Southwest Climate Outlook Tropical Storm Tracker - October 2018

Atlantic hurricanes Florence and Michael have understandably been the focus of attention this year, but as discussed on page 1, 2018 has been an extremely active year for tropical storms in the eastern North Pacific. While most of the storms expended most or all of their energy over the Pacific, a few had notable impacts on the Southwest.

In mid-June, Tropical Storm Bud caused widespread precipitation across the Southwest just as the monsoon began, kickstarting cumulative monsoon precipitation totals, even as some argued it should not be included as part of the monsoon* (Fig. 1). In September, Tropical depression Nineteen-E brought widespread precipitation to the Southwest (Fig. 2) and was a major contributor to that month’s above-normal precipitation (see Fig. 5 on the Maps & Images page). October has seen two events (thus far) of notably different character. Tropical Storm Rosa brought intense precipitation to the borderlands region of Arizona and up to Phoenix (Fig. 3) at the beginning of the month, resulting in severe flooding in both regions, and one week later, Tropical Storm Sergio brought more widespread but less-intense precipitation to southern Arizona and parts of New Mexico (Fig. 4).

With an official end to the season not until Nov. 30, it remains to be seen how many more tropical storms might bring additional rainfall to the Southwest this fall.

Figures 1-4 - CLIMAS: Climate Assessment for the Southwest - climas.arizona.edu

Data: prism.nacse.org