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FEBRUARY 1999 WEATHER SUMMARY

February started out wet, as the 1st marked 12 days out of the previous 16 with measurable precip.  Temps remained on the cool side (only 49.8F mean temp..the first time this year when mean temp for a full month was less than 50F). Frost and light freezes occurred early in the month when rain and winds calmed down...with fog in inland areas a persistent problem. Snow in the local hills fell down to 2K' . (This after snow to 1K' on 1/24 when a very cold trough pushed through).  Heavy rain came through area on 2/5 - 2/8 as 2 cold lows embedded in a long fetch of mid-Pacific moisture pummeled the coast. North Bay Counties were harder hit, with some danger of flooding on the Napa and Russian Rivers, but rivers receded quickly once the rains quit. A classic cold front/T-Storm line hit early on 2/06, with hail, lightning and thunder, with heaviest T'storm activity in the South Bay and in Monterey area. Up to 5" rain in Santa Cruz area, though much less over the hill in San Jose.  The Sierra received up to 7' in the highest elevations with 4' common at around 7K' for the event. Snow level came down to 2K' on back side of the  impulse. With all the snow in the Sierra's, only flurries occurred in Reno, with no snow sticking. On 2/22, thunder associated with a cold trough and an embedded upper low occurred , ending a three day period of mostly light rain. A juicy plume of moisture had hovered over the coast most of the day on 2/20, but lack of upper air support for most of the time contributed to the low rain totals (mostly below 1" in the Bay Area-0.74" here). A basically Zonal flow pattern dominated,  with ridging nudging north then mid-Pacific lows riding on 140-160kt jets beating it back down south. Some of the lows brought unusually cold air down behind them, but either lack of moisture or weak dynamics prevented  the  widespread gullywashers that sometimes occur in these patterns. Most of the heavy rains fell due to orographic enhancement. The last in a series of three dying troughs through here early on 3/01, following a warm front bringing drizzle , fog and light rain most of the day on 2/28.  Only .08" recorded here. Warm air advecting ahead of the trough raised dewpoints to 58F, which was the highest in months. With clearing skies, temps to the mid 60's (and 70's elsewhere) are possible. This air mass is clearly warmer and more humid than what we have been experiencing almost all Fall and Winter. It is possible this signals a generic northward shift in the dividing line between wet/dry zones along the Pacific Coast. In years past, a warm, spring-like spell like this would occur between mid Dec. to mid Jan.- a sort of mid-winter break that separated our "early season" rain pattern from the "late season" pattern. This year, while  the dry spell occurred right on schedule, it was much colder and lasted much longer than normal and created one of the driest periods during that time frame on record. If the current shift to warmer temps is indeed reflecting a generic shift in the pattern, we might expect below normal rain for the remainder of the late rainy season, as lows are guided farther to the north and drying occurs along the southern troughs. On the other hand, if this is just a delayed "break" in the overall Winter pattern as would normally occur much earlier in the season, a turbulent Spring might be on hand, as cold core lows will be drawn down the coast. With the basic pattern remaining quasi-zonal, I am leaning toward a dry Spring. It will take a few weeks to analyze  whether our rains here are nearly over. 

La Nina Update: With still almost three months to go in the rainy season, Eureka has now received 100% of their annual rain total (37") and San Francisco with 18", is also nearing annual norms (20.5") with 120% of normal to date.  However, just to the south at San Francisco Airport (SFO) which typically receives almost the same rain as The City , only 80% (11.7") of normal to date has fallen and 65% of annual totals.   SoCal continues less than 40% of normal to date in most areas (L.A. has received barely 4" as compared to a normal of almost 11").   The Santa Cruz area is an anomaly, as zonal flows have hovered twice over the area this Winter..and near normal rain totals have resulted in a narrow band-maybe 50-75 miles north to south.  Sierra snowpack  water content in the Cent Sierra (near Tahoe) was just measured at 166% of normal (over 300" of snow currently at top of Kirkwood), but the southern Sierra is only 60% or less.  The northern mountains, and especially in the far NW, continue way above normal, with exceptionally hazardous conditions in Washington and the Northern Oregon Cascades. Sea Surface temps immediately off the coast continues 4-5F below normal, hovering around 51-52 degrees. Even San Diego is reporting SST's in the 50's. Water vapor imagry still shows a definate lack of activity in the ITCZ, and very dry air in the western Pacific equatorial region. Based on this alone, it seems likely La Nina will be with us at least a couple more months, and possibly longer.

