The extraordinary California dry spell continues: 2013 will probably be the driest year on record

Filed in Uncategorized by on December 13, 2013 82 Comments

Recent weather summary

An extremely cold (but also quite dry) storm system originating over Western Canada brought long-duration hard freezes to most regions and some snowfall to very low elevations in parts of Northern California late last week (including flurries on the beaches near Eureka and very substantial snowfall in Redding around 500 ft AMSL in the Northern Sacramento Valley). Some daily record lows were set for the month of December, and in a few places temperatures were colder than they have been at any point in several years. The remarkably cold modified Arctic airmass that has brought bitterly cold air to much of North America has now shifted eastward, and the West Coast is in the midst of a slow but substantial warming trend that will continue at least through the coming weekend.

GFS forecast depicting  a very warm airmass for mid-December. (NCEP)

GFS forecast depicting a very warm airmass for mid-December. (NCEP)

Temperatures will rise to above-normal levels, with a few record high temperatures possible early next week as offshore flow promotes compressional warming in favored regions, with possible fire weather concerns in Southern California. Later in the week, though, a weak low will ride down the eastern side of the seemingly ever-present Northeast Pacific ridge, perhaps bringing a few showers but more likely initiating yet another offshore wind event. In any case, any precipitation (if any) would be extremely light.

Looking even farther ahead: it looks like the possible eastward eastward progression of the Madden-Julian Oscillation in the West Pacific has not transpired as was projected in the medium-term models, and West Coast weather has not become subsequently more active. Unfortunately, there is actually quite good model agreement on the overall pattern over the East Pacific through the end of the month: the huge ridge over the Eastern Pacific is expected to persist and perhaps grow even more, continuing the extraordinarily dry pattern over California but allowing for occasionally large swings in temperature as a very cold airmass over Canada is occasionally able to spill westward in weak or even slightly retrogressive (east to west) zonal flow. In short: California (and, in fact, much of the Pacific Coast region) is in for more of the same for the foreseeable future.

GFS forecast depicting the continuation of the Ridiculously Resilient Ridge of 2013. (NCEP)

GFS forecast depicting the continuation of the “Ridiculously Resilient Ridge of 2013.” (NCEP)


The Ridiculously Resilient Ridge of 2013

As improbable as it may seem, the extraordinary California dry spell of 2013 has continued well into the month of December, and there are virtually no prospects for relief over at least the next two weeks. The most recent climate statistics suggest that calendar year 2013 is very likely to go down in the record books as the driest on record for the state of California, possibly by a considerable margin.

I’ve discussed fairly extensively in previous posts (here and here) the structure of the highly persistent and amplified geopotential height ridging over the Gulf of Alaska that began in December 2012 and has continued up to the present. This anomalous ridging has been the proximate cause of California’s extraordinary dry spell, as it has directed the primary storm track well northward into Alaska and British Columbia and promoted large-scale atmospheric subsidence (sinking air unfavorable for precipitation and storm activity) further to the south. Given the remarkable persistence and distinct structure of this high-impact feature of recent atmospheric circulation, I would argue that it’s now worthy of a proper name. With this in mind, here’s a visual reminder of the spatial and temporal character of the Ridiculously Resilient Ridge of 2013 (or, for brevity’s sake, the RRR):

The Ridiculously Resilient Ridge of 2013

The Ridiculously Resilient Ridge of 2013 (NOAA/ESRL PSD)


Just how dry has it been in 2013?

We all know that it has been extremely dry for the past year in nearly every corner of the state. Newly-released data from the National Climatic Data Center, though, starkly illustrates just have phenomenally dry 2013 has been relative to the historical record.

