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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