Southwest Climate Outlook September 2013

Date issued

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.

Published by the Climate Assessment for the Southwest (CLIMAS), with support from University of Arizona Cooperative Extension, the Arizona State Climate Office, and the New Mexico State Climate office.

Disclaimer. This packet contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials. The user assumes the entire risk related to the use of this data. CLIMAS, UA Cooperative Extension, and the State Climate Office at Arizona State University (ASU) disclaim any and all warranties, whether expressed or implied, including (without limitation) any implied warranties of merchantability or fitness for a particular purpose. In no event will CLIMAS, UA Cooperative Extension, and the State Climate Office at ASU or The University of Arizona be liable to you or to any third party for any direct, indirect, incidental, consequential, special or exemplary damages or lost profit resulting from any use or misuse of this data.