Time series of January-November precipitation anomalies in California from the full historical record. Note that 2013 is literally off the chart. (NCDC)

Time series of January-November precipitation anomalies in California from the historical record. Note that 2013 is literally off the chart. (NCDC)

The January-November 2013 period is not only the driest since at least 1895, but it also surpasses the previous record driest year to date, 1898, by nearly 16%! Precipitation deficits have actually grown even larger since the end of November, and given the current forecast for a continuation of exceptionally dry conditions for essentially the rest of the calendar year, I expect that it’s very likely that California will experience it’s driest calendar year on record in 2013.

Also of considerable note is that the current 12 and 24-month periods are drier than any other 12 or 24 month period since 1977. 1976-1977, some of you may remember, featured one of the most acute short-term water shortages California has ever faced in the modern era due to two consecutive winters with very low rainfall and snowfall. The above chart, however, illustrates just how far behind 2013 is relative to either 1976 or 1977.


2013 year-to-date precipitation anomalies. Note the very large region with precipitation totals less than 25% of the long-term mean. (NOAA/NWS)

While the ever-important caveat is that it would only take a couple of strong, moist storms (namely, an atmospheric river or two) to bolster our reservoir levels to a level adequate to get us through next summer, there is likely to be rapidly heightening concern in the coming months over possible water shortages in the medium and long term if the “rainy season” doesn’t actually become rainy in pretty short order. 


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  • Dan the Weatherman

    I know that we have experienced the oceanic oscillations such as what are in place now in decades past with the -PDO, etc. However, does it seem that there is another element in play that is constantly reinforcing this ridge over and over again? Having this pattern dominate for an entire year to this extent is very unusual.

    What has occurred more frequently in the past is that we have a certain pattern, a ridge somewhat like this for example, that is more dominant during a season, but the pattern changes intraseasonally when something comes along from time to time such as an MJO in a favorable phase, and we get at least a couple of storms or a series of storms, before the more dominant pattern comes back for a while (the ridge in this example) before the next change. As of late it seems, the pattern changes just barely enough for a single storm probably due to retrogression of the ridge, and the ridge then just bounces back into its previous position (earning the appropriate nickname of the Ridiculously Resilient Ridge of 2013).

    • Sounds about right to me. The location of this ridge is definitely a signature of a negative phase of the PDO, but its persistence is pretty amazing. Hard to know exactly why it is so persistent, but I’ll keep exploring this moving forward.

      • Ricky Wogisch

        Do the weather patterns from
        1976-77 resemble our current situation?

        • That’s a good question. I’ll take a look at the composites later.

          • Dan the Weatherman

            While you are at it, you may want to check 1975-76 as well, to see if matches up to the current weather pattern in any way.

          • Flunking_retirement

            Same time, I don’t recall seeing such inactivity in the subtropical jet last couple years either. I don’t know if that’s partially a supporting cause or a result of the RRR. Normally, we get at least one or two southwest entrainments a year if not a separate system come So Cal’s way even in drought years that ease the situation, some, but we haven’t see any of that for 2 years now.

          • I’ll check this out tomorrow and include in the next blog update if there’s anything interesting.

        • Jai

          Yes they do

          Simulation of a Blocking Event in 1977
          Miyakoda et. al., Monthly Weather Review, Dec. 1982

  • Charlie Hohn


  • Betty KC

    Okay, I understand this RRR is extremely unusual. Can you tell me what needs to happen for this ridge to move or dissipate? Im assuming thats what needs to happen to allow the storms into California. Furthermore, what is your prediction as to what might happen in the long term, 2014 and beyond?

    • Usually a “blocking” ridge such as this one eventually becomes unstable, either because it deflects the normal flow pattern so much that it breaks down the thermal anomalies that allowed it to form in the first place or because westerly flow becomes strong enough at low latitudes to “undercut” the ridge and reestablish zonal flow along the subtropical storm track. An intensification of the West Pacific jet could do either or these things, or a particularly large cyclone could help to disrupt the prevailing patterns of thermal anomalies that have been so spatially consistent. Ultimately, though, both of these things have already happened several times over the past year and the ridge just rebuilds immediately afterward. I don’t have a really good reason why that’s happening at the moment…

      2014, at least the early part, may well be dominated still by anomalous ridging. There are hints of a possible El Nino event starting in the spring, which if it comes to fruition should change the Pacific flow pattern enough to prevent this persistent ridge from dominating. That’s a long way away, though, and probably won’t have any effect on this winter’s weather.

