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Monthly Archive

Southwest Climate Outlook - El Niño Tracker - August 2019

Friday, August 23, 2019

El Niño Tracker

Forecast Roundup: Seasonal outlooks and forecasts based on sea surface temperature (SST) anomalies (Figs. 1-2) and other oceanic and atmospheric indicators have all identified the end of this El Niño event. On Aug 6, the Australian Bureau of Meteorology maintained their ENSO Outlook at ‘inactive’, stating that “all climate models indicate the tropical Pacific is likely to remain ENSO-neutral for the rest of 2019”. On Aug 8, the NOAA Climate Prediction Center (CPC) issued their final El Niño advisory, which reflects the end of oceanic and atmospheric conditions indicative of El Niño. They called for a 50-55% chance of ENSO-neutral conditions persisting through winter 2019-2020. On Aug 8, the International Research Institute (IRI) issued an ENSO Quick Look (Fig. 3), confirming the end of El Niño as SSTs returned to normal in July. Their models see ENSO-neutral as the most likely outcome, but with “higher chances for El Niño than La Niña”. On Aug 9, the Japanese Meteorological Agency (JMA) highlighted a return to normal SSTs and other atmospheric indicators and maintained their call for a 60-percent chance of ENSO-neutral conditions to continue until winter 2019. The North American Multi-Model Ensemble (NMME) is within the range of ENSO-neutral and is forecast to remain there through 2019 and into 2020 (Fig. 4).

 

Summary: As predicted in more recent model runs, oceanic and atmospheric conditions have returned to within the range of normal, and this El Niño event is officially over. This is in spite of earlier outlooks that were rather bullish on El Niño lasting into fall and winter of this year, and it will be interesting to track how forecasters make sense of this relatively quick swing in forecasts in the next month or so. In terms of the Southwest, seasonal outlooks had been calling for above average precipitation in late summer and early fall, likely tied to the increased chance of enhanced tropical storm activity in the eastern pacific associated with El Niño. With a return to ENSO-neutral, the role that El Niño might play in enhancing those pacific tropical storms is much less relevant, and this has been a quiet tropical storm season so far (at least in terms of southwestern impacts). This does not mean there is an increased chance of drier than normal conditions, but it does mean that the enhanced tropical storm activity associated with El Niño is no longer in play.


Online Resources

  • Figure 1 - Australian Bureau of Meteorology - bom.gov.au/climate/enso
  • Figure 2 - NOAA - Climate Prediction Center - cpc.ncep.noaa.gov
  • Figure 3 - International Research Institute for Climate and Society - iri.columbia.edu
  • Figure 4 - NOAA - Climate Prediction Center - cpc.ncep.noaa.gov

Southwest Climate Outlook August 2019 - Climate Summary

Friday, August 23, 2019

Monthly Precipitation and Temperature: July precipitation was mostly below average to much below average in Arizona, while New Mexico ranged from above average to much below average (Fig. 1a). July temperatures were mostly above average to much above average in Arizona and New Mexico, with a small pocket of record warmest in southwestern New Mexico (Fig. 1b). The daily average temperature anomalies for Jul 1 – Aug 15 (Fig. 2) highlight the fluctuations at select stations around the region.

Seasonal Precipitation and Temperature: Total precipitation for the last three months (May-July) was below normal or much below normal for most of Arizona and New Mexico (Fig. 3), and limited early season tropical storms and a late monsoon onset are part of this story. Water year precipitation to date reveals the extent to which much of the Southwest has recorded above average precipitation over the last year, with parts of New Mexico and Colorado as the only areas without normal to above normal precipitation (Fig. 4).

Drought: Despite the recent below average precipitation, the impact of longer-term above average precipitation in much of the Southwest is reflected in the Aug 6 U.S. Drought Monitor (USDM), which continues to document relatively low levels of drought designation in Arizona and New Mexico (Fig. 5). The past three months of mostly below average precipitation, and the late onset of the monsoon, however, will lead drought experts to closely monitor these conditions.

Water Supply: Most of the reservoirs in the region are at or above the values recorded at this time last year, but most also remain below their long-term average (see Arizona and New Mexico reservoir storage). This illustrates improvements in drought conditions over the past year, but also highlights accumulated water resource deficits linked to multiple years of drought.

Wildfire, Health, and Safety: Despite a late and somewhat sporadic onset of monsoon activity, the resulting precipitation and increased humidity has helped tamp down elevated wildfire risk in much of the Southwest. The National Interagency Fire Center outlooks for August and September each call for average fire risk across the region. In terms of wildfire acres burned, lightning and human caused fires are above median in Arizona, and below median in New Mexico (Fig. 6).

El Niño Tracker: Despite hints (or hope) that this El Niño event might last into early 2020, conditions have returned to ENSO-neutral and are likely to remain neutral through the rest of 2019 and into 2020 (see ENSO-tracker for details).

Precipitation and Temperature Forecast: The three-month outlook for September through November calls for increased chances of above-normal precipitation in parts of New Mexico, with equal chances of above- or below-normal precipitation in 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 across most of the U.S. Southwest and northern Mexico (Fig. 7, bottom).


Online Resources

  • Figures 1 - National Centers for Environmental Information - ncei.noaa.gov
  • Figure 2, 6 - Climate Assessment for the Southwest - climas.arizona.edu
  • Figure 3, 4 - Western Regional Climate Center - wrcc.dri.edu
  • Figure 5 - U.S. Drought Monitor - droughtmonitor.unl.edu
  • Figure 7 - International Research Institute for Climate and Society - iri.columbia.edu

Monsoon Recap - August 2019

Tuesday, August 20, 2019

Given the spatial variability of the monsoon, single weather stations are an imperfect measure, but they do provide an opportunity to track long term averages compared to the current year. Figure 1 compares 2019 precipitation to date with 2018 and climatology. This reveals 2019 is lagging behind average in terms of precipitation and is also a significant departure from 2018’s widespread activity by mid-August. Dewpoint temperatures and daily precipitation for the same five stations (Fig. 2) illustrate that while increased dewpoint temperatures do not guarantee monsoon precipitation, it is rare to see monsoon precipitation in the absence of these elevated dewpoint temperatures. Regional monsoon precipitation totals (Fig. 3) demonstrate variable precipitation in the Southwest, with much of the region lagging behind average accumulated precipitation through mid-July (Fig. 4). Percent of days with rain highlight areas with more regular rainfall events (Fig. 5). Mid-August is the approximate monsoon midpoint*, so there is time for below average areas to catch up, since a relatively late start does not necessarily mean decreased activity over the entire monsoon.


Online Resources

  • Figures 1-2 - Climate Assessment for the Southwest - climas.arizona.edu
  • Figures 3-5 - Climate Science Applications Program - cals.arizona.edu/climate/misc/SWMonsoonMaps/current/swus_monsoon.html