# Thursday, July 9, 2020
« El Nino Comparison Chart for 2019-2020. | Main |
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.

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