Western Regional Climate Center

PROVIDING CLIMATE SERVICES SINCE 1986

September in the West

September 2014

Scattered areas of the West saw significantly above normal precipitation this month, notably the Great Basin and areas along the Mexican border. Though several low-pressure systems moved through the West during September, strong high pressure between storms kept temperatures above normal for much of the region.

Remnants of hurricanes Norbert and Odile supplied moisture that allowed for heavy precipitation over the Southwest this month. Phoenix, Arizona recorded its wettest calendar day on record September 8th when 3.3 in (84 mm) fell in roughly 7 hours. Phoenix also recorded its wettest September on record with a total 5.11 in (130 mm) precipitation. Records for Phoenix began in 1933. Artesia, in southeastern New Mexico, recorded 7.37 in (187 mm) this month. This was the 5th wettest September in a 110-year record. Average September precipitation for Artesia is 1.79 in (46 mm). A cold-core low-pressure system during the last week of the month also provided precipitation for a wide swath of the West. In Northern California, Eureka logged 3.09 in (78 mm) of rainfall, 500% of normal and the 6th wettest September since records began in 1887. Of this total, a majority (2.59 in/66 mm) occurred on the 24th. Southeast Utah also experienced above normal precipitation this month. Cedar City reported 2.57 in (65 mm), the 3rd wettest September since records began in 1948. Above normal precipitation was also observed in southern Idaho and along the borders between Idaho and Oregon/Nevada and Utah. This precipitation occurred mostly as a result of the slow moving low-pressure system that passed through the region during the last week of the month. Despite this month’s precipitation, extreme to exceptional drought continues in California, Oregon, and Nevada due to the large precipitation deficit present after 3+ years of drought and the impacts observed in water resources and landscapes. Some improvement in drought conditions was observed in the eastern Great Basin, Arizona and New Mexico though moderate drought persists as drought-related impacts are still apparent.

An early season snow event affected southern Montana and northern Wyoming. Some locations in the mountains east of the Continental Divide in this region reported over 12 in (31 cm) of snow. Lower elevations saw up to 2 in (5 cm) of snowfall. Towards the end of the month, a slow moving and cold low-pressure system brought the first snowfall of the season to the Sierra Nevada. Up to 6 in (15 cm) of snowfall was observed at favorable high-elevation locations, with 1-3 in (2-8 cm) widespread in the range. The storm then tracked eastward and brought 1-5 inches (2-12 cm) of snow to Utah’s Uinta and southern Wasatch Mountains and the central Rockies.

Above normal temperatures dominated the West this month. Along the coast, North Bend, Oregon recorded an average 61.6 F (16.4 C) this month, 4.2 F (2.3 C) above normal. Further south, temperatures averaged 75.7 F (24.2 C) in San Diego, 5 F (2.8 C) above normal. This was the 4th warmest September on record for both North Bend and San Diego, with records beginning in 1902 and 1939, respectively. In the central Great Basin, Ely, Nevada recorded its warmest September at an average 61.4 F (16.3 C). Consistent records in Ely began in 1938. In southern Colorado, Alamosa also experienced its warmest September on record with an average of 58.7 F (14.8 C). Records for Alamosa began in 1948. Small areas of slightly cooler than normal temperatures were observed in parts of Arizona and New Mexico and also dotted Wyoming and Montana.

Precipitation was highly variable throughout Alaska this month. Fairbanks recorded 2.89 in (73 mm) of precipitation, 262% of normal and the second wettest September since records began in 1929. Further southwest, Bethel reported 1.26 in (32 mm), 46% of normal. Temperatures were generally above normal throughout with state, though some Interior locations were slightly cooler than normal. Homer, on the Kenai Peninsula, reported its warmest September since records began in 1932 at an average 53.2 F (11.8 C). Further south, precipitation was variable throughout Hawaii as well. Hilo observed 41% of its normal rainfall; Kahului recorded 186% of normal. The average temperature in Hilo this month was 79.4 F (26.3 C), 3.2 F (1.8 C) above normal and the warmest September in a 66-year record. Other stations in the state generally observed near-normal temperatures.

Significant Events for September 2014

September (all month): King Fire in northern California: The human-caused King Fire was ignited September 13 and spread rapidly due to strong southwest winds. The fire has charred over 97,000 acres (39,000 hectares) and destroyed 12 residences since it began. Smoke from the fire reduced air quality in the Reno/Lake Tahoe area as well as in the communities of the Sierra Foothills.

September (throughout month): Flooding in Southwest: Heavy precipitation associated with the northward movement of subtropical moisture brought several waves of flooding to the Southwest this month. During the first week of the month (8th-9th) southern Arizona, southern Nevada and southeastern California experienced flash flooding, road closures, and stalled or stranded vehicles. Two fatalities were reported near Tucson. Over the 16th -19th, southern and eastern New Mexico saw flooding that resulted in road closures and caused some localized areas to be evacuated. On the 26th -27th, heavy precipitation resulted in flooding that closed parts of Interstate 15 near Las Vegas, Nevada, debris flows in southern Utah, and flooding of homes in southwest Utah.

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