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
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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
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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