Chasing Structure in the Southwest Monsoon

[Jeremy Perez]

Hi folks,

This is my first post. I really appreciate the wealth of experience being shared here, and I've been absorbing loads of information and inspiration throughout the site.

I have had a long interest in observing and photographing thunderstorms and other atmospheric phenomena, but recently I've been trying to move my understanding of storm structure and behavior up a few notches. I live in Flagstaff, Arizona, and get to watch some beautiful storms build and live their short lives on almost a daily basis during the summer monsoon.

This summer, I put a little more effort than usual in watching for more robust storms and trying to catch a rare Arizona funnel cloud in the act. I'm not surprised that I wasn't successful, but storms were tornado warned two days last month, as we got some really good action from a couple early-season troughs that stirred the monsoon moisture into a lovely froth.

Because monsoon storms seem to be highly terrain driven, I'm not really sure how to analyze the structure of a severe storm compared to how someone would look at severe weather in the plains. I'd really appreciate your input on a few photos and time-lapse animations I shot of a couple storms last month, to see if I'm focusing on the right places.

The first is a storm that formed southeast of Flagstaff, and was crawling northwest. As I drove eastward toward it, I noticed a lowering where the inflow seemed to be strongest. I was interested by the curving bands of cloud that arced up to it. This structure was positioned on the north side of the storm as it moved northwest. The photo can be seen below, and a very short animation can be found here: YouTube Time Lapse

 

[Jeremy Perez]

Not sure if I can add more than one attachment per post, so I'm separating this into two more posts.

A few weeks later, I caught the backside of another storm as it formed west of Flagstaff. Bands of cumulus were feeding into it from the east while the storm as a whole was moving west-northwest. The most interesting inflow structure was on the northeast side while heavy precipitation was falling along the southwest and west sides. It appeared to be competing with a pulsing updraft on the southeast side of the storm, but the northeast structure had such a nice, steady column working for it, that I shot a time lapse of it. One photo can be seen below, and the time lapse can be found here: YouTube Time Lapse.

At about the 5 second mark in the time lapse, I zoomed in on the structure right as the inflow seemed to converge enough to put a bit of a spin on it. At this point, it seemed to be getting too far away, so I stopped shooting and packed up to try to catch up with it. A couple minutes after that, a flattened, bell-shaped cloud condensed below this structure and hung just above the tree line for several minutes. I'm kicking myself that I didn't stop the car to at least get a consolation shot of this.

 

[Jeremy Perez]

I drove west down I-40 through blinding rain to try and get parallel with it in a spot that wasn't blocked by cliffs, hills and trees. When I finally found a clearing off the highway and spotted it again, the low base of condensation was gone, and I felt that I had just missed the best ten minutes of its life. However, it had a beautiful, long, thin arc of cloud peeling away and downward to the north. I wondered if this was what you might call a tail cloud.

I was able to start photographing it again just as this cloud started to dissipate. You can see a very short time lapse of that at the tail end of the time lapse I linked above. The photo is below. A full report and larger photos can be found at my website: Northern Arizona Storm - August 30, 2008

So, the main thing I'm wondering is whether I'm just picking up random turbulence in these structures, or if I'm actually watching the 'right' spots for potential funnel clouds in these unruly monsoon storms. I really appreciate any insights anyone can offer as to how to chase these peculiar creatures. Thanks for taking a look.

 

[Jeremy Perez]

I was just rescanning the forum, and it occurred to me that I should have posted this into the Sticky "FAQ: Chasing the Southwestern Monsoon" at the top of the forum. I was a bit nervous when posting and wasn't thinking as clearly as I should have. If a moderator were inclined to move the above posts into that thread (if it's not too much trouble), I'd be relieved. Very sorry about that.

 

[David Wolfson]

For the most part monsoon storms develop under very slack anticyclonic upper air flow, so you won't find mesocyclone-type supercell structure. Rather tornados as they occur are of the landspout variety. Although I'm far from an expert on the subject, I've seen my share.

From my observation these landspouts arise at the interface between a mature storm's outflow and the inflow to a new pulse storm. Such an interface is pretty common with the monsoon's pulse storms, as are various transient features like tail-clouds, small-scale visible rotation at cloud level, and gustnadoes. Rarely do the conditions line up in one place for long enough to stretch and spin up a significant vortex from the surface to the typically high cloud-level qualifying as a landspout.

