Dry winters - what is the cause? (Los Angeles: county, average)

[MHarrington]

For the past two years or so, the winters have been unusually dry. I don't there has been a huge abundance of rain and snow since March and April of 2006. Since then, there has been pretty much scant rain and snow (up in the Sierras). What is going on here?

[DMenscha]

Our weather patterns are largely influenced by the surface temperature of the ocean and events known as el nino (wet weather for us) and la nina (dry weather for us). Weather is a hugely complex phenomena and the cycles over which it repeats itself are long.

[FresnoFacts]

Here is a chart of snowfall (blue) and the accumulated snowpack (red) at Donner Summit. Look at how low the totals fell in the mid 1970s. The cycles are very complex and long.
Donner Pass California Average Annual Snowfall with Yearly Sierra Nevada Snow Pack

[bhcompy]

as dmenscha said, el nino and la nina play a large part in our weather. this year has been pretty wet so far in so cal(but these seem to be arctic systems rather than pacific systems), but prior to this the last real wet season we've had was in 96 or 97. el nino was in effect and it rained like it was never going to end. been pretty quiet since then

[MHarrington]

Originally Posted by bhcompy

as dmenscha said, el nino and la nina play a large part in our weather. this year has been pretty wet so far in so cal(but these seem to be arctic systems rather than pacific systems), but prior to this the last real wet season we've had was in 96 or 97. el nino was in effect and it rained like it was never going to end. been pretty quiet since then

Funny. That's not what Weather.com says about Los Angeles (for example).

[Fontucky]

Originally Posted by MHarrington

For the past two years or so, the winters have been unusually dry. I don't there has been a huge abundance of rain and snow since March and April of 2006. Since then, there has been pretty much scant rain and snow (up in the Sierras). What is going on here?

The Winter of 2007/08 gave L.A. some decent rainfall numbers, enough at least to be near average.

[SandyCo]

Actually, 2004/05 was the second wettest year in Los Angeles history with 37.25" of rain between July 1st, '04 and June 30, '05. That was followed by the driest year on record, I think. Last year was a little below average.

The wettest year on record for L.A. was 1883/84 with 38.18" of rain in the same time period. I bet there was a LOT of flooding then, because the L.A. River wasn't encased in concrete yet.

http://www.wrh.noaa.gov/lox/climate/...2_image001.gif

What's creating problems in the Sierras is that California is getting more warm storms, meaning that the snow pack isn't as deep. Since that is where a lot of our water supply comes from, it's obvious why this is a huge concern.

[happ]

We've had wet winters recently as well as bone-dry winters. Unfortunately it doesn't look too good for rain this month as the pattern shifts back to sunny & dry. The Sierra are running above normal because of all the rain in December but sometimes winters start off wet & then go completely dry like last year. Unless California gets a lot of rainfall we may be put on water restrictions this summer

[MHarrington]

So what is the cause of the dry winters? Is it another example of this fickle climate change?

[happ]

Originally Posted by MHarrington

So what is the cause of the dry winters? Is it another example of this fickle climate change?

Check DMenscha earlier post. Subtle changes in the tropical Pacific Ocean along the equator can alter the usual rain patterns. Also a variety of other factors [ie. MJO]. If we are currently leaning toward LA NINA like last winter, then rainfall could be sparse but what storms we do observe are generally colder = more snow in Sierra watershed. Weather models suggest rainfall around Jan 20 w/ a change in the steering currents.