Downtown Los Angeles (USC) ended the 2020-21 rain year (July 1 to June 30) with 5.82 inches of rain. This is about 41% of the new normal annual precipitation total of 14.25 inches. Much of the West recorded below average precipitation for the rain year.

The amount of rainfall that is considered "normal" for Downtown Los Angeles has decreased nearly an inch in the past three decades. The normal rainfall for Los Angeles was 15.14 inches based on 1971-2000 climate data, and dropped to 14.93 inches based on data from1981-2010. Analysis of 1991-2020 data provided the new normal of 14.25 inches. Interim 2006-2020 climate data is shockingly dry, with normal rainfall in Los Angeles calculated at only 11.39 inches! For more info see U.S. Climate Normals and Normals Calculation Methodology 2020 (PDF).

La Nina conditions developed in August 2020 and transitioned to ENSO-neutral in April 2021. The Oceanic Nino Index (ONI) decreased to a minimum of -1.3 in the Oct-Nov-Dec season. The EL NIÑO/SOUTHERN OSCILLATION (ENSO) DIAGNOSTIC DISCUSSION issued August 12, 2021 projects a 70% chance of La Nina conditions being present during November-January.

Los Angeles rainfall during La Ninas has been variable, but skewed to the drier side. The average rain year precipitation for the 24 ERSST.v5 ONI-based Cold Episodes since 1949 is 11.84 inches. The highest amount was 20.20 inches in 2010-11 and the lowest 4.68 inches in 2017-18. In the past decade, rainfall totals for Los Angeles have been less in the second year of successive cold episodes, but this pattern doesn't hold up over the entire record.

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

Downtown Los Angeles (USC) November 2019-April 2020 Rain
Month	Precip in.	Normal in.	Percent of Normal	500mb Height Anomaly
November	2.12	1.04	204%
December	4.84	2.33	208%
January	0.32	3.12	10%
February	0.04	3.80	1%
March	4.35	2.43	179%
April	3.02	0.91	332%
Rain Year	14.86	14.93	99.5%

To say Los Angeles recorded a normal amount of rainfall during a rain year is not the same as saying the rain year was typical. As I scan down the monthly precipitation totals in Los Angeles' 143 year weather record, it seems the pattern of rainfall is different for every one.

Our most recent rain year, 2019-2020, is an excellent example. Wet weather in November and December was followed by equally dry weather in January and February. Just when it looked like the rain season was done, wet weather returned in March and April. The end product was a "normal" rain year, with 14.86 inches of precipitation recorded at Downtown Los Angeles (USC) from July 1, 2019 to June 30, 2020..

As can be seen from the mean monthly 500mb height anomalies, much of this rain season's precipitation resulted from a semi-persistent pattern of upper-level low pressure off the coast of Southern California. The pattern of precipitation in the West for the rain year reflects the position of these lows.

Based on the CPC's Oceanic Nino Index (ONI), equatorial Pacific SSTs marginally capable of supporting El Nino conditions developed in the Oct-Nov-Dec 2019 season, but ocean-atmosphere coupling characteristic of El Nino did not follow.

There is some evidence that suggests Southern California precipitation is more closely correlated with AAM than with Nino 3.4 SST. Here is an extended GWO phase space plot for November 2019 - May 2020. The November-March GWO Phase Plots for ONI-based warm episodes can be found on our El Nino Comparison Chart for 2019-2020 page.

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The graphic above is color-coded chart of Los Angeles (KCQT) rain year precipitation from 1877 to 2017, a period of 141 years. Years progress from left to right. The rain year is from July 1 of the indicated year to June 30 of the following year. Colors are indicative of the following amounts of rain:

Red: VERY DRY - less than 5 inches of rain.
Orange: DRY - more than 5 inches of rain, but less than 13 inches.
Light blue: ABOUT AVERAGE - more than 13 inches of rain, but less than 17 inches.
Blue: WET - more than 17 inches of rain, but less than 22 inches.
Dark Blue: VERY WET - more than 22 inches of rain.

Following are some observations regarding Los Angeles rainfall:

- VERY DRY and DRY years (orange & red) have been more common than VERY WET and WET years (blue & dark blue). In the first 70 years there were a few more dry years than wet years (30 vs. 25). In the last 70 years there have been about twice as many dry years as wet years (41 vs 20).

- Extended dry periods (orange & red) have been more common than extended wet periods (blue & dark blue) and generally last longer. The longest uninterrupted dry period is 7 years, while the longest wet period is only 3 years. If we allow for one interceding year, the longest dry period is 11 years and the longest wet period is 5 years.

