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September 2013 Southwest Climate Outlook
Published September 25, 2013
Drought: Another wet month across much of the Southwest has led to substantial improvements in short-term drought conditions.
Temperature: The last 30 days were generally warmer than average and the summer is turning out to be one of the warmest on record in many areas.
Precipitation: Subtropical moisture drenched New Mexico on its way to Colorado in recent weeks, and most of the Southwest has benefitted from an active monsoon.
ENSO: ENSO-neutral conditions are expected to persist through the fall season and most likely through next winter and spring.
Forecasts: Outlooks call for enhanced chances for above-average temperatures and below-average precipitation through the winter; both are based, in part, on long-term trends.
Climate Snapshot: The monsoon officially ends on September 30, but for all intents and purposes its last gasp has already passed. Atmospheric circulation is now drawing dry air from the West. In coming weeks, some southerly moisture may be sucked from the south as if the monsoon were revving back up, but these intermittent episodes are common in this monsoon-winter transition period. There is no reason, however, to lament the ending of the monsoon. It delivered enough storms to much of the Southwest to drive precipitation to above-average levels for only the fifth time since 2000. The rain has dramatically improved drought conditions, particularly by reducing acute short-term drought. At the start of the monsoon on June 18, nearly 90 percent of New Mexico and 22 percent of Arizona were classified with extreme or exceptional drought. Now, about 6 and 2 percent of New Mexico and Arizona, respectively, are classified with extreme and exceptional drought. There is some indication that this winter will deliver below-average rain and snow, however. These outlooks are based on long-term drying trends but are far from conclusive. Without a strong signal from the El Niño-Southern Oscillation—the climatologist’s best statistical tool for seasonal forecasts uncertainty is high. ENSO-neutral conditions often do not steer the jet stream, which ferries storms into the region, to either a more northerly or southern trajectory like La Niña and El Niño events do. There is, however, more certainty that temperatures will be above average in coming months, based, at least in part, on long-term trends that are evident at many spatial scales.
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, Managing Editor, CLIMAS Associate Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Dollin, CLIMAS Publications Assistant
- Dave Dubois, New Mexico State Climatologist
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
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