Prospects for a wet November are dashed; exceptionally dry conditions continue in California

Filed in Uncategorized by on November 9, 2013 46 Comments

For a little while last week, numerical model forecasts were suggesting a very strong possibility of significant rainfall and storminess along the West Coast of North America, including California, beginning late this weekend. This projected major pattern change was driven by a high-amplitude flow pattern over the Central Pacific, which would have allowed a deep longwave trough to develop off of the West Coast and for a series of strong, moist storm systems to move inland at a relatively low latitude. This would have brought meaningful, perhaps heavy precipitation to regions desperately in need of rainfall after an increasingly long and intense dry spell.

GFS depiction of tilted blocking pattern over the Pacific Ocean, keeping California high and dry (NCEP)

GFS depiction of tilted blocking pattern over the Pacific Ocean, which is keeping California high and dry. (NCEP)

Unfortunately, this pattern change that was projected last week has not come to pass. The high-amplitude flow pattern is, as previously predicted, developing in the Central/West Pacific, but the downstream trough near the West Coast has not materialized, and has instead been replaced by fairly strong ridging that will effectively prevent significant storm systems from reaching California for at least the next 7-10 days. It is not entirely clear why the models–which were exhibiting near unanimity in their wet forecasts just 5-7 days ago–changed their tune so dramatically. I suspect that former Super Typhoon Haiyan, which made a devastating landfall on Friday in the Philippines as one of most powerful tropical cyclones ever measured, may be a partial factor in this evolution. West Pacific tropical cyclones often affect the flow pattern over the entire Pacific basin during the fall months as they decay into extratropical remnants and inject considerable amounts of energy into the Westerlies, sometimes resulting in unusually intense storm activity along the West Coast of North America. In this case, it appears that the energy from Haiyan may be acting to further amplify the central/western Pacific blocking ridge, leaving California too far downstream to benefit from the longwave trough.

Super Typhoon Haiyan at its peak shortly before making landfall; sustained winds at landfall were near 200 mph. (NOAA)

Super Typhoon Haiyan at its peak shortly before making landfall; sustained winds at landfall were near 200 mph. (NOAA)

Short-term prospects for California rain are rather dim. Light rain could fall early this week in coastal NorCal as a rapidly decaying cold front brushes the state, but after that the pattern will become even more dry and stable as the East Pacific ridge rebuilds overhead. At the moment, I don’t see any obvious triggers to dislodge this impressively persistent ridge that has stuck around for the better part of two years. We have reached the point where another dry winter will be seriously problematic from a human hydrological standpoint: while reservoir levels for much of the current calendar year were bolstered by the exceptionally heavy (if fleeting) rains last November, storage levels in many of the state’s major reservoirs are rapidly falling as demand for water continues at above average levels and inflows continue to decrease due to the already-late start to the rainy season.

The latest Drought Monitor update indicates that over 84% of California is currently experiencing severe to extreme drought. (NDMC-UNL/USDA/NOAA)

The latest Drought Monitor update indicates that over 84% of California is currently experiencing severe to extreme drought. (NDMC-UNL/USDA/NOAA)

As always, it’s important to keep in mind that the annual precipitation in this part of the world is almost always driven by just a handful of large precipitation events during the cool season, so we’re never more than a few big storms away from a much better water storage situation. On the other hand, we have now reached the point where there will probably be trouble next year if those few big storms never materialize this winter.

Stay tuned.

© 2013 WEATHER WEST

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  • Probably of interest to many of you:

    “Study Finds Climate Link to Atmospheric-River Storms”
    http://www.nasa.gov/centers/jpl/news/earth20131108.html#.Un_sVfmsh8H

  • Dan the Weatherman

    2010-11 overall featured -PDO, +AMO, and a moderate to borderline strong La Nina. As far as the shorter-term oscillations around the time of the atmospheric river event of December 18, 2010 go, we had a -PNA, -AO, and from the looks of the high-latitude blocking over Greenland and lower pressure over the north Atlantic on the map shown, quite likely a -NAO. According to the article, a -PNA, -AO combo is quite rare.

