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June 2016 SW Climate Outlook - Climate Summary | CLIMAS


June 2016 SW Climate Outlook - Climate Summary

Thursday, June 16, 2016

Precipitation & Temperature: May precipitation totals in Arizona and New Mexico were average to above average (Fig. 1a), while temperatures were average to below average (Fig. 1b). May is one of the warmest and driest months in the Southwest, so these deviations provided a welcome break from more typical conditions. It takes very little moisture to push the month above average, and cooler-than-average temperatures still feel warm, albeit more desirable than the oppressive heat of mid-summer. June ushered even warmer-than-average temperatures, with most of Arizona and much of New Mexico recording temperatures 4-6 degrees F above normal (Fig. 2), with near-record and record temperatures observed during the first part of the month (June 3–5). Extreme heat is again in the forecast for June 18–19. In contrast to the building heat of summer, precipitation activity in May and early June is sporadic and unpredictable, and influenced by tropical storm activity, cold fronts that interface with surges of tropical moisture, and convective storms tied to the building monsoon. 

Drought, Snowpack, & Water Supply: A strong El Niño event was expected to bring above-average precipitation to the region, especially during winter and spring, but water year totals to date reveal a disappointing reality. Precipitation in most of Southern California and Arizona and much of western New Mexico was below average during this crucial timeframe (Fig. 3), and long-term drought persists across the Southwest (Fig. 4). Snowpack continues to dwindle in the upper elevations that feed into the Southwest, and the spring and summer streamflow forecasts for the Colorado and Rio Grande basins were between 50 and 109 percent of average. Lakes Mead and Powell in Arizona and Elephant Butte Reservoir in New Mexico are at 36, 50, and 14 percent of capacity, respectively (see reservoir storage diagrams). Lake Mead is receiving particular attention, given possible water restrictions if reservoir levels drop below established trigger points.

El Niño / La Niña Tracker: With a return to ENSO-neutral conditions, the El Niño event of 2015–2016 is officially over (see ENSO tracker). Current forecasts indicate a transition to La Niña conditions with some uncertainty as to the timing, with most forecasts indicating a return to La Niña by late summer or early fall. While strong El Niño events are linked to above-average precipitation during the cool season (this last event notwithstanding), La Niña events are associated with warmer and drier conditions over winter, which could have implications for drought, snowpack, and water supply concerns in the Southwest.

Wildfire: Relatively cooler and wetter-than-average conditions tamped down early-season fire activity, but wildland fire potential is above average for June and July, especially in southern and central Arizona (Fig. 5). Lightning activity tied to the building monsoon increases the risk of wildfire across the region, especially given the abundance of fine fuels stemming from above-average tropical storm activity last fall. There are numerous active wildfire events in Arizona and New Mexico (Fig. 5, inset), but to date, these events are either generally under control or are being managed to reduce fine fuels and the risk of severe wildfire.

Precipitation & Temperature Forecasts: The June 16 NOAA-Climate Prediction Center three-month seasonal outlook calls for equal chances of above- or below-average precipitation for the Southwest (Fig. 6, top) and increased chances of above-average temperatures across the entire western United States (Fig. 6, bottom).