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APRIL 2000 WEATHER REVIEW

Early April continued  the unusually warm and dry mid/late March pattern, culminating an extended dry period lasting nearly 5 weeks. Temps were in the high 70's very early, and no rain fell until the 13th.  This Mar/Apr dry period immediately followed a Feb./Early Mar wet period  which saw a Feb. record set for 21 days/rain in San Francisco (but no record here) and almost 15" total rain, with over 6" of it coming in a single 72 hr.period.  By the middle of April, the dominant EPac High finally slackened, allowing yet another repeat of a SW-NE oriented tropical moisture surge getting funnelled over the west coast causing prolonged moderate/heavy rains (especially in orographically favored areas which favor juicy SW wind flows).  This was the fourth time this La Nina-fueled-Winter that a cutoff low/trough dove anomalously deep into the tropics off the coast then, coupled with circulation around the depressed EPac high, flung heavy rain plumes NE over California.  In hindsight,  I believe this is a similar  pattern to the incredible Summer T'Storms of last year, which had prolonged rain on the NE flank of an offshore low. After rain on 5 of 6 days, very mild Spring-like conditions for the most part set in for the last 10 days, (save for a mild rain on the 22nd) with temps mostly in the 50's and lo 60's, and shallow fog along the coast  burning off most mornings. .Rain for April was 2.8", with 1.89" of that falling in a 36hr period on the 16th/17th. Rainfall to date stands at 32.73", or nearly 10" over yearly normal. As this La Nina Winter winds down, almost 40% of our YTD rains have occurred during the four major surges...which as noted earlier, have been  seperated by prolonged, extreme dry periods.The Feb./March/April time frame was a classic example, as heavy rains both preceded and followed one of the driest spells during this time of year in memory. Overall April temps were quite mild, with four 70+ degree days (continuing March's anomalous run of several 70+ days).  After a toasty 79F & 78F on the 1st and 2nd ended a three day run of high 70's temps, we barely nudged 70 only twice for the remainder of the month. Persistent onshore conditions and chilly SST's (51F off Pacifica), kept a clamp on any serious heating along the coast. By month's end, a very typical pattern of weakening GOA lows brushing northern sections with light rain and increased stratus has evolved. Because of the mild temps, lighter than normal winds and the heavy April rain a couple of weeks ago, wildflowers are in major bloom seemingly everywhere. With many trees in full foliage, the flowers are incredible when set against the deep green of new growth on trees and grass. The California Golden Poppy, our state flower, is particularly brilliant and plentiful this year. Offshore, mammoth schools of krill are showing up, bringing huge schools of Salmon along the coast. It will be interesting to see if the humpback whales return to feed as they did 3 years ago, during the last krill explosion. Of interesting note, in recent months almost a dozen gray whales have been found washed up dead along the ocean coast and inside the Bay. Biologists are stumped as to the cause, but malnurishment is being suspected....odd given the amount of food just offshore. Usually, El Nino conditions are cited as cause for the food chain to collapse, as lack of upwelling produces nutrient starved waters. Gray whales feed very little during their annual migration up the coast from Mexico and Hawaii, doing most of their feeding in Summer months in the Gulf of Alaska. I wonder if La Nina has caused a food shortage or had some other effect in the Winter breeding grounds which weakened these creatures? While overall the fish populations seem up, this may be due to now 6 straight years of above normal rains and the resulting improved spawning conditions.

