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DECEMBER 1998 WEATHER SUMMARY

An overall much below average rain month (1.82"), wetter early on, record warmth and dry in the middle of the month, then continued dry and very cold for the last half. Only 3 days of .5" rains, none >.6"  A deep, cold GOA low hit the coast in late Nov/early Dec. bringing high winds, huge surf and moderate rain locally. Rain total in Pacifca was 1.18" for the event ending on Dec 1, with a nice frontal passage dropping about .4" in an hour.  This event brought November rains to generally near normal, with above average rains along the Cal/Ore border.  By the middle of the month, very warm offshore winds brought record temps (77F) to Pacifica and elsewhere, with damaging Santa Ana's in SoCal. The record warmth was quickly replaced on the 19th and 20th, as a rapidly advancing arctic airmass from the NNE brought record cold and SNOW showers to Pacifica on 12/20. The cold air mass affected most of the country including the West Coast.   The Snow was produced by an embedded low in the rapidly advecting cold airmass which produced a sort of "bowshock" effect along the arctic frontal zone. Embedded thunderstorms along this front created up to 6" of snow locally in the hills and flurries to sea level in Monterey County and lesser amounts  here. Briefly moderate snow was reported at Rockaway Beach in Pacifica. 5 separate snow squalls hit my house from between 0630 and 1100 hrs, with one at 0930 producing thundersnow and briefly near zero visibility. Air temp at 37F prevented snow from sticking, but nearby Montara mountain was completely encased in white on two occasions. Squalls also produced moderate pea hail on three occasions. Total liquid precip was only .16", as dew points quickly fell into the 20's after the initial frontal passage. Near record cold followed the snow event, with high temps in the upper thirties to mid forties throughout the area for almost 6 days. Lows in the mid-teens were widely reported. Agriculture has been hard hit by the widespread freeze, with low temps at Bakersfield in the mid to upper teens. This cold air should eventually be replaced in January by a more progressive, almost zonal flow pattern which should develop to our north, then slowly sag south.

 
MONTHLY CLIMATOLOGICAL SUMMARY for DEC. 1998


NAME: HOME CITY: Pacifica  STATE: 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  51.0  56.7   2:30p  46.8   5:00a  13.3   0.0  0.00   1.5  13.0  12:30p   NNE
 2  54.6  56.0   1:00p  50.3  12:30a  11.8   0.0  0.04   4.4  18.0  10:30p     S
 3  50.7  56.0  12:30a  43.3  12:00m  15.3   0.0  0.56   5.5  31.0   5:30a   WNW
 4  45.6  49.8   3:30p  41.9   2:00a  19.2   0.0  0.00   3.0  15.0  11:00a   NNE
 5  45.9  52.2   1:30p  38.7   7:30a  19.5   0.0  0.43   5.3  44.0   7:30p     N
 6  47.0  52.6   2:30p  42.5  12:00m  17.5   0.0  0.00   3.4  30.0   1:30a   NNW
 7  47.1  53.4  12:30p  40.8   6:30a  17.9   0.0  0.01   1.6  13.0   9:30a   SSW
 8  48.8  51.3   7:00a  43.4  10:00p  17.7   0.0  0.00   3.7  17.0  12:00p   NNE
 9  48.8  55.5   3:30p  42.1   4:00a  16.2   0.0  0.00   3.1  19.0  12:00p   NNE
10  50.4  56.4   2:00p  46.1   6:30a  13.8   0.0  0.00   2.9  15.0   1:30p     N
11  50.5  57.4   1:30p  46.1   7:30a  13.3   0.0  0.00   2.4  18.0   4:00a     W
12  53.1  59.0   3:00p  48.5  12:30a  11.3   0.0  0.00   4.0  18.0   5:00a     S
13  52.1  57.6   1:00p  47.8  11:30p  12.3   0.0  0.53   5.8  36.0   1:00p     S
14  50.5  55.9   2:30p  47.5  11:30p  13.3   0.0  0.00   2.7  23.0   3:30a     N
15  56.2  62.3  12:00m  47.3   3:30a  10.2   0.0  0.00   4.7  26.0  11:30p   NNE
16  64.6  69.3   2:00p  58.5   8:00a   1.1   0.0  0.00   7.0  28.0   9:00a   NNE
17  64.2  69.9   1:00p  54.5  11:00p   2.8   0.0  0.00   3.4  16.0   1:30a     W
18  54.9  61.5   4:30a  48.3  12:00m  10.1   0.0  0.00   3.9  23.0   3:30p     S
19  46.4  51.1   2:30p  41.0   9:00a  19.0   0.0  0.00   4.1  24.0   4:30a     W
20  40.5  45.7  12:30a  34.3  12:00m  25.0   0.0  0.17   4.7  34.0   7:30a     N
21  36.2  43.1   3:00p  30.7   8:30a  28.1   0.0  0.00   2.4  19.0   1:00p   NNE
22  39.4  47.1   3:30p  35.1  12:30a  23.9   0.0  0.00   2.5  17.0   1:00p   NNE
23  40.8  47.3   3:00p  36.6   1:30a  23.1   0.0  0.00   3.6  16.0   1:30p     E
24  40.6  47.5   3:00p  35.0   8:00a  23.8   0.0  0.00   3.5  17.0   1:00p     S
25  44.9  53.4   2:00p  39.5   3:30a  18.5   0.0  0.00   2.9  18.0   9:30a     N
26  49.1  57.9   1:00p  43.2   1:00a  14.4   0.0  0.00   1.4  14.0  11:00a    SW
27  48.8  56.5   4:00p  44.4   2:00a  14.5   0.0  0.01   2.0  16.0  10:00a     S
28  48.6  55.1   3:30p  44.3  12:00m  15.3   0.0  0.01   1.5  13.0   1:00p     N
29  48.8  56.7   2:00p  44.0  12:30a  14.7   0.0  0.01   1.6  16.0   1:00p     S
30  50.6  61.3   2:00p  44.5   5:30a  12.1   0.0  0.00   2.1  14.0   2:30p     E
31  50.2  52.8  12:30p  44.7  12:00m  16.3   0.0  0.05   2.4  18.0  10:30a     N
-------------------------------------------------------------------------------------
    49.1  69.9    17    30.7    21   485.0   0.0  1.82   3.3  44.0     5       N


Max >= 90.0:  0
Max <= 32.0:  0
Min <= 32.0:  1
Min <=  0.0:  0
Max Rain: 0.56 ON 12/03/98
Days of Rain: 6 (>.01 in) 4 (>.1 in) 0 (>1 in)
Heat Base:  65.0  Cool Base:  65.0  Method: (High + Low) / 2