California and National Drought Summary for July 21, 2015
Summary
This U.S. Drought Monitor week saw improvements in the Southwest as overall conditions continued to improve across parts of the region. Improvements primarily were focused upon west-central New Mexico and northern Arizona where most long- and short-term indicators have pointed toward improvements, although reservoir storage levels in various drainage basins remain below normal. During the weekend, residual moisture associated with Hurricane Dolores fueled showers and thunderstorms across southwestern California and western Arizona leading to locally heavy rainfall accumulations and flash flooding. Despite well-above-average precipitation in southern California during the past 90 days, recent rainfall has had little impact on the overall drought situation in the state. In the Pacific Northwest, above average temperatures and precipitation deficits continue to mount across the region with growing concern about potential crop losses in central and eastern Washington. Moving eastward, short-term precipitation deficits led to slight deterioration of conditions in the northern Plains while locally heavy rainfall was observed across drought-free areas of Illinois, Indiana, Ohio, Kentucky, and Missouri. In the Southeast, conditions continued to deteriorate across portions of Alabama, Georgia, and South Carolina where excessive heat and lack of rainfall dried soils and reduced streamflows. According to the National Centers for Environmental Information (NCEI) climatological rankings, the contiguous U.S. average temperature for June was the second hottest in the observational record (1895–2015). On a state level, California, Idaho, Oregon, Utah, and Washington all experienced their hottest average-temperature Junes on record since 1895.Hawaii, Alaska, and Puerto Rico
On this week’s map, minor improvements were made on the island of Maui in an area of Severe Drought (D2). Elsewhere in the Hawaiian Islands, conditions remained status quo on the map. In Alaska, above-normal precipitation during the past 30 to 60 days led to the removal of an area of Abnormally Dry (D0) in southeastern Alaska. Further north, a one-category improvement was made in areas of Moderate Drought (D1) on the Kenai Peninsula and in the Interior where Water-Year-to-Date precipitation accumulations at various NRCS SNOTEL sites reported normal or near-normal precipitation. In Puerto Rico, an area of Extreme Drought (D3) was introduced in southeastern Puerto Rico where water rationing measures will be going into effect.Mid-Atlantic
Minor changes were made on this week’s map with the slight expansion of an area of Moderate Drought (D1) in south-central North Carolina where soils continued to dry out and streamflow conditions dipped to less than the 10th-percentile range. For the week, notable rainfall accumulations in the region centered on western portions of West Virginia, while Virginia and North Carolina received spotty rainfall with some isolated heavy rainfall accumulations. Looking at the 30- and 60-day precipitation departures, there’s a clear divide between northern and southern portions of the region with North Carolina being drier than states to the north. Average temperatures for the week were generally near-to-slightly-above normal except for some eastern portions of Virginia. The seven-day maximum temperatures across the region reached to the mid-to-high 90 degrees F.Midwest
The Midwest remained drought-free on the map this week. Locally heavy rainfall accumulations (three-to-six inches) were observed across parts of Illinois, Indiana, Kentucky, Missouri, and Ohio. Looking at the short-term (30-day) percentage of normal precipitation and the Vegetation Drought Response Index (VegDRI, a satellite-derived vegetative stress index), a few pockets of dryness are showing up in northern Iowa, northern Michigan, northern Minnesota, and eastern Wisconsin. During the past week, average temperatures were above normal in Illinois, Indiana, Iowa, Kentucky, northern and southern Minnesota, and Missouri while Michigan, central Minnesota, and Wisconsin were below normal.The Northeast
On this week’s map, no changes were made in the Northeast since areas currently in Abnormally Dry (D0) and Moderate Drought (D1) received only minor precipitation accumulations (generally less than one inch). Average temperatures were generally near-to- slightly-below normal while temperatures were three-to-five degrees below normal in Maine. Overall, it was dry across the region this week with the exception of a few isolated areas receiving light-to-moderate accumulations (two-to-three inches) in central Pennsylvania and northern Vermont.The Plains
Across the central and northern Plains, temperatures were near normal in eastern portions while western parts were below normal. In the southern Plains, temperatures were near- to-slightly-above normal for the week. The heaviest rainfall accumulations (two-to-four inches) were observed in isolated pockets of northwestern Kansas and the Oklahoma Panhandle, while lesser amounts (one-to-three inches) were recorded in the central and northern Plains. On the map, areas of Abnormally Dry (D0) expanded in Kansas, North Dakota, and South Dakota where short-term precipitation deficits exist.The South
