Discussion for the Seasonal Drought Outlook
Tools used in the Drought Outlook
included the official CPC precipitation outlook for January 2010 and the long lead forecast for
January - March 2010, the four-month Palmer drought termination and amelioration probabilities, 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, El Niño precipitation and temperature composites
for January - March 2010, climatology, and initial conditions.
Moderate to severe drought
continues in northwest Wisconsin. Soil moisture anomalies in this area currently remain negative. Although
medium-range forecasts predict above median precipitation in this region, precipitation amounts should not be
high enough to alleviate drought. Since long-range forecast guidance does not suggest the potential for
wetter than median conditions in this region, persistence is forecast. Precipitation typically increases
later in the spring.
Forecast confidence for Wisconsin is low.
Continued relief from the
protracted drought affecting parts of southern Texas appears likely. Precipitation forecasts at all time
ranges along with the ongoing El Niño strongly favor improvement for the Texas drought area.
Forecast confidence for Texas is high.
Despite the heavy precipitation
that occurred in early December, Winslow and Flagstaff, Arizona recorded their 2nd and 4th driest years,
respectively. Widespread drought continues for the Southwest and Four Corners region and dry weather has
prevailed since the winter storms in early December. Model guidance indicates that precipitation could return
by late January. CPC’s seasonal forecast for January through March indicates a slight tilt in the odds for
wetter than median conditions across southern parts of Nevada, Utah, and Colorado, with increasing odds for
wetter than median conditions across Arizona. The ongoing El Niño and its associated wet conditions for this
region suggest drought improvement for this drought area.
Forecast confidence for the Southwest and Four Corners region is moderate.
CPC’s 6-10 day and 8-14 day
precipitation forecasts call for increasing odds for above median precipitation over much of California and
Nevada. El Niño composites along with the CPC seasonal outlook favor above median precipitation during
January through March across central and southern California. Typically, the storm track along the West
Coast shifts south later in the winter. The CPC seasonal forecast is slightly less optimistic for above
median precipitation over northern California, northern Nevada and southern Oregon, where equal chances for
above, below or near median precipitation are indicated. With these considerations in mind, improvement
during this period is more likely across central and southern California with odds for improvement
decreasing farther north. Persistence is forecast for southeast Oregon and adjacent areas of Nevada.
Forecast confidence for central and southern California is high, and forecast confidence for northern
California, northern Nevada and southern Oregon is moderate.
Moderate to severe drought
continues in east-central Washington. Due to a lower than usual snowpack at this time of year, drought has
recently developed in western Montana. El Niño composites along with CPC’s monthly and seasonal outlooks
favor persistence and expansion of drought across east-central Washington and parts of Montana. Abnormal
dryness currently exists across eastern Idaho and extreme western Wyoming. Snow depth departures are as much
as 2 to 3 feet below normal in eastern Idaho and western Wyoming. Also, basin average snow water content
values are running 50 to 75 percent of normal in these areas. Due to these initial conditions and
correlations with previous El Niño events indicating below normal snowpack, drought development is forecast
in eastern Idaho and extreme western Wyoming.
Forecast confidence for Washington, Idaho, Montana, and Wyoming is moderate.
With the exception of northwest
Ohio, current stream flows are running at or above normal across Ohio. Precipitation has generally averaged
near normal during the past 30 and 90 days. CPC’s seasonal outlook for January – March indicates relatively
high odds for below median precipitation across the Ohio Valley. This is consistent with El Niño composites
for January – March, which favors below median precipitation. Despite a strong signal for drought development
during an El Niño winter, uncertainty in the precipitation forecast during the first 2 weeks of the period
combined with current moisture levels reduce confidence for drought development. Any such development, should
it occur, would take place late in the period.
Forecast confidence for Ohio and northern Kentucky is low.
As is consistent with an ongoing
El Niño, Hawaii is expected to receive below-median precipitation during this period. These dry conditions
will likely exacerbate ongoing areas of severe to extreme drought over Hawaii and also provide support for
drought development over the remainder of the Hawaiian Islands.
Forecast confidence for Hawaii is high.