2004-12-07_PERMIT FILE - C1984063

Home Browse Search

• 7. Climatological Information Weather patterns within the area are associated with two general weather systems. During the winter months (October - April), moist Pacific air, transported by frontal systems, move eastward across the area. Orographic lifting of this moist air mass results in winter storms covering relatively broad areas. Summer weather patterns are often derived from warm moist air originating in the Gulf of Mexico. Thermal heating of this air creates localized upward movements and high intensity thunderstorms. These storm cells are generally about one mile in diameter and move across the terrain in an erratic pattern. The average annual precipitation at the NDAA climate station in nearby Rifle C5,432 feet in elevation) is 11.3 inches. Mean monthly precipitation for the Rifle station is shown in Table 22: Mean Annual and Monthly Precipitation - Rifle, Colorado. Precipitation is distributed fairly evenly throughout the year, with the maximum monthly amount associated with thunderstorm activity during the month of August. Estimated rainfall amounts for selected durations and return intervals are displayed in Table 12: Maximum . Expected Rainfall Amounts per Durations for Selected Recurrence Intervals for the West-Central Colorado Coal Area. Area temperatures are moderate to cool with a range of -6o F to 97o F, and a mean annual temperature for Rifle of 47o F (BLM, 1983). Typically, there is a variance of 10 to 25o F between day and night time temperatures. The prevailing wind direction in the area of the permit is from the west-southwest to the east-northeast. Because the local area is somewhat sheltered from the regionally prevailing northwesterly winds by the Grand Hogback, winds are locally moderate ranging from 1 to 12 mph. Wind direction versus wind speed are shown in Table 13: Wind Direction versus Wind Speed. The wind rose for the Rifle station is shown in Figure 17: Rifle Wind Rose. r1 ~J 70 Revised 5/87