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.

Details

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.

Caveats

  • 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: http://foid.me/roads/. 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

On the Continuum of Walls and Shelves

In 2010 after my first Great Plains chase, I spent a lot of time going through my photos and working to improve my understanding of storm structure. For one of those exercises, I diagrammed the Bowdle supercell. There was a lot of excellent feedback and discussion on all the structure in that beautiful, terrible, amazing storm.

Each new supercell I chase broadens my appreciation for all the ingredients and dynamics that make each one unique and awesome. I enjoy recapping each one and visualizing what was happening, so I've been keen to diagram some more recent storms.

What I especially wanted to work on were transition points in space or time where a shelf cloud is merging or morphing into a wall cloud/tail cloud and vice-versa. A lot of times it's pretty clear what's what. But because the storm and its environment don't care about taxonomy, there are plenty of cases where things ride along a diffuse spectrum. To me, it's educational to watch these things unfold and look for transitions where one thing becomes another, and what that means for the fluid movement and interaction of near-storm air masses.

So, here is a batch of a few more.

Denver Supercell - May 21, 2014

While this storm was still strengthening over Denver Metro and headed toward the airport, it had a very compact RFD shelf that I wanted to call a wall cloud at first glance. But the RFD appears to be responsible for lifting this prominent feature out ahead of the base while the true wall clouds spins away behind. Mike Olbinski's time lapse nicely demonstrates the dynamics (See the 6:24 segment of the video).

Denver Supercell - May 21, 2014
Denver Supercell - May 21, 2014 - Diagrammed

Goshen County Supercell - May 20, 2014

This was a view that to me, beautifully demonstrates the source of a weak wall cloud’s formation as the forward flank's rain foot intrudes into the updraft, drastically lowering the condensation level in that area. How much of the foreground lowering would technically be considered a wall cloud vs. RFD shelf was questionable to me.

Goshen County Supercell - May 20, 2014
Goshen County Supercell - May 20, 2014 - Diagrammed

Newkirk, Oklahoma Supercell - May 19, 2013

This is an example of a transition point where the RFD is smearing a weak wall cloud into a shelf cloud. At least that's how it seems to me. You can see that the foreground lowering is "pointing" toward the forward flank, and benefiting from lowered condensation as it rises into the base. But now it's being hurried and lifted on its way by the RFD gust front (which it "points" away from). It seems to be in a place between both 'definitions' and both dynamic conditions.

Newkirk, Oklahoma Supercell - May 19, 2013
Newkirk, Oklahoma Supercell - May 19, 2013 - Diagrammed

Oxford, Kansas Supercell - May 19, 2013

This storm had a shelf feature on the forward flank leading straight into the the RFD core that made me think of video of the Long Point, Illinois storm on November 17, 2013. Skip Talbot had commented that the forward flank shelf on that storm seemed to behave like a hybrid shelf cloud and inflow band.

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

I just finished editing and uploading video to the September 27, 2014 chase report.

Arizona Storm Chase and Supercells - September 27, 2014 from Jeremy Perez on Vimeo.

Video account and time lapse sequences from the chase.

It's been three years since I've had a really good storm chase in Arizona. This past Saturday, I had a chance to make up for the last couple of missed years. I wound up tracking three supercells along Highway 93 between I-40 and Wickenburg. The last of those three was difficult to observe due to bad positioning, surrounding convection, and unexpected freight trains, but the first two were spectacular amid some stunning Arizona landscapes.

The day before, I had set an initial target of Kingman, Arizona by sunrise, based on NAM and GFS placement of a closed low over Nevada. This was forecast to wrap up 30-50 kts of deep layer shear on top of a cold front over the Colorado river while rich moisture surged northward bringing mid 60 degree dew points. As is usually the case, targeting was based on a compromise between better instability further south vs. better dynamics further north. Instability and backed surface winds appeared to be maximized around daybreak and weakening by midday (1000-1500 j/kg with 100-150 m2/s2 SRH). By the night before, all models were trending downward on lapse rates, so forecast instability was dwindling. However, there was still enough to work with, and hodographs were very tantalizing by Arizona standards. This did adjust my perspective on positioning and timing. So I was able to get a bit more sleep and head out of Flagstaff a little later than planned (5AM instead of 3AM).

I stopped at Seligman about 6:00 AM. As I looked west, I was treated to a line of storms flickering with constant lightning as they trained along the cold front near Kingman. HRRR was forecasting the convection to quickly fill in eastward, along sheared out bands with some stronger embedded storms. HRRR's version of SRH, bulk shear and CAPE still looked promising and was trending toward batches of storm helicity tracks over western Yavapai county by mid to late morning.

