Southwest Climate Outlook July 2015

Date issued

Precipitation: In the past 30 days, much of New Mexico and portions of eastern Arizona recorded above-average precipitation (Fig. 1). We are closing out one of the driest times of year, climatologically speaking, and any amount of recorded precipitation can push monthly totals well above average. To that point, we saw anomalous incursions of moisture from tropical systems in early to mid-June, as well as an early start to monsoon-associated precipitation in mid- to late June (see Monsoon Summary, page 5-6). In the longer term, water year observations (since Oct 1) show above-average precipitation across most of New Mexico and eastern Colorado, with a mix of average and below-average precipitation across the rest of the Intermountain Southwest (Fig. 2).

Temperature: May and early June were exceptionally mild, but overall, June temperatures were consistent with warming southwestern summers, with much of New Mexico and nearly all of Arizona recording above-average temperature anomalies over the past 30 days (Fig. 3). An early start to monsoon activity has provided some relief, but increased humidity can offset lower temperatures by driving heat index values higher.

Monsoon: Last month, we reported on the general association between El Niño and a delayed onset to the monsoon. El Niño is showing no sign of letting up (see El Niño Tracker, pages 3-4), but our monsoon decided to ignore this association and got off to an early start anyway, about a week ahead of the average onset of monsoon storms in early July. The monsoon ridge set up and drove relatively frequent precipitation events over the past 30 days (see Monsoon Summary, page 5-6, for more details).

Drought & Water Supply: The U.S. Drought Monitor highlights drought conditions across the West, with particularly severe conditions in California and Nevada (Fig. 4). Arizona and western New Mexico continue to grapple with the impacts of years of accumulated drought and water deficit (see Reservoir Volumes, page 7). El Niño, particularly if it remains a moderate to strong event, offers some hope for above-average precipitation in the Southwest this winter.

Wildfire: Mild spring weather, above-average precipitation, and above-average relative humidity reduced wildfire risk in Arizona and New Mexico for much of the fire season (Fig. 5). An early start to the monsoon has continued to keep the most extreme fire risk conditions at bay, and a number of fires that started were allowed to burn for beneficial use, such as to manage fuel loads. As of July 7, wildland fires had burned approximately 100,000 acres in Arizona and approximately 40,000 acres in New Mexico.

Precipitation & Temperature Forecasts: The July 16 NOAA-Climate Prediction Center seasonal outlook predicts above-average precipitation for most of the Southwest and Intermountain West this summer, with Northern California and far western Nevada as notable exceptions (Fig. 6, top). Temperature forecasts are split, with elevated chances for above-average temperatures along the West Coast and into western Arizona (and most of the western U.S.), and increased chances for below-average temperatures in the midwestern U.S. and extending across New Mexico (Fig. 6, bottom).

Published by the Climate Assessment for the Southwest (CLIMAS), with support from University of Arizona Cooperative Extension, the Arizona State Climate Office, and the New Mexico State Climate office.

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