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DECEMBER 2000 WEATHER REVIEW

DECEMBER 2000 WEATHER REVIEW

The progressive, cool and wet weather of October which evolved first into a colder, then gradually milder/drier November, became quasi- stagnant  for virtually the entire December resulting in one of the driest on record under moderate temps.. Total rain was a paltry 0.72", all of which fell during a 7 day showery period between the 9th and 16th as a series of once-potent storms slammed into our dry continental airmass and basically evaporated-on -contact..leaving paltry little rain in their wake. Actually, this lack of rain is just another manifestation of the same basic pattern we've had for months which has seen a mean flow of continental air flowing N-S or offshore into the sub tropical EPAC region. As the dry air flows south, it then turns gradually westward, where it amplifies the E-W trades and enhances surface cooling over the EPAC waters (La NIna), all of which reduces available moisture for storms to the north. Currently, SST's remain near normal, but the dry continental air that has been flowing for months is blocking tropical air from flowing north. While it is much too early in the year to project with high confidence the pattern for our second phase of Winter (Jan.-Mar.), the "D" word is being more than whispered about in matters of water control measures and power generation needs. And with the current energy crunch in California, below normal hydro-electric power  generation in coming months/years could have a major impact on our economy. Once these powerful cause/effect systems get entrenched, only major changes elsewhere can dislodge the pattern or cause a change in the generic storm track. To illustrate how generic patterns can linger, keep in mind Cent. California has just experienced above average rains in 7 out the last 8 years, which immediately followed a 6 year period of much below normal rains. Many places like Fresno have just set all-time records for driest Nov./Dec.time periods... receiving only .08" for both months together. Here in Pacifica, 1.52" fell in Nov./Dec, less than 25% of our normal 7" for the same time period. After the very cold temps of early November, temps rebounded nicely with numerous days in the 60's, and no days of frost. The mean avg. temp of 53.6 was much more typical this time of year (typical mean is around 54)---yet was almost 2 degrees warmer than this November's mean of 51.9.

                   MONTHLY CLIMATOLOGICAL SUMMARY for DEC. 2000


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  50.7  57.4   5:00p  47.0   5:45a  12.8   0.0  0.00   1.5  13.0   1:15p   ESE
 2  52.5  60.3   4:30p  46.3   8:30a  11.7   0.0  0.01   2.7  18.0   2:00p    NE
 3  53.2  58.3   3:45p  48.8   9:15a  11.5   0.0  0.00   4.1  21.0   9:15a     S
 4  57.0  62.5   4:45p  51.9   2:45a   7.8   0.0  0.00   4.0  15.0   3:00p     N
 5  58.9  63.6   3:15p  56.1   8:45a   5.2   0.0  0.00   4.6  18.0   2:15p     S
 6  58.2  62.9   1:00p  54.3   9:00a   6.4   0.0  0.00   3.9  22.0   9:45a   WNW
 7  57.2  63.1   2:45p  54.3  12:00m   6.3   0.0  0.00   1.0  10.0   1:00p     N
 8  54.7  61.8   3:45p  49.4  11:45p   9.4   0.0  0.00   0.8   8.0   2:00p     S
 9  54.4  58.0   1:30p  49.6  12:15a  11.2   0.0  0.02   0.5   6.0  11:45a   ESE
10  52.3  55.4   1:30p  45.2  12:00m  14.7   0.0  0.02   1.4  12.0   2:00p   SSW
11  50.1  54.1   1:45p  45.5  12:15a  15.2   0.0  0.08   2.7  36.0   8:30p   SSW
12  50.4  55.2   1:30p  47.1   9:15p  13.8   0.0  0.05   1.7  12.0   2:30a     S
13  51.8  55.9  11:45a  48.3   1:15a  12.9   0.0  0.30   5.6  30.0   2:00p     S
14  53.7  55.0  11:30p  50.0   7:00a  12.5   0.0  0.13   4.9  28.0   1:30a     S
15  52.7  56.8   1:45p  48.1  10:30p  12.6   0.0  0.11   2.3  11.0   7:00a     S
16  53.3  59.6   2:15p  49.0   7:00a  10.7   0.0  0.00   3.3  19.0  12:00p   NNE
17  52.7  59.7   3:00p  46.4   6:45a  11.9   0.0  0.00   3.9  20.0  11:45a   NNE
18  53.7  58.6   2:30p  50.1   8:00a  10.7   0.0  0.00   5.8  24.0   3:30a   NNE
19  55.3  65.7   2:45p  48.5   7:00a   7.9   0.0  0.00   2.5  19.0   2:00a    NE
20  54.6  61.9   3:00p  48.3  12:00m   9.9   0.0  0.00   3.5  25.0   1:15p   WNW
21  52.6  57.3  10:00a  46.6   3:30a  13.1   0.0  0.00   4.6  28.0  12:45p     S
22  52.8  58.6   3:00p  47.5  12:00m  12.0   0.0  0.00   0.9  12.0   1:30a     N
23  50.2  56.2   2:00p  45.6   6:30a  14.1   0.0  0.00   0.6   8.0   1:15p     N
24  50.6  56.6   2:00p  47.4  11:45p  13.0   0.0  0.00   1.8  16.0  11:30a   NNE
25  52.6  57.5   2:45p  47.1   2:30a  12.7   0.0  0.00   3.9  19.0  11:15a   NNE
26  54.3  61.3   2:45p  49.8   5:45a   9.5   0.0  0.00   3.6  19.0  11:30a     N
27  54.6  62.5   2:45p  49.2   2:45a   9.2   0.0  0.00   3.3  19.0   8:45a   WNW
28  56.6  64.4   2:30p  52.3   3:00a   6.7   0.0  0.00   3.4  16.0   6:00a     S
29  54.7  61.5   2:15p  50.1   7:45a   9.2   0.0  0.00   2.5  12.0   6:15a   ENE
30  53.4  60.5   1:30p  49.1   6:15p  10.2   0.0  0.00   2.6  13.0   7:45a     S
31  52.5  61.1   2:45p  46.3   4:45a  11.3   0.0  0.00   2.4  18.0   7:45a     N
-------------------------------------------------------------------------------------
    53.6  65.7    19    45.2    10   335.8   0.0  0.72   2.9  36.0    11       S


Max >= 90.0:  0
Max <= 32.0:  0
Min <= 32.0:  0
Min <=  0.0:  0
Max Rain: 0.30 ON 12/13/00
Days of Rain: 7 (>.01 in) 3 (>.1 in) 0 (>1 in)
Heat Base:  65.0  Cool Base:  65.0  Method: (High + Low) / 2