July - September 2009

Outlook Graphic: GIF   PDF 

Latest Seasonal Assessment - During June, a heat wave combined with much below normal rainfall has resulted in drought expansion across southeast Texas and Louisiana. Due in part to a forecast of above normal temperatures and below-median precipitation during the next two weeks, drought should persist or expand further across the western Gulf Coast region. Odds for improvement increase across northwest Texas, the Oklahoma Panhandle, and southern Nebraska, while drought should persist across central Oklahoma. The southwest monsoon that typically peaks during August should result in improvement across southeast Arizona and New Mexico. Some improvement is forecast across Minnesota and Wisconsin, but hydrological impacts should continue into September. Climatology favors drought persistence across the West. Enhanced odds for below-median precipitation and above normal temperatures across the Pacific Northwest from July-September should lead to drought development across inland Washington. Persistence is expected across Montana. Improvement is forecast across the eastern slopes of the Hawaii’s Big Island with drought persistence or development forecast for the remainder of the Hawaiian Islands.

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 southern Nebraska.
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 Islands.
Forecast confidence for Hawaii is moderate.