National Drought Monitor for September 23, 2014
Looking Ahead
During the September 25-30 period, a large upper-level trough of low pressure will begin moving over the western CONUS from the Pacific. Temperatures will be warmer than normal for much of the country at the beginning of this period, but become cooler than normal in the West near the end of the period. The trough should bring precipitation to much of the West, with an inch or more expected from northern California to the Cascades of the Pacific Northwest, and an inch or more over much of the Northern Rockies. The precipitation is expected to miss southern California. Bands of frontal precipitation are likely in parts of the Plains and Midwest, in the Southeast, and along the Gulf of Mexico and Atlantic coasts, although the precipitation is forecast to miss large parts of the Plains to Midwest.
The upper-level pattern will slowly migrate to the east during October 1-8. The 6-10 day and 8-14 day outlooks indicate that the temperature pattern will be below normal in the West and above normal in the East, with above-normal temperatures eventually returning to the West Coast. The precipitation pattern should transition to drier than normal in the West and wetter than normal from the Rockies to the Great Lakes and Southeast as the weather-producing systems migrate eastward. An upper-level ridge over the eastern Pacific is expected to bring above-normal temperatures to Alaska, with wetter-than-normal conditions to the southern coastal locations and drier-than-normal conditions to the interior Alaskan locations.
Summary
The long-wave circulation pattern, during this U.S. Drought Monitor (USDM) week, consisted of an upper-level ridge over the western United States and trough over the east. This continued the trend of well-above-normal temperatures in the West and below-normal temperatures in the Midwest to Northeast. Low pressure systems, moving in the jet stream flow, dragged cold fronts across the contiguous United States (CONUS), bringing areas of precipitation to the northern Rockies, Plains, Great Lakes, and Southeast. Moisture from the remnants of Hurricane Odile deluged parts of the Southwest and western Texas with flooding rains, while a cold front spread moisture across portions of central and eastern Texas. Some of Odile’s tropical moisture fed monsoon showers over the Intermountain Basin. However, large parts of the Far West, Great Plains, and CONUS east of the Mississippi River had a drier-than-normal week.
The Plains and Midwest
With cooler-than-normal temperatures and areas of precipitation, no change was made to the USDM depiction in the Midwest, although mounting precipitation deficits were becoming a concern in northeast Minnesota. A weather system, that dropped 2-4 inches of rain over southwest Missouri, resulted in contraction of D0 there. But 30- to 90-day precipitation deficits continued to mount further east, with low streams becoming evident, so D0 expanded in east central Missouri. No change was made to the USDM depiction over the central and northern Plains, even though the week was mostly drier than normal. Areas of above-normal rain fell across Kansas, but they had little impact on agricultural conditions, so no improvement was made to the USDM depiction. The extreme dryness of the 2012-2013 drought severely depleted soil moisture in the state. As noted by the Kansas State Climatologist’s office, surface water supplies have not recovered materially, with ponds having a quarter to a third of normal capacity, even in areas receiving above-normal precipitation. The USDA reported up to 55% of the topsoil and 64% of the subsoil short to very short of moisture in some western crop districts, with 23% of pasture and range conditions poor to very poor statewide. Even in the northeast district, where soil moisture conditions were “wettest”, 15% of topsoil and 32% of subsoil were still rated short to very short of moisture.
The Northeast and Mid-Atlantic
It was another drier-than-normal week across the Northeast and Mid-Atlantic. Cooler-than-normal temperatures helped keep evapotranspiration down, but hydrological impacts were mounting in southern New England from the lack of rain. Streams were low from Connecticut to eastern Massachusetts, with soils drying and pastures and rangeland suffering. In Manchester, Connecticut, the Water and Sewer Department has issued a water conservation alert because its reservoir was below 80 percent of capacity; a ban on outdoor watering and other outdoor water uses took effect in Ipswich, Massachusetts as the rainfall deficit continued to build; and level 5 drought conditions were declared in Danvers, Massachusetts, due to low flow in the Ipswich River and the rapid depletion of the city’s reservoir. September 22 reports from the U.S. Department of Agriculture (USDA) indicated that 26% of the topsoil and 20% of the subsoil in New England was short to very short of moisture (dry to very dry), and 12% of the pastures were rated in poor to very poor condition. D1 (moderate drought) was added to the southern New England states and D0 (abnormally dry conditions) expanded northward (into parts of Maine) and westward (further into New York and Pennsylvania). Mounting precipitation deficits over the last 90 days prompted expansion of D0 in Virginia, southwest Pennsylvania, and southern Maryland.