      • Kamau40

        Just heard on the weather report on one of the Bay Area’s local new station about the incredible rainfall deficits in some of the following cities which probably reflects how bad this current drought has been for the entire state: Santa Rosa(-23in), San Francisco(-15in), and San Jose(-9in). There is still no end in sight as far as I can see which means we will be in very, very bad shape come next summer if this patter does not change real soon!!

      • xeren

        do you think that the quick re-establishment of this ridge has anything to do with the ~3.5 degree Sea surface temp anomaly sitting almost right under it? or are sea surface temps unrelated?

        • These anomalous SSTs are very likely related, though it’s hard to say without more information whether they’re a cause or effect of the anomalous ridging. I discussed this a bit in my more comprehensive earlier discussion of this dry spell:

          • And regardless of initial causality, at this point it’s most likely contributing to the recent persistence as you mention. As far as SSTs go, 3+ degree anomalies are actually very large.

          • Dan the Weatherman

            Did the SSTs in this area get this warm anytime during the last -PDO phase from 1945 to 1977, or is the data too sparse from that time to determine that?

          • xeren

            yeah, if we were lucky enough to have that 3.5 degree anomaly along the equatorial pacific instead, that would be the largest el nino in a long time. we’re not that lucky though, i guess…

      • Jai

        The number of cut-off lows in 2013 are about 400% (just guessing) from the 1975-2005 average. For the first time we are also seeing cut-off highs happening around 60’N latitude and above. This is a symptom of a slower jet stream caused by a change in the angle of descent into the arctic (higher temperatures, higher altitude GPH)

        Now, how does this affect the subtropical jet???

        • There certainly have been a lot of cut-off cyclones lately, and in general these types of systems are associated with a weak or meandering jet stream. The possible connection to differential high-latitude warming (i.e. Arctic amplification), which is driven largely by rapid loss of Arctic sea ice, is a fascinating one, but I don’t think that question has yet been satisfactorily answered. This is actually a topic very close to my own research, and is also potentially relevant to the journal article you posted today.

        • This is a topic close to my own research interests. See the Pethoukhov et al. paper I mentioned above. I certainly think that a connection between a weak/meandering jet and persistent/wandering systems and differential high-latitude warming (i.e. Arctic amplification) is plausible, but the scientific evidence up to this point remains insufficient to support this claim beyond reasonable doubt. Stay tuned!

          • Jai

            did you notice the june 21 wrong way storm from Tennessee to texas, down to mexico and then up to Montana? a 14 day backwards moving cutoff low. It was outrageous.

            You probably know about this one. I think it is a good baseline.

          • California also experienced an extremely rare warm-season atmospheric river during that time frame. 2013 has featured some exceptionally strange flow patterns in the Northern Hemisphere.

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  • Randomly came across this site and enjoy the breakdown of the exceptionally dry years. Not only is this excessive ridge of high pressure keeping rainfall amounts low but it’s being a drag for those of us that enjoy surfing. The past couple of years have been the worst years for surfing that many can ever remember.

  • Any chance we could do some weather control experiments and weaken the high pressure ridge?

    • Mike Stephenson

      Or is it already the result? O.o

    • Well, that would certainly be an interesting modeling experiment.

      • Thanks. Just wondering if that would be a federal or state prerogative.

        • At present we don’t have any physical means to manipulate specific weather patterns. We’re certainly making a large-scale change to the climate system over the long term through emissions of greenhouse gases and changes to the land surface, but at present there’s no obvious way for humans to have active control over chaotic weather patterns.

