By Charly SHELTON
“Great droughts, I always say, end in great floods.” So says Bill Patzert, climatologist with JPL who sees the coming storm. Not in a figurative sense, but literally – there will be a lot of storms this winter in the Los Angeles area courtesy of the coming El Niño.
“Everybody has forgotten what [winter is] like, not only a normal winter but one with twice the average rainfall and snowpack,” said Patzert. “In February 1998 [last time a major El Niño hit L.A.], rather than three inches of rain that month, which would be normal, we had almost 14 inches of rain.”
Over the course of a month, L.A. was hit with four large storms and two small ones that dumped almost an entire year’s worth of expected rainfall. These caused flooding, hazardous conditions and more flooding.
“When it comes at you that fast and furious,” said Patzert, “we are just not engineered to handle it gracefully. Angelenos can’t drive when we get a quarter inch of rain. When we get 14 inches in a month, we are talking mudslides, general chaos all over California.”
This extreme weather is caused by the heating of ocean water around the equator, which simultaneously creates a high-pressure system that changes the path of the jet stream (the flow of winds that direct storms) and pumps more evaporated water into the atmosphere, condensing as huge storm clouds. It both creates and drives huge storms to our area.
“They say [an El Niño] has a cycle, every three to seven years,” said Stuart Seto of the National Weather Service, “but actually it was going on last year; [it just wasn’t expected] to get as strong. And this year, one of the things that affect it is the way it is measured. It has to be over a certain degree of heating on the equator, near the date line. They call this, where it is actually measured for our area, a 3.4 region out by the equator. And what are looked for are temperatures to go above normal. Once it reaches 0.5 C above normal, then it is considered El Niño temperature. If that persists over a three month period, then an advisory is issued, which was done earlier this year in January.”
Temperatures rose through the beginning of the year and by June, Seto said, the temperature was up to 0.9 C above normal. In July, it was just over 1 C above normal. Following the pattern, the National Weather Service expects the temperature to rise above 2.0 between December and March, the official winter months.
The NWS classification system for El Niño rates the severity based on the temperature increase. From 0.5 to 0.9 C above normal is considered a weak El Niño. From 1.0 to 1.4 C above normal is a moderate El Niño, and 1.5 C and above is considered a strong El Niño. With an expectation of 2.0 or above, this El Niño year could bring quite a bit of rain, which California is sorely in need of during its severe drought.
“The best thing we can do now is to make plans to capture more of the water that we get during our rain years and to continue to conserve,” said Seto.
While the El Niño rains will help, even with a huge storm year as in 1998, it won’t end the drought. It would take several consecutive years of such rainfall, Seto said, to bring the water table, reservoirs and lakes back to the normal, safe level. For the past four years, California has received about half its normal rainfall and so even doubling or tripling the amount of rain cannot make up the deficit in just one winter.
That being said, many are hoping for as much rain as they can get.
“That’s the great wet hope, you know,” said Patzert. “But the flip side of that is be careful what you wish for.”
Resulting from the Station Fire and subsequent floods, foothill debris basins and flood control channels have not been fully cleared and this could cause an issue, Patzert said. The direct effects of the Station Fire of 2009 are behind us as the Arroyos have healed for the most part. Any upcoming flooding that might occur will not be as violent as those first rains in February 2010, but whatever does wash down the mountain currently has nowhere to go. This poses a danger for those who live on a hillside or in the foothills. Sandbags or other water flow diversion agents and proper emergency kits are vital to ensure the safety of the home and family.
“Mitigation and preparedness are the key when you have unusual copious amounts of rain and snowpack,” said Patzert. “So sitting around and wringing your hands doesn’t help much, but getting prepared goes a long way to mitigating any kind of disaster or damage you might have.”
For more information on El Niño and how to get prepared for the coming wet winter, visit elnino.noaa.gov.