Primary Colors

A Facebook discussion got fired up recently about primary colors: which ones are correct?

It’s funny how riled things get on this one. The source of the confusion that I've seen boils down to what kind of primary are we talking about? Additive? Subtractive? How about ‘pshychological’ (artist’s) primaries? Maybe even squeak in the opponent primaries of the LAB color space.

Additive Primaries: Red, Green, Blue
This is what’s happening on the screen of your computer or phone right now as it emits light into your eyes.

Subtractive Primaries: Cyan, Magenta, Yellow
What’s happening on that full color piece of junk mail sitting on your desk as it reflects ambient light at you. Black is usually added in print to compensate for impurities/imperfections in the three primary pigments.

Psychological Primaries: Blue, Red, Yellow
I used to think of this as artist's primaries, but apparently it's also called "psychological". This is a painters approximation of subtractive primaries—artists may start here for color mixing, but the gamut is very limited so other colors have to be added to support it.

Opponent Primaries: Magenta-Green, Yellow-Blue, Luminosity/White-Black.This is a conceptual color space based on theories of how the eye responds to opposing/overlapping colors across the red, green and blue cones. The fact that it separates luminosity from pure color creates some useful image processing techniques in the LAB color space. (L=Luminosity, A=green-magenta opponents, B=blue-yellow opponents)


These primaries aren’t determined by actual physical properties of light, but by the fact that most human eyes are trichromats and have three types of cones with peak sensitivities to red, green and blue light. So our technology and artistry have been geared to interpret and feed us light in those terms. I think it's really, really cool.

Which means, if tetrachromat Zebra Fish decided to get in on the act, they’d probably want _four_ primaries that add ultraviolet to the mix…so they could get the most visual appeal out of their soggy coffee-table books.

Special note—while I think this is extremely cool, it can also be extremely frustrating for color blind individuals who might have lower—or no—sensitivity in some of those cones!

This wikipedia article does an outstanding job detailing some of this: Primary Color

On my way home after photographing monsoon thunderstorms northeast of Flagstaff, I noticed smoke rising over the hills along Townsend-Winona Road. I thought it might be another tree fire, but as I rounded a bend, it turned out to be a terrible house fire. Checking radar, it looks like there were 3 lightning strikes over that location from 2:45-3:00 PM. Several fire trucks were on the scene but the fire was overwhelming and it took quite a while before it seemed to be brought under control. I'm afraid the house may have been completely lost.

A couple of the lightning strikes along Townsend-Winona Rd.



The house fire at Townsend-Winona and Bullion Hill Rd.





Arizona Storm Chase - 9 August 2015

After noting a great supercell near Winslow, I opted to head toward Twin Arrows to see if some developing convection would take off there. It was good for a lot of heavy rain, but hardly any lightning and it didn't manage to organize.


While I was toying with that mess, another storm north of Flagstaff crossed the threshold to the Colorado River Valley, west of Wupatki and went supercellular.


As I pondered my situation and whether I could race to that storm in time before it drifted into the extremely hard to navigate spaces west of Hwy 89, it picked up a tornado warning. So I dropped the slop I was on—to at least give it a try. By the time I had visibility on Hwy 89, it had the merest remnants of an elevated base.


On the chance it might cycle up on some new convection to the south, I took a pretty decent forest service road along the cinder cones north of Sunset Crater. What did pop up didn't develop rotation but still managed to make for some nice storms and lightning.





Arizona Storm Chase - 8 August 2015

More storms showing up with couplets this day, but I didn't manage to intercept them during prime structure. The landscape made up for a lot of those issues. These shots are from Hwy 89 north of Flagstaff along the Mogollon Rim/Colorado River Valley margin.

A scud bomb merging into the updraft between Sunset Crater and Wupatki National Monuments.

More disorganized convection playing with sunbeams north of the San Francisco Peaks.

Benign convection percolating as the atmosphere begins to stabilize.

