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Drought monitor update for 11/8/12

10:18 PM, Nov 8, 2012   |    comments
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After last week's devastation caused by Hurricane/Superstorm Sandy, calmer conditions slowly returned as the storm weakened over the eastern Great Lakes region and tracked northward.

In its place, an upper-level trough of low pressure settled over the Northeast, producing unsettled weather (light precipitation and subnormal temperatures) to much of the Great Lakes region, New England, and mid-Atlantic. Unfortunately, a new Nor'easter threatened areas hit by Sandy as the period ended.

In the West, a series of Pacific systems dropped moderate to heavy precipitation (1 to 3 inches, locally up to 8 inches) on northern California, coastal Oregon, western Washington, and the northern Rockies. Meanwhile, a persistent ridge of high pressure located over the central Rockies kept the Southwest, Great Basin, and southern halves of the Rockies and Plains unseasonably mild and dry.

The weakened Pacific storm systems were diverted northeastward into south-central Canada by the ridge, then southeastward by the eastern trough into the northern Plains, lower Missouri Valley, the Delta, and across the Southeast. This brought light precipitation (0.1 to 0.5 inches, locally an inch) to the aforementioned regions. In Hawaii, mostly dry weather prevailed while stormy weather soaked the southeast Alaskan Panhandle.

The Northeast and Mid-Atlantic: As Superstorm Sandy gradually weakened over the eastern Great Lakes region and slowly tracked northward into southeast Canada, windy, cold, and showery weather enveloped the region. Light to moderate precipitation amounts (0.3 to 1 inch) fell on the eastern Great Lakes region, New England, and the mid-Atlantic, with locally over 2 inches in northeastern Ohio and most of Maine. With another 1 to 1.5 inches of rain, long-term deficits were reduced enough in central New York (Tompkins, Otsego, and Schoharie counties) that D0 was erased. However, lighter totals fell east of eastern Lake Ontario during Sandy, and with growing short-term deficits, D0 was expanded into Jefferson County.

Farther south, little or no rain (less than 0.3 inches) fell on southern Virginia and adjacent central North Carolina, adding to short-term (30- and 60-days) departures. USGS stream flows have dropped below the 25th percentile at 1-, 7-, 14-, and 28-days at several sites. Accordingly, D0 was expanded southward, and this area will be closely monitored for future deterioration.

The Southeast: Although light rains (0.3 to 0.8 inches) fell on most of Alabama and Georgia this week, short-term dryness (past 30 and 60 days) have accumulated deficits of 2 to 4 and 3 to 6 inches, respectively, from southeastern Alabama northeastward into central North Carolina. In fact, the central and eastern Carolinas saw little or no rain this 7-day period. This short-term dryness comes in the face of a severe 2-year drought where the deficits were never truly alleviated. As a result, D0 was expanded into southwestern Alabama and across northeastern Georgia and western South Carolina. Surplus amounts at 90-days across north-central North Carolina and the Piedmont prevented D0 development from connecting with D0 in south-central Virginia, but continued dryness will probably require a broad D0 expansion there soon. D1 expansion occurred in southeastern Alabama, central South Carolina, and south-central North Carolina, while D2 increased into southeastern Alabama and western South Carolina. The D3 and D4 areas were redrawn to reflect the largest AHPS deficits at 180-days and year-to-date. The two areas of worst long-term drought (at 1 and 2 years) stretched from southwestern Georgia northeast into west-central South Carolina, and from east-central Alabama northeast into northwestern Georgia. For example, Augusta, GA, only received 0.17 inches of rain the past 30 days, and was nearly 30 inches below normal over the past 24 months (driest on record since 1942). Numerous USGS stream levels are below the tenth percentile, and several are at near- to record lows for early November.

