Southwest Climate Outlook April 2016

Date issued

Precipitation & Temperature: Over the past 30 days, above-average temperatures and below-average precipitation continued across most of the Southwest. This pattern was in place for the last 90 days (Fig. 1), due in large part to a ridge of high pressure that diverted moisture away from the region and helped keep temperatures high and humidity low. March 2016 precipitation totals were much below average or even record dry, in most of Arizona and New Mexico (Fig. 2a), while temperatures were among the 10 warmest for the period in each state (Fig. 2b). These precipitation patterns are particularly unexpected, as a strong El Niño is associated with increased chance of above-average precipitation.

Drought, Snowpack and Water Supply: Long-term drought persists across the Southwest, and warm and dry weather has further exacerbated regional drought (Fig. 3). There was some hope that a strong El Niño might help ameliorate drought conditions. Instead, winter precipitation patterns look more like La Niña than El Niño, and water year precipitation, along with snowpack and reservoir storage, is unexpectedly average to below-average in much of the region. Early April storms provided a small boost to snowpack and water supply, but winter was dominated by above-average temperatures and below-average precipitation, which contributed to reduced snowpack across the region. Snow water equivalent (SWE) percent of normal values are well below average in Arizona and southern New Mexico (0 to 50 percent of normal) (Fig. 4), while northern New Mexico and much of the western United States are closer to normal (50 to 110 percent).

El Niño Tracker: This El Niño event is one of the strongest events ever recorded, but its strength is waning and seasonal outlooks forecast a transition to neutral conditions by summer and possibly to La Niña by fall. The strength of the event set high expectations, with hopes that a wet winter would mitigate some of the drought conditions in the Southwest. Six-month cool seasonal totals (Oct–Mar) are disappointingly average or slightly below average and were buoyed by a few strong events interspersed between mostly warmer- and drier-than-average conditions. Paradoxically, regional precipitation patterns more closely reflect those often seen in La Niña years, even though the atmospheric and oceanic conditions were clearly El Niño in origin (See El Niño Tracker and Recap).

Environmental Health and Safety: The wildflower season has been incredible this year, and also highlights the extent to which allergy sufferers are exposed to a diversity of pollen in the Southwest. Dust also remains a primary concern in terms of human health and public safety, especially as warm, dry, and windy conditions have increased the number and extent of dust events. Wildfire season is underway, and while the early April precipitation event may have tamped down fire risk temporarily, fine fuel growth from a wet fall combined with dry conditions this winter have contributed to above-normal wildland fire risk for May and into summer (Fig. 5).

Precipitation and Temperature Forecast: The March 17 NOAA-Climate Prediction Center three-month seasonal outlook calls for increased chances of above-average precipitation for most of the Southwest (Fig. 6, top) and increased chances of above-average temperatures across most of the western United States (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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