The Week of Great Storms

The past several days have been so unusual, with such heavy precipitation and flooding, that I have been unable to do much except try to save data files and images so that, eventually, I can do careful analyses of the events.

There were significant MCSs over Arizona from the 25/26 through the 30/31. On some days there were MCSs early over the mountains and then later over lower elevations.

The episode began with a great northward push of low-level moisture into the state that was triggered by TS Emilia moving through the favored area southwest of Baja (see earlier post). I had anticipated this surge would reach Arizona 12 to 18 hours earlier than it did. I put too much confidence in the early track forecasts of NHC, which were too fast. Art Douglas warned me that he didn't think the TS would move northward as fast as the early NHC forecasts indicated and he was correct.

The first MCS event occurred during the night of the 25th (26th UTC time - note that Arizona is on MST and that midnight is 0700 UTC). An earlier post covers this first event in some detail.

Satellite IR images are shown for UTC times on the 26th through the 1st of August.

CLICK HERE for Figures 1 -8

As the week progressed, the large-scale pattern evolved from one dominated by a large, middle-level anticyclone over the west, i.e., a fairly typical July setting into one with a cyclone and several associated short-waves spinning over northeast Arizona and western New Mexico, remaining nearly stationary for a couple of days.

MCSs during the period first moved toward the west-southwest, and then toward the south, and eventually toward the southeast.

The rain events measured at our house are shown below - and, for a larger perspective total CG counts over the Arizona domain (domain has been shown in earlier posts). My 24-h rain measurements were taken around 1300 UTC each day and the 24-h CG counts ended at 1200 UTC each day.

Date / Rain Total / AZ CGs

7-26 / 0.14" / 36,256
7-27 / 0.17" / 26,696
7-28 / 0.39" / 14,614
7-29 / 1.64" / 25,047
7-30 / 0.40" / 10,013
7-31 / 1.39" / 14,907
8-01 / 0.15" / 5,652

Total rain measured here at the house was 4.19"! The most unusual aspect of these heavy rains, at least here locally, was that approximately 80% of the rain occurred between 2 am and 8 am local time. Thus, events in southeast Arizona for the week considered were mostly nocturnal and more like the summer rainfall climatology of Omaha than of Tucson.

More will follow.