Update on February 2, 2017. Downtown Los Angeles has ended January 2017 with 8.38 inches of rain. This is 269% of the normal January rainfall total of 3.12 inches. The preliminary Rain Year precipitation total for Downtown Los Angeles for July 1 through January 31, 2017 is 14.33 inches, which is 193% of the normal amount of 7.44 inches. Here is an updated California Percent of Normal Precipitation map from the Western Regional Climate Center for July 1, 2016 to January 31, 2017.

On the heels of a wet December, a series of Pacific storms have resulted in the wettest start to the Rain Year (July 1 - June 30) and Water Year (October 1 to September 30) since the very wet year of 2004-2005.

The six day period from January 18-23 was particularly wet, with three storms producing a total of 5.53 inches of rain at Downtown Los Angeles (USC). Here are some preliminary 7-day precipitation totals from around the area from the Ventura County Watershed Protection District.

The last system of the series, which brought very heavy precipitation to the area on Sunday, was associated with a well-defined atmospheric river. Precipitation totals in the Los Angeles area for the storm generally ranged from about 2 to 5 inches. According to the NWS, new rainfall records for January 23 were set at Los Angeles Airport (2.94 inches), Camarillo (2.74 inches) and Long Beach Airport (3.97 inches). The rainfall at Long Beach Airport was the most ever recorded in a day at that location. Here are some precipitation totals from around the area compiled by the NWS Los Angeles/Oxnard and NWS San Diego.

As of yesterday Downtown Los Angeles (USC) has recorded 14.33 inches of rain for the Rain Year. This is 217% of the normal amount of 6.65 inches for the date, and 97% of the normal amount of rainfall for an entire year. Assuming we don't get any more rain this January, the 8.38 inches recorded will work out to 269% of the normal amount for the month.

The California Cooperative Snow Surveys Snow Water Equivalents report for today puts the snowpack for the date at an average 197% of normal. That's two times the normal amount.

A little precipitation has crept back into the GFS, GEFS and ECMWF forecasts for the Los Angeles area the first week of February. We'll see!

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

After being negative for 3 1/2 years, the PDO Index has been positive since January 2014. December's PDO value of 2.51 is the highest for that month on record (since 1900), exceeding December 2002's value of 2.10 and December 1940's value of 1.96.

Even so, the highly anticipated 2014-15 El Nino continues to dawdle with little ocean-atmosphere coupling and an emphasis on an higher amplitude meridional flows. Due in part to the upwelling phase of a series of oceanic Kelvin waves, equatorial Pacific heat content and SST anomalies have diminished. After having been at or above 0.5 °C for the past twelve weeks OISST.v2 Nino 3.4 SST Anomalies dropped to 0.4 °C for the week centered on January 7, 2015 and as of the week of January 14 was at 0.5 °C.

The Multivariate ENSO Index (MEI) for NOV/DEC has decreased 0.13 SD to +0.58, but has maintained its historic rank (since 1950) at 47. A rank of 46 is the threshold for weak El Nino conditions in the context of the MEI. The FNL Global Wind Oscillation for the past 90 days continues to reflect the lack of definitive atmospheric coupling.

So far this rain season Northern California and the coastal areas of Central and Southern California have fared much better in terms of precipitation than last year. As of today Downtown Los Angeles (USC) precipitation for the water year (beginning July 1) is at 90% of normal and Downtown San Francisco is at 127%.

As this AHPS plot of precipitation since October 1 shows, many areas of California have recorded at least 75% of normal precipitation. Unfortunately the Sierra Nevada is not one of them. While better than last year's dismal 14% of normal on this date, this year's snowpack is currently well below average, and was last reported at 36%. Here is an AHPS plot of precipitation departure since October 1 that shows the deficits in the Sierra Nevada.

At the moment it doesn't look like the snowpack will get much help in the short term. After fending off a little shortwave the blocking ridge is forecast to rebuild to new heights, bringing unseasonably mild weather to much of the West Coast. There does appear to be the possibility of a wildcard low latitude low developing under the block and that could result in some precipitation in Southern California next week. If such a system develops, given the warm state of the Eastern Pacific, it could be wetter than expected. We'll see!