Sunset Crater is trying to peek between the trees on the right.

Convection has turned to mush almost everywhere, leaving a great sunset aftermath—just northwest of Sunset Crater National Monument, looking toward the San Francisco Peaks.



The Mogollon Rim Convergence Zone worked its magic the past 3 days with southwest flow leading to some especially favorable shear along the Colorado River Valley.

On my way north to meet the best shear parameters—which I thought would be best near Page and the Arizona Strip, I encountered some heavy convection and a nice roll cloud and gust front north of Cameron on Hwy 89.


I figured this one would probably stabilize the air mass pretty solidly, so after following it a bit, getting photos, looking for lightning and doing some roadside nowcasting, I started making my way towards Page. A couple hours later I found myself at The Gap to pick up a replacement 9-volt battery for the lightning trigger. Radar showed a couple strong storms lighting up to my south—where I thought things had already been played. So I raced back south and started catching sight of a very healthy looking anvil peeeking over the plateau to my west. Once I cleared the horizon-blocking hills, I got to meet a beautiful Arizona supercell drifting toward me from the west.

This is the first time I've caught Kelvin-Helmholtz waves along the elevated base of a supercell—and it was an hour from home. This view faces northwest as the cell moves over the edge of the Painted Desert.

Another view as the storm starts to pass to the north

I followed it through Tuba City and further east where it was trying to hand off to a new base before slowly withering.

I've finished evaluating road networks for Arkansas, Louisiana, Mississippi, Alabama, Tennessee, Kentucky, Indiana, Ohio, Michigan, and Wisconsin to wrap up the central US area. I also worked up California and Florida for road options at the tornado hors d'oeuvres they serve up. To help distinguish things better, I added a gray tone to states that haven't been evaluated yet.

US Storm Chase Map - with forested areas

US Chase Map 15 May 2015 - with forest

US Storm Chase Map - without forested areas

US Chase Map 15 May 2015 - without forest

US Storm Chase Map Project

I’ve had a goal of creating a detailed US Chaseability map for a couple years now. I wanted to factor in road grid, tree density and terrain. I’ve made progress on the first two items, and it’s at a point now where it should help inform my chase planning this year. I wanted to share in case anyone else finds it helpful. (For chasers that dwell and chase frequently in the central US, this might be superfluous :) )

My intention for it is to frame what I might expect and be ready for during a chase, or possibly inform my targeting decisions (all other thing being equal).

Please also note that I have not completed road network analysis on Wisconsin, Indiana, Michigan, Ohio, Florida, and Mississippi River Valley (see future plans at bottom of this post).

US Storm Chase Map - with forested areas

US Chase Map 5 May 2015 - with forest

US Storm Chase Map - without forested areas

US Chase Map 5 May 2015 - without forest

I want to make this available as a resource to the storm chasing community. If you are interested in editing or adding content to the layered PSD file, please let me know and I can provide a download link. It is too big—150MB—to provide an ongoing public link (my web host would probably threaten to terminate my account if I did that). If anyone wants to do their own work on it, I’d just ask that any copies or derivatives of this content be re-distributed non-commercially. I can be reached at the email address in the header of this blog.


Road grid quality

  • Green = Typically 1 mile grid with some 2-3 mile gaps
  • Yellow = Typically 2-4 mile network with some 8 mile gaps / 1-2 mile network with discontinuous junctions
  • Orange = Typically 5-10 mile network/uncertain network with gaps up to 16 miles
  • Empty = Questionable or non-existant. Mainly highway chasing.

Tree Density

Contour of areas with highest tree density.

Urban Areas

Highlighted in dark red.


  • This is not intended as a tactical navigation resource. It is meant to provide a strategic overview of chase navigability/storm visibility.
  • Road grid quality does not speak to actual road conditions—mud bogs, sand traps, plowed-over roads, and map mirages.

