Southwest Monsoon 2019 Discussion

[Warren Faidley]

There could be a "perfect storm" situation setting up for a mega-dust storm this weekend near Phoenix and surrounding areas.

1: Delay of monsoon. The monsoon typically starts during the first week in July. This extra heating time has removed a substantial about of moisture from the 0-10 cm soil content, especially east of the Phoenix area. (See chart below).

2: The initial onset of higher RH figures (55ºF+ dp's) will likely come in 1-2 day surge, preventing soil from being moistened over a period of time. The July 6, 2011 mega-dust storm had 35% relative humidity at noon in Tucson, holding at 31% at 3:00 pm.

3: There is likely more dead, vegetation particles on the desert surface after two hard freezes this winter. This was a contributing factor to the big dust storm in 2011 according to research involving particulates recovered during the storm.

The wild card will be how the storms form and move. In 2011 they formed in severe (broken) lines near Tucson northward and the outflows were able to consolidate as the storms moved west / northwest. The models currently show typical southeast monsoon flow at 500mb and 700mb, slowly moving storms in a favorable n/nw direction.

 

[Marc R. O'Leary]

I can't f-ing wait! Colorado monsoon is just a hair above traditional storm season in my "let's get out there" scale. Give me some dry lightning!!

 

[Jeremy Perez]

Thanks for getting that discussion started, Warren. The UofA WRF models only have the GFS CAM in range so far, but it hints at Friday possibly being a day to watch for a starter round. The 4PM PHX sounding shows steering flow could nudge incipient storms westward/northwestward into the valleys with anvils knocked out of the way, northeastward. Surface convergence could also be aided with westerly surface winds if that panned out.


CAPE doesn't look all that great on the surface plot, but the reflectivity model shows convection getting off at least one round from that down in the desert.




With the soil nice and crispy like you noted, that could be a fun I-8 haboob surf. As usual, need to see if that trends, and if it shows up on the NAM & RR, or if it moves off to the weekend or later.

Might have to make a trip down off the rim...

 

[Warren Faidley]

Yes. NWS Phoenix also mentioned Friday and/or Saturday (in addition to Sunday). I'm not sure if the rh is going to be elevated enough to produce and support a line of high-topped, severe cells needed to create apocalyptic dust. If they only dampen the soil, it really reduces the odds of a big show. Just hope people will keep the hell off the freeways when these things come ripping.

 

[Steve Miller]

This is exciting as I have a trip to Sedona, AZ planned for this weekend. Perhaps I'll chase my first #haboob?

 

[John Moore]

Warren - around Phoenix the deserts are covered with thick grass - a couple of invasive species, which is why our fire situation is precarious. I don't know about the situation in your area. I wonder if that grass will hold down a lot of the dust.

I suspect we'll get a chance to find out.

 

[Warren Faidley]

Yea, I don't think the grass will do much to prevent a big dust storm. During past storms, most of the particles were picked up east and southeast of Phoenix. I did a minor survey last week near Casa Grande and Eloy, and it was dry as a bone. We will know soon enough!

 

[Mike Olbinski]

Not much grass south of Phoenix between Gila River and Picacho Peak...that's where the dust comes from. And the Maricopa area. Could be a few of them Friday-Sunday, we'll see how good they are.

 

[Marc R. O'Leary]

Not much grass south of Phoenix between Gila River and Picacho Peak...that's where the dust comes from. And the Maricopa area. Could be a few of them Friday-Sunday, we'll see how good they are.

Looking forward to what you come up with this monsoon season Mike. Love your work!

 

[Mike Olbinski]

Thanks Marc! Been a little tired from spring, but hoping to catch a second wind starting tomorrow haha

Looking forward to what you come up with this monsoon season Mike. Love your work!

 

[Jeremy Perez]

For Friday, 12Z WRF-NAM and WRF-RR both favor the idea of outflow dropping off the Mazatzals from the east. Not the primo dust source. The RR does show an option for weaker outflow moving up from the south, off weaker convection. Moisture isn’t great, especially further west, so storms may not propagate and reinforce the gust front. The wind forecast still looks encouraging though.
.

12Z WRF-GFS25 is more optimistic with moisture content in the southern deserts and firing storms in Pinal County, which would be a better dust source, although with weaker winds for reasons I haven't worked out.


I don’t chase these as much as the desert dwellers, and I don’t have time to see how well the models are initializing. But it seems encouraging enough to head down—if anything, to work on getting better with haboob tactics, and maybe get something unexpected.

 

[Mike Olbinski]

Saturday and Sunday have chances too.

I will say, storms from the Mogollon Rim with strong outflow going through Phoenix towards Maricopa is what caused July 9th last year So it's not bad, but you do need pretty strong storms for that to happen.

 

[Jeremy Perez]

Hoping by tonight to have a better idea whether to store up energy for Sat/Sun instead of Friday...

Mike Leuthold also just posted discussion for today/tomorrow and this overall start to the monsoon pattern:

20190711

General Discussion These forecasts discussions sure have been few and far between so far as the monsoon continues to sputter. It’s just...

arizonawrf.blogspot.com

To anyone who hasn't ventured to his blog, he provide a great resource for AZ monsoon meteorology. Not to forget, the models he maintains here:

UA Hydrology and Atmospheric Sciences

The University of Arizona's Department of Hydrology and Atmospheric Sciences.

www.atmo.arizona.edu

 

[Warren Faidley]

Still counting on Saturday or more-so Sunday as the possible big days. The hardest thing to predict are often the debris clouds left over from local activity or a decaying, Sonorian MCS. Such cloud cover kills the CAPE. Friday has potential only because the dust bed is undisturbed and any organized outflows could easily lift the fine particles. The epic dust storms really need the combination of elements as noted above.

Edit: Having checked the 18z RAP, there is a hint of a rapid, surface moisture surge tomorrow at peak heating. So tomorrow would be in play if the rh holds.

 

[Warren Faidley]

Really boring monsoon so far. One of the latest I can remember -- rh wise.

The low rh and overall lack of energy and supporting upper-level flow has really put a monkey wrench in the progress. The areas between Tucson and Phoenix remain bone dry (or drying out from light showers). The 110ºF+ temps are really frying the small plants, making an even more dramatic dust storm possible. Phoenix forecasting 114ºF tomorrow (7-16). Looking at Wednesday or Thursday as the next potential targets as a surge of rh and gravity waves / eastern flow disturbances could load the gun. Still possible to have a world-class dust storm in the next week.