          That said, the State of California (Department of Water Resources) is actually ramping up its cloud seeding program this year, though I’m not totally convinced that will be entirely useful. There is some scientific evidence that existing precipitation can be enhanced locally as a result of well-planned and executed cloud seeding regimens. The big problem is this: cloud seeding cannot create precip where there isn’t any–it only marginally enhances existing rain/snowfall–and we’re really not seeing any storm activity at all. Interesting stuff, certainly!

          • Thanks again. I was asking about the cloud seeding, as I had heard of it. It seems that given the Chinese efforts during the Olympics, such efforts would only follow. The results of the cloud seeding would be educative, even at a micro-level.

          • Jai

            How about lower stratospheric SO2 seeding in the tropics? isn’t that considered the most effective geoengineering strategy to combat global warming (basically adding about 1/10th of the total high altitude Pinatubo volume each year in the 0′ to 20’N latitudes)

          • There have definitely been modeling studies regarding possible geoengineering options, but none of these has ever been attempted in the real world (for two reasons: first–the uncertainties regarding the outcome and unintended consequences, and second–the practical complications of actually implementing something on as large a scale as would be necessary).

          • Well, we’ve done modeling strategies on large-scale geoengineering options, but they are generally too risky/complicated/expensive to conduct on the large scale (at least so far). We’ve never actually attempted this in real life. Even if we did, though, we still wouldn’t be able to target specific weather patterns.

          • Jai

            who is this “we” you are referring to?

          • Tom Maxwell

            I would enjoy your comments with regard to the ideas expressed at Pages are dedicated to Improving rainfall in Ca and a test method stakeholders could employ. Microwave heating of clouds has no scientific standing, experimental test results, and no supporters in the science community. But the current crisis is demanding that no possibility for improving rainfall be overlooked, no matter how bizarre the concept may seem at the outset of study. Thanks

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  • redlands

    Was 84 in Redlands, Ca Today — Dec-16-2013 — Was a pretty day — however way too warm/hot for Dec — Would be nice to get to 84 in the middle of summer. Bring on the cooler weather

  • redlands

    Was warmer today Dec-17-2013 in Redlands, Ca — It reached 86 — which is a record for the day at my station — records back to Aug-1981. Its also the 3rd warmest temp Ive recorded for the month of December — Warmest being 88 — 2nd warmest 87 — It needs to cool down

    • Dan the Weatherman

      I agree with you that it needs to cool down to more normal levels!

      I am really getting tired of this wet season pattern of cold and a little bit of rain, then followed by warm and dry, and repeat ad nauseum that has been going on since last January and even during the 2011-12 season. I am ready for some real storms to come off the Pacific to give the area a good soaking and a good deal of snowfall to help out with our water supply and decrease the fire danger. It is absolutely ridiculous to have brush fires in places further north like Big Sur this time of year, even though they can happen in Socal during drier falls such as this.

      • Betty KC

        When is this storm expected? And is it expected over the Bay Area? I don’t see anything in the next 10 day forecast.

        • Some light showers are possible tomorrow, mainly in Southern California, but it won’t amount to much if anything and the Bay Area should stay mostly dry. No storms are on the horizon.

          • Dan the Weatherman

            I realized I forgot to mention above where these rain totals were forecast to occur. They are for the Socal coastal and valley zones that aren’t shadowed by any mountain ranges from the W or NW.

  • wobblyradical

    This pattern extends well up into Oregon. We have a tiny spring/water-right that feeds a little pond. Been here 15 yrs. and it’s always filled back up by october. NEVER seen it this low, almost gone 9ft. down. I’m amazed(not really) that, esp. here with all the timber and agriculture, that there is so little discussion or awareness in the media. Had a major fire last year and it’s hog heaven in the burn area cutting trees(with lotsa fed. $) to sell, at a discount, to china. Lotsa $ generated by all this and likely more to come. Silver lining to that global warming that don’t exist? Is Big Sur the START of fire season?