Map choice

To avoid copyright issues, I took my first dip into working with shapefiles from the US Census Bureau using QGIS on the Mac to convert to DXF and then import into Illustrator. This provided vector data I could use to add county and state boundaries, interstate paths, and urban areas.

I chose a map projection for the data that was compatible with Google Maps mercator projection (EPSG:900913). This aligned with the road network resource I used and the default projection at Data Basin.

Road Network Method

The US Census Bureau provide shapefiles for all roads in the US, but the number of shapefiles is enormous (3200+) and without scripting would be an extremely tedious process. However, reddit user, WestCoastBestCoast94, did go through this process and used the data to generate a high-res PNG image of all roads in the US. I referenced this image to make estimates of road networks and to draw in boundaries. I gave preference to networks with primarily straight roads and perpendicular intersections. There may be decent networks with lots of diagonal roads and angled intersections (I’m looking at you, Texas), but without a more detailed & lengthy examination, I can’t tell which of these are halfway-decent and which are terrible, so I tended to leave them in the lower quality buckets.

I did not have an eternity to do this, so there is going to be some slop in places—taken as a whole, it should provide a reasonable estimate of road network. However, DeLorme, Garmin, Google, Yahoo, Microsoft, whatever map software of your choice, would still need to be the prime resource for current/reasonably-accurate info.

I am not including the actual road-network map in the image above or in the layered PSD file, because I don’t know if ‘WestCoastBestCoast94’ wanted it to be re-distributed in a Creative Commons non-commercial sense. However, you can find his US map and more detailed individual state maps in the directory he created here: It is scaled such that you could paste it into the layered PSD document to compare to contours I’ve drawn.

Tree Density Method

I used the ‘Mask Of Forested Lands Contiguous US’ data from Data Basin to draw contour lines around the areas of highest tree density. There are less dense tree signals that I did not include in the boundaries. I am also not sure how well the data correlates to the real world and whether it includes other annoying, visibility-killing plant life.

Future Plans & Possibilities

  • Road Network: Add contours for California, Wisconsin, Indiana, Michigan, Ohio, Florida and Mississippi River Valley.
  • Evaluate color choices for accessibility and easy evaluation of features (it's probably pretty bad for deuteranopes at this point).
  • Terrain: flat / hilly (maybe 2 or 3 degrees of this?) / rugged / mountainous — with obstructions (rivers/escarpments)
  • River crossings
  • Hostile counties: I’m collecting a list (e.g., Barber Cty, KS)
  • Rest Stop/Boondocking locations

Storm Chase — 19 March 2015

This was a chase-of-opportunity with my kids while visiting family in western Oklahoma. Before heading out, I brewed up my traditional personal estimate for success for the day:

  • Thunderstorms 75%
  • Transient Structure 50%
  • Supercell 15%
  • Rotating Wall/Funnel 5%
  • Tornado 1%

I got a late start getting out of the fog and drizzle of Elk City and got to my target in Vernon by 20Z — about an hour later than I wanted to. It was nice to see clearing and bubbling cumulus to the south. After fueling up and messing around with the latest data for too long, we headed further south into the clear and near the junction of Hwy 183 and 277 by 21Z. There were two areas of initiation at this point: some early development to my northwest north of Seymour, and a more mature cell near Archer City. The Archer City tower looked great, but I opted for the Seymour target since it didn’t involve playing catch-up, and being closer to the triple point, I thought it might have a better fetch of backed surface winds. The problem with this is that the western target was also further north and so was first to greet the cold front. It also got to choke on stable inflow from the Archer City storm. (click images for larger versions)

My daughter checking out the Archer City tower — 2110Z

Until it got wiped out though, it was a nice early-season chase. After grabbing a few shots of that tower to the east, we drove back north to watch the inbound Seymour storms. At an overlook east of Lake Kemp I met Marcus Diaz, Jason Boggs, Bobby Hines, Mark Eslick, and Tyler Hudson. We shared the views for a while as the convection gained strength and developed some structure. As the forward flank gust front finally started spitting rain on us, we hopped in our cars and headed our separate ways. Road options were pretty scarce, and we had to get a ways south of the storm before getting back east on Hwy 277 to get ahead of it.