- There were no VERY DRY years (red) prior to 1960 and three of the four VERY DRY years have occurred since 2001.

- ABOUT AVERAGE years (light blue) have not been common. Only 24 of 141 years (17%) have had ABOUT AVERAGE rainfall. The first 70 years had 15 ABOUT AVERAGE years and the last 70 years had 9 ABOUT AVERAGE years.

- Overall, VERY WET years (dark blue) have been more common than VERY DRY years (red), but in the last 30 years the number of VERY WET years (4) and VERY DRY years (3) have been about equal.

- Consecutive VERY WET (dark blue) or VERY DRY years (red) have been rare. There has been one instance of back-to-back VERY WET years (1956 & 1957) and no instances of back-to-back VERY DRY years.

Here is a PDF of the rainfall chart. The chart includes the January - December precipitation amounts for each year, as well as the rain year value.

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

Downtown Los Angeles (USC) finished the 2016-17 rainfall year (July 1 to June 30) with 19.00 inches of recorded precipitation. This is about 127% of the 1981-2010 normal of 14.93 inches. This was the first rain year with above normal precipitation at Los Angeles since 2009-2010, when 20.2 inches was recorded.

As of May 2017 the Pacific Decadal Oscillation Index has been positive (warm) since January 2014 -- a record 41 consecutive months. The previous record streak was 36 months, from August 1991 to July 1994.

Most climate outlooks are projecting ENSO Neutral conditions are favored to persist into the Northern Hemisphere fall, with a lesser chance of weak El Nino conditions developing over that period. Perhaps supporting the notion of El Nino development, the April-May value of the Multivariate ENSO Index (MEI) increased by 0.69 standard deviations from 0.77 to 1.46. This is solidly within the index's El Nino ranking and at the threshold of a strong El Niño ranking. According to Klaus Wolter, the increase over the last three months is the second largest on record for this time of year, exceeded only by 1997. We'll see if ENSO conditions remain neutral or some form of ENSO warming (Central Pacific?) takes place.

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

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.

As of today Downtown Los Angeles (USC) December rainfall is 1.75 inches above the monthly normal of 2.33 inches. Not since the beginning of the drought has Los Angeles experienced such a wet December. The 4.08 inches of rain recorded so far this month is the most since December 2010 and the most for any month since January 2010.

Since the Rain Year began July 1, 5.48 inches of rain has fallen at Downtown Los Angeles (USC). This is more than an inch above the normal July-December rainfall of 4.32 inches. It is the best start to the Rain Year (Jul 1-Jun 30) and Water Year (Oct 1-Sep 30) since 2010.

While the rain is good news, this graphic from the Western Regional Climate Center shows that the Jul-Dec precipitation in some areas of Southern California is still below normal.

Forecasting how the cut off upper level low currently spinning offshore southwest of Los Angeles and a developing upstream trough interact is a tough task, even for a supercomputer. The trough is expected to propel the low in our general direction and then replace/absorb it. Add to the mix the possibility of pulling up some sub-tropical moisture (or not) and the forecast becomes even trickier. Guess we'll see!

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

Downtown Los Angeles (USC) finished the 2015-16 rainfall year (July 1 to June 30) with 9.65 inches of recorded precipitation. This is about 65% of the 1981-2010 normal of 14.93 inches. This was the fifth consecutive year of below normal rainfall for Downtown Los Angeles, with a cumulative rainfall deficit of 35.86 inches --nearly three feet!

Observable impacts of the drought are widespread. Trees have been particularly hard hit. Dead trees can be seen along city streets, in parks, and throughout the open space areas and wildlands of Southern California. The dead and dying 100+ year old coast redwoods at Malibu Creek State Park are an example.

Most climate outlooks are forecasting La Nina conditions to develop over the Northern Hemisphere summer. Historically La Ninas have "on average" resulted in below normal precipitation in Southern California. But historical composites can be misleading. During the last five La Nina episodes (1999-00, 2000-01, 2007-08, 2010-11, 2011-12) Downtown Los Angeles (USC) has averaged 14.39 inches of rain, which is 96% of normal.

Even during one of three strongest El Ninos on record, precipitation outlooks based on historical composites and analogs didn't perform well in Southern California. Given the somewhat more variable rainfall in Southern California during La Ninas, to determine the winter precipitation outlook you might as well flip a three-sided coin.

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

Following a circuit through Arizona, Mexico and the Eastern Pacific that started in Southern California on October 5, a moisture-laden upper low moved into SoCal for a second time Thursday, October 15.