Anticrepuscular rays lead into a line of storms as seen looking west from Seligman, AZ. 6:05 AM / 1305Z

Anticrepuscular rays lead into a line of storms as seen looking west from Seligman, AZ. 6:05 AM / 1305Z

Once I reached Highway 93 a little before 8AM, a weak line of storms was passing overhead while a stronger line was approaching from the west. That stronger line featured a healthy cell just to my southwest with a persistent velocity couplet. It looked like it would cross Hwy 93 a couple miles south of I-40 and I had some difficulty deciding on which highway to intercept it (no decent side-road options in this area, just the two main perpendicular highways). I would have preferred the east-west option of I-40 for more fine-tuned positioning and safety margin on storms that are moving mainly northward. But I finally decided on my north-south Hwy 93 option since it would give more opportunities to pull off, start and stop instead of being trapped on the interstate with fewer offramps. As the updraft for the embedded cell moved by my position, it wasn't much to look at, and just seemed to be putting a bit of a kink in the line.

Updraft base in a line of convection as seen looking west from Highway 93 about six miles south of I-40. 8:10 AM / 1510Z

Updraft base in a line of convection as seen looking west from Highway 93 about six miles south of I-40. 8:10 AM / 1510Z

A line of convection as seen looking west from Highway 93 about six miles south of I-40. 8:30 AM / 1530Z

A line of convection as seen looking west from Highway 93 about six miles south of I-40. 8:30 AM / 1530Z

A supercell sports a lowering where the highway disappears into the hills. Meanwhile, trailing convection begins to merge into a bowing segment. View is to the northwest from Highway 93 a few miles south of I-40. 8:35 AM / 1535Z

A supercell sports a lowering where the highway disappears into the hills. Meanwhile, trailing convection begins to merge into a bowing segment. View is to the northwest from Highway 93 a few miles south of I-40. 8:35 AM / 1535Z

Reflectivity and velocity radar of the embedded mesocyclone. 7:54 AM / 1454Z

Reflectivity and velocity radar of the embedded mesocyclone. 7:54 AM / 1454Z

Because of the added safety cautions being on the north-south road, and new convection fluctuating to the south of my target cell, I decided to stay a lot further south of it than I wanted. About the time it neared the I-40/Hwy 89 junction, it didn't look as strong on radar, but the trailing gust front finally pushed hard and it expanded outward in spectacular fashion. As a kink in the shelf took shape, a rugged, conical lowering materialized behind the surging gust front before getting smeared out.

The gust front south of a supercell pushes out over Highway 93 a few miles south of I-40. View is to the north. 8:40 AM / 1540Z

The gust front south of a supercell pushes out over Highway 93 a few miles south of I-40. View is to the north. 8:40 AM / 1540Z

A kink in the gust front develops, leading to a conical lowering. View is to the north from Highway 93. 8:40 AM / 1540Z
A kink in the gust front develops, leading to a conical lowering. View is to the north from Highway 93. 8:40 AM / 1540Z

A kink in the gust front develops, leading to a conical lowering. View is to the north from Highway 93. 8:40 AM / 1540Z

A shelf cloud lines up along Highway 93. View is to the north. 8:45 AM / 1545Z

A shelf cloud lines up along Highway 93. View is to the north. 8:45 AM / 1545Z

After that amazing encounter, I headed further south to get in front of some more developing convection. Along the way, I caught brief views of stronger updraft bases between precipitation cores, and irresistible stormy views in the desert terrain.

A dark rain free base peeks out from between two rain cores as seen from Highway 93 looking southwest. 9:50 AM / 1650Z

A dark rain free base peeks out from between two rain cores as seen from Highway 93 looking southwest. 9:50 AM / 1650Z

Disorganized convection paints the sky above a soaked desert landscape. As seen from Highway 93 looking southeast. 10:20 AM / 1720Z
Disorganized convection paints the sky above a soaked desert landscape. As seen from Highway 93 looking southeast. 10:20 AM / 1720Z

Disorganized convection paints the sky above a soaked desert landscape. As seen from Highway 93 looking southeast. 10:20 AM / 1720Z

By this time, HRRR was trending toward better options further east into central Yavapai county. So I headed east to Congress when a strong cell with a developing couplet started moving in from the southwest, so I headed back south toward Wickenburg on Highway 89. As I cleared heavy rain on some cells popping up overhead, the base of the Wickenburg storm came into view. It was sporting a lowering and a huge tuft of scud was rising up from the ground to meet it. As that merged with the rain free base, the storm had the embryo of a wall cloud.

