Southwest Climate Outlook Monsoon Tracker - October 2018

The precipitation rankings for the months that encompass the monsoon period (see Fig. 3 on p. 2) smooth out the variability over space and time that is characteristic of this season. The cumulative totals for the monsoon for most of the major metropolitan areas in the region (Fig. 1) came in at or above average, with the exception of El Paso.

Monthly rankings show that June—which is typically dry, often with little actual precipitation at all in the Southwest—was wetter than normal across much of the borderlands region of Arizona and New Mexico (Fig. 2). This was almost entirely due to Tropical Storm Bud, which brought rain to the area in mid-June. Widespread precipitation occurred across the Southwest in July, and while a few areas only received below-normal precipitation, most of the region was at or above normal for the month (Fig. 3). August flipped that script, and while there were wide swaths of Arizona and New Mexico that received average to above-average rainfall, south-central New Mexico, parts of southern Arizona, and the Four Corners region in particular, lagged behind (Fig. 4). In September, southeastern Arizona and the lower two-thirds of New Mexico received average to above-average precipitation, but this was largely due to the incursion of tropical moisture in the latter half of the month. Outside that area, the region was generally devoid of widespread precipitation, with the Four Corners region continuing to be the epicenter of below-average to record-driest conditions (Fig. 5).

Monsoon totals (Figs. 6a-b on p. 5) demonstrate the range of precipitation across the two-state region. Percent of normal precipitation (Figs. 7a-b) and percent of days with rain (Figs. 8a-b) describe aspects of the monsoon that shape local perceptions of the monsoon’s performance (i.e. how much compared to normal, and whether rain fell in just a few intense days or over many less intense days).

Online Resources

• Figure 1 - CLIMAS: Climate Assessment for the Southwest - climas.arizona.edu
  • Figure 1 Data: wrh.noaa.gov/twc/monsoon/monsoon_elp.php
• Figures 2-5 - Western Regional Climate Center - wrcc.dri.edu
• Figures 6-8 - UA Climate Science Application Program - cals.arizona.edu/climate