Special Weather Statement
Dept Atmospheric and Oceanic Sciences UCLA
3:55 PM PDT Thursday 02 August 2011

This July was slightly wetter than normal. A total of 0.03 inch rain
fell for the month(same total as two years ago). Normal July rainfall
(defined by a 30 year mean) is just 0.02 inch. However, many Julys
can pass without any rain at all(median rainfall is zero). Thus, this
month's total still ranked it tied for the 5th wettest July on record
(first time in 1935 and repeated in 1986 and 2010). Normally, one
measurable rain day occurs every other year. The two rain days this
month fell one day short of the record for measurable rain days in July.
The first rain event of the month started on the 12th. Some sprinkles began
in the mid-afternoon hours. No qualified trace amount was recorded for the
12th(using Greenwich Mean Time convention). Rain was most steady in the
early evening(no further showers remainder of the local calendar day).
A few more showers fell in the wee early hours of the 13th. The day recorded
0.02 inch rain. That set a record rainfall for the date(previously a trace
amount in 1953,1954,1973). The second and final rain event of the month
occurred on the 18th, local calendar-wise(rainfall recorded on the 19th,
GMT-wise). Like the previous event, sprinkles started mid-afternoon.
Showers increased in frequency in the evening hours though only the last
one produced measurable rain(late evening). A thunderstorm was reported near
the campus late in the 7 PM hour(loud clap of thunder reported once). The
0.01 inch rain for the 19th was enough to set a record for the date(old
record was a trace amount in 1948,1985,1991).  

This July was much cooler than normal. The average temperature was 66.4 degrees.
That was three degrees lower than normal(coolest July since 1991). It ranked
tied for the 8th coolest July on record(first occurrence in 1948 and repeated
in 1956). The average maximum temperature was 73.3 degrees and the average
minimum was 59.5 degrees(3.8 degrees and 2.2 degrees below normal, respectively).
The average maximum ranked 7th coolest while the average minimum ranked 15th
coolest for July. Normally, a July would have one day reaching at least 90 degrees,
but none occurred this year. Three days warmed into the 80s(13th,19th,20th), but
that was five days less than normal for the month. Five days did not even reach
70 degrees(4th-7th,16th). That was four days more than normal. The highest
temperature in the month was 85 degrees(19th). The lowest temperature in the
month was 54 degrees(7th,8th). A number of temperature records for the date were
tied. Record low maximums were tied on the 5th(68 degrees also occurred in 1960
and 1962) and on the 26th(70 degrees also in 1979). Record minimums were tied on
the 7th(54 degrees also in 1962) and on the 28th(55 degrees also in 1932). 

An interesting temperature event occurred in the evening of the 12th. Convective
showers in the area apparently produced pockets of moderately, strong vertical 
mixing of the air. In between showers, the campus temperature rose as high as 74
degrees at 8:09 PM(unusually warm for early evening). Correspondingly, the dew
point temperature rose to 64 degrees(unusually high for the area). Just five minutes
later, the temperature fell back to 68 degrees. Alos, the barometric pressure rose two
millibars in just a 15 minute period(8:10-8:25 PM).

This month had one day where the campus visibility was estimated down to one mile or less.
On the 14th early morning fog may have briefly reduced the visibility to a mile(toward
the south).

No significant wind(at least 25 mph gusts) occurred this month. The highest measured
wind gust was 24 mph on the 12th(8:13 PM). Brisk easterly winds were prevalent only for
a short time(8:13-8:21 PM...gusts reaching at least 20 mph).  

J. Murakami

Rainfall in inches
24 hour rainfall measured from Midnight to Midnight, Greenwich Mean Time
Normals are defined using a 30 year mean from 1981-2010
UCLA records date back to 1932
All times given in Pacific Standard Time