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
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
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.