    If the NAO was negative in and around December 18, 2010 like it appears that it was, then this was certainly a rare pattern especially for a year that wasn’t an El Nino, because when the AO and NAO are negative, the PNA is usually positive, leading to ridging and dry weather over CA and the West, and troughing over the Midwest and East as opposed to the atmospheric river CA experienced during this time frame.

  • Also, it’s starting to look like even NorCal might see pretty warm temps and offshore winds at times over the next 2 weeks, so instead of traditional winter rains as we approach Thanksgiving we may actually be looking at very high wildfire risk.

  • alan

    Brutal just brutal.

  • kcanton40

    Just took a peak at the latest CFsv2 climate model that we may actually experience a weak la nina pattern in Jan-Feb then looking forward after that we start seeing a strengthening warm ENSO episode to develop going to toward the middle of 2014. Just keep in mind we are well overdue for a strong El Nino so that is something that needs to be watched for the 2014-2015 rainy season for the state.

    • Dan the Weatherman

      A moderate to strong La Nina or moderate to strong El Nino would benefit us much better under this current -PDO, +AMO regime than this ENSO neutral or weak ENSO that we have experienced the last two years, going on three. I am hoping for a significant ENSO event in 2014-15, or we are going to have serious drought problems in the very near future.

      • At this point, any kind of anomalous flow over the Pacific would probably be better than that status quo. It’s very difficult to get meaningful precip with this incredibly persistent ridging over the Eastern Pacific and West Coast.

        • Dan the Weatherman

          This persistent eastern Pacific ridging has been blocking our primary pathway off the Pacific that storms usually take to bring us significant rain and snow. Instead, during the last two years, storms have been taking a detour into Alaska and/or Canada and then dropping south into our region mainly over land or just hugging the coastline. The end result has been storms with very limited moisture content and a lot of cold dry air. In addition to this the subtropical jet has been quite absent from our area, yet eliminating another source of moisture that benefits us at times in more normal seasons.

  • Nicholas

    Something is telling me that next year its going to be a winning one. We need to get through the valley to hit the peak.

  • Weather West is now on Twitter!

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    • Nicholas

      We doing big thangs!

  • Nicholas

    To no ones surprise California on set for the most dry year ever recorded.

    http://www.sfgate.com/science/article/California-on-course-for-driest-year-on-record-4971192.php

    • Sunchaser

      You would think looking at the latest Enh Infared Goes west image that we would be getting the pineapple connection headed our way…but pictures are worth a thousands words aren’t they ? unfortunately no rain in sight…in ACCUrate weather shows the 45 day outlook as rather dry until about Dec 7 th …with a chance of morning rain …. think im going to start doing rain dances pretty soon..lol

      • Nicholas

        I am sure in a usual year it would be a decent rain event. It looks a bit like last November with the only difference being a bit more north looking.

    • sc100

      Sacramento’s in the same boat as SF regarding driest calendar year on record, with only 4.92 inches for the whole year so far. That stat of 3.95 inches for SF really is incredible. That would be amazingly dry even for Socal. It’s looking like a good possibility November will be completely dry as well just like October was. The only other time both October and November were dry in the same year for Sac was in 1995. And remember, these records go all the way back to 1849. Another way of seeing it is that over the last 315 days there have only been 21 days with rain! Here’s the incredible month by month break-down this year:

      Jan – 1.06
      Feb – 0.26
      Mar – 1.59
      Apr – 0.58
      May – 0.57
      Jun – 0.31
      Jul – 0.00
      Aug – 0.00
      Sep – 0.55
      Oct – 0.00
      Nov – 0.00

      • Dan the Weatherman

        So far for the calendar year, Downtown Los Angeles has recorded a measly 2.78″, while San Diego (Lindbergh Field) has received a somewhat higher 3.63″. In a really good rainy season, these figures could easily be monthly totals in January, February, or even March for either station. Here is the breakdown month by month, and it was incredibly dry in the winter particularly in February:

        Month Los Angeles San Diego
        Jan 1.18″ 1.21″
        Feb .20″ .63″
        Mar .54 1.22″
        Apr T .01″
        May .71″ .26″
        Jun 0.00″ 0.00″
        Jul .09″ .05″
        Aug 0.00″ T
        Sep 0.00″ T
        Oct .06″ .25″
        Nov (to date) T T

        • redlands

          Month Los Angeles San Diego Redlands
          Jan 1.18? 1.21? 1.07
          Feb 0.20? 0.63? 1.22
          Mar 0.54 1.22? 0.93
          Apr T .01? 0.13
          May 0.71? 0.26? 0.21
          Jun 0.00? 0.00? 0.00
          Jul 0.09? 0.05? 0.26
          Aug 0.00? T 0.30
          Sep 0.00? T 0.00
          Oct 0.06? 0 .25? 0.61
          Nov (to date) T T 0.00

      • redlands

        SC100 — Does the rain season up in Sacramento start July 1st and end June-30 like it does in Southern California

        • sc100

          Yes, all of California has the same water year: July 1 – June 30.

  • And new model solutions keep getting worse. The GFS offers little hope of change for its full 16-day run, which almost gets us to December.

  • kcanton40

    Just read on mammothweather.com, Howard has just posted on his blog the latest CFS model runs revealing a possible change in the AO/NAO where there will be a flip from negative to positive phases which would give the West Coast a -EPO which would start bringing in wet weather at least for Nor Cal by the end of Nov and the 1st week of Dec. But, what is more interesting is that there will be stronger blocking taking place in the far Northern Hemisphere such as Iceland. Now keep in mind this is only a model outlook not a forecast! Let’s hope this all come to fruition as the time frame gets near before getting too excited.

  • Nicholas

    Just as Daniel said. This sounds like a scary situation for No Cal. Reminds me a bit of So Cal 2003 event…

    Attention then turns to possible wind event and elevated fire
    weather concerns from Thursday afternoon into Friday with biggest
    concern right now being Thursday night. Updated fuels analysis
    indicates much of the area is not only at record dryness but at
    levels we would normally see around Labor Day or the peak of fire
    season. Recall that we had red flag warnings and wildfires on may
    1st about 6 weeks ahead of normal and now we may be looking at
    legitimate fire season extending towards Thanksgiving. Pattern
    that is prognosticated by the new 00z GFS and NAM models is showing a
    screaming message of strong northerly or offshore winds…most
    notably Thursday night into Friday. NAM 925 mb analysis shows
    boundary layer relative humidity values below 20% with widespread 45 knots wind
    barbs in the 2000-3000 foot elevation layer. This is further
    supported by strong low-level barrier jet down the SAC
    valley…strong surface pressure gradients and flow aloft stacked
    northerly from 700-500 mb with shortwave trough diving down The Spine
    of Sierra and associated downward momentum mixing. Both wind
    advisories and fire weather watches/red flag warnings will be
    possible should the models continue to advertise these solutions.
    The large scale pattern is energetic and highly amplified so large
    run to run model changes remain possible.

    • I’ve lived in Northern California all my life, and the prospect of extreme fire danger on Thanksgiving is downright bizarre.

      • Dan the Weatherman

        After reading tonight’s SFO AFD (partially quoted above), I just realized that the pattern right now seems more typical for early-mid October rather than early-mid November in all of CA in terms of wind events in Norcal and the calmer than average weather of late here in Socal. I have a feeling that it is going to take a couple of offshore wind events both in Socal and Norcal before the pattern finally changes to something more normal for this time of year.

  • redlands

    I hope we get cooler weather — November 2013 at my station in Redlands, Ca in Southern California is currently 2nd warmest November Ive recorded – records back to November 1981. This would be nice if it was during July — I want some cooler weather — along with some rain — could be a rainless November

  • alan

    Had to laugh when I read this:

    THE DEEP MARINE LAYER COULD PRODUCE PERIODS OF RAIN LATE
    FRI NIGHT THROUGH SAT NIGHT. THE DETAILS ARE SOMEWHAT UNCERTAIN DUE TO SOME DISCREPANCIES IN THE MODEL SOLUTIONS.