                   MONTHLY CLIMATOLOGICAL SUMMARY for APR. 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  68.8  79.2   2:30p  56.6  12:00m   0.0   2.9  0.00   3.0  18.0  11:15a   NNE
 2  65.4  78.3   3:15p  55.8  12:45a   0.0   2.1  0.00   1.3   8.0   1:45p   NNE
 3  57.6  68.1  11:00a  50.8   7:30a   5.6   0.0  0.00   4.7  26.0   2:30p    SE
 4  55.4  62.0   1:45p  52.4   4:30a   7.8   0.0  0.00   4.4  26.0   2:45a   SSW
 5  53.6  58.8   2:00p  50.5   9:45p  10.3   0.0  0.00   3.3  19.0   1:45p   SSW
 6  53.2  59.6   2:00p  49.0  12:00m  10.7   0.0  0.00   3.6  16.0   3:15p   SSW
 7  54.5  64.8   2:45p  46.8   2:30a   9.2   0.0  0.00   2.6  12.0   5:00a   SSW
 8  52.3  56.0   2:15p  49.8   5:45a  12.1   0.0  0.00   3.5  16.0   3:15p   SSW
 9  53.8  60.4   3:15p  49.8  12:00m   9.9   0.0  0.00   3.8  17.0   9:15a   SSW
10  53.1  59.5   2:00p  48.9   5:30a  10.8   0.0  0.00   2.8  14.0   1:15a   SSW
11  56.3  65.2   4:30p  48.9   7:45a   8.0   0.0  0.00   1.9  11.0  11:15a   SSW
12  60.3  70.8  11:45a  51.0   2:45a   4.1   0.0  0.48   7.6  34.0   1:15p     S
13  56.6  61.2   5:15p  54.7   1:00a   7.0   0.0  0.08   8.2  24.0  12:45a     S
14  56.2  62.4   4:00p  51.8   7:00a   7.9   0.0  0.15   4.1  16.0  10:15a     S
15  55.6  60.9   1:00p  52.9   6:30a   8.1   0.0  0.00   4.9  24.0   4:30p   SSW
16  55.2  60.6  11:45a  52.9  12:00m   8.3   0.0  1.16   4.3  27.0  11:00a   SSW
17  54.0  60.0   3:00p  50.1   7:30a  10.0   0.0  0.73   5.8  30.0   1:30a     S
18  55.2  62.8   9:30a  48.2   1:45a   9.5   0.0  0.00   2.5  13.0   1:00p     W
19  54.9  63.1   1:45p  46.0   6:30a  10.5   0.0  0.00   1.4  10.0   5:30p    NW
20  56.5  64.6   9:45a  49.3   5:00a   8.1   0.0  0.00   2.0  12.0   3:30p     W
21  54.0  56.8   2:45p  52.0   9:15p  10.6   0.0  0.00   4.0  21.0   3:30p   SSW
22  54.2  58.4   2:15p  50.8  10:45p  10.4   0.0  0.17   4.7  18.0  10:30a   SSW
23  54.1  59.7   9:30a  48.8  12:00m  10.8   0.0  0.00   4.9  23.0   3:00p     W
24  53.4  66.4   9:45a  45.0   6:30a   9.3   0.0  0.01   2.6  13.0   2:30p     S
25  53.1  61.0   2:15p  47.2   6:15a  10.9   0.0  0.00   2.2  12.0   6:30p   SSW
26  58.8  72.5   9:45a  47.9   2:00a   4.8   0.0  0.00   2.6  13.0  10:45a   SSW
27  53.9  60.2  12:30p  49.8   1:15a  10.0   0.0  0.02   3.3  17.0   1:30p   SSW
28  52.9  61.6   9:30a  48.3   5:30a  10.1   0.0  0.00   4.8  21.0   2:45p     W
29  53.3  65.6   9:30a  43.9   6:15a  10.3   0.0  0.00   1.8  11.0   5:45p     S
30  54.9  67.9   9:45a  47.7   1:00a   7.2   0.0  0.00   2.3  14.0   4:30p     S
-------------------------------------------------------------------------------------
    55.7  79.2     1    43.9    29   251.9   4.9  2.80   3.6  34.0    12     SSW


Max >= 90.0:  0
Max <= 32.0:  0
Min <= 32.0:  0
Min <=  0.0:  0
Max Rain: 1.16 ON  4/16/00
Days of Rain: 7 (>.01 in) 5 (>.1 in) 1 (>1 in)
Heat Base:  65.0  Cool Base:  65.0  Method: (High + Low) / 2