A wall cloud begins to form beside the forward flank of an approaching supercell. As seen from Highway 89 between Wickenburg and Congress looking southwest. 11:25 AM / 1825Z

A wall cloud begins to form beside the forward flank of an approaching supercell. As seen from Highway 89 between Wickenburg and Congress looking southwest. 11:25 AM / 1825Z

While photographing it, I noticed that the storm appeared to be deviating a bit to the right. So I jumped back in the car and headed further south to avoid getting cut off. During that short drive, the wall could got sturdier as it made attempts at a tail cloud along the interface of a the forward flank. It reminded me a lot of another beautiful supercell I intercepted in Wyoming back in May.

Wall cloud on a supercell north of Wickenburg. As seen from Highway 89 facing southwest. 11:30 AM / 1830Z
Wall cloud on a supercell north of Wickenburg. As seen from Highway 89 facing southwest. 11:30 AM / 1830Z
Wall cloud on a supercell north of Wickenburg. As seen from Highway 89 facing southwest. 11:30 AM / 1830Z

Wall cloud on a supercell north of Wickenburg. As seen from Highway 89 facing southwest. 11:30 AM / 1830Z

Reflectivity and velocity radar of the Wickenburg supercell. 11:32 AM / 1832Z

Reflectivity and velocity radar of the Wickenburg supercell. 11:32 AM / 1832Z

I was so busy trying to coordinate video and photography, and keeping track of overall storm motion that I couldn't relax and see if any slow rotation was present. At this point, if there was any rotation in the wall cloud, it wasn't fast enough to make me think it was about to plant something out in the mesquite and palo verdes. However what was concerning is that the storm was turning even further to the right and I had to hustle out of the way. As I raced south, I started getting shoved around by RFD that was starting to fill in with rain. Once I was clear, I got view of the back of the RFD core and right edge of the wall cloud as it moved away.

RFD partially obscures the rotating wall cloud on a receding supercell between Wickenburg and Congress. As seen from Highway 89 looking north-northeast. 11:35 AM / 1835Z

RFD partially obscures the rotating wall cloud on a receding supercell between Wickenburg and Congress. As seen from Highway 89 looking north-northeast. 11:35 AM / 1835Z

I still wasn't confident if I was seeing low level rotation, but I did call it in to the Phoenix NWS office as exhibiting supercell structure. Looking at the video and time lapse sequences later, it definitely was twirling behind the RFD. The view of the entire cell moving away over the desert was incredible. The dark base and flanking line contrasted against the bright white RFD core and anvil against a deep blue sky. It was spectacular.

A receding supercell thunderstorm dumps rain and hail over Congress, AZ. As seen from Highway 89 looking north-northeast. 11:45 AM / 1845Z

A receding supercell thunderstorm dumps rain and hail over Congress, AZ. As seen from Highway 89 looking north-northeast. 11:45 AM / 1845Z

After savoring the experience, I had a choice between more cells moving into Yavapai County, or a building squall line moving into Phoenix. I was feeling a little hooked on the supercell storm mode, so I didn't head into Phoenix for the amazing show that storm put on. Instead, I repositioned west of Congress for the next line of storms as another cell with a velocity couplet was moving in. Unfortunately, it was surrounded by more developing convection and I only had brief views of structure between morphing rain cores. I was about to make a hopefully decent intercept, but was stopped short as a freight train took its sweet time blocking my best approach.

A striated shelf cloud approaches the intersection of Highway 93 and 71. The rain free base on this supercell was obscured by surrounding precipitation. View is to the southwest. 1:05 PM / 2005Z

A striated shelf cloud approaches the intersection of Highway 93 and 71. The rain free base on this supercell was obscured by surrounding precipitation. View is to the southwest. 1:05 PM / 2005Z

Reflectivity and velocity radar of broad circulation in a passing storm. 1:04 PM / 2004Z

Reflectivity and velocity radar of broad circulation in a passing storm. 1:04 PM / 2004Z

A new updraft base forms to the south of a passing supercell as seen from Highway 71 in Congress, AZ. View is to the southwest. 1:15 PM / 2015Z

A new updraft base forms to the south of a passing supercell as seen from Highway 71 in Congress, AZ. View is to the southwest. 1:15 PM / 2015Z

Once that storm was gone, I decided to take the scenic route back toward I-17 and took Highway 89 to Prescott. The long drive up the mountain switchbacks took me into the dark of the foggy cloud bases where mounds of small hail still survived in places against an onslaught of heavy rain. As I descended the east side of the mountain range I came across several sections of road that had recently seen flooding and had to stop at one point to pull an 8-inch diameter log out of the road while essentially taking a full on shower.

