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Published September 23, 2010
Seasonal Drought Outlook(through December)
Data Source(s): NOAA-Climate Prediction Center (CPC)
This summary is excerpted and edited from the Aug 16 Seasonal Drought Outlook technical discussion produced by the NOAA–Climate Prediction Center and written by forecaster A. Allgood.
In the Southwest, drought persistence is forecast for northern Arizona, with drought development likely in areas already experiencing abnormal dryness. Many forecast models, including the 6-10 day and 8-14 day (Figure 11) forecasts, the October monthly forecast, and the October–December seasonal forecasts, all favor drier conditions across much of the Southwest, and confidence in this forecast is high. Below-average precipitation in the past two weeks and a mounting la Niña event play a large role in this forecast. La Niña events often bring dry weather to the Southwest. Since 1950, the southwestern U.S. and particularly Arizona have been drier than average between 60 and 80 percent of the time. Currently, the strength of the La Niña event is moderate to strong, and it is expected to persist into next year.
Elsewhere in the West, drought conditions have persisted across the Great Basin and parts of the northern Rockies region throughout the summer dry season. As winter approaches, the La Niña event will likely shift storm tracks into the Pacific Northwest, bringing increased precipitation to the region. The region of increased precipitation can extend as far south as northern California, but a sharp gradient exists between the enhanced precipitation in the Northwest and the typically drier Southwest during a La Niña event. Due to the high likelihood of elevated precipitation across the Pacific Northwest, drought improvement is forecast for southern Oregon, while some improvement is indicated for northern California and far northwestern Nevada. Persistence is forecast for the remainder of the Great Basin, as the La Niña climate anomalies are drier towards the south. Confidence is this forecast is high for the northern Great Basin.
The delineated areas in the Seasonal Drought Outlook are defined subjectively and are based on expert assessment of numerous indicators, including the official precipitation outlooks, various medium- and short-range forecasts , models such as the 6-10 day and 8-14 day forecasts, soil moisture tools, and climatology.
For more information, visit:
For medium- and short-range forecasts, visit:
For soil moisture tools, visit:
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Dan Ferguson, CLIMAS Program Director
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, CLIMAS Associate Staff Scientist
- Gigi Owen, CLIMAS Assistant Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Swetish, CLIMAS Publications Assistant
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
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