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Monthly Archive

El Niño Tracker - June 2015

Friday, June 19, 2015

Originally Published in the June 2015 CLIMAS SW Climate Outlook (SWCO)

El Niño conditions continued for a fourth straight month with no signs of weakening or disorganizing. Forecasts focused on the persistence of sea-surface temperature (SST) anomalies (Figs.1 - 2) along with weakening trade winds, ongoing convective activity, and El Niño-related ocean-atmosphere coupling. Despite the high degree of uncertainty associated with forecasting El Niño this time of year (the so-called spring predictability barrier), the most recent outlooks from various sources offer a consistent cluster of forecasts calling for a clear El Niño signal that is maintained or even strengthening. 

Image Source - Australian Bureau of Meteorology

Image Source - National Climatic Data Center

On June 9, the Australian Bureau of Meteorology maintained its tracker at official “El Niño” status, identifying persistent SST anomalies, weak trade winds, and ocean-atmospheric coupling as indicators this El Niño event was strong enough to extend through 2015. On June 10, the Japan Meteorological Agency identified strengthening El Niño conditions in the equatorial Pacific, and forecast that the current El Niño conditions were likely to last until winter. On June 11, the NOAA-Climate Prediction Center (CPC) extended its El Niño advisory with a 90 percent chance that El Niño will continue through fall 2015 and an 85 percent chance the event would last through winter 2015-2016.  It pointed to the increasingly positive SST anomalies, along with ongoing ocean-atmospheric coupling and dateline convection activity, as indicators of an ongoing and strengthening El Niño event (Fig. 3). On June 18, the International Research Institute for Climate and Society (IRI) and CPC forecasts indicated continued strengthening of El Niño through 2015, with a moderate event during summer and likely stronger in the fall, lasting into early 2016. The North American multi-model ensemble currently shows a moderate event extending through early summer, with potential for a strong event by mid-summer or early fall (Fig. 4).

Image Source - International Research Institute for Climate and Society

Image Source - NOAA - Climate Prediction Center

Last year’s vacillating signals and forecasts may have led forecasters to take a more conservative approach when presented with similar conditions earlier this year to avoid repeating the “enthusiastic” forecasts of Spring 2014 that didn’t immediately pan out.  That said, we appear to be in the midst of an ongoing and strengthening El Niño event.  If this event remains on the current trajectory, it could rival our strongest El Niño events of recent memory (1997 in particular), with implications for both Southwest and global communities.

The recent above-average precipitation and below-average temperatures in Arizona and New Mexico are exactly the sort of patterns we expect to see under El Niño conditions. In the immediate future, we may see a return of some early season tropical storm activity, as we did with Hurricane Blanca in June. El Niño also points toward a possible delay in the start of the monsoon, which could actually extend the hotter and drier early portion of summer. We could also see a repeat of 2014’s above-average eastern Pacific tropical storm season, when conditions favorable to El Niño were thought to be driving increased late-season tropical storm activity in the Southwest.  And if El Niño persists into winter 2015-2016, particularly if it remains a moderate-to-strong event, we would likely see patterns of above-average precipitation in the Southwest (Fig. 5).

Image Source - NOAA

El Niño Models - May 2015 SW Climate Podcast

Friday, June 19, 2015

Excerpt from the May 2015 CLIMAS SW Climate Podcast

Image & Story Credits

Southwest Climate Outlook June 2015

Thursday, June 18, 2015

Originally Published in the June 2015 CLIMAS SW Climate Outlook (SWCO)

Precipitation: In the past 30 days, most of New Mexico and much of northern Arizona recorded well-above-average precipitation (Fig. 1).  Climatologically, we are in one of the drier times of year for the Southwest, so this precipitation and humidity (mostly tied to early season Pacific tropical storm activity) helped tamp down fire risk. This respite was short-term however, as water-year observations since October 1 reflect persistent and ongoing drought conditions, with most of the western U.S. recording well-below-average precipitation (Fig. 2).  Notable exceptions are New Mexico, Colorado, Wyoming, and Montana, but with most recent precipitation falling on the eastern side of the Continental Divide.

Image Source - NOAA/NWS - Advance Hydrologic Prediction Service

Image Source - NOAA/NWS - Advance Hydrologic Prediction Service

Temperature: Tropical storm activity led to unseasonably mild and pleasant conditions across the Southwest, with temperature anomalies across much of Arizona and New Mexico between 2 and 6 degrees below average during the past 30 days (Fig. 3).  But by mid-June, the Southwest had returned to more typical hotter and drier temperature and humidity patterns.  These conditions are likely to persist until the monsoon fires up, which may be delayed by El Niño conditions.  

Image Source - High Plains Regional Climate Center

Snowpack/Streamflow: At this point in the season (and after a relatively warm winter), snow is absent across much of the West. The recent unseasonably cool and wet conditions led to some anomalous snow water equivalent (SWE) readings in Colorado and Utah (Fig. 4), but it remains to be seen if this will have any long-term effects on water supply or streamflow.  Streamflow forecasts reflect generally warm and dry winter conditions, with below-average forecasts across most of the western U.S. (Fig. 5), save for a few locations that saw late-season spikes in storm activity.

Image Source - Natural Resources Conservation Service 

Drought & Water Supply: The U.S. Drought Monitor highlights drought conditions across the West, with particularly severe conditions in California and Nevada. Arizona and New Mexico are still grappling with the impacts of years of accumulated drought, and the monitor emphasizes long-term drought conditions across Arizona and western New Mexico.

Wildfire: Mild spring weather, above-average precipitation and above-average relative humidity have reduced wildfire risk in Arizona and New Mexico for most of this wildfire season thus far, but recent elevated temperatures and decreased humidity could change conditions quickly.  The current short-term forecast calls for increasingly hotter, drier, and breezy conditions, especially in southern Arizona (Fig. 6).  This could increase fire risk across the region, especially given the abundance of fine fuels stemming from above-average tropical storm activity late last fall. In the past week or so, we have already seen a number of lightning ignitions, although to date, fire managers are allowing these to burn to reduce fuel loads, further highlighting the beneficial impact of the extended period of cool and wet late-spring weather.

Image Source - National Interagency Coordination Center

Precipitation & Temperature Forecasts: The June 18 NOAA-Climate Prediction Center seasonal outlook predicts above-average precipitation for much of the Southwest and most of the Intermountain West this summer, with California, western Nevada, and southwest Arizona as notable exceptions. Temperature forecasts are split, with elevated chances for above-average temperatures along the West Coast and into Arizona (and most of the western U.S.), and increased chances for below-average temperatures in the midwestern U.S. and extending into eastern New Mexico (Fig. 7)

Image Source - NOAA/NWS - Climate Prediction Center