So the area I'd be watching is the gnarly rainfree base of new development that is able to stand up to its neighbors' gustfronts for a rather long time at one location.

I think your excellent pictures are examples of the above process that made it farther than many storms do, but not quite to the landspout.

Now, especially near the end of the season as some upper southwest flow begins to re-establish while there's still a low-level moist flow remaining from the south, you can get conditions that favor some supercells.

Today is in fact a marginal example of such conditions IMHO. There's a pretty good upper flow and 20+ kts at mid-level with 60+ dews left around -- enough progged CAPE and helicity to be interesting. The low-level gradient is slack into the heat low, however. I would be looking northwest of Phoenix, e.g. the Wickenburg vicinity and up toward Prescott, where the orographic effects should enhance the rotation of any supercells that manage to develop. Almost but not quite enough to embarass myself with a FCST thread as I write this, FWIW.

 

[Jeremy Perez]

David, that's very helpful. Thanks for your thorough message, I really appreciate it. I'm feeling pretty excited about conditions today too. The nocturnal cloud layer seems to be burning away nicely already (8:40 AM) and the cumulus that are popping up along the rim are shooting quite diagonally to the northeast. I may have to take a late, long lunch and see what rears its head today.

 

[Richard Dickson]

Today is looking quite promising here is Arizona. The SPC even has a 2% tornado circle that would cover roughly a third of the state. That is rather rare for us. The current RUC shows CAPE values in excess of 4500 J/kg over an area north and east of Yuma. Twelve hours from now still shows a very decent area in southwest / south central Arizona. We are getting some rapid cumulus buildup here around Casa Grande at 1000 local time.

I thought David did an excellent job of describing the conditions that it takes to make a tornado here in Arizona. Having lived in Kansas for forty years before moving to Arizona makes me appreciate the differences between the two areas and their storm patterns. I’ve had a long running humorous battle with a fellow that I used to work with and his insistence that “it really was a tornado because it blew the awning off of someone’s mobile home in Glendale and turned over their patio furniture”. Quite a difference between that and having neighborhoods removed.

I believe I am going to go west from Casa Grande and hang out around the Gila Bend area for a while to see what develops. I agree with the comments about the Wickenburg to Prescott area for later this afternoon, but I want to keep my options open for now. I got burned yesterday thinking there would be more activity around Casa Grande than what actually developed. I should have headed to either Cochise or Yavapai Counties. Oh well, I still got some nice sunset photos. Just to ‘rub it in’, it is wonderful being retired and having the chance to chase when the opportunities are ripe.

 

[Jeremy Perez]

Heh, I'd probably rub it in too if I were you

There's something to be said for living vicariously through other's chase opportunities!

Some early storms popped up and blew through Yavapai and Coconino counties (firing up right over Prescott, btw). Another double-cell was tagged with a severe warning up in central Navajo and Apache counties at about 12:30 MST. There's been enough scattered cumulus everywhere, that it's hard to get a good visual look at the larger cells. Hopefully there will be a late afternoon surge that will coincide with my ability to get my non-retired behind out of the office a bit early, head west toward Williams and see what I can find.

I hope Casa Grand/Gila Bend offers something up for you.

David, thanks for making the FCST post after all!

 

[Ed Boik]

I just moved in March from the HP wonderland of the midwest to the west valley of Phoenix. I was surprised by the high base of the storms storms and the way they appear to erode from the bottom-up as they precipitate.

They have made for some phenominal lightning photography opportunities.

Haven't chased yet, still getting settled here and my four kids keep my chases limited to the backyard and the end of the block.

 

[Jeremy Perez]

Things didn't seem to congeal much for strong storms in Yavapai and Coconino counties yesterday afternoon. Would it be reasonable to say that because the storms in that area got started early, that there wasn't a strong enough cap to let the energy build up for something bigger later in the day? Would those early storms be considered Joule Thieves?

As I watched the satellite view, there was a mighty cell that started over Yuma and boiled north along the Colorado River all day. It was warned as severe for a few hours. Did anyone get a chance to get a look at that one? And Richard, there was a smaller cell that blew up over Gila Bend and was warned as severe until it got murdered over Tempe. Did you get a chance to check that one out yesterday?

Ed, I hope you get a chance to take advantage of those high-base storms and find some nice lightning opportunities before the monsoon fades out for the year.

