Tools used in the Drought Outlook included the
official CPC precipitation outlook for August 2009 and the long lead forecast for August – October 2009,
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 August–October, climatology, and initial conditions
During the late spring and early summer, drought has expanded across Minnesota
and the upper peninsula of Michigan, while drought has worsened in parts of
Wisconsin. Little or no drought relief is expected in short or medium range.
However, median rainfall amounts are relatively high during August. Since El
Niño composites from August – October indicate variable conditions within the 3-
month time period, some improvement is forecast.
Forecast confidence for Wisconsin and Minnesota is low.
In Oklahoma, an upper-level ridge centered over the southern plains has resulted
in triple digit high temperatures during the past several days. As the upper-
level ridge weakens and shifts westward, northwest flow aloft should favor an
increasing threat for mcs activity and much-needed rainfall. Therefore,
improvement is forecast across Oklahoma. El Niño composites for August – October
also indicate odds for improvement in the southern high Plains. Improvement is
also forecast for the small drought area in southern Nebraska.
Forecast confidence for Oklahoma and Nebraska is moderate.
Since early June, drought was eliminated in far west Texas, while exceptional
drought conditions continue across south Texas. As of July 15, precipitation
deficits (inches) since January 1 include: 7.68 at Austin, 10.21 at San Antonio,
11.55 at Corpus Christi, and 14.72 at Victoria. Since tools extending through
August favor below-median rainfall, drought should persist across south Texas.
With the arrival of El Niño, relief may occur later in the fall and winter. Some
improvement is forecast in northwest Texas and southeast Texas where short-term
rainfall may provide relief.
Forecast confidence for Texas is moderate.
After an extended period of hot, dry weather that has resulted in drought
expansion across the lower Mississippi Valley, a pattern change should bring
more seasonal temperatures and a better chance for rainfall in the short and
medium range. HPC’s 5-day precipitation forecast indicates several inches of
rainfall across Louisiana and southern Mississippi. Although the CPC August
outlook calls for enhanced chances for below-median rainfall along the western
Gulf coast, a return of more typical summertime conditions during the remainder
of July should bring short-term relief. A wet climatology also supports
improvement. Improvement or some improvement is now expected in this region.
Forecast confidence for Louisiana and southwest Mississippi is moderate.
Drought was recently eliminated in Arizona and has been reduced in New Mexico.
Despite a recent lull in the monsoon, it typically reaches its peak intensity
during August. The CPC August-October outlook calls for enhanced odds for above
median precipitation across the ongoing drought area in New Mexico. Improvement
is forecast for the remaining drought areas across eastern New Mexico.
Forecast confidence for New Mexico is high.
Although fall storms begin to affect the Pacific Northwest by late in the period,
rainfall does not usually increase in California until later in the fall and
winter. Therefore, climatology favors drought persistence across California and
Nevada. Persistence is also forecast across interior Washington and Montana.
Forecast confidence for the West is high.
With neither the CPC monthly or seasonal outlooks showing below median rainfall,
the previous outlook forecasting improvement remains most likely for the small area of drought in southeast Alaska.
Forecast confidence for southeast Alaska is moderate.
Some improvement is forecast for eastern Maui in association with trade wind
showers. Long-range forecasts are uncertain and the previous forecast for
persistence and development will continue for the remainder of the Hawaiian
Islands. At this time, Hurricane Carlos is forecast to pass south of Hawaii.
Forecast confidence for Hawaii is moderate.