August in the West
An active monsoon circulation as well as the passage of several low-pressure systems produced above normal precipitation over much of the West this month. Temperatures were cooler than normal in a wide swath extending from southeastern California northeast to the Great Plains states while the Pacific Northwest and much of California experienced warmer than normal temperatures.
High pressure dominated over the Pacific Northwest this month producing average temperatures 2-6 F (1-3 C) above normal. In northwestern Oregon, Salem recorded its warmest August in a 122-year record at an average 72.5 F (22.5 C). August’s warm temperatures helped several locations in northern California and southwest Oregon achieve one of their top-10 hottest summers (June-August) on record. Temperatures averaged to 75 F (23.9 C) in Medford, Oregon, the hottest summer since records began in 1911. The previous record of 74 F (23.3 C) was set in 2013. In northern California, Montague reported an average 72.9 F (22.7 C) for the summer, the warmest in a 67-year record. August was the third warmest on record at Medford (77 F, 25 C) and the second warmest at Montague (73.7 F, 23.2 C). Cool air brought in by passing low-pressure systems as well as cloudiness associated with monsoonal precipitation helped moderate temperatures in the Southwest east of the Sierra Nevada and in the central and southern Rockies. Average August temperatures in these regions were 1-4 F (1-2 C) below normal.
During August’s first week, an upper level low over the Great Basin combined with a surge of monsoon moisture resulted in well above normal precipitation for many Great Basin locations. Reno recorded 1.03 in (26 mm) on the 4th and 5th; their August total of 1.08 in (27 mm) was 470% of normal, tied with 2013 for the 4th wettest August on record. Farther east, copious precipitation fell in southern Idaho on the 5th and 6th and again from the 20th-25th when monsoonal moisture interacted with another slow-moving upper level low. Twin Falls, Idaho, recorded 5.57 in (141 mm) for the month, 5.25 in (133 mm) above normal and by far the wettest August on record and the wettest of any calendar month at any station in the Magic Valley. These systems also brought very heavy precipitation to much of Montana. Saco, in the northeastern part of the state, observed a record 10.41 in (264 mm), nearly triple the previous August record of 3.51 in (89 mm) set in 1975; records there began in 1966. A low-pressure system passing over the Pacific Northwest on the 12th-15th helped to initiate thunderstorms in the region, resulting in above normal precipitation in parts of eastern Washington and Oregon. During this period, Ephrata, Washington, collected its total precipitation for the month of 0.83 in (21 mm), 437% of normal and tied for 4th wettest August in a 66-year record. Some areas of the desert Southwest saw above normal precipitation as well. Needles, in the Mojave Desert, recorded 2.22 in (56 mm) this month, 560% of normal. This summer has been the wettest in Needles’ 67-year record with a total 4.43 in (113 mm) of precipitation. This month’s precipitation improved drought conditions in southeastern California and western Arizona as well as parts of the central and northern Great Basin; however, large areas of extreme to exceptional drought remain in California, Nevada, and Oregon. As is typical for August, coastal locations saw little to no rainfall. Portions of New Mexico and Colorado saw drier than normal conditions as well.
In Hawaii, the windward side of the Big Island saw heavy precipitation in the beginning of the month associated with Tropical Storm Iselle. Hawaii Volcanoes National Park, at 3970 ft (1210 m) on the southeast side of the island, recorded 12.29 in (312 mm) of rainfall on August 8 alone. This was the 5th wettest day since the station began recording data in 1949. To the north, southeastern Alaska saw showery weather. Yakutat logged 23.17 in (589 mm) precipitation this month, 165% of normal and the 8th wettest August in a 98-year record. Temperatures were slightly above normal in Interior Alaska and considerably above normal in the far western portion of the state. Kotzebue saw an average temperature of 58.4 F (14.7 C) this month, 6.6 F (3.7 C) above normal and the 3rd warmest August on record. Records for Kotzebue began in 1897.
Significant Events for August 2014
August (all month): Heavy precipitation damages Idaho crops: Three Idaho counties have requested USDA disaster declarations due to crop damage from this month’s extreme precipitation. Wheat and barley crops were most affected since they were mature and nearing harvest.
August 7: Tropical Storm Iselle makes landfall in Hawaii: Iselle was the strongest tropical cyclone to make landfall on the Big Island in recorded history. Iselle reached peak intensity on August 4th as a category 4 hurricane, then weakened to a tropical storm just before making landfall on August 7. Iselle caused significant crop damage including losses to papaya operations estimated at $53 million. One death was reported due to flooding on Kauai.
August 19: Flash flooding in Yavapai County, Arizona: Heavy monsoonal rainfall flooded portions of Yavapai County (north of Phoenix). Fifteen miles of Interstate 17 were inundated and rock slides along the highway caused several vehicle collisions. Over 40 water rescues occurred throughout the day along with isolated major property damage.