December 1st – 16th: The tail end of a low pressure system swept down from the Pacific Northwest over the first week of the month bringing a little rain and snow to Arizona. Totals were quite low because there was not a lot of moisture to work with. On the 3rd, Tucson received 0.12″ of rain and Phoenix received a trace of rainfall by the 4th.
On the 5th precipitation was more widespread, but the most was 0.49″ at Saint Johns, and 0.35″ at Cast Hot Springs. Flagstaff received no precipitation from this system. Dry conditions followed with no further precipitation until the 15th, when a small upper level disturbance moved and tapped into a little moisture, with Flagstaff receiving about 0.06″. Also on the 16th, Flagstaff recorded their peak wind gust for the month at 42 mph. Phoenix and Tucson were able to set/tie old HiMin records. On the 13th, a new HiMin record was set at 69 degrees from 67 degrees in 1983 for Phoenix. Tucson set a new HiMin at 63 degrees from 60 degrees in 1990. In Phoenix on the 14th, the old HiMin record of 63 degrees from 1990 was tied as well as the HiMin for the 15th which was tied at 62 degrees. Tucson tied another HiMin record of 60 degrees on the 16th which was originally set in 1936. The warm nighttime temperatures were the result of very warm daytime temperatures followed by nighttime cloud cover that trapped the heat below the clouds.
December 17th – 31
st: The beginning of the third week of December started off with relatively fair weather conditions due to a more zonal flow of the jet stream. However, as the week progressed, gradients within the main flow became tighter creating stronger jet maximums and the flow became more meridional. A well-defined low pressure system made its way into the southwest creating uplift for the moisture that was pumped up from the Pacific Ocean. The available moisture was significant and the storm moved very slowly, so rain and snowfall totals were quite high. On the 22nd, Flagstaff received 1.01″ of precipitation, a new record, and Phoenix reported 1.60″ of precipitation, also a new record. Additionally, Phoenix received 0.42″ of precipitation the previous day which set a new record, beating the original record of 0.24″ in 1963. Tucson received 0.87″ on the 22nd, but 1.21″ the following day. No additional records were set or tied for Tucson. On the 22nd, Flagstaff set a new snowfall record of 5.6″, breaking the previous record of 5″ in 1902.
In This Issue: Overview of December, graphs of the December daily maximum and minimum temperatures, precipitation, mean daily dew points for Flagstaff, Phoenix, and Tucson; December climate statistics, maps of mean monthly maximum and minimum temperatures, precipitation, dew points, wind speeds for December; and graphs of the
mean December temperature and precipitation for the period of record for Tucson, Phoenix, and Flagstaff, graphs of the cumulative precipitation for the calendar year for Flagstaff, Phoenix, and Tucson. Climate calendars for Flagstaff, Phoenix, Tucson, Prescott, Winslow and Yuma, including daily and monthly normals and extremes, for each month of
the year, can be downloaded directly from the State Climate website. See p. 19 of this report for calendar abbreviations. Data are preliminary and are from the National Weather Service Forecast Offices in Flagstaff, Phoenix and Tucson. **Note: The discrepancy between the Statewide Temperature and Precipitation values for Phoenix, Flagstaff and
Tucson and the daily values in their graphs are due to the reporting times. Statewide Temperature and Precipitation values are taken at 5pm, while official daily records at the airports are taken from Midnight to Midnight.