Wednesday, August 01, 2018

July Summary

Even though PW and surface dewpoints were high for most of month, here at house the July rainfall was the third lowest amount in my records. The driest four years here have been (since 1999): 2000 - 0.49"; 2015 - 0.60"; 2018 - 0.62"; and 2013 - 0.83. In contrast, the wettest four years here have been: 1999 - 6.63"; 2017 - 5.85"; 2007 - 4.94"; and 2006 - 4.85".

Measurable rain fell on 8 days - BUT the greatest amount was only 0.20" on the 15th.

There were thunderstorms on at least 10 days - but because of my hearing situation, there could have been other thunder days. Katie lets me know when she hears thunder, but I'm often here with no hearing help.

There was one severe thunderstorm with strong wind gusts on the 5th.

All-in-all a pretty dismal month, especially given the generally moist and unstable conditions that prevailed.

Here are the monthly totals from the Pima County ALERT network (north half above). Most amounts at low elevations were between 1 and 2 inches. However, there were 12 sites with less than inch (these were clustered in central and north metro areas). One site reported less than half an inch. Amounts of over four inches were confined to the Catalinas, with the exception of the heavy rains that occurred near and west of Oro Valley.

The south half of network (below) generally reported monthly accumulations of one and a half inches to around three and a half inches.

Finally, the average daily dewpoints (below from NWS) were above the old monsoon threshold of 54 F for every day after July 8, except for two. I did check the average winds for every TWC sounding for the month to determine on how many days monsoonal winds occurred. I considered average directions from 090 to 210 degrees for the layer 700 to 400 mb as "monsoonal flow." Only half the days of the month had winds that met these simple monsoonal flow criteria, reflecting the fact that the anticyclone shifts around, and that even once in a while a westerly trough reaches this far south.

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