Substantial drought throughout the interior of North America 2018

[harpy]

There's currently a substantial area of continental united states undergoing a moderate to severe drought.  The size of the area is currently abnormally dry to severe drought is roughly 1/3 of the entire United States.  Here's a link to the US drought monitor.

http://droughtmonitor.unl.edu

If this continues into the summer months, I cannot imagine that there's going to be a healthy wheat harvest this year from the united states in 2018. 

I'm not sure what is grown in the South and midwest, but it doesn't look like there's going to be much grown there if this persists for the next 12 months.

[Csnavywx]

This isn't terribly uncommon after a double-dip or prolonged Nina event (-ENSO). Pay special attention to the -PDO in the coming months. If we start getting cooler water off the NW coast and south of AK, it'll probably be game on for a big event. Also, strong negative soil moisture anomalies in late winter and spring often correlate to heat/drought events during the summer. AGW is going to make any event more likely and worse, of course. It's really only a matter of time until a 2012-style event becomes fairly normal.

I'll do some more posting on this tomorrow (wrt graphics).

[A-Team]

isn't terribly uncommon after a double-dip

This year has been really really off in the Southwest, continuing the AGW expected, longer term trend. The monsoon terminated two months early, at the end of July. There have been essentially no winter rains. Not to mention incredibly elevated temperatures and what lifelong residents call lack of any winter.

The annual winter grasses, which used to make the whole area look like pool table green, have not sprouted at all. False starts in previous years -- germination but drying out before seeds could mature -- may have exhausted the seed bank. Prickly pears (Opuntia spp.) are collapsing everywhere. This means the bottom of the food chain, rodents and quail/doves, are working off the odd household bird feeder. Where does that leave the snakes, owls, hawks, coyotes, foxes, bobcats? People here are already living in a martian colony: unbearable temperatures, all food and water transported in.

What I've learned living here is that Southwest airport weather statistics are highly illusory. Things I see on the internet like OSU's Prism or Palmer drought maps have very little connection to ground reality. How many reporting rain gauges actually operate between Tucson and Los Angeles, maybe two over 800 km? Four gauges over 645,000 sq km, an area larger than France. Where are they getting these 1 km pixels from?

A few heavy rainstorms in summer can make total precip seem normal. For the airport. Five km away it didn't rain a drop. Sporadic events don't average out. Those 300 mm heavy rainfalls sink within hours into 500 m of alluvium, perhaps refreshing fossil water down there but losing all relevance to plant uptake. Yet 15 mm x 2 spread out over two days can have a major effect. So in terms of sustainable habitability, the wrong thing is being measured: airport point-precip instead of areal soil moisture and timing. (NVDI doesn't work here).

Meanwhile, the snowpack in the Colorado Basin is what most people watch here (as it provides irrigation and urban water to twenty million people in CA). Those numbers are quite low (graphic) but again they haven't been adjusted downward for applicable conditions, like early melt onto drier soils and enhanced evaporation from elevated temperatures.

Broad-brush statements from afar don't really capture very well what is going on here.

[Csnavywx]

isn't terribly uncommon after a double-dip

This year has been really really off in the Southwest, continuing the AGW expected, longer term trend. The monsoon terminated two months early, at the end of July. There have been essentially no winter rains. Not to mention incredibly elevated temperatures and what lifelong residents call lack of any winter.

The annual winter grasses, which used to make the whole area look like pool table green, have not sprouted at all. False starts in previous years -- germination but drying out before seeds could mature -- may have exhausted the seed bank. Prickly pears (Opuntia spp.) are collapsing everywhere. This means the bottom of the food chain, rodents and quail/doves, are working off the odd household bird feeder. Where does that leave the snakes, owls, hawks, coyotes, foxes, bobcats? People here are already living in a martian colony: unbearable temperatures, all food and water transported in.

What I've learned living here is that Southwest airport weather statistics are highly illusory. Things I see on the internet like OSU's Prism or Palmer drought maps have very little connection to ground reality. How many reporting rain gauges actually operate between Tucson and Los Angeles, maybe two over 800 km? Four gauges over 645,000 sq km, an area larger than France. Where are they getting these 1 km pixels from?

A few heavy rainstorms in summer can make total precip seem normal. For the airport. Five km away it didn't rain a drop. Sporadic events don't average out. Those 300 mm heavy rainfalls sink within hours into 500 m of alluvium, perhaps refreshing fossil water down there but losing all relevance to plant uptake. Yet 15 mm x 2 spread out over two days can have a major effect. So in terms of sustainable habitability, the wrong thing is being measured: airport point-precip instead of areal soil moisture and timing. (NVDI doesn't work here).

