DECEMBER 1999 Wx REVIEW
A very stagnant pattern for most of the month, with near record LOW rains
in many areas of the West, especially from SFO south. Pacifica received only
0.72", with the bulk (0.54) falling during a brief trough passage on the
9th. No appreciable rain has fallen since then. Mean temp for the month was
a warm 52.8F (normal is near 50F), and temperature records throughout the
month were set in many areas of the West. Monterey in fact, reported
8 days of 70+ temps immediately before Christmas..a new record for
December to be sure...and an unconfirmed record of the longest 70+ streak
for ANY time of the year. Here in Pacifica, we topped out at 69F on the 20th,
with a very warm stretch between the 18th and 22nd. Christmas was especially
pleasant, with temp at 64 under clear blue skies. The main pattern has been
a blocking high sitting off the West Coast and bridging with a strong Continental
high over the Big Basin. This creates a strong East-West pressure gradient
and a period of prolonged offshore winds (and Santa Ana's in SoCal). Locally,
E and NE winds over 50mph have been clocked over the East Bay hills....with
25mph wind from the NE on the 22nd here. Wildfires in SoCal have become a
problem in the tinder dry grasslands/hills. Because the winds were so dry,
no front stood a chance of penetrating to the coast...and what little energy
remained after slamming into the dry air mass, was shunted over top of the
Western states and channeled into the upper mid-west. The dry air
penetrated to tropical latitudes and the ITZ was unusually quiet.
Continuing the pattern for over a year now, no tropical or "pineapple" connection
took place, and unless the ridge is pressed much farther south than it's
current location, we should not expect one this Winter. This warm December
is somewhat similar to near record warmth we received last year in early
December. However in 1999, the end of December brought near record cold to
most of the West.. and this year brought only more warm weather. Curious
to see if January brings an unusually cold snap as so often happens after
a warm spell in La Nina years.
MONTHLY CLIMATOLOGICAL SUMMARY for DEC. 1999
Pacifica, Ca ELEV: 540' LAT: 37.36'N LONG: 122.27'W
TEMPERATURE (°F), RAIN (in), WIND SPEED (mph)
HEAT COOL AVG
MEAN DEG DEG WIND DOM
DAY TEMP HIGH TIME LOW TIME DAYS DAYS RAIN SPEED HIGH TIME DIR
------------------------------------------------------------------------------------
1 52.1 56.2 3:00p 48.3 9:00a 12.8 0.0 0.01 2.5 14.0 8:30p N
2 51.7 55.8 3:00p 47.5 12:00m 13.3 0.0 0.04 3.5 22.0 4:00p N
3 51.2 58.5 2:30p 44.7 2:30a 13.4 0.0 0.00 3.7 24.0 4:30a N
4 50.7 57.4 4:00p 46.9 7:30a 12.8 0.0 0.00 2.5 16.0 11:30a NNE
5 50.5 57.8 3:00p 44.1 7:30a 14.1 0.0 0.00 1.4 12.0 4:00p ENE
6 51.9 55.9 4:30p 46.6 7:30a 13.8 0.0 0.02 1.6 11.0 1:00p SSW
7 51.8 55.7 2:00p 45.7 12:00m 14.3 0.0 0.00 3.7 26.0 5:00p N
8 48.1 55.6 2:30p 41.7 8:00a 16.3 0.0 0.00 1.5 13.0 12:00p N
9 50.2 56.1 2:00p 46.5 12:00m 13.7 0.0 0.54 4.4 36.0 3:00a S
10 47.0 53.2 3:30p 40.3 8:00a 18.3 0.0 0.00 2.3 21.0 5:30p N
11 50.3 59.4 1:30p 43.9 6:00a 13.3 0.0 0.00 1.3 9.0 11:30a SW
12 51.1 58.2 3:00p 46.1 7:00a 12.8 0.0 0.00 1.9 11.0 11:30p SSW
13 49.7 53.5 2:00p 44.3 10:30p 16.1 0.0 0.07 3.6 19.0 9:30a N
14 47.8 57.1 4:00p 42.4 6:30a 15.3 0.0 0.00 1.5 13.0 1:30p SSW
15 47.0 55.9 3:00p 42.0 3:00a 16.0 0.0 0.00 1.2 12.0 2:30p N
16 49.2 56.9 3:30p 44.3 6:00a 14.4 0.0 0.00 2.3 11.0 10:30a S
17 52.8 63.8 1:30p 47.5 12:30a 9.3 0.0 0.01 1.8 13.0 12:00p SSW
18 51.4 56.8 4:00p 47.8 6:00a 12.7 0.0 0.02 1.4 17.0 10:00a ESE
19 59.2 68.0 3:00p 46.9 3:30a 7.5 0.0 0.01 3.4 16.0 10:00a NNE
20 62.9 68.6 3:30p 57.6 8:00p 1.9 0.0 0.00 5.3 23.0 11:00a NNE
21 61.9 67.1 2:30p 57.0 9:00p 3.0 0.0 0.00 4.7 22.0 12:30a NNE
22 59.8 67.5 3:00p 51.2 12:00m 5.7 0.0 0.00 3.3 25.0 1:00a NNE
23 55.2 66.4 1:30p 48.3 12:00m 7.7 0.0 0.00 1.0 13.0 3:30p WSW
24 53.0 62.9 4:30p 42.1 3:30a 12.5 0.0 0.00 2.0 15.0 2:30p S
25 58.2 63.6 3:30p 51.6 1:00a 7.4 0.0 0.00 3.3 16.0 11:30a S
26 56.1 61.7 3:00p 51.2 8:30a 8.5 0.0 0.00 2.3 17.0 1:00p SW
27 54.9 61.9 4:00p 49.5 6:00a 9.3 0.0 0.00 2.5 17.0 3:00p N
28 57.7 66.0 4:00p 51.8 3:30a 6.1 0.0 0.00 2.9 14.0 2:00p N
29 54.6 63.3 3:30p 49.1 9:00p 8.8 0.0 0.00 1.4 13.0 12:00m SSW
30 51.5 59.7 3:00p 45.2 11:00p 12.5 0.0 0.00 1.6 13.0 2:00a ESE
31 48.3 51.8 4:00p 43.3 2:30a 17.5 0.0 0.00 2.9 16.0 6:30p SSW
-------------------------------------------------------------------------------------
Tot 52.8 68.6 20 40.3 10 361.2 0.0 0.72 2.5 36.0 9 N
Max >= 90.0: 0
Max <= 32.0: 0
Min <= 32.0: 0
Min <= 0.0: 0
Max Rain: 0.54 ON 12/09/99
Days of Rain: 5 (>.01 in) 1 (>.1 in) 0 (>1 in)
Heat Base: 65.0 Cool Base: 65.0 Method: (High + Low) / 2