The University of Arizona

Monthly Archive | CLIMAS

Monthly Archive

Southwest Climate Outlook September 2019 - Climate Summary

Friday, September 20, 2019

Monthly Precipitation and Temperature: August precipitation was much below average in most of Arizona, while most of New Mexico ranged from above average to much below average, and both states saw small pockets of record driest conditions (Fig. 1a). August temperatures were much above average to record warmest in Arizona and New Mexico (Fig. 1b). The daily average temperature anomalies for Aug 1 – Sep 17 highlight the fluctuations at select stations around the region (Fig. 2).

 

Seasonal Precipitation and Temperature: Total precipitation for the last three months (June-August) was below average to record driest in Arizona, with a wide range of above and below average totals in New Mexico (Fig. 3a). Mean temperatures for the same three-month period were above average to much above average across the region (Fig. 3b).

Drought: Water year precipitation to date includes wetter than normal winter conditions, and only pockets of Arizona, and much of western and southern New Mexico recorded below normal precipitation in the Southwest (Fig. 4). The recent downturn in precipitation activity is reflected in the Sept 10 U.S. Drought Monitor (USDM), which has seen a return of widespread drought designations in Arizona and western New Mexico (Fig. 5).

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). There have been improvements over the last year, but concerns remain about the recent below average precipitation, along with the accumulated water resource deficits associated with multiple years of drought.

Wildfire, Health, and Safety: The National Interagency Fire Center outlooks for September, October, and November all call for average fire risk across the region. With the declining monsoon activity and cooling temperatures, the Southwest should be on the wane for fire activity. Current seasonal statistics for wildfire acres burned show that lightning and human caused fires are above median in Arizona, and below median in New Mexico (Fig. 6).

ENSO Tracker: Oceanic and atmospheric conditions are generally consistent with an ENSO-neutral outlook for 2019 and into 2020 (see ENSO-tracker for details).

Precipitation and Temperature Forecast: The three-month outlook for October through December calls for increased chances of above-normal precipitation in much of New Mexico, eastern Arizona, and north Texas, while equal chances of above- or below-normal precipitation are prominent in western Arizona, west Texas, and most of northern Mexico (Fig. 7, top). The three-month temperature outlook calls for increased chances of above-normal temperatures across 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

Southwest Climate Outlook - El Niño Tracker - September 2019

Friday, September 20, 2019

Forecast Roundup: Seasonal outlooks and forecasts based on sea surface temperature (SST) anomalies (Figs. 1-2) and other oceanic and atmospheric indicators all point towards ENSO-neutral conditions lasting through 2019 and into 2020. On Sep 10, the Japanese Meteorological Agency (JMA) highlighted dissipating warmer-than-normal SSTs and maintained their call for a 60-percent chance of ENSO-neutral conditions to continue until winter 2019-2020. On Sep 12, the NOAA Climate Prediction Center (CPC) issued their ENSO diagnostic discussion, which focused on neutral conditions across the oceans and atmosphere. They called for a 75-percent chance of ENSO-neutral conditions persisting through fall 2019. On Sep 12, the International Research Institute (IRI) issued an ENSO Quick Look (Fig. 3), emphasizing neutral conditions in both oceanic and atmospheric ENSO indicators. Their models see ENSO-neutral as the most likely outcome, but with “slightly higher chances for El Niño than La Niña”. On Sep 17, the Australian Bureau of Meteorology maintained their ENSO Outlook at ‘inactive’ with most oceanic and atmospheric conditions in the range of neutral. The North American Multi-Model Ensemble (NMME) is within the range of ENSO-neutral and is forecast to remain neutral through 2019, with more variability and uncertainty into 2020 (Fig. 4).

 

Summary & Outlook: ENSO-neutral remains the most likely outcome for 2019 extending into winter 2020. Oceanic and atmospheric conditions returned to within the range of ENSO-neutral, and the ENSO outlooks generally reflect these conditions. In terms of the Southwest, seasonal outlooks had been calling for above average precipitation in late summer and early fall, presumably linked 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 no longer in play, but warmer and (mostly) wetter than normal conditions remain in the seasonal outlooks thus far (see Fig. 7 on p. 2). Despite El Niño’s decline to ENSO-neutral, tropical storm activity has picked up in the eastern Pacific Ocean. At the time of this writing, two named storms (TS Lorena and TS Mario), depending on their eventual storm track, are poised to help direct moisture into the Southwest. This could amplify precipitation activity even as the monsoon is on the wane and might even help make up some of the accumulated precipitation deficit of a mostly below average monsoon.

 


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

Monsoon Recap - September 2019

Monday, September 16, 2019

Single weather stations are an imperfect measure of monsoon spatial variability, 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 that continued into September. Daily average and dewpoint temperatures, along with daily and cumulative precipitation 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 (Fig. 2).

Total monsoon precipitation (Fig. 3) is variable in the Southwest, with much of the region lagging behind average through mid-September (Fig. 4). Percent of days with rain highlight areas with more (or less) regular rainfall events (Fig. 5). 2019 is shaping up to be one of the drier monsoons for much of the region, and some locations may be in the running for driest monsoon on record. A late September tropical storm could boost precipitation totals, but time is quickly running out.


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