The University of Arizona

Monthly Archive | CLIMAS

Monthly Archive

CLIMAS SW Climate Outlook - Wildfire Report: Sawmill Fire

Friday, May 19, 2017

The Sawmill fire (Fig. 1) started, reportedly by recreational shooting, on April 23, 2017 in a grass- and shrub-covered area of low-elevation Arizona state lands approximately 40 miles south of Tucson. The fire spread quickly due to dry and windy conditions that day: the temperature reached 98 degrees, relative humidity ranged between 4 and 18 percent, and sustained winds reached 20 mph with gusts up to 30 mph. High winds, high temperatures, and low relative humidity continued through much of the following week, driving rapid growth of the fire (Fig. 2).

The strong winds whipped the fire along, challenging ground-level fire-line containment efforts and repeatedly grounding aerial support. Numerous communities and rural households were evacuated, and wildfire management was eventually escalated to a type 1 incident management team. At peak effort, nearly 800 firefighters and multiple aerial tankers were deployed to fight the fire, slow the spread, and protect communities and structures. Initial estimates of the fire put the total acreage burned at 46,991 acres, making it the 14th largest wildfire in Arizona history (Fig. 3).

In the Southwest, peak seasonal wildfire danger varies across the region, ranging from early-mid-May to early June in eastern New Mexico, to late June in western Arizona (Fig. 4). This roughly corresponds to the progression of the monsoon, which brings some relief to the hot and dry conditions that characterize late spring and early-to-mid summer, although dry lightning associated with early monsoon storms sometimes serves as an ignition source for wildfire. June and early July are characterized by the warmest and driest conditions, reaching the peak of the warm-up and dry-out period of late spring into summer.

While fire is possible during most of the year, most wildfire activity clusters in this warm/dry summer period (Fig. 5). The Sawmill fire demonstrates that large fires are possible outside of the peak of summer wildfire season, and was likely the culmination of a set of circumstances that brought about enhanced wildfire risk earlier than is typical in Arizona.

In September 2016, a surge in precipitation associated with hurricane Newton and lingering monsoon activity brought moisture into the Southwest, in particular to the southeastern corner of Arizona where the Sawmill fire broke out (Fig. 6). The rains boosted plant growth and green-up, and by mid-October, above-normal green-up was visible in satellite imagery of the grasslands in the region (Fig. 7). 

Following this explosion of new vegetation, the region experienced an extended drier-than-average period, with water-year precipitation totals for the seven-month period of Oct 2016 to April 2017 well-below average in southern Arizona. (Fig. 8).

Temperatures during the same period were warmer than average across the Southwest, and in some locations approached or set records (Fig. 9). The relative wintertime warmth augmented by early January precipitation further enhanced plant growth. These moderate winter conditions extended the growing season and likely contributed to an early start for spring plant growth and development (for more details see the story about early arrival of spring conditions in 2017, links to a changing climate, and the National Phenology Network).

By late winter, however, heat and lack of precipitation (Fig. 10) had dried out the lower-elevation soils and the new vegetation began to dry out and die. By early-to-mid April, abundant fine fuels had accumulated. Add in strong winds and low relative humidity, and the stage was set for an earlier-than-normal significant wildfire event – all it needed was an ignition source. Although that source was a human, the fire itself, by virtue of its fast-moving nature, did not have severe adverse impacts to the soil and may ultimately be viewed as beneficial to the grasslands.


Image Credits

Southwest Climate Outlook May 2017 - Climate Summary

Thursday, May 18, 2017

Precipitation & Temperature: April precipitation was average to above average in New Mexico, while most of Arizona was below average, including much-below average and record-dry conditions in the southwestern corner of the state (Fig. 1a). April temperatures were above average in nearly all of Arizona and New Mexico, with much-above average temperatures in southern Arizona (Fig. 1b). May has been dry in southern Arizona and New Mexico, while parts of northern Arizona and northern and eastern New Mexico have picked up decent precipitation relative to the normally dry May climate (Fig. 2). May temperatures in Arizona and New Mexico have ranged from 4 degrees below to 4 degrees above normal, while temperatures in higher latitudes and upper elevations (e.g. Upper Colorado River Basin, California Sierras, etc.) have been generally warmer than average, ranging from 0 to 8 degrees above normal. Water year precipitation has been normal to above normal across most of Arizona and New Mexico aside from a small pocket of dry conditions along the Arizona-Mexico border (Fig. 3).

Snowpack & Water Supply: Snowpack and snow water equivalent (SWE) have declined in Arizona and New Mexico as well as in the Upper Colorado River Basin region of Utah and Colorado (Fig. 4). While areas of well-above-average snowpack and SWE remain, particularly in the Great Basin and the California Sierras, persistent warm temperatures are reducing once-impressive snowpack levels back to normal. This has resulted in some remarkable streamflow forecasts, as well as incremental improvements in reservoir storage volumes (see reservoir levels).

Drought: Much of the West has seen improvements in drought conditions, and only 5.2 percent of the contiguous United States is now designated as experiencing moderate drought (D1) or worse. The wetter-than-normal conditions that helped reduce drought conditions across much of the West (see Fig. 3) provided limited relief (if any) in southern Arizona and New Mexico, which have experienced a return of both short- and long-term drought designations (Fig. 5). These changes are due to both near-record- to record-warm temperatures in recent months and very little precipitation falling since mid-January.

