Latest Seasonal Assessment -
The drought outlook for January 20, 2011 – April 2011 was based largely upon climate anomalies associated with a
La Niña as it is expected to persist throughout the period. Drought is forecast to continue across the
southeastern U.S. with development expected in coastal South Carolina. Drought persistence is also forecast
across southern parts of Louisiana and southeast Texas, while improvement or some improvement is anticipated in
northeast Texas, northern Louisiana, Arkansas, and the lower Ohio Valley. During the past month, drought has
expanded across the central and southern Plains, west Texas, and southern parts of Arizona and New Mexico.
Drought persistence and additional development can be expected in the southwestern U.S. and the central/southern
Plains. Drought relief has recently occurred in Hawaii, courtesy of winter rains associated with La Niña.
Continued improvement is forecast for the Hawaiian Islands.
Tools used in the U.S. Drought Outlook (USDO)
included the official CPC precipitation outlook for February 2011 and the long lead forecast for
February - April 2011, 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, La Niña composites for the December - February season, the four-month
Palmer drought termination and amelioration probabilities, climatology, and initial conditions.
An early start to the dry season
combined with a lack of tropical cyclone activity resulted in expanding drought across Florida. 2010 rainfall
departures below normal include 12.58 inches at Melbourne (3rd driest year on record) and 14.89 inches at
Vero Beach (5th driest year on record). Much needed rainfall occurred on January 17 when 2 – 5 inches fell in
parts of the Florida peninsula. Heavy rainfall (more than 2 inches) was also recorded in eastern
North Carolina. Across the southeast U.S., La Niña composites indicate the highest negative precipitation
anomalies in southern Georgia and the Florida panhandle. The CPC monthly and seasonal outlooks indicate
increased chances for below median precipitation across much of the southeast U.S., with the highest chances
across the Florida peninsula. Although the CPC 6-10/8-14 Day outlooks favor above median rainfall, drought is
expected to persist or develop across much of the southeast U.S.. This outlook is based primarily on the
ongoing La Niña and its associated dry signal.
Forecast confidence for Florida and southern Georgia is high, and moderate across Alabama, the Carolinas,
central Georgia, and Mississippi.
During the past month, northerly
flow resulted in drier than normal conditions across the lower Ohio Valley and the middle Mississippi Valley.
Despite the recent dryness, cold temperatures have led to little change in drought status across these
regions. The short and extended range forecasts for the next two weeks indicate a persistently dry pattern
for the lower Ohio Valley and middle Mississippi Valley. Despite this expected dryness, La Niña composites
along with the CPC monthly and seasonal outlooks favor above median rainfall in these areas. Across Arkansas,
mixed signals exist among most precipitation tools, but the outlook period is a relatively wet time of year.
Improvement is forecast for the lower Ohio Valley, middle Mississippi Valley, western Tennessee, while some
improvement is forecast across Arkansas.
Forecast confidence for the lower Ohio Valley, middle Mississippi Valley, and western Tennessee is
moderate and low for Arkansas.
From January 1 – 17, above median
rainfall occurred in northwest Louisiana along with eastern and southern Texas, while below median rainfall
was observed in southern Louisiana. The recent increase in rainfall has reduced drought severity and coverage
in eastern and southern Texas. 1-5 and 6-10 day forecasts indicate additional rainfall across the western
Gulf region, while CPC monthly/seasonal outlooks predict low chances for below median rainfall closer to the
Gulf Coast. Some improvement is forecast in northeast Texas and northern Louisiana due to prospects for more
rainfall during January. Persistence is forecast across southeast Texas and southern Louisiana where
monthly/seasonal outlooks tilt the odds slightly towards below median precipitation.
Forecast confidence for the western Gulf region is low.
Little if any precipitation has
occurred across the central/southern Plains and western Texas during the past month. Therefore, drought
conditions expanded or intensified across western Nebraska, eastern Colorado, Kansas, Oklahoma, and western
Texas. Precipitation tools at all time ranges indicate an elevated chance for below median precipitation in
these regions. Based upon the good agreement among precipitation tools, a relatively dry climatology, and
initial conditions, drought is likely to persist and develop across the central/southern Plains and western
Forecast confidence for the central/southern Plains and western Texas is high.
Since mid-December, drier than
normal conditions have affected much of Arizona and New Mexico. River basin snow water content values are
currently running 25 to 75 percent of average in southeast Arizona and most of New Mexico. Precipitation
tools at all time ranges indicate enhanced odds of below median precipitation. Due to a lack of adequate
snowfall so far this winter, a tendency for dryness during a La Niña, and forecasts of below median
precipitation, drought persistence and development can be expected across much of Arizona and New Mexico.
Forecast confidence for Arizona and New Mexico is high.
Heavy rainfall has recently reduced
drought conditions across the Hawaiian Islands which is typical for a La Niña winter. Although above median
rainfall is expected to continue and bring additional drought relief, long-term drought effects may linger.
Forecast confidence for Hawaii is high.