The smaller cells we did get up here were enjoyable to watch. The anvils had a nice long stretch to them, but the ones I saw weren't very active lightning producers. As the sun dipped below the horizon, they fell apart, but put on a nice sunset display. That low sun angle really shows off the mammatus drooping off the anvils.

 

[Richard Dickson]

Jeremy,

I won't say that it was a wasted trip yesterday, but it didn't go as well as I had planned. I did the Gila Bend and later on to Buckeye expecting the cells out at yuma to move into that area. Like you indicated, they went northerly instead of northeasterly. I took a back road that I hadn't traveled before from Buckeye to Wickenburg. The cells in the area north of Wickenburg were weak and not well organized. I got into position for the warned cell coming up from the Tonopah area a little before sunset and tried some lightning shots without great success. They were just too random to work with.

I turned off of AZ 74 onto I-17 about 2000 and knew I was in trouble right away. All of the lights of Phoenix just simply disappeared. I was 'white-knuckled' by the time I got through the construction zone in an absolute downpour that ended at the 101 loop on the north side of Phoenix.

After traveling all day, the best lightning was just south of Casa Crande where I live. I wound up with some decent shots for my skill level and got home after midnight. I also tried to photograph two rattlesnakes in the road on the way home, but they didn't seem to appreciate the publicity and headed back to the brush. I don't remember having seen two traveling together before. Tonight may be another good opportunity here in the southern portion of the state, so I believe I'll just stay around here. I'll probably scare them up to your area.

 

[Richard Dickson]

Ed,

You mentioned watching some clouds eroding from the base around here. Don't know if you have witnessed one of these yet, but I get a real kick out of them. A small, rather tight, cumulus cloud struggling to rise will suddenly break through the cap above it like there had been a hole poked in the top and within about five minutes will have reformed just above where it had been. Really fun to watch this happen. Not a big deal, but I always video those when I see them.

 

[Susan Strom]

I turned off of AZ 74 onto I-17 about 2000 and knew I was in trouble right away. All of the lights of Phoenix just simply disappeared. I was 'white-knuckled' by the time I got through the construction zone in an absolute downpour that ended at the 101 loop on the north side of Phoenix.

Geez I must have passed you on the road. I went northbound on I-17 and ended up using westbound AZ 74 to shoot from. I arrived 74 just at the last light of sunset; saw the black raggedy underside of the Wickenburg cell. Electrified storms continued to build to the east of the Wickenburg cell; so I went for the new lightning and "shot" from a small road at the Ben Avery rifle/pistol range.

 

[Richard Dickson]

Susan,

I didn't look at the side road there by Ben Avery, but now I wish that I had. Even though you were about to get wet, I would have really enjoyed meeting you and see what sort of luck you were having that evening. I did my best work that day at your old favorite stomping grounds. We had a very nice display down at the Sawtooth Mountains again.

I did come across another photographer on AZ 74 as you come down the big hill on the west side of the entrance to Lake Pleasant. He seemed to be in a hurry to get his gear picked up before the Wickenburg cell got to us so all I did was a quick 'Hi and Howdy'. Didn't even exchange names.

It's not a big deal, but I'm very surprised with the number of ST members showing up on the threads that are from Arizona. We may have to start our own Chapter someday. (Just kidding!) I'm secretly hoping that the rest of the country doesn't find out how great the living is here for most of the year or they would all want to move out with us.

 

[Susan Strom]

That's funny. I was probably just a mile or two away from you and the other guy near Lake Pleasant. I did get wet too; rain was pretty heavy. I drove a lot that night.

I think our desert has a share of chase convergences. The other night there were other photographers in the McDowell Mtns alongside me and someone running data on his laptop. There are a lot more chasers in Arizona than most people think.

When you think about it, it makes sense. You can live with nice weather, but if you want to chase, it is not a bad place to be. In the Spring, you're a day's drive from the West TX dryline. After Plains work in May & June, the Monsoon starts in July and runs into September, and is capable of very extreme weather. An Arizonan has access to chasing from April to Sept, technically.

Another feather in Monsoon's cap is not having to worry too much about tornadoes dropping in the dark while you're out there doing lightning photography. However there are other dangers...heat, sandstorms, flash floods, downed lines, hurricane force winds, crazy lightning amounts and torrential rain.

Sixty powerlines down that night in the southeast Valley. Pretty typical for a Monsoon night.

Hope you had fun out on 74!