    LOL

    • Dan the Weatherman

      If the marine layer produces anything, it would be patchy to steady drizzle or a steady light very fine rain with small droplets at most, as opposed to anything heavy.

  • Dan the Weatherman

    Last night’s (and this morning’s as well) SFO AFD mentioned that San Francisco has had only 2 years since records began in 1850 that no precipitation was recorded in both October and November: 1890 and 1959. I strongly believe we are in a very similar climate pattern to the late 1950s and early 1960s right now and have felt that way for quite some time now.

    SFO may have had a bit of rainfall today, but whether it was measurable or not I don’t know at this time.

    Looking back at the records for Los Angeles, 1890 occurred during a much wetter time period than we are in right now, so I am assuming that 1890-91 was probably much wetter in SFO than this year has been despite the later than normal start that season. As a matter of fact, 1889-90 was one of L.A.’s wettest on record, and 1890-91 was drier (over 10″ I believe), but not nearly to the extent of 2011-12 or 2012-13.

    • silvertip

      Sacramento also had dry oct/nov in 1890/1959, interesting they both had an above average september and finished the year 30-40% below normal. This very similar to our 1″ 200% of normal for Sept this year.

      Also of interest is 1880 and 1995 had no rain in oct/nov but did have big Decembers and finished the year approx 45% and 15% above normal

      Those are the only 4 no rain oct/nov that I see.

  • Shady Blues

    Dan, you have been spot on in regards to a very dry Fall while many others thought otherwise. I am certain that you will be right about winter too….you continue to amaze with your impeckable thoughts/forecasts.

  • Nicholas

    The trough over achieved compared to what the models where showing today. The models take the next storm a lot more Western trajectory compared to what it was showing yesterday. Lets not get to excited quite yet on the past few runs.

    • Well, no one south of Eureka got more than a few sprinkles, and I think that SFO didn’t even register a trace. This weekend system is worth keeping an eye on, but either way it shouldn’t produce much precip (perhaps a few showers over the mountains and if we’re really lucky the Central Valley). There’s an equally good chance it’ll be an entirely dry inside slider with strong offshore winds and high fire danger. I will probably have another post later this week with a more detailed meteorological analysis of what has been an incredibly persistent and anomalous pattern over the past 300 days.

  • mendodave

    Mendocino got a few drops, no measurable rainfall.
    I am going for broke, washing ALL the vehicles.
    that outa do it.

  • kcanton40

    Hi Dan,

    I think you are right about this winter, while I was earlier trying to be optimistic about our upcoming winter. But, with this persistent -PDO, neutral ENSO, -NAO combo locked in place and with each passing day and week with yet no significant storms on the horizon I am too beginning to see and feel that we are unfortunately headed for a 3rd dry winter in a row. I have studied drought and wet patterns for years. At this point up here in the Bay Area at least, if this was going to be a wet year we should have seen at least a couple of good storms by now. I know that a dry start does not always mean a dry finish, however, since we are in this wicked combo phase, it certainly does not bode well for us for at least this year!

    • Dan the Weatherman

      I just wanted to point out that you have have been saying -NAO while I believe you mean +AMO as they are not the same thing. The Atlantic Multidecadal Oscillation (AMO) is a Atlantic SST pattern, in which many parts of the north Atlantic including the main development region for hurricanes in the tropical Atlantic are warmer than average during the positive phase, while SSTs are cooler in the negative phase.

      The North Atlantic Oscillation (NAO) is an air pressure pattern related to the AO that occurs over a much shorter time scale as the AMO. In a -NAO, high pressure sets up over Greenland and in nearby regions, while lower pressure is over the north Atlantic Ocean off the east coast, causing a trough in the Midwest and eastern portion of the U.S. (a cold pattern for them), while a +NAO features just the opposite, leading to a milder Pacific flow pattern across the country. The -NAO pattern often coincides with our +PNA pattern which is the death ridge in the eastern Pacific, blocking storms from entering CA. The -PDO aids in this +PNA death ridge pattern and I believe the +AMO amplifies the effect of the pattern even more and the combination of all of these factors seems to make the pattern more persistent and resilient than usual, leading to longer droughts in CA.