The South
There were several reports of 5 inches or more of rain in parts of southeast, central, and west Texas for the week, resulting in contraction of D0-D3. Rainfall from the remnants of Hurricane Odile significantly improved reservoirs in west Texas, with Guadalupe Mountains National Park reporting a total of 13.58 inches of rain and Gail (in Borden County) reporting 18.24 inches. On the other hand, continued dryness in northeast Texas and central to western Oklahoma resulted in expansion of D0-D3 in those areas. While subsoil moisture improved, the USDA reported that topsoils in Oklahoma continued to dry out, with 55% of topsoil and 61% of subsoil statewide short to very short of moisture, and 20% of pastures and rangeland in poor to very poor condition. Conditions in Texas improved over last week, with 52% of topsoil and 63% of subsoil rated short to very short of moisture, and 34% of pastures and rangeland in poor to very poor condition.
The Southeast
Frontal rains dropped 1-3 inches of moisture in portions of southeast Georgia and adjoining northern Florida, prompting contraction of D0-D2, and 4+ inches of rain erased D0 in Pinellas County in western Florida. But continued dryness, especially over the last 60 to 90 days, caused the expansion of D0-D1 in other parts of the Southeast. D1 expanded in central Alabama and D0 expanded in North and South Carolina. Low streamflows and drying soils were causing vegetative stress in the northern Piedmont of North Carolina. The USDA reported that 55% of the topsoil and 54% of the subsoil in Alabama was short or very short of moisture, and 21% of the state’s pastures and rangeland were rated poor to very poor. In Georgia, the statistics were 31% of topsoil, 35% of subsoil, and 13% of pastures and rangeland. In southern Georgia, the dry land peanut crop in Irwin County was severely affected by drought and Lesser Corn Stalk Borer damage, and development of the dry land cotton crop was hindered by the drought. Irwin County is under D1-D2 conditions.
The West
The remnants of Hurricane Odile dropped 2 inches or more of rain along a path from southeast Arizona, across southern New Mexico, into western Texas this week, with locally 5 inches or more reported in many areas along with widespread flooding. A CoCoRaHS weather station near Carlsbad, New Mexico, reported 10.48 inches of rain during the week. Reservoirs along the Pecos River in southeast New Mexico were replenished by the Odile rainfall, including Brantley and Red Bluff. Significant improvement in the USDM depiction was made, with D1-D2 pulled back in southeast Arizona, D0-D3 pulled back in southern New Mexico, and much of southeast New Mexico now drought-free. However, the Odile rainfall, while beneficial, was not enough to eliminate 3+ years of drought in other parts of the state. A band of moderate drought (D1) remained from southwest to south central New Mexico, with an oval of severe drought (D2) in the southwest corner of the state. Areas to the north received very little to no rain from Odile. Another dry week added short-term dryness on top of long-term dryness, so D2-D3 was expanded in northwest New Mexico. USDA reports indicated that, on a statewide basis, soil moisture and pastures and rangeland improved in New Mexico, with the values decreasing to 52% of topsoil and 56% of subsoil short or very short of moisture and 32% of pasture and rangeland rated in poor to very poor condition.
Further to the north, beneficial rains improved D0-D3 in southwest Colorado and D0-D1 at the junction of Colorado, Wyoming, and Utah. But D0 expanded into northwest Montana and D1 expanded into the north central prairies and canyons of Idaho to reflect dryness which appeared as notable departures on the 30-day to 6-month Standardized Precipitation Index. Firefighting crews were fighting large wildfires in the northern Idaho D1 area. Monsoon showers dropped an additional inch or more of rain over parts of the intermountain basin, adding to the above-normal rainfall this area has received during the summer. D1-D2 were pulled back in southeast to east central Nevada to reflect the short-term gains made due to the monsoon/tropical moisture. Showers in parts of California dropped a few tenths of an inch of rain, but had little effect on drought conditions. Reservoir levels in the state continued to decline and groundwater wells continued to go dry. Record warm January-August temperatures across the West have intensified evapotranspiration and exacerbated drought conditions. With continued much-above-normal temperatures, the drought depiction across the rest of the West remained unchanged.
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