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Arizona Reservoir Volumes

New Mexico Reservoir Volumes

The official start date of the monsoon (June 15) was overshadowed by a Southwest-wide extreme heatwave that set numerous records. Heatwaves in June are a typical feature of the seasonal climate, especially as the subtropical ridge builds north, but these record temperatures also increased the anticipation for the relief that the monsoon can provide. Much of southern and central Arizona have recorded pockets of above-average precipitation, while New Mexico has seen more widely distributed precipitation since June 15 (Fig. 1a-b). (read more)

Precipitation and Temperature: June precipitation ranged from record driest to near average in Arizona, while in New Mexico, precipitation ranged from much-below to much-above average (Fig. 1a). This difference reflects the seasonal progression of monsoon activity in the Southwest—it typically starts earlier in New Mexico and progresses westward—as well as the relatively late start to monsoon activity observed in much of Arizona this year. June temperatures ranged from much-above average to record warmest in Arizona and from above average to much-above average in New Mexico (Fig. 1b). A region-wide heat wave that struck in mid-to-late June helped drag up the averages, setting a number of daily high records across Arizona. Year-to-date precipitation ranks reveal average to above-average precipitation in all of New Mexico and much of Arizona, with a pocket of below-average precipitation in southeast Arizona (Fig. 2a). Year-to-date temperatures reveal much-above-average to record-warmest conditions in both Arizona and New Mexico (Fig. 2b).(read more)

In 2008, the National Weather Service changed the definition of the start of the Southwest monsoon from a variable date based on locally measured conditions to a fixed date of June 15. Prior to 2008, the start date reflected the seasonal progression of the monsoon (Fig. 1). This is based on larger seasonal atmospheric patterns and the establishment of the ‘monsoon ridge’ in the Southwest (Figs. 3a-b, also see sidebar for link to NWS pages).

In Southern Arizona, the start date was based on the average daily dewpoint temperature. Phoenix and Tucson NWS offices used the criteria of three consecutive days of daily average dewpoint temperature above a threshold (55 degrees in Phoenix, 54 degrees in Tucson) to define the start date of the monsoon. As shown in Figure 2, the dewpoint temperature criterion produced start dates ranging from mid-June to late July over the period of record (1949-2016). The average daily dewpoint temperature is still a useful tool to track the onset and progression of conditions that favor monsoon events, and the National Weather Service includes a dewpoint tracker in their suite of monsoon tools. (read more)

Precipitation & Temperature: May precipitation was variable across the Southwest, ranging from average to much-above average in Arizona and below to above average in New Mexico (Fig. 1a). Similarly, May temperatures were average to above average across Arizona and ranged from below to above average in New Mexico (Fig. 1b). Taking a longer view, spring (March-May) precipitation was mostly below average in Arizona, while New Mexico ranged from below average in the southwestern region to above average in the northeast (Fig. 2a). Spring temperatures were much-above average across most of the Southwest (Fig. 2b). So far in June, temperatures have ranged from 0 to 8 degrees above normal across much of Arizona and New Mexico, with extreme heat forecast for the week of June 19. June precipitation has been sparse in most of Arizona, with infrequent storm activity mostly in southern and eastern New Mexico. (read more)