On the second go-round the upper low packed an even bigger punch, producing strong afternoon thunderstorms with very high rain rates that resulted in severe flash flooding and debris flows in northern Los Angeles County and southern Kern County.

CIMSS Morphed Integrated Microwave Total Precipitable Water Imagery from October 12 shows the upper low entraining moisture from the sub-tropics and tropics as it retrograded into the Eastern Pacific.

Below are some NEXRAD Level-III/Google Earth composites of northern Los Angeles County and southern Kern County for the afternoon of October 15:

Overview

- PPS Storm Total Precipitation for the period ending 6:00 pm PDT. (KSOX)
- QPE Storm Total Precipitation for the period ending 6:00 pm PDT. (KSOX)
- PPS Storm Total Precipitation for the period ending 6:00 pm PDT. (KEYX)
- QPE Storm Total Precipitation for the period ending 6:00 pm PDT. (KEYX)

Lake Hughes - Elizabeth Lake Area

- One Hour Precipitation ending 3:30 pm PDT. (KSOX)
- Instantaneous Precipitation Rate at 3:20 pm PDT. (KSOX)
- Instantaneous Precipitation Rate at 3:30 pm PDT. (KSOX)

Leona Valley

- One Hour Precipitation ending 4:42 pm PDT. (KSOX)
- Instantaneous Precipitation Rate at 4:25 pm PDT. (KSOX)

Hwy 58 - Cameron

- One Hour Precipitation ending 5:39 pm PDT. (KEYX)
- Instantaneous Precipitation Rate at 5:21 pm PDT. (KEYX)
- Instantaneous Precipitation Rate at 5:30 pm PDT. (KEYX)

Here are NWS tabulations of some rainfall totals around the area for October 15 and some totals for October 16.

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

Recall that storm a week ago Monday that blasted down the West Coast and into the Southland? The Los Angeles County mountains received as much as two inches of rain; Downtown Los Angeles (USC) recorded 0.45 inch of rain; and the Sierra got a good shot of snow. (Here are some precipitation totals for that storm from the NWS Los Angeles/Oxnard and the NWS San Diego.)

Well, surprise, surprise that upper low isn't done with us yet! After a multi-day circuit into Arizona, Mexico and the Eastern Pacific, the low is now sitting off the coast of Southern California and forecast to move over the area on Thursday. The result is a chance of showers and thunderstorms today, Thursday and possibly Friday, particularly in the mountains. We'll see!

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

Downtown Los Angeles (USC) ended the 2014-2015 rainfall year (July 1 - June 30) with 8.52 inches of rain; well below the normal of 14.93 inches. It was the fourth consecutive year of below normal rainfall in Los Angeles and much of Southern California.

To kick off the new new rainfall year two waves of moisture and instability associated with ex-hurricane Dolores, other tropical sources, and a strong monsoonal flow from Baja resulted in record-setting rainfall in Southern California from Saturday July 18 to Monday July 20.

Constructive interference of the El Nino base state by the active phase of the MJO resulted in negative 200-hPa velocity potential anomalies and enhanced convection in the Eastern Pacific during the first half of July. This appears to have contributed to the rapid development of Dolores from a tropical depression on July 11 into a Category 4 hurricane July 15. Anomalously warm SSTs in the tropical and sub-tropical Eastern Pacific also played a role, helping to maintain the strength of Dolores and increasing the amount of water vapor entrained by the system and transported into Southern California.

Many stations set new records, not only for the date, but for any day in July. Downtown Los Angeles (USC) set rainfall records for the date on Saturday and Sunday and tied Monday's record. Downtown Los Angeles recorded 0.36 inch of rain Saturday. This is more rain than any day in any July since recordkeeping began in 1877. That one day of rainfall even broke the monthly record for July in Los Angeles! Prior to this event the wettest July on record was in 1886, when 0.24 inch was recorded.

There was very heavy rain in the mountains on Sunday, with rain rates exceeding an inch a hour. From 5:15 p.m. to 5:25 p.m. a CBS Radio weather station on Mt. Wilson recorded a half-inch of rain in just 10 minutes!

Though the rain created its own problems -- including flash floods, debris flows and rock slides -- the soaking rains helped quell the Pines Fire near Wrightwood and the North Fire near Cajon Pass. Over the three day period from Saturday to Monday the Big Pines Remote Automated Weather Station (RAWS), near the Pines Fire, recorded 3.12 inches of rain. Several stations in the San Gabriels recorded more than three inches of rain, including Clear Creek and Opids Camp. Here's a NWS compilation of some rainfall totals in the Los Angeles forecast area and the San Diego forecast area.