Flash flood debris on Highway 89 just south of Prescott (Had already pulled the huge log out of the road at this point). 2:56 PM / 2156Z

Flash flood debris on Highway 89 just south of Prescott (Had already pulled the huge log out of the road at this point). 2:56 PM / 2156Z

As I made my way into Prescott, DPS was roaming around pulling debris out of the streets. Further in, I passed a storm drain that was fountaining water, and the town was a waterlogged, debris strewn mess. The worst had passed though, and there were no 'turn around don't drown' scenarios to deal with.

Overloaded storm drain in Prescott. 3:04 PM / 2204Z

Overloaded storm drain in Prescott. 3:04 PM / 2204Z

As I made my way up I-17 back to Flagstaff, I skirted the west edge of the weakening line of storms and noticed an eddy on radar moving over east Flagstaff. Looks like this might have been a bookend vortex on the line. I wish I could have seen what that looked like, but that will have to wait for another time.

Reflectivity radar of possible bookend vortex southeast of Flagstaff. 5:06 PM / 0006Z

Reflectivity radar of possible bookend vortex southeast of Flagstaff. 5:06 PM / 0006Z

What an amazing chase. No tornadoes, but three Arizona supercells in one chase day is so much better than I could have hoped for. It has me seriously itching for springtime in the Plains—only 6 or 7 months to go!

Arizona Storm Chase and Supercells - September 27, 2014 from Jeremy Perez on Vimeo.

Video account and time lapse sequences from the chase.

Today, a strong multicell hammered east Flagstaff, dropping up to 2 inches of precipitation including mounds of hail during a 45 minute time frame. Some meager vorticity got stretched into the blue-green updrafts at times and made me wish I had a better vantage.

Hail and Vorticity - July 8, 2014

Still, the view from the middle of town was pretty good as a clearing eventually showed a nice rain free base west of Mt. Elden.

Flagstaff Storm Structure - July 8, 2014

I noticed some laminar striation under the base, but thought it was just an indication of strong inflow. After checking the photos, I noticed that structure may have actually been a shear funnel that lasted a little more than a minute from 4:42 to 4:43 PM.Flagstaff Storm Structure and Possible Funnel - July 8, 2014

I wasn't fully prepared, and decided to shoot a 96 frame time lapse when all I had was a monopod. After Effects stabilization managed to rescue the time lapse pretty nicely.

So much for Virtual Chases. I'm planning to head out to the plains for a few days to try chasing some marginal setups. Not sure if I'll be able to post a forecast ahead of each day, but I'll start with my first opportunity this Sunday.

Target: Northeast Wyoming

With all the frustrations of a flimsy severe weather pattern setting in for the latter half of May, it still looks like there will be isolated/conditional opportunities in the northern plains and elsewhere as a trough moves onshore this weekend and starts cutting off in the southwest early in the week.

For Sunday afternoon/evening, per guidance from NAM, I'm looking at a target in northeastern Wyoming as 40-50 kts of southwest H5 flow moves in over an area of low to mid 50 dew points advects around a consolidating surface low in that target area. A narrow, meridional zone of 1500-2000 j/kg CAPE will develop along the eastern Wyoming border with the CAP weak or open by mid to late afternoon in the northern portion of this ribbon. Today's 12Z NAM forecasts a focal point for convection in this area by 00Z with that area potentially ingesting 100-150 m2/s2 0-1km SRH. Mixed layer LCLs are in the 1500 meter range and heighten quickly the further south you go.

If this plays out well, I might hope to see an isolated, high-based supercell drifting slowly into South Dakota. I have no expectations of anything tornadic with this setup. And if today's 06Z GFS has its way, then I can expect a bust with maybe some elevated showers in South Dakota (GFS keeps surface moisture about a hundred miles further east under stronger capping). 00Z ECMWF agrees better with NAM on placement of moisture and location of precipitation, so I hope that agreement favors my focus on NAM.

This will be my first 2014 chase day during a week of very iffy conditions. I'm definitely concerned that I'm setting myself up for a series of busts, but also excited to take on the challenge.

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Recent Assets

  • US Chase Map 15 May 2015 - without forest
  • US Chase Map 15 May 2015 - with forest
  • US Chase Map 5 May 2015 - without forest
  • US Chase Map 5 May 2015 - with forest
  • Oxford, Kansas Supercell Part 2 - 19 May 2013 - Diagrammed
  • Oxford, Kansas Supercell Part 2 - 19 May 2013
  • Oxford, Kansas Supercell - May 19, 2013 - Diagrammed
  • Oxford, Kansas Supercell - May 19, 2013
  • Newkirk, Oklahoma Supercell - May 19, 2013 - Diagrammed
  • Newkirk, Oklahoma Supercell - May 19, 2013
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