Downtown Los Angeles (USC) will end the the 2011-2012 water year (July 1 to June 30) having recorded 8.69 inches of rain. This is about 58% of the 1981-2010 normal of 14.93 inches. The deficit of 6.24 inches is a little more than the 5-6 inch deficit recorded in a selection of similar second year La Nina years. According to data compiled by the NWS Santa Barbara will end the water year at about 66% of normal; Camarillo/Oxnard at 57%; Burbank Airport at 51%; LAX at 59%; and Long Beach Airport at 62%.

This TAO/Triton plot of Pacific equatorial SST and anomaly clearly depicts the evolution of our two year La Nina and the recent transition to warmer conditions. Is an El Nino in the works for this Winter? According to the Multivariate ENSO Index (MEI) a transition to El Nino conditions may already be underway. The April/May value of the MEI was +0.706. This is already within the range of a weak El Niño ranking. In his June 6 discussion of the MEI climatologist Klaus Wolter noted the last month's increase in the MEI was the 6th highest increase for this time of year since 1950. He also pointed out that it was the 4th monthly increase of this caliber in a row -- second only to the record of six consecutive large monthly increases in 1997 at the beginning of the mega El Nino of 1997-98. It will be very interesting to see if the string of large increases in the MEI continues with the May/June value.

While the ocean seems to be on board with the El Nino idea, the atmosphere appears to be balking -- at least for the moment. As of June 24, the AAM component of the GWO was down around -2.0, which is nearly as low as it's been during year two of the 2010-2012 La Nina. A positive value of AAM is generally associated with El Nino conditions.

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Judging from this NEXRAD regional composite radar image last week's system might have been much wetter. As has happened a couple of times this season, much of the heavier rain appears to have remained offshore. Even so, this compilation of rainfall totals from around the area by the NWS Los Angeles/Oxnard lists some respectable rainfall totals for a late season storm in Southern California.

Downtown Los Angeles (USC) recorded 0.49 inch for the storm, increasing April's rainfall total to 1.71 inches. This is almost double April's normal of 0.91 inches. The water year total rainfall for Downtown Los Angeles now stands at 8.68 inches; which is about 60% of normal at this point in the water year. The water year extends from July 1 to June 30.

In a "normal" season Los Angeles would be expected to record another 0.35 inch of rain by June 30. Both the 6-10 Day Precipitation Outlook and 8-14 Day Precipitation Outlook from the CPC are indicating a better chance of below normal precipitation in Southern California than of normal or above normal precipitation. The CPC Monthly and Three Monthly Temperature and Precipitation Outlooks are indicating an equal chance of above normal, normal, and below normal precipitation in Southern California. We'll see!

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Some of the video of yesterday's rainstorm looked more like coverage of a hurricane rather than an April storm in Los Angeles. There were flooded streets and creeks, lightning strikes of aircraft and gas lines, strong winds, waterspouts, hail, toppled trees, mountain snow and more. Downtown Los Angeles (USC) set a new rainfall record for the date of 0.49 inches, breaking a record set in 1956.

The system's strong dynamics were due in part to upper level divergence associated with an ideally positioned jet max and strong positive vorticity advection. The result was strong omega, with 12z NAM vertical velocities at KVNY on the order of -25 microbars per second from 900 mb to 600 mb.

Apirl's above average rainfall has increased the water year (July 1 to June 30) rainfall total for Downtown Los Angeles to 8.19 inches, which is about 58% of normal. Here are some preliminary rainfall totals from around the area for the storm earlier in the week and yesterday's storm compiled by the NWS, and a snapshot of a Ventura County Watershed Protection District Google Map (large image) with some rainfall totals for the past week.

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Low pressure "alow and aloft" and associated surface boundaries resulted in some higher than expected rainfall totals Sunday. Gauges in the Santa Monica Mountains generally recorded from 2-3 inches of rain, Valleys and the Metro area 1-2 inches, and Los Angeles County mountains 1-2.5 inches. Here are some preliminary rainfall totals from around the area compiled by the NWS, and a snapshot of a Ventura County Watershed Protection District Google Map with some additional rainfall totals.