    • The region of abnormally dry conditions has definitely been expanding to the north this fall. It’s not as extreme as in California, but that could change:

      • wobblyradical

        Another “storm” predicted this weekend, less than 1/10. Another “silver lining”? Warmer ocean, bigger waves-Surfs up!

  • Gary Zack

    Interestingly enough as of December 15 2013 we have mobilized a fire handcrew, 5 wildland fire engines and two additional handcrews to southern california for fires. This weather pattern will put a good hurt to us if we are still in fire season?

    • It really is pretty amazing to see this kind of fire activity in NorCal this time of year.

  • Dan the Weatherman

    Why is it that this ridge has not been able to be undercut by a lower latitude storm track as often happens in a high-latitude blocking situation? Is it due in part to the lack of an enhanced subtropical jet, an unfavorable phase of the MJO, the cooler waters associated with the cold (negative) phase of the PDO, or is the main branch of the polar jet been weaker than normal lately with smaller than normal storm systems?

    • The unusual persistence of ENSO-neutral conditions has been associated with a weak subtropical branch of the jet over the Pacific, so that is definitely part of it. I don’t think the polar branch is necessarily weaker, but it has been deflected well to the north due to the RRR.

      • Jai

        I have been following the pattern of unusually low relative humidity at GPH of <300mb in the tropics this summer. see:

        It seems that this unusual pattern has severely reduced the intensity of the Hadley Cell this summer. Is this a causative factor in the maintaining of the RRR?

        Similarly, we had an identical ridge in the 1977 winter

        • Thanks for sharing that paper! I think that is extremely relevant, and it’s possible the causal mechanisms are similar. However, in this case, the ridging has persisted for over a year(!), rather than just 3 months. I’ll take a close look at that later…thanks again.

          The tropical humidity anomalies are interesting, though it’s hard to say if they’re related to the current situation. What we’re not seeing is an unusually weak West Pacific jet, which might be expected if the Hadley cell was driving this persistent pattern. My best guess right now is that the pattern is being maintained by SST anomalies and a transient/planetary wave resonance as discussed in this 1983 paper (see also Pethoukhov et al. 2013:

          • Betty KC

            What were the weather conditions that broke the ridge in the winter of 1977? If we were to have those same conditions, would it break this ridge? If so, do you forsee it happening any time soon? If not, could this condition possibly persist for years?

          • Jai

            I thought that the SST anomaly was a result of the ridge, not vice versa.

            Isn’t there a series that tracks Hadley cell intensity? Dollars to doughnuts it went to nil in march 2013.

            It is very interesting that the GLORY satellite launch failed and the ENVISAT failed in April of 2012.

          • Well, in a general sense the forcing could be acting in either direction. Based on the SST anomaly time series I checked today, though, I’d agree that it looks like the ocean anomalies are being forced by the atmosphere in this case (though there is inevitably some positive feedback here as well). There’s still the background -PDO signal in SSTs which is probably at least partially responsible for the maintenance of this pattern, but it’s hard to believe that there isn’t also something interesting behind the incredible persistence of the stationary/quasistationary ridging over the North Pacific for the past 400+ days. I’m taking a look at the 20th Century reanalysis for the next post.

            And this is certainly an inopportune time for multiple Earth-observing satellite failures. It’s tough to get new ones up there these days…

  • While I don’t have a huge deal of confidence in the CFS long-range projections, this image is pretty ominous, depicting a continuation and even amplification of the RRR for the rest of winter. Yikes.

  • redlands

    Well !!! As of 1145am Dec-19 – 2013 — this storm is a big flop — only 0.01 of rain — in Redlands, Ca

    • Sunchaser

      Just got home and as of 7:06 PM the rain gauge shows .68 here in the South East part of Glendale, Ca and looking at the radar looks like I’m getting the wrap around moisture from the storm right now…woow…..Its about time !!! Need about 100 more like this….Please Santa bring me more rain ..?