In the early morning hours of Friday, December 12, 2014, a very strong cold front, enhanced with moisture from an atmospheric river, produced a line of strong storms that produced rain rates in the Springs Fire burn area as high as 2 inches per hour. This resulted in widespread flash floods and debris flows in the burn area, much of which is in Pt. Mugu State Park. Mud and debris flows originating from the burn area inundated homes below Conejo Mountain and closed Pacific Coast Highway. This slideshow includes photos of the aftermath of the flash floods and debris flows in Blue Canyon, Sycamore Canyon and Upper Sycamore. The photos were taken on a trail run on December 14, 2014. Also included are some NWS Los Angeles/Oxnard tweets and some additional meteorological images and info.

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

Updated November 5, 2013. My mistake -- a spreadsheet range error -- thanks for the heads up Reg! The driest January 1 to November 1 for Downtown Los Angeles was in 1972 with 0.92 inch. Here are the driest ten years for that period:

1. 1972 0.92
2. 2002 1.62
3. 1984 1.93
4. 1961 2.37
5. 1971 2.39
6. 1947 2.45
7. 2013 2.78
8. 1894 2.89
9. 1953 2.89
10. 2007 3.37

An energetic upper level low brought the first widespread precipitation of the rain season to Southern California October 9, with rain at the lower elevations and some snow in the local mountains. Rainfall amounts varied widely, ranging from a trace in some areas to over an inch in the mountains.

Downtown Los Angeles (USC) recorded only 0.04 inch for the storm, bringing the water year rainfall total to 0.13 inch, which is 0.31 inch below normal. Downtown Los Angeles has recorded only 2.76 inches of rain since January 1. This is one of the driest January 1 - October 20 in Los Angeles over the past 135 years! To get out of the bottom ten for calendar year rainfall Los Angeles needs about 3.5 inches of rain by December 31. Normal rainfall for November is 1.04 inches and for December is 2.33 inches.

For months I've been monitoring climate data and forecasts looking for something on which to base a 2013-14 Winter precipitation Outlook. Historically ENSO has played the major role in Southern California rain season weather, with El Nino conditions generally producing wetter weather and La Nina conditions generally drier. But ENSO conditions are currently Neutral and are expected to remain so through the end of the year.

Most climate models forecast slow warming of SSTs in the equatorial Pacific (NINO 3.4 region) over the next several months, but at this time of the year it would be very unusual to have substantial warming. The CPC/IRI ENSO Forecasts from IRI's October Quick Look indicate the probability of an El Nino developing before the end of the year is less than 20% -- and 20% seems high.

One computer model that at times has been forecasting above average precipitation in Southern California this Winter is the Climate Forecast System version 2 (CFSv2). The CFSv2 is fully coupled ocean-atmosphere-land-sea ice model used to forecast parameters such as sea surface temperature, temperature and precipitation rate. While skillful at predicting tropical SSTs, the CFSv2 generally performs very poorly when forecasting precipitation over land, so forecasts such as this earlier one for Dec-Jan-Feb must be viewed somewhat skeptically.

Another glass half-full observation is that the Madden-Julian Oscillation (MJO) has been relatively active this year and if this activity continues it provides recurring opportunities for enhanced U.S. West Coast precipitation. The downside is that it can result in periods of dry weather as well.

With the ocean and atmosphere neutral there's just not much on which to base a rain season forecast. As a result of the government shutdown the release of the official NOAA 2013-14 Winter Outlook has been delayed until November. The October CPC outlook is usually the basis of the initial official NOAA U.S. Winter Outlook. The U.S. Dec-Jan-Feb Precipitation Outlook, released October 17, calls for an equal chance of below average, average, or above average precipitation for all of California. We'll see!

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

After producing phenomenal rainfall totals in Southern California and snowfall totals in the higher elevations of the Sierra, the Pacific low and trough responsible for days and days of wet weather has finally moved east.

Some stations recorded more rain in the last 7 days that would normally be recorded over an entire year. Precipitation amounts over 10 inches were common, and several stations recorded over 20 inches. Tanbark, in the San Gabriel Mountains recorded 24.7 inches, NF Matilija in the Ventura Mountains recorded 24.09 inches, and Lytle Creek in the San Bernardino Mountains recorded an astonishing 26.35 inches!

Here's are snapshots of provisional 7-day rainfall totals in Ventura County and 7-day rainfall totals in Los Angeles County from the Ventura County Watershed Protection District ALERT Map Viewer; and a snapshot of provisional 7-day rainfall totals from the NWS San Diego's Experimental Rainfall Summary Display. And here are archived copies of NWS precipitation summaries with preliminary rainfall totals from the NWS Los Angeles/Oxnard and NWS San Diego offices.