Downtown Los Angeles (USC) recorded 0.95 inch for the storm, bringing the 2011-2012 water year total to 6.93 inches. This boosts the water year total to 51% of normal. The wet weather the last two weekends makes March the wettest month of the rain season to date at Los Angeles. It may have taken the edge off a very dry rain season for the moment, but rainfall totals the past 30 days have still been below normal in much of Southern California and additional rainfall would really help.

The good news is it looks like the current progressive pattern of West Coast troughs will continue into April. While at the moment it appears the next trough in the series won't produce more than a smattering of rain south of Pt. Conception, the ECMWF has been relatively consistent in bringing in a system similar to our last storm weekend after next. That's a long way out, and the GFS and GEFS don't agree with the ECMWF, but we'll see!

Update 04/02/12. Saturday's system produced a little more rain than expected south of Pt. Conception. Downtown Los Angeles (USC) recorded 0.04 inch for the storm, bringing the 2011-2012 water year total to 6.97 inches. Here are some rainfall totals from around the area compiled by the NWS. At the moment it looks like a disturbance rotating around a large Gulf of Alaska low will probably not elongate and deepen the low enough to produce rain in Southern California, but will result in cooler temperatures Wednesday and Thursday. Higher pressure is forecast to build in behind the trough, with a warming trend forecast through Easter weekend.

According to the Australian Bureau of Meteorology ENSO Wrap-up, issued March 27, the 2011–12 La Niña event has ended, with key indicators returning to neutral levels.

The IRI/CPC mid-March plume of forecasts made by dynamical and statistical models for SST in the Nino 3.4 region suggest ENSO Neutral conditions will persist through boreal autumn 2012. However, as climatologist Klaus Wolter points out, all ten of the two-year La Niña events between 1900 and 2009 either continued as a La Niña event for a third year (four of ten), or switched to El Niño (six of ten), with none of them becoming ENSO-neutral.

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Updated 03/29/12. Edited to include the rainfall total from October 5 in the Downtown Los Angeles rainfall comparison.

Although there were scattered showers throughout much of Southern California Sunday morning, the Los Angeles Marathon beat the 70/30 odds for measurable rain and stayed dry. Given the cool and breezy conditions, I'm sure runners were glad the precipitation forecast worked out on the dry side!

According to KCQT data Downtown Los Angeles (USC)recorded 0.76 inch for the storm, bringing the water year total to 5.98 inches, which is 46% of normal for the date. This was less than the 1.15 inch recorded Downtown on October 5, the 0.90 inch recorded on November 20, and the 0.96 inch recorded December 12-13, but in some areas Saturday's storm was wetter than any of these storms.

Because of the very strong southwesterly inflow that accompanied the storm, upslope precipitation enhancement produced some impressive totals in the foothills and mountains. For example, West Fork Heliport recorded 3.82 inches, OPIDS Camp 4.49 inches, Mt. Baldy 3.76 inches, and Nordhoff Ridge 5.32 inches. Here are some preliminary rainfall totals from around the area compiled by the NWS, and a snapshot of a Ventura County Watershed Protection District Google Map (PDF) with some additional rainfall totals.

Here are a NEXRAD regional radar image, water vapor satellite image, IR satellite image and RAMDIS visible satellite image of the system at noon Saturday. The parent low north of Pt. Conception is beautifully structured and there is strong convection associated with the frontal boundary south of the Los Angeles.

On a run in the Santa Monica Mountains Sunday morning, I found melting graupel in the Santa Monica Mountains at an elevation of about 2300' along Castro Mtwy about a mile east of Castro Peak. This cell that appears to be the best candidate for the producing the graupel is shown in this KVTX NEXRAD radar image from about 9:00 am PDT Saturday morning.

Both the GFS and ECMWF medium range models show a trough evolving into an upper level low just off the Central California coast this weekend. It's too early to put much credence in the forecast, but some precipitation in the Saturday to Monday timeframe looks like a possibility. We'll see!

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Updated 03/29/12. Edited to correct the date for the most rainfall in a day this season (through March 16) at Los Angeles.

It's been a bleak rain season. So far the most rainfall Los Angeles has recorded in a day this season was in the record-setting early season storm October 5, when Downtown recorded 1.15 inch of rain. As of today Los Angeles' water year rainfall total stands at a meager 41% of normal.

