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July 2016 Southwest Climate Outlook - Climate Summary | CLIMAS


July 2016 Southwest Climate Outlook - Climate Summary

Thursday, July 21, 2016

Precipitation & Temperature: June precipitation totals generally were average to above average in Arizona and New Mexico, with the exception of southern Arizona (much above average) and the Four Corners region of New Mexico (below average) (Fig. 1a). Temperatures were above average to record warm across most of the Southwest (Fig. 1b), with two periods of extreme heat (June 3–5 and June 18–20), the latter of which resulted in multiple fatalities in southern Arizona. As of July 20, temperatures this month have remained mostly above average across the Southwest (Fig. 2). 

Monsoon: Following a strong start to the monsoon in late June, there was a considerable decline during much of July, aside from sporadic storms that pushed into the southeastern corner of Arizona (Fig. 3). This decline, or “break,” is associated with a shift in the monsoon circulation patterns, in which a high pressure ridge diverts moisture and storm activity away from southern Arizona (see Monsoon Tracker for more information).

Drought & Water Supply: Long-term drought persists across the Southwest (Fig. 4), reflecting multiple years of drought and accumulating precipitation deficits. The southern half of Arizona and the western edge of New Mexico are experiencing moderate drought, while most of the rest of these two states are designated as abnormally dry. Water year precipitation to date in Southern California, most of southern Arizona, and western New Mexico is below average (Fig. 5).  Lakes Mead and Powell in Arizona and Elephant Butte Reservoir in New Mexico are at 36, 57, and 14 percent of capacity, respectively (see reservoir storage diagrams). Lake Mead is of particular interest, given water restrictions that would be triggered were levels to drop below critical thresholds (see CLIMAS 1075 podcast series).

La Niña: Sea surface temperature anomalies and atmospheric patterns all indicate ENSO-neutral conditions. Most models point towards the formation of a weak La Niña event sometime in late summer or early fall that is likely to last through winter 2017. Some uncertainty remains regarding the strength and timing of the event (see La Niña Tracker).

Wildfire: Given the abundant fine fuels that grew following a strong monsoon and tropical storm season in fall 2015 and given the warmer- and drier-than-expected conditions in winter and early spring 2016, there was concern over the possible severity of wildfire in 2016. Relatively cooler and wetter-than-average conditions (linked to the lingering effect of El Niño) tamped down early-season fire activity in April and May. Fire activity increased in June, but numerous precipitation events, a strong start to the monsoon, and increased relative humidity across the region helped limit the risk of severe wildfire. As of July 20, wildland fires had burned approximately 177,000 acres in Arizona and approximately 135,000 acres in New Mexico. Much of the fire activity this year has been managed for beneficial use. With the onset of the monsoon and the associated increase in precipitation activity and relative humidity, the window for severe fire is nearly closed.

Precipitation & Temperature Forecasts:  The July 21 NOAA-Climate Prediction Center’s one-month seasonal outlook calls for increased chances of above-average precipitation for most of Arizona and western New Mexico (Fig. 6, top), and increased chances of above-average temperatures across the entire western United States (Fig. 6, bottom).

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