California and National Drought Summary for May 26, 2015
Summary
An extraordinarily active weather pattern led to flood intensification across the central and southern Plains, culminating in a Memorial Day weekend deluge. The latest round of heavy rain pushed Oklahoma to its wettest month on record, based on preliminary data, supplanting October 1941. Showery weather extended beyond the Plains, reaching into the lower Mississippi Valley, parts of the upper Midwest, and much of the northern Intermountain West. Meanwhile, drier-than-normal conditions dominated much of the eastern U.S., where diminishing soil moisture began to have some adverse effects on pastures and summer crops. In contrast, beneficial rain dampened some of the hard-hit drought areas of the Far West, including parts of Oregon, Nevada, and northern California.Great Plains
Mostly dry weather returned to North Dakota, but the remainder of the nation’s mid-section continued to receive substantial rainfall. A small pocket of moderate to severe drought (D1 to D2) persisted from northeastern Nebraska into eastern South Dakota. Otherwise, the Plains were free of severe drought, with only a few remaining pockets of moderate drought—largely due to lingering hydrological concerns. In Texas, reservoirs were collectively 82.0% full by May 27, up from 73.2% a month ago and 62.5% six months ago. In the last month, reservoir storage in Texas has increased 2.77 million acre-feet.By May 26, month-to-date rainfall totals climbed to 18.97 inches in Oklahoma City, Oklahoma, and 14.53 inches in Wichita Falls, Texas. In both locations, those values represent the highest monthly totals on record. Previously, Oklahoma City’s wettest month had been June 1989, with 14.66 inches, while Wichita Falls’ had been May 1982, with 13.22 inches. Oklahoma City’s total was boosted by a daily-record total (3.73 inches) on May 23, part of a broad heavy rain event that led to catastrophic flash flooding in portions of the south-central U.S. In Texas, for example, preliminary USGS data indicated that the Blanco River at Wimberly rose more than 35 feet in less than 8 hours, cresting on May 24 at 27.21 feet above flood stage. The preliminary high-water mark at Wimberly was 6.91 feet above the previous record set on May 28, 1929. The San Marcos River near Martinsdale, Texas, surged more than 51 feet in less than 24 hours on May 23-24, based on initial data.
Hawaii, Alaska and Puerto Rico
No changes were made in Hawaii, Alaska, and Puerto Rico. Hawaii experienced a few periods of showers, mainly in windward locations. On Maui, Kahului’s 0.51-inch rainfall on the 23rd boosted its May 1-26 total to 1.06 inches (156% of normal). Elsewhere in Hawaii, May 1-26 rainfall included 0.58 inch (32% of normal) in Lihue, Kauai, and 0.15 inch (27%) in Honolulu, Oahu. Farther north, warm, dry weather across interior and southeastern Alaska contrasted with showery weather in the southwestern part of the state. The dryness in southeastern Alaska follows a very wet April; therefore, impacts have been slow to emerge. A few wildfires have been recently reported in Alaska, including the 556-acre Bolgen Creek fire south of Circle. Rivers are running high in some parts of Alaska due to early-season warmth melting high-elevation snow. Meanwhile, recent shower activity has been sufficient to stabilize the drought situation in Puerto Rico. Rain has been especially beneficial in northeastern Puerto Rico, where San Juan received 1.01 inches on May 20.Midwestern and Great Lakes States
Significant rain shifted eastward into Wisconsin and environs, leading to reductions in the coverage of dryness (D0) and moderate drought (D1). During the week ending May 24, topsoil moisture rated very short to short declined from 24 to 20% in Wisconsin. Additional rain arrived on May 26, after the drought-monitoring period ended, and will be reflected next week. Further analysis of the previous week’s rainfall led to some additional reductions in drought coverage in Minnesota.Southeast
Broad expansion of abnormal dryness (D0) was noted in the Southeast, with a new spot of moderate drought (D1) introduced in southern Georgia. Statewide, Georgia’s topsoil moisture was rated 59% very short to short by May 24. During the week ending May 24, pastures rated by USDA in good to excellent condition declined at least 5 percentage points in Virginia (from 62 to 55%); South Carolina (from 58 to 52%); and North Carolina (from 53 to 45%). Late in the drought-monitoring period (on May 25-26), rain began to spread into the Southeast, followed by additional rain that will be reflected next week.The Northeast
Isolated showers had little effect on the Northeastern dryness (D0) and moderate drought (D1). From March 1 – May 26, precipitation totaled one-half to two-thirds of normal in locations such as Boston (5.64 inches, or 52% of normal), New York’s Central Park (7.12 inches, or 58%), and Providence (7.42 inches, or 60%). Stream data from USGS indicated extremely low flows for this time of year from the northern Mid-Atlantic region into southern New England. According to USDA, topsoil moisture on May 24 was rated 80% very short to short in Connecticut, along with 70% in New Hampshire; 58% in Massachusetts; 54% in Delaware and New Jersey; and 52% in Maine.West
Similar to the previous drought-monitoring period, Western precipitation boosted topsoil moisture and eased irrigation requirements, but in many states provided negligible relief from long-term, hydrological drought. However, in areas where long-term drought was less deeply entrenched, particularly in Wyoming, Colorado, and parts of neighboring states, the recent and ongoing wet spell has put a meaningful dent in the drought.While most of the West has experienced an unusually cool, wet May, warmth has prevailed from the Pacific Northwest to the northern Rockies. As a result, an emerging area of short-term dryness (D0) has begun to appear near the Canadian border as far east as northwestern Montana.
Looking Ahead
During the next 5 days, the western U.S. will experience a warming trend, while near- to above-normal temperatures will continue in the East. In contrast, very cool weather will cover much of the Plains and Midwest. Meanwhile, heavy rain (locally 2 to 4 inches) will lead to additional flooding across the southeastern Plains and western Gulf Coast region. A broader area of the Plains and Midwest will receive 1 to 2 inches, with locally higher totals. Similar amounts can be expected in the eastern U.S., except along the southern Atlantic Coast. Elsewhere, showers in the Rockies and Intermountain West will contrast with warm, dry weather in the Pacific Coast States and the Desert Southwest.The NWS 6- to 10-day outlook for June 2 – 6 calls for the likelihood of near- to above-normal temperatures and precipitation across much of the nation. Enhanced odds of cooler-than-normal conditions will be limited to parts of Texas, while drier-than-normal weather will be limited to the Pacific Northwest and the northern Intermountain West.
Author(s):
Brad Rippey, U.S. Department of Agriculture
Dryness Categories
D0 ... Abnormally Dry ... used for areas showing dryness but not yet in drought, or for areas recovering from drought.Drought Intensity Categories
D1 ... Moderate DroughtD2 ... Severe Drought
D3 ... Extreme Drought
D4 ... Exceptional Drought
Drought or Dryness Types
S ... Short-Term, typically <6 months (e.g. agricultural, grasslands)L ... Long-Term, typically >6 months (e.g. hydrology, ecology)