Meanwhile, the snowpack in the Colorado Basin is what most people watch here (as it provides irrigation and urban water to twenty million people in CA). Those numbers are quite low (graphic) but again they haven't been adjusted downward for applicable conditions, like early melt onto drier soils and enhanced evaporation from elevated temperatures.

Broad-brush statements from afar don't really capture very well what is going on here.

Here's a good look at the station density.

There's a few stations filtered out, but they're close to other main airfields. That data is primarily for aviation purposes. A smaller reason for that is that these old ASOS systems are a pain in the ass to maintain. The one at my airfield has problems on a weekly basis.

The first thing that popped to my mind for higher-res was the use of bias-corrected radar data. However, PRISM only uses that in the central and eastern US, apparently (http://prism.oregonstate.edu/documents/PRISM_datasets.pdf). Maybe it's excluded due to distortion due to terrain beam blocking and larger radar spacing? Those are the only reasons I can figure. It looks like they use CAI, which is a climo-based field for "first guess". I could see how that would run into a hi-bias during droughts. I think the drought monitor does stream and groundwater monitoring, which might be useful as a sort of proxy.

At any rate, you're correct on the efficiency of groundwater recharge via brief, heavy rain events. I saw some of that first-hand during the big 2012 drought. We had a quick dump of 2" of rain right towards the end of the drought, but you could stick a shovel in the ground and hit dry powder at 2-4" down.

[A-Team]

So there's not a single rain gauge between Tucson and the Colorado River. That's quite a ways, 386 km gap yet gotta love the pretty colors on those drought maps (which often miss the well-established rainfall gradient on the Cabeza Prieta NWR). Quite a bit of our weather is influenced by the nearby Gulf of California and Sierra Madres. Depends very much if you're under a highly variable storm track.

After the 180º bellyflop last time around, I count myself among the non-believers in predictability of Southwestern rainfall from ENSO conditions.

A new publication (can't relocate) said 'oh yes but by cherry-picking major el ninos for the persistent ones, there's a perfect correlation with wetter years, 3/3'.

Next time it doesn't rain, they'll say 'oh yes but by cherry-picking major el ninos over the last century for the persistent ones that started on Tuesdays, there's a perfect correlation, 1/1'.

In my view, too much else is going on now at the level of climate change already attained for sole drivers and legacy data to offer useful seasonal forecasts in the Europe-sized southwestern US.

[Csnavywx]

I forgot about co-op stations!

Of course, looking up recent data for them from the Tuscon NWS page runs straight into a re-direct about the government shutdown.

https://wrcc.dri.edu/summary/Climsmaz.html

[TerryM]

At Murray Springs, south of Tucson, the recent undercutting can be contrasted to the steady buildup of land since Clovis Man killed and devoured the mammoths.
Were mammoths extant today, what would the herd find to nosh on in this now desiccated region?


Drought has been the norm in the Southwest since the Black Band strata was laid down during the Younger Dryas.
Terry

[Sigmetnow]

The Drought Monitor is not simply based on precipitation.

“It’s not based on a statistical model. It’s based on many indicators and observations, not just precipitation.”

Who produces the U.S. Drought Monitor?

The U.S. Drought Monitor is a joint collaboration of the U.S. Department of Agriculture, the National Drought Mitigation Center at the University of Nebraska-Lincoln, the U.S. Department of Commerce and the National Oceanic and Atmospheric Administration.

Authors from the partner agencies take turns assembling the map and accompanying narrative summary each week. The author edits the map based on several climate products, and on feedback from an expert observer network.

The map production process occurs at the National Drought Mitigation Center, based at the University of Nebraska-Lincoln. This consists of creating the various maps, statistics, GIS data and other products that are distributed each week. 

  http://droughtmonitor.unl.edu/AboutUSDM/FAQ.aspx

[gerontocrat]

I remember writing (probably in error) some time ago that while drought in the UK is defined entirely by (lack of) precipitation, in the USA it's all about soil moisture. Perhaps in the USA it is a mixture of several parameters?

[harpy]

Temperatures in the continental US are incredibly warm for February - if this warm weather continues into march and April, crop failures are likely as soil moisture is already very low, and there's no snow cover.  Winter wheat will fail if there's any killing frosts in April.  I would suspect even without a killing frost the lack of soil moisture is going to lead to crop failures this year.

It's just a watch and wait at this point.  We'll have much more information in May and June.

[Daniel B.]

Gerontocrat, you are correct.  In the U.S., soil moisture content is estimated from the temperature.  Since temperature has increased, the Pdsi has shown a drought increase, while other calculations have not.