If current forecasts verify, the rainfall total at Los Angeles for this weekend's storm might exceed last October's storm. Maybe. BUFKIT display of WRF ensemble precipitation forecast shows a spread from 0.4 inch to about 1.1 inch at LAX, and from about 0.65 inch to 1.6 inch at Van Nuys. The 18z WRF/NAM run was wetter than the 12z run producing about 0.95 inch at LAX and 1.1 inch at Van Nuys. A strong southwesterly inflow of around 35-40 kts is forecast and could produce higher precipitation amounts on foothill and mountain slopes which have a southerly to westerly aspect.

The Los Angeles Marathon is this Sunday, and after last year's record-setting Marathon day rainfall, many are wondering about the weather on Sunday. Last year of 19,798 runners that completed the race, more than 10,000 were on the course for longer than 5 hours and nearly 2000 were out there for longer than 7 hours. The Elite Men and most of the runners start at 7:24 am, so the majority of runners will finish after noon.

Check with the NWS for the latest official information, but as it looks now the bulk of the rain is forecast to occur on Saturday and the Marathon will be run after the cold front has passed through the area. This is a different weather scenario than last year, but one that can produce cold, showery, blustery conditions with strong winds out of the northwest. In the unstable conditions that typically follow a cold front heavy showers, gusty winds and even a thunderstorm are possible. The HPC 6-Hour Probabilistic Precipitation Guidance for the periods ending 10:00 am Sunday morning and 4:00 pm Sunday afternoon indicate a high probability of at least 0.01 inch of rain in the Los Angeles area. We'll see!

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Wednesday Downtown Los Angeles' water year rainfall total fell below 50% of normal for the date. With only 5.22 inches of rain in the bucket it looks like we're headed toward the driest rain season since the record-setting dry water year of 2006-2007, when a meager 3.21 inches was recorded. If Los Angeles ends the rain year (June 30) with less than 7.16 inches of precipitation, the 2011-2012 water year would be one of the ten driest on record.

It's been dry throughout most of Southern California and much of the state. According to data compiled by the NWS Burbank's water year total now stands at a paltry 34% of normal; Long Beach 49% of normal; Camarillo 42% of normal; Santa Barbara 56% of normal; and Paso Robles 49% of normal. Southernmost California has fared a little better with San Diego at about 79% of normal for the date. Central California rainfall is also well below average with San Francisco at 35% of the normal, San Jose at 26% and Sacramento at 40%.

I received an email recently from a reader asking if I thought a March Miracle was likely this year. Keeping in mind the chaotic nature of weather, and that low probability events do sometimes occur, the short answer is that I don't think it's likely we'll see higher than normal rainfall this March.

In a post in early October I discussed what the impact of a second year La Nina might be on 2011-12 Winter precipitation in the continental U.S. For a selection of seven second year La Ninas the coastal Southern California climate division recorded about 5 to 6 inches less precipitation than normal for the period November through March. If we take a look at March rainfall in that same selection of second year La Ninas, four of the seven recorded less than 0.5 inch rain in March, and only one was well above average -- 4.83 inches in March 1975.

Current outlooks are not favorable for higher than average March precipitation. The Climate Prediction Centers 6-10 Day Precipitation Outlook, 8-14 Day Precipitation Outlook, and One Month Precipitation Outlook all indicate below normal precipitation in Southern California. The ESRL/PSD Analog Probabilistic Precipitation Forecast is also dry in the 6-10 and 8-14 day outlook period, and the PSD Ensemble Spread does not look encouraging.

On the climate side of things the active phase of the MJO has been stalled in the Indian Ocean, but the 15-day ensemble ECMWF and several models forecast increased amplitude and eastward propagation. As a result of strong negative East Asian and Tropical torque events, relative atmospheric angular momentum is dropping like a rock, with the GWO taking a big dive into La Nina territory. Should the MJO continue to propagate and AAM increase over the next 2 weeks, perhaps we'll see the scenario necessary to generate an extended Pacific jet strong enough to impact the West Coast.