      • Unfortunately that rainfall was very localized, even within SoCal. No rain at all fell north of Monterey!

        • snow755

          We have had a trace of rain today it was overe by noon

      • Dan the Weatherman

        I received some light showers here in Orange today, but I don’t think it is nearly as much as you got. I will check my gauge later and post a total.

  • Nicholas Gumina

    In Whittier yesterday it was real interesting. To my West I could see blue sky and over my area the rain was light most of the day. This was till the sun got into an angle where it broke through the clouds. This helped make it unstable and oh man did it come down in buckets. Also got some hail for a few seconds. Huge convective drops and while it was only 0.26 it did flood the streets since it rained so quickly. Saw a few distant flashes of lightning as well.

    It also left a double rainbow

    • Glad there was some excitement down south! Unfortunately, it made little to no dent in our extreme drought…

  • Nicholas Gumina

    Kevin martin was right on the money. My area got pounded but areas to my west got almost nothing.

  • Dan the Weatherman

    Paul Pastelok,’s long range forecaster just said the following in today’s article on regarding CA’s current drought:

    “It will remain dry through February and probably early March in California,”
    “It’s possible that a system or two could reach the state, but not enough to put a dent in the drought.”

    If it stays dry through early March, we are looking at potentially another 2006-07 type of year, which is the last thing in the world we need right now. I hope his prediction is wrong and that it turns wetter sometime next month. This extreme dryness can’t go on forever!

    • Keep in mind that 2006-2007 was only extremely dry for Southern California. Northern California has recently received less actual precipitation than Southern California (not just relatively less, but in absolute inches!), and Los Angeles is still on track for its driest calendar year on record! That should hint at the truly extreme degree of dryness right now. I’m working on creating some figures for the next post–will probably be up tomorrow.

      • Dan the Weatherman

        That’s right, Norcal was closer to normal than Socal during the 2006-07 season. This year is far worse because the whole state is experiencing the 2006-07 type of dryness that Socal had.

  • redlands

    Redlands, Ca Weather Summary — (( 12-19-13 Hi 53 – Low 41 — only 0.04 of rain —– )) (( 12-20-13 Hi 63 Low 38 — 0.01 —- ))) So the grand total for the storm was 0.05 of rain. For the month of Dec-2013 — 0.26 For the 2013-2014 rain season 2.70 —– Another disappointing storm. I was over in Highland /San Bernardino, Ca area and it appears that they got more rain than 0.05 we got — times it was coming down pretty good.

  • redlands

    Yes the 2006-7 rain season was a dry season, however 2001-2 at my station in Redlands, Ca got a measly 2.78 for the whole season. I hope that doesn’t happen this year — but its not lookin good

  • redlands

    I was looking at my weather records — that is my rain records — Starting Jan-2011 up to now – Dec-20th- 2013 — which is 36 months — I averaged out those 36 months — it averaged out to 0.71 of rain per month — that’s dry !!!! December 2010 – I got 10.46 of rain — which was the last good month – rainwise

  • Flunking_retirement

    I guess we are in the right place. Tijuana Valley – Otay Mesa area in So San Diego is at .65 for the season, .70 for the backyard. However, even that is less than half of normal, and falling rapidly behind now with every day.

    Largely anecdotal; as some of you know, Im a professional mariner, have been in the trans Pacific trade for some years now, I have rarely seen such mild winters in the North Pacific these last two years as far as the intensity of the storms we’ve met. Rainwise yes, but only well above latitude 60, and not the heavy driving wind and rain that deliver enough punch to carry through the blocking highs. Not that I don’t appreciate it, id rather have to worry about calmer conditions than the normal this time of year, but something to think about non-the-less. Ill leave it to Daniel and others of you that know about the mechanics of it to come up with the possible reasons..

    • Dan the Weatherman

      Are you saying that the storm systems travelling the jet stream upstream of the RRR are weaker than normal overall and further north, or just that the winds associated with them are not as strong?