During the past week, the South was generally hot and dry. The only areas receiving rainfall (one-to-two inches) were northern portions of the Texas Panhandle and the Trans-Pecos region of west Texas. The NWS WPC Quantitative Precipitation Forecast (QPF) calls for the dryness to continue across most of Texas during the next seven days. On the map, only minor changes were made in east Texas where two small areas of Abnormally Dry (D0) were introduced in response to short-term dryness. During the past week, temperatures were above normal in Louisiana, Mississippi, east Texas, parts of the Panhandle, and in the Trans-Pecos. Maximum temperatures observed were in the high 90 degrees F in eastern portions of the region, while temperatures exceeded 100° F in western portions.The Southeast
During the past week, temperatures were above normal across most of the region with maximum temperatures exceeding 100° F in Alabama, Georgia, and South Carolina. The overall hot and dry pattern led to expansion of areas of Abnormally Dry (D0) and Moderate Drought (D1) in northern and southern Alabama, central and southern Georgia, and northern portions of South Carolina. Some isolated shower activity in southern Georgia led to minor improvements in an area of Severe Drought (D2). In Florida, rainfall was spotty across the state with some locally very heavy accumulations observed along the west-central coast where four-to-nine inches fell during the seven-day period. One-category improvements were made in areas of Moderate Drought (D1) and Severe Drought (D2) in northern Florida where July rains have improved local conditions. In south Florida, short-term precipitation deficits (60-day) continue to mount leading to expansion of Moderate Drought (D1) in Palm Beach, Martin, and Saint Lucie counties.The West
During the past week, average temperatures were below normal across much of the West with the exception of western portions of California and Oregon, eastern New Mexico, and Washington. During the weekend and into Monday, moisture associated with Hurricane Dolores triggered showers and thunderstorms across parts of southern California and western Arizona. Some locally heavy accumulations (two-to-four inches) and flash flooding were reported. Despite well-above-average precipitation during the past 90-days in parts of central and southern California, the Sierras, and portions of the Great Basin, the recent rains have not impacted the overall drought situation in these areas because significant precipitation deficits remain as well as agricultural and hydrological (low reservoirs, below normal streamflows) impacts. In the Pacific Northwest, precipitation has been below normal since the beginning of the Water-Year (Oct. 1). The trend has continued during the past 60-days leading to very low streamflows, dry soils, and increasing concern in the agricultural sector. In the Southwest, some improvements were made on this week’s map in areas of Severe Drought (D2) in west-central New Mexico as well as east-central and northern Arizona where long- and short-term drought indicators (precipitation, soil moisture, streamflows, and vegetative health) have shown improvement during the past year. However, according to the Natural Resource Conservation Service (NRCS), statewide reservoir storage remains below normal in both Arizona and New Mexico. According to the Salt River Project (SPR), the Salt River system reservoirs are currently 53% full while the Verde River system reservoirs are 52% full. In New Mexico, Elephant Butte (the state’s largest reservoir on the Rio Grande) is currently 27% of average – up 9% from the same time last year. Elsewhere, statewide reservoir storage is above average in Colorado, Idaho, Montana, and Wyoming.Looking Ahead
The NWS WPC 7-Day Quantitative Precipitation Forecast (QPF) calls for generally dry conditions across most of the western U.S. with the exception of some modest accumulation (one-to-two inches) in northern portions of the Great Basin, northern Rockies, and North Cascades. In contrast, the central and northern Plains and western portions of the Midwest are forecasted to receive one-to-three inches while heavy precipitation is forecasted in southern Georgia and Florida with totals in the three-to-seven inch range. The CPC 6–10 day outlooks call for a high probability of above-normal temperatures east of the Rockies as well as along the West Coast while most of the interior West will be below normal. Across the West (with the exception of extreme southeastern Arizona and southwestern New Mexico), there’s a high probability of below-normal precipitation while the central and northern Plains, western portions of the Midwest, Northeast, and Southeast have a high probability of above-average precipitation.Author(s):
David Simeral, Western Regional Climate Center
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)
