Tools used in the Drought Outlook included the
official CPC precipitation outlook for July 2009 and the long lead forecast for July – September 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 July–September, climatology, and initial conditions
In the upper Mississippi Valley, drought has expanded west during the late
spring, while drought persists in parts of Wisconsin. Little or no drought
relief is expected during the short and medium range. Watersheds in east central
Minnesota and west central Wisconsin are running much below normal. El Niño
composites for July-September along with the CFS seasonal precipitation forecast
indicate a tilt in the odds for above median precipitation. Some improvement is
forecast since long-term indicators are optimistic for improvement but the
hydrological drought should persist into September.
Forecast confidence for Wisconsin and Minnesota is moderate.
During June, drought was eliminated in far west Texas and the severity and areal
coverage of the drought has been reduced in northwest Texas. During the past 2-3
days, scattered showers and thundershowers with local amounts exceeding 3 inches,
per radar estimates, have occurred in northwest Texas. With the recent rainfall
and mixed signals from the various tools, some improvement is forecast in
northwest Texas. Meanwhile, severe to exceptional drought persists in central
and south Texas. Since most tools on all time scales favor below median
precipitation, drought should persist across much of central and south Texas.
Forecast confidence for northwest, central, and south Texas is high.
A recent heat wave coupled with much below normal rainfall has resulted in the
expansion of drought into southeast Texas and Louisiana. From May 1, 2009 – June
28, 2009, Houston received only 0.65 inches of rainfall, 7 percent of normal for
that time period. On June 24 and 26, Houston measured high temperatures of 104
degrees which is the highest temperature on record during June. Record heat has
also affected Louisiana. With the 6-10 and week 2 forecasts calling for above
normal temperatures and below median precipitation, drought persistence and
development are forecast in southeast Texas and southern Louisiana. With a wet
climatology and potential for tropical systems, drought development across the
western Gulf coast region is a risky forecast. Following expected development in
the medium-range, drought amelioration is possible later in the summer.
Forecast confidence for southeast Texas and Louisiana is low.
A relatively dry climatology favors persistence in central Oklahoma, while odds
for improvement increase for drought areas in the Oklahoma panhandle and
Nebraska. The 5-day precipitation forecast from HPC as of July 1 indicates more
than 1 inch of rainfall in these areas. In addition, the updated CPC July
outlook calls for enhanced chances for above median precipitation. However, hot
temperatures and high evapotranspiration rates may offset beneficial rainfall.
Therefore, some improvement is forecast in the Oklahoma panhandle. Higher normal
rainfall amounts during the July-September period favor improvement across
Forecast confidence for Oklahoma and Nebraska is moderate.
Prospects for improvement in Arizona and New Mexico remain high. During the next
few days, model guidance indicates that a continued surge of monsoon moisture
should result in frequent showers and thundershowers with locally heavy amounts.
The southwest monsoon typically reaches its peak intensity during August. The
CPC July-September outlook calls for enhanced odds for above median
precipitation across the southwest.
Forecast confidence for the Arizona and New Mexico is high.
Climatology favors drought persistence across California and Nevada. Persistence
is also forecast across Montana where the CPC July and July-September outlooks
favor dryness. With the CPC July-September outlooks calling for enhanced odds
for below median precipitation and above normal temperatures, development is
forecast across inland areas of Washington that are currently experiencing
abnormal dryness as indicated on the Drought Monitor.
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.
In Hawaii, the forecast indicates improvement for eastern parts of the Big
Island and some improvement for eastern Maui where trade wind showers have
occurred recently. Long-range forecasts are uncertain and the previous forecast
for persistence and development will continue for the remainder of the Hawaiian
Forecast confidence for Hawaii is moderate.