El Niño 2015-2016: Distinguishing Normal Weather From El Niño-Driven Storm Patterns

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A spring storm brought rain to Commerce on Thursday, May 7, 2015. (Credit: Loudlabs)

The rainy season in Southern California extends from November until the end of April. The heaviest rains in Los Angeles occur in January, February, March and April. This will most likely be true during the current El Niño. We would normally see about 13 inches of precipitation during these months. With a strong El Niño we could see 35 inches of rain during the upcoming January, February, March and April.

Rainfall amounts 150 percent to 200 percent of normal are a good signal that our weather is being affected by El Niño. A normal storm might bring anywhere from 1 inch to 2 inches (L.A. Basin) of precipitation over a couple of days.

During El Niño years we might see a series of storms generating two or three times more rainfall. The development of a “Pineapple Connection” would also signify a weather pattern related to El Niño. The most obvious sign of extreme El Niño-driven weather will come in the physical damage it leaves behind.

The El Niño of 1982/83 was one of the most destructive weather years in modern times. Looking back provides a good example of what to expect in the Southland. Interpreting the numbers shows, except for December, all of the months recorded rainfall amounts higher than the mean. This may be a little misleading because a mean is an average of many years. You would generally find totals above or below the mean. However what separates this season from others is rainfall amounts that are two or three times the mean. This shows that the El Niño phenomenon did play a significant role in shaping this rainy season.

Another important note of this historical table is the relatively calm period we experienced in December and into the first half of January. The idea of El Niño tends to make people think of constant storms throughout the winter season. Calm periods will likely be mixed in this winter. They do not signify an end to the El Niño. Rather, they are a part of normal weather patterns.

Projecting what will happen in the coming months is aided by looking at 1982/83. However, this season we may see divergent weather patterns develop. Other factors like the Ridiculously Resilient Ridge of high pressure that has contributed to our lengthy drought and climate change could introduce new variables into the El Niño equation. For example, we could have the heaviest rains and flooding in the first part of January. Or we may see no unusual weather. The important message in all of this is to be prepared.

El Niño Flashback 1982 and 1983
Measurements Taken From UCLA in Westwood
Nov ’82 Dec ’82 Jan ’83 Feb ’83 Mar ’83 Apr ’83
4.83″ 1.61″ 8.99″ 6.40″ 9.52″ 4.26″
1.4″ 2.5″ 2.8″ 3.1″ 2.5″ 1.2″
Days With
7 5 7 12 16 12
Several tornadoes spawned on 11/9. Highest daily rainfall 2.35″ on 11/30 Below average rainfall. Highest daily rainfall 1.09″ on 12/22. Dry until 1/16. Three days of wet weather produced 4.56″ of rain around 1/22. Highest daily rainfall 2.60″ on 1/27. 2.31″ of rain fell in the first 8 days. Minor rains from 2/9 – 2/18. Prolonged wet period began on 2/24 extending into March. Nearly 4″ of rain fell in the last 4 days of the month. Highest daily rainfall 1.60″ on 2/26. On 3/1 a major tornado rips through central L.A. causing widespread damage. Highest daily rainfall 3.57″ also on 3/1. On 3/7 a 12-day period of wet weather came to an end. 9.28″ of precipitation fell from 2/24 until 3/7.
Rains resumed on 13th with 2.98″ falling from 3/21 – 3/24.
Highest daily rainfall .96″ on 4/30. Rains off and on from 4/17 – 4/30.
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