Monday its looking like we may get a little rain and possibly some lower elevation snow. Goes soundings and model data indicate the Pacific system is moisture-starved, but it is quite cold and is forecast to have strong dynamics. A GOES sounding near the systems core showed a 500mb temp of -30°C. Precipitable water values in the circulation around the low were around 0.6 inch. With such cold air aloft, and strong system dynamics, strong convection is a possibility. We'll see!

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

Last Sunday's upper level low resulted in a little rain, mostly south of the L.A. basin, but Southern California and much of the West has been dry, dry, dry. How dry? Take a look at this plot of percent of average precipitation for the past 90 days from the Western Regional Climate Center.

Downtown Los Angeles (USC) has not recorded measurable rain for more than a month. The last measurable rain was on December 17 when 0.01 inch recorded. The water year precipitation total for Los Angeles has been stuck on 3.76 inches, which is about 2.5 inches below normal. The Sierra has been especially dry. The Statewide Summary of Snow Water Content for January 18 reported the snowpack at 10% of normal. Remarkably, Mammoth Mountain recorded no natural snow between December 5 and January 19!

The good news is the very stubborn West Coast ridge has finally relented, opening the door to a more zonal flow and a sequence of shortwave troughs. The change in pattern is forecast to produce significant rain and snow over most of the West Coast the next few days. The HPC 5-day Precipitation Forecast indicates up to about 5 inches of precipitation in some areas of the Sierra and North Coast, and over 9 inches in some areas of the Pacific Northwest.

The change in pattern isn't forecast to produce much rain south of Pt. Conception, but at this point just about any amount would be helpful. BUFKIT analysis of WRF Ensemble forecasts for Van Nuys indicate precipitation amounts ranging from about 0.1 inch to 0.5 inch, beginning sometime this evening and ending midday Saturday. The 18z NAM precipitation forecast for Van Nuys projects about 0.25 inch for the storm. Some mountain areas could see somewhat higher precipitation totals, particularly those with a west-facing aspect.

Another shortwave is forecast to move through the area Monday. Model projections differ, but we could get a little rain out of that system as well. We'll see!

Update January 25, 2012 8:00 am PST. Precipitation totals across the area from Monday's system generally ranged from about 0.3 inch to 0.75 inch. Downtown Los Angeles (USC) recorded 0.62 inches for the storm. This combined with the 0.68 inches from Saturday's system boosted the water year total for Los Angles to 5.06 inches, which is about 75% of normal for the date. The medium range models have been all over the place. Yesterday the 12z GFS forecast for Monday morning depicted an upper low and trough on the West Coast, while the ECMWF indicated some ridging. Here's a GFS/ECMWF comparison from San Jose State University Meteorology. Given the recent Sudden Stratospheric Warming (SSW) and rejuvenation of the MJO there's plenty of uncertainty in the medium range. The ECMWF seems to like the idea of a relatively fast-moving trough affecting the West Coast sometime around February 1. We'll see!

Update January 21, 2012 1:30 pm PST. Perhaps because its jet stream dynamics were more favorable than expected, this first system was a little stronger and held together a little better south of Pt. Conception than suggested by the models. Rainfall totals tabulated by the NWS generally ranged from about 0.2 to 0.7 inch in the Los Angeles area, with somewhat higher totals recorded in Ventura County and Santa Barbara County. Model projections have varied on the strength of the system forecast to move through the area on Monday. The 12z NAM projected about 0.4 inch for Van Nuys; the 18z NAM about 0.3 inch, and the 12z GFS about 0.5 inch. The system appears similar to today's, but it looks like the shortwave trough and vortex max may track more directly into Southern California.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

There's been no rainfall recorded at Downtown Los Angeles (USC) since December 17 when 0.01 inch recorded. Los Angeles ended December with 1.01 inch of rain. This is less than half of normal for the month and far less than last December's deluge of 10.23 inches.

Even though December 2011 was somewhat dry, it comes nowhere near setting a record. Since 1877 there have been eight Decembers in which no rain was recorded, and 44 Decembers with 1.01 inches of rain or less.

Downtown begins 2012 with a water year rainfall total of 3.76 inches. Last year we would have said this was near normal, but using the new normals derived from 1981-2010 data the total is 0.56 inch below normal. It has been several years since Downtown Los Angeles (USC) recorded below normal rainfall for the first six months of the water year. The last time was July 1 to December 31, 2007.

