November 2007 - January 2008

Latest Seasonal Assessment - With the intensification and expected persistence of La Niña conditions through January, the current Drought Outlook leaned heavily on precipitation anomalies that typically occur during La Niña episodes. In addition, the latest official forecasts through mid-November, the official November and November-January outlooks from the Climate Prediction Center, climatological considerations, and how firmly entrenched current drought conditions are were all considered. The resulting forecast calls for drought persistence or development along most of the Gulf Coast and the southern half of the Atlantic Coast, save southern Florida. Some improvement is anticipated farther inland across the upper South, and improvement is expected for the Great Lakes region and the Northeast. To the West, the northern Plains and the northern and central portions of the Rockies, Intermountain West, and West Coast all should see some improvement by the end of January. In Contrast, drought persistence or intensification is likely in the Southwest and adjacent southern Rockies while drought should expand eastward through much of the southern Rockies and southern High Plains by the end of January. Limited improvement is anticipated between the areas of persistence and improvement in the West. Finally, improvement is forecast for the drought areas in Hawaii

Tools used in the Drought Outlook included the official CPC long-lead precipitation outlook for November - January 2007/08, the four-month 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 moisture, and the CFS monthly precipitation forecasts.

With the recent intensification of below-normal sea surface temperatures across the central and eastern equatorial Pacific Ocean, and the expectation that these La Niña conditions should persist through January, emphasis was placed on historic La Niña composites (both raw and adjusted toward recent decadal trends). Still, a great reliance was also placed on the official 5-day, 6- to 10-day, 8- to 14-day, November, and November - January outlooks (the latter of which also relied heavily on La Niña composites), adjusted for considerations related to how typically wet or dry this season is compared to other times of the year, how firmly entrenched drought conditions are, and the seasonal decline in water loss due to declining temperatures, decreased evapotranspirative losses, and reduced public water usage.

Near the Gulf and Atlantic Coasts in the southern half of the country, drought persistence or development should be widespread with La Niña conditions typically bringing subnormal precipitation to the region during the forecast time period. In addition, many of the areas forecast for development have experienced some degree of dryness recently if not full-fledged drought conditions, and thus may be more sensitive to potential dryness than would normally be the case. South Florida could also be added to this discussion, but potential rainfall from Tropical Storm Noel, as well as a forecast that favors surplus precipitation into mid-November and the possibility for additional tropical activity, have led to its exclusion from a forecast of drought developement for the time being.

Well inland, across the upper South, La Niña tends to be more generous with precipitation, so despite a dry forecast for the next couple of weeks, some improvement is expected in this region.

To the north, the next couple of weeks look wet in the Great Lakes and Northeast, and with longer-range outlooks being non-committal, some improvement was forecast for this region.

Out West, La Niña tends to favor surplus precipitation for much of the central and northern Rockies and the northern half or so of the West Coast. Official long-term forecasts agree with this scenario, as do shorter-term outlooks for the northern Plains and Rockies. Thus, a large area of improvement was forecast for these regions, with lesser improvement anticipated in areas bordering these to the south, including the lower northern High Plains.

All forecasts on all time scales essentially agree on subnormal precipitation in the Southwest, where drought persistence or deterioration is anticipated. For southern sections of the Rockies and High Plains not already experiencing drought but beginning to feel the effects of short-term precipitation deficits, drought developement probabilities are enhanced, as reflected in the forecast. This includes regions in the southern High Plains currently in the 'abnormally dry' category as depicted by the Drought Monitor.

Finally, with Hawaii progressing into its wetter time of the year, and with La Niña composites favoring above-normal precipitation, improvement was forecast for drought-affected areas across the island chain.