Latest Seasonal Assessment -
The drought outlook for December 15, 2011 – March 31, 2012 was based upon climate anomalies associated with La Niña, short to
medium range forecasts, climatology, and initial conditions. Persistence or development can be expected across much of the
Southeast with the highest forecast confidence in Florida. However, the prospects for improvement increase closer to the
southern Appalachians. Since early November, frequent precipitation and seasonably cooler temperatures resulted in drought
improvement across the southern Plains. Additional improvement can be expected in southeast Kansas, eastern Oklahoma, and
northeast Texas, while monthly and seasonal precipitation forecasts favor persistence across the remainder of Texas and the
southern high Plains. Despite the early winter snowfall in Arizona and New Mexico, La Niña elevates the odds for drought
persistence across the Southwest. Drought development is forecast for parts of California associated with a dry La Niña
signal, and development potential extends north into the southern Sierras due to a lack of early winter snowfall. A relatively
dry winter climatology elevates the chances for persistence across the western Corn Belt and upper Mississippi Valley. Drought
improvement is forecast for Hawaii which is consistent with a La Niña winter.
Discussion for the Seasonal Drought Outlook
Tools used in the U.S. Drought Outlook (USDO)
included the official CPC temperature and precipitation outlooks for January 2012
and the long lead forecast for January 2012 - March 2012, various medium- and short-range forecasts and
models such as the 6-10 day and 8-14 day forecasts, the soil moisture
tools based on the GFS model and the Constructed Analogue on Soil (CAS) moisture, the Climate Forecast
System (CFS) seasonal precipitation forecasts, the four-month Palmer drought termination and amelioration
probabilities, climatology, and initial conditions.
Since the La Niña event of 2010-2011, widespread moderate to extreme drought remains entrenched across much of the
Southeast. La Niña conditions returned during fall 2011 and are expected to persist throughout the outlook period. The
CPC January-March outlook favors below median precipitation across the southern half of Alabama and Georgia along with
the coastal Plain of the Carolinas. Persistence or development can be expected across these areas. Meanwhile, closer to
the Tennessee Valley and southern Appalachians, the 6-10/8-14 Day outlooks along with the CPC January-March outlook tilt
the odds towards above median precipitation. A small swath of improvement or some improvement is forecast across northern
Alabama/Georgia and the upstate of South Carolina. March is a relatively wet month across the mid-South and improvement
could extend farther south into central Alabama/Georgia depending on the storm track later this winter into the early
Forecast confidence for the Carolinas, Georgia, and Alabama is moderate.
Although the rainy season eased drought conditions across the Florida peninsula, the return of La Niña strongly favors
drought development in central and south Florida. Below average water levels (1 foot or more) are observed at Lake
Okeechobee at the beginning of the dry season and probabilities of below median rainfall through the winter are greater
than 60 percent in south Florida. Extreme drought continues across the Florida Panhandle which missed the heavier summer
and early fall rainfall. Despite much-needed rainfall (> 3inches) on December 11-12, 2011, the rainfall deficit since
January 1, 2011 remains more than 22 inches at Tallahassee, Florida. La Niña composites and the CPC January – March
outlook indicate a relatively high probability for below median precipitation across the Florida Panhandle where
persistence is forecast.
Forecast confidence for Florida is high.
Since early November, frequent rainfall has nearly eliminated drought across Arkansas and ameliorated drought across
northern/western Louisiana. During the remainder of December, a continued wet pattern is expected to potentially end any
lingering drought across southwest Arkansas and bring additional improvement to northwest Louisiana. However, below
average rainfall has resulted in a return of severe drought to the southeast parishes of Louisiana and a continuation of
moderate drought along the Mississippi Gulf Coast. La Niña composites and the CPC January – March precipitation outlook
favor persistence across southern portions of Louisiana and Mississippi.
Forecast confidence for the lower Mississippi Valley is high.
Frequent periods of wet weather coupled with seasonably cooler temperatures have resulted in drought reduction across the
southern Plains, most notably across Kansas, Oklahoma, and north Texas. During the past 30 days, 2 to 5 inches of
precipitation was observed across these areas with the heaviest amounts in southeast Oklahoma. According to the Oklahoma
Mesonet, Broken Bow has recorded 11.05 inches of precipitation since November 13. Short and medium-range forecasts
indicate 1-3 inches of rainfall in southeast Kansas, eastern Oklahoma, and northeast Texas. Due to this expected wetness
and relatively low probabilities for below median precipitation in the CPC January-March precipitation outlook,
improvement is forecast in southeast Kansas, eastern Oklahoma, and northeast Texas. Across the remainder of Texas and the
high Plains of Kansas and Oklahoma, higher probabilities for below median precipitation in the CPC January-March
precipitation outlook and limited precipitation amounts expected during the short to medium-range favor drought
Forecast confidence for the southern Plains is high.
Since mid-November, shortwave troughs digging into the desert Southwest have resulted in widespread moderate to heavy
snow across the higher elevations of Arizona and New Mexico. As of December 11, basin average snow water content values
are running 100 to 135 percent of average across the mountains of Arizona and north-central New Mexico. Despite the near
to above average precipitation during the past 30 days across Arizona, New Mexico, and southern Colorado, precipitation
tools on all time scales favor below median precipitation which is typical for a La Niña winter. Therefore, drought
persistence is forecast across the Southwest.
Forecast confidence for the Southwest is moderate.
Rain and mountain snow has brought near normal precipitation amounts to southern California since mid-November.
Meanwhile, farther to the north, little or no precipitation has affected northern/central California and the northern
Great Basin. As of December 11, basin average snow water content values are running less than 25 percent of average in
the Sierras. Precipitation tools on all time scales along with La Niña composites tilt the odds towards below median
precipitation across the southern half of California and southern Nevada. By the end of March, drought development is
expected in areas of California and Nevada that are expected to experience relatively dry conditions from mid-December
through March. Development is also forecast for the southern Sierras that are off to an unusually dry start to the wet
Forecast confidence for California and Nevada is low.
Drought coverage and intensity has remained nearly steady across the western Corn Belt and upper Mississippi Valley
during the past two weeks. During the remainder of December, the primary storm track is expected to remain southeast of
these drought areas. The CPC January and January-March outlooks indicate equal chances for below, near, or above
precipitation. A dry climatology limits prospects for significant drought relief. Furthermore, since the ground and
streams in this region freeze over during the winter months, it is likely that the benefits of improved moisture would
not be realized until the spring thaw, which occurs at the end of this outlook period. Therefore, persistence is favored
across the western Corn Belt and upper Mississippi Valley.
Forecast confidence for the western Corn Belt and upper Midwest is moderate.
Drought redeveloped during the summer months across the western portions of the Hawaii, but recent rainfall reduced
drought coverage across the Big Island. During a La Niña winter, wetter than average conditions are typically observed,
particularly after January. Based on these climate anomalies, drought improvement is forecasted for the leeward sides of
the Hawaiian Islands.
Forecast confidence for the Hawaii is moderate.