In a word the weather for the Rose Parade is expected to be SPECTACULAR. The current NWS point forecast for Pasadena is calling for an overnight low Sunday-Monday of 54 and a high Monday of 83. Click here for the latest NWS forecast for Pasadena.

The MJO has been relatively active this autumn and after going on a two week holiday appeared to be more coherent as it moved into the Western Pacific between Christmas and New Year's. However the NCEP GEFS and several other models forecast the MJO to rapidly diminish in amplitude and eastward propagation.

At the moment the precipitation outlook continues to be on the dry side. We'll see!

The November 30 - December 1, 2011 downslope windstorm felled thousands of trees, produced multi-day power outages and resulted in millions of dollars of damage in valley communities along the San Gabriel Mountains. An initial analysis of the conditions leading up to the event suggest a combination of factors contributed to the strength of the winds. Among them were a highly amplified and energetic north-south upper flow which was evolving into a cutoff upper low over southeastern California; a deepening surface low south of Las Vegas; cold air advection; and a possible inversion near mountain-top level.

More information about Southern California weather and climate can be found using our WEATHER LINKS page.

For the past two years Los Angeles has recorded above normal rainfall over the first six months of the water year (Jul. 1 to Dec. 31). So far this year is following suit.

After a record-setting storm in early October in which Downtown Los Angeles (USC) recorded over an inch or rain, a series of upper level troughs have continued to bump up the rainfall total. The systems have tended to be amplifying upper level troughs that split, typically transforming the southern half of the trough into a difficult-to-forecast cut-off upper level low. The resulting cut-off lows have then tracked over, along, or off the Southern California coast producing varying amounts of rain.

Sunday's system was the fourth to produce measurable rain in Los Angeles this November. A strong cold front produced very heavy rain, resulting in flooded streets and highways and resulting in a host of other weather-related problems. In the middle of it all runners in the PCTR Santa Monica Mountains 9K, 18K, 30K and 50K were running distances up to 31.5 miles on the trails of Pt. Mugu State Park.

Downtown Los Angeles (USC) recorded 0.90 inches for the storm, bringing the water year total to 2.75 inches. This is 1.11 inch above the new 1981-2010 normal for rainfall from July 1 through November 22. Here are some additional (preliminary) precipitation totals from around the area, compiled by the NWS Los Angeles/Oxnard. More than an inch above normal sounds like a lot, but as of today only guarantees Los Angeles precipitation will be above normal through December 12.

Back on July 1 NOAA released the new 1981-2010 climate normals, replacing the 1971-2000 normals that have been used this past decade. Normals serve as a 30 year baseline average of climate variables such as monthly and annual maximum, minimum, and mean temperature; and monthly and annual total precipitation. For example, Downtown Los Angeles' new normal annual precipitation total is now 14.93 inches, down from the 15.14 inches we've been using.

After dropping to -0.503 for July/August, and then to -0.772 for August/September, the September/October value of the Multivariate ENSO Index (MEI) has dropped a bit more to -.968 sigma. This is well within La Nina territory, but almost one sigma less than last year's September/October value. Plots of the Global Wind Oscillation (GWO) for July 1 to November 19, 2011 and the same period last year illustrate the year-to-year difference in the atmosphere's response to La Nina conditions. So far, this year's response is consistent with a more active MJO and a shift toward a more neutral ENSO state.

While there's still a chance of rain in Southern California Thanksgiving Day, the forecast is looking better than it did a few days ago when rain was considered likely. The difficulty in the forecast is yet another upper level trough splitting into a cut-off upper level low. The 12z NAM forecasts the low to remain offshore on Thanksgiving Day, and move into Northern Baja by the late afternoon. The 09z SREF puts the probability of more than 0.01 inch of rain in coastal Southern California for the 12 hours ending 4:00 pm Thursday at 10% - 30% and the chance of more than 0.10 inch of rain at around 10%. A shift in the track of the low toward the coast would significantly increase the chance of rain. We'll see!

More information about Southern California weather and climate can be found using our WEATHER LINKS page.