California and National Drought Summary for August 9, 2016

New England, the Northeast, and the Great Lakes Region

August 11, 2016 - Little or no precipitation fell on most areas, leading to intensifying and expanding dryness and drought in many areas. Extreme drought (D3) was introduced in northeast Massachusetts where 90-day rainfall deficits exceeded 8 inches. In other drought areas, shortfalls of 4 to 7 inches were common during this period. Areas of D1 and D2 in northern Pennsylvania, western New York, Ohio, lower Michigan, and eastern Indiana expanded significantly.

The Southeast and Lower Mississippi Valley

Heavy rains in the western Carolinas brought significant improvement to the western Carolinas. Reports of 3 to 6 inches were common across the region, with isolated higher amounts recorded. In the rest of the Southeast, heavy rainfall was common but not widespread, leading to a mixed pattern of improvement and persistence/deterioration, though improvement was more common. Most notably, heavy rains brought an end to dryness in parts of southern Florida and a swath through interior western Alabama, whittled away at the D3 areas from northern Mississippi eastward through western South Carolina, improved D2 to D1 in interior west-central Mississippi and south-central Tennessee, and reduced D1 coverage in southwestern Mississippi, adjacent Louisiana, and central Tennessee. Over the past 3 months, rainfall totals in areas of drought range from 3 to locally 10 inches below normal.

Texas

High temperatures and minimal precipitation led to expansion of dryness and drought in most of Texas, but heavy late-period rains in the Panhandle engendered some relief there. D0 and D1 expanded most notably in a swath through central Texas from near the middle Red River Valley southward through Deep South Texas, where little or no rain fell. Broad parts of this region received less than one-quarter of their normal rainfall since mid-June.

The Plains and Midwest

Moderate to heavy rain fell in a band from northern New Mexico northeastward through much of northern Oklahoma, Kansas, and the southern and northern reaches of Missouri, and adjacent Iowa last week, with amounts of 3 to 5 inches recorded in a few spots in north-central Missouri and adjacent Iowa, northern and southern Kansas, and northeasternmost New Mexico. Farther north, moderate to heavy rain was also observed in a smaller swath covering south-central to southeastern Nebraska. Light to moderate totals were observed in the central High Plains and eastern Iowa, and only a few tenths of an inch at best fell elsewhere. This pattern of variable precipitation amounts prompted numerous changes of relatively small scale. For instance, patches of deterioration were noted in South Dakota, western Iowa, and south-central Oklahoma while improvements were introduced in southern Nebraska, southeast Oklahoma, southern Kansas, and areas near the Iowa/Missouri border.

The Rockies and West

Seasonable monsoon rainfall was observed in Arizona (generally eastern areas), New Mexico, and the southern half of Colorado while little or no precipitation fell elsewhere, which is not uncommon this time of year. The precipitation pattern per se did not warrant making Drought Monitor changes, but water supply assessments undertaken in some states led to a more pessimistic re-assessment of conditions, particularly in Montana, and these are reflected in the Drought Monitor this week. Reservoir levels, streamflow levels, and surface moisture conditions prompted expansion of abnormal dryness and moderate drought, along with the introduction of large areas of severe drought, across the southern, central, and western sections of Montana. Smaller-scale deteriorations were also introduced in part of Idaho and Oregon.

Alaska, Hawaii, and Puerto Rico

Another relatively wet week was experienced in much of Hawaii. Abnormal dryness was eliminated in Oahu, leaving the state’s most populous island without any abnormal dryness or drought, but no changes were made anywhere else in the state. A second week of moderate to locally heavy rain trimmed the northward extent of the D0 in Puerto Rico, but left the small remaining D1 area intact. Moderate precipitation over the last few weeks prompted a reduction in the extent of D0 conditions in northwestern Alaska, but most of the area remained unchanged.

Looking Ahead

During the next 5 days (August 11 – 15), heavy precipitation (more than 1.5 inches) is expected in a broad swath from the Big Bend region in Texas eastward through upper central Texas, most of the Mississippi Valley, the adjacent central Gulf Coast, the Ohio Valley, the western Great Lakes region, and interior sections of the Northeast and New England. Amounts may reach 4 to 8 inches in the eastern half of Louisiana and adjacent locations, 3 to 6 inches in the Big Bend, 2 to 5 inches in the upper Midwest (centered near the Wisconsin/Iowa/Minnesota triple point), and 2 to 5 inches along and just north of the Ohio River. Moderate amounts are anticipated in the Southwest, eastern Colorado, most of Florida, the central Plains, and the southern reaches of the Northeast and New England. A few tenths of an inch at best are expected in most other areas, although amounts may approach an inch in the southern Appalachians. High temperatures will average a few degrees above normal in the Great Lakes region, mid-Atlantic, and Northeast, as well as the West Coast states away from the immediate coastline. Near- or below-normal temperatures seem likely elsewhere.

During August 16 – 20, the odds favor wetter than normal weather in a broad swath from the southern Rockies eastward through the southern Plains, lower Mississippi Valley, mid-Atlantic region, and Southeast (outside the Florida Peninsula). The odds also favor wet weather in the northern Great Plains. However, enhanced chances for drier than normal weather exist in the Northwest, the Intermountain West, central sections of the Rockies and Plains, and southern and eastern portions of the Great Lakes region. The odds favor warm weather from the Rockies westward, from the Appalachians eastward, and along the northern one-third of the Nation. In contrast, cooler than normal weather is favored from the Southwest eastward through the lower Mississippi Valley away from the immediate Gulf Coast.

Author(s):
Richard Tinker, NOAA/NWS/NCEP/CPC

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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 Drought

D2 ... 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)
Source: National Drought Mitigation Center