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
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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
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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