Wildfire, Environmental Health, & Safety: The transition from spring into summer brings rising temperatures, little precipitation, and frequent high winds that create highly favorable conditions for fire ignition and spread. As noted last month, fire managers are increasingly vigilant during this transitional season. This year, fire conditions have been enhanced by the senescence of grasses that thrived under the moisture of last fall and warm temperatures this winter into spring, and have now left behind a pervasive blanket of fine fuels that exacerbate wildfire risks, especially during hot, dry, windy days. The Sawmill fire of 2017 perfectly encapsulates this cluster of conditions (see wildfire report). The warm and dry weather also produces dry and dusty conditions that prompt ongoing health and safety concerns such as dust exposure and traffic visibility.

El Niño Southern Oscillation: Current forecasts suggest ENSO-neutral conditions will continue through the spring and early summer, with approximately equal chances of an El Niño event or ENSO-neutral conditions during the second half of 2017.

Precipitation & Temperature Forecast: The May 18 NOAA Climate Prediction Center’s outlook for June calls for equal chances of above- or below-average precipitation for most of the Southwest, and increased chances of above-average temperatures across the region. The three-month outlook for June through August calls for equal chances of above- or below-average precipitation in Arizona and much of New Mexico with only the northeast corner of New Mexico expecting increased chances of above-average precipitation (Fig. 6, top). Increased chances of above-average temperatures are forecast for the entire southwestern region (Fig. 6, bottom).

CLIMAS SW Climate Outlook - ENSO Tracker May 2017

Thursday, May 18, 2017

Oceanic and atmospheric indicators are still within the range of neutral (Figs. 1-2), although sea-surface temperatures have more consistently hinted at El Niño compared to atmospheric indicators. Outlooks and forecasts generally agree that ENSO-neutral conditions are likely to remain through the summer, but by mid-to-late 2017, chances of an El Niño event emerging become approximately equal to the chances of continued ENSO-neutral conditions. On May 9, the Australian Bureau of Meteorology maintained its El Niño Watch with a 50-percent chance of an El Niño event, noting warming sea-surface temperatures but less movement towards El Niño in the atmosphere. On May 11, the NOAA Climate Prediction Center (CPC) observed that oceanic and atmospheric conditions were consistent with ENSO-neutral conditions, but expressed some doubt as to whether warming ocean temperatures would last long enough to reach official El Niño status, and whether coupling between ocean and atmosphere would be sufficient to drive an El Niño event. CPC identified nearly equal chances of El Niño (45%) and ENSO-neutral (50%) conditions during fall 2017, with uncertainty regarding El Niño potential attributed to “the lack of a clear shift toward El Niño in the observational data.”  On May 12, the Japanese Meteorological Agency (JMA) identified a continuation of ENSO-neutral conditions with a 50-percent chance of El Niño conditions by fall 2017, but like others noted a lack of development in atmospheric conditions that matched the warming sea-surface temperatures. On May 18, the International Research Institute for Climate and Society (IRI) and CPC identified a 60-percent chance of an El Niño in 2017 (Fig. 3) with “dynamical models showing weak El Niño, while statistical (models) predict (an) even weaker event”. The North American Multi-Model Ensemble (NMME) is borderline weak El Niño as of May 2017, but the model spread indicates a wide range of possible outcomes for the rest of 2017 (Fig. 4), clustered mostly around ENSO-neutral and weak El Niño conditions, paralleling the uncertainty in the CPC and IRI/CPC outlooks.

 

 

Summary: The lack of clear atmospheric indicators of El Niño, the borderline status of sea-surface temperature anomalies, and the waning influence of remnant La Niña conditions together indicate there is not an imminent El Niño event, although it is too early to rule out an event later this year. Outlooks and forecasts this time of year come with the annual caveat regarding increased uncertainty during the “spring predictability barrier,” and better predictions will become available over the summer. While this uncertainty makes forecasting difficult, one likelihood that does appear certain is a near-zero probability of a La Niña event in 2017. Other than that exclusionary forecast, it is essentially a coin-flip between El Niño and ENSO-neutral, and the Southwest remains in an El Niño holding pattern until more information is available, and/or conditions become less ambiguous.

Climate Services Database Now Available for the Western States

Tuesday, May 9, 2017

More than 130 public sector and nonprofit organizations provide climate services to the eleven western states, yet until now there has been no centralized resource to connect climate information users with the wide array of information and services available.

The NOAA Western Region Climate Service Providers Database is a searchable directory of climate service providers in the west that makes climate services easier to find. Its powerful search function allows users to customize their search based on the type of service, the geographic area, stakeholders served, and several additional parameters. It’s a match-making app for the climate world.

For example, say a water resource manager in Nevada is seeking coordination assistance in water resource issues. By searching for the state and sector served (NV and water, respectively), and for an organization that provides coordination services, the database returns eight organizations for the manager to contact for more information.

This database is a pilot and we appreciate comments and suggestions from users. Please send any comments to csproviders@dri.edu. For more information about this project and initial findings from a landscape assessment of climate providers in the west, please refer to the preliminary analysis report.

This resource was created through a partnership between NOAA Western Regional Collaboration Team, the NOAA-RISA Western Water Assessment and the NOAA-RISA Climate Assessment for the Southwest.