Monsoon Diary

[Joe Zemek]

Monsoonal return

Latest ETA sez Tuesday pm looks pretty good. I look forward to finishing the roll of film from last weekend (got a nonrotating wallcoud N of Casa Grande! Too bad I'm an amateur nighttime lighting photog, so I bracketed the cr@p out of it and am hoping I got something). Got pounded by dust front and rain driving back to PHX, and did not see one photogenic CG in range. But the CC was constant and spectacular.

 

[Dave Chapman]

8/14 Phelan Tornado

Southern California deserts get their own taste of summer monsoon weather on occasion. Last Saturday (Aug. 14), my wife and I saw a small tornado in the high desert west of Hesperia:

http://www.kickbully.com/Storms/phelan-tornado.jpg

We were driving back from a hiking trip in the Sierras when I noticed some towers building just north of the San Gabriel mountains. Convection in Southern California usually tops out fairly quickly, but two cells were developing more like the early stages a Plains supercell, with deep sustained updrafts over darkening bases.

I kept waiting for these cells to collapse, but instead watched as dark, rain-free bases developed on one cell a couple of miles to my southeast, and another the same distance to my southwest.

At the edge of the cell on my left, a very strong spin-up occurred. This was only a couple of hundred feet away and small debris was caught up in the circulation. Then a small tornado developed directly under the rain free base of the storm on the right, only about a mile away.

The tornado moved very slowly across open desert for about 10 minutes before dissipating in a cloud of dust (mistakenly reported as a 1/2 mile wide tornado by spotters).

Both cells soon became outflow-dominated, and we waited out the storm in the Hesperia mall. Flash flooding occurred nearby and nearby lightning and downpours seemed out of place for a Southern California summer.

 

[Cstok]

Nice pic Dave!! Thanks for sharing. That looks like an RFD notch on the right hand side of the picture... can you confirm?

 

[Dave Chapman]

My initial take is that the notch was due to uneven convection rather than a downdraft. There was no apparent mid-level rotation to generate an RFD and the notch is on the northern perimeter of the main updraft (fed by 10 mph southerly winds). If weak upper winds caused that feature, it did not appear to be significant to tornado development.

In looking for a possible cause of tornadogenesis, my bet is on the downdraft that had just formed to the south. The leading edge of the rain-cooled outflow probably created weak horizontal shear, which was soon stretched vertically by an unusually strong updraft.

 

[David Wolfson]

I'd probably think differently if I were there, but it looks to my jaded Arizona eyes like a rather common "gust devil" or "dustnado". Yesterday I was watching several in the distance and waiting for a decent picture at a Monument Valley overlook. They were also persistent and extended toward and occasionally even "into" a rain-free updraft cloud zone in the vicinity of a developing thundershower.

My own feeling is that for a whirl to be a "nado" you should have evidence of a condensation funnel somewhere below cloud base in the updraft column. That's what's usually missing IMHO.

 

[Dave Chapman]

Because of the desert location, I was looking at things a little differently. I may have been mistaken, but I assumed that the air was too dry for the drop in pressure to cause sufficient adiabatic cooling to create a visible funnel. Also, because the vortex was traveling over very hard desert soil, and lasted only a few minutes, there wasn't sufficient dirt or debris to vacuum up to the cloud base.

However, in terms of strength, height and shape, the vortex was very typical of an F1-damage potential tornado (my digital camera unfortunately did not pick up the less visible portions of the funnel). I had just seen a strong dust devil a couple of minutes earlier, and when I saw this new vortex, there was no doubt in my mind that I was looking at a tornado.

Impossible to verify, but I tend to be overly cautious about calling anything a tornado without clear visual evidence.

 

[David Wolfson]

Dave, you'd have some heavy-duty convincing to do to before I'd buy anything like F1 from that picture! TTI, much more spectacular dust devils than that don't even nearly make F0. It's truly amazing how much dust and crap some of those energetic little vacuums can pick up. With the rare one that might rate F0 you see pieces of tree and humongous amounts of dust, unless it crosses a populated area, in which case you see empty trash cans, sheet metal, and more stuff than you ever thought could be loose in someone's backyard dancing hither and thither.

Agreed about the dryness inhibiting lower-level condensation, but I'd still personally want to see some protrusion or at least some circulating scud below cloud base before I'm convinced. That said, I wasn't there and you were -- doggone it! :salute:

 

[Dave Chapman]

Good points...I've learned my lesson. Definitely not F1 in appearance, especially compared to a mesocyclone tornado.

 

[Joe Zemek]

Last hurrah

Well... I'm somewhat conflicted about posting given my apparent jinx effect... but the MRF has shown for *two whole days now* that, beginning of Labor Day weekend, a tropical system will be drawn deep into AZ by a strong Pacific trough. Now, even if this forecast pans out, it could be a cooler, heavy rain event with the occasional thunder rumble, but that much juice and a 500mb jet that counts as high speed shear for this part of the country are exciting.