The remarkable amount of rainfall makes December 2010 one of the wettest on record in Southern California. According to preliminary NWS data Downtown Los Angeles (USC) has recorded 8.52 inches of rain so far this December. This ranks it as the third wettest December in Los Angeles since recordkeeping began in 1877, exceeded only by December 1889 (15.8 inches) and December 2004 (8.77 inches). With additional rain a possibility, December 2010 only needs 0.25 inch to surpass 2004. For more detailed info see "A Look at the Record-Breaking Week of Rainfall" a PDF from the NWS Los Angeles/Oxnard.

The Sierra recorded gargantuan snowfall totals, with some of the largest being in the Southern Sierra. In the last week the snow sensor at Farewell Gap recorded 22.6 inches snow water equivalent, which roughly translates to 18 feet of snow. This morning California Cooperative Snow Surveys reports the Southern Section Sierra snowpack at 287% of normal, and the snowpack overall in the Sierra at 207%! Mammoth Mountain reports 167 inches of snow so far this December, a new record for the period 1968 to date, obliterating the records set in 1971 (139.8 inches) and 2002 (134.4 inches).

As of yesterday Downtown Los Angeles (USC) rainfall was a whopping 6.88 inches above normal for the water year. That puts us way, way ahead of what is typical for a La Nina influenced rain season -- at least for a couple of months.

Update December 24, 2010. Looks like there will be two opportunities before the end of December for Downtown Los Angeles (USC) to increase its rainfall total for the month and become the second wettest December since recordkeeping began in 1877. The first chance is Saturday night. For the 24 hour period ending 10:00 a.m. Sunday, the 09z SREF puts the probability of more than 0.25 inch of precipitation in the Los Angeles area at about 70%. The WRF ensembles precipitation forecast for LAX for Saturday night ranges from a low of about 0.25 inch to a high of about 0.7 inch. The 18z GFS says the second opportunity will be Wednesday, and forecasts a little under an inch of rain at LAX. We'll see!

More information concerning Southern California weather can be found using our WEATHER LINKS page.

If current precipitation forecasts and outlooks validate, December 2010 could become one of the wettest on record in California, and at the higher elevations of the Sierra, one of the most snowy. This morning's 5-day precipitation forecast from the Hydrometeorological Prediction Center, for the 5-day period ending early Wednesday morning, indicates up to 7.9 inches of precipitation locally, and 14.7 inches (water equivalent) in the Sierra. And additional precipitation is forecast beyond the 5 day period.

A large Pacific low working in concert with a low west of Hawaii has established a tropical connection, and is pumping copious amounts of moisture into California. This tropical moisture conveyor belt scenario is currently forecast to continue into next week. Late Sunday, shortwave impulses dig down into the low and elongate it southwestward, creating a large longwave trough. This northern part of this trough is forecast to evolve into another large upper and surface low in the northeastern Pacific. The southern part of the trough is forecast to develop a surface low and front that moves into Southern California Tuesday into Wednesday.

In the short term, BUFKIT analysis of WRF ensemble data for Van Nuys shows precipitation totals through early Sunday morning ranging from about 1.0 inch up to about 3.5 inches. Analysis of 12z NAM data for Van Nuys produces around 1.8 inches through early Sunday morning and nearly 5 inches through early Monday morning. The 09z SREF pegs the probability of more than 1.0 inch of precipitation in Los Angeles area at around 70%. Precipitable water values of over 1.0 inch, high relative humidity, and a strong south to southwesterly inflow of over 30 knots should produce significantly enhanced precipitation on favored slopes -- generally those with a south to southwest aspect.

It's a little early to put much credence in forecasts for next week, other than more rain appears likely. The 06z GFS produced astronomic precipitation totals mid-week -- several inches more than either yesterday afternoon's 00z run (2.75 inches), or this morning's 12z run (4.6 inches). We'll see!

As of yesterday Downtown Los Angeles (USC) rainfall was 0.91 inch below normal for the water year, and much of Southern California was falling behind in the rainfall department. It looks like by next week we'll be ahead of the La Nina game again, perhaps way ahead.

More information concerning Southern California weather can be found using our WEATHER LINKS page.