National Drought Monitor for August 12, 2014

2014 Drought

Looking Ahead

August 14 – 18, 2014 is expected to bring a swath of moderate to locally heavy rain (0.5 to 2.5 inches) from the northernmost reaches of the Cascades, Intermountain West, and Rockies southeastward through most of the Dakotas, the upper Mississippi Valley, the southern Great Lakes Region, and the Ohio Valley. Light rainfall is expected for most other regions of dryness and drought, with scattered moderate rains dampening the Rockies. Little if any precipitation is expected in much of Georgia and South Carolina, central and southern Texas, the Great Basin, and the Far West south of the Cascades.

The ensuing 5 days (August 19 – 23) favor above-median rainfall from the northern Rockies eastward through the northern Plains, the middle and upper Mississippi Valley, the Great Lakes, the Ohio Valley, the upper South, and the Northeast outside of New England. Below-median precipitation is anticipated for Oregon, Nevada, Utah, the Four Corners States, Texas, and adjacent parts of neighboring states. Elsewhere, neither unusually dry nor wet weather is favored.

2014 Drought

Hawaii and Puerto Rico

In Hawaii, heavy rains fell on most locations, primarily associated with then Tropical Storm Iselle. This brought an end to whatever dryness existed statewide, except for that associated with low reservoir levels in north-central Molokai.

In Puerto Rico, light to moderate rain fell on the area of dryness and drought, keeping conditions roughly unchanged from last week.

The Far West

It was seasonably dry along the West Coast, with measurable precipitation limited to parts of the Sierra Nevada and northeastern California. To wit, areas of dryness and drought remained unchanged. The major reservoirs in California are in aggregate at 59% of the historical average, still above the 41% of average recorded during the 1976-77 drought. But some reservoirs are below 1977 levels, especially in west-central parts of the state, and water restrictions have been imposed statewide.The Northeast

Light to moderate rain fell on the dry area in the Northeast, with a few locations reporting more than an inch of rain. No changes were made to the D0 area, where many locations are 2 to almost 4 inches below normal for the last 60 days.

The Rockies and Intermountain West

Generally moderate to heavy rains of 0.5 to locally over 3.0 inches fell from central Idaho and northwestern Wyoming southward through northeastern Nevada and adjacent Utah. Farther north, little or no rain fell, and across the southern half of the Rockies and Intermountain West, only scattered totals of over 0.5 inch and isolated reports topping one inch were noted.

Monsoonal rainfall was relatively light in most locations, and with little or no rain affecting the southern deserts of Arizona, D3 conditions were expanded throughout that region. Farther north, increasing deficits led to deterioration in several areas of Utah, and dryness and drought expanded in central and western Montana, where streamflows and vegetative health were declining. Across Utah, most of Arizona, and adjacent sections of New Mexico and southwestern Colorado, only one-half to two-thirds of normal precipitation has fallen during the last 6 to 9 months.

The elevation of the Lake Mead water level has dropped to 1080 ft. (54% of the historical average), the lowest since the lake was being filled in the 1930’s. This is closest Lake Mead has come to dropping to its “ration level one” of 1075 ft. It has been below its “drought” level of 1l25 ft. for 28 of the past 33 months.

Lake Powell is low, but faring better. After reaching a level of 3574 ft. in mid-April (just over the 3rd percentile since 1964, and 64% of the historical average), the lake rebounded to 3608 ft. at the end of July (20th percentile).
The Southeast

As in areas farther north, a highly variable rainfall pattern, but most locations received an inch or more of rainfall, with 4 to locally 6 inches reported in parts of the central and southern Appalachians and at scattered locations from southwestern Virginia southward through Georgia. In contrast, amounts under an inch were also scattered through the same region, especially prevalent in eastern North Carolina, the west-central Carolinas, and much of Georgia. This resulted in a number of relatively local changes to the Drought Monitor, among them the removal of D0 in parts of southwestern Virginia, western South Carolina, and eastern Georgia. However, abnormal dryness and moderate drought was expanded in southern Georgia and adjacent Florida, and across central Alabama. Most areas across south-central and southwest Georgia, northwestern Florida, and both central and far southern Alabama received 4 to locally 8 inches less than normal rainfall in the last 60 days.

The Southern Great Lakes, and the Ohio and Tennessee Valleys

Showers and thunderstorms resulted in a lot of spatial variability in rainfall totals. Moderate to heavy rains fell on a swath from southern Illinois eastward and southeastward through central and eastern Kentucky and the eastern half of Tennessee. In contrast, only light rain fell on much of western Kentucky, northwestern Tennessee, western Ohio, and most of Indiana. As a result, a new abnormally dry area was introduced from central Indiana into south-central Michigan, where less than half of normal rainfall was reported over the past 30 days, and deficits of 2 to almost 4 inches accumulated since mid-June. Farther south, in the swath of dryness and moderate drought in western Kentucky and northwestern Tennessee, the variable precipitation pattern essentially shifted these areas slightly westward toward the confluence of the Ohio and Mississippi Rivers. Deficits exceed 4 inches over the past 60 days in part of southwestern Kentucky and adjacent Tennessee.

The Western Great Lakes and the Plains States

Moderate to very heavy rain, 4 to 8 inches in some areas, fell on many locations from the northeastern half of Oklahoma, Kansas, and southern Missouri northward through southern South Dakota, southwestern Minnesota, and the southwestern half of Iowa. Moderate rain was more scattered through the rest of this large region, with 0.5 inch or less falling on most of the upper Midwest, the central High Plains, southwestern Oklahoma, and central through northeastern Texas.

As a result, areas of dryness and drought improved significantly across south-central South Dakota, central Nebraska, central Missouri, southeastern Kansas, central through eastern Oklahoma, and parts of central and northern Texas, plus a few smaller, isolated locations. The small area of exceptional drought was removed in eastern Colorado, and extreme dryness was eliminated in southern New Mexico, with additional improvements in other central and eastern parts of the state. However, in areas that missed the heavier precipitation, some areas of abnormal dryness were introduced, specifically in western Nebraska, western South Dakota, southwestern Wisconsin, north-central Iowa and adjacent Minnesota, and north-central Missouri. These areas generally received well under half of normal rainfall since mid-July, and 60-day shortages of 2 to almost 4 inches affect north-central Missouri, north-central Iowa and adjacent Minnesota, and southwestern Wisconsin.

Richard Tinker, NOAA/NWS/NCEP/CPC

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