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Monthly Archive

June 2016 SW Climate Outlook - ENSO Tracker

Friday, June 17, 2016

El Niño conditions continued their active decline (Figs. 1-2), and consensus is that they have reached ENSO-neutral status at the time of this writing. Forecast discussions focused on the decline of atmospheric and oceanic anomalies that characterize an El Niño event—convective activity, equatorial sea surface temperatures, and trade winds—and forecasters saw consistent evidence of a return to ENSO-neutral status across these indicators. Seasonal ENSO outlooks coalesced around La Niña conditions emerging by summer or fall 2016, with relatively high certainty that La Niña conditions would be in place sometime by mid-to-late 2016.

On June 7, the Australian Bureau of Meteorology maintained its outlook at La Niña Watch status, noting that the tropical Pacific Ocean was in an ENSO-neutral state, with a 50 percent probability of a La Niña event developing in 2016. On June 9, the NOAA-Climate Prediction Center (CPC) issued a final El Niño Advisory, while maintaining a La Niña Watch. The CPC identified atmospheric and oceanic anomalies as reflecting ENSO-neutral conditions and forecast La Niña conditions would develop over the summer, with a 75 percent probability of a La Niña during fall and winter 2016-2017. On June 10, the Japan Meteorological Agency identified that El Niño conditions ended in late spring 2016, with an increasing likelihood of La Niña developing over summer and into fall. On June 16, the International Research Institute for Climate and Society (IRI) and CPC forecasts identified ENSO-neutral conditions in oceanic and atmospheric indicators, with La Niña emerging by late July or August and lasting through fall and winter (Fig. 3). The North American multi-model ensemble currently shows the decline from strong El Niño status to neutral conditions, as well as a relatively rapid swing to La Niña conditions by summer (Fig. 4).

As very clearly experienced during the El Niño event of 2015–2016, there is no guarantee that a given event will meet expectations (see El Niño tracker in the May 2016 Southwest Climate Outlook for more details). That said, it is important to note that La Niña events are associated with decreased cool-season precipitation in the Southwest. This is a more reliable pattern in terms of forecasts and predictions, with La Niña events being more reliably dry than El Niño events are reliably wet, and considerable variability between wet and dry in ENSO-neutral years. With a La Niña forecast on the horizon for winter 2016–2017, drier-than-average cool-season precipitation totals are a likely outcome, with implications for long-term drought and water storage concerns in the Southwest.

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).