though so let's narrow it down a bit.

There are actually a few different options that a chaser could consider and they're all relatively reasonable for tornado potential. That's part of what makes this a little more complex, and in my opinion a little more interesting and fun. We'll dive into how things have evolved up to this point and I'll share my thoughts on how I think things may play out and how I'm going to chase this event as well as a couple other areas I think you could target.


Current Analysis and Forecast
All in all we've got an impressive system that has come together across the central US and this is putting a classic Plains setup on the table. A relatively high amplitude, though neutral-tilt, shortwave trough embedded within the Polar Jet has been swinging around the Rockies for the past 24-36hrs now and it has a powerful speed max associated with it. Winds aloft around 30,000ft are over 100kts and this cross-range flow has aided in deep lee-side cyclogenesis in the Colorado region. A strong surface-low (sub-990mb) spun up today and a significant organizing mid-latitude cyclone is evident. My morning observation chart analysis showed the effects of this low already ongoing and essentially giving us a head start on priming the environment for tomorrow. For one thing, a previous low-pressure system passed toward the Great Lakes earlier in the week and this helped reconnect us to rich Gulf moisture following a preceding cold front. The development of this more significant low has picked up right where we wanted it to and started pulling the approaching front back North as a warm front. At 14z this morning there were already mid-60's dew points in East Texas and a deep moisture axis extended well up to 850mb. A nocturnal low-level jet and further deepening of the surface cyclone will be key in establishing our pre-frontal moist sector and ramp up this moisture return even more so I fully expect to see mid-60's dew points all the way into Iowa. I always like to see the moist sector get established well before initiation is expected because it allows the moisture to build throughout the boundary-layer and help limit the chances of a shallow moist layer.


A dryline was analyzed on morning obs and has been drifting ENE throughout the day and this feature will be a key factor tomorrow. Observed soundings also show very very steep lapse rates over the SW US, approaching dry-adiabatic.

Just these observations allow us to piece together the bigger picture. So as the lead shortwave ejects into the central US the surface low will slide ENE into KS/NE by noon. A triple point will come into place in eastern KS/NE with the dryline extending southward through the OKC area into Texas, a trailing cold front, and a warm front extending eastward through Iowa. We've already discussed some of the characteristics of the moist sector ahead of these features and strong theta-e advection coupled with strong diurnal heating will result in at least moderate instability developing. Southwesterly flow aloft associated with the mid-level speed max will advect the steep lapse rates observed on tonight's 00z soundings in the SW US northeastward and just like that you've assembled a severe storm environment. Steep lapse rates/buoyancy atop a deep moist layer with multiple triggers for ascent, that's what we have.


But that's just the large scale setup, to narrow down our possible chase areas we need to assess probable storm evolution/storm mode and mesoscale features. The axis of the upper-jet streak looks timed out to dive into the KS area by mid-afternoon so it appears that the stronger deep-layer shear will exist from eastern KS into MO and IA, something on the order of 50kts. Of great interest in severe storm forecasting is the orientation of shear vectors to the initiating boundary. In this case shear vectors should cross the dryline at about 45degrees and this is pretty good for the development of severe storms. This allows storms to roam relatively freely while still maintaining a sufficient "parcel residence time" along the region of ascent to sustain. Further South shear profiles will still support severe storms but with mid-level shear somewhat weaker and more parallel to the boundary I think it is very possible that storms will both ride the boundary and run into each other, both of which lead me to anticipate a more linear structure, somewhat less favorable for supercell tornadoes, although there is a realistic chance that pre-frontal storms develop and these would certainly pose a supercell threat. Forecast data shows long, looping hodos as well, particularly in the vicinity of the triple point where low-level winds will be a little more backed and the likelihood of mesocyclone/low-level rotation appears fairly high in this area. A strengthening of the low-level jet by late afternoon/early evening will only serve to enlarge hodographs even more and this would further increase the tornado threat.
HRRR Forecast Sounding (Via SHARPpy Software) for Kansas City, MO (Blue-ish Traces) and Longview, TX at 19z Friday 13 April 2018. You can compare the pre-storm environments in these two locations with this tool. Notice, in both locations the moisture extends well throughout the BL and both also show suffcient buoyancy. The TX profile however is already saturated woth strong vertical velocities suggesting ongoing convection and cloud cover. A veer-back-veer profile is evident in TX too and weaker mid-level winds could result in storm mergers early, inhibiting greater supercell potential, but the hodograph still suggests some tornado potential. I've overlayed the dryline motion across KS/MO on the hodograph to show boundary-relative winds in that region.  

How does this play out then? As mentioned, a sfc-low will be positioned in central KS. A strong cap will be in place and this could delay initiation but will also help maintain discrete cells if we get storms. Elevated convection will likely be ongoing through the morning but this will be North of the warm front and will lift out of the region early. Skies should be mostly clear as a clear slot works into the region and the depth of dryline mixing relative to the depth of the moist layer is more than sufficient to get parcels to their LFC (Level of Free Convection). Because of these factors I think it's reasonable to infer that CI (convective initiation) will occur in eastern KS/OK along the dryline by mid-afternoon and rapidly track northeastward. Storms will also fire to the South in East Texas around this same time but I suspect there will be issues with preferred storm mode. This is not to say that the risk is lower here but simply that it is a less favorable chase setup. All hazards are on the table across the entire risk area. Due to the factors we looked at I believe that storms in East KS/OK will become supercellular fairly quickly as they track into MO/IA. This is where I think the greatest threat for supercell tornadoes exists, including the possibility for a few strong tornadoes.

How Should I Chase This Setup?
Personally, I am going to target the triple point action. This seems like the most likely location to get supercell tornadoes given such a favorable temporal/spatial overlap of ingredients. There are some uncertainties regarding the exact location of initiation but I'm going to set up just northeast of where I think CI will occur and simply ride the gradients, picking off the cells as they move northeast. I think it's a good bet to give yourself a little room to play with since storm motion will be fast due to the strong wind fields and that's what I'm doing. 

The southern play in East Texas is another viable option as well. As I said, the only real limiting issues I see down here are possible messy storm evolution and a water-loaded profile that may result in HP cells. Regardless, embedded supercells will still be possible through the evening here and it's a solid target.

Lastly, I also think there's an outside play farther East along the warm front. While storms continue to merge to the South you could find yourself in a good spot if you caught an already organized supercell as it started to ride the WF. Once storms cross the WF, tornado potential will eventually wane but if you're looking for the outside chance or you live in the northern Ohio Valley and can't make the drive West then this is a play worth considering.

It's late and I have to get a little rest while I can, the next 2-3 days will be busy. Just remember, this post focused primarily on chasing tornado potential but anyone in the severe threat tomorrow should stay alert because dangerous severe storms are very possible. I'll update again tomorrow with a recap from the road of how the chase goes and we'll look at Saturday's setup. Make sure to follow my other online profiles (links to the right) to get real-time updates from the storms. Also follow my Twitch channel or my chase partner's Twitch channel for live video of our chase adventures. Stay cool, see ya soon.
DKK
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