      • Storms have been deflected way to the north–as in, north of the Pacific basin entirely and over continental Alaska. Fairbanks has had some really bizarre weather over the past few months.

        • Dan the Weatherman

          This is really an amplified pattern then if the storm systems are being forced way up into Alaska before coming down into the Lower 48. No wonder it has been so cold with the deep trough in the middle of the country with the western states being on the edge of it.

          • Flunking_retirement

            Well, yes Daniel, and that falls right in with our experiences. Dutch Harbor, in the Aleutians is an interchange for us, They have been averaging 5 to 10 degrees above normal (15 to 30F for December) for the past year or more.

  • craig matthews

    I live on the central coast of California 7 miles southeast of big sur. I have lived here for 40 years and have never seen it this dry. Even during the infamous drought of 1976-77 we at least had some rain. Ridiculous is the right word. I think there are many forces in the atmosphere/ocean that are aligning just right to cause this historic event. I did some studying on the drought of 1976-77{which may have begun in 75} and found that the pattern across the north pacific basin was similar, yet there was a weak el nino during that winter, and there was more convection occurring along the equator near the date line. Yet the following winter of 77-78 was a weak el nino winter and we had buckets of rain as for some reason the westerlies were able to undercut the ridge. So I’m not looking for el nino to solve this problem, although maybe this time it might help if it develops.

    • Dan the Weatherman

      I think you are absolutely correct in that there are many factors aligning together to produce this historic dryness.

      I believe the combo of the cold (negative) phase of the Pacific Multidecadal Oscillation (PDO) and the warm (positive) phase of the Atlantic Multidecadal Oscillation (AMO) leads to drier than normal winters in southern CA, and when this occurs with ENSO neutral or very weak ENSO, it can lead to record dryness and that exact pattern is what we are experiencing right now and has been like that for the last two winters. This is in my opinion is very much like the pattern of the mid 1940s to early 1960s, which was in general a much drier regime for Socal. Norcal was not as dry overall during that time period, going by Tahoe snowfall totals, even though there were some drier years in there.

      There are likely other additional factors than just the ones I just mentioned that are contributing to the incredible dryness affecting the entire state, especially northern CA. Dryness in Socal is more common than it is in Norcal this time of year.

      • Dan the Weatherman

        As for 1976-77, the AMO was its cold (negative) phase, and the PDO had just flipped from its cold (negative) phase to the warm (positive) in the summer of 1976 and remained that way until the fall of 1977 when it negative for a few months before going positive again in the winter of 1978. The positive phase of the PDO is overall more favorable for wet weather in CA, including during these ENSO neutral / weak ENSO events, and I believe that helped probably along with other factors to make the conditions for the winter of 1977-78 more favorable for getting storms. As a matter of fact downtown Los Angeles received over 30″ of rain that season, and that has been achieved only 7 times since records began in 1877, the latest being in the 2004-05 season.

    • I delved into the NCEP climate reanalysis yesterday and have looked at the large-scale patterns for many of these periods. Much of this will be discussed in the next blog update–either tonight or tomorrow. Stay tuned! A preview: calendar year 2013 does stand out pretty starkly from all other years since at least 1948. There are multi-month periods where similarities are very strong (including the 1976-77 winter), but the year plus long persistence of the current anomaly does, in fact, appear to be unprecedented in reanalysis.

  • craig matthews

    I found an interesting study online. “A hypothesis for the 1976-77 western drought” by James Johnstone, Dept of Geography, UC Berkley. Does anyone have some good info on the PDO,WP/NPO phases. I have found some info but conflicting info on how long we’ve been in the negative PDO phase.

    • Dan the Weatherman

      Negative PDO – 1945 to 1976, 1998-2002, 2007 present

      I don’t know about the WP/NPO phases, but others here can probably shed some light on them.

    • craig matthews

      Thank you.

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