August - October 2009

Outlook Graphic: GIF   PDF 

Latest Seasonal Assessment - Hot temperatures combined with below-normal rainfall have resulted in drought expansion across the western Gulf region while an exceptional drought continues in south Texas. Drought is forecast to persist across south Texas, but short- term improvement is likely in the lower Mississippi Valley. It should be noted that the arrival of El Niño could bring relief to the Texas drought later in the fall and winter. The southwest monsoon that typically peaks during August should result in improvement across eastern New Mexico. Improvement is also forecast for drought areas across southern Nebraska and Oklahoma where much needed rainfall and cooler temperatures are expected during the remainder of July. Some improvement is forecast across the upper Midwest. Although not depicted on the map, eastern Ohio should be closely monitored for drought development. Climatology favors persistence across California and Nevada. Persistence is also forecast across interior Washington and Montana. Improvement can be expected in southeast Alaska. Improvement has recently occurred along the eastern slopes of Hawaii’s Big Island, but drought persistence or development is forecast for the remainder of the Hawaiian Islands.

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.