  • kcanton40

    I’m wondering, do you remember if we were stuck in this same combo phase during the last major drought period from 1986-end of 1992? I remember those droughts years very well. Likewise during the big drought of 1975-77? It seems to me as I’m learning more about these global teleconnection signs, it is what’s at least partly responsible of keeping the West Coast locked in the +PNA phase which allows the ugly Eastern Pacific ridge to remain stuck in its position every once in awhile for a number of years much like now.

    • Dan the Weatherman

      The period from 1986-1992 was mostly a +PDO, -AMO pattern except for a few brief periods. The PDO went negative for a few months from September 1988 to April 1989, likely related to the strong La Nina that year, but then was negative fall and early winter of 1990, and then from the fall to spring of 1991. The AMO went positive between 1987 and 1988 and for a couple of months in 1999. The shifts in PDO and AMO could have very well been at least partially responsible for this drought, but other factors may have played a role, too, such as a very high solar max around 1989 or 1990. 1986-87 and 1987-88 were El Ninos of varying strength, while 1988-89 was a moderate to strong La Nina, while 1989-90 and 1990-91 were both ENSO neutral, but El Nino formed later in the spring / summer of 1991.

      • Dan the Weatherman

        1975-76 -AMO , -PDO, moderate to strong La Nina
        1976-77 -AMO, +PDO, weak to moderate El Nino

        • kcanton40

          Just curious, is there a particular website you used to look up the different modes and phases of the PDO and AMO? Otherwise, very interesting analysis of how these modes along with other variables such as the sun solar activity(min or max) and the QBO can determine how wet or dry West Coast winters will be.

          • Solar cycles on the sub-decadal scale have a very small (essentially immeasurable) impact on regional weather patterns. The El Nino/Southern Oscillation (ENSO) is the only global-scale mode of inter-annual variability that is associated with very consistent, reliable teleconnections to California climate (strong El Nino=>above normal precip; strong La Nina=>below normal precip). As Dan has mentioned, the Pacific Decadal Oscillation (PDO) is another mode of coupled ocean-atmosphere variability that certainly influences California climate; however, the statistical and dynamical relationship with precipitation is more complicated and therefore its usefulness as a predictor is less straightforward.

            There is also some evidence that the Quasi-biennal Oscillation (QBO) may enhance predictability of California precip, though this process is even less well understood. INTRA-seasonal oscillations associated with the Madden-Julian Oscillation (MJO) are associated with rather strong teleconnections with CA precip (strong MJO event often means heavy precip a week or so later). Other statistically-derived teleconnection indices, such as the Arctic Oscillation (AO) and the Pacific-North American Index (PNA) don’t really increase seasonal predictability of CA precip in wintertime, though in specific situations they may enhance qualitative predictions about specific pattern evolution on multi-week timescales.

  • kcanton40

    Dan,

    I humbly have to admit, I did not know the difference between AMO, NAO. Thank you for explaining and clarifying the differences.

  • Dan the Weatherman
  • I’m also in the process of making some cosmetic changes to the site–let me know if you have any problems.

  • alan

    Long range is completely useless and depressing to follow right now lol. Its like it knows its that time of year for a pattern change so it keeps putting hints in the 250+ hr range but shorter term and real time continues dry so the pattern change for a month now has been endlessly pushed further and further out.

    I’ll just put it this way…its gonna rain…eventually.

    What’s interesting, and I don’t know if this is reflected across SoCal, my average temperature for Nov 2012 was below 32F with more sub freezing highs than not. Three or four cold inside sliders with less than a foot of snow for the month altogether. Dry, cold, windy. Despite low precip totals nov. had the largest number of ‘storms’ for last winter.

    So far this months lows have averaged in the 40’s, highs in the 50’s…yesterday it hit 64 and right now today it is 61.

    • Dan the Weatherman

      There may be some light showers or heavy drizzle on Friday night and Saturday in Socal as a couple of shortwaves move through NV, but totals probably won’t be very high except in the orographically favored areas of the mountain slopes. Then it appears to turn dry again for next week with possible Santa Ana winds.