                   MONTHLY CLIMATOLOGICAL SUMMARY for FEB. 1999


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  45.3  54.7   2:00p  39.8   3:30a  17.8   0.0  0.00   1.3  11.0   9:30a   WSW
 2  47.5  57.3   2:00p  40.8   2:00a  16.0   0.0  0.00   1.6  11.0   2:30p     N
 3  49.0  55.9  12:00p  44.6   1:30a  14.8   0.0  0.00   1.8  11.0   7:00p   SSW
 4  49.6  54.9   1:30p  44.6  10:00p  15.3   0.0  0.00   2.8  19.0   2:00a     N
 5  47.7  54.5   2:30p  42.6   3:30a  16.5   0.0  0.00   2.6  14.0   9:30a   SSW
 6  50.9  53.2  12:00m  48.1  12:30a  14.3   0.0  1.34  14.9  52.0  11:30a     S
 7  53.6  55.4   9:00a  50.9   9:30p  11.8   0.0  0.84   8.9  43.0   8:30a     S
 8  53.3  55.1   2:30p  51.7  12:30a  11.6   0.0  0.39  11.1  47.0  12:00m     S
 9  46.5  54.6   3:30a  41.1  10:00p  17.2   0.0  0.63   8.5  50.0   3:00a     S
10  45.2  51.0   3:00p  40.9   8:30a  19.0   0.0  0.00   2.2  12.0   1:30p   NNW
11  46.5  54.1   3:00p  40.0   2:00a  18.0   0.0  0.00   3.6  20.0  11:00a   NNE
12  48.8  59.2   3:30p  43.4   6:30a  13.7   0.0  0.00   4.0  18.0  12:30p     S
13  49.7  59.1  12:30p  45.4   6:00a  12.8   0.0  0.20   2.2  15.0   7:30p   WNW
14  48.6  53.4   1:00p  44.0   9:00p  16.3   0.0  0.01   2.0  16.0  12:30a   SSW
15  47.9  55.6  12:00p  41.1   7:30a  16.7   0.0  0.00   1.4  13.0  10:00a   SSW
16  52.3  54.6  11:00p  49.0  12:30a  13.2   0.0  1.08   8.8  35.0   1:30p     S
17  53.7  59.1   1:30p  47.2   9:30p  11.8   0.0  0.20   1.8  11.0  12:30a     S
18  49.3  53.7  12:00p  46.0  12:00m  15.2   0.0  0.53   4.1  37.0  12:30p     S
19  49.6  57.7   2:00p  42.9   8:00a  14.7   0.0  0.01   2.7  19.0  10:30a   NNE
20  50.0  53.8  11:00a  46.9  12:00m  14.7   0.0  0.71   6.6  32.0   1:00p     S
21  48.7  54.5   2:30p  43.6   7:00a  16.0   0.0  0.06   4.6  21.0   9:30p   SSW
22  51.7  58.6   2:30p  46.4  12:00m  12.5   0.0  0.05   1.6  14.0   2:30p   WSW
23  51.1  60.5   2:30p  45.7   4:30a  11.9   0.0  0.00   1.3  12.0   3:00p   WSW
24  51.0  57.4   1:00p  44.1   5:00a  14.3   0.0  0.44   5.3  32.0   8:00p     S
25  50.1  55.9   1:30p  46.8   6:30a  13.7   0.0  0.11   3.8  30.0  12:30a   SSW
26  48.9  55.8  12:30p  42.5   5:00a  15.8   0.0  0.00   1.5  11.0   4:00p   NNE
27  52.8  61.7   3:30p  45.4  12:30a  11.4   0.0  0.00   1.9  14.0   9:30a     W
28  56.2  61.8   2:30p  50.5   2:30a   8.8   0.0  0.08   2.9  16.0   3:30a   SSW
-------------------------------------------------------------------------------------
    49.8  61.8    28    39.8     1   405.4   0.0  6.68   4.1  52.0     6       S


Max >= 90.0:  0
Max <= 32.0:  0
Min <= 32.0:  0
Min <=  0.0:  0
Max Rain: 1.34 ON  2/06/99
Days of Rain: 14 (>.01 in) 11 (>.1 in) 2 (>1 in)
Heat Base:  65.0  Cool Base:  65.0  Method: (High + Low) / 2