After dawdling around for several months our on again, off again El Nino is finally firing on all cyclinders and could reach ONI and MEI levels not seen since 1997-98 and 1982-83. The Multivariate ENSO Index (MEI) for May-June was 2.06. This was the third highest value for the season, exceeded only in 1983 (2.2) and 1997 (2.3). It is the second highest for the season during the development phase of an El Nino event. The 2015 April-May-June Oceanic Nino Index (ONI) value of 0.9 was higher than than in 1982 (0.6) and 1997 (0.6). Several dynamical models in the IRI/CPC ENSO Predictions Plume of forecast Nino 3.4 SST anomaly, released July 16, project Nino 3.4 SST anomalies in excess of 2.5°C this fall.

Analysis of correlations of CMAP Precipitation with globally integrated atmospheric angular momentum using ESRL/PSD's Linear Correlations in Atmospheric Seasonal/Monthly Averages tool suggests that precipitation in the southern half of California is more strongly correlated with atmospheric angular momentum (AAM) than with Nino 3.4 SST. For example, compare the correlation of CMAP Precipitation to AAM and to Nino 3.4 SST for Dec-Jan-Feb 1980-2012. Cyclical increases in relative atmospheric angular momentum are often associated with El Ninos. This can be seen in the plots of the Global Wind Oscillation in my El Nino Comparison Chart.

After being negative for 3 1/2 years, the PDO Index has been positive since January 2014. December's PDO value of 2.51 was the highest for that month on record since 1900. June's value of 1.54 was the 13th highest since 1900.

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.

After being negative for 3 1/2 years, the PDO Index has been positive since January 2014. October's PDO value of 1.49 is the 6th highest for that month since 1900 and comparable to PDO Index values in October 1997, 1957, 1993, and 1987.

PDO/AMO-based Precipitation composites suggest a warm Pacific generally produces more Winter precipitation in California than a cold Pacific. This makes sense. Among other effects a warm Pacific increases evaporation, air temperature, and the amount of water vapor transferred to the atmosphere. This in turn can increase precipitation. Here is a comparison of Pacific SST anomalies at the beginning of December 2014 and December 2013. Mouse over the image to switch to the December 1, 2013 image.

A warm Pacific may have contributed to the amount of precipitation produced in California by a large Pacific upper level low this past week. Two periods of rain were observed in Southern California -- one on Sunday and the other on Tuesday and Wednesday.

Sunday an embedded short wave in the moist southerly flow produced more rain than expected in many areas of Los Angeles. Surprisingly high rain rates and amounts in the Santa Monica Mountains, resulted in debris flows in the Springs Fire burn area that closed PCH. Here's a NWS compilation of some rainfall totals in the forecast area.

Even with the parent low lifting to the north on Tuesday and the 570 mb contour near Santa Barbara, the very moist southerly flow orographic lift and sufficient dynamics produced widespread precipitation in Southern California with some impressive precipitation totals. Tuesday record rainfall for the date occurred at both Downtown Los Angeles and Downtown San Francisco. Yucaipa Ridge in the San Bernardino Mountains recorded a whopping three-day rainfall total of 14.6 inches. Following are three-day rainfall compilations from the NWS Los Angeles/Oxnard and NWS San Diego.

Here are graphics from the CNRFC with gridded precipitation totals for the four day period from early Sunday morning to early Thursday morning for Southern California, the Sierra Nevada and the San Francisco Bay Area. Some preliminary precipitation totals of 5 inches or more are noted.

Equatorial Pacific SSTs continue to rebound with OISST.v2 Nino 3.4 SST Anomalies above 0.5 °C for the past seven weeks and now stand at 1.0 °C for the week centered on November 26, 2014. The Multivariate ENSO Index (MEI) for OCT/NOV has increased 0.35 SD to 0.71, increasing its historic rank (since 1950) from 42 to 47, just within the MEI's weak El Nino threshold. However as noted by the CPC in their December 4, 2014 ENSO Diagnostic Discussion, "the overall atmospheric circulation has yet to show a clear coupling to the anomalously warm waters." The FNL Global Wind Oscillation for the past 90 days continues to reflect the lack of definitive atmospheric coupling

For now the Pacific storm door appears to be open. Most medium-range guidance is suggesting another significant system will be affecting California in the Thursday-Friday timeframe. We'll see!

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