November 2013

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Latest Monthly Assessment - The November 2013 Drought Outlook is based on initial conditions, short and medium range forecasts, the CPC updated monthly outlooks for temperature and precipitation, and climatology. During late October, heavy rains ahead of a slow moving cold front fell across parts of south-central and southeastern Texas, causing localized flooding in Austin and regions just to the southwest. Widespread rainfall associated with the same storm system also overspread eastern Kansas, Missouri, southern Iowa, and northern Illinois, with accumulations of an inch or greater observed. Additional rainfall in these areas are expected during the first week of November, as ridging builds over the Southeast, promoting slow frontal passages as new mid-latitude storms develop across the Mississippi Valley. Therefore, drought improvement or removal is anticipated across south central and eastern Texas and along the middle and lower Mississippi Valley. Further east, the ridging over the Southeast is forecast to prevent significant rainfall from reaching the Atlantic coast. Drought development is possible across parts of the Southeast, especially along the Savannah River basin, where 30-day percent of normal precipitation values are particularly low. Drought has also expanded across parts of the Northeast, and without a clear signal for wetness during the first half of November, persistence is anticipated. Uncertainty increases towards the end of the month, as coastal winter storms become more likely. November is a climatologically dry time of year across the Plains and intermountain West, making drought persistence most probable. Winter storm activity increases across the Pacific Northwest during late autumn, but sufficient precipitation to overcome current drought conditions is not likely to occur until later in the winter season, especially across California. Drought persistence is forecast for interior Alaska, where November is a climatologically dry time of year. Persistence is also anticipated across Hawaii, where the rainy season becomes most active beyond the monthly forecast period.

Tools used in the monthly U.S. Drought Outlook (MDO) included the official CPC temperature and precipitation outlooks for November 2013, various short- and medium-range forecasts and models such as the 6-10 day and 8-14 day forecasts, the NAEFS and ESRL precipitation outlooks, the soil moisture tools based on the Constructed Analog on Soil (CAS) moisture, dynamical models (CFSv2, NMME, and IMME), the 384-hour total precipitation forecasts from several runs of the GFS, the 7-day quantitative precipitation forecast from the NCEP Weather Prediction Center (WPC), climatology, and initial conditions. ENSO Neutral conditions are expected to continue through the fall season, and little mid-latitude impacts from a currently incoherent MJO pattern are expected, particularly during the first half of the month.

During the previous 30 days, less than 50-percent of normal precipitation was observed across most of the Eastern Seaboard states. The only exception was the Chesapeake Bay watershed and central Appalachians, where a slow moving coastal storm generated significant rainfall accumulations during early October. Abnormal dryness (D0) developed across parts of Florida, Georgia, and the Carolinas, and moderate drought developed over metropolitan areas of New York City, Long Island, and southeastern New England. During the first half of November, a pattern of mid- and upper-level ridging is forecast over the Southeast, which would suppress frontal intrusions to the Atlantic coast by shifting the storm track westward. 7-day precipitation accumulations generally under 1-inch are forecast for the first week of November, and there is little signal beyond Week-1. Based on the dry initial conditions and lack of a significant wet signal, persistence is forecast for the drought areas of the Northeast. A small area of drought development is indicated across the lower Savannah River basin along the Georgia and South Carolina border, where precipitation deficits are currently greater than 4-inches since September 1.
Forecast confidence for the Eastern Seaboard is low.

During late October, a slow moving cold front produced widespread rainfall along a swath from eastern Texas northeastward into the Great Lakes region. The heaviest accumulations fell across south-central Texas, where daily accumulations on 30 October topped 10-inches near and just southwest of Austin, TX. Widespread accumulations greater than 1-inch were also observed across existing drought areas of Missouri, southern Iowa, and Illinois. Additional rainfall is expected across the middle and lower Mississippi Valley as this cold front progresses eastward. During the first week of November, a second storm system is forecast to bring additional rainfall to these same areas, further relieving drought conditions. Both the CPC 8-14 day outlook and updated November monthly outlooks tilt the odds towards above-median precipitation in these areas. Based on the strong wet signal during the first half of November, drought improvement or removal is anticipated across eastern Texas and the Mississippi Valley.
Forecast confidence for the middle and lower Mississippi Valley and eastern Texas is high.

Although widespread heavy precipitation eased drought across the northern Plains, 60-day accumulations were generally below normal across the upper Midwest. Light to moderate precipitation is forecast during the first week of November as a storm system progresses through the middle Mississippi Valley, but most of the precipitation is anticipated to fall south and east of the upper Mississippi Valley. The CPC 8-14 day outlook indicates near normal precipitation, and the updated November outlook maintains equal chances of below, near, and above-median precipitation. November is a climatologically dry time of year for the upper Midwest. Based on the lack of a strong wet signal and the dry climatology, drought persistence is forecast for the upper Mississippi Valley.
Forecast confidence for the upper Mississippi Valley is moderate.

Widespread heavy rainfall is forecast during the first week of November across the eastern Plains, with forecasted totals topping 3-inches across eastern Kansas and Oklahoma. These regions are mostly drought free, however, with the core drought areas confined primarily to the High Plains. Light to moderate precipitation is forecast for the High Plains during early November. The CPC 8-14 day outlook indicates near normal precipitation, while the updated November outlook does not show a wet or dry signal. November is climatologically dry across the Plains, so significant drought improvements are unlikely without a clear wet signal. Based on these outlooks, drought persistence is anticipated across the Plains.
Forecast confidence for the Plains is moderate to high.

During early November, a storm system is forecast to impact the Pacific Northwest, bringing widespread precipitation to coastal Washington and Oregon and the adjacent Cascades. Mountain snowfall is also forecast for the northern and central Rockies, with the heaviest accumulations anticipated to be north of the existing drought areas of the Intermountain West and Pacific coast. The CPC 8-14 day outlook indicates enhanced chances of below-median precipitation across the central and southern Rockies, as well as the desert Southwest. Near or above-median precipitation is most likely across the Northwest, although the area of enhanced chances for above remains north of the drought areas in southeastern Washington and southern Idaho. The November updated outlook does not indicate a wet or dry signal across the Intermountain West, and tilts the odds towards below median precipitation across New Mexico and eastern Arizona. November is climatologically dry for the southern and central Rockies. Based on the lack of a wet signal during November, drought persistence is forecast.
Forecast confidence for the Intermountain West and the Pacific coast is moderate to high.

Although a stormy pattern is anticipated during early November across Alaska, November climatology is quite dry. It is unlikely that sufficient precipitation will fall during the month to overcome the deep initial drought conditions. Therefore, drought persistence is anticipated.
Forecast confidence for Alaska is moderate.

Widespread drought conditions persisted across much of Hawaii, particularly across the eastern islands. The winter season is a wet time of year across Hawaii, as mid-latitude storms generate increased precipitation across the islands. Climatologically, most of this activity occurs beyond the November period, making significant drought improvements unlikely by the end of the forecast period.
Forecast confidence for Hawaii is moderate.