December 2009 - February 2010

Outlook Graphic: GIF   PDF 

Latest Seasonal Assessment - After a brief period of tranquil weather during early November, abundant moisture from the remnants of Hurricane Ida, coupled with a developing Nor’easter and a stationary front, dropped heavy rains on most of the Southeast, alleviating drought in the Carolinas. Florida was an exception where significant rains bypassed the southern two-thirds of the State, and moderate drought developed in east-central Florida. Light to moderate showers in the upper Midwest erased moderate drought in northern Minnesota, but drier weather to the south maintained drought across northern Wisconsin. Light rain also fell across south-central Texas, but amounts were insufficient for any significant improvement. Although the Pacific Northwest observed stormy weather, areas to the south were left mostly dry, with drought expanding into southern Nevada. The outlook for December 2009 through February 2010 continues to indicate drought improvement for California, southern Arizona, southern Texas, and Florida. The current moderate El Niño is expected to last through this winter, increasing the odds toward improvement in the aforementioned areas. Ongoing drought with some improvement is forecast for the remainder of the Southwest (southeastern California, central and northern Arizona, Nevada, and the Four Corners Region). In contrast, drought should persist in northern Wisconsin and north-central Washington, and slightly expand eastward into the northern Rockies. During El Niño events, the odds favor subnormal winter rainfall across the Hawaiian Islands which should cause worsening conditions for the existing drought regions, and possible drought development over areas that are currently drought free.

Tools used in the Drought Outlook included the official CPC precipitation outlook for December 2009 and the long lead forecast for December 2009 - February 2010, 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 December - February, climatology, and initial conditions.

Short-term dryness has led to drought development in east-central parts of the Florida peninsula. Since October 1, the rainfall deficit at Melbourne, FL is nearly 6 inches. Although drought conditions may expand across the Florida peninsula during the next few weeks, the ongoing El Niño strongly favors above-median precipitation during the winter and thus improvement in the long-term.
Forecast confidence for Florida is high.

Drought coverage and intensity has decreased in the upper Mississippi Valley, but severe drought continues in northwest Wisconsin. Due to a lack of any forecast signals for wetter than normal conditions and a relatively dry climatology during the outlook period, drought is expected to persist. Precipitation for this region typically increases later in the spring.
Forecast confidence for Wisconsin is low.

Additional relief from the protracted drought affecting parts of southern Texas appears likely during the winter. Forecasts from December through the end of February favor above-median precipitation, and the development of moderate El Niño conditions also favors enhanced precipitation during the outlook period.
Forecast confidence for Texas is high.

Recent short-term dryness has worsened the drought in the Southwest, especially in Arizona. Little or no change can be expected during the remainder of November. El Niño composites indicate a tilt in the odds toward above-median precipitation during the outlook period. The CPC seasonal forecast shows slightly increased odds for above-median precipitation for southern Arizona but equal chances for above, below, or near normal precipitation across the reminder of the State. With these considerations, improvement is more likely in southern Arizona.
Forecast confidence for the Four Corners region is moderate.

Since October 13 when a very strong storm affected northern and central California, drier than normal conditions have prevailed across the state. At the beginning of the outlook period, moist onshore winds should bring several inches of precipitation to northern California. By the end of November, enhanced rainfall associated with a MJO event is expected to become established across the western pacific. This MJO activity may affect the circulation pattern across the north Pacific and contribute to wet conditions along the West Coast. Later in the winter, the storm track is expected to gradually shift south along the West Coast. El Niño composites along with the CPC seasonal outlook favor above-median precipitation during December – February. Therefore, improvement is forecast in California.
Forecast confidence for California is high.

Although the short-term forecast is quite wet across central Washington, the CPC seasonal forecast indicates higher odds for below-median precipitation. Drought persistence and development is forecast in central and eastern Washington.
Forecast confidence for Washington is low.

Hawaii is forecast to receive below-median rainfall during the upcoming winter, consistent with an ongoing El Niño. Drier than normal conditions will worsen existing severe to extreme drought and likely result in drought expansion across the remainder of the state.
Forecast confidence for Hawaii is moderate.