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Southwest Climate Outlook May 2019 - Climate Summary

Sunday, May 26, 2019

April Precipitation and Temperature: April precipitation was average to much above-average in most of New Mexico, while Arizona ranged from below-average to above-average (Fig. 1a). April temperatures were almost entirely above-average to much above-average across the Southwest (Fig. 1b), while temperatures so far in May have been mostly below-average.

Seasonal Precipitation and Temperature: Year-to-date precipitation (Jan-Apr) is above-average for most of the western U.S. (Fig. 2a). Most of Arizona and northern New Mexico were above-average or much above-average, and across the Southwest, only southern New Mexico and far west Texas recorded below-average precipitation. Temperatures for Jan-Apr were average to above-average in Arizona and mostly above-average in New Mexico (Fig. 2b).

Drought: Water year precipitation is above normal (top 33%) for much of the Southwest, with large areas of much above normal (top 10%) and smaller pockets of record wet conditions (Fig. 3). The May. 7 U.S. Drought Monitor (USDM) continues to show improvements in regional drought conditions in the Southwest, with Arizona nearly clear of drought designations, and the intensity of drought characterizations in the four corners region and northern New Mexico further reduced compared to last month (Fig. 4).


Snowpack & Water Supply: Late season snowpack in the Southwest is waning, and snow water equivalent (SWE) in Arizona and New Mexico reflect this seasonal transition. Many stations are no longer reporting values, but those still reporting show over 200-percent of average (Fig. 5). Upper elevation areas in Utah and Colorado mostly range from 110- to 200-percent of average, which bodes well for short term reservoir storage (see streamflow forecast and Arizona and New Mexico reservoir diagrams).

Wildfire, Health, and Safety: Wildfire outlooks for June and July paint a similar picture for lower elevation areas of Arizona, with above normal fire risk (Fig. 6), linked to widespread fine fuel growth driven by above-average precipitation in the cool season. Northern Arizona and New Mexico are projected to see below normal fire risk in June and return to normal risk in July. Cool season precipitation has done wonders for the wildflower season and helped with drought, but wildfire risk and the impact of pollen production for allergy sufferers provide examples of trade-offs associated with increased precipitation.

El Niño Tracker: Atmospheric and oceanic conditions remain in line with a weak El Niño, and most forecasts call for this event to last at least through summer. There is considerable uncertainty, however, for forecasts made in Spring, and in the Southwest, there is little in the way of a precipitation signal to alter in May and early June (see El Niño tracker for more details).


Precipitation and Temperature Forecast: The three-month outlook for June through August calls for increased chances of below-normal precipitation in northern and central Arizona and equal chances of above- or below-normal precipitation in much of the rest of Arizona, New Mexico, west Texas, and northern Mexico (Fig. 7, top). The three-month temperature outlook calls for increased chances of above-normal temperatures in most of Arizona, and parts of northern New Mexico, and northern Mexico, with equal chances of above- or below-average temperatures in the rest of the region (Fig. 7, bottom).

Online Resources

  • Figures 1-2 - National Centers for Environmental Information -
  • Figure 3, 5 - Western Regional Climate Center -
  • Figure 4 - U.S. Drought Monitor -
  • Figure 6 - National Interagency Fire Center -
  • Figure 7 - International Research Institute for Climate and Society -

Southwest Climate Outlook - El Niño Tracker - May 2019

Sunday, May 26, 2019

Seasonal outlooks highlight persistent sea surface temperature (SST) anomalies consistent with a weak El Niño event (Figs. 1-2), while other atmospheric and oceanic indicators such as convective anomalies and sub-surface temperatures are less definitive. The so-called ‘spring predictability barrier’ further limits certainty. Forecast discussions focus on how long the event will last and the potential for a second year of El Niño.

On May 9, the NOAA Climate Prediction Center (CPC) maintained their El Niño advisory, identifying that SSTs were consistent with El Niño even while other indicators were less definitive. Their outlook maintained a 70-percent chance of El Niño lasting through summer, and 55- to 60-percent of lasting through fall. On May 9, the International Research Institute (IRI) issued an ENSO Quick Look (Fig. 3), highlighting above-average SSTs and warm subsurface waters, although they noted a decline in the positive sub-surface anomalies over the last few months. On May 10, the Japanese Meteorological Agency (JMA) noted deviations from typical El Niño conditions in the atmosphere, but based on SSTs, they called for an 80-percent chance of the event lasting until summer, and a 60-percent chance to last until fall. On May 14, the Australian Bureau of Meteorology moved their ENSO Outlook to “watch” status (down from “alert”), calling for a 50-percent chance of an El Niño event sometime in 2019. The North American Multi-Model Ensemble (NMME) points toward a weak El Niño lasting into fall 2019 (Fig. 4).


Summary: El Niño conditions are in the range of a weak event, but it is difficult to nail down its longevity. It might be on the way out by the end of summer, it might extend into Fall, or it might even last into 2020. With El Niño conditions expected to remain for at least the rest of summer, there are a few associations of note. The first is enhanced northern Pacific tropical storm activity, which could see tropical storms increase our warm season precipitation totals in direct ways via storms that push into the region or that provide additional moisture and instability that enhances monsoon activity. This influence is typically associated with the latter half of the monsoon and into fall, but tropical storms have augmented regional precipitation totals in late May and early June (e.g. TS Bud, last year). El Niño conditions over summer are also associated with a delayed onset of monsoon activity, but this link is tenuous given the small sample size. El Niño sends us mixed signals for summer seasonal outlooks, and provides little to improve our understanding about the timing and intensity of tropical storm activity and monsoon precipitation.

Online Resources

  • Figure 1 - Australian Bureau of Meteorology -
  • Figure 2 - NOAA - Climate Prediction Center -
  • Figure 3 - International Research Institute for Climate and Society -
  • Figure 4 - NOAA - Climate Prediction Center -