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Treebeard's Stumper Answer
5 January 2001

Rain or Shine

It's hard to complain about this beautiful winter weather we're having in California, but it's not right. There were warm, gusty Santa Ana winds in L.A. on Christmas day, and wildfires in Ventura and San Diego. I don't want to use that d-word that rhymes with "shout," but it's been very dry since our early October rain. The hills are still brown. What a contrast with our El Niño floods just three years ago! Why is the weather so different this year? What is blocking our normal winter storms, and what is the outlook? I've included a separate page of Santa Barbara weather records and an Excel spreadsheet file. Are there patterns here?

We've had temperatures in the 80's this week at Dunn Middle School in the Santa Ynez Valley behind Santa Barbara in central California. It's dry. The hills are brown. There's an 11,000+ acre wildfire burning in San Diego County. If there are fires now, what will August be like? At the same time, there has been record cold across the country. It's not El Niño or La Niña this year.

What's happening?

I found it surprisingly difficult to find long-term rainfall records for Santa Barbara. It was easy to find yearly rain data going back to 1877. The National Weather Service (NWS) has monthly records back to 1941. I finally found month-by-month records going back to 1930 at the National Climatic Data Center (NCDC), part of NOAA, but I had to extract the numbers from the big four-megabyte california.txt data file. NCDC offers free historical records for every state. The ultimate source for detailed weather info seems to be the NCDC Daily Historical Climatology Network (USHCN) that has thirty-one fields of daily weather data for 1064 stations across the country. But it's a 110 MB download (compressed!), way too much for my slow modem connection. The NCDC Global Historical Climatology Network (GHCN) has weather data for the world. NCDC sells regional data reports. Don't we taxpayers already pay for this?


Santa Barbara Santa!


Our winter storms come from the ocean, but this year they've been pushed north by high pressure over Utah and Nevada, like bumper-pool with air masses. Look at the 125 year Santa Barbara rainfall record below. Our weather has always swung between drought and deluge with no simple pattern. There have even been dry El Niño years, like 1965-6. As a naturalist, this is why I love the Santa Barbara region. We're perched between desert and Redwood forest, and every year is different. We finally had our rain this week, and I hope we'll get more. But I'll take what comes, and smile.

Long-term rainfall records for Santa Barbara. The data are a composite from the Santa Catalina Island Conservancy, the National Climatic Data Center (NCDC), and NWS data for the SBA station at the Santa Barbara Airport. This data is available on a separate page of Santa Barbara weather records and an Excel spreadsheet file.

Notes:

The timing for this stumper couldn't have been better. Our Santa Barbara rainfall in November and December was just 0.3 inches, less than 10% of the 4.65 inch average. But last week, we received 9.8 inches of rain in one storm at my house on San Marcos Pass in the mountains behind Santa Barbara. The Weather Channel reported San Marcos Pass at the top of their rain tables! There's snow on the high mountains, the Santa Ynez River is running, surf's up, and the hills are turning green. This storm puts us well above average. We really do swing between drought and deluge here in Central California.

Drought pattern on New Year's Day. That solid looking Pacific storm will move north of California because of high pressure over the desert. Deluge pattern on January 10. We're getting hammered by this tightly-wound storm that dropped 10+ inches in the Santa Barbara mountains.

Look at the graph. It's obvious that more dots are below the blue average line. I count 47 years above average, and 76 years at or below average. Pick a year at random, and the odds are that it will have below normal rainfall. This sounds like the old Garrison Keillor joke about Lake Wobegon, where all the children are above average. Of course the reason is those few very wet years like 1997-98 that raise the average.

I went through the Santa Barbara monthly rain data, and picked out the wettest and driest years for each month on record:

by Month:OctNovDecJanFebMarAprMayJunJulAugSepTotal
Greatest Rain:3.028.269.8418.2021.7612.386.553.751.210.811.484.0191.27
Least Rain:0.000.000.000.000.000.000.000.000.000.000.000.000.00

It's interesting that every month has had zero rainfall in at least one year! It's also interesting that the wettest year (1997-98, 47.08") and the driest year (1989-90, 6.50") are both recent. Is this a consequence of Global Warming, that weather swings are becoming more extreme?

Graybear writes:

I suppose the answer must include the El Niño/La Niña effect, but it also relates to chaos theory - we can tell with fair accuracy what the weather will be like tomorrow based on what it is today, and what it will be like the next day, but minute discrepancies compound until we cannot say what it will be like in a week. Apparently you didn't know you would be flooded with up to 20" of rain when you posted the stumper. I hope you have been able to stay high on your mountain and that the flooding hasn't impacted you as much as the electricity shortages.
We got through the storm just fine, though the heavy rain and hail made it hard to watch the episode of Ken Burn's excellent Jazz series on PBS television. We're on top of the mountains on solid rock, so our runoff becomes other peoples' problem down below.

(There's another stumper there. We started with our Primestar Satellite TV service over 10 years ago. Originally, we got 10 or so channels from the small dish on the roof. When it rained, we would see white "snow" on the TV screen. I figure each spot on the screen was the image of a rain drop blocking the dish. Then Primestar (now DirecTV) switched to digital. We get lots more channels, but the picture breaks up in weird ways in the rain, and finally disappears. I assume this has to do with MPEG video compression schemes that transmit the differences between frames rather than whole video frames, so the MPEG decoder gets lost.)

Our Central California climate is sometimes controlled by El Niño, and sometimes by high pressure that builds over the Great Basin. Our wettest years involve northern Pacific storms that pull in a sub-tropical jet stream "Pineapple Express" of tropical weather. But nothing is simple! Here are the records for past strong "Type 1 El Niño" events since 1950. (Data from El Niņo and California Precipitation.)

Type 1 El Niño
Rain Year
1951-21957-81965-61968-91972-31977-81982-31991-21998-9
Total Rainfall
(Oct. - Sep.)
31.2532.2114.3430.5223.3541.6441.3519.9247.08
Difference From
Average (18.34")
+12.91+13.87-4.00+12.18+5.01+23.30+23.01+1.58+28.74

El Niño and the Southern Oscillation (ENSO) are obviously part of the story, but not the whole story, as 1965-6 shows!

Exceptional years are always interesting, but long sequences of wet and dry years have more impact. The seven year drought from 1983-1990 was our longest recent dry period. 1918-1935 looks even worse from the record. These extended droughts change the way people use their land and effect the distribution of native plants and animals. After the last dry period, Santa Barbara's water supply was dangerously low; water rationing was in effect; cattle herds all but disappeared from the Santa Ynez Valley; The Painted Cave Fire burned into the city; Santa Barbara voters approved construction of a state of the art reverse osmosis seawater desalination facility that has never been used since; and they approved a connection to the California State Water project. There are lasting consequences, despite a recent wet decade. Cattle herds are still scarce (except when a ranch property is up for sale!), and former ranch land is being converted to vineyards and exclusive housing developments. People forget, and there is now a State Water aquaduct to supplement our limited local supply. It makes me nervous to see so much open land at risk for development, and natural limits being ignored.

Wet years make a difference too. The heavy rains in 1998-9 caused a landslide in Tequepis Canyon that literally took out a locally rare colony of Five-Finger Fern (Adiantum aleuticum). Extreme events either way can make a difference!

Here are some links for your own weather research:

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Copyright © 2001 by Marc Kummel / mkummel@rain.org