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SW Climate Outlook - Monsoon Case Study - Tucson July 2017

Tuesday, July 25, 2017

The onset of monsoon activity seemed to arrive late in Tucson this year, although residents have been rewarded for their patience by a surge of almost daily storms in the region since July 10. Coincidentally, July 10 was also the third straight day of average daily dewpoint temperatures at or above 54 degrees, thereby meeting the monsoon threshold used by NWS Tucson prior to 2008. The average start date by the former definition is around July 3, although in 2015 and 2016 Tucson met this threshold on June 25. By the dewpoint criteria—and given the absence of any measurable precipitation in Tucson in June and early July, the monsoon did start late, but as was discussed in the most recent episode of the CLIMAS Southwest Climate Podcast, the relatively short length of the monsoon and the desire for relief from the extreme heat of June means any delay to the onset feels like an eternity, even if the first big storm day is only a few days or a week after we might normally expect it. (read more)

SW Climate Outlook - Monsoon Tracker - July 2017

Monday, July 24, 2017

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)

SW Climate Outlook - ENSO Tracker - July 2017

Friday, July 21, 2017

Oceanic and atmospheric indicators are still within the range of neutral (Figs. 1-2), although sea-surface temperatures have hinted at borderline El Niño conditions. Seasonal outlooks and forecasts generally agree that ENSO-neutral conditions are the most likely outcome for the remainder of 2017, albeit with a lingering possibility of an El Niño event by winter 2017-2018. (read more)

SW Climate Outlook July 2017 - Climate Summary

Thursday, July 20, 2017

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)

Extreme Heat in the Southwest - June 19, 2017

Monday, June 19, 2017

At the time of publication (Jun 15, 2017), an extreme heatwave is forecast to hit the Southwest beginning later this week and extending into next week the week of June 19, peaking on/around June 19-20, 2017. Tucson is currently forecast to reach 114, while Phoenix may see temperatures reach 120 – both of which are approaching the record high temperatures for Tucson and Phoenix, respectively. Southwestern summers have a well-earned reputation for extreme temperatures, and compared to most of the country, even a ‘normal’ summer day is often much warmer than record high temperatures in more temperate locales. The Phoenix NWS office is piloting an experimental heat extremes tracker/map that highlights the risk potential associated with direct exposure and more sustained heat events. (Figs. 1a-ab). (read more)

CLIMAS SW Monsoon Outlook - June 2017

Friday, June 16, 2017

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)

CLIMAS SW Climate Outlook - ENSO Tracker June 2017

Friday, June 16, 2017

Oceanic and atmospheric indicators of the El Niño-Southern Oscillation (ENSO) are still within the range of neutral (Figs. 1-2), although sea-surface temperatures more consistently hint at borderline El Niño conditions compared to atmospheric indicators. Outlooks and forecasts generally agree that ENSO-neutral conditions will persist through the summer and is the most likely scenario for the rest of 2017. A lingering possibility remains of an El Nino event developing later this fall, but forecasts since last month have shifted further from that likelihood. (read more)

 

Southwest Climate Outlook June 2017 - Climate Summary

Thursday, June 15, 2017

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)

CLIMAS SW Climate Outlook - Wildfire Report: Sawmill Fire

Friday, May 19, 2017

The Sawmill fire (Fig. 1) started, reportedly by recreational shooting, on April 23, 2017 in a grass- and shrub-covered area of low-elevation Arizona state lands approximately 40 miles south of Tucson. The fire spread quickly due to dry and windy conditions that day: the temperature reached 98 degrees, relative humidity ranged between 4 and 18 percent, and sustained winds reached 20 mph with gusts up to 30 mph. High winds, high temperatures, and low relative humidity continued through much of the following week, driving rapid growth of the fire (Fig. 2). (read more)

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