precipitation

CLIMAS and Arizona Cooperative Extension will host an online climate briefing about the 2009 monsoon for natural resource managers, extension faculty, and interested citizens on May 21 at 10:00 a.m. PDT. Colleagues from northern Mexico are especially invited to participate, as forecasts will cover the U.S.-Mexico border region.

Average monsoon precipitation (June 15 through September 31) since 1895 for Tucson and 1896 for Phoenix. This data was obtained from the National Weather Service in Tucson.

The data for Arizona was obtained from the NWS Tucson; New Mexico data was compiled from the Western Regional Climate Center.

During El Niño years, all climate divisions in Arizona and New Mexico tend to receive above-average winter precipitation. Values represent the percentage of December-March precipitation compared to non-El Niño years for the period 1895-1996.

Trends in the frequency of precipitation events in which precipitation over a 7-day duration exceeds a 1-year recurrence interval for each particular climate division. Blue circles are positive trends, red circles are negative trends. The magnitude of the trend is linearly proportional to the radius of the circle.

Snow monitoring sites in the Western U.S. with at least 20 years of data. Additional sites with less data are not displayed.

Meteorological and climatological flood-producing events operate at varying temporal and spatial scales.

The map shows the mean calendar date of monsoon onset, based on the time frame 1963–1988. Onset definitions vary depending on region because of differences in rainfall regimes. Although average onset date may change slightly if different time frames are used, the relative timing of the northward progression of the monsoon should remain intact.