Pray... for... storms!

 

[Susan Strom]

After storms lined up like planes on a tarmac the week of 8/14, skies have been calm, blue and quiet since then. Signs of fall in the air? Actually, based on past experience I would say no, not quite yet.

Since I started chasing Monsoon 8 years ago I always notice around the third week of August there is a break, which as it turns out is rather typical and expected.

Will the fur start to fly again? If I were to lay money on the table I would say yes. What do I base this on? My past experience year after year with the Monsoon has always included September activity, particularly around Labor Day. Actually, the storm gods must have been smiling on me during years past, because early to mid September like clockwork brought strong storms with torrential rains, frequent lightning and moody temperaments prior to the Monsoon sputtering to a close a couple weeks later.

Rain-washed September evenings bring me images like this one, one of my favorites from fantastic 92-day pattern year 1999. http://www.lightninglady.com/photos/LLHighEnergy.jpg
This was taken during the second most violent Monsoon storm I have ever chased. I will never forget how the lightning looked that night, like Zeus having a mood swing.

Although it is true that drought conditions and urban heat islands kept some 2004 Phoenix Monsoon activity at bay, I remain optimistic for an encore or two especially in the desert foothills before we see the last of the Monsoon mid to late September. It's like what prospectors say: "Pan for gold where gold has been found before." I'm going to roll the bones and say that storms will be back at least for a couple more chases in September. Cameras are near the door.

If the sky remains clear though, I'll call for reinforcements and invite Greg Campbell of Tucson, who is a bit of a good luck charm, again up for a chase. Every time he visits Phoenix I swear he brings Tucson's lightning with him.

 

[John Farley]

Levy NM storm 8/14/04

This was not quite a monsoon storm, since it was more associated with a shortwave passing over NE New Mexico, but since 1) it was in New Mexico and 2) there's no reports thread on Target Zone for that day, I thought I would say a few words here about a spectacular storm my wife and I watched from near Levy, NM on 8/14/04. This SVR-warned storm produced a large, menacing wall cloud that showed rotation at times, and loads of CG, along with hail in the Eagle Nest and Cimmarron areas that completely covered the ground in some places.


Details and pictures at:

http://www.siue.edu/~jfarley/chase81404.htm

This was the only day we went out actively seeking storms, but the next day there was quite an impressive storm just northeast of Santa Fe, where we were staying, that caused serious flash-flooding at the Bishops Lodge (where we, fortunately, were not staying). The cars of a half-dozen employees ended up in a mud-covered pile, and several rooms were flooded and had to be re-carpted.

 

[Howard Robinson]

Hey Susan,

Nice updates on the monsoons, I remember when I lived out there was a break in August.

But, I do recall that when I was up in NorthEast Arizona during the last week of August, that a huge thunderstorm was building while I was in Sanford. Listening to the radio, they called it for SVR and I left to go back home to Phoenix. The darn thunderstorm chased me all the way back to Marcopia line. Got to see awesome lighting behind me.

 

[Susan Strom]

John, nice chase account. New Mexico can deliver the goods sometimes, most definitely. My first lightning chase in '04 was on the Sandia Crest

Hey Howard...
A Pacific storm, Hurricane Howard is currently 405 miles SW of Cabo San Lucas Mex as of 8am PDT 9/2. I'm keeping a (hopeful? wishful?) eye for the off chance that tropical moisture from its breakup will edge toward the Baja and feed moisture into Arizona via any weather disturbances that may occur. That would not be an uncommon setup for this time of year. Make a wish, raindance, break out the magic lamp. Although I hope for a last charge of activity before the Monsoon season starts to wind down, doesn't wishing for a hurricane feel a bit ironic today?

Howard-watching? Mexican satellite is available here: http://www.earthwatch.com/SKYWATCH/IRMEX2D.html

 

[Susan Strom]

A quick but punchy storm blew through lastnight in the East Valley PHX about 5pm. Mesa had large numbers of trees down and power lines across the road. Upon returning home more trees were down and street lights/signs were damaged and power had been out. It was reported as straight-line wind damage. Quite substantial actually.

Interesting weather continues. Does the Holiday Factor occur for Labor Day in Arizona too? Seems to. Interesting, Tornado Warning at this very moment for Forest Lakes up in the Rim Country (about an hour up the road). Atmosphere is very unstable. Could be a day of surprises in the Southwest. Good morning! Out the door.

 

[Greg Campbell]

Things are still quite dead in Arizona. I've seen a few scruffy storms over the last few days, but they invariably fall apart as soon as they loose direct solar heating. With dewpoints in the 50's (45 today) you can't expect much....

-Greg