Southwestern Monsoon Discussion - 2020

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Figured it was time to start this annual thread since we are about 3 weeks away from the average start of Gulf and/or Pacific RH working into the southern parts of Arizona and New Mexico.

With such a crappy tornado season, I was wondering how many chasers are eyeing the monsoon as a back-up adventure this year? Most of Arizona is low-COVID except for Phoenix.

For me, the ever-increasingly extreme dust storms are my main target early-on. You only get a few (2-3) shots at a good dust storm, because once the ground is saturated, it's harder for repeat performances. We did not have a hard freeze this year in the deserts, so without the small plant particles we might not get the "big-one" unless everything sets-up just right. It is bone dry right now (see SPORT data below) and no precipitation is expected between now and the start of the monsoon -- e.g., no tropical activity.

After nixing 2020 plains vacation plans, I've been pinning hopes on doing more monsoon day trips this season. Last year I put some effort into plotting out spots with good visibility and decent data reception to work remotely while waiting for storms to fire up. Focusing on the MRCZ in northern AZ again, but eyeing strict boundaries not to cross into the Navajo Nation. They're being hit really hard by the virus and I don't want to add to aggravations for them even though I'm staying isolated. There might even be a couple days of pre-season moisture next weekend pulling in from an AZ/NM high pressure between cutoff lows.
Last edited:
Mar 15, 2007
Essex - UK
Scuppered here as well as Tornado Alley and called off our Arizona Chases this week due to ongoing outlook that no Trans Atlantic Flights will be happening anytime this side of Autumn. So its Tornado and Monsoon Season game over for us this year.
Monsoon dust storms coming soon to AZ and NM. Just a reminder that dust storms are a constant hazard. Remember to get off the road (exit if possible) and take your foot off the brake pedal. If you can get all the way off the highway safely, that is even better. These storms come up quickly and what seems like a small amount of dust and rapidly turn into a blinding wedge of dust. Don't think you can simply drive through it. I-10 in Arizona is very dangerous, especially between Tucson and Phoenix. As some of you know, I saved my own life by pulling off the road during a dust storm in Colorado. The DPS car seen below was fortunately unoccupied.

Looks like some RH will begin to trickle into Arizona over the course of the next week, but a system moving in from the west will move storms east. This is not a good set-up for mega-dust storms in Phoenix and central Arizona. Travelers near Wilcox and the AZ / NM border will need to be watchful of outflows. This is a good set-up for isolated thunderheads. It looks like the big show will begin to take shape after July 3rd as the 500mb flow turns east.
Monsoon is here! Wednesday (7-1), is still questionable, but Thursday+ looking good for all monsoon hazards. Latest soil moisture content data (inset) shows very dry / undisturbed soil, so major dust storms are likely over the next 3-7 days. I went out on Monday and surveyed the ground between Tucson and Phoenix and it's like talcum powder. Just walking on it creates a dust cloud.

The upper-level winds should be moving storms N/NW allowing them to mature and consolidate outflows in favorable direction. Pretty difficult to forecast monsoon storms too far in advance as a lot depends on cloud debris from the previous day's activity in Sonora, Mexico and the unpredictable surges of RH from the south. (The RH on the day of the ultra-massive dust strom in PHX (7-6-11) was 31 ºF at 3pm in Tucson).

I should note that the majority of epic-class dust storms occur within the first week of increased activity.

Needless to say, if you are coming out to Arizona to chase, we are having a major resurgence of COVID-19.

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I'm not goin' near Arizona right now, but do have hope that some of that moisture will make it up into southern Colorado by Friday or Saturday. Did you mean the dewpoint was 31F at 3:00 p.m.? Dry for getting much rain, but good for that dusty outflow you're looking for.