The Southern Plains and Delta: According to the 1981-2010 normals, October is the third wettest month for the Texas, but instead last month was one third of normal and the ninth driest October statewide since 1895. This week offered little change to the dry theme as much of Texas and Oklahoma recorded above normal temperatures and little or no rain. The lone exception was in southeastern Texas (1 to 3 inches). In Oklahoma, the OCS Mesonet noted that it has been 52 days since parts of the state have seen at least 0.25 inches of rain in one day. The combination of warm and dry weather was taking a toll on grasses and small grains. Winter wheat was running out of moisture and was rated 30 percent poor to very poor as of Nov. 4, up from 12 percent a week ago. Topsoil moisture conditions continued to decline, with 88 percent rated short to very short, while subsoil moisture similarly rated dropped to 94 percent. With the recent unfavorable weather conditions, deteriorations were made to Oklahoma (D3 and D4) and most of Texas (D1-D4). With so much of Oklahoma already in D3 and D4, it is getting difficult to degrade the state further. An exception was in extreme southeastern Colorado (Baca County) and the immediate area where further assessment of indices and actual conditions warranted an improvement from D3 to D2. In contrast, the rains in southeast Texas were enough to remove D0 in Polk and San Jacinto counties; however, but drier conditions to the east expanded D0 into southwestern Louisiana while D1 was added in extreme southeastern Texas and southwestern Louisiana due to short-term (60-day) shortages of 6 to 9 inches.

In the Delta, rains were more scattered, with the greatest totals in extreme southern Louisiana (1 to 2 inches), most of Mississippi (0.5 to 1.5 inches), and southern Arkansas (0.3 to 1 inch). From 60-days out to a year, most of Arkansas has reported near or above normal precipitation, and after a reassessment of all indices and products, improvements of a category were made across most of the state (except the northwest) which corresponded to AHPS, ACIS, and CPC anomalies at medium- to long-term time scales.

Central and Northern Plains and Midwest: Weekly weather conditions contrasted as one traveled from the central Plains (warm and dry) to the northern Plains and upper Midwest (cool and showery). Similar to Oklahoma, Kansas also recorded little or no precipitation with temperatures averaging 2 to 8 degF above normal. As this was the third straight week with minimal precipitation, a 1-category downgrade was made for east-central Kansas as eastern sections of the state normally record greater cold season moisture than western areas so shortfalls accumulate at a greater rate. No changes were made in western Kansas and most of Nebraska as much of it is already in D3-D4, leaving little room for downgrade. Topsoil and subsoil moisture continued to drop, and surface water supplies remained short. With light precipitation and subnormal temperatures, no changes were made in South Dakota, Minnesota, Wisconsin, Iowa, and Missouri. The U.S. Army Corps of Engineers in St. Paul, MN, said that they are preparing to store future precipitation within the Mississippi River Headwaters reservoirs during the next few weeks in an effort to ease drought conditions and support navigation south of St. Louis, MO, later this year. In northern North Dakota and westward into Montana, another week of light precipitation (0.3 to 0.8 inches) aided soil moisture conditions, resulting in a 1-category improvement. But drier conditions in southwestern North Dakota slightly expanded D2 there. Farther east, light to moderate precipitation (0.5 to an inch) and a reassessment of medium- to long-term conditions resulted in some 1-category improvements in lower Michigan and parts of the lower Ohio River Valley. In central Kentucky, a dry 30 days (2 to 4 inch deficits) have brought out lingering soil moisture deficiencies created earlier this summer, and D0 was expanded there.

The West: Decent precipitation (more than 2 inches) fell on non-drought areas of Washington, Oregon, and northern Idaho, while 3 consecutive weeks of light to moderate precipitation have fallen across Montana. Surpluses of 1 to 3 inches have accumulated during the past 30 days, easing drought across the northern two-thirds of the latter state. In addition, a slight improvement of dryness and drought were made along the edges of the D0 and D1 western borders in northern California, central Oregon, and central Idaho where recent storms have dropped enough precipitation to create small 30-day surpluses. Although the 2012-13 Western Water Year is still early, basin average precipitation percent of normals were above normal from the northern Sierra Nevada northeastward into central Montana. Unfortunately, the Great Basin and Southwest were well below normal, but their typical wet season generally starts later in the winter. Elsewhere, slight degradations were made in New Mexico based upon several indices and products. D2 was expanded into southeastern and north-central portions, while D3 increased in northeastern sections. The remainder of the West was left status quo, except for changing the Impact Type to L (from SL) as the short-term dryness has recently abated.



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