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Monthly Archive

Monsoon Recap - July 2019

Saturday, July 20, 2019

Given the spatial variability of the monsoon, single weather stations are an imperfect measure. For example, if it rains at the station and not in surrounding areas or vice versa. 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-July. 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 a relatively slow start, with most of the Southwest lagging behind average accumulated precipitation through mid-July (Fig. 4). There is still plenty of time however, since monsoon activity typically intensifies in July and August, and with many locations experience their monsoon midpoint* in August. An early start can boost cumulative totals, but a 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

 

Southwest Climate Outlook July 2019 - Climate Summary

Friday, July 19, 2019

June Precipitation and Temperature Recap: June precipitation was variable in Arizona, ranging from record driest to above average, with a majority of the region recording average to below average precipitation, while New Mexico was mostly average with pockets of both below and above average precipitation (Fig. 1a). June temperatures were mostly average in Arizona and New Mexico, with pockets of above and below average temperatures (Fig. 1b). Daily average temperature anomalies for Jun 1 – Jul 15 demonstrate the fluctuations above and below average (Fig. 2).

 

Seasonal Precipitation and Temperature Recap: Cumulative precipitation for April-June was mostly above average to much above average in Arizona, and below average to above average in most of New Mexico (Fig. 3a). Temperatures for the same period were average to below average in Arizona, and average to above average in New Mexico (Fig. 3b).

 

 

Drought: Water year precipitation to date was above average across much of the Southwest, with Arizona, Utah, Nevada, and southern California doing particularly well, while other areas (i.e. parts of Colorado and New Mexico) were closer to average and even below average (Fig. 4). This extended period of above average precipitation is reflected in the Jul 9 U.S. Drought Monitor (USDM), which continues to document widespread improvements in regional drought conditions in the western United States, and with most of the region no longer classified as experiencing drought (Fig. 5).

 

 

 

Water Supply: Most of the reservoirs in the region are at or above the levels recorded at this time last year, but most reservoirs are also below their long-term average (see Arizona and New Mexico reservoir storage). This highlights the short term improvement in drought conditions and reservoir storage, as well as the accumulated deficits linked to the persistent drought affecting the region for much of the last 20 years.

Wildfire, Health, and Safety: The onset of monsoon activity, including precipitation and increased humidity, has more or less tamped down elevated wildfire risk in much of the Southwest. The National Interagency Fire Center outlook for August calls for average fire risk across the region. In terms of wildfire acres burned, lightning caused fires in Arizona and New Mexico, as well as human caused fires in New Mexico, are all below their long term annual median acres burned for 2019 to date, while human caused fires in Arizona are well above the annual median acres burned (Fig. 6).

 

El Niño Tracker: After multiple months of outlooks that hinted at an El Niño event that might last through 2019 and into 2020, this event is currently forecast to return to ENSO-neutral conditions this summer (see ENSO-tracker for details).

Precipitation and Temperature Forecast: The three-month outlook for August through October calls for increased chances of below-normal precipitation in parts of western Arizona, 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, 3 - National Centers for Environmental Information - ncei.noaa.gov
  • Figure 2, 6 - Climate Assessment for the Southwest - climas.arizona.edu
  • Figure 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 - July 2019

Friday, July 19, 2019

Forecast Roundup: Seasonal outlooks and forecasts focused on sea surface temperature (SST) anomalies and other oceanic and atmospheric indicators, all of which had generally remained consistent with a weak El Niño event (Figs. 1-2), at least until recently. On July 9, the Australian Bureau of Meteorology ended their ENSO Outlook and returned to ‘inactive’ status, identifying ENSO-neutral as the most likely outcome in 2019. On July 10, the Japanese Meteorological Agency (JMA) identified the end of this El Niño event, mostly due to the rapid dissipation of SST anomalies, as well as the return to normal for other atmospheric indicators. They called for a 60-percent chance of ENSO-neutral conditions to continue into Fall 2019. On July 11, the NOAA Climate Prediction Center (CPC) maintained their El Niño advisory based on the SST anomalies, but trends in oceanic and atmospheric conditions led them to expect this event would transition to ENSO-neutral in the next few months. On July 11, the International Research Institute (IRI) issued an ENSO Quick Look (Fig. 3), highlighting above-average SSTs consistent with a weak El Niño, but with most models predicting a transition to ENSO-neutral status by the end of summer. The North American Multi-Model Ensemble (NMME) shifted considerably in the last month, and now points towards a rapid decline to ENSO-neutral status by early fall (Fig. 4).

Summary: El Niño conditions are still within the range of a weak event based on SST anomalies, but most forecasts and outlooks describe this event as over, or that it will be soon. This is a quick shift compared to forecasts from the last few months, which identified the persistence of El Niño through 2019 as the most likely scenario, based on SST anomalies and other oceanic and atmospheric indicators. The swing towards ENSO-neutral was tied to the rapid dissipation of warmer waters in the ocean, and a return to mostly normal atmospheric conditions. 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. Now that a return to ENSO-neutral is all but certain the role that El Niño might have played in enhancing pacific tropical storms is less relevant. This does not necessarily mean there is an increased chance of drier than normal conditions, but it does mean that one source of moisture and storm activity that has tended to bring increased chances of precipitation into the Southwest, especially in late summer and early fall, is effectively off the table.


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