Some structure on the developing cell near Lake Kemp — 2150Z

Marcus Diaz, Mark Eslick, Tyler Hudson and Jason Boggs check out radar and the storm base east of Lake Kemp — 2151Z

Encroaching outflow — 2204Z

A north option on SR 25 put us in a spot to look into a beautifully sculpted vault with a lengthy arcus/inflow tail spanning the sky and racing into the storm base. As the forward flank started gusting toward us, we cruised back south to get out of the way.

Storm base and pump jack from SR 25 — 2242Z

Terraced vault with arcus/inflow tail racing westward from SR 25 — 2247Z

Arcus and shelf gusting southward along SR 25 — 2247Z

Heading south, I wondered why truck traffic was backed up. Turns out a chaser had a yellow vehicle parked partway into the southbound lane and placing his body even further into the lane. So the trucks were waiting their turn to safely pull into the opposing lane to get around him as he waved people around. There were plenty of great pull-offs on this road—I used a couple of them. And the grass shoulder was huge and in good shape too, so there was no reason for treating the shoulder and pull out areas like hot lava. It was really really frustrating and embarrassing. I needed to get ahead of the gust front and didn’t have time stop and attempt a chaser-101 session, or get a good read of the decals on the vehicle.

Chaser obstruction — 2249Z

The storm was pretty strung out at this point but still dishing out some interesting sights. We got further east to Holliday and noticed a bell shaped lowering. It appeared to be a new updraft trying to forming well to the east of the base I had been watching, and it had what appeared to be a bit of RFD curling in and lowering a wall cloud/RFD shelf around itself before gusting out and merging with the forward flank.

Transient updraft/lowering seen west of Holliday — 2305Z

After that, we bailed out on the storm and headed south for some views of the other storm as it approached Bowie. We got a look at the back of the storm and its upswept flanking line before calling that one off too in some beautiful country.

Backside view of the other storm approaching Bowie — 2349Z

I’ve been watching the GFS signals for this Thursday (19 March 2015) flicker on & off for the past week. It’s nice to see a thin glimmer of hope for tomorrow. Moisture is forecast to move up to the Red River with dew points around 60 degrees. Lapse rates aren’t so great, and NAM and GFS vary on the degree of instability from 250-500 j/kg for GFS and up to 1000 j/kg from NAM. A cold front will sag southward and into this area of instability with storms firing as it forces its way into the warm sector. A shortwave trough over the southwest will feed 40-50 knot H5 winds over the area. So this leads to the possibility for some severe storms with a lot of caveats—especially marginal instability and an undercutting cold front.

18Z NAM shows 0-3 km Helicity maximized up to 250-350 m2/s2 narrowly along the cold front near the triple point at 00Z in the vicinity of Childress. 0-1km SRH is localized and probably barely worth noting near the triple point in the 50-100 m2/s2 range. 18Z GFS is much more conservative and also points further east—south of Wichita Falls. Obviously wouldn’t mind NAM’s optimism working out moreso than GFS at this point and I’m planning to give it a shot just in case. I’m planning to head out of Elk City with an initial target of Vernon, TX by early afternoon.

19 May 2013 Oxford Supercell Diagram

In my previous post, I diagrammed the Oxford, Kansas supercell from 19 May 2013. About 90 seconds after that shot was taken, a new area of low level rotation developed just ahead of the occlusion. This is a diagram of that moment as the inflow was forced into the updraft at that point and rapidly exposing circulation at the cloud base.

Oxford, Kansas Supercell Part 2 - 19 May 2013
Oxford, Kansas Supercell Part 2 - 19 May 2013 - Diagrammed

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